Catenary Action In Beams Research Articles

Resistance of Reinforced Concrete Frames to Progressive Collapse at Catenary Action of Beams

Resistance of Reinforced Concrete Frames to Progressive Collapse at Catenary Action of Beams

Analytical study on one-way reinforced concrete beam-slab sub-structures under compressive arch action and catenary action

In case of accidental loading, compressive arch action and catenary action in beams and slabs can be mobilised to resist progressive collapse of reinforced concrete structures. Analytical models have been proposed for reinforced concrete beam-column sub-assemblages under compressive arch action and catenary action. Nonetheless, the effects of the slab on load resistance and deformation capacity of one-way beam-slab sub-structures have not been fully investigated. This paper presents a study on the structural behaviour of one-way beam-slab sub-structures subjected to compressive arch action and subsequent catenary action. In the study, an analytical model is developed to predict the load-displacement relationship and the axial force-displacement relationship of sub-structures. The model is developed in accordance with rigid-plastic assumption. Compatibility, equilibrium and constitutive models for steel reinforcement and concrete are taken into account in the model. Hogging and sagging moments are calculated by taking moments about the plastic centres of beam-slab sub-structures. The model is validated against published test data and reasonably good accuracy is obtained in terms of the load resistances under compressive arch action and catenary action. The variation of bending moments, neutral axis depths and steel strains can also be obtained through the analytical model. The model is then used for parametric study of the effects of longitudinal reinforcement, slab width, and thickness on compressive arch action and catenary action. The parametric study shows that the cross-sectional area of longitudinal reinforcement in the slab affects the catenary action capacity and the width and thickness of the slab affects the deformation capacity of one-way beam-slab sub-structures. Finally, conclusions are drawn from the analytical study which can be used in the design of one-way beam-slab sub-structures against progressive collapse.

Collapse of steel-concrete composite frame under edge-column loss—Experiment and its analysis

Previous studies on steel frames cannot consider the effect of concrete slabs on the collapse behavior of structures, while recent experimental studies on steel-concrete composite frames fail to fully mobilize the tensile membrane action in slabs and catenary action in beams which have great influence on the failure mode of the frame. Large-scale experiments are conducted in this study on steel frames with flat concrete slabs to investigate the resistance mechanisms and typical failure modes of the structure. An edge-column removal scenario is used to consider a worse condition than an internal-column removal case. The resistance-vertical displacement relationship at the column-removal location, horizontal displacements at the structural edges and final failure patterns of main structural components are reported. Parametric studies are conducted using a validated numerical model to further quantify the effect of concrete slab thicknesses, reinforcement diameters, and beam section dimensions on the collapse resistance of composite structures. A simplified calculation method is also proposed to predict the resistance-displacement curve of composite framed structures under an edge-column loss scenario. The experimental results show that even without external horizontal restraints, tensile catenary action and membrane action can significantly develop in the steel beams and concrete slabs, respectively, at large deflections of structures under an edge-column loss scenario. Positive yield lines are found to distribute diagonally in the slab extending from the column-removal location to the two corners of the slab, while negative yield lines elliptically distribute along the edges of the slab. The numerical results highlight that the contribution of tensile membrane action in concrete slabs to the collapse resistance is less significant than that of catenary action in steel beams. Moreover, increasing the section height of beams guarantees a greater plastic bearing capacity of composite structures, but it fails to always provide a larger ultimate bearing capacity due to a poorer ductility.

Behaviour of restrained steel beam at elevated temperature – parametric studies

Purpose This paper aims to investigate computationally and analytically how different levels of restraint from surrounding structure, via catenary action in beams, affect the survival of steel framed structures in fire. This study focuses on examining the mid-span deflection and the tensile axial force of a non-composite heated steel beam at large deflection that is induced by the catenary action during exposure to fires. The study also considers the effect of the axial horizontal restraints, load-ratio, beam temperature gradient and the span/depth ratio. It was found that these factors influence the heated steel beam within steel construction and its catenary action at large deflection. The study suggests that this may help the beam to hang to the surrounding cold structure and delay the run-away deflection when the tensile axial force of the beam has been overcome. Design/methodology/approach This paper is part one of the parametric study and discusses both the effect of the axial horizontal restraints and load-ratio on the heated steel-beam. Reliance on the prescriptive standard fire solutions may lead to an unpredicted behaviour of the structure members if the impact of potential real fires is not considered. Findings Variation of the horizontal end-restraint level has a major effect on the behaviour of the beam at high deflection, and the loading on a beam at large displacement can be carried effectively by catenary behaviour. An increase of axial horizontal stiffness helps the catenary action to prevent run-away at lower deflections. The studies also investigated the influence of varying the load ratio on the behaviour of the heated beam at large deflection and how it affects the efficacy of the catenary action. The study suggests that care should be taken when selecting the load ratio to be used in the design. Originality/value In a recent work, the large deflection behaviours of axially restrained corrugated web steel beam (CWSB) at elevated temperatures were investigated using a finite element method (Wang et al., 2014). Parameters that greatly affected behaviours of CWSB at elevated temperatures were the load ratio, the axial restraint stiffness ratio and the span–depth ratio. Other works included numerical studies on large deflection behaviours of restrained castellated steel beams in a fire where the impact of the catenary action is considered (Wang, 2002). The impact of the induced axial forces in the steel beam during cooling stage of a fire when the beam temperature decreases, if thermal shortening of the beam is restrained, large tensile forces may be induced in the beam (Wang, 2005; Allam et al., 2002). A performance-based approach is developed for assessing the fire resistance of restrained beams. The approach is based on equilibrium and compatibility principles, takes into consideration the influence of many factors, including fire scenario, end restraints, thermal gradient, load level and failure criteria, in evaluating fire resistance (Dwaikat and Kodur, 2011; Allam et al., 1998).

Numerical study of progressive collapse resistance of RC beam-slab substructures under perimeter column removal scenarios

In this paper high fidelity solid-element-based numerical models are used to study the progressive collapse resistance of reinforced concrete (RC) beam-slab substructures. This is a common type of system used in RC framed structures through monolithic construction. After careful calibration of model parameters, the numerical models are validated through comparisons with test data and further employed to investigate the load transfer mechanisms and explore parameters affecting the robustness of RC beam-slab substructures under perimeter column removal scenarios. The parameters studied include lateral restraint stiffness at the substructure boundaries, loading schemes in testing, slab thickness and reinforcement detailing in slabs. The simulation results show that the progressive collapse resistance of the RC beam-slab substructures is developed primarily through compressive arch action of the longitudinal beams and flexural mechanism of the transverse beam at small deflections and catenary action of beams as well as tensile membrane action (TMA) of slabs at large deflections. The slabs enhance structural resistance through working compatibly with beams as L- and T-section “composite beams” at hogging moment regions and developing TMA. If the slabs are just simply converted into equivalent flanges of beams, the resistance at large deflections will be significantly underestimated.

Investigations of tensile membrane action in beam-slab systems under progressive collapse subject to different loading configurations and boundary conditions

Although catenary action in beams and tensile membrane action in slabs are generally believed as high-level analyses to mitigate progressive collapse in a reinforced concrete building, previous research studies did not clearly differentiate the contributions of the two mechanisms in combined three-dimensional beam-slab systems. Besides, most of the recent experimental studies on column removal scenarios focused on point load application as it is more difficult to apply the more realistic uniform distributed loads in the laboratory. In this paper, numerical analyses were first employed to investigate the combined effects of beams and slabs under both point load (idealised) and uniform distributed load (more realistic) conditions. The results show that differences between these two loading methods not only affect overall structural capacities, but also influence vertical deflections and failure modes. It is also observed that tensile membrane action in slabs was less sensitive to boundary conditions compared to catenary action in beams. Moreover, catenary action in beams which showed limited development in beam-slab structures can be conservatively neglected. Besides, under uniform distributed loading condition, scenarios with different locations of column removal were numerically investigated, showing that the loss of a penultimate column, rather than a corner column, could be the most critical case, contrary to conventional wisdom. In fact, in a corner-column removal scenario, tensile membrane action can still be partially mobilised owing to the presence of two stiff discontinuous edge beams. This phenomenon was well observed in a beam-slab test conducted in this study.

Experimental studies of 3D RC substructures under exterior and corner column removal scenarios

In a cast in-situ reinforced concrete (RC) beam-slab system, concurrent development of secondary mechanisms, i.e. catenary action in beams and tensile membrane action in slabs, may significantly increase load-carrying and deformation capacities of structures under missing column scenarios. Previous researches mainly focused on structural behaviour of individual RC beams, slabs or beam-slab systems, without clearly defining structural interactions among slabs, beams and columns. To obtain a better understanding of these complex interactions, a systematic study starting from RC skeletal frames and culminating in frame-slab systems is conducted under corner and exterior column removal scenarios, which are among the most critical scenarios for analysis of structural resistance towards progressive collapse. Four specimens were included in this programme, i.e. under corner column loss event, one skeletal frame (COR) and one frame-slab (S-COR) specimens were tested to failure, while one skeletal frame (EXT) and one frame-slab (S-EXT) specimens were loaded to collapse under exterior column loss scenario. In 3D beam-slab tests, it is very challenging to design a test setup with complete measurements of all support reactions due to a great number of statical indeterminacies. The novelty of the paper is to address this aspect. Through the proper test setup and instrumentation of structural behaviour of RC 3-D skeletal frames under corner and exterior column loss scenarios, interactions between the columns and beams could be elucidated. In turn, the slab contributions could be isolated and quantified through direct comparisons between skeletal frame and frame-slab specimens for both scenarios.

Progressive collapse analysis of steel frame structure based on the energy principle

The progressive collapse potential of steel moment framed structures due to abrupt removal of a column is investigated based on the energy principle. Based on the changes of component's internal energy, this paper analyzes structural member's sensitivity to abrupt removal of a column to determine a sub-structure resisting progressive collapse. An energy-based structural damage index is defined to judge whether progressive collapse occurs in a structure. Then, a simplified beam damage model is proposed to analyze the energies absorbed and dissipated by structural beams at large deflections, and a simplified modified plastic hinges model is developed to consider catenary action in beams. In addition, the correlation between bending moment and axial force in a beam during the whole deformation development process is analyzed and modified, which shows good agreement with the experimental results.

Influence of fire scenarios on progressive collapse mechanisms of steel framed structures

AbstractOpenSees is an open‐source object‐oriented software framework developed at UC Berkeley. The OpenSees framework has been recently extended to deal with structural behaviour under fire conditions. This paper presents the results of a numerical study, using OpenSees, of the progressive collapse of steel frames exposed to fire. After validating the capability of OpenSees against available analytical and experimental results of fire tests on steel members, a parametric study is carried out to find the progressive collapse mechanism of steel frames exposed to fire and corresponding influencing factors. The factors include load levels, lateral restraint, beam strength and fire scenarios. The catenary action of beams is considered by using a temperature‐dependent corotational beam/column element. The results show that different progressive collapse mechanisms can happen due to the sequence of the buckling of columns. High load levels lead to the downward collapse of the whole structure compared with the lateral collapse for low load levels. The existing of lateral restraint causes the premature buckling of bottom columns which triggers the whole frame collapse. As the beam section increases, the collapse mechanism of steel frames changes from beam failure mode to column failure mode. The fire scenarios have significant effect on the collapse mode of steel frames. The work presented in this paper is a preliminary study of the progressive collapse of steel frames. Further work is underway to combine the influence of the effect of concrete floors. A simple design method is then expected to be proposed to investigate the robustness of steel structures against progressive collapse due to fire.

Experimental Response of Beam-Slab Substructures Subject to Penultimate-External Column Removal

AbstractThis paper presents an experimental program to investigate the progressive collapse resistance of reinforced-concrete (RC) building structures subjected to a loss of a penultimate-external (PE) column that is the exterior one nearest to the building corner. Under this accidental scenario, any mobilization of catenary action in beams and slabs bridging over the column, as an alternative load path, should rely solely on the strength of a half perimeter compressive ring forming within the deflected slab area. Three one-third scaled beam-slab substructures were designed, built, and tested by a static loading scheme to examine the overall load capacity and displacement ductility that are two aspects of the progressive collapse resistance of RC building structures. The test variables are (1) additional amounts of beam stirrups, (2) additional beam longitudinal reinforcement, and (3) the aspect ratio of the slab panel. The boundary condition of the specimens is rotationally and vertically restrained, but...