Prevention Of Progressive Collapse Research Articles

Innovative scheme for RC building progressive collapse prevention

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.

Analysis of frames of operating metallurgical shops under reconstruction

Introduction. A large number of industrial metallurgical shops, currently in operation in Russia, were erected in 1960–1980. Nowadays, these facilities need large-scale reconstruction to improve the production procedure and to install new, high performance and environmentally friendly equipment and automated control systems. Higher capacity production requires a change in the frame behaviour and the loads acting on it, in comparison with the design ones. It should be noted that the remaining service life of the frame is coming to an end in the harsh environment of a metal factory, and therefore, it needs a major overhaul and reinforcement to ensure smooth operation under the action of new loads.
 
 Materials and methods. To ensure the most accurate evaluation of forces and displacements in the frame elements and to design its reinforcement, it is advisable to perform a 3D analysis of the frame using the finite element method. This analysis must take into account current regulatory requirements, that are much tighter than those that were in effect when the frame was designed (for example, higher standard snow load, requirements ensuring protection from progressive collapse, higher values of some reliability factors, etc.).
 
 Results. The author describes the practical analysis of the frame of converter shop No. 2 at Novolipetsk Iron and Steel Works (NLMK), which was part of a reconstruction project, that included replacement of two converters with gas exhaust ducts and construction of a fugitive emission treatment system. The calculation model was described; loads acting on the frame of the converter shop were provided; principal combinations of loads and progressive collapse prevention actions were analyzed. The analysis confirmed that the bearing capacity of some structures was insufficient, and therefore, they were to be reinforced.
 
 Conclusions. Proper analysis of the stress-strain state of the frame was made using the finite element method. The bearing capacity of the converter shop frame was analyzed, and its effective reinforcement was designed according to current standards. Further research will be focused on improving the analysis by contributing the actual stiffness of joints, evaluating actual loads and ensuring the combined action of enclosing and other non-bearing structures.

Fire resistance design of the bolted-welded hybrid composite connection in steel frame

As a key component of the steel frame, the connection is important for the behaviour of the steel frame and for the prevention of progressive collapse under fire. To investigate the fire resistance of the bolted-welded hybrid composite connection in steel frame (BWC-SF), based on a completed test, a refined finite element model of the BWC-SF with a reinforced concrete slab was established. A parametric analysis was carried out to investigate the effects of the beam end load ratio, axial compression ratio of the column, thickness of the beam web and flange, thickness of the column web and flange, thickness of the concrete slab and reinforcing bar diameter. The fire resistance of the connection improved with a decrease in the beam end load ratio and reinforcing bar diameter and with an increase in the thicknesses of the beam flange, beam web and concrete slab. The flexural capacity and stiffness of BWC-SF components, which had great effects on the fire resistance, were analysed. The flexural capacity and initial rotation stiffness calculation method of the BWC-SF at elevated temperatures were established based on the component method and verified according to the test and finite element results.

Force Transfer Mechanism and Component-Based Model of Cast-Steel-Stiffened Circular-Tube-Column Frames for Progressive Collapse Analysis

In this paper, the system response, stress redistribution, failure mode, and catenary effect of steel frames with circular tube columns and cast steel stiffener (CSS) joints under a sudden column removal scenario were revealed. Based on this force transfer mechanism analysis, a practical and computationally efficient component-based model considering catenary effects and CSS joint details with a series of springs was established and validated by a detailed solid-element method. By using this component-based model, the proper dynamic response increase factor of the CSS joint frames was investigated. The results show that the great overall stiffness and strength of the CSS limit the deformation of the column front shell. Therefore, the CSS joint frames have superior performance for progressive collapse prevention than the frames using welded joints without stiffeners. In addition, the component-based model is validated to be effective and the dynamic response increase factor of the frames with circular tube columns and CSS joints is smaller than 2.0.

Upgrading of reinforced concrete frame using novel detailing technique for progressive collapse prevention

Upgrading of reinforced concrete frame using novel detailing technique for progressive collapse prevention

Experimental study and numerical simulation analysis of the Bolted-Welded hybrid connection joint of steel frame under fire

As an important part of the steel frame structure, the bolted-welded hybrid connection joint has a significant impact on the overall behavior of the structure and the prevention of progressive collapse, especially under fire exposure. Therefore, a fire test of three specimens with bolted-welded hybrid connection joints was carried out in this paper. The effects of beam-end load ratio and concrete slab thickness on the fire resistance of bolted-welded hybrid connection joints were investigated. The connection performance and failure mechanism of this connection joint under fire exposure were revealed. The furnace temperature - time curves, the surface temperature - time curves of the components, the vertical displacement - time curves of the beam end and the column top, the joint angle - time curves, the joint angle - temperature curves, the fire resistance time, and the critical temperature were obtained. The test results show that the load ratio has a great influence on the fire resistance of the bolted-welded hybrid connection joint. With the load ratio increasing, the time for the bolted-welded hybrid connection joint to reach the fire resistance limitation is significantly shortened, and the maximum anti-arch value at the beam end is significantly reduced. The increase of concrete slab thickness improves the fire resistance of the bolted-welded hybrid connection joint, but the improvement is small. A finite element model of three bolted-welded hybrid connection joints of steel frame specimens was established using ABAQUS software. A parametric analysis of load ratio and concrete slab thickness was carried out, and the mechanical behavior and failure modes of each specimen under fire exposure were numerically simulated.

Investigation of the Occurrence of Progressive Collapse in High-Rise Steel Buildings with Different Braced Configurations

Abstract The progressive collapse phenomenon refers to a chain of damages in a structure where all or a large part of the structure is destroyed by an initial local collapse in it, which can lead to very disastrous results. Therefore, the prevention of progressive collapse has become a necessary action in the design and analysis of buildings and it is vital to investigate this topic more accurately. This study aims to present a proposed pattern in the configuration of braces at the height of a high-rise steel building for reducing the probability of progressive collapse. In this regard, the vertical displacement of 18-story structure with four scenarios of column removal and five concentric bracing patterns including V, Inverted V, X, discontinuous X-bracing at height, and a combination of Xbracing in the side spans and discontinuous X-bracing at height in the middle spans are investigated and compared. In this study, the Alternative Path Method (APM) is used based on the GSA guideline for the analysis of progressive collapse. The results of this research showed that the use of X-bracing in the side spans and discontinuous X-bracing in the middle spans in nonlinear static and dynamic analyses performed better in reducing the probability of progressive collapse than other bracing configurations. Finally, it is recommended to use discontinuous X-bracing at the height that would place the bracings in one direction and providing alternative paths for force transferring in the structure.

Upgrading of precast RC beam-column joints using innovative FRP/steel hybrid technique for progressive collapse prevention

This study aims at investigating the efficacy of using an innovative hybrid strengthening technique composed of near-surface mounted (NSM) steel rebars along with fiber reinforced polymer (FRP) sheets to prevent (or diminish) the risk of progressive collapse in precast reinforced concrete (RC) beam-column joints. The study details tests involving one control specimen that is a half-scale single-story precast RC beam-column assembly having two bays. One monolithic test specimen with continuous longitudinal beam rebars was employed for comparison. The third specimen was similar to the control one, but it was retrofitted using FRP sheets combined with NSM steel rebars within the beam-column joint zone. The base of the center column was released, and a dynamic load was applied in the vertical direction on this column for simulating the column-removal scenario of progressive collapse. The proposed strengthening technique was efficient at enhancing the peak load and dissipated energy of the upgraded specimen by about 16.9 and 12.4 times, respectively, of control precast specimen. Three dimensional (3D) finite element (FE) models that consider rate-dependent material nonlinearity and bond behavior at FRP-to-concrete interface were also devised to predict the behavior of test specimens. Good agreement was obtained between the experimental and FE results with prediction errors ranging from 0% to 4%, 1% to 17%, and 3% to 10% for peak load, center column displacement at peak load, and dissipated energy at ultimate state. The validated FE models were employed for parametric studies of practical interest for investigating the impact of different strengthening parameters on the behavior of test specimen under the middle column-loss scenario.

Investigation of Progressive Collapse Resistance Mechanism in Reinforced Concrete Beam–Column Assembly

Progressive collapse is defined as the spread of an initial local failure of a structure. This phenomenon, caused by the removal of one or more load-bearing elements, is followed by a chain of failures through the structure and ultimately leads to partial or even full collapse of an entire structure. As a result, an accurate understanding of structural behavior subjected to large displacements, caused by progressive collapse, is essential to ensure a safe structural design. In this study, the behavior of the beam–column assembly subjected to progressive collapse was investigated by using finite element software. The results were compared to those of the results published in the literature, and model validation was ensured. The progressive collapse resistance mechanisms in RC beam–column assembly as well as the effectiveness of each mechanism in progressive collapse prevention were investigated. According to the results, the four resistance mechanisms, i.e., flexural action, compressive arch action, plastic hinge formation, and catenary action, have a significant effect on structural behavior.

Research of the specific steel shells progressive collapse prevention

The article deals with coatings in the form of the specific steel shells. After a detailed analysis certain number of accidentsand collapses, these collapses can be classified as “progressive” collapse. The main purpose of the article is the developmentof design algorithms for evaluation of the stress-strain state and preventing the progressive collapse of the specific steelshells. The method of prevention progressive collapse has been developed in the form of a constructive modernization.The comparative finite-element analysis of the strained-strain state of the specific shells original models, models of discretecontinualribbed shells (with constructive upgrading) and models of solid ribbed shells has been carried out. From the analysisresults it can be concluded that the proposed modernization method can be considered as one of the possible options forpreventing progressive collapses and increasing the bearing capacity of specific steel shells.

Performance analysis and macromodel simulation of steel frame structures with beam-column joints using cast steel stiffeners for progressive collapse prevention

Progressive collapse is an important failure mechanism that must be considered in the design of critical and essential buildings. For steel moment structures, beam-column joints, which act as transportation hubs of forces, are crucial members to resist progressive collapse. This research investigated the effectiveness of beam-column joints with cast steel stiffeners (CSS) in steel moment frames for progressive collapse resistance. A computationally efficient macromodel that can be used for routine design of steel moment frame buildings with CSS was developed in this paper. The developed model, which considers the deformation of joints with CSS and the catenary action effects during progressive collapse, was validated using a 3D solid finite-element model. Subsequently, the macromodel was utilized to calculate the proper dynamic increase factor for steel moment frame structures with beam-column joints using CSS. The results show that the frame with CSS is less vulnerable to gravity-induced progressive collapse than frames with welded beam-column joints without stiffeners. The proposed macromodel is effective and a dynamic increase factor of 1.6 is suitable for dynamic progressive collapse analysis of steel moment frame structures using beam-column joints with CSS.

Experimental Investigation of Beam–Column Joints with Cast Steel Stiffeners for Progressive Collapse Prevention

AbstractA full-scale experimental study was carried out on a two-story steel frame to investigate the progressive collapse behavior of beam–column joints with cast steel stiffeners (CSS). The frame...

A new type of truss joint for prevention of progressive collapse

This paper presents a study on a new type of truss joint (Pinned-Slidable or PS joint) that is designed to maximize the function of catenary action upon a sudden member removal. The basic idea for a PS joint is such that it is fixed on the bottom chord without sliding under the design load, but can slide along the bottom chord to help distribute the unbalanced tensile forces that the catenary action generates on different bottom chord members. The sliding resistance of this joint is provided by the friction generated by the preloaded bolts and the shear resistance of a locking rod, which can be designed according to the proposed design schemes. A Warren truss with PS joints as the bottom joints (Truss-PSJ) has been designed and tested under a scenario of a sudden removal of one of its diagonal members, and the response of the structure is compared with that of an identical truss model except for its non-slidable joints (truss-PJ). Results show that significant catenary action develops in the bottom chord of the remaining structure in the process of establishing a new equilibrium state after the member removal, and the catenary action tends to generate much larger tensile forces in the bottom chord members in the mid-span than in the neighboring bottom chord members, leading to the sliding of a PS joint. By comparing the test results of truss-PSJ with those of its counterpart truss-PJ, the benefits of the PS joints have been clearly demonstrated. The sliding of the PS joint not only releases the excessive unbalanced forces between neighboring members and thus enables a fuller development of the catenary action, but also facilitates the adaptation of the remaining structure towards a new balanced state with a near-optimal deformation shape. A finite element analysis has also been conducted to confirm the above experimental observations, and to demonstrate the performance of PS joints under other progressive collapse scenarios. Furthermore, a method for determining the sliding resistance of PS joints is also proposed.

Evaluation of vierendeel peripheral frame as supporting structural element for prevention of progressive collapse

Progressive building collapse occurs when failure of a structural component leads to the failure and collapse of surrounding members, possibly promoting additional failure. Global system collapse will occur if the damaged system is unable to reach a new static equilibrium configuration. The most common type of primary failure which led to the progressive collapse phenomenon, is the sudden removal of a column by various factors. In this study, a method is proposed to prevent progressive collapse phenomena in structures subjected to removal of a single column. A vierendeel peripheral frame at roof level is used to redistribute the removed column's load on other columns of the structure. For analysis, quasi-static approach is used which considers various load combinations. This method, while economically affordable is easily applicable (also for new structures as well as for existing structures and without causing damage to their architectural requirements). Special emphasis is focused on the evolution of vertical displacements of column removal point. Even though additional stresses and displacements are experienced by removal of a structural load bearing column, the proposed method considerably reduces the displacement at the mentioned point and prevents the collapse of the structural frame.

Refined dynamic progressive collapse analysis of RC structures

Post-earthquake field investigation has revealed that if reinforced concrete (RC) structures in seismic regions were not designed to the level required by modern seismic design codes, they are vulnerable to severe damage or even progressive collapse when subjected to strong earthquakes. To gain insight into the mechanism and prevention of progressive collapse, it is imperative to develop an effective and efficient approach to capture the physical collapse of RC structures by numerical simulation. Finite element method (FEM)-based numerical simulation is one of the most widely used approaches for progressive collapse analysis, but some uncertainties still exist in its element removal algorithms. This paper refines FEM-based dynamic progressive collapse simulation for RC structures by introducing the concept of degree-of-freedom (DOF) release. With the concept, a RC beam-column element removal is a natural consequence of release of all DOFs of the element. This concept is implemented in an open-source finite element code of OpenSees. The test results of a RC beam with two ends fixed under a static load and a RC column with light transverse reinforcement under lateral pseudo-static load are first used to assess and demonstrate the advantages of the DOF release over the beam element removal. The refined progressive analysis method is then applied to a RC frame structure to demonstrate its dynamic progressive collapse with catenary effect included. Finally, a two-span continuous RC bridge with a two-column pier is taken as an example to demonstrate its flexure-shear-axial failure predicted by the proposed method.

New sacrificial cladding system for the reduction of blast damage in reinforced concrete structures

Over the past few decades, explosive devices have become the weapon of choice for many terrorist attacks. In some of these attacks, large amounts of explosives are detonated within a short distance of building structures. It has been shown that current design methods are inadequate for the prevention of progressive collapse. The protection of key elements, such as columns, is necessary to prevent this catastrophic response sufficiently. This article discusses the performance of a new sacrificial cladding that protects reinforced concrete members under blast loading. It consists of reinforced resin panels with an insulation layer. For comparison purposes, two reinforced concrete members were previously experimentally studied, a reinforced concrete column without protection and reinforced concrete column with classical steel jacketing. It can be observed from the experimental results that the new sacrificial cladding achieves an important reduction in damage and displacements.

A special reinforcing technique to improve resistance of beam-to-tubular column connections for progressive collapse prevention

This paper presents a research on two types of beam-to-tubular column connections for progressive collapse prevention. Two specimens, each comprising a central column stub and half of the beam span on both sides, were constructed to represent these two types of connections. One specimen (ST-WB), had a conventional welded flange-bolted web connection, and the other (ST-WBR), which was modified by a special reinforcing technique based on the connection detail of ST-WB, had a reinforced welded flange-bolted web connection. The specimens were subjected to a monotonically increasing vertical displacement of the central column to observe their behaviors under a central-column-removal scenario. Computational simulations of the tests were carried out using detailed finite element models. The analyses provided insights into the behaviors and failure modes of the connections, including their capacities to carry the tensile forces that developed in the beams. Both the experimental and computational results demonstrate that the reinforced welded flange-bolted web connection can make the bottom flange continue to transfer force effectively after the weld failure, which is beneficial to the continuous development of axial tensile forces in the beams. As a result, the assembly with the reinforced welded flange-bolted web connection can provide a greater vertical resistance under a column removal scenario. Based on above observations, the reinforced welded flange-bolted web connection is proved to have a better performance in terms of strength and deformability than the conventional welded flange-bolted web connection, and the special reinforcing technique can be used to enhance structural robustness for progressive collapse prevention.

Details of H-Beam-to-RHS Column Joints with through Diaphragm for Progressive Collapse Prevention

A partial damage caused by an abnormal load could trigger progressive collapse of high rise buildings which may lead to fatal consequences. To meliorate structural robustness, two types of joint with improved connection details—modified bolted connection and retrofitted bolt-weld connection and their corresponding design methods are proposed on the basis of the conventional RHS column joint with through diaphragm. The numerical results indicate that both the modified bolted connection and the retrofitted bolt-weld connection can enhance the vertical deformation capacity of the beam-column assemblages before the force transmission failure at the bottom of connection region, which is conductive to the development of catenary action by axial force in the beams. For that reason, the beam-column assemblages can provide greater vertical carrying capacity and the two improved connection details can be used in designing and transforming structures against progressive collapse.

Progressive Collapse Resistance of Two Typical High-Rise RC Frame Shear Wall Structures

AbstractExisting research on progressive collapse of building structures mainly focuses on concrete and steel frame structures. To investigate the progressive collapse resistance of high-rise RC frame shear wall structures, two typical 15-story building models are designed with equivalent overall lateral resistance to seismic actions. However, the structural layouts in resisting the lateral forces are quite different for the two buildings. Building A is a weak wall-strong frame structure, whereas building B is a strong wall-weak frame system. Three-dimensional (3D) finite-element models of the two structures are established using fiber beam and multilayer shell elements. The progressive collapse resistances of the frames and the shear walls in both structures are evaluated under various column (shear wall) removal scenarios. Results demonstrate that there is a difference in progressive collapse prevention performance for different structural layouts. The progressive collapse resistance tends to be inadequ...

Special Issue on Analysis of Structural Failures Using Numerical Modeling

In recent years, there has been a considerable increase in the number of publications related to structural failures in buildings, as shown by the publication of specialized journals, books, and articles, not to mention the proliferation of conferences dealing with the analysis of real cases of structural failure. The importance of studying real cases is based on the need to determine the causes of failure, with the aim, for example, of providing technical assistance to insurance companies in claims cases, designing appropriate repairs, learning from the failure, and consequently preventing recurrences. It should be pointed out here that the study of structural failures has always contributed to progress in thefield of structural design and has encouraged the creation of new theories, concepts, construction details, etc. Numerical modeling, for example, by the finite-element method (FEM), has made the study of structural failures much easier. The calculation programs currently in use can carry out complex processes and have ever more user-friendly interfaces. If we add to this the capacity of existing computers, we can see that the use of complex numerical models is highly appropriate for analyzing failures in actual structures. Being able to carry out nonlinear calculationsmakes it possible to simulate structural behavior until failure occurs or until the structure itself collapses. The possibilities of nonlinear calculations include material yielding and cracking, large displacements, use of intersurface contact areas, and analysis of buckling. This special issue of the Journal of Performance of Constructed Facilities is entitled “Analysis of Structural Failures Using Numerical Modeling” and has its origin in the work of the guest editor in recent years both in his university lectures and in his professional duties as a structural engineer. It contains nine papers that describe the use of numerical models to analyze actual cases of structural failures with the aim of showing the reader how useful the technique can be in analyzing causes and clarifying the failure process. In the first paper, Bartoli and Betti analyze the cracking found to be present in the Capella dei Principi in Florence, Italy, including onsite surveys for subsequent nonlinear FEMmodeling, which make it possible to reproduce the structure’s behavior and thus arrive at the cause of the damage. In the second, Milani and Venturini analyze failure mechanisms in four masonry-built churches by means of numerical modeling with several unique characteristics, such as an analysis of the entire masonry structure, the use of the homogenization technique, and nonlinear behavior. Xu et al. study the progressive collapse of stone arch bridges. Numerical simulation consists of using three-dimensional FEM to perform a nonlinear analysis using contact algorithms in conjunction with the deactivation-element technique. The results obtained predict the actual behavior of stone arch bridges. This paper thus provides reference points for the analysis and prevention of progressive collapse in stone arch bridges. While the first three papers in the special issue deal with the failure of historical masonry structures, the fourth and fifth focus on the failure of masonry walls in two recently constructed buildings. Lourenco and Medeiros describe the failure of a long curved veneer wall, which, shortly after being built, exhibited significant out-of-plane movements, in addition to which part of the wall collapsed during the operation of dismounting sections of veneer. By using FEM, the authors are able to clarify the causes of the collapse and to assist in designing the repair work. In the fifth paper in this special issue, del Coz Diaz et al. use numerical modeling to determine the causes of the collapse of a masonry curtain wall in an industrial building attributable to wind action. An initial model is developed to consider fluid-structure interaction to determine wind loads on the wall. Using the loads obtained from the first model, a simulation of the wall collapse is carried out by FEM. The sixth and seventh papers analyze failures in two metallic structures. Augenti and Parisi analyze the collapse of a long-span steel roof that fell without warning during construction. The authors carry out FEM simulations to determine the causes including the possibility of structural buckling. Fig. 1. Jose M. Adam, Ph.D., Civil Engineer