Beam-slab Structures Research Articles

Unified analytical and design-oriented models for compressive and tensile membrane actions in RC beam-slab structures under internal column loss

Resisting mechanisms including compressive membrane action (CMA) and tensile membrane action (TMA) are critical for RC beam-slab structures against progressive collapse. However, due to the difficulties in considering the nonlinear behaviors and beam-slab interactions, limited analytical studies are currently available to accurately determine the whole resistance evolution path, let alone a simplified design model. This study presents a unified analytical model and a design-oriented simplified model to predict the whole resistance displacement of RC beam-slab substructures under internal column loss. Both equivalent uniformly distributed load (EUDL) and concentrate load (CL) conditions have been considered. In the analytical model, the beam-slab system is discretized into interior beams and multiple slab strips with consideration of their interaction. The compatibility and equilibrium conditions, curvature equations, and constitutive laws of concrete and reinforcement are incorporated to analyze each beam and slab strip. In the design model, a new strategy is proposed to decompose the structural resistance of membrane effect into summation of two components, CMA and TMA resistances, with explicit expressions. Both developed models are validated through experimental and numerical results and good agreements are achieved. Results of the analytical model show that ignoring the beam-slab interactions can lead to underestimation of structural resistance, especially during the transition from the CMA to TMA. The locations of loading points should be carefully selected to make sure 12-point loading system effective. A rule is also suggested to determine proper locations. The simplified design method gives slightly conservative predictions of structural resistance, and its calculation is easy for engineers to use.

Effect of steel reinforcement corrosion on progressive collapse resistant of beam-slab structure with interior column failure

To investigate the effect of steel reinforcement corrosion on the progressive collapse resistance of reinforced concrete (RC) structures, this study shows a methodology for establishing a finite element model (FEM) of a beam-slab structure by LS-DYNA software considering steel reinforcement corrosion. The reliability of this methodology was validated by experimental results. The analysis results indicate that considering the effect of the slab causes the beam-slab structure to enter the stages of tensile catenary action (TCA) and tensile membrane action (TMA) at smaller displacement. Moreover, as the corrosion time increases, the influence of the TCA on the structural resistance decreases. After prolonged corrosion, the top reinforcements of the beam at the failed column sides fail to fully utilize their tensile capacity when the structure fails. Furthermore, the corrosion of reinforcement significantly weakens the TCA and TMA to the structure, and neglecting the effect of the slab may lead to an overestimation of the weakening degree of the TCA caused by steel reinforcement corrosion. Additionally, the contribution of the slab's resistance in the beam-slab structure follows an "S"-shaped curve in relation to the displacement of the failed column, and the contribution of the slab to the structural resistance ranges between 40% and 60%.

Structural assessment of beam–slab reinforced concrete sub-structures under column loss scenario

Mobilisation of alternate load path (ALP) mechanisms in three-dimensional (3D) beam–slab systems is a key factor in designing structures against progressive collapse. Existing analytical methods on 3D beam–slab systems focusing on limited load-resisting mechanisms often lead to uneconomical and unrealistic design, while finite element models with 3D solid elements are too complicated and time-consuming for 3D beam–slab systems. To address these shortcomings, this paper aims to provide structural engineers with two simple but effective and reliable approaches to predict the structural behaviour of 3D beam–slab systems. They include (i) an analytical method and (ii) a simplified finite element model based on strip method and grillage analysis. Both approaches are validated against published test results for 3D beam–slab systems. Compared to existing approaches on 3D beam–slab systems, these two proposed methods incorporate all the load-resisting mechanisms in both the beams and slabs, giving more accurate and realistic predictions of load–displacement curves for the sub-structures considered. In addition, parametric studies on the analytical approach are presented to shed light on the role of boundary conditions and the contribution of slabs to the load resistance capacity of 3D beam–slab structures against progressive collapse.

Coriolis Force Sliding Mode Control Method for the Rotary Motion of the Central Rigid Body-Flexible Cantilever Beam System in TBM

Beam slab structure is often encountered in a complex tunnel boring machine. Beam slab structure is subject to dynamic load, which is easy to cause fatigue damage and affect its service life. Therefore, it is necessary to control the vibration of this kind of beam slab structure. In this study, the central rigid body-flexible beam model is established for the rotating beam and plate rotating around the y-axis. Based on the Hamilton variational principle, the dynamic equation of the central rigid body-flexible beam system is established, and the dynamic model of the central rigid body-flexible beam system considering the influence of Coriolis force and centrifugal force is given. The vibration control of the central rigid body-flexible beam system is studied. The vibration mode of the rotating Euler Bernoulli beam is determined by using the elastic wave and vibration mode theory. The influence of the rotating motion on the beam vibration is analyzed, and the variable structure control law is designed to suppress the beam vibration. Numerical simulation results show that the control method can effectively suppress the first-order and second-order vibration of the beam and verify the effectiveness of the control strategy.

Initial damage and residual behavior of RC beam-slab structures following sudden column removal - numerical study

High fidelity solid-element-based numerical models built in LS-DYNA are employed to study the progressive collapse resistance of reinforced concrete (RC) beam-slab substructures with an emphasis on the effect of initial damage caused by dynamic response from sudden removal of a column. In particular, the numerical models consider the bond-slip behavior between concrete and reinforcement in the joint regions, and incorporate element erosion in order to predict the failure modes such as reinforcement fracturing, concrete cracking and crushing. The finite element modeling is validated by experimental results in terms of both dynamic behavior following sudden column removal and residual behavior under quasi-static loading. After the validation, parametric studies are performed to investigate the influence of the equivalent gravity load and shock-induced initial acceleration. The study clearly shows that the dynamic response due to sudden column removal can induce great reduction in the progressive collapse resistance of substructures through the initial damages. The compressive arch action (CAA) and compressive membrane action (CMA) are more easily damaged by the dynamic response following sudden removal of a column, constituting less reliable load resisting mechanisms against the progressive collapse compared to the tensile catenary action (TCA) and tensile membrane action (TMA). Structures with larger applied load would suffer more from the dynamic response. Moreover, the initial upward acceleration in the event of blast or explosion is extremely unfavorable to the development of CAA and CMA by introducing transient upward movement before the downward deflection under gravity load. A comparison of the dynamic load amplification factors (DLAFs) is also made between the cases with and without significant initial damage due to dynamic response. It is concluded that ignoring the initial damage of structures can underestimate DLAF and further overestimate structural resistance, resulting in the structural design for mitigating progressive collapse in the events of explosion and impact on the unsafe side.

Flow Field Simulation When Waves Impact on Beam-plate Structures

To discuss the characteristics of flow field during wave impact, based on the software FLUENT, two-dimensional regular wave numerical models were adopted. The models could reproduce the wave impact of several typical beam slab structures, and compared with the experimental data, which verified the correctness of the model and showed the wave impact process intuitively. With simulation, the influences of wave steepness, relative clearance and relative structure width on flow field in impacting were analysed. The computational relations between the impact pressures and corresponding vertical velocities were analysed. The works are useful for mastering more mechanism of wave impact.

Earth pressure on an unloading-type sheet-pile: High-pile beam-slab wharf structure

This study analyzes a new wharf structure using a method to calculate earth pressure on a covered type sheet-pile wharf. The earth pressure on the riverside of the sheet pile and the landside of the concrete compresol pile is calculated using the earth pressure theories of Coulomb and Rankine. The earth pressure of the landside of the sheet pile and riverside of the concrete compresol pile is deduced by considering the soil arching and plate-unloading effects and a parallel walls theory. To analyze the distribution of earth pressure on the unloading sheet-pile, geotechnical-centrifuge model tests were conducted to validate the design structure of the newly reconstructed wharf structure. The test results show that the earth pressure on the riverside of the sheet pile is high at the end of the wall, decreases slightly, initially, with the increase in the depth, and then increases rapidly. However, the earth pressure on the landside of the sheet-pile initially increases to a maximum with depth and then decreases slowly with depth. With the increase in depth, the earth pressure on the riverside of the concrete compresol pile increases, while that on the landside of the concrete compresol pile first increases and then decreases.

Response of RC Beam-Slab Structure Strengthened with CFRP under Sudden Corner Column Removal Scenario

Response of RC Beam-Slab Structure Strengthened with CFRP under Sudden Corner Column Removal Scenario

Technical and economic analysis of hollow (thin wall corrugated pipe) beamless floor in underground garage

as a new type of construction technology, hollow floor without beam has been widely used in constructions. This paper studied economic efficiency of selecting hollow (thin-walled corrugated pipe) beamless floor structure system, common beam slab structure system and beamless floor structure for the roof of underground garage. Through the comparative analysis, the following conclusions are obtained: If thin wall corrugated pipe hollow beamless floor technology is used in the construction of underground garage roof, the use of construction materials and the direct cost of the projectcan will be greatly reduced.

Common Design Problems and Optimization Measures for Flat Slab Floor Structures

Compared with the traditional beam-slab structure, the flat slab floor structure has the advantages of simple load transmission path, beautiful appearance and outstanding economic benefits. It is widely used in the roof design of residential underground garages. In recent years, there have been many roof collapse accidents of underground garage in China. This makes the safety of the beamless floor become a hot topic. As a common structural form, the flat slab floor structure has the advantages of cost saving and convenient construction, but the potential risk factors for continuous collapse are more complicated than the traditional structure. Therefore, the study of the mechanical behaviour of the flat slab floor structure is very important. The article points out some common problems in the design of flat slab floor, and proposes many optimization and improvement measures, such as considering unbalanced bending moments and construction conditions, improving design methods, adding structural measures, etc.

Effects of Reinforcement Discontinuity on the Collapse Behavior of Reinforced Concrete Beam-Slab Structures Subjected to Column Removal

AbstractExisting reinforced concrete buildings constructed in low-seismic zones are most vulnerable to disproportionate collapse due to low reserve strength and presence of reinforcement discontinu...

BEHAVIOR OF RC BEAM-SLAB SUBSTRUCTURES TO RESIST PROGRESSIVE COLLAPSE

The progressive collapse resistance of RC beam-slab substructure under the loss of a penultimate side column is studied through the experimental and numerical analysis. A scaled RC beam-slab substructure is carried out in the laboratory by considering the effect of service loading during collapse. The failure modes, load redistribution mechanism, and load resisting mechanism are investigated and discussed. The experimental results showed that the beam action, compression arch action, catenary action, and tensile membrane action can be mobilized to resist the collapse of RC beam-slab structures under a penultimate column failure scenario. In the initial deformation stage, the flange effects of the slab could enhance the flexural resistance of RC beams. However, the mobilization of tensile membrane action in RC slabs is earlier than that of catenary action in RC beams. In addition, the numerical analysis based on the commercial finite element software LSDYNA showed that the floor slabs increase the yield strength and ultimate bearing capacity of a RC frame up by 65% and 61%, respectively.

Analytical Model for Tensile Membrane Action in RC Beam-Slab Structures under Internal Column Removal

An analytical approach was developed at Nanyang Technological University, Singapore, to predict structural capacities of RC beam-slab structures under the internal column removal scenario, taking into account the contribution of tensile membrane action in the slab. The model considers both commonly used loading methods in the laboratory, namely, concentrated and uniformly distributed loads. Catenary action in internal beams is neglected for conservatism, and tensile membrane action is assumed to rely solely on the yielding force of the top reinforcement arranged along negative yielding lines in the slab. The failure criterion of the model is based on fracture of longitudinal bars in internal beams, either near the middle or near the edge of beam-column joints. The proposed approach is shown to be reasonable because it provides conservative estimates compared with actual tests, which had high rotational restraints at the slab perimeter, and still gives good predictions for cases of semirigid rotational restraints.

Progressive Collapse Resistance of GFRP-Strengthened RC Beam–Slab Subassemblages in a Corner Column–Removal Scenario

In RC buildings, the unexpected sudden failure of a corner column is more likely to cause severe progressive collapse than the failure of an interior column or a side column due to the relatively weak tie force from the surrounding elements. Effective strengthening methods can improve the progressive collapse resistance of these structures. Fiber-reinforced polymer (FRP) has been widely used to retrofit RC structures due to its high strength, light weight, and corrosion resistance. In this study, the progressive collapse behaviors of glass FRP (GFRP)–strengthened RC beam–slab subassemblages under corner column removal were investigated. First, a quasi-static experimental test was adopted to study the progressive collapse resistance of the beam–slab subassemblages, including a control specimen and strengthened specimens. Two techniques applying externally bonded GFRP laminates and near-surface-mounted (NSM) GFRP bars were adopted to strengthen the subassemblages. The influences of the strengthening schemes on the behavior of the tested specimens were studied by comparing all the test results. The experimental results demonstrate that this strengthening technology can enhance the progressive collapse resistance of RC beam–slab structures. Finite-element (FE) analysis of the progressive collapse resistance of the beam–slab subassemblages was also conducted using the software package MSC Marc. The numerical model can predict the progressive collapse resistance of the subassemblages. In addition, the calculated results were used to better understand the stress distribution of the GFRP in a corner column–removal scenario.

Analytical model for predicting membrane actions in RC beam-slab structures subjected to penultimate-internal column loss scenarios

The potential for progressive collapse of RC buildings can be estimated by column loss scenarios. The loss of either internal or external penultimate columns is among the most critical scenarios since the beam-slab substructures associated with the removed column becomes laterally unrestrained with two discontinuous edges. At large deformations, membrane behaviour of the associated slabs, consisting of a compressive ring of concrete around its perimeter and tensile membrane action in the central region, represents an important line of defence against progressive collapse. The reserve capacity can be used to sustain amplified gravity loads and to mitigate the progressive collapse of building structures. In this paper, based on experimental observation of 1/4 scaled tests together with investigation of previous research works, an analytical model is proposed to predict the load-carrying capacity of beam-slab structures at large deformations. Comparison with the test results shows that the analytical model gives a good estimation of the overall load-carrying capacity of the RC slabs by membrane actions.
 Article history: Received 15 March 2018, Revised 28 March 2018, Accepted 27 April 2018

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.

A simplified approach to assess progressive collapse resistance of reinforced concrete framed structures

Progressive collapse resistance of reinforced concrete (RC) building structures can be assessed by sudden column loss scenarios. Penultimate column loss is among the most critical scenarios since it leaves the affected beam-slab systems with lack of external lateral restraints. Under such accidental situation, flexural action in the double-span beams and slabs bridging over the removed column is experimentally identified as the main mechanism to redistribute the gravity loads, which is amplified by double span effect and dynamic effect. This paper presents a simplified approach for progressive collapse assessment of RC building structures subjected to a penultimate column loss. The collapse resistance is calculated based on an idealized elastic–plastic static response of a double-span beam-slab structure, which is constructed with (i) ultimate flexural capacity of the beam-slab structure that is determined by yield-line method of analysis and (ii) displacement ductility at the removed column position that is established based on curvature ductility of a critical connection touching on the affected area. The idealized static response is validated by experimental results of 12 beam-slab sub-assemblage tests. A simple step-by-step procedure together with worked examples are provided. Practical application of this approach and design recommendations for mitigating progressive collapse are discussed.

Design and analysis of the glass fiber composite truss beam structure

To exert the corrosion-resistant characteristics of the composite materials, which have overcome the characteristics of low modulus of the truss structure design. We designed a new kind of beam-slab structure and it can be applied to the desulfurization and denitration tower. The kingpost is undertook by four successive FRP profiles and nodes connected by hough; both ends are connected by a rod with the thread structure. This research analyzed the structure of the finite element, and the result comes out that the stress, the strain and distortion of the whole kingpost, are meet regulatory requirements as well.

COMPARATIVE STUDY OF SEISMIC PERFORMANCE OF HIGH RISE 30 STOREY BUILDING WITH BEAM SLAB, FLAT SLAB AND ALTERNATE FLAT - BEAM SLAB SYSTEMS IN ZONE V

In present era, Flat slab buildings are capturing much importance and are commonly adopted for the construction. In high seismic regions, the structural efficiency of flat slab system poses a significant risk due to lowly-ductile. The collapse of the structure is due to brittle punching shear due to transfer of shearing forces and unbalanced moments between slab and columns. In the present work another model is generated by using alternate arrangement of conventional beam slab and Flat Slab building model. The performance of conventional RC Frame building, flat slab RC Frame building and alternate flat slab - beam slab building models with shear walls of G+30 storey under different load conditions were studied and for the analysis, seismic zone V is considered. The object of the present work is to study the performance of alternate flat slab – beam slab structure and compare the behaviour of three structures i.e. conventional beam slab structure, flat slab structure with that of alternate flat slab – beam slab structure under seismic loads. This paper presents good source of information on the parameters modal participation mass ratios, spectral acceleration, time period, storey drift, storey shear, column forces and shear wall forces.

The Construction Technique of the Beam Slab Structure being Filled Large-Span Prestressed Lightweight Materials

Abstract: With the rapid development of Chinese economy, more and more requirements of large public buildings, large space and has more functions, the engineering design, construction and bring many technical problems, in order to solve the technical problem, the construction of scientific research departments continue to research and development of new materials, new technology, new methods of construction, city of Puyang stadium the tennis project 44M*24M large span structure, adopts the ‘made of light material combined unit filled prestressed concrete cast-in-situ slab’ structure technology, solves the light, save steel, concrete, reduces the structure thickness, good economic practicability.