Semi-rigid connections are widely used in steel frame structures. The bending and axial stiffness of connections have a significant influence on the mechanical performance of frame structures. However, most finite-element models of an actual project established in general finite-element software are rigid or hinge-connected for simplicity. Thus, the results are not consistent with the actual situation and may cause large errors. To estimate the influence of joint stiffness, including bending and axial stiffness, a novel numerical beam model is proposed in this paper. This method can be used for inelastic analysis with axial and bending stiffness considered separately. The accuracy of the proposed element model is first validated by comparing it with an ordinary beam element. Then, the model is used for seismic analysis of a steel frame structure, and the influence of bending stiffness on the dynamic response of a steel frame is derived. Progressive collapse analysis is conducted, and the influence of bending and axial stiffness on the mechanical behaviour of the steel frame structure during collapse is also determined. The proposed element model can consider semi-rigid joints and inelasticity at the same time with high accuracy, and it can be conveniently incorporated in general finite-element software.

This paper studies the behavior of concentrically braced frames (CBFs) and eccentrically braced frames (EBFs) under a progressive collapse scenario, by using the alternate load path method, recommended in progressive collapse guidelines. The model structure is a 10-story steel moment frame with five bays in each direction. The present study has investigated the CBF with two types of failure scenarios, each of which examines the effects of reducing the brace’s sections, and the EBF, including three types of failure scenarios, each of which investigates the effects of link beam length on structural capacity. Failure scenarios include the sudden removal of a column with one or more adjacent braces on the ground floor, which, for simplicity, is examined in a two-dimensional form in a perimeter bay of the building. The ability of the structure to absorb and withstand extra load after the sudden removal of the members in each of the states is examined, and their capacity and ductility are compared. According to the results, both EBF and CBF systems can withstand the progressive collapse. Moreover, in the CBF system, while the cross sections of braces decrease, the ductility of the CBF structure increases.

Progressive collapse analysis of composite steel frames subject to fire following earthquake

This research investigates numerically the potential failure of different framed structures after removal of a corner column. This study is directed towards the role of the joint above the removed column in terms of framed structures stability and internal forces redistribution utilizing linear static, nonlinear static and nonlinear dynamic analysis procedures. First, the preliminary linear static analysis as a part of more detailed nonlinear static and dynamic analysis to model reinforced concrete frames is performed. For nonlinear numerical models, three different moment-rotation capacity curves are considered for the joint above the removed column. These curves are taken according to FEMA 356 regulation according to the reinforcement condition at the joint location to represent normal joint, anchorage deficient joint and shear deficient joint. In linear static models, the results confirmed that, the more moment the joint can resist at the removed column location, the less moment is generated at the beam’s other end. In nonlinear static analysis, the model with normal plastic hinge properties recorded a higher carrying capacity than the model with both shear and anchorage plastic hinges. Nonlinear dynamic analysis with less assumptions offer the more representative modeling for the considered case study which is obvious from its closer perdition of internal forces and deflection compared to the reference findings.

This paper investigates the effects of the tensile catenary action on dynamic increase factor (DIF) in the nonlinear static analysis for progressive collapse of steel-frame buildings. Numerical analyses were performed to verify the accuracy of the empirical and analytical expressions proposed in the literature in cases where the catenary action is activated. For this purpose, nonlinear static and dynamic analyses of a series of steel moment frame buildings with a different number of spans and stories were carried out following the alternate path method. Different column removal scenarios were considered as separate load cases. The dynamic increase factor that approximately compensates for the dynamic effects in the nonlinear static analysis was selected so to match results from the nonlinear dynamic analysis. The study results showed that the many expressions in literature may not work in cases where the catenary stage is fully developed.

Recent studies regarding progressive collapse resistance of buildings considered only single critical column removal scenario. However, limited investigations have been conducted so far to assess multi-column removal scenarios. Hence this study is made to compare progressive collapse resistance of a multi-story building under both single and multi-column removal scenarios. An eight-storey reinforced concrete building was analyzed by using linear static analysis procedure and DCR values of the members are calculated to investigate the potential of progressive collapse as per GSA guideline. The values of DCR are compared for different cases. Comparisons of single and multi-column removal scenarios reveal that later scenarios are more critical because of their higher demand capacity ratios, and it is more critical when both corner and exterior columns are removed.

Steel reinforced concrete (SRC) frame-reinforced concrete (RC) core tube hybrid structures are widely used in high-rise buildings. Focusing on the progressive collapse behavior of this structural system, this paper presents an experiment and analysis on a 1/5 scaled, 10-story SRC frame-RC core tube structural model. The finite element (FE) model developed for the purpose of progressive collapse analysis was validated by comparing the test results and simulation results. The alternate load path method (APM) was applied in conducting nonlinear static and dynamic analyses, in which key components including columns and shear walls were removed. The stress state of the beams adjacent to the removed component, the structural behavior including inter-story drift ratio and shear distribution between frame and tube were investigated. The demand capacity ratio (DCR) was applied to evaluate the progressive collapse resistance under loss of key components scenarios. The results indicate that the frame and the tube cooperate in a certain way to resist progressive collapse. The core tube plays a role as the first line of defense against progressive collapse, and the frame plays a role as the second line of defense against progressive collapse. It is also found that the shear distribution is related to the location of the component removed, especially the corner column and shear walls.

A new method for progressive collapse analysis of steel frames

One of the most important issues discussed structural passive defense is progressive collapse. Progressive collapse occurs the sudden destruction caused by the deliberate structural member by accidents or disasters, such as earthquakes and terrorist military or operational errors and downtime has spread to adjacent organs and extended downtime for the chain is ruining a part of or the entire structure. Structural performance by identifying the key elements (elements with the greatest potential for progressive collapse) will be upgraded and strengthened them. In this paper buildings with 4,7and 12 stories of reinforced concrete moment frame with resistant system has been selected L-shaped plan. To determine the key elements, different situations Delete columns plan, is considered. For the first time, the progressive collapse by two method of the sensitivity index and load factor was evaluated and structures have been analysised nonlinear static analysis (Push Down Analysis).From of the values of the bearing capacity of the structure, sensitivity index and the load balance corresponding to the target displacement, the load factor is calculated.The Element with the maximum of sensitivity as well as the lowest load factor as a key element in determining the progressive collapse. The results in this paper show that L-shaped concrete building plan corner columns is the greatest potential for progressive collapse. Moreover, the results indicate that the structures in height, has a better performance against progressive collapse.

This paper presents the experimental and numerical investigation of the progressive collapse vulnerability of an existing steel building, Haskett Hall, on the Ohio State University campus. The building was tested by removing one of the first-story columns to observe its collapse resistance and to evaluate the effectiveness of current modeling and analysis guidelines. Progressive collapse is a relatively large partial or complete collapse of a structure due to the loss of a vertical load-carrying element—a column in this case. Few researchers have been able to conduct full-scale experiments to understand the progressive collapse mechanism. In this research, deflections and deformations of steel structural components were measured during the field experiment. Computational models and simulations were examined and compared with the experimental data from the field tests. The contribution and effects of infill walls to progressive collapse resistance of frame structures were investigated. The test data collected in this research can be used to help develop recommendations for improved procedures for progressive collapse analysis of frame buildings.

In this study, three-dimensional finite element models of transmission tower-line systems were established, analyzed and simulated wind-induced progressive collapse by birth-to-death element technique in ABAQUS/Explicit. This research provided clear step-by-step descriptions of various procedures for progressive collapse analysis of different transmission tower-line systems by wind load. The numerical simulation results demonstrated that wind-induced collapsed performance of transmission tower-line system could be simulated clearly. For the Claw-type and Stem-type double circuit transmission tower-line systems, the progressive collapse speed and path were different under the same wind loading and related to the structural topology form and material characteristics closely. Therefore, the numerical simulation of progressive collapse process was considered as a significant and necessary project.

The present paper presents a historical review associated with the research works on hull girder strength of ship and ship-shaped structures. Then, a new program is developed to determine the ultimate vertical bending moment of hull girder by applying direct method, stress distribution method, and progressive collapse analysis method. Six ships and ship-shaped structures used in the benchmark study of International Ship and Offshore Structures Congress (ISSC) in 2012 are adopted as examples. The calculation results by applying the developed program are analyzed and compared with the existing results. Finally, the roles of the developed program and its further development are discussed.

Themodern stage of modelling of behavior of reinforced concrete structures is associated with the widespread use of numerical methods. Thedistinctive paper is devoted todevelopment and numerical implementation of methods of structural analysis including progressive collapse analysis of spatial plate-shell reinforced concrete structures with allowance for physical nonlinearity, crack formation and inducedanisotropy. The relevance of the research topic is substantiated, the current status of research on this topic in Russia and abroad (including various aspects dealing with types of diagrams for modelling of reinforced concrete structures,construction of general deformation models of reinforced concrete, strength criteria for reinforced concrete structures and methods of structural analysis) is analyzed, the goals, objectives and boundaries of the study are determined, the provisions constituting scientific novelty, theoretical significance and practical significance are formulated, publications on the topic are under consideration. It should be noted that generallyfurther improvement and modifications of reinforced concrete models and their integration incontemporarysoftware systems for structural analysis remain very important. It is assumed that developing methods of analysis of reinforced concrete structures will replace multi-iterative approaches to the solution of physically nonlinear problems and move from the practically possible high-precision analysis of individual structures to the analysis of complex structural systems with allowance for various factors of physical nonlinearity and anisotropy. As a result,reliability of design solutions will increase significantly. The strength criteria used in this way, in turn, will also eliminate a number of errors in existing methods for strength analysis.

The definition of performance limit states for progressive collapse design and assessment of civil structures is an open issue and deserves special attention in view of future building codes and standards. In this study, the main findings of a multilevel sensitivity analysis are presented to characterize the progressive collapse capacity of a selected class of modern European buildings having a reinforced concrete framed structure. After that a group of capacity model properties are assumed as random variables on the basis of earlier studies, the sensitivity of both ultimate load capacity and corresponding maximum and residual drifts to the ultimate steel strain and location of column‐removal scenario is assessed. Then, the influence of the capacity model properties on maximum drift demand corresponding to a code‐compliant design gravity load is evaluated. Finally, five performance limit states associated with increasing levels of damage are introduced and the corresponding load capacity is quantified under varying capacity model properties. Analysis results indicate a high sensitivity to the ultimate steel strain, column location in plan, beam span and yield steel strength.

Progressive collapse triggered by fire induced column loss: Detrimental effect of thermal forces

ABSTRACTThe present study aims to assess the ultimate strength of a jacket offshore wind turbine support structures at different water depths. The progressive collapse analysis is carried out based on the finite element method accounting for the nonlinearities regarding material and geometry. A two-step analysis is carried out, in which at first, the axial dead loads are applied in a linear quasi-static analysis and then the resulting pre-stressed jacket support structure is analysed by a nonlinear finite element analysis in order to identify the ultimate strength. The present study employs a global strength approach so as to assess the ultimate strength of the jacket support structures consisting of several supporting modules with different stiffness. The moment–curvature relationships are presented for the jacket support structures at water depths of 40, 60 and 80 m. The effects of the thickness and leg inclination on the ultimate strength are investigated.

It is known that building structures would undergo nonlinearity during progressive collapse. Given this, modelling the nonlinear behaviour of structural members is critical for assessing their resistance. The objective of this study is to develop the nonlinear modelling parameters of reinforced concrete (RC) beams for the progressive collapse analysis. To achieve this, three types of RC moment-resisting buildings located in high, moderate, and low seismic zones in Canada are designed. Nonlinear pushdown analyses are then conducted on 27 three-dimensional finite element models using ABAQUS to examine the case that one column on the ground level is removed. Based on the analysis results, an idealized moment-rotation curve for modelling the plastic hinge in beams with different ductility is proposed. In comparison with the 2013 GSA modelling parameters, smaller chord rotations are observed from the detailed finite element analysis.

Abstract Multistory frame structures are generally simplified as single-story substructures to study their progressive-collapse resistance. In this study, a single-story substructure was investigate...

The influence of beams design and the slabs effect on the progressive collapse resisting mechanisms development for RC framed structures

Dynamic progressive collapse analysis of building structures is usually conducted under sudden column loss conditions. The time length required for disabling the failed column is defined as the rise time. The rise-time effect on the maximum dynamic response of building frames under column loss is investigated in this study. Based on the work-energy principle, an approximate analytical formulation for the maximum dynamic response is derived considering the rise-time effect. The force- and displacement-based dynamic increase factors (DIFs) of a single degree-of-freedom model and a clamped steel beam are used to assess the accuracy and validity of the proposed formulation. Analysis results indicate that the DIFs decrease with increased rise time. Also, the rise-time effect decreases with increased ductility demand. Practical application of the analytical formulation to regular building frames subjected to column loss is illustrated. Primary factors related to the extent of the rise-time effect on the column-loss response are identified for design consideration.