Reinforced Concrete Coupled Shear Wall Research Articles

Mechanical behavior of ECC-reinforced coupled shear wall

PurposeBased on the weak seismic performance and low ductility of coupled shear walls, engineered cementitious composites (ECC) is utilized to strengthen it to solve the deformation problem in tall buildings more effectively and study its mechanical properties more deeply.Design/methodology/approachThe properties of reinforced concrete coupled shear wall (RCCSW) and reinforced ECC coupled shear wall (RECSW) have been studied by numerical simulation, which is in good agreement with the experimental results. The reliability of the finite element model is verified. On this basis, a detailed parameter study is carried out, including the strength and reinforcement ratio of longitudinal rebar, the placement height of ECC in the wall limb and the position of ECC connecting beams. The study indexes include failure mode and the skeleton curve.FindingsThe results suggest that the bearing capacity of RECSW is significantly affected by the ratio of longitudinal rebar. When the ratio of longitudinal rebar increases from 0.47% to 3.35%, the bearing capacity of RECSW increases from 250 kN to 303 kN, an increase of 21%. The strength of longitudinal rebar has little influence on the bearing capacity of RECSW. When the strength of the longitudinal rebar increases, the bearing capacity of RECSW increases little. The failure mode of RECSW can be improved by lowering the casting height of the ECC beam in a certain range.Originality/valueIn this paper, ECC is used to strengthen the coupled shear wall, and the accuracy of the finite element model is verified from the failure mode and skeleton curve. On this basis, the casting height of the ECC casting wall limb, the strength and reinforcement ratio of longitudinal rebar and the position of the ECC beam are studied in detail.

Numerical study on optimized application of engineered cementitious composites in RC coupled shear wall structures

Due to the superior tensile strain-hardening and multi-cracking properties, engineered cementitious composites (ECC) can be adopted in reinforced concrete (RC) shear walls and coupling beams to improve the seismic performance and damage tolerance with simplified reinforcement details. This study numerically investigates the optimized application of ECC in coupled RC shear wall structures based on refined two-dimensional finite element models incorporating constitutive models of ECC and concrete for nonlinear shear behaviors. The balance between cost and performance is adequately considered from the material, member, and structural levels. At the material level, the reasonable tensile properties of ECC are suggested based on the parametric analysis of coupling beam and shear wall specimens. At the member level, the effect of diagonal bar ratios on the seismic performance of coupled walls is investigated to propose reasonable diagonal bar ratio of ECC coupling beams. Finally, at the structural level, nonlinear dynamic time-history analysis of a typical 11-story coupled wall structure based on practical engineering is conducted to investigate the influence of the application ranges of ECC on the seismic performance of the wall system. The damage indexes, including story curvature and crack width, are analyzed and compared. Based on the analytical results, recommendations related to some key issues on the application of ECC in traditional RC structures are provided, including the application range and tensile properties of ECC, as well as the reinforcement details.

Shaking table tests and numerical analysis of RC coupled shear wall structure with hybrid replaceable coupling beams

AbstractA variety of innovative structural solutions have been recently introduced to mitigate damage and expedite the repair of buildings subjected to extreme seismic events, hence contributing to the urgent need for resilient societies. In this context, the present study experimentally and numerically investigates an innovative reinforced concrete (RC) shear wall (SW) structure with replaceable coupling beams (CBs) equipped with hybrid devices. These hybrid devices couple metallic and viscoelastic dampers and aim at satisfying multiple lateral load performances effectively. To assess the seismic performance of the proposed coupled SW system and verify the design principle, comparative shaking table tests were performed on two 1/4‐scale seven‐story SW structure specimens, including a conventional RC coupled SW and the proposed coupled SW with hybrid devices. The tests results indicate the improved performance of the proposed compared with the conventional system in terms of: (1) reduced interstory drifts and story accelerations demand under a wide range of seismic intensities, (2) concentrated damage in the hybrid device and minimal damage to the other components contributing to the reparability of the structure. Furthermore, 3D finite element models for the shaking table test specimens were established in OpenSees and validated against experimental response. Successively, a numerical parametric study was conducted by performing non‐linear response history analyses under a set of 22 ground motions to investigate the influence of different design configurations of the hybrid device on the peak interstory drifts and peak story accelerations.

Nonlinear behaviour of FRP-retrofitted RC coupled shear walls

This paper presents a numerical study of the effectiveness of fibre-reinforced polymer (FRP) composites in upgrading the seismic performance of conventional reinforced concrete (RC) coupled shear walls. The study investigates the performance of two RC coupled shear wall buildings with different heights when their coupling beams are retrofitted using FRP U-wraps for increased ductility of the beams. The 10- and 15-storey existing buildings are located in Montreal, Canada, and were designed according to the 1970 National Building Code of Canada (NBCC). The FRP retrofit aims to increase the shear capacity of nominally ductile coupling beams, and hence increase their rotational ductility to the limited ductility, moderate ductility, and ductile levels. Nonlinear incremental dynamic analyses were conducted for existing and FRP-retrofitted buildings when subjected to twelve ground motion records with different frequency contents. The seismic behaviour of the analyzed cases was compared based on the maximum earthquake intensity that can be resisted by the building, maximum interstorey drift ratio, maximum storey shear, maximum coupling moment, maximum energy dissipated, and maximum wall forces. Moreover, the twelve earthquake records were scaled to match the NBCC 2015 design response spectrum of Montreal to determine the optimum retrofit level for the coupling beams of the two buildings in consideration.

Seismic Performance of a New Type of Coupled Shear Wall with Replaceable Components: Experimental Validation

ABSTRACT This study proposes a new type of reinforced concrete (RC) coupled shear wall with replaceable coupling beams and replaceable corner components (RCCs) installed at the bottom corners of wall piers. To assess the seismic performance of the new coupled shear wall and verify the proposed design methodology, four 1/2-scale specimens including one conventional RC coupled shear wall and three new coupled shear walls were tested under lateral cyclic loading. The test results indicate that compared with conventional RC coupled shear walls the seismic performance of the new coupled shear wall is significantly improved.

Numerical study of reinforced concrete coupled shear walls based on a two-dimensional finite element model

The reinforced concrete (RC) coupled shear wall is used extensively in high-rise buildings due to its extraordinary lateral resistance performance. Although massive individual RC shear wall as well as RC coupling beam specimens were tested, both the experimental and numerical studies on the seismic performance of RC coupled shear walls are insufficient. Considering the difficulties in large-scale coupled shear wall tests, finite element analysis (FEA) is carried out in this study to reveal quantitatively the effects of coupling beams with different aspect ratios and reinforcement layouts, as well as the behavior of coupling beams in the complex boundary conditions between adjacent wall piers. First, the finite element model based on a two-dimensional fixed crack constitutive model is proposed and validated by twelve coupling beam tests and the results demonstrate that buckling of diagonal bars should be reasonably considered. Then three coupled shear wall specimens are simulated, verifying the high accuracy of the proposed model. The effects of slabs on the coupled shear wall as well as coupling beams are also discussed. Finally, twenty coupled shear wall models with different degrees of coupling (DOCs) and diagonal bar ratios of coupling beams are analyzed. The results demonstrate that coupled shear walls with the diagonal bar ratio of 25–75% exhibit equivalent seismic performance with the diagonal bar ratio of 100%. In order to make full use of the energy dissipation of coupling beams, the DOC value should be no larger than 66%. With the constraint of adjacent wall piers, large axial compressive and tensile forces are induced, and their effects on the coupling beams should be considered.

Hysteretic Behavior of Conventionally Reinforced Concrete Coupling Beams in Reinforced Concrete Coupled Shear Wall

This paper presents the experimental results of four full-scale coupling beams in which only horizontal reinforcements are placed, without diagonal reinforcements, with the aim to develop reinforcement details for coupling beams used in connecting side walls in a wall-slab structural system. Each coupling beam specimen was designed according to the deep-beam design procedure that does not use diagonal reinforcements and that is found in current standards. Two cases for basic deep-beam design specimens were investigated wherein (1) U-type reinforcement was added to prevent sliding shear failure of the joints and (2) horizontal intermediate reinforcements were placed. The coupling beam specimens were fabricated with a shear span-to-depth ratio (aspect ratio) of 1.68 and were connected to walls only by horizontal reinforcements, i.e., without diagonal reinforcement. The experimental results indicate that the strength of the beams was about 1.5 times the designed strength of a strut-and-tie model, which suggests that the model is available for predicting the strength of coupling beams with conventional reinforcement layouts such as horizontal and transverse reinforcement bars. The deformation capacity of these conventionally reinforced concrete coupling beams ranged from 1.48 to 3.47% in accordance with the reinforcement layouts of the beams. Therefore, this study found that the performance of conventionally reinforced concrete coupling beams with an aspect ratio of 1.68 can be controlled through the implementation of reinforcement details that include U-type reinforcement and the anchorage of intermediate horizontal bars.

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.

Performance based evaluation of RC coupled shear wall system with steel coupling beam

Steel coupling beam in reinforced concrete (RC) coupled shear wall system is a proper substitute for deep concrete coupling beam. Previous studies have shown that RC coupled walls with steel or concrete coupling beam designed with strength-based design approach, may not guarantee a ductile behavior of a coupled shear wall system. Therefore, seismic performance evaluation of RC coupled shear wall with steel or concrete coupling beam designed based on a strength-based design approach is essential. In this paper first, buildings with 7, 14 and 21 stories containing RC coupled shear wall system with concrete and steel coupling beams were designed with strength-based design approach, then performance level of these buildings were evaluated under two spectrum; Design Basis Earthquake (DBE) and Maximum Considered Earthquake (MCE). The performance level of LS and CP of all buildings were satisfied under DBE and MCE respectively. In spite of the steel coupling beam, concrete coupling beam in RC coupled shear wall acts like a fuse under strong ground motion.

Seismic behavior of RC coupled shear walls with strengthened coupling beams by bonded thin composite plates

The present study investigates the dynamic analysis of Reinforced Concrete (RC) coupled shear walls strengthened by bonded Carbon Fibre Reinforced Polymer (CFRP) composite plates applied on both sides of the coupling beams. For this purpose, new finite element models are developed for both the walls and strengthened coupling beams. In the validation process of the proposed model, static and free vibration analyses of coupled shear walls were firstly studied. Comparisons with ABAQUS code using shell elements were made and good agreement was observed. After this stage, dynamic analysis was carried out under El Centro and Northridge earthquake records. In these conceptual studies, the maximum top lateral deflection responses of strengthened and unstrengthened RC coupled shear walls are computed. The obtained results showed that mitigation of seismic behaviour of RC coupled shear walls by using CFRP bonded composite plates depends on the geometrical characteristics of shear wall structure and dominant range frequencies of the input earthquake records.

Identification of the dynamic properties of a reinforced concrete coupled shear wall residential high-rise building

As high-rise buildings increase with height and slenderness, they become increasingly sensitive to dynamic vibrations, and therefore the natural frequency of vibration and damping ratio are very important design parameters, as they directly impact the design wind forces. Recent advances in sensing and computing technology have made it possible to monitor the dynamic behaviour of full-scale structures, which was not possible in the past. Full-scale validation of the dynamic properties is useful for high-rise designers to verify design assumptions, especially since recent measurements have shown that damping decreases as the height of the building increases, and in situ damping measurements have been lower than many currently assumed design values, potentially leading to unconservative designs. A 50-storey residential building in downtown Toronto, with a reinforced concrete coupled shear wall lateral load resisting system with outriggers was monitored using current state-of-the-art sensing technologies and techniques to determine, in situ, the dynamic properties under real wind loads. The in situ measurements were then compared with results obtained using current state-of-the-art computer modelling techniques.

Earthquake Response of RC Coupled Shear Walls Strengthened with Thin Composite Plates

This paper deal with the seismic analysis of reinforced concrete (RC) coupled shear wall structures strengthened by bonded composite plates. In the analytical formulation of the present study, the adherent and the adhesive layers are modeled as shear wall elements, using the mixed finite element method. In the validation process of the proposal model, static and free vibration analyses of coupled shear walls are firstly studied. Comparisons with theoretical results reported in the literature are made and good agreement is observed. After this stage, numerical results are presented that relate to the performance of RC coupled shear walls bonded with composite plates under several different earthquake scenarios, in which an RC coupled shear wall strengthened by steel plates is treated as a limiting case.

Seismic behavior of RC coupled shear walls repaired with CFRP laminates having variable fibers spacing

The paper considers the seismic analysis of reinforced concrete (RC) coupled shear walls structures strengthened by bonded composite plates having variable fibers spacing. An efficient analysis method that can be used regardless of the sizes and location of the bonded plates is proposed in this study. In the numerical formulation, the adherents and the adhesives layers are all modeled as shear walls elements, using the mixed finite element method. Dynamic analysis was performed to investigates the influence of the fibers redistribution of the bonded plates on the lateral deflections of RC coupled shear walls. This conceptual study has demonstrated the feasibility of mitigating the seismic response of RC coupled shear walls building structures by using composites plates having variable fibers spacing.