Progressive Collapse Potential Research Articles

Technical Note: Analytical Evaluation of the Vulnerability of Framed Tall Buildings with Steel Plate Shear Wall to Progressive Collapse

In recent decades, vulnerability of tall buildings to unforeseen loads, induced by progressive collapse, has drawn researchers’ attentions. Steel plate shear walls have long been used as a lateral load-resisting system. It is composed of beam and column frame elements, to which infill plates are connected. There is a growing tendency among engineers to design tall buildings using steel plate shear walls. This paper investigates the progressive collapse-resisting capacity of the strip model of steel plate shear wall system compared with X-braced and moment frame system. The 3D models are used to assess the collapse behavior of typical 50-story building models, under sudden loss of elements from the middle and corner of the exterior frame in the story above the ground. The progressive collapse potential of model structures is evaluated by different nonlinear static and dynamic analyses using conventional analysis software. In this study, the vulnerability of candidate structures subjected to progressive collapse is also assessed by a sensitivity index regarding the sensitivity of structures to the dynamic effect induced by progressive collapse. To identify vulnerable members, the resulting actions of two nonlinear and linear static analyses are compared by the factor of redundancy related to the overall strength of the structure. Comparison of the analysis results indicated that in the steel plate shear wall system, the progressive collapse-resisting potential is more than X-braced and moment frame structure. Sensitive index of highly sensitive elements to the dynamic effect stated that in the structural models, beams are significantly more vulnerable in the moment frame than X-braced and SPSW structure. The index depicted that the vulnerability of columns in X-braced and SPSW structure is more than the moment frame structure.

Dynamic Increase Factor for Investigation of Progressive Collapse Potential in Tall Tube-Type Buildings

AbstractIn recent decades, vulnerability of tall buildings to unforeseen loads induced by progressive collapse has drawn researchers’ attentions. There is a growing tendency among engineers to design tall buildings using complicated structural systems with adventurous load paths that are inconsistent with the existing guideline recommendations. Progressive collapse is a dynamic and nonlinear phenomenon. This paper describes a recommended methodology for calculating the dynamic increase factor (DIF) to consider the dynamic effects for nonlinear static analysis. Based on this method, the specific load factor corresponding to the progressive collapse potential of building structures is evaluated by a proposed collapse index. In the development of the methodology, selected tube-type structural systems such as framed tube, braced tube, diagrid, and hexagrid systems were investigated. This study was conducted to assess the collapse behavior of typical 48-story building models under sudden loss of corner load-be...

Progressive collapse resistance of reinforced-concrete frames with specially shaped columns under loss of a corner column

To investigate the progressive collapse potential of reinforced-concrete frames with specially shaped columns subjected to the loss of a ground corner column, a static experiment on a one-third scale, 2 × 3-bay, two-storey model frame was carried out. The experiment showed that the collapse process could be divided into four stages (elastic, elasto-plastic, plastic-hinge and collapse), and the redistribution of loads was mainly observed to occur in the components adjacent to the failed column. The load-carrying capacity of the frame decreased dramatically at a rotation angle of approximately 0·06 rad at the end of the adjoining beam, indicating the start of the frame collapse. The beam resisting mechanism was identified as the major load redistribution mechanism, and the arch action in frame beams played an important role in improving the collapse-resistance capacity. A finite-element model was developed to analyse the progressive collapse-resistance performance by utilising OpenSees. The load–displacement curve obtained from the numerical analysis compared well with the experimental result. A simplified approach to evaluate the collapse-resistance capacity of the frame is proposed.

Design guides to resist progressive collapse for steel structures

The progressive collapse phenomenon in structures has been interested by civil engineers and the building standards organizations. This is particularly true for the tall and special buildings ever since local collapse of the Ronan Point tower in UK in 1968. When initial or secondary defects of main load carrying elements, overloads or unpredicted loads occur in the structure, a local collapse may be arise that could be distributed through entire structure and cause global collapse. One is not able to prevent the reason of failure as well as the prevention of propagation of the collapse. Also, one is not able to predict the start point of collapse. Therefore we should generalize design guides to whole or the part of structure based on the risk analysis and use of load carrying elements removal scenario. There are some new guides and criteria for elements and connections to be designed to resist progressive collapse. In this paper, codes and recommendations by various researchers are presented, classified and compared for steel structures. Two current design methods are described in this paper and some retrofitting methods are summarized. Finally a steel building with special moment resistant frame is analyzed as a case study based on two standards guidelines. This includes consideration of codes recommendations. It is shown that progressive collapse potential of the building depends on the removal scenario selection and type of analysis. Different results are obtained based on two guidelines.

Effect of earthquake and progressive collapse potential of rc frame structure: with and without the involvement of infill wall stiffness

Effect of earthquake and progressive collapse potential of rc frame structure: with and without the involvement of infill wall stiffness

Effect of Design Ductility on the Progressive Collapse Potential of RC Frame Structures Designed to Eurocode 8

Progressive collapse is the cause of most structural failures around the world. The US General Service Administration (GSA) has presented guidelines for the assessment of the vulnerability of building structures to progressive collapse. It has been established in literature that the philosophy of ductility and redundancy used in seismic design is beneficial in resisting progressive collapse but not accounted for in these guidelines. The GSA methodology is particularly suited to seismic codes which allows for a constant member rotation but may be unsuitable to other codes that makes provision for ductility level. In this study, an investigation into the progressive collapse potential of RC framed structures designed to the seismic design code, EC 8, with varying design ground accelerations and ductility classes under different column loss scenarios was done. Based on the EC 8, a criteria for maximum plastic rotations and dynamic multiplies for progressive collapse analysis was proposed. These proposed criteria, together with the GSA criteria, were used to investigate the designed structures. The EC 8 criteria proved that buildings designed for higher ductilities yield at lower loads but undergo greater deformations and absorbs more energy to resist collapse. On the other hand, buildings designed for lower ductilities have higher yield loads but undergo lower deformations before collapse. Higher PGAs result in higher yield strengths but does not necessarily deformation capacity. This effect of ductility was not seen with the GSA criteria since a constant rotation capacity was recommended for all the buildings regardless of design ductility. It was also found that the removals of a corner column possess the greatest threat to progressive collapse on a building.

Analysis of Steel-Concrete Composite Buildings for Blast Induced Progressive Collapse

This paper investigates the progressive collapse behaviour of steel concrete composite buildings subject to ground blast explosion using nonlinear dynamic analysis and conventional alternate path approach. The alternate path approach, which is a threat independent methodology, is commonly used as a design guide for minimising the potential for progressive collapse. This method may not be always conservative in assessing the robustness of the structure, especially for building subject to heavy blast loads and thus nonlinear analysis is often needed to investigate the building response under such extreme load. In the present paper, composite slab model based on equivalent area approach and composite joint model based on Eurocode's component method are proposed for nonlinear analysis of building framework. The analysis results show that a heavy blast load may wipe out a series of columns/beams at once instead of a single one. High blast pressure may also induce large lateral drift and lead to significant damage to structural elements spreading over several storeys of the building. Generally, such extensive damage cannot be captured using the alternate path approach. The present investigation recommends that nonlinear analysis should be performed in order to capture the true behaviour of such buildings subject to extreme blast loads.

Vulnerability of simple braced steel building under extreme load

This paper studies the behaviour of steel building under extreme load. A 10-storey steel building with a variety of lateral bracing system for a column loss is first investigated using conventional alternate path approach. The numerical study shows that the simple braced steel frames are susceptible to progressive collapse due to a column loss, due to weak column-to-beam joints compared to moment resisting frames, which have higher redundancy to redistribute the damaged column load to all other floor level. The alternate path approach, which is a threat-independent methodology, is commonly used as a design guide for minimising the potential for progressive collapse. This method may not be always conservative in assessing the robustness of the structure, especially for building subjected to heavy blast loads and thus nonlinear direct blast analysis is often needed to investigate the building response under such extreme load. The same 10-storey steel frame response is investigated for a surface blast using ...

Progressive collapse resisting capacity of reinforced concrete load bearing wall structures

Reinforced concrete (RC) load bearing wall is widely used in high-rise and mid-rise buildings. Due to the number of walls in plan and reduction in lateral force portion, this system is not only stronger against earthquakes, but also more economical. The effect of progressive collapse caused by removal of load bearing elements, in various positions in plan and stories of the RC load bearing wall system was evaluated by nonlinear dynamic and static analyses. For this purpose, three-dimensional model of 10-story structure was selected. The analysis results indicated stability, strength and stiffness of the RC load-bearing wall system against progressive collapse. It was observed that the most critical condition for removal of load bearing walls was the instantaneous removal of the surrounding walls located at the corners of the building where the sections of the load bearing elements were changed. In this case, the maximum vertical displacement was limited to 6.3 mm and the structure failed after applying the load of 10 times the axial load bored by removed elements. Comparison between the results of the nonlinear dynamic and static analyses demonstrated that the “load factor” parameter was a reasonable criterion to evaluate the progressive collapse potential of the structure.

Comparison of the Progressive Collapse Resistance of Seismically Designed Steel Shear Wall Frames And Special Steel Moment Frames

In this study, the progressive collapse potential of seismically designed steel plate shear wall (SPSW) systems is investigated using the alternate path method, and their performances are compared with those of the conventional special moment frame (SMF) systems. Nonlinear static and dynamic analyses are conducted to follow the progressive collapse of the structures, and their ability of absorbing the destructive effects of member loss is investigated. The obtained results show that when a corner or a middle column in the first story of the SPSWs is removed, the rest of the structure is not able to provide an appropriate alternative path for redistributing the generated loads caused by member loss, and therefore the structure presents a high potential for progressive collapse. However, by changing the lateral load resisting system of these buildings with the SMFs, the progressive collapse resisting capacity of the buildings increases significantly.

Threat-Independent Column Removal and Fire-Induced Progressive Collapse: Numerical Study and Comparison

Progressive collapse is defined as the spread of an initial failure from element to element, eventually resulting in the collapse of an entire structure or a disproportionately large part of it. The current progressive collapse analyses and design methods in guidelines and codes focus on the alternate load path method. This method is suitable especially in the case of blast-induced progressive collapse. In this paper, fire-induced and threat-independent progressive collapse potential is numerically investigated in steel moment resisting frames. Affecting parameters such as location of initial failure and number of floors are considered in this study. Two different mechanisms were observed in threat-independent and fire-induced progressive collapse: while in threat-independent column removal alternative load paths play major role, in fire-induced progressive collapse the weight of the structure above the failure region is the most important parameter.

ANALYTICAL ASSESSMENT ON PROGRESSIVE COLLAPSE POTENTIAL OF NEW REINFORCED CONCRETE FRAMED STRUCTURE

Progressive collapse is a catastrophic partial or total failure that mostly occurs when a structure looses a primary structural component or more like a column or any vertical load resisting component due to natural or manmade hazard. In this research paper a new undergoing construction of Reinforced concrete 12 storied building located in Whitefield, Bangalore is modelled in accordance with the actual drawings according to Indian standard codes and analysed for progressive collapse potential by using structural design and analysis software Etabs2013. For evaluating the effect of progressive collapse in accordance with the guidance of U.S General Service Administration (GSA) linear static method is followed. The analytical model is checked for Demand capacity ratio by removing primary vertical support, one column at a time and evaluating whether the member is resistance to progressive collapse. Many such columns are removed and analysed to know the behaviour of building on abnormal loading conditions. The result shows that progressive collapse can be resisted by providing proper detailing and adequate reinforcement to the beams and columns.

Progressive collapse resistance of RC beams

The current guidelines for evaluating progressive collapse potential of existing and new buildings require analyzing and evaluating the structure for the case of an instantaneous loss of a primary vertical support, such as a column. In this paper, the response of a continuous beam bridging over a lost column is evaluated. A series of beam models are developed by changing structural characteristics such as lateral load design type (ordinary vs. special frames), axial stiffness at the beam boundaries, steel yield stress, amount of integrity reinforcement at bar cut-off locations and the beam span to study their effects on the performance of the beam. The modeling technique used for the analyses of the beams has been validated by comparing experimental and analytical results of an RC beam subjected to large deformations. Push-down analyses are carried out in order to study and characterize the full range of response and compare the behavior of the beams. For each case, the behavior of the critical sections are evaluated and used to describe load transfer mechanisms. The effects of different structural characteristics on the performance of the beam to resist progressive collapse are discussed by comparing the results of the analyses.

Resistance of Flat-Plate Buildings against Progressive Collapse. II: System Response

AbstractUsing a macromodeling approach and alternate path method, dynamic and static analyses are performed to assess the progressive collapse resistance of a multistory reinforced concrete flat-plate building lacking structural integrity reinforcement in the slabs. Two loading scenarios, instantaneous removal of an exterior column and interior column, are considered. The dynamic analyses examine the potential of progressive collapse of the building, the dynamic demands on global and local nonlinear deformations, the effects of strain rate in materials, and the development of compressive membrane action. The effectiveness of an energy-based nonlinear static analysis procedure is examined for equivalently estimating the peak dynamic global and local responses caused by sudden column removal. The analyses indicate that older flat-plate buildings are vulnerable to progressive collapse; the combined effects from strain rate and compressive membrane action can significantly increase punching resistance; energy...

Progressive collapse evaluation of RC symmetric and asymmetric mid-rise and tall buildings under earthquake loads

Plan irregularity causes local damages being concentrated in the irregular buildings. Progressive collapse is also the collapse of a large portion or whole building due to the local damages in the structure. The effect of irregularity on the progressive collapse potential of the buildings is investigated in this study. This is carried out by progressive collapse evaluation of the asymmetric mid rise and tall buildings in comparison with the symmetric ones via the nonlinear time history analyses in the 6, 9 and 12 story reinforced concrete buildings. The effect of increasing the mass eccentricity levels is investigated on the progressive collapse mechanism of the buildings with respect to the story drift behavior and the number of beam and column collapsed hinges criteria. According to the results, increasing the mass eccentricity levels causes earlier instability with lower number of the collapsed hinges which is necessary to fail the asymmetric buildings and at the same time mitigates the potential of progressive collapse. Moreover, the decreasing trend of the story drifts of the flexible edges is lower than those of the stiff edges and the mass centers and the amount of decrement in the story drifts of the stiff edges is approximately similar to those of the mass centers.

Analytical and Experimental Evaluation of Progressive Collapse Resistance of a Flat-Slab Posttensioned Parking Garage

AbstractDespite the popularity of posttensioned (PT) floors for parking garages and the likelihood of a column loss, due to blast or vehicle impact, there is a lack of research on the progressive collapse potential of this structural system subsequent to initial damage. In this paper, progressive collapse resistance of an actual posttensioned parking garage is evaluated experimentally and analytically. An interior column was removed by explosion and the structure resisted progressive collapse with a permanent maximum vertical displacement of about 61 mm (2.4 in.). Analytical models of the garage are developed using computer software and nonlinear dynamic analyses are performed. The interaction between the tendon and the slab is modeled explicitly. The analytical results show that despite the fact that the slab around the removed column had no bottom reinforcement and the tendons were placed close to the top of the slab, pushing the slab down, the compressive membrane forces developed in the slab helped in...

Calculation of load increase factors for assessment of progressive collapse potential in framed steel structures

Progressive collapse of building structures is a relatively rare event. However, the consequences of progressive collapse may be catastrophic in terms of injuries and loss of lives. In addition, in many parts of the world including the United States of America, Europe, Asia, and recently, United Arab Emirates, there is a trend to build taller and more structurally complicated buildings with adventurous load paths. Therefore, structural design that takes into account the potential for progressive collapse is becoming critical. This paper outlines and discusses the process of estimating the load increase factor (LIF) needed for progressive collapse resistant design of steel building structures that takes into account the effects of component ductility on structural response following the initiation of collapse. LIF are used to account for the dynamic effects of column/wall removal when the designer opts for linear or nonlinear static analysis to assess the potential for progressive collapse. The approach recognizes the difference in response associated with deformation-controlled compared to force-controlled response quantities and structural elements. Emphasis in this paper is on the Alternate Path (AP) approach which is the most commonly used approaches for progressive collapse resistant design of building structure that fall under Occupancy Category II.

Damage Assessment of a Building Subjected to a Terrorist Attack

An increasing threat of global terrorism has led to concerns about bombings of buildings, which could cause minor to severe structural damage. After such an event, it is important to rapidly assess the damage to the building to ensure safe and efficient emergency response. Current methods of visual inspection and non-destructive testing are expensive, subjective, and time consuming for emergency responders' usage immediately after an attack. On the other hand, vibration-based damage detection methods with wireless smart sensors could provide rapid assessment of structural characteristics with low cost. For blast analysis, structural response is usually determined using a simplified SDOF version of the undamaged structure, such as used in a Pressure-Impulse (P-I) Diagram, or using more complex FEM (finite element method) models. However, the simplified models cannot take into account damage caused by blast focus at a specific location or on a specific element, which may induce local failure leading to potential progressive collapse, and the more complex FEM models take too long to derive applicable results to be effective for a rapid structural assessment. In this paper, a new method to incorporate vibration-based damage detection methods to calculate the multi degree of freedom structural stiffness for determining structural condition is provided to create a framework for the rapid structural condition assessment of buildings after a terrorist attack. The stiffness parameters are generated from the modal analysis of the measured vibration on the building, which are then used in a numerical simulation to determine its structural response from the blast. The calculated structural response is then compared to limit conditions that have been developed from ASCE blast design codes to determine the damage assessment. A laboratory-scale building frame has been employed to validate the developed use of experimentally determined stiffness by comparing the P-I diagram using the experimental stiffness with that from numerical models. The reasonable match between the P-I diagrams from the numerical models and the experiments shows the positive potential of the method. The framework and examples of how to develop a rapid condition assessment are presented.

Improved capacity spectrum method with inelastic displacement ratio considering higher mode effects

Progressive collapse, which is referred to as the collapse of the entire building under local damages, is a common failure mode happened by earthquakes. The collapse process highly depends on the whole structural system. Since, asymmetry of the building plan leads to the local damage concentration; it may intensify the progressive collapse mechanism of asymmetric buildings. In this research the progressive collapse of regular and irregular 6-story RC ordinary moment resisting frame buildings are studied in the presence of the earthquake loads. Collapse process and collapse propagation are investigated using nonlinear time history analyses (NLTHA) in buildings with 5%, 15% and 25% mass asymmetry with respect to the number of collapsed hinges and story drifts criteria. Results show that increasing the value of mass eccentricity makes the asymmetric buildings become unstable earlier and in the early stages with lower number of the collapsed hinges. So, with increasing the mass eccentricity in building, instability and collapse of the entire building occurs earlier, with lower potential of the progressive collapse. It is also demonstrated that with increasing the mass asymmetry the decreasing trend of the number of collapsed beam and column hinges is approximately similar to the decreasing trend in the average story drifts of the mass centers and stiff edges. So, as an alternative to a much difficult-to-calculate local response parameter of the number of collapsed hinges, the story drift, as a global response parameter, measures the potential of progressive collapse more easily.

Design of MR dampers to prevent progressive collapse of moment frames

In this paper the progressive collapse resisting capacity of steel moment frames with MR dampers is evaluated, and a preliminary design procedure for the dampers to prevent progressive collapse is suggested. Parametric studies are carried out using a beam-column subassemblage with varying natural period, yield strength, and damper force. Then the progressive collapse potentials of 15-story steel moment frames installed with MR dampers are evaluated by nonlinear dynamic analysis. The analysis results of the model structures showed that the MR dampers are effective in preventing progressive collapse of framed structures subjected to sudden loss of a first story column. The effectiveness is more noticeable in the structure with larger vertical deflection subjected to larger inelastic deformation. The maximum responses of the structure installed with the MR dampers designed to meet a given target dynamic response factor generally coincided well with the target value on the conservative side.