Composite Coupling Beams Research Articles

A unified design approach for plate-reinforced composite coupling beams

Plate-reinforced composite (PRC) coupling beam is fabricated by embedding a vertical steel plate into a conventional reinforced concrete coupling beam to enhance its strength and deformability. Shear studs are welded on the surfaces of the steel plate to transfer forces between the concrete and the steel plate. Extensive experimental studies and numerical simulation have demonstrated the effectiveness and efficiency of this new type of coupling beam in resisting high shear force and large rotational demand from large wind or seismic loading. In this paper, an original and comprehensive design procedure is proposed to aid engineers in designing this new type of beam and to ensure proper beam detailing for desirable performance. The proposed design procedure consists of four main parts, which are (1) estimation of ultimate shear capacity of beam, (2) design of RC component and steel plate, (3) shear stud arrangement in beam span, and (4) design of plate anchorage in wall piers. Using the proposed procedure, the load-carrying capacity of the PRC coupling beams which were previously tested and simulated was evaluated. The results were compared with those from non-linear finite element analyses and experimental studies for validating the design procedure. A worked example is given to illustrate the design of PRC coupling beams using the proposed procedure.

Effects of fibre-reinforced cement composites' ductility on the seismic performance of short coupling beams

The current study examines the effects of the deformation behaviour of cementitious material ductility on the seismic performance of shear-dominant coupling beams. Matrix ductility and reinforcement layouts comprise the main testing variables. Three short coupling beams with two different reinforcement arrangements and matrices are constructed and tested. They are subjected to cyclic loading under a suitable experimental set-up. All specimens are characterised by a shear span–depth ratio of 1·0. The reinforcement layouts consist of a classical scheme and diagonal scheme without confining ties. The effects of cement-based matrix ductility on crack patterns, failure modes, hysteretic characteristics and the ultimate shear load of the coupling beams are examined. The combination of a ductile cement-based matrix and steel reinforcement is found to result in improved energy dissipation capacity, simplification of reinforcement details, and damage-tolerant inelastic deformation behaviour. Test results show that high-performance hybrid fibre-reinforced cement-based composite (HPHFRCC) coupling beams behave better than normal reinforced concrete (RC) control beams. These results are evidenced by the tensile deformation capacity, damage tolerance and tensile strength of HPHFRCC material.

Behaviour of embedded steel plate in composite coupling beams

Plate-reinforced composite (PRC) coupling beam is fabricated by embedding a vertical steel plate into a conventional-reinforced concrete coupling beam to enhance its strength and ductility. Shear studs are welded on the steel plate surfaces to allow for proper load transfer between the concrete and steel plate. The present study focuses on the evaluation of internal load distributions and load sharing on the embedded steel plate as well as at the shear studs in composite coupling beams using the nonlinear finite element package ATENA. The proposed two-dimensional finite element model is able to simulate the overall load–deflection behaviour and internal load distributions of coupling beams subjected to bending and shear forces. The reliability of the model is demonstrated by comparisons with the available experimental results. This is followed by an extensive and carefully planned parametric study using the calibrated finite element model. Numerical results on the effects of steel plate geometry, span–depth ratio of beams and steel reinforcement ratios at beam spans and in wall regions are presented and discussed in this paper. The finite element model provides a better understanding of the behaviour of shear studs as well as plate anchorage in the wall regions and embedded beam region. Based on the numerical results, equations for quantifying the shear stud forces are established and a set of non-dimensional design charts for determining the internal forces of the embedded steel plates is constructed. Both of them are useful for engineers to design PRC coupling beams.

Large-Scale Testing of a Replaceable “Fuse” Steel Coupling Beam

When coupled core wall (CCW) systems are built in regions of high seismicity, the ductility demands on the coupling beams can be of critical concern. Steel coupling beams, whether encased in concrete or not, offer a very high degree of ductility relative to common concrete coupling beams. Hybrid core wall systems, that is CCW systems with steel or steel/concrete composite coupling beams, provide excellent lateral stiffness from the walls and coupling action, while providing excellent energy dissipation and ductility characteristics of steel coupling beams. Previous research pertaining to steel coupling beams has made great strides in furthering the understanding of the behavior of steel coupling beams, and recommendations regarding design methodologies have been established. However, as steel coupling beam ends are embedded in the wall piers, postdamage repair can be costly. This paper presents the results of large-scale cyclic tests of a steel coupling beam designed and detailed based on the writers’ previous recommendations and an innovative “fuse” steel coupling beam which provides an added feature to the steel coupling beam in that postdamage repair/replacement difficulties and expenses are minimized.

Experimental study of plate‐reinforced composite deep coupling beams

AbstractAn experimental study was conducted to investigate the behavior of deep coupling beams of span‐to‐depth ratio (1·17) fabricated according to the newly proposed plate‐reinforced composite (PRC) coupling beam design. Three PRC coupling beams of small span/depth ratio fabricated based on different approaches for load transfers between steel plates and reinforced concrete (RC) were tested under reversed cyclic loading. This paper presents the experimental results and compares the overall performance of these three specimens with two geometrically identical RC coupling beam specimens, one with diagonal reinforcement and the other with conventional reinforcement details, tested by previous researchers. It was found that the performance of PRC deep coupling beams of small span‐to‐depth ratio with properly designed plate anchorage in the wall regions can be comparable to that of diagonally reinforced coupling beams while being able to achieve a higher shear capacity without causing the problem of steel congestion. The proper design approach for the plate anchorage of PRC coupling beams was also identified. Copyright © 2007 John Wiley & Sons, Ltd.

Bearing strength of steel coupling beam connections embedded reinforced concrete shear walls

In high multistory reinforced concrete buildings, coupled shear walls can provide an efficient structural system to resist horizontal force due to wind and seismic effects. Coupled shear walls are usually built over the whole height of the building and are laid out either as a series of walls coupled by beams and/or slabs or as a central core structure with openings to accommodate doors, elevator wells, windows and corridors. A number of recent studies have focused on examining the seismic response of concrete, steel, and composite coupling beams. However, since no specific equations are available for computing the bearing strength of steel coupling beam–wall connections, it is necessary to develop such strength equations. There were carried out analytical and experimental studies to develop the strength equations of steel coupling beams–concrete wall connections. Experiments were conducted to determine the factors influencing the bearing strength and to verify the strength equations of the steel coupling beam–wall connections. The proposed equations were in good agreement with both test results and other test data from the literature.

The Steel Coupling Beam-Wall Connections Strength

In high multistory reinforced concrete buildings, coupled shear walls can provide an efficient structural system to resist horizontal force due to wind and seismic effects. Coupled shear walls are usually built over the whole height of the building and re laid out either as a series of walls coupled by beams and/or slabs or a central core structure with openings to accommodate doors, elevators walls, windows and corridors. A number of recent studies have focused on examining the seismic response of concrete, steel, and composite coupling beams. However, since no specific equations are available for computing the bearing strength of steel coupling beam-wall connections, it is necessary to develop such strength equations. There were carried out analytical and experimental studies to develop the strength equations of steel coupling beam-connections. Experiments were conducted to determine the factors influencing the bearing strength of the steel coupling beam-wall connection. The results of the proposed equations were in good agreement with both test results and other test data from the literature. Finally, this paper provides background for design guidelines that include a design model to calculate the bearing strength of steel coupling beam-wall connections.

Experimental Study on Embedded Steel Plate Composite Coupling Beams

A research study has been conducted on a newly proposed design of embedded steel plate composite coupling beams with shear studs in order to improve the performance of reinforced concrete (RC) coupling beams under severe wind or earthquake loading. The experimental results on three coupling beams tested under reversed cyclic loading are discussed in this paper. One of the coupling beams was conventionally reinforced, while each of the other two contained a vertically embedded steel plate along the whole span either with or without shear studs. It was found that embedded steel plates could improve the strength and the stiffness of coupling beams, while shear studs are required to enhance the plate/RC interaction in order to achieve good inelastic performance under large imposed shear deformations. Equations for calculating the required shear connection strength in the beam span to ensure the plate/RC composite action and for estimating the available plate/RC interface slips to mobilize shear studs have been proposed.

Effects of shear connectors on plate-reinforced composite coupling beams of short and medium-length spans

Experimental studies on the newly proposed design of plate-reinforced composite (PRC) coupling beams have been carried out. Previous results have demonstrated the useful application of this design in coupling beams of medium span-to-depth ratios ( l / h ) under both inelastic seismic and elastic wind loading. This paper presents further experimental studies on five PRC coupling beams, which investigated the importance of shear connectors on plate/reinforced concrete composite action. Three medium-length ( l / h = 2.5 ) and two short ( l / h = 1.17 ) PRC coupling beams, each containing a vertically embedded steel plate, were tested under reversed cyclic loading. While one short beam was welded with expanded metal meshes on the plate surfaces, others were welded with shear studs on the plates in the wall regions and/or the beam spans. Results showed that the expanded metal meshes did not work effectively, and while the shear studs in the beam span only slightly increased the beam capacity, those in the wall regions contributed considerably in improving inelastic beam performance.

Experimental Study on Seismic Behavior of High-Performance Fiber-Reinforced Cement Composite Coupling Beams

Current design provisions in the ACI Building Code for reinforced concrete (RC) coupling beams in earthquake-resistant structures require substantial reinforcement detailing to ensure a stable seismic behavior, leading toreinforcement congestion and construction difficulties. As a design alternative, the use of high-performance fiber-reinforced cementitious composites (HPFRCCs) in coupling beams with a simplified reinforcement detailing was experimentally investigated. To validate this alternative, four coupling beam specimens were tested, including an RC control specimen detailed as per the 1999 ACI Building Code. A precast construction process was proposed for the HPFRCC coupling beams in this study. This construction alternative would lead to significant savings in time and workmanship at the job site, and provide good material quality control. Results from large-scale tests demonstrated the superior damage tolerance and stiffness retention capacity of HPFRCC coupling beams. It was also observed that diagonal reinforcement is necessary to achieve large displacement capacity. However, the transverse reinforcement around the diagonal bars was successfully eliminated due to the confinement provided by the HPFRCC material.

Strength and Ductility of Embedded Steel Composite Coupling Beams

The stringent requirements on dimensions, ductility, energy absorption, strength and stiffness of coupling beams have resulted in much research on various alternative coupling beam designs, which include the use of diagonal reinforcement, rhombic arrangement of main bars and steel composites. Experimental results showed that each of these designs offered better performance than the conventional type but had its own limitations. A new embedded steel composite coupling beam design is therefore proposed. This paper presents the findings from the experimental tests of a coupling beam fabricated with this proposed design and a conventionally reinforced coupling beam, which serves as the reference. The preliminary test results showed that the embedded steel coupling beam with relatively large span-to-depth ratio ( l/h = 2.5) had excellent shear capacity (∼10MPa) and very good energy absorption.

Steel-concrete composite coupling beams — behavior and design

Structural steel/composite beams provide a viable alternative for coupling individual reinforced concrete wall piers. Well-established guidelines for shear links in eccentrically braced steel frames form the basis of current design guidelines. However, these provisions ignore the effects of nominally reinforced concrete encasement which typically surrounds the coupling beam, and are based on overly conservative assumed deformation demands. A coordinated analytical and experimental research program at the University of Cincinnati has focused on cyclic response of steel/composite coupling beams, their connections to reinforced concrete walls, and overall behavior of composite coupled wall systems. Using the results from this study, guidelines for proper design and detailing of steel/composite coupling beams and beam-wall connections have been developed. This paper summarizes the research program, and highlights the basic concepts, important findings, and recommendations.

Concrete-Steel Composite Coupling Beams. I: Component Testing

A viable alternative to reinforced concrete coupling beams with heavily reinforced diagonal struts is steel or steel-concrete composite beams. A limited number of previous studies have examined various issues related to design of steel coupling beams. In this and a companion paper, cyclic response of steel-concrete composite coupling beams is addressed. The research results show that nominally reinforced encasement around steel coupling beams contributes to the strength and stiffness, and web stiffener plates can essentially be eliminated as the encasement provides adequate lateral stability for the shear-yielding web coupling beams. Although current design practice is conservative in terms of design and detailing of the beam, the overall behavior of composite coupling beams is not necessarily conservative. The design needs to consider the additional stiffness and strength in order to ensure proper calculation of design forces in the walls and coupling beams, and to dissipate the input energy through formation of plastic hinges in the beam and not in the connection region. Revision of current design guidelines is recommended.

Concrete-Steel Composite Coupling Beams. II: Subassembly Testing and Design Verification

As shown in a companion paper, the embedment length of steel-concrete composite coupling beams inside wall piers should be computed by incorporating the contribution of the encasement. In lieu of detailed fiber-based analytical techniques, a simple design-oriented model was developed and verified through testing of additional specimens with more realistic loading and boundary conditions. Moreover, the influence of face-bearing plates and floor slab was examined. The developed design method results in longer embedment length, and significantly enhanced energy-dissipating characteristics, strength, stiffness, and ductility. Additional improvements are possible by using face-bearing plates. The contribution of floor slab toward stiffness of the coupling beam is lost at small deformations and may be ignored. Slab participation toward the strength of the steel-concrete composite coupling beams is different from that anticipated for conventionally reinforced concrete beams because of the amount of equivalent re...

An overview of reinforced concrete core wall–steel frame hybrid structures

AbstractAn overview of a number of issues related to design of hybrid structures with reinforced concrete central core walls and perimeter steel frames is presented. Various design options for steel or steel–concrete composite coupling beams and their connections to core walls, and connections between outrigger beams and core walls are discussed. Design guidelines are presented and are evaluated with reference to previous experimental data from tests conducted by the authors. By following the recommended design procedures, it is possible to ensure satisfactory cyclic behaviour in terms of strength and energy dissipation characteristics.

Behavior and Design of Reinforced Concrete, Steel, and Steel-Concrete Coupling Beams

The efficiency of coupled wall systems to resist lateral loads is well known. In order for the desired behavior of the coupled wall system to be attained, the coupling beams must be sufficiently strong and stiff. The coupling beams, however, must also yield before the wall piers, behave in a ductile manner, and exhibit significant energy-absorbing characteristics. This paper reviews the current state of the art for the design of conventional reinforced concrete, diagonally reinforced concrete, steel, and composite steel-concrete coupling beams. Although not exhaustive, critical aspects of the design of these systems are presented.