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Tensile and shear performance of rotary inter-module connection for modular steel buildings
Abstract
Because of the advantages of construction speed and efficiency, modular steel buildings (MSBs) have been increasingly used in mid-to high-rise buildings with repetitive units. Different form of connection and mechanical performance of the inter-module connection of MSBs from the traditional structure have always been remained a research hotspot. In this study, the mechanical performance of an innovative rotary inter-module connection was studied mainly through two tensile and two shear resistance tests. Then, the parametric analysis was carried out through the finite element analysis. The critical components of the connection under the tensile load were the corner fitting and the bottom plate of the lower rotating part, whereas, during the shear performance, the top plate of the lower corner fitting played a vital role. The edge yield of the bottom plate of the lower rotating part was used as the basis for deriving the formula of the tensile bearing capacity of the connection. Finally, a simplified calculation model was developed, and the formulas for tensile and shear bearing capacities were derived and verified.
... Researchers have proposed various IMCs, including welded [16,17], self-locking [18], rotary [1,19], prestressed [20], bolted [10,[20][21][22][23][24][25][26][27][28], and hybrid IMCs [29]. For bolted and rotary IMCs, openings (also referred to as access holes) are typically created in the side plates of corner fittings to provide the necessary space for assembly [1,17,[21][22][23][24][25]29]. ...
... Numerous studies on IMCs with openings in corner fittings or modular columns have been conducted, as shown in Fig. 3. Chen et al. [1,19] introduced a type of rotary IMC (see Fig. 3a) featuring elliptical openings on the side plates of corner fittings. They investigated the tensile, shear, and flexural properties, as well as the seismic performance of these IMCs through experimental studies and finite element (FE) analyses. ...
... Shi et al. [10,22] investigated a bolted IMC with corner fitting openings (see Fig. 3d). Through experiments and FE analysis, they examined the me- [1,19], b) Lacey's post-tensioned bolted IMC [20], c) Choi's bolted IMC [21] and d) Shi 's bolted IMC [10,22]. chanical behavior of typical IMCs under axial tension and compression loads, developing a theoretical model to predict the axial loaddisplacement relationship. ...
... Thus, the self-locking connection may be a key direction for future research on the vertical connection of modular steel buildings. [20,23] Overall, although there is an insistent demand for a deeper understanding of the mechanical performance of module-to-module vertical connections, the related research is still limited. The development of connections between modules is even more challenging, for the following reasons: (1) Easy manufacture and hoisting: inter-module connections should meet the requirements of building industrialization. ...
... The research results show that rib stiffeners can significantly improve the bending stiffness and lateral bearing capacity of the joint connection. The stress concentration in the joint connection area can be effectively reduced by adding rib stiffeners in the area of the 9 Chen et al. [20,23] 1. cyclic loading 2. Shear behavior 7 Chen et al. [31] 1. static loading 2. Moment transfer behavior 8 Lacey et al. [28] 1. monotonic loading 2. Shear behavior 9 Chen et al. [20,23] 1. monotonic loading 2. Tensile and shear behavior ...
... The research results show that rib stiffeners can significantly improve the bending stiffness and lateral bearing capacity of the joint connection. The stress concentration in the joint connection area can be effectively reduced by adding rib stiffeners in the area of the 9 Chen et al. [20,23] 1. cyclic loading 2. Shear behavior 7 Chen et al. [31] 1. static loading 2. Moment transfer behavior 8 Lacey et al. [28] 1. monotonic loading 2. Shear behavior 9 Chen et al. [20,23] 1. monotonic loading 2. Tensile and shear behavior ...
Modular steel buildings offer the advantages of time-saving construction, reduced on-site work, and less resource waste. The mechanical behavior of modular connections is complex, depending on the type of connecting method and the load-transferring path. The aim of this paper is to offer an overview of the methods for creating inter-module connections. First, we discuss the existing inter-module connections, including vertical connections, horizontal connections, and module-to-concrete-core-wall connections. Then, the mechanical performance and simplified models of the inter-module connections are reviewed in detail; these have a significant influence on the development of modular steel buildings. Finally, the prospects of module-to-module connection are summarized. Despite the increasing amount of research that explores module-to-module connections, fully modular buildings have not yet been achieved, hindering the further development and use of modular steel buildings. In this context, self-locking connections and laminated double-beam connections are proposed, with the aim of promoting the increased use of modular steel buildings.
... Doh et al. [59] discovered that bolted bracket connections were susceptible to prying failure, exhibiting a brittle behavior and are suited for low-rise structures. Thus, Chen et al. [60,61] developed rotary connectors that protect the columns; access holes are used for large bolt tightening, as displayed in Figure 2b [62]. The experiments demonstrated an outstanding bearing capacity and ductility in high-rise PFISB extreme dynamic situations [63]. ...
... Additionally, these IMCs cannot be removed once locked, making it challenging to reuse the IMU in the event of accidental damage during servicing. [60,61,63]; (c) beambeam bolted [66,67]; (d) beam-beam and column-column bolted [64]; (e) fully bolted plug-in connector [65]; and (f) column-column pre-tensioned [68,69] IMC. [60,61,63]; (c) beambeam bolted [66,67]; (d) beam-beam and column-column bolted [64]; (e) fully bolted plug-in connector [65]; and (f) column-column pre-tensioned [68,69] IMC. ...
... [60,61,63]; (c) beambeam bolted [66,67]; (d) beam-beam and column-column bolted [64]; (e) fully bolted plug-in connector [65]; and (f) column-column pre-tensioned [68,69] IMC. [60,61,63]; (c) beambeam bolted [66,67]; (d) beam-beam and column-column bolted [64]; (e) fully bolted plug-in connector [65]; and (f) column-column pre-tensioned [68,69] IMC. ...
Compared to traditional onsite steel construction, prefabricated industrial steel construction (PFISC) saves time, money, and resources. It results in sustainable steel structures that use fewer resources and are better for the environment. Despite their advantages, the private sector favors creating high-rise buildings in an old-fashioned way. In order to encourage the adaptability of prefabricated industrial steel buildings (PFISBs) in high-rise structures, this study critically evaluates the adaptable solutions offered in the literature on the recent developments, structural performances, present difficulties, and future potential. In mid-rise and low-rise structures, PFISC is frequently used. In research and case studies, PFISBs have proven to perform admirably under various adverse conditions, including in the event of an earthquake, wind, blast, impact, fire, collapse, and long-term sustained loads. The use of potential research solutions, the “Top-down” strategy, and the resolving of problems such as the structural-based design guidelines, column stability, discontinuous vertical and horizontal diaphragms, cluster columns and beams effect, damage-free and innovative inter- and intra-modular connections, high strength-to-weight modules, numerical simulation, and transportation will help PFISBs to become more widely accepted in high-rise structures. Compared to other materials, steel has recently demonstrated great promise for the construction of PFISBs. Additionally, China plans to increase their PFISC to 30% by 2026, Australia to 15% by 2025, and North America to over 5% by 2023, proving that it is a reasonable response to future urbanization concerns.
... The fact is that some joints have weaknesses due to problematic disassembly, spaciousness requirements, and sensitivity to installation errors. These problems are largely solved by rotary connections [18] and shear bolted and splined connections [18,19]. In addition, there is a problem with the vulnerability of modular buildings to seismic effects. ...
... The fact is that some joints have weaknesses due to problematic disassembly, spaciousness requirements, and sensitivity to installation errors. These problems are largely solved by rotary connections [18] and shear bolted and splined connections [18,19]. In addition, there is a problem with the vulnerability of modular buildings to seismic effects. ...
The article discusses a solution to the relevant task of analyzing and designing modular buildings made of blocks to be used in industrial and civil engineering. A block that represents a container is a combination of plate and beam systems. The criteria for its failure include both the strength of the individual elements and the loss of stability in a corrugated web. Methods of engineering analysis are hardly applicable to this system. Numerical analysis based on the finite element method is time-consuming, and this fact limits the number of design options for modular buildings made of blocks. Adjustable machine learning models are proposed as a solution to these problems. Decision trees are made and clustered into a single ensemble depending on the values of the design parameters. Key parameters determining the structures of decision trees include design steel resistance values, types of loads and the number of loadings, and ranges of rolled sheet thickness values. An ensemble of such models is used to take into account the nonlinear strain of elements. Piecewise approximation of the dependencies between components of the stress–strain state is used for this purpose. Linear regression equations are subjected to feature binarization to improve the efficiency of nonlinearity projections. The identification of weight coefficients without laborious search optimization methods is a distinguishing characteristic of the proposed models of steel blocks for modular buildings. A modular building block is used to illustrate the effectiveness of the proposed models. Its purpose is to accommodate a gas compressor of a gas turbine power plant. These machine learning models can accurately spot the stress–strain state for different design parameters, in particular for different corrugated web thickness values. As a result, ensemble models predict the stress–strain state with the coefficient of determination equaling 0.88–0.92.
... In practice, most inter-module connections are asymmetric in different directions. In response, Chen et al. [24] experimentally examined the shear behaviour of rotary intermodule connections in X-and Y-direction, respectively, while the shear load-displacement model was still not available. Chua et al. [25] theoretically derived the initial shear stiffness of vertical inter-module connection and proposed a translational spring model to simulate the shear behaviour. ...
... Chen et al. [24] Rotary inter-module connection: The connection includes upper and lower corner fitting and connector. ...
Modular steel constructions (MSCs) are increasingly used in mid- to high-rise buildings because of their advantages in higher manufacturing quality, faster on-site installation speed, higher material use efficiency, lower life-cycle cost, as well as some other environment-friendly features. Shear tests of vertical inter-module connections with bolts and shear keys, which play a critical role in the lateral performance of MSCs, were carried out to investigate their shear load-carrying capacities and shear mechanical characteristics. Refined numerical models were established, calibrated against the test results and used to simulate the shear behaviour of vertical inter-module connections. The effects of friction coefficient and axial compression ratio on the shear behaviour were investigated. The connections were shown to exhibit excellent initial shear load-slip behaviour and shear load-carrying capacity under shear load. In terms of initial shear stiffness and slip resistance, the axial compression ratio and friction coefficient were shown to be the critical parameters, while the shear key and high-strength bolt dominated the ultimate shear resistances. Shear processes of vertical inter-module connections in different shear directions were almost consistent, which can be divided into the micro slipping stage, macro slipping stage, bearing stage and failure stage. Through geometrical parameters correlation analysis, a piecewise polynomial simplified shear load-deformation model was proposed for predicting the shear load-deformation relationship. The proposed model was shown to be capable of accurately capturing the shear behaviour of the connection, and is therefore recommended for use in engineering applications and future research on inter-module connections.
... ceiling beam i b . Considering that the shear stiffness of the vertical inter-module connection was much larger than the lateral stiffness of a single module [35][36][37], the horizontal spring stiffness of each vertical inter-module connection was taken as infinity, i.e., k s = ∞. ...
... Joint shear tests were carried out on three types of connections between vertical modules in Refs. [35][36][37]. The shear stiffness of specimen C2 was the smallest at 153299 N/mm [35]; this value was taken as the horizontal spring stiffness to investigate the shear performance of the existing vertical inter-module connection in the overall structure. ...
The lateral displacement of a column-supported modular steel structure with semi-rigid con�nections (CSMSS-SRC) owing to lateral loading was investigated to determine the corresponding
lateral displacement mode and establish a foundation for a direct displacement-based seismic
design method. Theoretical equations for the lateral displacement caused by the bending defor�mation of beams and columns, axial deformation of columns, and shear deformation of the
vertical inter-module connections were theoretically derived using slope–deflection equations,
unit-load method, and shear deformation definition, respectively. Two simplified single frame
finite element models were then established to verify the theoretical equations and study the
effects of the rotational and horizontal shear stiffnesses of the vertical inter-module connections
on the lateral displacement of the CSMSS-SRC. The results showed that the proposed lateral
displacement equations are highly accurate. Furthermore, although the rotational stiffness of the
vertical inter-module connection did not exert an appreciable effect on the lateral displacement of
the CSMSS-SRC, its horizontal shear stiffness did. These results are expected to provide a refer�ence for the engineering design of CSMSS-SRC.
... Various innovative inter-module connections, such as bolted inter-module connections [12][13][14][15][16][17][18], plug-in inter-module connections [19][20][21][22][23], and prestressed inter-module connections [24][25][26], have been proposed in recent years to provide solutions for rapidly assembling the modules [10,11]. The mechanical behavior of some inter-module connections was further researched through the tensile [21,27,28], shear [28][29][30][31], and bending experiments [26,31,32]. Then the seismic behavior of new modular joints [13,[19][20][21]23,24,[33][34][35] was experimentally clarified through the designed T-shaped or cruciform-shaped specimens, and the results showed that the ductility of these modular joints highly depends on the plastic capacity of intra-module connections. ...
... Various innovative inter-module connections, such as bolted inter-module connections [12][13][14][15][16][17][18], plug-in inter-module connections [19][20][21][22][23], and prestressed inter-module connections [24][25][26], have been proposed in recent years to provide solutions for rapidly assembling the modules [10,11]. The mechanical behavior of some inter-module connections was further researched through the tensile [21,27,28], shear [28][29][30][31], and bending experiments [26,31,32]. Then the seismic behavior of new modular joints [13,[19][20][21]23,24,[33][34][35] was experimentally clarified through the designed T-shaped or cruciform-shaped specimens, and the results showed that the ductility of these modular joints highly depends on the plastic capacity of intra-module connections. ...
The rib stiffeners are usually used to reinforce the intra-module connections in corner-supported modular steel buildings; however, may be conflicted with the internal wall panels. There is a lack of relevant understanding of the effects of reinforcing intra-module connections on the seismic behavior of corner-supported steel modular structures. Therefore, this study investigated the effect of the intra-module connections reinforcing details on the seismic behavior of such modular structures. Such proposed reinforcing measures comply well with the architectural internal finishing demand, including vertical stiffeners or cover plates and an enlarging ceiling beam section. Four full-scale two-story plane frame structures were designed and experimentally examined under lateral cyclic loading to investigate and compare their seismic performance, such as the hysteretic performance, skeleton curves, and strain distribution. The experimental results showed that these reinforcing measures were helpful for the development of plastic deformation of such corner-supported modular structures through effectively moving local buckling away from the beam ends. Moreover, the reinforcing intra-module connection details were able to enhance the force resisting capacity and initial lateral stiffness of the overall structures. Additionally, the nonlinear finite-element (FE) modeling was developed and validated against the corresponding experiment. It showed satisfactory agreement with the failure responses and load–displacement curves. The plastic strains at reinforcing intra-module connection were further analyzed through the validated FE models, and the design suggestions were given accordingly.
... The FEA modelling techniques have been validated by simulating experimental tests on three separate IMCs studied by Chen et al [29] in figure 5 (a), Lacey et al. [30] in figure 5 (b), and Chen et al [31] in figure 5 (c) and the laminated elastomeric bearing (LEB) studied by Rahnavard and Thomas [32] in figure 5 (d). In addition, the validation of the calibrated material models presented in the previous section is also completed by simulating the experimental characterisation tests for rubber in figure 5 (e) and SMA in figure 5 (f). ...
Inter-module connections (IMCs) play a crucial role in the structural behaviour of steel Modular Building Systems (MBSs) by ensuring the vertical and horizontal load-transfer paths between modules, yet existing designs display limited disassembly opportunities and lack damage control features. This study introduces a novel, hybrid demountable IMC comprising bespoke corner fittings, a resilient high-damping rubber core and a shape-memory alloy (SMA) bolt. Proof-of-concept connection tests have been carried out using validated, continuum finite element analysis (FEA) to determine the mechanical behaviour of the proposed IMC with respect to the main deformation modes expected to occur in the joints of tall steel MBSs under the combined effect of vertical and horizontal loading. Main findings show that both the HDR core and the SMA bolt contribute effectively to the overall hybrid response of the IMC under tension and combined compression and shear loading, preventing the formation of significant plastic damage in the MBS’s corner fittings to facilitate reusability of modules.
... These findings provide insights into the complexity of deformation and residual stresses involved in the lap joints of layered stainless steel plates during multi-layer welding processes. Furthermore, according to [12], the technical challenges associated with these welding processes significantly contribute to the general understanding of the welding effects on layered stainless steel materials in the context of multi-layer welding. These insights have not fully examined the comparison of current strength usage and combined welding direction model parameters, but they can assist designers and industry practitioners in developing more effective welding strategies while minimizing adverse effects on structural and material performance. ...
The welding process plays a central role in the welding industry, where the joint zone undergoing the welding process experiences structural and mechanical property changes. This research evaluates the comparison of current strength and parameters in the directional welding joint model, a critical aspect of addressing common weaknesses in welded joints. The research objects include four current levels (100, 120, 140, 160 A) and three types of welding directions (longitudinal, transversal, and combination). The aim of this study is to detect the optimal combination in welded joints that can produce a maximum tensile strength ratio. The research method involves tensile testing on various specimen models of joint types at specific current strength levels. The research results indicate that at the current strength level of 120 A, the combined directional welding joint model (longitudinal+transverse) provides a maximum tensile strength reaching 335.370 MPa. This finding stands out significantly, surpassing the tensile strength values at other current levels and welding model types, such as at 100 A (331.574 MPa), 140 A (332.315 MPa), and 160 A (332.685 MPa). This discovery highlights that the combined joint model yields a substantial improvement in joint strength, making it an optimal solution for various current strength levels and joint models. The key feature of this research involves specific recommendations for the welding industry, including guidelines on selecting optimal parameters to enhance the tensile strength of joints. The directional welding joint models can be a reference in designing welding procedure specifications to incorporate construction elements using ST 42 material. This research contributes both theoretically and practically, offering opportunities for improving efficiency and structural safety in the welding process, thus positively impacting the quality of joints in construction and manufacturing applications
... Researchers and engineers have recently paid more attention to modular buildings' IMCs. Extensive state-of-the-art literature studies on the structural performance of IMCs were conducted in [8,11,14,[16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35]. While the internal area between the adjacent modules is still the most prone, various (internal) inter-module connection techniques have been proposed in the available literature that aim for easy and fast installations using bolted shear keys, plates, grouts, etc. [10,28,[36][37][38][39][40][41][42][43][44][45]. ...
Interlocking Inter-Module Connections (IMCs) in Modular Steel Buildings (MSBs) have garnered significant interest from researchers. Despite this, the optimisation of plate thicknesses in such structures has yet to be extensively explored in the existing literature. Therefore, this paper focuses on optimising the thickness of interlocking IMCs in MSBs by leveraging established experimental and numerical simulation methodologies. The study developed various numerical models for IMCs with plate thicknesses of 4 mm, 6 mm, 10 mm, and 12 mm, all subjected to compression loading conditions. The novelty of this study lies in its comprehensive parametric analysis, which evaluates the slip prediction model. A random forest regression model, trained using the ‘TreeBagger’ function, was also implemented to predict slip values based on applied force. Sensitivity analysis and comparisons with alternative methods underscored the reliability and applicability of the findings. The results indicate that a plate thickness of 11.03 mm is optimal for interlocking IMCs in MSBs, achieving up to 8.08% in material cost reductions while increasing deformation resistance by up to 50.75%. The ‘TreeBagger’ random forest regression significantly enhanced slip prediction accuracy by up to 7% at higher force levels.
... Numerous studies have examined the unidirectional mechanical properties of inter-module connections in the worst practical scenario, including axial compressive [15,16], tensile [17][18][19], flexural [20][21][22][23][24], and shear properties [17,[25][26][27]. The overall numerical model considers inter-module connections' shear, axial, and moment-rotation behaviors to better understand the global structural responses [28]. ...
Modular steel buildings (MSBs) consist of complete steel modules and inter-module connections; the latter plays a crucial role in assembly efficacy on-site and in resisting the tension load at the base of a high-rise modular building subjected to lateral loads. This paper investigates the tensile performance of the proposed self-locking inter-module connection. Two full-scale experiments were conducted to evaluate the axial tensile behavior of this innovative connection. The mechanical properties of the self-locking inter-module connection were obtained and analyzed, including the failure modes, ultimate bearing capacity, and strain distribution. Under axial tension load, the self-locking inter-module connection exhibited adequate load-carrying capacity and ductility, as evidenced by the results. The refined finite element (FE) model of the self-locking inter-module connection was developed and validated against experimental data. Then, FE modeling was used to further investigate the working mechanism of the self-locking inter-module connection under axial tensile force. Two essential parameters were considered, including the bottom plate thickness of the upper corner fitting and the top plate thickness of the lower tenon. The numerical results demonstrated that the failure mode of such a self-locking inter-module connection was dependent on the relative relationship of the aforementioned two key parameters, which is reflected by the ratio (Kt) of the vertical shear area of the bottom plate of the upper corner fitting and the top plate of the lower tenon. Considering tensile resistances and material strength utilization, a range of values for the parameter Kt and design recommendations were provided.
... A steel plate welded to the sleeve establishes horizontal connections between adjacent modules. Chen et al. [9][10][11] also proposed another connection, as illustrated in Fig. 1(b), to connect the upper and lower module columns. This involves hoisting and bolting through openings in the module columns. ...
Modular Integrated Construction (MiC) has gained prominence as a construction method, and the integrity of its
structural connections plays a critical role in ensuring the overall stability and safety of buildings. This paper
presents an experimental investigation into the static and hysteretic performance of grouted steel beam-column
inter-connections designed for MiC. The study examines eight full-scale specimens subjected to both monotonic
and cyclic loading conditions, with a focus on failure characteristics, deformation behavior, loading-
displacement curves, loading-strain curves, skeleton curves of hysteretic loops, stiffness degradation, and energy
dissipation. Key findings of the study include the observation of weld cracking between beam flanges and
columns in all specimens, highlighting the necessity of welding quality control to prevent such issues. Grouted
connections exhibited superior integrity, with no gap opening or misalignment between upper and lower columns.
Additionally, it was found that grouting could enhance the stiffness of certain connections. Removal of
diagonal stiffeners significantly decreased peak bearing capacity, emphasizing their importance. The composite
action brought about by bolts connecting ceiling and floor beams also proved influential. According to Eurocode
3, all grouted specimens fall under the classification of semi-rigid connections, with a distinction made for partial
and full-strength connections. This research contributes valuable insights into the static behavior and hysteretic
performance of grouted steel beam-column inter-connections for MiC, providing essential knowledge for the
structural design and safety of buildings utilizing this innovative construction method.
... Among the various forms of off-site construction, modular construction is the one whose assemblies delivered to the site show the greatest level of completion [3]. Methods for assembling prefabricated modules are currently the subject of intense research because inter-modular connections (IMCs) are a crucial part of off-site construction as they serve a prominent role in the structural integrity of modular building systems [4][5][6][7][8][9][10][11][12][13]. Rajanayagam et al. [10] reported 25 existent IMCs, out of which none fully met all the requirements for off-site construction, and argued that only automated or semi-automatic connections have the ability to resolve both constructional and functional requirements [10]. ...
Modular construction is characterized by assembling volumetric units on site. Once assembled on site, the structural integrity of modular buildings highly relies on connections that provide essential performance against critical loading conditions. Connections significantly impact field assembly activities, and previous research has highlighted the importance of their functional performance. In this study, the researchers focus on implementing automated connecting devices in a full-scale experimental project. It presents the implementation of a self-locking inter-modular connector and an investigation of the benefits and limitations of its application in modular building systems. This study also investigates the use of connectors as attachment points for modular handling and lifting. It evaluates the pros and cons of combining a single device’s connecting and lifting functions. The implementation of an automated connecting device in the building design process is covered as well as the evaluation of its impacts on architectural, structural, and functional considerations. Finally, the potential of automated connecting devices to improve modular building systems’ overall performance and efficiency is assessed, and guidelines are identified to facilitate their adoption.
... Another post-tensioned connection was also developed in Ref. [6]. Chen et al. [7] proposed a rotary inter-module connection, in which columns in the stacking modules were connected through a protruded bolt rod. Hou et al. [8], Shi et al. [9,10], Corfar and Tsavdaridis [11], Yang et al. [12] also proposed a series of novel intermodule connections in their studies. ...
Module-to-core wall connection for assembling modules to the core wall system plays a key role in transferring loads in modular high-rise buildings. However, its mechanical mechanisms are not systematically understood. This study proposes an innovative module-to-core wall connection, which could be installed and detached with good feasibility and efficiency during construction and detachment processes. The roles that module-to-core wall connections play in steel-framed modular high-rise buildings are discussed. The hysteretic behaviors, stiffness deterioration, energy dissipation and failure process of the connection against cyclic load are investigated, and resistances of the connection against extreme loads are examined. Parametric analyses are conducted to study influences of strengths of critical components on resistance of the proposed connection. Results show that the proposed connection has good mechanical behaviors against cyclic load and has sufficient resistances against extreme loads. The connection behaves within an elastic range during the working stage and has good vibration isolation capability. The failure of the connection subjected to cyclic load is caused by the fracture of the end of beams, while those subjected to extreme loads are governed by fractures of connector assembly and bolts. Finally, a series of design equations is proposed to predict resistances of the module-to-core wall connection with good accuracy. The present study provides useful references for the application of module-to-core wall connection in steel-framed modular high-rise buildings.
... Chen et al. [20] introduced cast plug-in devices for horizontal connections and high tensile strength bolting for vertical ones. However, these bolted connections, due to their strict installation requirements on the installation accuracy and require opening holes in beams or columns, pose potential architectural concerns [39]. Dhanapal et al. [29] presented modules connected via VectorBloc connectors. ...
This paper presents a novel approach for steel modular structures, incorporating the S-CN connector – a hybrid tie rod and connector connection method – along with rectangular hollow section (RHS) steel members. The study numerically investigates the mechanical behavior of S-CN connectors and their application in beam–column connections under compressive loading. The compressive load-bearing capacity of the proposed connection is determined following AISC 360-16 guidelines, predicted through a finite element analysis approach and validated by experimental data. Parametric analysis reveals the impact of local buckling in modular nodes on the connector’s load-bearing capacity. The results demonstrate that tie plate thickness has a minimal effect, while reducing the modular node thickness leads to a linear decrease in load capacities. Furthermore, the failure mode of the beam–column connection depends on the compressive capacities of both the RHS column and the S-CN connector.
... FEA validation I is conducted on the IMC with a rotary locking device studied by Chen et al. [89,90]. The experimental setups and corresponding numerical models are illustrated in Fig. 10. ...
The recent technological advancements achieved in modular construction have accelerated the trend of building taller self-standing steel modular building systems (MBSs), leading to a consensus among researchers regarding the vital role that inter-module connections (IMCs) play in the structural performance of MBSs subjected to extreme lateral loading. However, existing IMCs are typically designed such that the global structural system heavily relies on the hysteresis of the steel framing member, leading to severe sustained damage and costly, impractical retrofitting programmes. To unlock the full “disassembly and reuse” potential of steel MBSs, IMCs can be designed to contribute more effectively to the global damage distribution mechanism, by engaging specific “fuse” components which are easy to replace, improving the reuse prospects of volumetric modules. In this regard, the present study proposes a novel, hybrid IMC using custom corner fittings, a high-damping rubber (HDR) core and a shape-memory alloy (SMA) bolt. Calibrated and validated material models using data from experimental material characterisation tests have facilitated the full characterisation of the hybrid mechanical response, determining the deformation modes, stress states, hysteresis loops and mechanical parameters. The parametric FEA included the variation of bolt preload, endplate thickness, axial load magnitude and the vertical layout of the HDR core. The study represents a preliminary, proof-of-concept investigation, showcasing the favourable cyclic performance of the proposed IMC under the main deformation modes expected in tall self-standing MBSs during lateral loading. Due to the effective contribution of each component to the combined hybrid response, the connection succeeds in preventing the formation of significant plastic damage in the MBS’s corner fittings to facilitate reusability of modules.
... In many of the recent IC proposals, intermediate elements are used to connect the modules. E.g., ''plug-in'' type connections (male-female type connection) that facilitate the alignment of vertically stacked modules and ensure the vertical connectivity of MBSs [23,25,35,52]. Also, in some cases, male-female connections are used along with a tie/transfer plate to connect adjacent side-by-side modules horizontally [23,24,29,37]. ...
Modular constructions are off-site prefabricated structures with transportable units assembled on-site. These units are linked together using mechanical connectors called “inter-modular connections”. Modular building structures are attractive from a constructional efficiency point of view if they include specific characteristics such as ease of on-site assembly and speed of construction. Accordingly, a vertically unconstrained inter-modular connection can considerably decrease the construction effort and promote the feasibility of the modular system if tension forces do not develop in columns when the structure is submitted to lateral loads. This study presents an efficient vertically unconstrained inter-modular connection, including a bolted tie plate and male–female components to ensure the connectivity of the diaphragms and columns. Two series of experimental tests are performed to examine the proposed inter-modular connection’s shear and axial force responses. The calibrated finite element models developed in ABAQUS software are used to study the in-plane shear behavior of a perforated plate acting as horizontal component of the inter-modular connection. The results show that the proposed connection has adequate ductile ultimate strength controlled by the yielding of the net section of the tie plate. However, removing the up-lift constraining mechanisms may lead to serviceability issues due to a potential slip occurrence between modular components constructed with tolerances. The experimental and numerical results/frameworks presented herein provide detailed behavioral information, including slip, yielding, and failure modes of the connection’s components. The captured behavior can be used to develop a simplified model of the proposed connection that can be used in detailed structural analyses.
... Experiments and numerical simulation were performed to study the shear force-displacement and load-slip behaviors of the connection and the influence of the preload and slip factor on the behavior. Chen et al. [14] raised an innovative rotary inter-module connection, and the mechanical performance was studied through two tensile and two shear resistance tests. And then based on the parametric analysis, the formulas for tensile and shear bearing capacities were developed and verified. ...
High extent of mechanized assembly is one of the development concepts of the modular construction, allowing the full development of its superiority in construction efficiency and quality. The primary focus of this research is to propose novel types of connecting techniques between the haunch brace and the module in the self-centering modular steel structure (SC-MSS) connection system, which horizontally inserts the long through-bolts inside the columns or fixes the sleeve device by bolts around the periphery of the columns to achieve stable and effective connecting performance and well installation convenience at the construction site. The functional mechanism of the traditional and novel haunch connecting techniques are clarified and the seismic performance of the SC-MSS connections with different connecting techniques are investigated due to monotonic and cyclic loadings. Results demonstrate that the strength and stiffness of all connections develop as the similar trend and stable hysteretic responses with satisfactory self-centering capability can be observed. Furthermore, the haunch reaction force is reasonably distributed and effectively transmitted under the proposed connecting techniques, which could control the stress level in the haunch intersection regions of the modules and well protect the key structural members. The mechanical and deformation mechanisms of the haunch connecting techniques are analyzed and some design considerations are provided accordingly for offering the guidance for the engineering design and application of SC-MSS connection systems.
... To name a few, Sharafi et al. (2018), Chen et al. (2020), Annan et al. (2009), Loss et al. (2016, Sendanayake et al. (2019), Bowron et al. (2014), Park et al. (2015), and Dai et al. (2018) proposed new connecting devices. As illustrated in Figure 1, modular joints are typically located in the corners of the modules, which allows to concentrate connection in specific points and to concentrate external load of the buildings to these transfer points. ...
... So far, existing inter-module connections have been influenced by conventional design methods, relying on bolts [4][5][6][7][8], welds [9], grout [10], or post-tensioning [11][12]. These methods often require laborious on-site tasks, hindering the demountability of MBS. ...
A new inter‐module connection was developed, adopting structural topology optimisation (STO) and the inter‐locking method of joining. The structural performance of the connection was assessed through a series of monotonic and cyclic FE analyses. Results revealed that the structural behaviour of the new connection was comparable to that of other inter‐module joints in the literature, while managing to tackle their limitations by introducing both an easy‐to‐install and easy‐to‐disassemble configuration with promising opportunities for reuse, demonstrating that inter‐locking joints can be worthy competitors for traditional means of attachment in the future of modular construction.
... The modular steel building (MSB) is one of the most widely-used building adopting MiC method. In current literatures, studies on the mechanical performance of the MSB were conducted mainly in the following two aspects: the connection level [2][3][4][5][6][7][8][9][10][11][12][13] and global structure level [14][15][16][17][18][19][20][21][22][23][24][25][26]. At the connection level, Zhai et al. [2] studied the static and hysteretic performance of the bolted-cover plate connections in MSB under both monotonic and cyclic loads. ...
A R T I C L E I N F O Keywords: Modular integrated construction Modular steel building Rigid body Pushover analysis Dynamic amplification factor A B S T R A C T This paper numerically studies the anti-collapse behavior of the modular steel building (MSB) in the scenario of interior module removal and corner module removal. The vertical displacement, lateral displacement and internal force of a six-storey MSB in a sudden module loss are studied. The reasonability by using rigid body assumption in collapse analysis of the MSB is examined. A refined fracture model of the steel is incorporated into ABAQUS via user subroutine, in which the effects of both stress triaxiality and Lode angle on the fracture ductility of the steel are considered. In the pushover analyses, the effects of the horizontal connection, opening of the wall panel and thickness of the wall panel on the collapse resistance and failure mode of the MSB are studied. The dynamic amplification factor (DAF) of the MSB at the collapse limit state is also obtained. It is found that the rigid body assumption may significantly underestimate the displacement and maximum shear force in the horizontal connection of the MSB. Two types of failure modes of the structure are observed, namely, connection failure-induced collapse and module unit failure-induced collapse. Among the studied parameters, the effect of the opening size of the wall panel on the behavior of the structure is the most significant. In the scenario of the interior module removal and corner module removal, the DAFs of the structure at the collapse limit state range from 1.20-1.29 and 1.27-1.50, respectively.
Modular integrated construction (MIC) has gained more popular attentions from both researchers and engineers due to its advantages of construction efficiency and environmental friendliness. The paper conducted a comprehensive review study on different structural systems for MIC including fully modular structure (FMS), mixed modular structure (MMS) and in-fill modular structure (IFMS), the architectural, structural and constructional characteristics are discussed in detail for each modular structure with typical applications. Afterwards, one innovative IFMS based on sparse-component frames (IFMS-SCF) was proposed and comparative analyses were provided between IFMS-SCF and previous modular structures. Results reveal that different modular structures vary greatly in their principal lateral resisting structures, applicable height, construction efficiency and architectural flexibility. IFMS-SCF can be one promising structural system used for high-rise MIC with enhanced construction efficiency and great potential in the brand-new residence style.
Modular steel buildings (MSBs) interlocking inter-module connections (IMCs) have piqued researchers’ interest. However, the existing literature has not yet studied the optimisation of its plate thicknesses. This paper, therefore, focuses on optimising interlocking (IMCs) plate thickness in (MSBs), leveraging previous experimental and numerical simulation methodologies. Various numerical models for four MSBs interlocking (IMCs) with plate thicknesses (4 mm, 6 mm, 10 mm, and 12 mm) were developed under compression loading conditions. The study’s novelty lay in its comprehensive parametric analysis, which evaluated the slip phenomenon in (MSBs) connections and introduced a slip prediction model validated against empirical data. Further innovative machine learning approach was utilised to predict slip values based on applied force through a random forest regression model trained using the 'Treebagger' function. Sensitivity analysis and comparisons with alternative methods were utilised to underscore the reliability and applicability of the findings. The results showed that 11.03 mm was the optimal plate thickness for interlocking (IMCs) in modular steel buildings, with up to 8.08% reduced material costs. Increasing plate thickness boosts its deformation resistance by up to 50.75%. ‘TreeBagger’ random forest for anomaly detection and machine learning improves slip prediction up to 7% at higher force levels.
Intermodular connections play an important role in the constructability and performance of modular building structures. The wind-generated vertical uplift force and the lateral load on modular structures raise concerns about the tensile and shear capacity of the intermodular connection joints. This study focuses on investigating the change in load response behaviour, working mechanism and performance of endplate-type intermodular connections with varying design parameters. Initially, the paper presents the design criteria of endplate-type intermodular connections and their behaviour, with a detailed theoretical approach, to identify their performance and capacity under tensile and shear loads. Then, the capacity of the proposed connections in this study was evaluated based on both the presented theoretical design and numerical approaches. The design inspiration for the proposed connection was taken from literature using which the finite element models for 4 specimens were developed and validated. The validated connection models were then used to conduct parametric studies for 11 proposed models, focused on changes in base endplate thickness (8 mm, 10 mm and 12 mm) and steel grade (s275 and s355), bolt hole diameter (22 mm, 26 mm and 30 mm) and tolerance, bolt grade (8.8, 10.9 and 12.9) and applied preload (0, 50 kN, 90 kN and 110 kN) with and without additional plate over oversized bolt holes. The results obtained from both shear and tensile performance analysis indicate that the change in proposed design parameters has a greater impact on shear over tensile behaviour and capacity. Further, the conducted parametric studies helped in identifying the optimum design parameter combinations for enhanced connection performance which are also cost-effective and ideal for an onsite installation. Finally, the paper suggests recommendations for future research and essential advancement in the endplate-type intermodular connection design in enhancing performance and presents the practical limitations and challenges in using such techniques.
Modular or offsite construction is believed to shape the future of the construction industry as it possesses significant benefits over traditional onsite construction methods. However, most of its application are limited to steel or concrete buildings. Although steel‐concrete composite structural system has many merits over the steel and concrete systems, its application in modular buildings is very limited. This paper explores recent developments of composite systems for modular high‐rise buildings. They include modular units for resisting vertical gravity loads and lateral structural systems for resisting horizontal forces from wind and earthquake loadings and progressive collapse due to accidental loads such as fire, explosions and impact. Various inter‐module joining methods developed in the literature will also be reviewed. Finally, a case study of the most efficient connection is presented to explore its applicability to high‐rise modular buildings.
Modular Steel Buildings (MSBs) are a new structure consisting of fully assembled volumetric units. The inter-modular connections are essential components contributing to MSB’s onsite assembly and structural safety. It is necessary to have a precise and valuable intermodular joining system that allows for efficient load transfer, safe handling, and the most efficient use of the modular components’ strength. The majority of inter-module connections are currently manual vertical column-to-column welded, bolted, or prestressed, which has a lot of shortcomings, including poor quality, inefficient construction, lack of space, full connectivity, and incompatibilities with interior design. Moreover, due to a discontinuous horizontal diaphragm and vertical walls, the lack of horizontal and vertical beam-to-beam connections between modular units reduces in-plane and out-of-plane stiffness and uniform lateral force transmission. To overcome the concerns mentioned above, this study first presents a unique self-locking automatic vertical column-to-column inter-modular connection that uses connection boxes with spring-loaded tenons and mortises with tongues and grooves to achieve vertical connectivity. Then, to guarantee horizontal diaphragm continuity, a horizontal beam-to-beam interlocking connection with a continuous group of interlocking clips with sigma-shaped tongues and grooves is proposed, welded on modular floor beams. Then, a vertical beam-to-beam interlocking connection with a group of interlocking clips is developed, welded on beams offsite to achieve vertical diaphragm continuity. The proposed vertical and horizontal connections satisfy simple splicing, non-welding, easy installation, complete and robust connectivity, and reliable connection characteristics. Furthermore, finite element analysis revealed that developed connections enhance in-plane rigidity and improve MSB vertical and horizontal connectivity, maximizing modular building assembly benefits.KeywordsDiscontinuous modular steel buildingsColumn-to-column automatic connectionBeam-to-beam vertical diaphragm connectionBeam-to-beam horizontal diaphragm connectionFinite element analysis
Modular steel buildings (MSBs) can meet the needs of building industrialization and have been developed in many countries. The inter-module connection is crucial to the overall performance of MSBs. An inter-module connection with bolt and shear key fitting was proposed in this paper, which is convenient for the on-site erection of the steel modules. The flexural performance of the connection was studied. Static tests were carried out to study the contribution of the key load-bearing components to the flexural performance of the novel connection. A finite element model was then proposed and verified, by which a parametric analysis to study the effects of the key components was conducted. It is found that the parameters significantly affecting the flexural performance of the connection include the diameter of the bolt and the thickness of the bottom plate. The results also showed that the contribution of the shear key to the flexural performance of the connection could be ignored. The flexural performance of multi-module connection was studied, and the results revealed that the multi-module connection can be designed as multiple two-module connections. Formulas for calculating the flexural capacity and rotational stiffness of the connection were finally proposed and verified.
Due to the advantages of high integration, modular steel buildings have recently received extensive attention and research. The connection between modules (inter-module connection) plays an important role in ensuring the safety and integrity of modular steel buildings. However, most of the existing inter-module connections have problems such as insufficient construction space, difficulty in disassembly, lack of design specifications, etc. An innovative inter-module connection with bolt and shear key fitting was proposed. The connection separates the horizontal load-bearing component and the vertical load-bearing component, which greatly reduces the difficulty of analysis and design. The structure of the connection is convenient for construction and insensitive to installation errors. The structure and advantages of the connection were introduced in this paper, and the shear performance of the connection was studied by the monotonic static test. A finite element model verified with the experiment was proposed to simulate the shear performance of the connection. The influence of errors in fabrication on the performance of the connection was studied using the finite element model, and connection’s operating status in a modular frame was analyzed. Thus the allowance for the clearance between the shear key and slot was obtained. Based on the experimental and numerical study results, a formula was proposed to predict the shear capacity of the connection for the practical design of inter-module connection in modular steel buildings.
Despite the advances of modular construction, the comprehensive understanding of its technical aspects in buildings is still limited, especially during the implementation process. This paper reviews the technical aspects of planning and coordination of modular construction in the building industry. The unclear onsite and practical knowledge need to be clarified for the implementation process. It then leads to the questions on the status of research development and gaps of the technical aspects. One hundred and thirty papers were filtered and analyzed through a systematic review. Four technical aspects of modular construction were found, namely (a) feasibility aspects of modular construction, (b) types of construction or materials, (c) design and structural analyses, and (d) construction planning. The findings render insightful references for the successful delivery of modular construction including its lifecycle analysis and sustainability needs. A research framework is also developed to highlight the gaps and measures for future practice.
In the recent history the development of inter-module connection (IMC) systems for steel modular building systems (MBSs) has gained traction with many researchers and engineers being in pursuit of universally performant connection systems. Even though many of the newly proposed connections are presented as potential disruptors for the market, it rarely is the case as it is a difficult, if not impossible task, to deliver a “fit-for-all” design given the complex and multi-dimensional character of this topic. While recently, there have been numerous review studies concerned with IMCs for hot-rolled steel MBSs, most of them focused only on a limited number of existing connections, while also failing to preserve a consistency in nomenclature and classification methods. Considering the large and growing volume of published studies which investigate IMCs for hot-rolled steel MBSs, there is a pressing need to classify all systems under a unified naming convention based on a systematic classification and thus harmonise the literature and promote a well-structured development of future designs.
The present study gathered sixty IMCs from the literature and proposed a nomenclature using a rigorous and consistent classification based on the method of joining. Complementary tables with all relevant studies published on each connection system are constructed, providing a comprehensive review of the existing literature at the time and helping to guide the development of future studies in an effort to promote a unified approach. In order to identify “must-have” features and key areas of improvement for future IMC designs based on the advantages and limitations of existing connections, a multi-attribute ranking system is developed and employed. The adoption of the proposed ranking system has the potential to facilitate the improvement of future designs, as well as to enhance existing connections in low-scoring areas, serving as a useful decision-making tool for both researchers and practitioners concerned with this topic.
To improve the constructability and performance of modular buildings, a number of inter-module connections have been developed, each with their own associated advantages and disadvantages. Interlocking inter-module connections have emerged as a promising type of improvement; however, it is not clear how to provide the required installation tolerance without allowing slip. At the same time, the existing model for the shear force-slip behaviour is known to be inadequate. This study introduces a novel interlocking inter-module connection which combines structural bolts with interlocking elements to improve the constructability and shear force-slip behaviour. An experimental study was conducted to investigate the shear force-slip behaviour of the proposed connection. The effects of the interlocking elements, bolt preload, hole tolerance, and fabrication and assembly tolerance on the shear behaviour are evaluated and discussed. Numerical simulations were carried out to support the experimental program, following which the distinguishing features of the force-slip behaviour were examined, and an empirical model was proposed.
In modular steel buildings the inter-module connections are key to the successful site installation of modules and the overall structural behaviour of the assembled building. The existing connection details such as site welding typically require external access during site install, which is not always possible or practical. Post-tensioned bolted steel connections are an enticing solution because they minimise the requirement for site work, allowing for easier internal assembly. However, the existing shear force-displacement model for inter-module connections is inadequate, and the initial load-slip behaviour is not accurately predicted. In this study, a new post-tensioned bolted steel connection is proposed and the prototypes are manufactured. The shear force-displacement and load-slip behaviours are investigated experimentally. The proposed connection is shown to have good initial stiffness in shear, which can be well controlled by the parameters of preload and slip factor. In addition, numerical simulation is conducted and the influence of the preload and slip factor on the load-slip behaviour is investigated. An improved empirical model is developed, and its application is demonstrated for the proposed connection.
This study proposes an effective steel frame modular system and evaluates the structural performance of its beam-column connection through experimental and analytical work. The new steel frame modular system utilizes the blind bolts, which allow free access to the structural members of the closed cross-section. In addition, the new modular system is designed such that the strength of its beam members is considerably lower than that of its column members to implement the strong column-weak beam concept. In order to investigate the effectiveness of the proposed modular beam-column connection, two types of specimens were designed and tested. One of the two specimens has four knee brace members to increase the bending stiffness of the connection, while the other does not have these components. The applied load versus displacement curves are plotted for the two specimens, and their failure modes are identified. Finally, a simplified analytical model for the modular beam-column connection is proposed, and its effectiveness is validated by performing its push-over analysis and comparing its results with the test results.
In current practice, the force-displacement and moment-rotation behaviours of inter-module connections for modular steel buildings are established by a combination of theoretical, experimental, and numerical analyses. The simplified connection behaviour is then incorporated into a numerical model of the overall structure for analysis and design. For engineering design analysis, it is desirable to estimate the inter-module connection stiffness by means of simplified calculations. Methods for estimation of the stiffness of traditional steel connections are available in the literature, however, their application to inter-module connections (also known as inter-connections) remains to be investigated. This paper summarises existing inter-connection details, including their purpose and associated design methods and models. The inter-connections selected from the literature provide details of the typical force-displacement and moment-rotation behaviours. For the selected inter-connections, the numerical and experimental results are compared with the calculated theoretical results predicted by existing theoretical models. The existing theoretical models are compared, and their limitations are outlined.
Prefabrication by off-site manufacturing leads to a reduced overall construction schedule, improved quality, and reduced resource wastage. Modular building is therefore increasingly popular and promoted. With the recent promotion a number of relevant studies have been completed, however, a review of the design, construction, and performance of modular buildings under different loading conditions is lacking. This paper presents a state-of-the-art review of modular building structures. First, structural forms and construction materials are presented as a brief introduction to the modular structures. Modular building is shown to refer not to a single structure type, but a variety of structural systems and materials. These modular structures might perform differently to similar traditional structures and the structural performance is highly dependent on inter- and intra-module connections. The structural response of modules to different hazards is then considered, followed by the current design practice and methodology. As a currently developing area there is great potential for innovation in modular structures and several key research areas are identified for further work.
Modular systems have been mostly researched in relatively low-rise structures but, lately, their applications to mid- to high-rise structures began to be reviewed, and research interest in new modularization subjects has increased. The application of modular systems to mid- to high-rise structures requires the structural stability of the frame and connections that consist of units, and the evaluation of the stiffness of structures that are combined in units. However, the combination of general units causes loss of the cross-section of columns or beams, resulting in low seismic performance and hindering installation works in the field. In addition, the evaluation of a frame considering such a cross-sectional loss is not easy. Therefore, it is necessary to develop a joint that is stable and easy to install. In the study, a rigidly connected modular system was proposed as a moment-resisting frame for a unit modular system, and their joints were developed and their performances were compared. The proposed system changed the ceiling beam into a bracket type to fasten bolts. It can be merged with other seismic force-resisting systems. To verify the seismic performance of the proposed system, a cyclic loading test was conducted, and the rigidly connected joint performance and integrated behavior at the joint of modular units were investigated. From the experimental results, the maximum resisting force of the proposed connection exceeded the theoretical parameters, indicating that a rigid joint structural performance could be secured.
This study presents a comprehensive analysis of the costs and benefits of the two main construction methods in the prefabricated homes category: panelized and modular. The main goal is to provide a framework of the implications and tradeoffs of both construction methods for single family homes, as well as determine which is more cost effective. The methodology consists of a qualitative analysis that includes the overview of the benefits of each construction method over the other, and quantitative analysis which compares the cost of the finished homes per square foot to determine which one is more cost effective. Both analyses are conducted by evaluating two case studies of single family homes with similar characteristics, one built with panels and the other with modules. The benefits identified for panelized homes have to do with transportation, equipment and machinery, and insulation technology; on the other hand, the benefits for modular homes are related to quality control, on-site work and trades. The quantitative results showed that the modular construction method is only marginally more cost effective than the panelized construction method under the given circumstances. As a second part of the quantitative analysis, the panel case study was calculated as if it would be built with modules, and the results of both analyses were consistent, but both with the same limitations. Through the proposed method, it is possible to evaluate the cost effectiveness of the two construction methods for single family prefabricated home projects which could serve as a valuable tool for decision making.
Contemporary seismic design is based on dissipating earthquake energy through significant inelastic deformations. This study aims at developing an understanding of the inelastic behavior of braced frames of modular steel buildings (MSBs) and assessing their seismic demands and capacities. Incremental dynamic analysis is performed on typical MSB frames. The analysis accounts for their unique detailing requirements. Maximum inter-story drift and peak global roof drift were adopted as critical response parameters. The study revealed significant global seismic capacity and a satisfactory performance at design intensity levels. High concentration of inelasticity due to limited redistribution of internal forces was observed.
Practitioners' views and opinions on the benefits and drawbacks of offsite technologies in the UK construction industry can vary widely, often depending upon their role or position. This research provides an indication of the opinions of the different sectors within the industry, including clients, designers, contractors and offsite suppliers, together with some predictions for the future growth of the offsite sector in the UK. A questionnaire survey of UK construction was conducted in order to target the three main construction industry sectors—suppliers/manufacturers, contractors and designers/clients. More than 80 questionnaires were completed and returned. The vast majority of practitioners within the industry are aware of the possibilities and potential of offsite, and most also understand the advantages and disadvantages of its use. The value of the UK offsite market was valued at £2.2bn in 2004 and the demand for offsite is clearly increasing, but it is not always clear in a project who is the main driver for its use. For the offsite market to develop further however, two main problems need to be addressed; the lack of transparent information for the decision makers in the construction process, particularly that relating to comparative costs, and the lack of available multi-skilled labour to work in the offsite factories.
Modular buildings are built using factory manufactured building units or modules that are transported and assembled on-site. Among the many different types of building units used, volumetric modules have the greatest potential to achieve complete building systems, where on-site work can be reduced to having only foundation, module assembly and the finishing of module-to-module interfaces. However, despite many reported benefits, the use of volumetric modules have some technical, logistical and regulatory issues that constrain its widespread application. The aims of this paper is to articulate two key technical issues that have been widely reported, namely, the lack of efficient structural systems for lateral load transfer and the lack of high-performance inter-module connectivity. Accordingly, a general overview regarding these two issues is presented that covers the behaviour of diaphragms in multi-story modular buildings and the essential characteristics required for inter-module connections. It is expected that inter-module connectivity should meet structural needs along with satisfying manufacturing and construction requirements. Brief descriptions of existing inter-module connecting systems that are available in both literature and the public domain including a critical review of those connections against the identified performance requirements are also presented. The outcomes of this paper are expected to assist in the future development and application of fully-modular superstructure construction systems for multi-story modular buildings.
The inter-module connection used for the assembly of prefinished modules is a unique key issue for modular steel buildings (MSBs). Previous types of inter-module connection require additional operation spaces and have conflicts with architecture decoration. To overcome these limitations, this study proposed an innovative rotary inter-module connection applied at the end of modular columns with corner fitting. The working mechanism of the rotary connection was introduced through a bending resistance test. Then, finite element analysis (FEA) and theoretical derivation were conducted to investigate the initial rotational stiffness obtained through the preceding test. In terms of the feature of double beams in MSBs and the results obtained, the influence of the stiffness ratio of double beams on the internal force distribution was investigated via FEA and theoretical calculation. Some recommendations for the design were also presented. Finally, the manner in which stiffness characteristics of the inter-module connection is considered accurately in the structural design was discussed and the conceptual design procedure of the inter-module connection was given accordingly. The results obtained could serve as a reference for the design of mid-rise MSBs.
Modular construction offers faster and safer manufacturing, better predictability to completion time, superior quality, less workers on site, less resource wastage, and a more environmentally friendly solution than the conventional construction process. Despite having several advantages of modular construction, the private sector still relies heavily on the traditional on-site construction method. To understand the scientific reason behind this situation, this paper critically reviews the recent developments, performances, challenges and future opportunities of modular buildings. Modular constructions are extensively used for low-rise buildings and further attracts strong interest for multi-storey building structures. Prefabricated modules demonstrated satisfactory performance under static, dynamic impact, cyclic, seismic, blast, fire and long-term sustained loading, and offer environmental, economic and social benefits. The acceptance and application of modular construction will further spread with the development of design guidelines, more skilled workers, addressing handing and transportation difficulties, and the development of novel interlocking connections between modules. Recently, composite materials demonstrated high potential to manufacture prefabricated building modules. In Australia, it is expected that modular construction will increase from the current stage of 3% to 5-10% by year 2030.
The popularity of steel modular construction is on the rise. This paper presents a new and innovative modular steel construction which uses state-of-the-art cast-steel connectors and hollow structural steel members. Structural behavior of a typical corner connection of this modular construction to be used in an assisted living facility was studied when the connection is subject to axial tension and axial compression loads. The study was completed using both experimental method and a numerical method. Six full-scale specimens were built and tested under axial compression and axial tension. It was found that this innovative modular connection satisfactorily carries the design loads. Based on the parametric study completed using finite element method, two significant design improvements are recommended. The cast-steel connector can be made 20% lighter without compromising the strength needed to satisfy the design loads. The locations of the connecting screws can be adjusted to achieve a higher stiffness and load carrying capacity of the connection when subjected to axial tension. This paper presents the new modular construction method in brief, the test method and test results, development of finite element model, and parametric study.
In this study, the seismic performance and inelastic behavior of joints were investigated using the bracket thickness, depth, and stiffener of the ceiling-bracket-type modular system as parameters. The performances of the joints were evaluated through a cyclic loading test and the nonlinear FEA. The initial stiffness, maximum flexural strength, failure mode at the ultimate stage, energy dissipation capacity, and inelastic behavior were analyzed, and it was determined whether the strong-column/weak-beam-type mechanism occurs at the joint. The results of the analysis were compared with those of the theoretical and FE models, respectively. For the comparison of the seismic performances, the flexural strength of the joint at the 0.04 and 0.05 rad inter-story drift ratios, which exceed the plastic moment, was investigated. From the comparison results, the standard specimen had a sufficient structural performance compared to the reference model, which was a welded joint. The joint was shown to be capable of maintaining a seismic performance higher than 80% of the plastic moment, and showed strain curves pointing to a strong column-weak beam behavior. In the joints, the initial stiffness was increased with a higher bracket thickness. In addition, the maximum flexural strength showed a large change in the loading direction due to the ceiling bracket. If the number of stiffeners is reduced, the joint will have both reduced initial stiffness and reduced maximum flexural strength. The bracket-type modular building was shown to be an effective and dependable modular system for resisting seismic loads, and the energy dissipation capacity of the standard specimen was shown to be higher than those of the other modular joints
Modular construction is an off-site construction technique. In this method, structural volumetric modular components are produced in a factory and assembled on-site to form a larger, permanent building. Typical vertical connections of modular steel buildings (MSBs) are provided by on-site welding. Welding may interfere with the finishing of the modules and also when several modules are placed together at a given floor level complete access for welding is compromised. As an alternative to on-site welding, the present paper proposes a new vertical post-tensioned (PT) connection for MSBs. This connection is comprised of a post-tensioned threaded rod installed inside hollow structural sections (HSS) columns and a steel box placed between two modules. In order to evaluate the general and the seismic performance of the proposed connection, eight quasi-static cyclic loading tests were performed in T-shaped subassemblies. A combination of three different steel boxes and three initial post-tensioning loads levels were considered. Additionally, two quasi-static cyclic loading tests were performed using standard welded connections. No local buckling was observed in any of the specimens and no welding fractures occurred up to 3% drift demand. Results indicated that in comparison to the welded connection the proposed PT connection have similar lateral stiffness and strain distribution, and a higher cumulative energy dissipation capability. Therefore, the proposed connection has the potential to eliminate on-site welding in the assembly of the modules while providing the lateral resistance required.
In modular steel building (MSB) built by unit-prefabricated on-site assembled construction method, connections are critical parts that can strongly influence the overall structural stability and robustness of the MSB. Previous MSB connections mainly use intermediate connecting plates, which may pose practical difficulties to certain modular arrangements or installations. Thus, this paper proposed an innovative MSB connection design with an intermediate plug-in device and a beam-to-beam bolt system as the horizontal and vertical connections, respectively. This connection design can ensure convenient installation, eliminating on-site welding. Two static uniaxial loading tests and four quasi-static cyclic loading tests were conducted on the T-shaped MSB connection to explore its load transfer capacity and aseismic behavior. Results showed that gaps would form between the upper and the lower columns because of its two-unit-joint structure. This gap can influence the deformation patterns and bending demand distributions in each unit joint. The weld quality in the unit joints was critical to ensure overall safety. Stiffeners can effectively strengthen the stiffness and load-bearing capacity. The deformation capacity of the connection was significantly influenced by the stiffness of floor beam–column joint and ceiling beam–column joint as well as the relative magnitudes between them.
In modular steel buildings, traditional architectures are separated into prefabricated room-sized volumetric units that are manufactured offsite and installed onsite. The connections between the modules are important for load transfer. Conventional inter-module connections mainly use direct plates and connect them using bolts; however, this may prove problematic for the inner connecting regions. A new type of design with beam-to-beam bolted connections is proposed in this paper; this design provides easy working access without being affected by the structural members. The static performance, hysteretic performance, skeleton curves, ductile performance, energy dissipation capacity, and stiffness degradation patterns of the joints are obtained by experiments and finite element analyses. The results showed that because of the construction between two unit joints, gaps would be formed between the upper and bottom columns, and this gap can influence the deformation patterns and distribution of bending loads at each unit joint. The weld quality at the unit joints is critical to ensure overall safety. Stiffeners can effectively increase the stiffness and load bearing capacity, but may reduce ductility performance. The deforming ability of the connection is also closely influenced by the stiffness of the floor beam column joint and ceiling beam column joint and their relative intermediate magnitudes.
Modular construction is widely used in Europe for multi-story residential buildings. A review of modular technologies is presented, which shows how the basic cellular approach in modular construction may be applied to a wide range of building forms and heights. Case studies on 12-, 17-, and 25-story modular buildings give design and constructional information for these relatively tall buildings. The case studies also show how the structural action of modular systems affects the architectural design concept of the building. The combination of modules with steel or concrete frames increases the range of design opportunities, particularly for mixed-use commercial and residential buildings. An overview of the sustainability benefits and economics of modular construction is presented based on these case studies.
The robustness or structural integrity of light steel framing and modular constructions is important because these are relatively new structural forms, in which the components have different forms of inter-connectivity in comparison with primary steel frames. There is an increased need to understand the sensitivity of these forms of construction to so-called 'accidental actions', including terrorist threats. Various forms of construction using light steel and modular technologies are identified and their implications for robustness are reviewed. A series of stressed skin tests on modular constructions is presented. These show that modules are able to span as deep beams with one longitudinal support removed with minimal displacements, indicating that the torsional stiffness of the 'box' provides a high level of robustness. Removal of a corner support again demonstrates the role that torsional action of the box plays in redistributing loads away from damaged sections of a structure. For light steel framing, multiple interconnections provide robustness by tying action and alternative load paths in the event of one or more elements being severely damaged. For modular construction, a scenario-based approach is required in which modules are selectively removed and the horizontal and vertical forces in the connections between the modules can be calculated explicitly.
Several studies have shown that the lateral response of concentrically-braced frames is dominated by the inelastic behavior of the bracing members. However, the overall performance of the entire frame depends on the frame configuration including its connections. In this study, the hysteretic characteristics of modular steel-braced frames under reversed cyclic loading are evaluated. The design and construction of the test specimen accounted for the unique detailing requirements of these frames. A regular concentrically-braced frame with similar physical characteristics was also tested for comparison. Both test specimens consisted of a one-storey X-braced system with tubular brace cross-section. This paper describes the behavior characteristics and provides a detailed comparison of the two systems to assess the strength, stiffness, inelastic force and deformation, and energy dissipation characteristics of the modular system. An analytical model capable of capturing the effect of the system’s unique detailing requirements is proposed and validated using the test results.