Concrete Shear Walls Research Articles

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.

Shear bearing capacity prediction of STRC shear walls using data‐augmented fusion model

AbstractMachine learning (ML) accurately predicts the shear bearing capacity of steel tube‐reinforced concrete (STRC) shear walls, aiding optimization design. However, creating a database for STRC shear walls experimentally is time‐consuming and costly. The aim of this study is to propose a method for high‐accuracy prediction of STRC shear wall shear bearing capacity using a small‐sample dataset. This study employs generative adversarial network (GAN) data augmentation techniques to address the issues of insufficient ML model training and low prediction accuracy in small‐sample databases. Based on the stacking framework, a fusion model (Stacking‐XRL) combining extreme gradient boosting (XGBoost), random forest (RF), and least absolute shrinkage and selection operator (LASSO) is established to predict the shear bearing capacity of STRC shear walls. Results show that after augmenting the training set with GAN, the prediction performance of K‐nearest neighbors (KNN), backpropagation neural network (BPNN), RF, light gradient boosting machine (LightGBM), XGBoost, and stacking‐XRL models significantly improve, with average increases of 10% in R2 and average decreases of 30% and 25% in MAE and RMSE, respectively. The proposed stacking‐XRL fusion model outperforms tested models, existing formulas, and Abaqus numerical simulations for the shear bearing capacity of STRC shear walls. Model interpretation reveals that the shear span ratios as the most important factors in predicting shear bearing capacity, followed by axial force ratio and whole section configuration steel tubular index.

Development and implementation of shear wall finite element in OpenSees

Shear walls are widely used as lateral load-resisting systems in high-rise building structures. The design and nonlinear analysis of shear walls under seismic loads for recoverability are complicated and challenging, which demands nonlinear computer modeling procedures. This paper presents a novel finite element named Double Vertical Beam-column with Shell Element (DVBSE) for the nonlinear analysis of complex reinforced concrete shear walls with columns. The DVBSE is implemented in the open-source finite element program OpenSees. The theoretical formulations of DVBSE are described in detail. The accuracy of the developed DVBSE is established by comparing the finite element analysis results with existing experimental data on recoverable steel-GFRP composite bar reinforced concrete shear walls. The comparative study demonstrates that the proposed DVBSE is superior to the commonly used finite element model in simulating the responses of recoverable complex shear walls under seismic loads. These research findings contribute to further advancements in the development of new shear wall elements and lay a solid foundation for the nonlinear numerical simulation of innovative shear walls.

Plastic Hinge Length for Flanged Reinforced Concrete Shear Walls with Asymmetric Sections

ABSTRACT This research investigates the determination method, spreading mechanism and influencing factors of the plastic hinge length for asymmetrical flanged walls using the finite element method. The plastic hinge length of flanged walls under flange-in-compression loading is generally greater than that under flange-in-tension loading. Based on the results, simple equations for predicting the plastic hinge length of flanged walls and which consider the contributions of the moment gradient, diagonal shear cracks, and strain penetration are proposed. Through comparison with the existing equations and design codes, the predicted plastic hinge lengths obtained from the proposed equations accord better with the test results.

Experimental Study on Seismic Performance of Prefabricated Monolithic Concrete–Polystyrene Panel Composite Wall Panels

A normal composite wall panel is a structural component composed of polystyrene insulation boards and concrete surface layers reinforced with steel wire mesh. It can be entirely prefabricated in a factory or constructed with the concrete surface layers cast on-site. A novel prefabricated monolithic concrete–polystyrene panel composite wall panel (CPC wall panel) is proposed in this study. The CPC panel features a middle part that is prefabricated in the factory while the reinforced concrete regions at its two side ends are cast on-site. To evaluate the seismic performance of the wall panel, 18 CPC specimens were designed, manufactured, and quasi-statically tested, through which the structural behaviors, failure mode, and load-bearing capacity were studied. In addition, the influences of the height-to-width ratio and the vertical compressive stress level on the seismic performance of the CPC panels were also investigated. The test results showed that the connectors spaced at 400 mm × 500 mm could ensure the concrete layers on both sides of the polystyrene board worked collectively under seismic conditions. When subjected to lateral loads, the interface between the newly poured concrete and the existing concrete exhibited good bonding. Moreover, the failure mode of the CPC wall panel was largely correlated to the height-to-width ratio that, for specimens having four steel bars of 12 mm diameter and a height-to-width ratio greater than 1, the flexural failure was initially developed, followed by diagonal shear failure. In specimens with a height-to-width ratio of 1, flexural and diagonal shear failures occurred almost simultaneously. For specimens with a height-to-width ratio of less than 1, the final diagonal shear failure was predominant. The longitudinal reinforcing bars at the two ends of the CPC panels could effectively improve their lateral load-bearing capacity, with the enhancement influenced by the height-to-width ratio, the vertical load applied to the wall panel, and the cross-sectional area of the steel bars. In practice, the lateral load-bearing capacity of the CPC panel can be conservatively evaluated using the calculation method of the reinforced concrete shear walls. Finally, the ductility of the CPC specimens was affected by the height-to-width ratio and the axial compressive stress level, such that the specimens with a larger height-to-width ratio and lower axial compressive stress exhibited better ductility.

Seismic connection performance of precast all-lightweight aggregate concrete shear walls

This study investigated the ductile behavior of the seismic connection performance in precast all-lightweight aggregate concrete shear walls (PALSWs) connected using the bolting technique developed by Yang et al. or the conventional spliced sleeve technique. The ductile behavior of the seismic connection performance was verified in PALSWs designed with different yield strengths (fy) of the longitudinal reinforcing bar and amounts (Ash) of transverse reinforcement, which are major factors affecting the ductility of shear walls. Eight PALSW specimens were prepared and tested under constant axial and cyclic lateral loads. The test results showed that the bolting technique developed by Yang et al.was favorable to achieve higher ductility in PALSW specimens than the conventional spliced sleeve technique, indicating that the displacement ductility ratio (μΔ) and work damage index (W80) of the PALSW specimens connected using the bolting technique were approximately 1.37 and 1.72 times higher, respectively, than those of the companion specimens connected using the conventional spliced sleeve technique. However, despite using the bolting technique, the PALSW specimens designed with the minimum required amount (Ashm) of transverse reinforcement at the boundary element specified in ACI 318–19 and the fy value of 600 MPa showed a tendency of brittle seismic connection performance. Consequently, these specimens did not satisfy the seismic connection performance requirements specified in ACI ITG 5.1–07 and AIJ. Therefore, to achieve a high ductility of PALSW and satisfy the requirements based on the emulation evaluation concept specified in ACI ITG-5.1-07 and AIJ, PALSWs recommends the use of the bolting technique developed by Yang et al. and a design with Ash of 1.5 Ashm or more, and fy of no more than 400 MPa.

Machine Learning Prediction Model for Boundary Transverse Reinforcement of Shear Walls

Due to their roles as efficient lateral force-resisting systems, reinforced concrete shear walls exert a tremendous degree of influence on the overall seismic performance of buildings. The ability to predict the boundary transverse reinforcement of shear walls is critical to the seismic design process, as well as in the overall evaluation and retrofitting of existing buildings. Contemporary empirical models attain low predictive accuracy, with an inability to capture nonlinearity between boundary transverse reinforcement and different influencing variables. This study proposes a boundary transverse reinforcement prediction model for shear walls with boundary elements based on the demand of ductility. Using the extreme gradient boosting machine learning algorithm and 501 samples, some 52 input variables are considered, and a subset with six features is selected, monitored, and analyzed using both internal methods (gain and cover) and external methods. The results (R2=0.884) display superior predictive capacity compared with existing models. Interpretation and error analysis are performed. Safety analysis is conducted to obtain references for use in practical engineering. Overall, this study presents a more accurate tool for use in seismic design and provides references for the evaluation and retrofitting of existing buildings. Our contributions hold significant implications for enhancing the safety and resilience of reinforced concrete structures.

Experimental Study on Seismic Performance of Partially Corroded Squat RC Shear Walls in Coastal Environment

In coastal environments, squat reinforced concrete (RC) shear walls are susceptible to local accumulation of moisture and chloride salts, causing local corrosion in the shear walls, which in turn affects their seismic performance. Four squat RC shear wall specimens were designed considering the corrosion locations and the heights of the corroded area. The seismic performance of partially corroded squat RC shear wall specimens was analyzed through a quasi-static test. The results show that as the height of the corroded area increases from 15% to 25% of the total height, the area of the hysteresis loop of the shear walls obviously decreases. As the height of the corroded area increases from 0 to 15% and 25% of the total height, the peak and ultimate displacements of shear walls are, respectively, reduced by 6.7% and 19.2% in the positive loading direction, and are, respectively, reduced by 22.3% and 18.3% in the negative loading direction. Compared with the unilateral corroded shear wall, the area of the hysteresis loop and the stiffness of the bilateral corroded shear wall remain approximately unchanged, and the peak and ultimate displacements, the shear strain, and the ratio of shear deformation to horizontal displacement are reduced. Compared with the uncorroded shear wall, the hysteresis loop of the unilateral corroded shear wall is plump, the displacement ductility ratio and the plastic rotation angle are both increased, and the stiffness degradation is relatively slow.

Research on seismic behavior of precast concrete shear wall with new steel plate-bolted horizontal connection

A new type of steel plate-bolted horizontal connection for precast concrete shear wall is proposed in this paper. To investigate the seismic performance of the precast concrete shear wall with the new steel plate-bolted horizontal connection (SPB-PSW), quasi-static tests were conducted on two SPB-PSWs (PSW-1 and PSW-2 with axial compression ratios of 0.1 and 0.2, respectively), as well as one cast-in-place concrete shear wall (SW-1, with an axial compression ratio of 0.1). The test results indicate that the proposed new connection type can increase the horizontal bearing capacity of the shear walls by 5.3 %, enhance the energy dissipation capacity by over 14.8 %, and improve ductility by 32 %. For the three shear walls, the SW-1 suffered severe damage at the bottom and corner of the wall, whereas the damage location for the two SPB-PSWs moved upwards. The specimen PSW-2 exhibited a 6.9 % higher bearing capacity compared to the PSW-1, but its ductility decreased by 10.5 % and the energy dissipation was slightly smaller. Furthermore, the effects of shear span ratio and steel plates on the seismic performance of SPB-PSWs were studied using nonlinear finite element method (FEM). The FEM results indicate that increasing the strength and thickness of the connecting steel plate have little influence on the load-bearing capacity of SPB-PSWs. Compared to the SPB-PSW with a shear span ratio of 1.94, the horizontal bearing capacity of SPB-PSWs with ratios of 1.48 and 2.40 decreases by 24.0 % and increases by 26.1 %, respectively, indicating that the horizontal bearing capacity of the SPB-PSWs decreases when the shear span ratio increases.

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.

A bottom-up analysis of the seismic performance of prefabricated recycled concrete shear wall via concurrent macro-mesoscale numerical approach

Uncertainty in the failure mechanism and damage evolution of recycled aggregate concrete (RAC) due to complex components largely restricts the practical application of RAC in load-bearing members. In this study, a feasible concurrent macro-meso numerical approach is proposed to investigate the seismic performance of prefabricated recycled concrete shear wall (PRCSW), with an emphasis on revealing the failure mechanisms at both the material and structural scales. Specifically, RAC is regarded as a multiphase heterogeneous material that is represented by an elaborative mesoscale random aggregate model consisting of six phases. The collective mechanical responses of RAC are reasonably captured under various replacement rates of recycled aggregate (Rra = 0, 30%, 50%, 70%, and 100%) and volume fractions of old mortar (Vom = 12%, 16%, 20%, and 24%). In addition to this, a practical concurrent macro-mesoscale model of PRCSW is established, in which the mesoscale model of RAC is exclusively exploited in the critical vulnerable regions (e.g., concealed beam, column, and bottom of wall limb), while the macroscale model is utilized for the remaining regions, striking a balance between computational efficiency and accuracy. To facilitate the numerical implementation, a highly effective approach using Linear Multi-Point Constraint (LMPC) is adopted to establish connections between models operating at varying scales, thus allowing for the simulation in parallel. Upon such a bottom-up numerical analysis, the results show that due to the significantly weakened properties of old mortar and the inclusion of associated interfacial transition zones (ITZs), the damage development and mechanical performance of RAC are quite different from that of ordinary concrete, manifesting as the amplified accumulation of damage around aggregates and severe fractures of recycled aggregates. Although the addition of RAC (Rra increases from 0 to 100%) is found to slightly weaken the horizontal seismic bearing capacity of PRCSW (decreased by 8.57%), its structural deformation capacity, however, is obviously compensated (increased by 34.42%), resulting in a marginal variation of energy dissipation capacity. The findings facilitate the utilization of substantial RAC in load-bearing members with higher confidence.

Data-driven shear strength prediction of steel reinforced concrete composite shear wall

Due to composition of concrete and steel materials, steel reinforced concrete composite shear wall (SRCCSW) plays a pivotal role as the primary lateral load-resisting component in buildings. Accurate prediction of shear strength is crucial, but numerous complex factors affect the shear strength, including shear-span ratio, axial load ratio, and materials properties. Therefore, it is imperative and urgent to develop precise prediction model. In this paper, machine learning (ML) models for predicting the shear strength of SRCCSW are developed. Firstly, a comprehensive database is established by collecting experimental data of 149 SRCCSW. Twelve predictive models are proposed, evaluated, and compared, including linear regression, decision tree, K-nearest neighbors, support vector regression, random forest, gradient boosting, adaptive boosting, categorical boosting, extreme gradient boosting (XGB), light gradient boosting machine, histogram-based gradient boosting, and artificial neural network. Then, six existing empirical models are further evaluated and compared. Finally, SHapley Additive exPlanations (SHAP) is employed to comprehensively explore the global explanation, individual explanation, and feature dependency of XGB model. The results show that the LR model is not as effective as that of other ML models, and the predictive performances of other ML models are generally comparable. The XGB model outperforms the best empirical model with a correlation coefficient of 0.99 (vs. 0.80) and a standard deviation of 520 kN (vs. 491 kN), while the experimental results have a standard deviation of 516 kN. Compared to other models, the XGB model possesses superior predictive accuracy and smallest dispersion. Wall height and shear-span ratio are the most two critical variables influencing the shear strength. At the individual level, the model’s prediction may depend only on certain features rather than having complex dependencies on all features. For the same feature, SHAP values may vary significantly due to the influence of other features. These results provided by SHAP reveal the detailed insights into the comprehensive impact of features on the shear strength of SRCCSW.

Seismic Performance Assessment of Composite Frame–High-Strength Steel Plate Wall Core Tube Resilient Structural System

Against the backdrop of China’s continuous promotion of green and low-carbon transformation and the development of construction industrialization, high-strength composite structural systems have significant development prospects. However, their research and application in the field of construction are insufficient. In response to this issue, the study proposes a new high-performance structural system, namely the composite frame–high-strength steel plate wall core tube resilient structural system, which includes a core tube composed of double steel plate concrete composite shear walls and replaceable energy dissipation coupling beams, as well as composite frames. The highest strength grades of the steel plate and concrete used in the composite walls of the core tube are Q550 and C100, respectively. Using a 200 m building as an example, this study designs and establishes models for this high-performance structure and a conventional reinforced concrete frame–core tube structure. Subsequently, the dynamic elastoplastic time history analysis and seismic resilience assessment of structures are conducted under design basis earthquakes (DBEs), maximum considered earthquakes (MCEs), and extremely rare earthquakes (EREs). Research has shown that, compared to conventional structures, the thickness of shear walls of new high-performance structures can be effectively reduced, which helps decrease the self-weight of the structure and improve the available space in buildings. Additionally, high-performance structures exhibit a better performance in controlling the story drift ratio, lower plastic damage and overall stiffness degradation of the structure, and better seismic performance. The seismic resilience of the high-performance structure has been significantly enhanced, especially in terms of minimizing casualties, thereby better ensuring the safety of people’s lives and property.

Implications of the 2020 National Building Code of Canada updates on the design demands for reinforced concrete shear wall buildings

The seismic demands of the Reinforced Concrete Shear Walls (RCSWs) system are determined based on Canada’s National Building Code (NBC). NBC 2020 features the revised Canadian Seismic Hazard Model and presents the possibility of enhancing demand’s accuracy by determining design spectra based on the specific average shear wave velocity, instead of specified site classes. This paper investigates the changes in design demands for RCSWs compared to the previous edition. To do so, fifty-five RCSW prototypes were modelled using distributed mass and stiffness procedure, and their dynamic response was assessed through Modal Response Spectrum Analysis at five locations across Canada. The results highlight significant changes in deformation and force demands, where the majority of cases experienced an increase in 2020 compared to 2015 when demands were determined based on specified site classes. This study also evaluates the log-log interpolation method recommended by NBC 2020 for the design spectral acceleration.

Study of the Impact Irregular Concrete Facilities with the Shear Walls Based: The Effect of Soil-Structure Interaction with ABAQUS Software

In the present study, the effect of irregularity of structures of the concrete with special shear walls has been analyzed and modeled by considering the effect of soil-structure interaction by dynamic analysis method with ABAQUS software. The results are presented in the form of diagrams with different soil interaction conditions, the effect of the number of layers was investigated for different soils. The results showed that the bearing system of the flexural frame and the concrete shear wall under the lateral load of the earthquake have good strength and ductility, which makes this issue. This structural system should be used for cities with very high earthquake risk. As the number of floors increases, the effect of the shear walls on increasing the bearing capacity decreases. As the number of floors increases, the final displacement of the frame increases. The results showed that for soil type 1(hard soil which Vs=1000 m/s, v=0.15, q=50000 Kg/m2, P=2000 Kg/m3, r=0.5 m) structural system of concrete shear walls with better displacement, maximum structural stiffness, better behavior was observed in the structure. Three-story frame with concrete shear wall has a significant increase compared to similar frames with more floors, which shows the good performance of this system in structures with fewer floors.

Shear bearing capacity calculation of low-rise SFRC shear wall with CFST columns based on simplified softened strut and tie model

In the paper, an innovative shear wall, which is referred to as steel fiber reinforced concrete (SFRC) shear wall with concrete filled steel tube (CFST) columns, is introduced, based on the high bearing capacity and large stiffness of concrete filled steel tube column (CFSTC) and good cracking resistance and strong toughness of steel fiber reinforced concrete. The loading mechanism of steel fiber reinforced concrete shear wall (SFRCSW) with concrete filled steel tube columns is analyzed, and shear bearing capacity calculation method. A simplified model of the steel fiber reinforced concrete shear wall web softening tension bar is proposed, concrete and distributed web reinforcement to the shear bearing capacity of steel fiber reinforced concrete shear wall web is identified. Furthermore, a new algorithm to obtain the shear bearing capacity of steel fiber reinforced concrete shear wall with concrete filled steel tube columns is established, and then it is validated by using the test results of steel fiber reinforced concrete shear wall with concrete filled steel tube columns under low-cycle repeated loading. The results showed that all tested shear wall specimens exhibited obvious shear failure characteristics and a typical diagonal cracking pattern after test. The steel fibers obviously improved the crack forms of the steel fiber reinforced concrete shear wall web and the seismic behavior of steel fiber reinforced concrete shear wall with concrete filled steel tube columns. In addition, the proposed calculation method is scientific and accurate to analyze and predict the shear bearing capacity of low-rise steel fiber reinforced concrete shear wall with concrete filled steel tube columns.

Experimental study on horizontal low-cycle loading of high-strength concrete medium high shear wall with cold-formed steel braces

This study presents the findings from experimental tests conducted on four medium-high shear walls with a shear span ratio of 1.8. The focus of the study is to investigate the effect of different types of cold-formed steel diagonal braces on the seismic performance of the shear walls. The specimens were subjected to horizontal low-cycle loading to observe their failure behavior, including cracking load, ultimate displacement, yield load, and ultimate load. Additionally, a comparative analysis of the stress distribution in the cold-formed steel braces, braces with different steel ratios but of the same type, and braces with the same steel ratio but of different types, was conducted. The research findings indicated that the inclusion of an appropriate amount of cold-formed steel braces with an appropriate steel ratio significantly improved the ultimate displacement and shear stiffness of the structures. The cold-formed steel braces effectively restrained crack development and prevent structural collapse after failure. However, it was observed that the lattice-type braces failed to confine the internal concrete to form a compressed concrete strut capable of resisting both shear and bending moment simultaneously. The addition of cold-formed steel braces was found to be advantageous in improving the shear stiffness of the specimens. In particular, the cold-formed angle steel braces in SRHCW-2 were more effective in enhancing the shear stiffness compared to the lattice-type cold-formed steel braces in SRHCW-3. Moreover, an increase in the steel brace ratio on top of the lattice-type cold-formed steel braces in SRHCW-3, as observed in SRHCW-4, contributed to a certain improvement in the structural shear stiffness.

Seismic behavior of a new type of precast concrete shear wall using UHPC connections at boundary elements

Ultra-high Performance Concrete (UHPC) is an attractive choice for connecting Precast Concrete Shear Walls (PCSWs), because of its high bond strength with rebars allowing for reduced lapped rebar lengths and precision requirements. This paper proposes a new type of PCSW that uses UHPC connections only at the boundary elements, significantly streamlining the installation process of wall panels and improving construction efficiency. To evaluate its seismic behavior, a total of five walls comprising three PCSWs and two Cast-In-Place (CIP) walls were tested by cyclic loadings under both low and high axial loads. Similar failure modes characterized by bending-shear damage were captured in all five specimens. The proposed precast walls display 7.8%–8.1% greater bearing ability and 41.8% higher ductility in comparison to CIP counterparts. These precast walls also demonstrated superior energy dissipation ability, particularly under high axial loads. Following NEHRP, it was validated that the proposed precast walls using UHPC connections at boundary elements could be used in regions with high seismic activity. Moreover, the finite element (FE) models were developed, yielding simulated results that aligned reasonably with the experimental findings, and the parametric predictions were performed to further broaden the scope of experimental works.

Experimental and numerical evaluation of seismic behavior of coupled walls connected by post-tensioned, unbonded, precast concrete coupling beams

To investigate the seismic performance of coupled shear walls, which are connected by post-tensioned, unbonded, precast concrete coupling beams (PCCB), two 1/7-scale experiments with 8-story coupled shear walls under cyclic lateral loadings were conducted. Coupling of concrete shear walls is achieved by post-tensioning concrete beams to the wall piers using unbonded post-tensioning tendons (UPT) at the floor and roof levels. Experimental results show that little damage occurs in the coupling beams and the wall regions when the specimen undergoes large nonlinear displacements. The residual displacements of the specimen are small because of the restoring effect of the post-tensioning force. The seismic performance of three systems including CW-RC (coupled wall systems that use traditional RC coupling beams), CW-UP (coupled wall systems which use only post-tensioning tendons without steel reinforcement through the beam-wall joints), and CW-HUP (shear walls and PCCB that use combinations of steel reinforcement and post-tensioning tendons) are evaluated by means of nonlinear dynamic analysis. The calculation results indicate that the inter-story drift and peak lateral displacements of CW-HUP and CW-UP are greater than that of CW-RC, whereas the residual deformations are reduced because of the self-centering effect of the post-tensioning tendons.

Modelling of Hybrid Steel-SMA Shear Walls with Local Strain and Reinforcement Considerations

The incorporation of Super-elastic (SE) Shape Memory Alloys (SMAs), such as Nitinol (Nickel-Titanium), presents a method of passively improving the damage resiliency of traditional reinforced concrete structural elements. This resiliency can be of particular use in seismic applications owing to the super-elastic behavior allowing for increased recentering. Currently available experimental data on hybrid slender shear walls incorporating both steel and SE-SMAs has demonstrated the recentering improvements while also highlighting that use of SE-SMAs tend to cause the formation of a predominant crack that controls the response. The ability to more accurately predict this behaviour through numerical modelling would allow for better understanding of the salient parameters affecting the response of hybrid slender shear walls. The paper herein presents a numerical modelling methodology that considered the impacts of local strain concentration as a result of a singular predominant crack formation during reverse-cyclic loading. This modelling was performed in VecTor2, a non-linear two-dimensional finite element program, in conjecture with experimental data of a hybrid steel-SMA slender shear wall and a steel-only reinforced concrete companion wall. The use of a tension stiffening constitutive model which considered local fracture was found to improve the displacement prediction capabilities of models. Additional considerations which were investigated included local reinforcement properties to reflect conditions at the wall base and accounting for the impact of strain gauge instrumentation on the location of rupture of the reinforcement. The results provide insight into the numerical modeling that captures the local strain and reinforcement conditions present in hybrid steel-SMA and reinforced concrete slender shear walls.