No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Ductile connections to improve structural robustness in fire
Abstract
The ductility of connections is a key property in preventing the brittle failure and subsequent progressive collapse of steel-framed structures in fire conditions. Conventional connection types have insufficient ductility to accommodate the deformations generated by the connected beams as their temperatures rise, or to withstand the forces to which they are subjected. This paper aims to investigate the mechanical performance of a new type of connection proposed to meet the ductility demand created by long-span steel beams in fire conditions. This novel connection consists of two identical parts, each of which includes a fin-plate, an endplate and a semi-cylindrical section. Analytical component models have been developed and validated, based on which a component-based model is proposed. A simple Abaqus frame model with these novel connections has been created to assess the structural performance of the novel connection under realistic conditions.
... Based on the FEM model, the characteristics failure mode, midspan deflection of the beam, axial force variation of the beam, and plastic strain are the key aspects considered. In the second part, presented in [34] is employed to verify the FE model. In the third part, detailed in section 4, finite element modeling of the proposed connection is conducted to assess the nonlinear cyclic response, the energy dissipated in the connection by plastic deformation and hysteresis curves. ...
... To simulate the effect of fire loading on tubular connections, ABAQUS software was used to run a Nonlinear FE model. The proposed subassembly, geometry, material, boundary conditions, and heating were modeled precisely the same as those used in the reference test [34,35] in order to explore the effects of dimensional parameters on the fire resistance and ductility of tube connections. To save computational expense, only half of the beam was modeled, and a symmetric boundary condition was implemented at the beam midspan. ...
... The experimental and numerical results of Wald et al. [38], Elsawaf et al. [13] and novel connection in the fire incident reported by Liu et al. [34,35] were utilized to validate the FE model. In this paper, only the result of ductile connection in long-span beam [34,35] and reverse channel connection in short-span beam [13] are presented. ...
... However, traditional connection types lack axial ductility to accommodate the net expansion of beams during early heating and the net contraction of beams during the high-temperature "catenary" stage. In order to prevent the brittle failure of connections and improve the robustness of steel framed structures in fire, a novel connection with high axial deformability has been proposed by the authors [1][2][3][4][5][6][7][8][9]. A component-based model of the bare-steel ductile connection has been developed by the authors and incorporated into the software Vulcan [3][4][5]. ...
... So far, the research on the fire performance of composite connections is still very limited. The performance of the ductile connection in bare-steel structures have already been well studied by the authors in previous papers [1][2][3][4][5][6][7][8]. It is necessary to study the high-temperature behaviour of the ductile connection in composite structures to verify whether the deformability of the ductile connection is still useful when used with composite floors. ...
... In order to improve the ductility of connections and enhance the robustness of structures in fire, a novel axially and rotationally ductile connection has been proposed by the authors [1][2][3][4][5][6]. This ductile connection consists of two identical parts, which can be manufactured by bending a steel plate. ...
Connections are vital to the survival of steel and composite framed structures in fire. To prevent brittle failure of connections at elevated temperatures, a novel connection with high ductility has been proposed previously. In this paper, the fire performance of this ductile connection in composite frames is investigated. In order to consider the influence of the out-of-plane structural behaviour, the 3-D models of a fire compartment of a typical composite framed structure with different connection types, including the ductile connection, idealised rigid and pinned connections, as well as commonly used end-plate and web-cleat connections have been built using Vulcan to compare the performance of ductile connection with other connection types. Comparison results show that the proposed ductile connection can provide additional ductility within composite frame to accommodate the axial deformation of connected beam at high temperatures. To further save computational costs, the 3-D composite frame compartment model has been reduced to a quarter of its original size by using symmetric boundaries. The influence of unconnected length between the slab and beam on the connection performance has also been investigated. It is found that the relative beam end slip is affected by the unconnected length. However, due to the inherent mechanical properties of the ductile connection, the influence of unconnected length on the force of the ductile connection is negligible, which can also reflect the deformation capacity of ductile connection.
... The existing commonly-used connection types lack the ductility to accommodate the axial deformation of connected beams in fire, which could trigger the brittle facture failure of connections. In order to improve the ductility of connections and enhance the robustness of structures in fire, a novel ductile connection has been proposed by the authors [8,9]. Two component-based models of the novel connection have been developed and compared [10]. ...
... The novel ductile connection proposed by the authors [8,9] consists of two identical parts which can be manufactured by deforming a steel plate, and each part includes a fin-plate bolted to the beam web, a web-cleat bolted to the column flange, and a semi-cylindrical section between the fin-plate and web-cleat, as shown in Figure 1. ...
... The semi-cylindrical section is the key component in providing additional ductility by allowing the fin-plate to move towards and away from the web-cleat. Therefore, the radius of the semi-cylindrical section should be determined according to the axial ductility demands of the connected beam, which can be evaluated as detailed in [8,9]. The fin-plate and web-cleat of the novel connection can be designed according to EC3 [6]. ...
The component‐based model of a novel ductile connection has been incorporated into the software Vulcan in order to facilitate global frame analysis within a performance‐based structural fire engineering design process. This paper reports on the validation and verification of the model, as well as the applications of the model in order to investigate the effects of the ductile connections on the structural responses of long‐span frames at high temperature. Firstly, three single‐beam models with the novel connections at both ends, connected to rigid supports, are used to verify that the component‐based connection model has been correctly incorporated into Vulcan, via comparisons against detailed finite element modelling with Abaqus. The structural performance in fire of long‐span frames with the novel ductile connections has been compared with the performance of the same frames with idealized rigid, idealized pinned and conventional end‐plate connections, initially using a limited sub‐frame model. Results show that, compared with the above mentioned three connection types, the ductile connection provides much higher axial and rotational ductilities to accommodate the deformations generated by the connected beams as their temperatures rise. As part of this process, these connections are instrumental in greatly reducing the axial forces to which the surrounding structure is subjected. Finally, parametric studies varying several key parameters have been carried out, in order to optimize the design of the ductile connection to enhance its performance subject to catenary action at very high temperature to prevent potential connection fracture and progressive collapse.
... Connection failures can also trigger the collapse of the supported slab, leading to the spread of fire into adjacent compartments. In order to provide the beam-column connection with high ductility, a novel connection has been proposed by the authors in the previous papers [3][4][5]. This novel connection can be considered as an angle-cleat with greatly enhanced ductility. ...
... These were validated against both Abaqus simulations and experiments [3]. A structural sub-frame model, analysed using Abaqus, was used to compare the performance of the novel connection with that of the normal webcleat connection [4]. The results showed that the axial force generated in the beam with the novel connections was significantly reduced due to the high axial ductility created. ...
... The novel ductile connection proposed by the authors in previous papers [3][4][5] is shown in Figure 1. It consists of two identical parts, each of which includes a fin-plate, a semi-cylindrical section and a web-cleat. ...
The component-based model of a novel connection, which is designed to accommodate the high ductility demand of long-span steel beams in fire conditions, has been incorporated into the finite element software Vulcan. A single beam with the novel connections connecting it to rigid supports at both ends is first used to verify that the component-based model has been correctly incorporated into Vulcan, by comparing its results with those from detailed finite element models using the general-purpose package Abaqus. The performance of the novel connection has been compared with that of conventional connection types, including ideally rigid and pinned connections, endplate and web-cleat connections, using a sub-frame model. Results show that, compared with other connection types, the novel connection provides much higher axial and rotational ductilities, to accommodate the deformations generated by the connected beam as its temperature rises. To optimize the performance of the novel connection under the tensile axial forces generated by the eventual catenary action of heated, unprotected beams at high temperatures, parametric studies have been carried out on the influence of four key parameters, including the temperature of the connection, the inner radius of its semi-cylindrical section, the plate thickness and the bolt spacing. It is found that it is possible to optimize connection thickness, protection level, and inner radius of the semicylindrical section in order to delay the occurrence of bolt pull-out failure, and thus enhance a beam’s ultimate failure temperature. Finally, the combined static-dynamic solver of Vulcan is used to simulate the progressive collapse of a three-storey, three-bay frame with these novel connections. This progressive collapse simulation emphasizes the importance of connections for the survival of the entire structure in a fire event.
... The proposed subassembly, material, boundary conditions, and heating were modeled precisely the same as those used in the reference test [29,30] to explore the effects of dimensional parameters on the fire resistance and ductility of cylindrical RBS connections. Only half of the beam was modeled to save computational expense, and a symmetric boundary condition was implemented at the beam midspan. ...
... The experimental and numerical results of Wang et al. [13] and the novel connection made in the fire incident reported by Liu et al. [29,30] are utilized to validate the FE model. In this paper, only the results of reverse channel connection in short-span beam [13] and web cleat connection [33] are presented. ...
... Current commonly-used connection types lack the axial and rotational ductilities required to accommodate the deformation of a connected beam under fire conditions. In order to improve the performance of connections and enhance the robustness of steel-framed or composite structures in fire, a novel ductile connection has been proposed by the authors [16][17][18][19]. A suitable component-based model of the bare-steel ductile connection has been developed and tested by the authors [18] against detailed Abaqus simulations. ...
... To meet the ductility demand of the beam in fire, a novel ductile connection has been proposed by the authors [16][17][18][19]. This novel connection consists of two identical opposed parts. ...
To enhance the robustness of steel-framed structures in fire, a novel, axially ductile connection has previously been proposed. In this paper its performance is investigated when it is used to connect composite beams to steel columns in composite steel-concrete construction. The ductile connection is designed to satisfy the ductility demands of the composite beam at elevated temperatures. A reinforcement component has been added to the bare-steel ductile connection model to establish a component-based model of the composite ductile connection. The connection model has been incorporated into the software Vulcan, and is validated against detailed Abaqus FE models using solid elements. Results show that the proposed component-based model can efficiently represent the behaviour of the connection given by the detailed Abaqus simulations. Parametric studies using Vulcan have been carried out, varying three parameters; the connection thickness, the semi-cylindrical section radius, and the density of longitudinal reinforcing bars. Finally, a 2-D Abaqus composite frame model has been created to investigate the influence of shear studs on the behaviour of the composite ductile connections under different stud spacings.
... To improve the high-temperature performance of connections, a novel axially and rotationally ductile connection with high deformability has been proposed by the authors [25][26][27][28][29][30][31][32][33][34][35]. The configuration of this ductile connection will be introduced in detail later in this paper. ...
Connections are the most vulnerable parts of a structure under fire conditions. A novel steel connection with high axial and rotational ductility has been proposed with the objective to improve the performance of steel-framed buildings in fire. Analytical model has been developed to determine the axial displacement of the top and bottom flanges of the beam end at high temperatures. A series of sub-frame models with this ductile connection have been built using Abaqus to study the influence of the characteristics of the connection part between the fin-plate part and face-plate part on the overall connection behaviour. The current critical failure mode of the ductile connection is bolt pull-out from the face-plate zone, and the tensile deformation capacity of the connection is not fully utilized. Therefore, measures to improve the bolt pull-out failure mode of the connection have been tested using the Abaqus sub-frame models, including adding a strengthening plate to the face-plate part of the connection and increasing the connection plate thickness. The simulation results show that the bearing failure of the beam web will become another critical failure mode of the connection, once the bolt pull-out failure is eliminated. To further optimize the high-temperature performance of the connection, the Abaqus steel frame models have also been used to test some measures to delay the occurrence of the beam web bearing failure, including adding strengthening plates to the part of the beam web in contact with the connection, and improving the material properties of the part of the beam web around the bolt holes at high temperatures.
... Conventional commonly-used connection types lack axial and rotational deformability to accommodate the large deformation that a connected beam would experience in a fire accident. In order to improve the fire performance of connections, a novel connection with excellent axial and rotational ductility has been proposed by the authors (Liu et al., 2019a(Liu et al., , 2019b(Liu et al., , 2020a(Liu et al., , 2020b(Liu et al., , 2020c(Liu et al., , 2021a(Liu et al., , 2021b(Liu et al., , 2021c. ...
Purpose
In order to improve the robustness of bare-steel and composite structures in fire, a novel axially and rotationally ductile connection has been proposed in this paper.
Design/methodology/approach
The component-based models of the bare-steel ductile connection and composite ductile connection have been proposed and incorporated into the software Vulcan to facilitate global frame analysis for performance-based structural fire engineering design. These component-based models are validated against detailed Abaqus FE models and experiments. A series of 2-D bare-steel frame models and 3-D composite frame models with ductile connections, idealised rigid and pinned connections, have been created using Vulcan to compare the fire performance of ductile connection with other connection types in bare-steel and composite structures.
Findings
The comparison results show that the proposed ductile connection can provide excellent ductility to accommodate the axial deformation of connected beam under fire conditions, thus reducing the axial forces generated in the connection and potentially preventing the premature brittle failure of the connection.
Originality/value
Compared with conventional connection types, the proposed ductile connection exhibits considerable deformability, and can potentially enhance the robustness of structures in fire.
... Connection failures may lead to the detachment of connected beams, the collapse of slabs, the buckling of columns and even the progressive collapse of the entire building. In order to enhance the robustness of structures in fire and prevent brittle failures of connections, a novel axially ductile connection has been proposed by the authors (Liu et al., 2019a(Liu et al., , 2019b(Liu et al., , 2020a(Liu et al., , 2020b(Liu et al., , 2020c(Liu et al., , 2021. The performance of the ductile connection within bare-steel frames in fire has already been well studied by the authors. ...
A novel axially and rotationally ductile connection has previously been proposed by the authors to prevent brittle failures of connections in fire. The study is now extended to investigation of the fire performance of the ductile connection in composite structures, particularly using a 3-dimensional model to consider the contribution of out-of-plane structural elements to the behaviour of the connection and the behaviour of the frame as a whole. In this paper, the design and the component-based model of the ductile connection have been briefly introduced. A composite frame has been designed according to the typical frame used in the Cardington full-scale fire tests. Three 3-dimensional composite frame models with different types of connections have been built using the software Vulcan to compare the performance of the ductile connection in fire with ideally rigid and pinned connections. Finally, 2-D models have been built to simulate the central and edge secondary beams of the composite frame to make a comparison between 2-D modelling and 3-D modelling.
... However, current commonly-used connection types lack the push-pull ductility required to accommodate either the compressive effects due to the constraint of thermal expansion of connected beams in the early stages of a fire, or the tensile effects caused by the catenary action of the connected beams when most of the steel strength has been lost at high temperatures. In order to improve the performance of connections and enhance the robustness of structures in fire, a novel ductile connection has been proposed by the authors [2][3][4][5][6]. Additional axial ductility is provided to a connection which is essentially a web-cleat by the inclusion of a semi-cylindrical zone in the connection leg which is attached to the beam web. ...
In order to improve the performance of connections and enhance the robustness of structures in fire, a novel, axially ductile connection has been proposed. The component-based models of bare-steel ductile
connection and composite ductile connection have been proposed, and incorporated into the software Vulcan to facilitate global frame analysis. These component-based models are validated against detailed Abaqus FE models. A series of 2-D bare-steel frame models and composite frame models with ductile connections, rigid connections, and pinned connections, have been created using Vulcan to compare the fire performance of ductile connection with other connection types in bare-steel and composite structures.
A component-based model for fin-plate connections has been developed to study the robustness of simple beam-to-column connections at elevated temperatures. The key aspect of this component method is the characterisation of the force-displacement properties of each active component at any temperature, represented by a non-linear "spring". The prescribed temperature-dependent characteristics of any given bolt row are governed by the failure mechanism of the weakest component, based on experimental and analytical findings. A major additional complication involves force reversal in components, which may occur because of temperature change, without any physical reversal of displacement. The Masing Rule has been adapted to incorporate this effect for particular force directions. To account for the bolt slip phases, force transitions between tension and compression take place only when positive contact between a bolt and the edge of its bolt hole is re-established. The results of high-temperature tests on connections have been used to substantiate the developed component model. The component-based connection model has also been used to study joint behaviour in structural sub-frame analyses. This approach will enable more valid performance-based assessment of the overall responses of connections, including their robustness, in design fire scenarios.
The companion paper has reported the results from a test programme in which web cleat connections were subjected to various combinations of shear, tying and moment actions at elevated temperatures. These tests showed that web cleat connections have very good tying resistance and rotational capacity, mainly due to the large deformation of which the web cleats are capable. In this paper a mechanical model is developed to predict the behaviour of web cleats subjected to tying forces. This model considers the formation of four plastic hinges on each angle and the effect of the angles opening in enhancing their resistance. It is capable of representing the action of the angles in component-based models for web cleat connections, in which algorithms for other components, including bolts in tension, bolts in double shear and holes in bearing, are already available. Failure criteria determined from the tests have been introduced into the models for components such as web cleats and bolts in double shear. This enables the component-based assembly to predict the occurrence and the sequence of connection failure. The behaviour of the connection predicted by the component-based model shows good correlation with the test results, which indicates that the developed model can be adopted in structural frame analysis to consider connection failure.
World Trade Center Building performance study: Data collection, preliminary observations, and recommendations, Federal Emergency Management Agency
- T Mcallister
- G Corley
MCALLISTER, T. & CORLEY, G. 2002. World Trade Center Building performance study: Data collection,
preliminary observations, and recommendations, Federal Emergency Management Agency.
Fire safe design: A new approach to multistorey steel-framed buildings
- G M Newman
- J T Robinson
- C G Bailey
NEWMAN, G. M., ROBINSON, J. T. & BAILEY, C. G. 2000. Fire safe design: A new approach to multistorey steel-framed buildings, Steel Construction Institute.
Numerical modelling for progressive collapse of steel framed structures in fire
- R R Sun
SUN, R. R. 2012. Numerical modelling for progressive collapse of steel framed structures in fire. University
of Sheffield, UK.
Mechanical properties of grade 8.8 bolts at elevated temperatures
- Y Theodorou
THEODOROU, Y. 2001. Mechanical properties of grade 8.8 bolts at elevated temperatures. University of
Sheffield UK.