Composite Coupling Beams Research Articles

Seismic performance of steel plate reinforced high toughness concrete coupling beams with different steel plate ratios

Embedded steel plate reinforced concrete (PRC) coupling beams are newly introduced into the family of coupling beams to improve the seismic behavior of reinforced concrete (RC) coupling beams. However, the brittle crush and spalling of concrete in these composite members noticeably reduce their deformation performance and energy-dissipating capacity which largely deteriorate the efficiency of this combination. Considering this noteworthy shortcoming, in this paper the authors propose a novel type of composite coupling beams, which is entitled steel plate reinforced high toughness concrete (PRHTC) coupling beam. This novel member replaces the conventional reinforced concrete with the high toughness concrete (HTC) which is a sort of pseudo strain-hardening cementitious composites exhibiting quasi-ductile behaviors. This study mainly investigates the seismic performance of PRHTC deep coupling beams (span-to-depth ratio, l/h = 1.5) with various steel plate reinforcement ratios. The test results indicate that the PRHTC coupling beams exhibit a ductile flexural failure mechanism with excellent energy dissipation capability. The high toughness concrete in this composite member displays multiple cracking pattern and maintains desirable integrity. All specimens attained high-level ductility factors exceeding 5.5, survived large rotations ranging from 0.064 to 0.078 rad, manifested superior stiffness retention capacity and strength retention capacity. The steel plate ratio ranging from 4.31% to 6.47% is proven to be appropriate and effective for maintaining high ductility and rotation deformability of the PRHTC coupling beams in this paper.

Seismic Performance of Endplate Connections between Steel Reinforced Concrete Walls and Steel Beams

In recent years, a coupled composite shear wall system consisting of steel reinforced concrete (RC) composite wall piers and steel coupling beams has been widely used for lateral force resistance in super high-rise buildings in medium to high seismic zones in China. Research on the seismic behaviour of the coupled composite walls, however, has rarely been conducted. This paper presents the main experimental results of four steel beam RC composite wall subassembly specimens with endplate connections in terms of failure pattern, strength, ductility and energy dissipation. Mathematical macroscopic models are established based on the proposed mechanical and numerical techniques. The simulated load versus displacement skeleton curves and hysteretic loops are obtained and compared to experimental results. The simulation results are found to have good agreement with the experimental data, indicating the applicability of the proposed nonlinear modelling techniques.

Seismic performance of composite coupling beams with diagonal steel tubes

Reinforced-concrete (RC) coupled shear walls are an efficient earthquake-resistant system governed by the performance, especially ductility, of coupling beams connecting two or more RC walls. To enhance the performance of RC coupled walls, the coupling beams need very complicated details such as diagonal reinforcements. This paper provides the experimental results for rectangular steel tube reinforced composite coupling beams, which were tested to investigate the feasibility of introducing rectangular steel tubes as an alternative to diagonal bar groups confined by transverse reinforcement to improve constructability and save construction time. Three coupling beams with a span–depth ratio of 2·0 and specified compressive strength of 80 MPa were tested under cyclic loading. Test results showed that 80 MPa concrete and a non-shrink mortar-filled steel tube composite coupling beam exhibited stable behaviour up to a chord rotation of 3·5%. The non-shrink mortar-filled steel tubes replacing diagonal bar bundles improved the initial stiffness and energy dissipation capacity of composite coupling beams compared to the empty steel tubes. It is concluded that non-shrink mortar-filled steel tubes are a feasible option to replace diagonal bar groups confined by closely spaced hoops.

08.14: Behaviour of innovative demountable shear connectors subjected to combined shear and axial tension

ABSTRACTComposite steel‐concrete beams are being used increasingly in construction due to its benefits over beams consisting of the steel component alone. Composite steel‐concrete beams comprise of a steel component which is under tension and a concrete component which is under compression. Shear connectors at the steel‐concrete interface connect the two components together as well as resist shear forces. However, in some applications such as in composite coupling beams and infill walls, these shear connectors have to resist uplift forces in addition to shear forces. Therefore, there is a need to carry out experimental testing to investigate the performance of shear connectors under combined loading. Furthermore, the steel and concrete components of a composite beam cannot be separated without destroying the components since the shear connectors are welded to the steel beam and embedded in concrete. If the steel is to be reused, it has to be remelted which requires energy that usually comes from unsustainable sources. Hence research has been carried out on demountable shear connectors as they allow demounting and easy separation of the steel and concrete components. The performance of three types of innovative shear connectors subjected to combined shear and tensile loading was investigated experimentally. A pull‐out test was first being carried out with each type of shear connector to determine the tensile capacity of each type of shear connector. This was then followed by a series of modified push tests that were carried out to determine the interaction between shear and tension loading on each type of shear connector. Tensile capacity which had been determined from pull‐out tests was applied in increments of 25 % to each group followed by shear loading until failure of the shear connector was observed. A comparison of the results was carried out with shear‐tension relationships for traditional headed studs proposed by other researchers. Based on the experiment investigation carried out, significant reduction in shear strength was observed when tensile force was applied. Demountable headed studs had a much higher ductility than AJAX Oneside and Hollo bolts.

Seismic behavior of precast concrete coupled shear walls with engineered cementitious composite (ECC) in the critical cast-in-place regions

The seismic performance of precast reinforced concrete (RC) coupled shear walls is significantly influenced by coupling beams and the beam-to-wall joints during large deformations into plastic ranges. This study investigated the use of engineered cementitious composite (ECC) in the cast-in-place beam-to-wall joints and the upper regions of the composite coupling beams as an innovative method to improve the seismic performance of precast RC coupled shear walls. Two 1/2-scale precast coupled shear walls were tested under reversed cyclic loading and seismic behavior in terms of failure characteristic, mechanical characteristic value, load-displacement hysteresis curves, load-displacement envelope relationship, stiffness degradation, ductility and energy dissipation capacity were evaluated. Research results show that the substitution of concrete with ECC in the critical cast-in-place regions proved to be an effective method to improve the seismic performance of the two-story spatial of precast RC coupled shear walls.

Shear capacity of concrete-filled steel plate composite coupling beams

The concrete-filled steel plate (CFSP) composite coupling beam is a newly developed form of coupling beam that possesses high deformation and energy dissipation capacities. In this paper, the shear capacity of concrete-filled steel plate composite coupling beams was investigated. An analytical model was proposed based on the force mechanism of the composite coupling beam and was proved to have adequate accuracy compared with the available test results. The shear capacity of the composite coupling beam was found to be governed by flexural strength, shear strength, or flexural-shear strength, depending on the material and geometrical properties of the coupling beam. By incorporating the effect of flexural-shear interaction, a unified equation was finally developed.

Numerical study of concrete-filled steel plate composite coupling beams

Concrete-filled steel plate (CFSP) composite coupled shear wall systems consisting of two or more CFSP composite wall piers connected by CFSP composite coupling beams are efficient seismic resisting systems for high-rise buildings. A nonlinear finite element model that can simulate the load–deformation behavior and local response of CFSP composite coupling beams was developed to investigate their deformation and force mechanisms. Although the beam end rotation contributes largely to the lateral displacement in the initial loading stage because of local deformations at the connection regions, the flexural and shear deformations of the coupling beam are the main contributors when the coupling beam deforms into plasticity. The ratio of flexural to shear contributions to lateral displacement is affected significantly by the beam span-to-height ratio and ratio of steel flange thickness to web thickness. The effective sectional stiffness of CFSP composite coupling beams can be taken as the sum of the full stiffness of the steel plates and a reduced stiffness provided by the concrete infill. Because of the compression resistance provided by the diagonal compression strut formed in the concrete infill, the steel web plates tend to sustain tension forces, and shear forces are sustained mainly by the web plates in the compression region. For the common coupling beams, the steel plates resist 36–76% of the shear force, and 57–82% of the beam end moment, and the remainder of the internal forces is resisted by the concrete infill.

Various Existing Methods of Coupling Beams and a New Alternative Hybrid Method

The performance of various existing methods of coupling beams is summarized, including the disadvantages and advantages. According to previous researches reporting the utilization of diagonally reinforced concrete coupling beams for deep beam is essential and is the best solution to provide adequate ductility in coupling beams. However, diagonally reinforced concrete coupling beams have difficulties in practice due to congestion of reinforcement. With the purpose of simplifying construction, an alternative approach for the design of composite coupling beams will be suggested for further studies in experimental research through the use of hybrid component, which is a combination between ordinary reinforced concrete beams that will resist the flexure and steel trusses that will resist the development of high shear in the coupling beam. The proposed method will be compared to the performance of diagonal reinforced concrete coupling beams according to guideline SNI-2847:2013.

대각철근을 갖는 고성능 섬유보강 시멘트 복합체 연결보의 이력거동 평가

병렬전단벽시스템은 경제적이고 효율적인 구조시스템이지만, 연결보의 복잡한 철근상세가 요구된다. 이를 보완하고자 ACI-318에서는 개선된 철근상세를 제안하고 있지만 과도한 횡보강근으로 현장 적용에 어려움이 따른다. 이 연구에서는 횡보강철근량을 감소시킨 대각철근을 갖는 HPFRCC 연결보 상세를 제안하고, 형상비 2.0 실험체를 통해 현행 기준에 만족하는 대각철근을 갖는 철근콘크리트 연결보와 이력거동을 비교 평가하였다. 그 결과, HPFRCC의 횡구속 효과를 확인하였고, 횡구속 철근을 기준의 1/2로 배근하고 HPFRCC로 보강한 연결보는 현행기준에 따른 연결보와 유사한 내진성능을 보였다. HPFRCC 보강을 통해 대각보강된 철근콘크리트 연결보의 횡구속 철근량을 감소시킴으로써 철근상세의 단순화가 가능할 것으로 판단된다.

Concrete filled steel plate composite coupling beams: Experimental study

This paper presents an experimental study on the concrete filled steel plate composite coupling beams to evaluate and improve their seismic behavior. Six coupling beam specimens with varying span-to-height ratio, steel plate thickness and bending-to-shear capacity ratio were subjected to reversed cyclic loading. The progression of limit states began with the fracture of the steel plates at the beam corners which gradually propagated to the middle of the steel webs and steel flanges. There was limited increase in the shear capacity of the coupling beams after fracture initiated. Two local buckling phenomena including compression local buckling at the beam ends and shearing buckling of the steel webs were observed. No compression failure phenomena were observed in the infill concrete, and the concrete crack patterns were consistent with the deformation of steel plates. The deformation capacity of specimens without butt welds in the connection between the coupling beam web and the shear wall was shown to be larger than that of the specimens with butt welds at that location. Stable and full hysteretic behavior was developed by the coupling beams, indicating stable energy dissipation capability.

Internal force and deformation of concrete-filled steel plate composite coupling beams

Two or more steel plate composite shear walls connected with steel plate composite coupling beams are an efficient system for resisting seismic forces. Based on test results from six concrete-filled steel plate composite coupling beam specimens, the internal force and deformation responses of the composite coupling beams are studied in this paper. At the onset of yielding in steel web plates, the shear forces were between 61% and 76% of the corresponding maximum shear capacities. The increase in shear capacity after the steel plates yielded was primarily attributed to the increase of concrete stresses along a diagonal compression strut. It was shown that the neutral axis in the steel shifted toward the compression face as the concrete compression strut gained strength. The steel and concrete both resisted shear and moment with the steel plates sustaining approximately 50% and 70% of the maximum shear force and associated bending moment, respectively. Besides the flexural and shear deformations of the coupling beam, the beam end rotations caused by the local deformations at the connection regions and steel plate fractures at the beam ends were significant. By decomposing the contributions of each to the lateral displacement of the coupling beam, it was found that end rotations and shear deformations were the largest contributors to displacement for long and short coupling beams, respectively.

The Seismic Behavior of Pseudo Strain-Hardening Cemetitious Composites Coupling Beams with Polyvinyl Alcohol Fiber

This paper addresses the seismic behavior of pseudo strain hardening cementitious composite (PSH2C) coupling beams with different failure modes in hybrid coupled shear wall. Test variables included the ratio of steel coupling beam strength to beam-wall connection strength. The results show that Specimen PSH2C-SCF exhibits a better stable behavior in comparison with Specimens PSH2C-SBVRT and PSH2C-FCF.

Research Status on Seismic Performance of Steel-Concrete Composite Coupling Beam

Coupling beams of coupled shear wall system in seismic regions are required to have high load resisting capacity and excellent ductility and energy-dissipation capacity. To achieve this goal, the concept of steel-concrete composite coupling beam is proposed. The steel-concrete composite coupling beam is a new form and worthwhile to research and promote. Further, it is a new direction for the future development of the coupling beam. But there is a lack of specific calculation method and constructional measures in the current related codes. In this paper, the review of available literatures is made including the experimental study and influence factors of mechanical behavior. It works that have not yet been covered after summarizing each research methods and research contents, which will provide scientific reference material for the intensive research on steel-concrete composite coupling beam.

불연속웨브가 도입된 프리스트레스트 합성연결보에 대한 내진성능 평가

The shear wall system with coupling beams has been known as an effective means for moderate and high rise buildings up to 40 stories, because this structural system can provide the enhanced lateral stiffness compared to individual shear walls. Typical reinforced concrete coupling beams have difficulties in construction due to complicated reinforcing work on site, and steel coupling beams also have disadvantages in economical point of view because of a large number of stiffeners required for its stability under lateral loading. To overcome these disadvantages in existing coupling beam systems, this study developed the prestressed composite coupling beam with discontinuous webs, which have improved constructability, economic feasibility, and reduced sectional size. The reversed cyclic loading test on two prestressed composite coupling beams with discontinuous webs having different shear reinforcement ratios have been conducted to investigate their structural performances, and test results showed that the proposed composite coupling beams had good seismic performances.

Behaviour of Plate Anchorage in Plate-Reinforced Composite Coupling Beams

As a new alternative design, plate-reinforced composite (PRC) coupling beam achieves enhanced strength and ductility by embedding a vertical steel plate into a conventionally reinforced concrete (RC) coupling beam. Based on a nonlinear finite element model developed in the authors' previous study, a parametric study presented in this paper has been carried out to investigate the influence of several key parameters on the overall performance of PRC coupling beams. The effects of steel plate geometry, span-to-depth ratio of beams, and steel reinforcement ratios at beam spans and in wall regions are quantified. It is found that the anchorage length of the steel plate is primarily controlled by the span-to-depth ratio of the beam. Based on the numerical results, a design curve is proposed for determining the anchorage length of the steel plate. The load-carrying capacity of short PRC coupling beams with high steel ratio is found to be controlled by the steel ratio of wall piers. The maximum shear stress of PRC coupling beams should be limited to 15 MPa.

Study on Seismic Performance of Connection of Hybrid Coupled Wall System

Based on the state-of-the-art of the research on connection of steel coupling beam to shear wall, The steel coupling beam has satisfactory seismic performance which is better than reinforced concrete coupling beams and composite coupling beams. In this paper, the existing research results were summarized and some views were put forward. It was useful to develop a seismic design method for hybrid coupled walls in China.

Seismic performance of pseudo strain-hardening cementitious composite coupling beams with different reinforcement details

The strength, stiffness, and ductility of coupling beams may significantly affect the seismic behavior of a coupled wall system. Therefore, coupling beams must be stiff and must possess strength, stiffness, and ductility capacities to spread inelastic deformations over the height of the coupled wall system under cyclic loading. Recently, the development of a new generation of pseudo strain-hardening materials that exhibit strain-hardening characteristics in tension has opened a new range of structural applications such as plastic hinge regions of structural members, coupling beams, structural wall, beam–column connections, connections for precast member, and seismic repair of structures. This paper addresses the seismic performance of pseudo strain-hardening cementitious composites (PSH2C) coupling beams, which have different details such as convention reinforcement, diagonal reinforcement or an embedded steel plate. The results show that the use of PSH2C coupling beams exhibit a better hysteretic response than conventional RC coupling beams.

Plate-strengthened deep reinforced concrete coupling beams

Many old reinforced concrete buildings in developed countries need to be strengthened due to the aging of construction materials, changes in functional use or new design loading requirements. In the present study, a series of experiments were conducted attempting to retrofit deep reinforced concrete coupling beams using a bolted steel plate. In addition to the control specimen, the other specimens were bolted with a steel plate on the side face to improve the shear strength and inelastic behaviour. A mechanical device was added to two specimens to restrain plate buckling. The study revealed that adding an external plate is an effective way to improve the shear capacity, energy dissipation and rotation deformability of deep reinforced concrete coupling beams. Moreover, the plate buckling-restrained specimen with a sufficient number of bolts in the anchor regions had a more stable response and better inelastic performance under reversed cyclic loads. These findings can help designers to a better understanding of this type of composite coupling beam.

Shear strength of pseudo strain hardening cementitious composite coupling beam

Experimental and theoretical studies were conducted to propose an equation for predicting the shear strength of a pseudo strain hardening cementitious composite (PSH2C) coupling beam with steel fibers, polyethylene and embedded plates. The application of these fibers in structural member has been known to improve the post-cracking tensile strength of concrete, and significantly enhances the shear strength of RC beams. It is very important to quantify the post-cracking tensile strength of fibers and the contribution of embedded plate in the PSH2C coupling beams before discussing the proposed equation to predict the shear strength of the member. In particular, the post-cracking tensile strength rely on the shape of fibers, volume fraction, aspect ratio, bond stress between fibers and matrix, and the properties of the concrete matrix. For PSH2C coupling beams with a shear span-to-depth ratio (a/d) less than 2.5, the effect of shear transfer by arch action is also taken into account. The results of 71 tests of PSH2C beams were used to evaluate existing and proposed empirical equation for shear strength. The predicted values by proposed equation were in good agreement with both test results and other test data from the literature. Finally, this paper provides background for the simplified design equation to predict the shear strength of a PSH2C coupling beam with steel fibers and polyethylene.

Headed steel stud anchors in composite structures, Part II: Tension and interaction

The 2005 AISC Specification for Structural Steel Buildings is the leading specification for composite construction in the US. However, these provisions do not provide a recommendation for computing the strength of headed steel stud anchors (traditionally used as shear connectors) under tension or combined tension and shear. Headed stud anchors are subjected to these types of forces in composite structures such as infill walls, composite coupling beams, the connection region of composite columns, or composite column bases. While the ACI 318-08 Building Code, the PCI Handbook, 6th edition, and CEB Design of Fastenings in Concrete include provisions for such conditions, those provisions are geared for more general anchorage conditions than are typically seen in composite construction. It would thus be beneficial to have design guidance specifically for the case of headed steel stud anchors subjected to tension or combined tension and shear in composite construction, evaluated within the context of the AISC and EC-4 Specifications. In this work, different strength equations to compute the nominal tensile strength of a headed stud are reviewed and compared to experimental results. The resulting recommendations seek to ensure a ductile failure in the steel shank instead of a brittle failure within the concrete. Several criteria are proposed to ensure that ductile failure controls in composite construction, and, different headed stud configurations and detailing reinforcement recommendations are proposed to improve the ductile behavior of headed stud anchors subjected to tension and combined tension and shear.