The numerical modeling of structures is a widely preferable approach to investigate the structura... more The numerical modeling of structures is a widely preferable approach to investigate the structural behavior of RC beams since it delivers inexpensive predictions for confirming the required goals concurrently with reducing casting, testing time, and effort. Shear-strengthening of reinforced concrete (RC) beams using externally bonded (EB) fiber-reinforced polymers (FRPs) has attracted much attention due to the fact that the FRP strengthening technique has the ability to alter the distribution of stresses between the structural elements and increase the load-carrying capacity. A significant number of experimental studies have been carried out to test the monotonic behavior of FRP shear-strengthened RC beams. Conversely, limited numerical research has been performed to investigate such performance. The VecTor2 software is developed based on the modified compression field theory (MCFT) and is directed to examine the monotonic behavior of retrofitted specimens using fiber-reinforced polymer (FRP) composites. To the authors’ knowledge, the behavior of FRP shear-strengthened beams has not been explored in the literature using the MCFT modeling approach. The main objective of this study is to detect the software’s capability of predicting the experimental outcomes of FRP shear-strengthened RC beams. This research study is carried out in two stages. Initially, the numerical study involves the development of an accurate finite element model to simulate the control specimens. The quality of this model is assessed by comparing the numerical results with the experimental outcomes. In the second phase of the numerical study, the control …
Progressive collapse of reinforced concrete (RC) building due to column failure can cause human c... more Progressive collapse of reinforced concrete (RC) building due to column failure can cause human casualties and severe irreparable damage or total collapse of the building. Different methods have been presented to mitigated progressive collapse of RC buildings; however, most of them are installed externally after construction and are costly, demanding, and require manufacturing mitigating elements such as steel cables, steel devices, or composites. This study presents an innovative mitigating scheme to improve the progressive collapse resistance of such buildings. The proposed scheme applies during construction and comprises of adding short wasted leftover steel bars from the construction site with special configuration in the slab around potential failed interior column. To examine the effectiveness of the proposed scheme, three-dimensional nonlinear fiber element-based model was developed, validated, and utilized for the analysis of such buildings. The findings of the study show that the proposed scheme improved progressive collapse behavior of the building with a percentage increase in total dissipated energy up to 241.8%. The scheme is eco-efficient and cost effective as it requires minimum amount of material, saves energy required to produce new steel bars, and can serve as an effective solution to mitigate progressive collapse of RC buildings subjected to column failure.
One of the factors that lead to potential progressive collapse of structures is removal of a load... more One of the factors that lead to potential progressive collapse of structures is removal of a load-bearing element such as a column. In this paper, a technique and a numerical procedure are presented for mitigation and evaluation of potential progressive collapse of reinforced concrete continuous beams following removal of interior columns. The procedure presented for mitigating progressive collapse proposes the use of external unbounded Fiber reinforced plastic (FRP) cables attached to the beam at anchorage locations and deviators/ saddle point(s) only, without being posttensioned. The cables will be in effect when excessive vertical displacements and deformations occur in the mitigated beam due to removal of the interior column support of the beam. The proposed numerical model evaluates the progressive collapse of such beams using a push-down analysis to simulate column removal. It assumes that the anchorage and deviator locations of the external cables act as rigid arms that connect the external cables to the beam. Parameters such as beam cross-section shape, location(s) of deviator/saddle point(s), area and profile of the external unbounded FRP cables are considered in the proposed model. The model predicts the strength of beams mitigated by the proposed technique and evaluates the effects of the external cables on the beam ductility. Numerical results of the proposed mitigation technique obtained by the proposed numerical model are compared to those in the literature.
This paper focuses on the methodology for modeling the dynamic behavior of steel structures due t... more This paper focuses on the methodology for modeling the dynamic behavior of steel structures due to severe earthquake ground motions. The development of the Improved Applied Element Method for analyzing the entire behavior of large-scale steel structures up to total failure is briefly discussed. The main features of the method are illustrated. The presented case-studies show different collapse mechanisms of moment-resistance steel frame structure under severe ground motions. The results show high capability on simulating the observed damage of many steel structures due to recent earthquakes.
One of the factors that lead to potential progressive collapse of structures is removal of a load... more One of the factors that lead to potential progressive collapse of structures is removal of a load-bearing element such as a column. In this paper, a technique and a numerical procedure are presented for mitigation and evaluation of potential progressive collapse of reinforced concrete continuous beams following removal of interior columns. The procedure presented for mitigating progressive collapse proposes the use of external unbounded Fiber reinforced plastic (FRP) cables attached to the beam at anchorage locations and deviators/ saddle point(s) only, without being posttensioned. The cables will be in effect when excessive vertical displacements and deformations occur in the mitigated beam due to removal of the interior column support of the beam. The proposed numerical model evaluates the progressive collapse of such beams using a push-down analysis to simulate column removal. It assumes that the anchorage and deviator locations of the external cables act as rigid arms that connect the external cables to the beam. Parameters such as beam cross-section shape, location(s) of deviator/saddle point(s), area and profile of the external unbounded FRP cables are considered in the proposed model. The model predicts the strength of beams mitigated by the proposed technique and evaluates the effects of the external cables on the beam ductility. Numerical results of the proposed mitigation technique obtained by the proposed numerical model are compared to those in the literature.
International Journal of Protective Structures, 2016
Recent guidelines have addressed provisions to improve structure integrity to accommodate progres... more Recent guidelines have addressed provisions to improve structure integrity to accommodate progressive collapse due to failure of an interior support. This article presents novel technique and numerical model to enhance and evaluate reinforced concrete frame robustness to progressive collapse triggered by an interior or edge column failure in any floor. The presented technique enhances the structure robustness to progressive collapse by providing sufficient ductility, continuity, and redundancy. The technique involves placing external unbounded steel cables attached to the continuous beam in each floor at anchorage and deviator locations to bridge over a damaged column of any floor of the frame. The cables transfer the loads above the failed column to the anchorages and deviators that are assumed to perform as rigid arms, which in turn redistribute the loads to adjacent columns. The numerical model computes the frame building progressive collapse robustness using push-down analysis to simulate a column elimination and estimate the effects of cable catenary action on the frame. Two-dimensional reinforced concrete frame of six stories and four bays was adopted in the study. The numerical results demonstrate the prospect of resisting progressive collapse of reinforced concrete structures by implementing the presented technique.
Optimal finite element modelling for modal analysis of liquid storage circular tanks
Model analysis of liquid storage vertical tanks is a complex task due to fluid-structure-soil int... more Model analysis of liquid storage vertical tanks is a complex task due to fluid-structure-soil interaction. Analysis of tanks subjected to earthquake excitations using finite element modelling (FEM) has become a preferred technique. The FEM is validated by comparing its results with experimental and theoretical results in the literature. However, most finite element studies in literature do not provide enough details on the selection of the elements used. The objective of this study is to provide optimal FEM options of parameters such as element types and number of elements which best predict the tank dynamic characteristics, natural frequencies and principal mode shapes. Coupled natural frequencies in sloshing modes were obtained for various tank height-to-diameter ratios, various tank wall thicknesses and various liquid depths. The FEM predictions compared well with literature available experimental and numerical results. A set of FEM options of parameters is recommended for elastic and inelastic analysis of such tanks.
In this paper, rate type constitutive equations using the Jaumann and 2nd Piola-Kirchhoff stress ... more In this paper, rate type constitutive equations using the Jaumann and 2nd Piola-Kirchhoff stress rate are used to develop axisymmetric finite strain, elastic, closed form solutions for a variety of loading conditions. We examined several cases comprizing compression-extension loading conditions, simple shear and cavity expansion conditions. Results from small strain analyses are used to indicate strain ranges for which such analyses will provide satisfactory solutions. For all the cases examined, except simple shear, the 2rid Piola-Kirchhoff stress rate does not appear to be a suitable stress rate to describe a material which follows a rate-type constitutive equation for strains greater than about 40%. The Jaumann stress rate solution shows oscillatory shear stress for axisymmetric simple shear similar to that found earlier by many other authors for rectangular (or cuboidal) condition. Negative excess pore water pressure (suction) at the cavity wall during the expansion of a cylindrical cavity was also observed in Jaumann stress rate solution.
During the past decade, increasing attention has been focused on the design of buildings to resis... more During the past decade, increasing attention has been focused on the design of buildings to resist progressive collapse. To obtain full knowledge of the total behavior of structures under extreme loading conditions, it is essential to simulate the collapsing process and the trace of yielding, damage and deformation at each structural member. Reliable numerical models are highly required as a cost effective method of obtaining a comprehensive knowledge of the main parameters that affect the response of structures. Simulation of the collapse mechanism requires an advanced technology to accurately predict member instability, failure evaluation, rupture of member joints and impact force of the falling debris. Recently, the improved applied element method (IAEM) has been introduced to simulate the total behavior of large-scale steel towers with high accuracy and low computational effort. However, its application was limited to structures with homogeneous material. In this paper, a new improvement to the IAEM is introduced to develop a novel numerical simulation analysis of failure and collapse of RC and composite structures under hazardous loads. With the new method, structures with homogenous and nonhomogenous materials such as steel, RC and composite can be simulated with high accuracy. The proposed technique takes into account geometric and material nonlinearities. The reliability of the code is investigated by comparing its results with existing experimental and numerical results. Results show that a good agreement between the analytical and the experimental results can be obtained in a less computational time.
One of the factors that lead to potential progressive collapse of structures is removal of a load... more One of the factors that lead to potential progressive collapse of structures is removal of a load-bearing element such as a column. In this paper, a technique and a numerical procedure are presented for mitigation and evaluation of potential progressive collapse of reinforced concrete continuous beams following removal of interior columns. The procedure presented for mitigating progressive collapse proposes the use of external unbounded Fiber reinforced plastic (FRP) cables attached to the beam at anchorage locations and deviators/ saddle point(s) only, without being posttensioned. The cables will be in effect when excessive vertical displacements and deformations occur in the mitigated beam due to removal of the interior column support of the beam. The proposed numerical model evaluates the progressive collapse of such beams using a push-down analysis to simulate column removal. It assumes that the anchorage and deviator locations of the external cables act as rigid arms that connect the external cables to the beam. Parameters such as beam cross-section shape, location(s) of deviator/saddle point(s), area and profile of the external unbounded FRP cables are considered in the proposed model. The model predicts the strength of beams mitigated by the proposed technique and evaluates the effects of the external cables on the beam ductility. Numerical results of the proposed mitigation technique obtained by the proposed numerical model are compared to those in the literature.
The pertinence of the fiber element approach to enable thorough numerical investigation on the po... more The pertinence of the fiber element approach to enable thorough numerical investigation on the potential for progressive collapse of reinforced concrete (RC) frame structures owing to interior column exclusion is examined using twenty-nine RC sub-assemblages with five different test setups and three different test scales. A qualitative examination of the results reveals a good agreement between the test results and the outcomes of the fiber-element-based numerical model using the finite element package SeismoStruct. Moreover, minor discrepancies between the test and numerical data demonstrate the capability of the fiber-element-based model to accurately simulate the behavior of RC elements with various boundary conditions and scales under the context of progressive collapse. Given the costly nature of experimental research, test errors, and the lengthy testing process, the proposed numerical model based on the fiber element approach can be considered a viable option for analyzing st...
This work addresses the field of collapse analysis of steel framed structures under severed loadi... more This work addresses the field of collapse analysis of steel framed structures under severed loading conditions. Applied Element Method (AEM) is recognized as a powerful tool for analyzing the structural behavior from the early stage of loading up to total collapse. This method has been used successfully with different types of material such as reinforced concrete, soil and masonry. A new extension of this method is proposed in this paper in order to simulate large-scale steel structures. The Improved Applied Element Method (IAEM) has been presented and employed in the development of novel numerical solutions for analysis of failure and collapse of large-scale structures under different hazardous loads. A series of numerical examples, including both geometric and material nonlinearity, are used for validation of the improved method. The results indicate that the improved method is capable of accurately analyzing the ultimate load-carrying capacity of steel structures. The case study,...
This study presents numerical findings of an investigation into the effect of beam dimensions and... more This study presents numerical findings of an investigation into the effect of beam dimensions and sagging and hogging reinforcement ratios on progressive collapse response of reinforce concrete (RC) frame sub-assemblages when faced with an interior column loss. Also the flexibility of the beams in terms of height to span ratio which is directly correlated with compressive arch action and catenary action mechanisms is not directly emphasized. To this aim, four RC frame sub-assemblages of constant span lengths and different beam dimensions and reinforcement ratios were designed. Built on earlier calibrated numerical models using fibre element approach, nonlinear static push-down analyses capable of accurately simulating structural response to large deformations were performed for the four frame sub-assemblages with different beam designs. The study demonstrates that the beam design influence is significant as it completely changes the progressive collapse resistance and behavior of su...
Predicting reinforced concrete (RC) framed structure resistance to progressive collapse as a resu... more Predicting reinforced concrete (RC) framed structure resistance to progressive collapse as a result of column removal scenario has recently become a necessity in the design of such structures. Such removal leads to large deformations impairing the functional performance of the structure. To predict the progressive collapse resistance, most of the researchers have developed numerical models to simulate the behaviour of test frames. However, these numerical models are confined to the test frames and would need to be modified when simulating different frames. This study discusses the resistance of RC framed structure to progressive collapse due to column exclusion from the viewpoint of numerical modelling issues using fibre element approach. The numerical results using fibre element approach were compared with a reported database of ten test RC framed buildings. The study shows that developing a simple numerical model, as an alternative to destructive tests, based on the fibre element ...
This paper aims to investigate the mechanical performance of steel fiber-reinforced geopolymer co... more This paper aims to investigate the mechanical performance of steel fiber-reinforced geopolymer concrete made with fly ash and ground granulated blast furnace slag as blended aluminosilicate source material. To activate the binding phase, combinations of sodium silicate (SS) and sodium hydroxide (SH) solutions with three different molarities (8M, 10M, and 14M) were used. Steel fibers were added to the geopolymer concrete mix in varying proportions up to 3%, by volume. Constant binder, activator solution, and aggregate contents were adopted for all 13 mixes. Samples were cast and cured at ambient conditions for measuring the rheological and mechanical properties, including slump, modulus of elasticity, compressive strength, tensile splitting strength, and flexural strength. Experimental test results show that geopolymers made with higher molarity of SH were less workable but had improved mechanical performance. The effect of adding steel fibers on the mechanical performance was more a...
The selection of an efficient mitigation technique from a number of alternatives to reduce the se... more The selection of an efficient mitigation technique from a number of alternatives to reduce the seismic risk of pre-seismic code school buildings is the main focus of this study. An on-ground survey of the school building stock in a large study area that extends for 6000 km2 enabled the selection of four different benchmark structures. Detailed simulation models are developed for the selected benchmark buildings and 14 retrofit alternatives to define their performance criteria and assess their seismic vulnerability. The earthquake hazard of the study region is accounted for using a wide range of ground motions, representing two seismic scenarios pertinent to several medium seismicity regions. The relative seismic performance of pre-code buildings and different mitigation alternatives from a large number of dynamic response simulations up to collapse is described in terms of fragility curves as well as a proposed measure of response termed the overall performance factor. This measure ...
International Journal of Protective Structures, 2016
Recent guidelines have addressed provisions to improve structure integrity to accommodate progres... more Recent guidelines have addressed provisions to improve structure integrity to accommodate progressive collapse due to failure of an interior support. This article presents novel technique and numerical model to enhance and evaluate reinforced concrete frame robustness to progressive collapse triggered by an interior or edge column failure in any floor. The presented technique enhances the structure robustness to progressive collapse by providing sufficient ductility, continuity, and redundancy. The technique involves placing external unbounded steel cables attached to the continuous beam in each floor at anchorage and deviator locations to bridge over a damaged column of any floor of the frame. The cables transfer the loads above the failed column to the anchorages and deviators that are assumed to perform as rigid arms, which in turn redistribute the loads to adjacent columns. The numerical model computes the frame building progressive collapse robustness using push-down analysis t...
Steel structures are widely used for buildings due to the advantages of high strength, good ducti... more Steel structures are widely used for buildings due to the advantages of high strength, good ductility and fast fabrication and erection. However, unprotected steel structures suffer serious damage or even collapse in a fire disaster due to the progressive deterioration in both strength and stiffness of structural steel with increasing of temperature. To protect life and reduce fire damage to property and financial loss, a steel structure must be designed to have the ability to sustain the applied design loads without the occurrence of excessive deflection or even failure in structural members for a specified period of time in the case of a fire. In this paper, the Improved Applied Element Method (IAEM), which was originally developed as an effective analysis technique of large-scale structures up to complete failure under different hazard loads, has been progressively developed to carry out modeling the behavior of plane frame steel structures in fire. The paper presents the methodo...
The numerical modeling of structures is a widely preferable approach to investigate the structura... more The numerical modeling of structures is a widely preferable approach to investigate the structural behavior of RC beams since it delivers inexpensive predictions for confirming the required goals concurrently with reducing casting, testing time, and effort. Shear-strengthening of reinforced concrete (RC) beams using externally bonded (EB) fiber-reinforced polymers (FRPs) has attracted much attention due to the fact that the FRP strengthening technique has the ability to alter the distribution of stresses between the structural elements and increase the load-carrying capacity. A significant number of experimental studies have been carried out to test the monotonic behavior of FRP shear-strengthened RC beams. Conversely, limited numerical research has been performed to investigate such performance. The VecTor2 software is developed based on the modified compression field theory (MCFT) and is directed to examine the monotonic behavior of retrofitted specimens using fiber-reinforced polymer (FRP) composites. To the authors’ knowledge, the behavior of FRP shear-strengthened beams has not been explored in the literature using the MCFT modeling approach. The main objective of this study is to detect the software’s capability of predicting the experimental outcomes of FRP shear-strengthened RC beams. This research study is carried out in two stages. Initially, the numerical study involves the development of an accurate finite element model to simulate the control specimens. The quality of this model is assessed by comparing the numerical results with the experimental outcomes. In the second phase of the numerical study, the control …
Progressive collapse of reinforced concrete (RC) building due to column failure can cause human c... more Progressive collapse of reinforced concrete (RC) building due to column failure can cause human casualties and severe irreparable damage or total collapse of the building. Different methods have been presented to mitigated progressive collapse of RC buildings; however, most of them are installed externally after construction and are costly, demanding, and require manufacturing mitigating elements such as steel cables, steel devices, or composites. This study presents an innovative mitigating scheme to improve the progressive collapse resistance of such buildings. The proposed scheme applies during construction and comprises of adding short wasted leftover steel bars from the construction site with special configuration in the slab around potential failed interior column. To examine the effectiveness of the proposed scheme, three-dimensional nonlinear fiber element-based model was developed, validated, and utilized for the analysis of such buildings. The findings of the study show that the proposed scheme improved progressive collapse behavior of the building with a percentage increase in total dissipated energy up to 241.8%. The scheme is eco-efficient and cost effective as it requires minimum amount of material, saves energy required to produce new steel bars, and can serve as an effective solution to mitigate progressive collapse of RC buildings subjected to column failure.
One of the factors that lead to potential progressive collapse of structures is removal of a load... more One of the factors that lead to potential progressive collapse of structures is removal of a load-bearing element such as a column. In this paper, a technique and a numerical procedure are presented for mitigation and evaluation of potential progressive collapse of reinforced concrete continuous beams following removal of interior columns. The procedure presented for mitigating progressive collapse proposes the use of external unbounded Fiber reinforced plastic (FRP) cables attached to the beam at anchorage locations and deviators/ saddle point(s) only, without being posttensioned. The cables will be in effect when excessive vertical displacements and deformations occur in the mitigated beam due to removal of the interior column support of the beam. The proposed numerical model evaluates the progressive collapse of such beams using a push-down analysis to simulate column removal. It assumes that the anchorage and deviator locations of the external cables act as rigid arms that connect the external cables to the beam. Parameters such as beam cross-section shape, location(s) of deviator/saddle point(s), area and profile of the external unbounded FRP cables are considered in the proposed model. The model predicts the strength of beams mitigated by the proposed technique and evaluates the effects of the external cables on the beam ductility. Numerical results of the proposed mitigation technique obtained by the proposed numerical model are compared to those in the literature.
This paper focuses on the methodology for modeling the dynamic behavior of steel structures due t... more This paper focuses on the methodology for modeling the dynamic behavior of steel structures due to severe earthquake ground motions. The development of the Improved Applied Element Method for analyzing the entire behavior of large-scale steel structures up to total failure is briefly discussed. The main features of the method are illustrated. The presented case-studies show different collapse mechanisms of moment-resistance steel frame structure under severe ground motions. The results show high capability on simulating the observed damage of many steel structures due to recent earthquakes.
One of the factors that lead to potential progressive collapse of structures is removal of a load... more One of the factors that lead to potential progressive collapse of structures is removal of a load-bearing element such as a column. In this paper, a technique and a numerical procedure are presented for mitigation and evaluation of potential progressive collapse of reinforced concrete continuous beams following removal of interior columns. The procedure presented for mitigating progressive collapse proposes the use of external unbounded Fiber reinforced plastic (FRP) cables attached to the beam at anchorage locations and deviators/ saddle point(s) only, without being posttensioned. The cables will be in effect when excessive vertical displacements and deformations occur in the mitigated beam due to removal of the interior column support of the beam. The proposed numerical model evaluates the progressive collapse of such beams using a push-down analysis to simulate column removal. It assumes that the anchorage and deviator locations of the external cables act as rigid arms that connect the external cables to the beam. Parameters such as beam cross-section shape, location(s) of deviator/saddle point(s), area and profile of the external unbounded FRP cables are considered in the proposed model. The model predicts the strength of beams mitigated by the proposed technique and evaluates the effects of the external cables on the beam ductility. Numerical results of the proposed mitigation technique obtained by the proposed numerical model are compared to those in the literature.
International Journal of Protective Structures, 2016
Recent guidelines have addressed provisions to improve structure integrity to accommodate progres... more Recent guidelines have addressed provisions to improve structure integrity to accommodate progressive collapse due to failure of an interior support. This article presents novel technique and numerical model to enhance and evaluate reinforced concrete frame robustness to progressive collapse triggered by an interior or edge column failure in any floor. The presented technique enhances the structure robustness to progressive collapse by providing sufficient ductility, continuity, and redundancy. The technique involves placing external unbounded steel cables attached to the continuous beam in each floor at anchorage and deviator locations to bridge over a damaged column of any floor of the frame. The cables transfer the loads above the failed column to the anchorages and deviators that are assumed to perform as rigid arms, which in turn redistribute the loads to adjacent columns. The numerical model computes the frame building progressive collapse robustness using push-down analysis to simulate a column elimination and estimate the effects of cable catenary action on the frame. Two-dimensional reinforced concrete frame of six stories and four bays was adopted in the study. The numerical results demonstrate the prospect of resisting progressive collapse of reinforced concrete structures by implementing the presented technique.
Optimal finite element modelling for modal analysis of liquid storage circular tanks
Model analysis of liquid storage vertical tanks is a complex task due to fluid-structure-soil int... more Model analysis of liquid storage vertical tanks is a complex task due to fluid-structure-soil interaction. Analysis of tanks subjected to earthquake excitations using finite element modelling (FEM) has become a preferred technique. The FEM is validated by comparing its results with experimental and theoretical results in the literature. However, most finite element studies in literature do not provide enough details on the selection of the elements used. The objective of this study is to provide optimal FEM options of parameters such as element types and number of elements which best predict the tank dynamic characteristics, natural frequencies and principal mode shapes. Coupled natural frequencies in sloshing modes were obtained for various tank height-to-diameter ratios, various tank wall thicknesses and various liquid depths. The FEM predictions compared well with literature available experimental and numerical results. A set of FEM options of parameters is recommended for elastic and inelastic analysis of such tanks.
In this paper, rate type constitutive equations using the Jaumann and 2nd Piola-Kirchhoff stress ... more In this paper, rate type constitutive equations using the Jaumann and 2nd Piola-Kirchhoff stress rate are used to develop axisymmetric finite strain, elastic, closed form solutions for a variety of loading conditions. We examined several cases comprizing compression-extension loading conditions, simple shear and cavity expansion conditions. Results from small strain analyses are used to indicate strain ranges for which such analyses will provide satisfactory solutions. For all the cases examined, except simple shear, the 2rid Piola-Kirchhoff stress rate does not appear to be a suitable stress rate to describe a material which follows a rate-type constitutive equation for strains greater than about 40%. The Jaumann stress rate solution shows oscillatory shear stress for axisymmetric simple shear similar to that found earlier by many other authors for rectangular (or cuboidal) condition. Negative excess pore water pressure (suction) at the cavity wall during the expansion of a cylindrical cavity was also observed in Jaumann stress rate solution.
During the past decade, increasing attention has been focused on the design of buildings to resis... more During the past decade, increasing attention has been focused on the design of buildings to resist progressive collapse. To obtain full knowledge of the total behavior of structures under extreme loading conditions, it is essential to simulate the collapsing process and the trace of yielding, damage and deformation at each structural member. Reliable numerical models are highly required as a cost effective method of obtaining a comprehensive knowledge of the main parameters that affect the response of structures. Simulation of the collapse mechanism requires an advanced technology to accurately predict member instability, failure evaluation, rupture of member joints and impact force of the falling debris. Recently, the improved applied element method (IAEM) has been introduced to simulate the total behavior of large-scale steel towers with high accuracy and low computational effort. However, its application was limited to structures with homogeneous material. In this paper, a new improvement to the IAEM is introduced to develop a novel numerical simulation analysis of failure and collapse of RC and composite structures under hazardous loads. With the new method, structures with homogenous and nonhomogenous materials such as steel, RC and composite can be simulated with high accuracy. The proposed technique takes into account geometric and material nonlinearities. The reliability of the code is investigated by comparing its results with existing experimental and numerical results. Results show that a good agreement between the analytical and the experimental results can be obtained in a less computational time.
One of the factors that lead to potential progressive collapse of structures is removal of a load... more One of the factors that lead to potential progressive collapse of structures is removal of a load-bearing element such as a column. In this paper, a technique and a numerical procedure are presented for mitigation and evaluation of potential progressive collapse of reinforced concrete continuous beams following removal of interior columns. The procedure presented for mitigating progressive collapse proposes the use of external unbounded Fiber reinforced plastic (FRP) cables attached to the beam at anchorage locations and deviators/ saddle point(s) only, without being posttensioned. The cables will be in effect when excessive vertical displacements and deformations occur in the mitigated beam due to removal of the interior column support of the beam. The proposed numerical model evaluates the progressive collapse of such beams using a push-down analysis to simulate column removal. It assumes that the anchorage and deviator locations of the external cables act as rigid arms that connect the external cables to the beam. Parameters such as beam cross-section shape, location(s) of deviator/saddle point(s), area and profile of the external unbounded FRP cables are considered in the proposed model. The model predicts the strength of beams mitigated by the proposed technique and evaluates the effects of the external cables on the beam ductility. Numerical results of the proposed mitigation technique obtained by the proposed numerical model are compared to those in the literature.
The pertinence of the fiber element approach to enable thorough numerical investigation on the po... more The pertinence of the fiber element approach to enable thorough numerical investigation on the potential for progressive collapse of reinforced concrete (RC) frame structures owing to interior column exclusion is examined using twenty-nine RC sub-assemblages with five different test setups and three different test scales. A qualitative examination of the results reveals a good agreement between the test results and the outcomes of the fiber-element-based numerical model using the finite element package SeismoStruct. Moreover, minor discrepancies between the test and numerical data demonstrate the capability of the fiber-element-based model to accurately simulate the behavior of RC elements with various boundary conditions and scales under the context of progressive collapse. Given the costly nature of experimental research, test errors, and the lengthy testing process, the proposed numerical model based on the fiber element approach can be considered a viable option for analyzing st...
This work addresses the field of collapse analysis of steel framed structures under severed loadi... more This work addresses the field of collapse analysis of steel framed structures under severed loading conditions. Applied Element Method (AEM) is recognized as a powerful tool for analyzing the structural behavior from the early stage of loading up to total collapse. This method has been used successfully with different types of material such as reinforced concrete, soil and masonry. A new extension of this method is proposed in this paper in order to simulate large-scale steel structures. The Improved Applied Element Method (IAEM) has been presented and employed in the development of novel numerical solutions for analysis of failure and collapse of large-scale structures under different hazardous loads. A series of numerical examples, including both geometric and material nonlinearity, are used for validation of the improved method. The results indicate that the improved method is capable of accurately analyzing the ultimate load-carrying capacity of steel structures. The case study,...
This study presents numerical findings of an investigation into the effect of beam dimensions and... more This study presents numerical findings of an investigation into the effect of beam dimensions and sagging and hogging reinforcement ratios on progressive collapse response of reinforce concrete (RC) frame sub-assemblages when faced with an interior column loss. Also the flexibility of the beams in terms of height to span ratio which is directly correlated with compressive arch action and catenary action mechanisms is not directly emphasized. To this aim, four RC frame sub-assemblages of constant span lengths and different beam dimensions and reinforcement ratios were designed. Built on earlier calibrated numerical models using fibre element approach, nonlinear static push-down analyses capable of accurately simulating structural response to large deformations were performed for the four frame sub-assemblages with different beam designs. The study demonstrates that the beam design influence is significant as it completely changes the progressive collapse resistance and behavior of su...
Predicting reinforced concrete (RC) framed structure resistance to progressive collapse as a resu... more Predicting reinforced concrete (RC) framed structure resistance to progressive collapse as a result of column removal scenario has recently become a necessity in the design of such structures. Such removal leads to large deformations impairing the functional performance of the structure. To predict the progressive collapse resistance, most of the researchers have developed numerical models to simulate the behaviour of test frames. However, these numerical models are confined to the test frames and would need to be modified when simulating different frames. This study discusses the resistance of RC framed structure to progressive collapse due to column exclusion from the viewpoint of numerical modelling issues using fibre element approach. The numerical results using fibre element approach were compared with a reported database of ten test RC framed buildings. The study shows that developing a simple numerical model, as an alternative to destructive tests, based on the fibre element ...
This paper aims to investigate the mechanical performance of steel fiber-reinforced geopolymer co... more This paper aims to investigate the mechanical performance of steel fiber-reinforced geopolymer concrete made with fly ash and ground granulated blast furnace slag as blended aluminosilicate source material. To activate the binding phase, combinations of sodium silicate (SS) and sodium hydroxide (SH) solutions with three different molarities (8M, 10M, and 14M) were used. Steel fibers were added to the geopolymer concrete mix in varying proportions up to 3%, by volume. Constant binder, activator solution, and aggregate contents were adopted for all 13 mixes. Samples were cast and cured at ambient conditions for measuring the rheological and mechanical properties, including slump, modulus of elasticity, compressive strength, tensile splitting strength, and flexural strength. Experimental test results show that geopolymers made with higher molarity of SH were less workable but had improved mechanical performance. The effect of adding steel fibers on the mechanical performance was more a...
The selection of an efficient mitigation technique from a number of alternatives to reduce the se... more The selection of an efficient mitigation technique from a number of alternatives to reduce the seismic risk of pre-seismic code school buildings is the main focus of this study. An on-ground survey of the school building stock in a large study area that extends for 6000 km2 enabled the selection of four different benchmark structures. Detailed simulation models are developed for the selected benchmark buildings and 14 retrofit alternatives to define their performance criteria and assess their seismic vulnerability. The earthquake hazard of the study region is accounted for using a wide range of ground motions, representing two seismic scenarios pertinent to several medium seismicity regions. The relative seismic performance of pre-code buildings and different mitigation alternatives from a large number of dynamic response simulations up to collapse is described in terms of fragility curves as well as a proposed measure of response termed the overall performance factor. This measure ...
International Journal of Protective Structures, 2016
Recent guidelines have addressed provisions to improve structure integrity to accommodate progres... more Recent guidelines have addressed provisions to improve structure integrity to accommodate progressive collapse due to failure of an interior support. This article presents novel technique and numerical model to enhance and evaluate reinforced concrete frame robustness to progressive collapse triggered by an interior or edge column failure in any floor. The presented technique enhances the structure robustness to progressive collapse by providing sufficient ductility, continuity, and redundancy. The technique involves placing external unbounded steel cables attached to the continuous beam in each floor at anchorage and deviator locations to bridge over a damaged column of any floor of the frame. The cables transfer the loads above the failed column to the anchorages and deviators that are assumed to perform as rigid arms, which in turn redistribute the loads to adjacent columns. The numerical model computes the frame building progressive collapse robustness using push-down analysis t...
Steel structures are widely used for buildings due to the advantages of high strength, good ducti... more Steel structures are widely used for buildings due to the advantages of high strength, good ductility and fast fabrication and erection. However, unprotected steel structures suffer serious damage or even collapse in a fire disaster due to the progressive deterioration in both strength and stiffness of structural steel with increasing of temperature. To protect life and reduce fire damage to property and financial loss, a steel structure must be designed to have the ability to sustain the applied design loads without the occurrence of excessive deflection or even failure in structural members for a specified period of time in the case of a fire. In this paper, the Improved Applied Element Method (IAEM), which was originally developed as an effective analysis technique of large-scale structures up to complete failure under different hazard loads, has been progressively developed to carry out modeling the behavior of plane frame steel structures in fire. The paper presents the methodo...
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