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Nonlinear simulation of RC structures using applied element method
Abstract
A new extension for the Applied Element Method (AEM) is introduced. Using this method, the structure is modeled as an assembly of distinct elements made by dividing the structural elements virtually. These elements are connected by distributed springs in both normal and tangential directions. This paper describes the applicability of the AEM for different fields of analysis and structure types and it deals with the formulations used for RC structures under monotonic loading. It is proved in this paper that the structural failure behavior including crack initiation and propagation can be simulated accurately with reasonable CPU time and without any use of complicated material models.
... Zhang and Zhao et al. [8] and [9] developed a simplified model for considering the contribution of floor slab on progressive collapse resistance of frames. The (AEM) was settled in 1995 as part of research studies, developed by [10]. However, only in 2000 the term of "Applied Element Method" was presented in a research paper [11]. ...
... However, the advantages of FEM compared to Discrete Element Methods (DEM) is that it is more accurate in the small displacement analysis. In order to overcome the DEM's problems, Tagel-Din and Meguro [10] created the Applied Element Method [11]. ELS also can be used in nonlinear dynamic analysis for low rise and high rise reinforced concrete buildings [12]. ...
... 10) shows the frame dimensions, height and position of the removal column. The columns and the beams cross sections were modeled as rectangle cross sections as shown inFigure (11-a). ...
... The importance of the outcome of this study will provide an overall idea of the behavior of the collapse of the different beam span lengths for either new or existing structure during the loss of one of its primary support. The case study is conducted using the Applied Element Method that adopts the discrete cracking concept [26], [27], and [28]. The material modeling is applied using complete non-linear constitute models for reinforced concrete. ...
... The Analysis Domain of Applied Element Method (AEM) and the Finite Element Method (FEM)[27]. ...
... Concrete and steel constitutive models adopted in AEM[27]. ...
Progressive collapse is defined as either partial or overall failure of the structure due to losing one of the main structural elements. In order to control this chain reaction, it is important to study the main structural elements behavior under column removal. Precast concrete structures become widely used recently due to the quality control assurance, economical aspects, and time-saving construction. Due to this many researchers studied the precast concrete structures behavior under earthquake loading, observing the failure patterns, weak points, and how to overcome all those parameters, however, regarding progressive collapse , Precast concrete structures need intensive researches to cover all the parameters that will affect the structure's behavior due to accidental loading. One of the main parameters that still ambiguous is the Precast beam span lengths and its behavior on the overall structure When subjected to progressive collapse. In this paper, the influence of different span lengths of precast beams is studied under different column removal scenarios. A precast concrete structure case study is adopted and designed according to Precast/Prestressed Concrete Institute and ACI 318-14 and a multiple 3D models, for different span lengths, are modeled in Extreme Loading of Structures software based on the Applied Element Method. Non-linear dynamic time-dependent analysis is conducted on two case studies; bare frame structure without any slab contribution (Case1), and full structure with slab contribution (Case2). Column removal scenarios are applied according to the UFC regulations, partial collapse took place in case1 while case 2 showed high resistance to progressive collapse. Observations are reported in terms of failure cause for case 1 and the resisting mechanism that took place in case 2. Rotational ductility redistributed applied loads for beams and columns are obtained for case 2. A comparison took place between the rotations obtained in the case study and the rotation limits specified by the UFC and found that the system is satisfying the UFC limits, and no additional consideration needs to be done in resisting progressive collapse.
... When assessing the resistance of reinforced concrete frame-tie frames of buildings and structures to progressive collapse, taking into account the possibility of local destruction in them, in any section of the bearing system, researchers and design engineers mainly use a spatial rod, plate, or plate-rod finite element (FE) models such as considered by Gudmundsson and Izzuddin (2010), Izzuddin et al. (2008), Kolchunov et al. (2019); Kolchunov and Savin (2018), Li et al. (2016), Marjanishvili and Agnew (2006), Shan, Petrone and Kunnath (2019), Wang et al. (2014) or similar models of the Applied Element Method investigated by Alanani, Ehab and Salem (2020), Tagel-Din and Meguro (2000). For a more detailed analysis of the features of deformation and the destruction of nodal joints, substructures, fragments of frames of buildings and structures under special influences caused by structural rearrangements of their bearing systems due to the sudden removal of one of the elements, using the decomposition method, such elements are separated from the spatial design model of the entire structure. ...
... After that, the dynamic effect quickly decays. These results of the finite element analysis confirm its limited capabilities for the post-critical structural behavior simulation previously noted by Tagel-Din H and Meguro K (2000). Besides, the nonlinear model of reinforcing steel adopted in Section 3.2 did not take into account the hardening of the steel and the possibility of the stress reaching its ultimate values. ...
The purpose of this study is to create a universal computational model of a plane-stressed joint element, which could be implemented as a special finite element of the beam-column subassembly integrated into the FEA procedure to improve its accuracy. The combination both of the finite element method and the finite difference method has been accepted to simulate the structural behavior of monolithic reinforced concrete joints of building frames. The finite difference method is used directly for analysis the stress-strain state of a 2D stressed member of a monolithic joint, and the FEM is used for preliminary obtaining the conditions on the contour of this plane stressed member. The proposed model allows considering the discrete reinforcement, as well as the disruption of the adhesion of the reinforcing bars to concrete matrix along the contact surface. For the purposes of implementing the model, an algorithm for the stress-strain state analysis of the beam-column joint is proposed. An example of calculating an experimental frame unit based on the proposed approach is considered.
... e Extreme Loading for Structures (ELS) program, developed by ASI-2018 [11], is based on the AEM, which was initially developed by Tagel-Din and Meguro [12,13] at the University of Tokyo in 1998 to solve problems related to two-dimensional plane stresses. It was later expanded to solve three-dimensional problems. ...
... e total number of elements used for monolithic, continuous, and simple bridges was 10,000, 13,800, and 13,200, respectively. e AEM mesh used was accurate enough during the elastic region and in the small deformation range of the inelastic region [12,13]. ...
Most of the recent studies focus on the progressive collapse of ordinary structures due to gravity and blast loads. A few focus on studying progressive collapse due to seismic actions, especially of bridge structures. The past major earthquakes have shown that it is possible to develop improved earthquake-resistant design techniques for new bridges if the process of damage from initial failure to ultimate collapse and its effects on structural failure mechanisms could be analyzed and monitored. This paper presents a simulation and analysis of bridge progressive collapse behavior during seismic actions using the Applied Element Method (AEM) which can take into account the separation of structural components resulted from fracture failure and falling debris contact or impact forces. Simple, continuous, and monolithic bridges’ superstructures were numerically analyzed under the influence of the severe ground motions not considering the live loads. The parameters studied were the superstructure redundancy and the effect of severe ground motion such as Kobe, Chi-Chi, and Northridge ground motions on different bridge structural systems. The effect of reducing the reinforcement ratio on the collapse behavior of RC box girders and the variation of columns height were also studied. The results showed that monolithic bridge models with reduced reinforcement to the minimum reinforcement according to ECP 203/2018 showed a collapse behavior under the effect of severe seismic ground motions. However, changing the bridge structural system from monolithic to continuous or simple on bearing bridge models could prevent the bridge models from collapse.
... Recently, due to the rapid development of both computer hardware and software, many numerical methods have been introduced to simulate the behavior of structures under hazard load conditions. Among these numerical methods, the applied element method (AEM) (Tagel-Din and Meguro 2000;Meguro and Tagel-Din 2001) has gained increasing interest because of the wide range of applications. Despite its accuracy and reliability, the drawback in this method is the large solving time because of the large number of elements in modeling a structure. ...
... The redistribution of spring forces is important for following the proper crack propagation. More details can be found elsewhere (Tagel-Din and Meguro 2000;El-Kholy et al. 2012). The second failure criteria for steel material is based on the stress-strain relationship. ...
The current study introduces an extension for the multilayered improved applied element method to provide a tool for bonded prestressed concrete structures. In the new extension, a new layer has been implemented to represent the behavior of the prestressing tendon and the transfer of the stresses between the tendon and concrete. Furthermore, an initial load step has been developed to consider the effect of prestressing. During this load step, an initial strain is produced in the tendon layer to represent the effective prestressing. Both material inelasticity and geometric nonlinearity have been considered in the proposed model. Several verification examples under monotonic and cyclic loading are presented to examine the reliability of the model and identifies its limitations. Comparison between the analytical and experimental results has shown good agreement, highlighting the reliability of the new extension.
... In this model, the non-orthogonal crack-to-crack interaction is treated using the active crack method under cyclic stresses, and four-directional cracking is represented within a control volume for which the space-averaged stress-strain relationship is defined. Other approaches to simulate seismic-induced damage and collapse include the use of multilayer elements and damage mechanics modeling of concrete behavior [12], the applied element method [13], and adaptively Shifted Integration (ASI) techniques [14]. However, past experiences of extreme damages in RC structures have shown scenarios of damage occurring at mesoscale volumes. ...
A two-story rigid-frame reinforced-concrete (RC) abutment of a viaduct that is part of the Tohoku Shinkansen, a high-speed train line, was severely damaged during the 2022 Fukushima Prefecture-Oki earthquake, Japan. The lower parts of the abutment piers suffered extensive damage, causing a vertical settlement of the abutment. An extensive study using three-dimensional nonlinear Finite Element (FE) analysis was conducted to understand the structural damage process and mechanism during the earthquake. The objectives of this study is to clarify the structural behavior after shear failure during the earthquake, to simulate the observed damage pattern and to confirm the effectiveness of quick and early recovery works in practice. In the FE analysis, a concrete-graveling transient model was adopted to simulate the large-scale pier damage. The model considers the transition of the shear resistance mechanism from aggregate interlock to Coulomb friction as the graveling formation progresses along localized shear bands in the concrete crack zone. In addition, a cyclic path-dependent enhanced buckling model of the reinforcement bars was adopted to simulate the large deformation and buckling of the reinforcement bars. Simulations demonstrated that, under extensive seismic excitation, the lower piers were subjected to large axial forces and gradually bulged out accompanying the shear failure mode. This damage mechanism agrees well with the observation of the damaged pier of the abutments. Retrofitting work to quickly restore the early service of railway infrastructure was conducted by jacking-up beams and upper piers of abutments to bring the structure back to the original position and repair the damaged piers. The effectiveness of the structural restoration was investigated using FE simulations by considering the pre-existing damage condition and jacking-up sequence.
... It is important to note that the classification shown in Fig. 1 is mostly relevant for strategies based on the finite element method (FEM), which is the most widely used approach for performing simulations in the field of structural engineering. Nevertheless, it should be mentioned that other strategies (employing 3D-solid elements) can be used to simulate progressive collapse, notably the discrete element method (DEM) [20][21][22] and the applied element method (AEM) [23][24][25][26][27]. ...
Several structural robustness requirements have been included in building codes over the past two decades. These mainly include measures to prevent collapse after an initial component failure by ensuring a minimum level of continuity within the structural system so that loads supported by the failed component can be redistributed to the rest of the structural system. However, there is still a general lack of consensus on how to evaluate the effectiveness of these measures. The present study proposes a practical methodology to evaluate the structural robustness of RC building structures by combining an efficient modelling strategy and suitable robustness indexes. The proposed computational modelling strategy for RC buildings accounts for relevant dynamic and nonlinear phenomena, including compressive arching, catenary action, and membrane effects. This strategy can be implemented at a reasonable computational expense in widely used commercial structural analysis software and has been validated by comparisons to selected experimental tests from the literature. The modelling strategy is then employed to compute four different robustness indexes proposed in the literature for three hypothetical building designs, allowing the indexes to be systematically compared. It was found that evaluating a system using multiple robustness indexes can provide a more holistic view of system performance compared to relying solely on a single index. Ultimately, the potential usefulness of the proposed methodology is demonstrated through two practical applications involving the estimation of component damage levels and the evaluation of different design and retrofitting solutions. Such a methodology can be useful for practising engineers to optimise the design of new buildings or to support decisions on the assessment and retrofitting of existing ones.
... For the identification of the required scenario, several nonlinear dynamic analyses were performed concerning different scenarios of column removal of the sample building. The Applied Element Method [25] was used to perform the numerical simulations, given its demonstrated ability to predict structural responses during different stages of collapse [7,26,27]. Simulations showed that the simultaneous removal of two interior columns was an initial damage scenario severe enough to generate a propagation of failure until total structural collapse (Figure 3a). On the other hand, scenarios concerning the removal of only one column did not generate any collapse propagation (Figure 3b), also proving the effectiveness of the strategy adopted in the initial robustness design phase. ...
Ensuring suitable robustness and resilience in building construction is a major priority for contemporary society. The study of past structural collapses resulting in disastrous consequences has revealed shortcomings in current robustness regulations. Particularly in cases of large initial damage, the widespread practice of ensuring extensive continuity may prove counterproductive, contributing to the propagation of failures rather than limiting their extent. This research presents the principles of an innovative design approach aimed at arresting the propagation of structural collapse through the segmentation of buildings. A performance-based framework is here proposed to guide designers in preventive structural planning for improved resilience. A cost-benefit analysis, a key tool to quantify the benefit of this philosophy , is introduced in order to support design decisions in accordance with required performance objectives.
... The AEM is a rigid body and spring modelling technique that uses zero-thickness joint interfaces in an implicit time integration scheme developed two decades ago [146,147,221]. Another major difference with respect to DEM, in addition to the fact that deformable bodies are not allowed, is the location of contact points. ...
In the last few decades, discontinuum (or discrete, discontinuous) numerical modelling strategies-i.e. those capable of representing the motion of multiple, intersecting discontinuities explicitly-have become increasingly popular for the structural and seismic assessment of unreinforced masonry (URM) structures. The automatic recognition of new contact points and prediction of large deformations up to complete separation are unique features of discontinuum-based models, making them particularly suitable for unit-by-unit simulations. The adaptation of discrete computational models, primarily used for analyzing rock mechanics and geomechanics problems, to the conservation, structural and earthquake engineering evaluation of URM assemblies is still ongoing, and recent advances in computer-aided technologies are accelerating significantly their adoption. Researchers have now developed fracture energy-based contact models tailored to unreinforced masonry mechanics , explored discontinuum analysis from the mortar joint-to the 3D building-level, combined discrete modelling strategies with analytical or continuum approaches, integrated the latest structural health monitoring and image-based developments into discontinuum-based analysis framework. Concurrently, new and still unsolved issues have also arisen, including the selection of appropriate damping schemes, degree of idealization and discretization strategies, identification of appropriate lab or onsite tests to infer meaningful equivalent mechanical input parameters. This paper offers to the research and industry communities an updated critical appraisal and practical guidelines on the use of discontinuum-based structural and seismic assessment strategies for URM structures, providing opportunities to uncover future key research paths. First, masonry mechanics and discontinuum-based idealization options are discussed by considering micro-, meso-and macro-scale modelling strategies. Pragmatic suggestions are provided to select appropriate input parameters essential to model masonry composite and its constituents at different scales. Then, discontinuum approaches are classified based on their formulation, focusing on the Distinct Element Method (DEM), Applied Element Method (AEM) and Non-Smooth Contact Dynamics (NSCD), and an overview of primary differences, capabilities, pros and cons are thoroughly discussed. Finally, previous discontinuum-based analyses of URM small-scale specimens, isolated planar or curved components, assemblies or complex structures are critically reviewed and compared in terms of adopted strategies and relevant outcomes. This paper presents to new and experienced analysts an in-depth summary of what modern discontinuum-based tools can provide to the structural and earthquake engineering fields, practical guidelines on implementing robust and meaningful modelling strategies at various scales, and potential future research directions.
... Therefore, it is essential to generate simple numerical models capable of predicting seismic behavior under various types of loading. The applied element method (AEM) [22], [23] is used to model the studied RM buildings. The AEM is a pioneering modeling technique that adopts the smeared and discrete cracking concept. ...
Many experimental and numerical studies have investigated the improvement in the seismic performance of reinforced masonry (RM) shear walls as a result of adding confined end zones (i.e., boundary elements) to rectangular shear walls. Moreover, the Canadian masonry design standard (CSA S304-14) introduced a ductile shear wall system and special seismic design provisions for masonry boundary elements. Furthermore, the National Building Code of Canada (NBCC 2015) permits the use of ductile shear walls as a seismic force-resisting system (SFRS) with height limits of up to 60 m and 40 m for moderate and high seismic regions, respectively. Therefore, as a continuous improvement in the seismic design of RM structures, this study assesses the seismic performance of reinforced masonry core walls built up of RM shear walls with boundary elements to act as the main SFRS in typical RM buildings. The applied element method (AEM) implemented in the Extreme Loading for Structures (ELS) software was utilized to simulate the seismic behavior of RM shear walls having different cross-sectional configurations and design parameters. Moreover, to evaluate the seismic performance of reinforced masonry core walls with boundary elements (RMCW+BEs). The results showed that RMCW+BEs can be used as an SFRS in RM structures and can be adopted in the next generation of North American masonry standards. Moreover, this study highlights the importance of implementing a shear amplification factor to account for the higher mode effects in multistorey RM buildings.
... These elements are connected by different types of distributed normal and shear springs, which are characterised by material-specific constitutive laws. Although this method is far less widespread compared to the FEM, several previous studies do exist that demonstrate its capability to accurately simulate all phases of collapse, including cracking, element separation, and collision (Tagel-Din & Meguro 2000b, 2000a. The geometry of the different components of the test building as well as reinforcement details were accurately reproduced, and material properties of concrete and steel were set based on results of tests performed on reinforcement bars and cylindrical specimens of concrete. ...
... The applied element method (AEM) [45][46][47] is considered an innovative modeling approach that adopts the discrete cracking concept. The AEM has a high capability of predicting the continuum and discrete behavior of structures. ...
The seismic design of mid- and high-rise reinforced masonry (RM) structures necessitates a reliable seismic force resisting system (SFRS) that provides adequate capacity and ductility. Core walls are commonly used as the SFRS for counterpart reinforced concrete buildings due to the convenience of locating the elevators and staircases inside it. This study introduces reinforced masonry core walls with boundary elements (RMCW+BEs) as a potential SFRS alternative to rectangular reinforced masonry shear walls (RMSWs) with and without boundary elements given their enhanced structural and architectural characteristics in typical RM buildings. A macroscale nonlinear numerical model was developed using the Extreme Loading for Structures software (ELS) to evaluate the seismic performance of RMCW+BEs. A nonlinear time history analysis (NLTHA) was carried out for three archetype RM buildings with 10-, 15-, and 20-story heights designed according to the CSA S304-14 and located in a North American moderate seismic zone. The results showed that utilizing RMCW+BEs as the main SFRS system adequately controlled the seismic demands on RM buildings subjected to typical North American ground motions. However, the 20-story building showed a shear demand exceeding the nominal flexural resistance of the core wall at the plastic hinge region at the base, which was attributed to the adverse effect of the higher modes of vibration effects on the seismic demand parameters. Therefore, the three buildings were redesigned using a dual plastic hinge (DPH) design approach. The numerical results demonstrated that using the DPH reduced the shear demand and mitigated the effect of the higher modes of vibration on the seismic response of the core walls. The findings of this study highlight the need to integrate a new shear demand magnification factor to account for the higher mode effects in estimating the seismic demand of ductile RMSWs in the next generation of the North American design standards for masonry structures.
... This extended version to be applied to masonry structures (Yamanoi et al. 2021) define the three directions of possible cracking along the location of mortar joints in advance and the rest of three crack planes are reserved for cracking in the bricks under loads. Then, we may say that this extended version of space-averaging is the hybrid of discrete methods like the rigid body spring method, RBSM (Nagai et al. 2005), and the applied element method (Tagel-Din and Meguro 2000) with the original smeared multi-directional crack model. ...
The extended multi-directional non-orthogonal crack model was applied to the joint interface area between RC members connected by shear dowel and the experimental verification was conducted in use of the low cycle fatigue experiments. The splitting tension field induced by the dowel action around the reinforcing bar is successfully reproduced with the coupled joint crack model and the beam finite elements, and the splitting tension cracking under cyclic fatigue loading and the joint degradation were fairly captured computationally. The effect of spiral steel confinement on the shear dowel performance can be quantitatively evaluated by the generic full 3D nonlinear analysis.
... The Applied Element Method (AEM) has been used to perform nonlinear dynamic computational simulations of the sudden column removal scenarios due to its ability to accurately represent different stages of failure including cracking, separation, and collision , Tagel-Din & Meguro 2000a, 2000b. ...
... The Applied Element Method (AEM) has been used to perform nonlinear dynamic computational simulations of the sudden column removal scenarios due to its ability to accurately represent different stages of failure including cracking, separation, and collision , Tagel-Din & Meguro 2000a, 2000b. ...
... In some cases, when the girders adjoin the column only from two opposite faces in the case of a frame-type assembly, such a stress-strain state can be conventionally considered as biaxial, assuming that the stresses are distributed relatively uniformly over the section width (from the plane of action of bending moments). For a more accurate account of the deformed state of such 2D frame joints, as a rule, approaches are used that are similar to the applied element method [3,4], which has gained wide recognition in recent years in modeling the deformation and destruction of reinforced concrete bearing systems of buildings and structures under special influences. Better convergence with experimental data when using the applied element method compared to the standard FEM procedure in a bar formulation is achieved by simulating the connection between short sections of structural elements using elastic-yielding springs. ...
In the beam-column subassembly and adjacent bar sections of RC frames of frame-braced structural systems, a complex 2D stress–strain state arises. The computational models for such subassemblies presented in the scientific literature are mainly based on a simplified representation of the forces acting in them. These ones allow evaluate the implementation of the characteristic destruction mechanisms and further each of them is analysed separately. Therefore, in this article, a finite difference method is proposed for deformation analysis of a reinforced concrete beam-column monolithic subassembly. A distinctive feature of the proposed solution is the ability to take into account the discrete nature of the reinforcement, as well as the incomplete adhesion of reinforcement to concrete along the contact surface. Also, the article presents an example of calculating the deformed state of a beam-column monolithic subassembly of a RC frame scale model, for which a simulation was previously performed using bar FE. Comparison of the calculation results according to the proposed model and the traditional bar model shows the differences in the deformed state of the 2D RC beam-column joint. This can be explained by taking into account the 2D stress–strain state factors, which are not taken into account in the bar model.
... Lastly, a study from Ehab et al. [46] further explored the use of MDOF by using a nonlinear time history dynamic analysis based on the Applied Element Method (AEM) [165][166][167][168]. AEM was proven to efficiently simulate progressive structural collapse [169,170] since structural pounding can cause damage such as partial collapse and/or total collapse of the subjective pounded structures. ...
Pounding of structures occurs when two or more structures are within proximity subjected to extensive lateral loading leading to a collision of structures. The pounding effect can be mitigated by providing a suitable gap distance between structures or by designing for the additional pounding loads between the colliding structures. These non-typical additional loads, if not properly taken into account, can produce damages within the structures, especially when the pounding structures are vibrating in an out-of-phase order. Multiple pounding incidents have been reported to occur during lateral activities, more specifically towards earthquake phenomena, which resulted in many local and global damages either for specific structures or across an entire region. This review paper articulates the past research regarding pounding hazards, their types, impact and causes, in addition to methods of analyzing structural pounding (i.e., numerically and experimentally).
... If the principal stresses exceed the material strength, the forces of the normal and shear springs are redistributed and reversed as force and a moment at the element's centroid in the next load increment. Tracking the proper crack propagation requires this redistribution and reversing of these forces [13] and [20]. ...
This paper introduces a first attempt of numerical simulation based on the improved applied element method to predict the behavior of prestressed concrete beams with internal unbonded tendon. The multi-layered element is used for modeling the reinforced concrete beam while the unbonded tendon is modeled as an assemblage of straight normal springs that connect the anchorage points with dummy elements generated between each two successive multi-layered elements. Furthermore, an initial loading procedure is added in which the springs representing the tendon are exposed to an initial strain to consider the effect of prestressing. During the analysis, the strain in the unbonded tendon is assumed to be constant along the beam length and is calculated from the displacements of all the dummy elements and anchorage points. Material and geometric nonlinearities are considered in the proposed model for both the multi-layered element and the unbonded tendon. Several verification examples are presented to examine the capability of the model. Comparison between the numerical and the experimental results has shown good agreement, highlighting the reliability of the proposed model.
... It is worth noting that an AEM formulation does not need a geometric stiffness matrix, entailing a simpler numerical procedure in comparison with the cumbersome one adopted by FEM. Ensuing research studies investigated the accuracy of AEM formulation in the case of reinforced concrete structures with nonlinear constitutive material laws applied at the springs [5,6]. The outcomes demonstrated again the feasibility of AEM since it was possible to accurately estimate the failure behaviour, including crack initiation and propagation, both with monotonic and cyclic loads. ...
The Applied Element Method (AEM) is a relatively recent numerical technique, originally conceived for simulating the large displacement nonlinear response of reinforced concrete, masonry and steel structures, and successful applications have been presented by various researchers. Recently, AEM was used to model the mechanical behaviour of steel storage pallet racks, i.e., particular cold-formed steel structures typically employed for storing goods and materials. Such systems are often subjected to peculiar displacements and stresses due to warping effects, which are inherent and often govern their behaviour, increasing the peak strength and ultimate displacement demand. This phenomenon has not been studied through AEM yet; hence, this work investigates the capabilities of AEM in simulating the warping effects in typical steel rack members, i.e., thin-walled C-shaped sections. Preliminary results and comparison against established modelling approaches indicate that AEM can accurately simulate this phenomenon, both in terms of displacements and stresses.
... In the late 1990s, Meguro and Tagel-Din developed a new method for structural analysis called Applied Element Method (AEM) [49][50][51]. This innovative method has the ability to vastly predict the continuum behavior and discrete behavior of structures. ...
Due to the repetitive progressive collapse events, it became necessity to form theories of designs against those cases of loadings. Prestressed reinforced concrete elements become widely used in construction field due to various properties that contribute to enhancing the overall structural stiffness, increasing the loading capacity, and elevating the crack resistance threshold compared to the non-prestressed elements. However, few researches in prestressing members and its capacity towards progressive collapse is covered. According to the Unified Facilities Criteria (UFC) and the General Services Administrations (GSA) guidelines, the pre-stressed precast structure's assessment under progressive collapse are taken into consideration using approximate solutions for analysis. The UFC stated the types of the structure under progressive collapse assessment regardless of the structural system used. This is a great challenge needs a lot of experimental and numerical testing and validation. In this research, a numerical analysis is carried out for a typical five-story framed prestressed precast reinforced concrete structure subjected to column loss (corner column, edge column and internal column near to the structure's edge), and designed according to Precast/Prestressed Concrete Institute (PCI) and (ACI 318À14). Non-linear dynamic analysis for the structure was carried out using Extreme Loading for Structures (ELS) software depending on the AEM. The investigation was done on two levels. Total collapse took place in case 1. As a result, the necessity of extending the research to include case (2) is essential for having an overview assessment of this type of structures. Case 2 showed high capability to resist progressive collapse against all column removal scenarios. The results are indicated in terms of; prestressed beam behavior, prestressing cable contribution, and flexure and axial loads' changes with respect to time. Beam and column rotations are calculated and compared to the UFC limitations to assess its safety towards progressive collapse.
... The Applied Element Method (AEM) [45] [46] [47] is an intelligent and advanced technique for modeling as it adopts the concept of discrete cracking. The elements are divided into small elements in size in the AEM as shown in Figure 3.1b. ...
Progressive collapse is defined as the chain failure of the overall structure due to losing one of the main structural elements. Recently, many codes studied the effect of the overall structure behavior due to the loss of one of the main elements and set some limitations for structures’ safety. However, the influence of different beam span lengths on the overall structure behavior still ambiguous. In this research, a numerical study is conducted on a typical five story precast reinforced concrete structure with ordinary moment frame connection to investigate the effect of varying beam span lengths (6,9, and 12 m) under different column removal scenarios (Corner, interior, and edge columns). The structure is designed according to the Precast/Prestressed Concrete Institute (PCI) and the Building Code Requirements for Structural Concrete (ACI 318-14) codes. Non-linear dynamic analysis for the structure is carried out using Extreme Loading for Structures (ELS) software. The Applied Element Method (AEM) is used to create a 3D model to assess the structure progressive collapse behavior as a result of primary support removal. Structure performance is presented in column, beam, and joints behavior. Axial forces for beams and columns, normal stresses in reinforcement, and maximum beam deflection is used to investigate the effect of different beam span lengths on structural behavior. For different column removal scenarios, the structure showed a partial collapse for different beam span lengths. Also, it’s emphasized that increasing the beam span results in rapid aggressive failure in connection in case of bare frame systems. The results obtained showed that structure designed according to the (ACI 318-14) satisfies all the (UFC) code requirements for the cases that did not show any collapse. The slab catenary action has a significant effect in resisting the structure progressive collapse in most cases. The slab contribution in progressive collapse resistance cannot be neglected as it may result in partial or total structure collapse.
The outcomes of the current research can be stated as follows:
1- Observing the different connection behavior that took place due to column loss for local and full structure model.
2- Observing the actual failure pattern
3- Considering the slab and its effect on the structural behavior.
4- Calculating rotations of the elements connected to the concerned connection (Beams and columns) and compare their values with the UFC code requirements.
The results emphasized that the use of slab for the different cases can work effectively in strengthening the precast beam-column connection as well as preventing local and global system failure due to column loss. Slabs played an important role in increasing the system strength against failure due to column loss and cannot be neglected in future research. finally, the system succeeded in meeting the Unified Facilities criteria limitations as a result of no need for extra design consideration to prevent progressive collapse due to column loss.
... In this analysis, Rankine's failure theory is introduced for crack pattern (Hatem and Meguro 2000). The procedure for calculating principle stresses at spring location is as follows. ...
Recent earthquakes have demonstrated that masonry infill walls cause major damage to the structure. Schools and hospital buildings are not built to achieve adequate lateral strength and stiffness as per seismic codes. The 2001 Bhuj earthquake is one of the examples where 1900 school buildings collapsed and 971 children died due to improper design. The present paper discusses the seismic damage of a G+4 school building through fragility curves. For the purpose of analysis, a severely damaged school building during the 2001 Bhuj earthquake was taken. The building is modeled in Applied Element Method. A non-linear static pushover analysis is performed in displacement control to understand the capacity of building. Finally, the seismic damage is estimated through fragility curves. The building has experienced 15% probability of moderate damage,
and less than 1% probability of collapse at peak ground acceleration of 0.11 g.
Coupling beams significantly influence the performance of coupled shear wall systems under lateral forces. To ensure adequate behavior under lateral load-induced deformations and stresses, coupling beams are typically reinforced with complex reinforcement configurations, such as diagonal bars and confinement reinforcement. However, these reinforcement schemes can complicate construction. In slender coupling beams with an aspect ratio of approximately 3.0, the shallow angle of the diagonal reinforcement (less than 20 degrees) relative to the beam's longitudinal axis raises questions about the effectiveness of this reinforcement. This study investigates the impact of utilizing tensile strain-hardening high-performance fiber-reinforced concrete (HPFRC) in coupling beams. A nonlinear static analysis using the Applied Element Method was conducted to assess the behavior of coupling beams with HPFRC. The analysis was validated using previously tested specimens. A parametric study was performed, considering factors such as the material type (HPFRC vs. regular concrete), the longitudinal reinforcement ratio in coupling beams, the incorporation of HPFRC within the coupled walls, the presence of diagonal reinforcement with or without confining stirrups, the coupling beam's aspect ratio, and the fiber ratio. The results indicated that the use of HPFRC enhances the beam's capacity and provides superior energy dissipation compared to traditional reinforced concrete.
This JRC Science and Policy Report presents scientific and technical background information to introduce the different aspects involved in providing robustness of structures. It is intended to bring together references and ongoing work on the subject as well as stimulate debate. It presents background information, state-of-the-art references and discusses provisions in available guidelines. As such, it serves as a basis for further work to achieve a harmonized European view on the consideration of robustness in the design, execution and assessment of structures. The report focusses on new-build construction, although the underlying principles also apply to existing structures.
The report introduces the general principles of structural robustness, including concepts and terminology, hazards and damage scenarios as well as assessment of the consequences of failure. An overview is provided of current standardization and design guidelines in Europe as well as outside of Europe. Strengths and weaknesses in current provisions are discussed. State-of-the-art information is collected covering alternative design strategies, approaches and considerations. Specific information on strategies to improve robustness is outlined, including the importance of allowing for ageing and deterioration, and aspects related to multi-hazard design. Whilst robustness as a design principle covers a range of extreme design events, including seismic and fire, differences in design approaches for such exposures are also important to recognize. State-of-the-art research information is referenced where available. Finally, a series of novel proposals for robustness provisions is provided encompassing more detailed technical guidance concerning the tying force strategy, the alternative load path strategy, etc. are proposed to encourage discussion.
The most widely used design approaches today for improving the robustness of buildings rely on improving continuity within the structural system to ensure that loads supported by failed components can be redistributed to the rest of the system. Although this is effective for small initial failures, it can increase the risk of disproportionate collapse after larger initial failures due to collapsing elements pulling down parts of the structure that would otherwise be unaffected. This form of continuity-enabled collapse propagation can be avoided by dividing a structure into different segments. However, completely separating parts of a building results in lower performance under operational conditions, against lateral loads, and after small initial failures. In fact, the advantages of both continuity and segmentation can be combined through a fuse-based segmentation approach in which predefined segment borders ensure connectivity after small initial failures but separate to isolate collapse after larger initial failures. To ensure that this approach is used effectively to improve the robustness of building structures, a design framework is proposed in this article to systematically consider relevant structural and geometric criteria in order to define suitable segmentation configurations for reinforced concrete and steel framed building structures. An application to a realistic case study is also presented to demonstrate the effectiveness of the proposed framework in enhancing structural robustness.
Several catastrophic building collapses1–5 occur because of the propagation of local-initial failures6,7. Current design methods attempt to completely prevent collapse after initial failures by improving connectivity between building components. These measures ensure that the loads supported by the failed components are redistributed to the rest of the structural system8,9. However, increased connectivity can contribute to collapsing elements pulling down parts of a building that would otherwise be unaffected¹⁰. This risk is particularly important when large initial failures occur, as tends to be the case in the most disastrous collapses⁶. Here we present an original design approach to arrest collapse propagation after major initial failures. When a collapse initiates, the approach ensures that specific elements fail before the failure of the most critical components for global stability. The structural system thus separates into different parts and isolates collapse when its propagation would otherwise be inevitable. The effectiveness of the approach is proved through unique experimental tests on a purposely built full-scale building. We also demonstrate that large initial failures would lead to total collapse of the test building if increased connectivity was implemented as recommended by present guidelines. Our proposed approach enables incorporating a last line of defence for more resilient buildings.
This paper introduces a novel formulation, called Hybrid Discrete-Finite Element (HybriDFEM) method, for modeling one-directional continuous and discontinuous planar beam-like members, including nonlinear geometric and material effects. In this method, the structure is modeled as a series of distinct rigid blocks, connected to each other through contact pairs distributed along the interfaces. Each of those contact pairs are composed of two nonlinear multidirectional springs in series, which can represent either the deformation of the blocks themselves, or the deformation of their interface. Unlike the Applied Element Method, in which contact pairs are composed of one single spring, the current approach allows capturing phenomena such as sectional deformations or relative deformations between two blocks composed of different materials. This method shares similarities with the Discrete Element Methods in its ability to model contact interfaces between rigid or deformable units, but does not require a numerical time-domain integration scheme. More importantly, its formulation resembles that of the classical Finite Elements Method, allowing one to easily couple the latter with HybriDFEM. Following the presentation of its formulation, the method is benchmarked against analytical solutions selected from the literature, ranging from the linear-elastic response of a cantilever beam to the buckling and rocking response of continuous flexible columns, and rigid block stackings. One final example showcases the coupling of a HybriDFEM element with a linear beam finite element.
The world has seen a surge in rigorous study efforts on the progressive collapse of structures in the past few decades. These events have led to new standards and provisions in building codes of practice, many of which are still being developed and updated today. Although there have been some excellent reviews covering different aspects of progressive collapse, the sheer volume of research performed in this area in recent years means that highly relevant investigation methods and research findings are not covered by them. To fill this void, this review article aims to provide an up-to-date and comprehensive overview of progressive collapse research on building structures. The review is organised into eight sections that cover: (1) essential background information; (2) prominent collapse cases; (3) progressive collapse typology; (4) design standards; (5) investigation methods; (6) prevention and mitigation strategies; (7) structural types and characteristics that require special consideration; and (8) future research needs. In addition to the fundamental concepts, this review encompasses recent advances, such as employing physics and game engines, and machine learning to study progressive collapse. It also explores the potential future applications of these new concepts in research. Furthermore, the review emphasises recent progress in improving the robustness of timber and modular structures. Therefore, this review provides a crucial resource to acquire a global overview of current state-of-the-art progressive collapse research and future requirements, making it valuable to both novice and experienced practitioners and researchers.
Research performed on the progressive collapse of reinforced concrete buildings has led to the development of several design approaches relying on sufficient continuity reinforcement to provide alternative load paths that can prevent collapse after the failure of single columns. However, there are very few works examining the possible contribution that continuity reinforcement could have in pulling down parts of a structure that would otherwise be unaffected after large initial failures. This article presents the findings of a study based on validated simulations of a prototype building using the Applied Element Method (AEM). The results reveal that a large amount of continuity reinforcement can indeed contribute to more failure propagation after very large initial failures by transmitting more unbalanced forces to columns. It is also demonstrated that localised reductions in continuity reinforcement can prevent failure propagation after large initial failures. In addition, it is shown that this can be achieved while still allowing alternative load paths to develop after single-column failure as required by current codes and guidelines.
The present paper employed the Applied Element Method (AEM) to investigate the damage patterns in high-strength concrete (HSC) frames under extreme loads. Unlike existing computational techniques, AEM offers a distinct advantage in accurately identifying structural damage in all stages of loading conditions. The research focuses on analysing the impact of displacement-controlled in-plane cyclic loads on single- and multi-storey reinforced concrete frames with and without infill walls. AEM analysis coincided with experimental results, theoretical predictions, and FEMA 356 code provisions, affirming a reliable examination of cyclic damage patterns. The study reveals distinct damage patterns, shedding light on infilled frames' superior in-plane lateral load resistance compared to bare frames. Interestingly, multi-storey frames with soft-storey configurations exhibited higher resistance to lateral loads than those with infilled walls due to premature collapse of HSC columns. The study highlights the crucial role of robust, strong infill walls in reinforcing slender HSC frames. The results provide valuable insights for designing resilient structures under extreme operating conditions, thus contributing to advancing structural engineering practices.
The Applied Element Method (AEM) and the Improved Applied Element Method (IAEM) are now recognized as efficient discretization procedures to follow through the stages of collapse of structures. Recently, the IAEM has been extended to study the collapse of post-tensioned bonded and unbonded concrete girders under various circumstances associated with blast loading. In this article, emphasis is given to study the effect of the probabilistic nature of blast loading as it acts on prestressed concrete girders, where analysis is carried out using IAEM. This is conveniently done by using the Monte–Carlo simulation technique from the statistical library of MATLAB mathematical software in order to predict and manipulate the statistical response due to probabilistic blast loading. The reflection overpressure is considered the random variable in the probabilistic analysis, whereas material characteristics and girder geometry are treated as deterministic variables. Formulations are given in case where other material or section parameters are of a probabilistic nature, in which case the performance function is expanded in the vicinity of the mean of the probabilistic parameters in order to predict the probability of failure. The established procedure paves the way to predict the probability of failure of girders due to blast loading affecting one or several components of the bridge.
High-strength concrete (HSC) is widely used in developed countries for reinforced concrete structures due to benefits like lower concrete use, smaller columns, increased floor area, and economic advantages. HSC reduces deflections and offers a high elastic modulus and low creep deformations, making it valuable in seismic-prone areas by decreasing inertial loads and lateral drift. However, the lack of new concrete standards for HSC challenges structural engineers. Infill walls are essential for separating interior spaces, particularly in seismic regions where weak infill within a strong frame dissipates energy and reduces lateral displacements. Nonetheless, weak infill behaves more brittle under intense seismic loads, posing risks like falling debris and causing casualties. Openings in infill walls are necessary for practical, architectural, or esthetic reasons, but their strength and stiffness contributions are often neglected in current design practices. Infill walls significantly alter a building’s seismic response compared to a bare frame, while frequent openings reduce the infilled frame’s lateral stiffness and strength. A micro-modeling study using the Applied Element Method (AEM) examines the role of brick masonry infill with various sizes and positions of openings. Ten single-storey, single-bay infilled frames with different percentages of openings undergo displacement-controlled cyclic loading. The lateral load capacities, displacements, and energy dissipation are compared for high-strength concrete frames with openings. Results showed that weak infill–strong frames with and without openings altered lateral load resistance, and severe failure was observed on either side of the central opening. The vertical position and the shape of the openings also influence the studied parameters.
This study draws attention on proper planning and construction practices for multi-storied buildings on sloping ground. However, in usual design practice the designers generally ignorethe behavior of the building due to the effect of sloping ground. The evaluation of a G+4 storey RCC structure on varying sloping angles (00 , 150 , 200 , 250 , 300 and 400 ) were studied and also compared with the flat surface. The evaluations of the structure were carried by the software STAAD Pro v8i to study the effect of slopes on building performance. The evaluation was done to figure out the effect of sloping ground on the forces applied on the structure. Soil interaction must be suitably believed from design point of view. The Research work triesto find the truth about the earthquake-related behavior of multi storey structures on sloping angles thinking about soil-structure interaction. The horizontal reactions, bending moment in footings and axial force, bending moment in columns were critically studied to put the effectsof different sloping ground. It has been followed that the footing columns of lower height attract more forces, because ofa big increase in their stiffness, which in turn increases the horizontal forces and bending moment. So, the section of these columns should be designed for changed forces due to the effect of sloping ground. It draws attention to the need for proper analysis and designing of the structure resting on sloping surface. Overall movement of the structure with respect to different sloping ground setups is also carefully studied.
A systematic and appropriate selection of columns to be removed should be conducted to ensure the safe and reliable demolition of old or uninhabitable buildings. However, the explosive demolition techniques used at present mostly rely on experiences and know-how built up by predecessors and are not fully open to general users. Therefore, a clear selection criterion for columns to be removed should be developed based on a quantitative value that indicates the contribution of each column in a building structure. This study applied a key element index to evaluate the contribution of columns and their variance to multistage explosive demolition planning. An adaptively shifted integration (ASI)-Gauss code was used to simulate and investigate the explosive demolition sequences of a 10-story steel-framed building. Various timings between the multistage blasts were evaluated by comparing the efficiencies and levels of safety during demolition. By removing the groups of columns from those that had a greater influence on the variance of the key element index values, a large difference was obtained in the distribution of the index values, especially in the lower structure. The results showed that if a building is not too weakened in the initial blast, the 2nd blast of the main blasts should be conducted at the moment of impact between the upper and lower structures or the following short time to make the most of the impact. The results also showed that too much weakening of a building at the preceding stage might not provide full advantage of the impact that occurs between the main blasts.
Odporność konstrukcji i łagodzenie skutków katastrofy postępującej to specyficzne aspekty bezpieczeństwa uwzględniane we współczesnych wytycznych i normach, również w Eurokodach. Aspekty te powinny być brane pod uwagę przez specjalistów związanych z branżą budowlaną, w tym architektów, projektantów, konstruktorów, pracowników nadzoru budowlanego, jak również agentów ubezpieczeniowych. Katastrofa wież World Trade Center w Nowym Jorku z 11 września 2011 roku spowodowała, że dostrzeżono znaczenie zapewnienia odporności konstrukcji na zdarzenia ekstremalne i potrzebę opracowania wytycznych do projektowania obiektów budowlanych w sytuacjach wyjątkowych. Dostęp do takich wytycznych, adresowanych do różnych grup specjalistów budowlanych, uwzględniających różne przeznaczenie i potencjalne zagrożenia, umożliwi projektowanie bezpiecznych konstrukcji stalowych i zespolonych.
W ostatniej dekadzie zrealizowano (zwłaszcza w Europie i USA) wiele projektów badawczych dotyczących tematyki zachowania się konstrukcji stalowych i zespolonych w różnych sytuacjach wyjątkowych (uderzenia, pożary, trzęsienia ziemi, itp.). Wyniki tych badań wykorzystano do sformułowania propozycji praktycznych metod zapobiegania powstawaniu katastrofy postępującej poprzez efektywne projektowanie i wykorzystanie w pełni właściwości materiałów stosowanych w konstrukcjach stalowych i zespolonych.
La robustezza strutturale per la mitigazione del collasso progressivo identifica un aspetto specifico della sicurezza considerato dai moderni codici di calcolo e dalle normative, inclusi gli Eurocodici, e che richiede particolare attenzione da parte di tutte le figure professionali coinvolte nell’industria delle costruzioni, inclusi architetti, progettisti, addetti al controllo, e agenti assicurativi. L’importanza del progetto nei confronti della robustezza strutturale è stata messa in luce da eventi disastrosi recentemente accaduti che hanno avuto risonanza mondiale come ad esempio il crollo delle Torri Gemelle dell'11 settembre a New York City e che hanno evidenziato la necessità di specifiche linee guida progettuali. La disponibilità di linee guida rivolte alle diverse figure professionali coinvolte nel settore delle costruzioni, che tengano conto dell’uso e dei rischi associati ai differenti edifici contribuisce nel garantire la necessaria fiducia nella sicurezza delle costruzioni in acciaio e miste acciaio-calcestruzzo.
Durante l’ultimo decennio, è stato condotto un numero significativo di progetti di ricerca riguardanti la risposta di strutture di acciaio e miste acciaio-calcestruzzo in presenza di azioni eccezionali (urti, incendio, sisma, ……), specialmente in Europa e negli USA. Un risultato di questi progetti è stata la proposta di possibili metodi operativi finalizzati alla mitigazione del collasso progressivo attraverso progettazioni efficaci attuate considerando tutte le potenzialità dei materiali utilizzati nelle strutture di acciaio e miste acciaio-calcestruzzo.
Robustnost konstrukce pro zmírnění rizika progresivního zřícení je bezpečnostním hlediskem, které se řeší v moderních předpisech a normách, včetně evropských. Vyžaduje součinnost všech odborníků ve stavebnictví, architektů, projektantů, statiků, konstruktérů, státní správy a pracovníků pojišťoven. Důležitost robustního návrhu zvýraznily události, jako bylo zřícení Dvojčat 11. září v New Yorku.
Společnost se z tragédii poučí a vznikne nová generace směrnic pro využití v praxi. Vhodné materiály pro pracovníky ve stavební praxi pro přípravu na řešení rizikových situací vytváří povědomí o kvalitě a velké spolehlivosti ocelových a ocelobetonových konstrukcí.
V uplynulém desetiletí se v Evropě a v USA řešila řada výzkumných projektů o odezvě nosné konstrukce ocelových a ocelobetonových budov při mimořádných situacích, při mimořádném zatížení nárazem, požárem, zemětřesením atd. Výsledkem prací jsou návrhy
konstrukčních řešení ke zmírnění rizika prostorového zřícení, které zohledňují možnosti materiálu v ocelových a ocelobetonových konstrukcích.
De constructieve robuustheid voor de beperking van progressieve instorting is een specifieke veiligheidsaspect die nu in moderne codes en normen, zoals de Eurocodes, wordt behandeld, die bijzondere zorg vereist van alle professionals die bij de bouwsector betrokken zijn, o.a. architecten, ontwerpers, constructeurs, controleurs en verzekeringsmanagers. Het belang van een robuust ontwerp is erkend door rampen die de wereld hebben getroffen, zoals de instorting van de Twin Towers in New York City op 11 september 2001, en de behoefte aan praktische richtlijnen is hierdoor aangewakkerd. De praktische richtlijnen die bestemd zijn voor de verschillende bouwprofessionals en betrekking hebben op specifieke gebruiks- en risicosituaties voor gebouwen
dragen bij tot het opbouwen van vertrouwen in de veiligheid van staalen composietconstructies.
De afgelopen decennia is met name in Europa en de Verenigde Staten een aanzienlijk aantal onderzoeksprojecten op het gebied van de constructieve respons van staal- en composietgebouwen onder verschillende buitengewone belastingsomstandigheden (botsing, brand, aardbeving...) voortgezet. Uit deze recente wetenschappelijke studies zijn verschillende ontwerpbenaderingen voorgesteld om de progressieve instorting te beperken, rekening houdend met het volledige potentieel van materialen die in staal- en composietconstructies worden gebruikt
Robustețea structurală și prevenirea colapsului progresiv sunt cerințe specifice de siguranță, care sunt prevăzute în normele și standardele moderne, inclusiv Eurocoduri. Aceste cerințe necesită o atenție deosebită din partea tuturor profesioniștilor implicați în industria construcțiilor, adică arhitecți, proiectanți, verificatori, constructori sau asiguratori. Importanța proiectării la robustețe a revenit de fiecare dată în atenție odată cu producerea unor dezastre, cum ar fi prăbușirea Turnurilor Gemene din New York la 11 septembrie 2001, reiterând astfel necesitatea dezvoltării unor ghiduri de proiectare si
reguli de bună practică. Într-adevăr, disponibilitatea unor ghiduri de proiectare adresate profesioniștilor din domeniul construcțiilor, care să acopere situații specifice de risc pentru clădiri, contribuie la creșterea nivelului de încredere și a siguranței construcțiilor din oțel și compuse oțel-beton.
În ultimul deceniu a fost realizat un număr semnificativ de proiecte de cercetare în domeniul răspunsului structural al clădirilor cu structură din oțel și oțel-beton în cazul unor situații excepționale de încărcare (impact, incendiu, cutremur, …), în special în Europa și SUA. Rezultatele acestor activități științifice au permis dezvoltarea unor metode de proiectare destinate reducerii sau prevenirii colapsului progresiv, în special prin utilizarea cât mai eficientă a materialelor si elementelor folosite în structurile din oțel și compuse oțel-beton.
Structural robustness and mitigation of progressive collapse is a specific safety consideration which is now addressed in modern codes and standards, including the Eurocodes, and which requires particular care from all professionals involved in the construction industry, including architects, designers, constructors, control officers, and insurance managers. The importance of the robustness design has been recognised by world shaking disasters such as the 9/11 collapse of Twin Towers in New York City
and the need for practical guidelines has been triggered. Indeed, the availability of such guidelines for practical application addressed to various construction professionals considering different use and risk of buildings helps to ensure confidence in safety of steel and composite construction. During the past decade, a significant number of research projects related to the structural response of steel and composite buildings under various exceptional loading situations (impact, fire, earthquake,…) have been carried out, especially in Europe and in the USA. As an outcome of these recent scientific
actions, different possible practical methods have been proposed to achieve the mitigation of progressive collapse through effective designs and accounting for the full potential of material characteristics in steel and composite structures. Purpose of the project “Mitigation of the risk of progressive collapse in steel and composite building
frames”- FAILNOMORE, is to consolidate the knowledge developed in the aforementioned research and transform it into practical recommendations and guidelines. The set of practical and user-friendly design guidelines for mitigating the risk of progressive collapse is focused on steel and composite structures subjected to exceptional events such as impact, explosions, fire, seismic, referring also to available normative documents, in order to propose a commonly agreed European design methodology. The project was funded for 24 months (starting from July 2020) by the Research Fund for Coal and Steel (RFCS) under grant agreement No 899371.
The resiliency of electricity transmission and distribution lines towards natural and man made hazards is critical to the operation of cities and businesses. The extension of these lines throughout the country increases their risk of extreme loading conditions. This paper investigates a unique extreme loading condition of a 100-year-old distribution line segment that passes across a river and got entangled with a boom of a ship. The study adopts the Applied Elements Method (AEM) for simulating 54 cases of the highly deformable structural behaviour of the tower. The most significant effects on the tower’s structural integrity were found to occur when applying the load with components in all three of the cartesian directions (i.e., X, Y and Z) with the full capacities of the four cables. The studied extreme loading condition was determined to be within the tower’s structural capacity, attributed to the shear failure of the anchor bolts, which acted as a sacrificing element that fails to protect the transfer of tensioning load to the supporting tower.
Corrosion due to insufficient grout filling can result in a sudden fracture of PC steel tendons. When a vertically tightened PC tendon in PC girders is ruptured, all the accumulated strain energy is suddenly released. The ruptured PC bar will severely damage cover concrete and asphalt pavement, and PC bars may protrude out of the structure, which may cause severe accidents. In the current study, the effects of 15 mm cover concrete and two-layered asphalt pavement system on preventing protrusion of PC bars were investigated. Numerical simulation of rupture and protrusion of PC bars were studied using the Applied Element Method. The numerical simulations were verified based on the experimental results. In the process of verification, many influential parameters, such as the effects of contact stiffness between elements, fracture energy of concrete, mesh sensitivity, time interval sensitivity, material properties, and strain rate effect, were investigated. This study found that AEM numerical simulation with appropriate modeling showed good agreement with the experimental results, which exhibited the effectiveness of the asphalt pavement system with appropriate material and thickness preventing protrusion of the PC bar tendon.
High rise buildings subjected to lateral loads such as earthquake must have systems
that can resist the shear forces and bending moments generated by earthquake. There are
a lot of systems as shear walls and it was found that shear walls can develop lateral
stiffness and strength if they are connected by coupling beams. Therefore, coupling beam
must be rigid and ductile to produce required strength and dissipate energy. The aim of
this thesis is to study the effect of using high performance fiber reinforced concrete to
construct coupling beams due to its strain hardening behavior. Therefore, mid-rise
reinforced concrete multi storey coupled walls with high performance fiber reinforced
concrete coupling beams were modeled. A parametric study was carried out to study the
effect of various parameters that could influence the behavior of high performance fiber
reinforced coupling beams including (1) material type, (2) longitudinal reinforcement
ratio of coupling beams, (3) high performance fiber reinforced concrete embedment
inside the coupled walls, (4) presence of diagonal reinforcement with and without
confining stirrups, (5) coupling beam's aspect ratio, and (6) different high performance
fiber reinforced concrete mixtures.
School buildings being a critical social infrastructure, assessment of their seismic behaviour is of utmost importance in ensuring safe schooling facilities in locations of high seismicity. This study presents two important aspects in analysing any existing building stock for seismic behaviour: the development of an appropriate taxonomy system and an appropriate analytical method to conduct fragility assessment. A detailed desk study of existing schools’ databases and tailored field investigation in Guwahati, Assam, situated in India’s highest seismic zone, reveal that the majority of school buildings can be categorised within the confined masonry (CM) typology. This study discusses first, the addition to the World Bank promoted Global Library of School Infrastructure taxonomy of the specific category relating to CM as to include the buildings under study, which are non-engineered CM buildings with flexible roofs. Identifying the density of confinement and quality of connections as critical parameters for the seismic response of these buildings, varying seismic design levels are defined in relation to these indicators. Secondly, the paper presents an approach for carrying out nonlinear static pushover analysis of these buildings with flexible diaphragms and elaborates on the criteria adopted for determining the performance drift limits in buildings with varying levels of seismic design. Numerical analysis for the capacity assessment of selected index buildings is carried out using a commercial software that enables nonlinear extreme loading analysis. Different failure mechanisms as a function of the level of confinement are identified and the performance range for three damage states for three index buildings is obtained by using the N2 method. The study shows the influence of both choices of performance indicators and intensity measure on the resulting fragility functions. Given the consistency of the educational building stock in Guwahati, the results can be used for investment on retrofit decision making at regional level.
The paper describes the complexity of the seismic assessment and rehabilitation of Hotel St George in Wellington, a 1920's heritage, 8-storey concrete encased steel frame structure (c.10.000m 2). The assessment was performed using Progressive Collapse Analysis. This method has been materialised into explicit requirements for redundancy in building codes. Conventionally, the engineering industry uses a simplistic procedure for most seismic assessments, which models only linear beam and column elements. This neglects the contribution of walls and slabs, leading to uneconomic solutions. Walls and slabs may be considered secondary members in other types of analysis but in progressive collapse analysis, walls and slabs often behave as primary members with slabs carrying load though membrane action and walls providing alternate load paths in case of loss or extensive damage of columns. The building has been modelled using the "Applied Element Method" (AEM). This approach allows tracking of the structural collapse behaviour passing through all stages of the application of loads including elastic stage, crack initiation and propagation in tension-weak materials, steel yielding, element separation and element collision. A significant breakthrough not only for the New Zealand industry but also for the international engineering community. Extensive research was undertaken to overcome the modelling complexities to incorporate the riveted connections, slabs, infill panels, foundation and surrounding soil and to assess the performance of the structure using state of the art methodology. A set of Numerical Integration Time History (NITH) analyses in compliance with AS/NZS 1170.5 recommendations was completed for the Progressive Collapse methodology. Various geotechnical and material testing was undertaken to confirm the parameters used in the analyses. To validate the accuracy of the model, the results were checked against ASCE41-06 acceptance criteria in conjunction with AS/NZ code requirements and limitations. The results indicate the efficiency of the specific methodology to visualise the extent, magnitude and direction of any potential collapse or crack occurrences within the structure and provide accurate insights on the performance of the building, leading to the most effective strengthening strategy.
The paper describes the complexity of the seismic assessment and rehabilitation of three different existing buildings in New Zealand. The assessment was performed using Progressive Collapse Analysis. This method has been materialized into explicit requirements for redundancy in building codes. Conventionally, the engineering industry uses a simplistic procedure for most seismic assessments, which models only linear beam and column elements. This neglects the contribution of walls and slabs, leading to uneconomic solutions. Walls and slabs may be considered secondary members in other types of analysis but in progressive collapse analysis, walls and slabs often behave as primary members with slabs carrying load though membrane action and walls providing alternate load paths in case of loss or extensive damage of columns.
The buildings have been modelled using the “Applied Element Method” (AEM) [1, 2, 3]. This approach allows tracking of the structural collapse behavior passing through all stages of the application of loads including elastic stage, crack initiation and propagation in tension-weak materials, steel yielding, element separation and element collision. It has also the unique ability to accurately evaluate the dynamic Eigen modes accounting for the phenomenon of period elongation due to cracking of the structural elements during the ground excitation. Period elongation is a phenomenon that may alter significantly the response of the structures and the effects of the ground motions on the buildings. This is a significant breakthrough not only for the New Zealand industry but also for the international engineering community.
Extensive research was undertaken to overcome the modelling complexities to incorporate the specific building characteristics including riveted connections, slabs, infill panels, foundation and surrounding soil and to assess the performance of the structures using the state of the art methodology [4, 5, 6, 7]. A set of Numerical Integration Time History (NITH) analyses in compliance with AS/NZS 1170.5 [7] recommendations was completed for the Progressive Collapse methodology. Various geotechnical and material testing was undertaken to confirm the parameters used in the analysis. The ground motions were selected and scaled in accordance with Site Specific Seismic Hazard Assessments.
To validate the accuracy of the models, the results were checked against ASCE41-13 [8] acceptance criteria in conjunction with AS/NZS code requirements and limitations [7, 9]. The post-earthquake observation in one of the case studies were used to validate the results of our analysis. The results indicate the efficiency of the specific methodology to visualize the extent, magnitude and direction of any potential local or global collapse or crack occurrences within the structures and provide accurate insights on the performance of the buildings, leading to the most effective strengthening strategy.
This methodology also enables the engineers to safely design the egress routes away from falling debris, for the safe evacuation of the buildings during the earthquakes.
Applied Element Method (AEM) is an efficient tool for analysing structures numerically. It has a few benefits when conventional methods are concerned. In conventional numerical methods, node-to-node connection is important. Hence, when elements of different sizes are to be connected, transition elements will have to be used. In AEM, rigid elements are connected to each other with the help of springs. Therefore, node-to-node connection is not required. In this paper, some plane stress problems are analysed using AEM. For this, two-dimensional (2D) element is made use of. Continuous beam and 2D frame are analysed using AEM. The results show that AEM is able to analyse beams and frames accurately. Modal analysis of beam clamped on one end and hinged at the other end, gave accurate first natural frequency and mode shape. It was also possible to perform nonlinear analysis of cantilever beam accurately.
The Distinct Element Method (DEM), in which soil is represented as an assembly of numerous discrete particles, does not account for the continuity of the medium. The extended method has another physical structure which represents the effect of the internal material between the particles as mortar of concrete. We simulated the two-dimensional dynamic fracture process of the Cypress Double-Deck Bridge on Interstate 880-Line suffered by the 1989 Loma Prieta earthquake using this method. Results agree well with the real damage qualitatively and confirmed that this method can simulate the collapse of structures involving discontinuous behavior.
A finite element alternating method is presented and applied to analyze two-dimensional linear elastic mixed-mode fracture problems with single or multiple cracks. The method involves the iterative superposition of the finite element solution of a bounded uncracked plate and the analytical solution of an infinite two-dimensional plate with a crack subjected to arbitrary normal and shear loadings. The normal and shear residual stresses evaluated at the location of fictitious cracks are fitted by appropriate polynomials through the least-squares method. Based on those coefficients of the determined polynomials, the mixed-mode stress intensity factors can be calculated accurately. The interaction effects among cracks are also considered. This method provides a highly efficient way to deal with two-dimensional fracture problems.
The rigid bodies—spring models (RBSM) were applied to the phenomenon of crack growth in three-dimensional problems and demonstrated the effectiveness of the models. The characteristic of RBSM is to give practical answers withing a relatively small number of degrees of freedom in the limit analyses such as strongly non-linear and fracture analyses; the models have already proved useful for the analysis of two-dimensional problems. In this paper, the practical application of the three-dimensional RBSM is presented, and the conventional constitutive law of steels is discussed. Compared with the experimental data, the potential fracture criteria are determined. The stable crack growth in an arbitrarily shaped intitial crack is simulated. The plastic zone of the crack tip demonstrate that Mohr—Coulomb's law may be more suitable than von Mises'. The effectiveness of the cutting criterion for the springs of the RBSM is verified in the application to an arbitrarily shaped crack. In an application to dynamic crack propagation of brittle material, the simulated crack propagation is in resonable agreement with the actual crack propagated in the residual stress field of the welded plate.