Confinement Effect in Reinforced Concrete Shear Wall with Enlarged Boundary Elements

Reinforced concrete shear walls (RCSWs) are complicated to compute their shear capacity due to their large cross-sectional height-to-thickness ratios and the fact that they are subjected to vertical loads. Numerous factors influence RCSWs’ shear strength capacity, and the analytical models find it challenging to fully account for each factor’s impact on RCSWs’ shear-bearing capacity. Machine learning (ML) technology can deeply capture the mapping relationship between each input feature and the target value, and provide a more flexible and effective prediction method for RCSW shear-bearing capacity. To this end, a shear capacity test database containing 583 RCSW specimens was first established and characterized, and then the database was employed to train single, ensemble, and deep learning models for the shear strength of shear walls and combined with hyper-parameter tuning to enhance each model’s prediction performance, after which the prediction performance of each model was compared. Then, the ML models were contrasted with conventional techniques founded on the mechanical premise. Finally, in order to improve the prediction accuracy and reliability of the ML methods, the individually trained models were integrated into a stacking model using the stacking method, and the stacking model’s prediction performance was assessed. The results of this study show that in the single model, the test set R2 of the decision tree (DT) reaches 0.94, showing good trend-capturing ability. Among the ensemble models, Gradient Boosting (GB) performs the best and is comparable to DT in terms of RMSE and R2 and significantly outperforms other ensemble methods, such as Random Forest (RF) and Bagging. Deep Neural Networks (DNNs) show the strongest predictive ability among all models, with the lowest RMSE (263 kN) and a test R2 of 0.95, which is much better than the majority of ensemble models. The ML models show high accuracy and reliability compared to the traditional RC shear wall shear capacity models. The stacking model has an R2 of 0.98 and a CoV of 0.147 in the test set, and it is much better than other independent ML models (R2 = 0.88~0.95, CoV = 0.179~0.651).

Shear failure of geometrically similar RC shear walls: Mesoscopic modellings and analysis

Deformation capacity of reinforced concrete (RC) shear walls is mainly influenced by concrete confinement at the boundaries of shear walls, axial force ratio and wall aspect ratio. In this paper, the relationship among the wall boundary transverse reinforcement characteristic value λvw, the axial force ratio n, the wall aspect ratio r and the ultimate displacement Δuw is established first. Then, the relationship between λvw −−n −−r −−Δuw is verified against the results of 71 RC shear wall experiments conducted by eight different research institutions. Based on the established relationship, the performance-based seismic design (PBSD) method for RC shear walls is proposed. According to the method presented in the paper, the amount of transverse reinforcement at wall boundaries could be determined, if the inter-storey drift demand θ and the damage index Dw are predetermined. The use of the proposed PBSD method, which may guide future RC shear wall design, is illustrated in detail by an example.

Measuring strain fields in FRP strengthened RC shear walls using a distributed fiber optic sensor

Experimental study and design method of shear-dominated composite plate shear walls

Reinforced concrete (RC) structures in developing countries, such as India, had been constructed prior to the application of modern seismic codes and are vulnerable to earthquakes. Retrofitting must be performed to prevent deformation during seismic activity. This study focuses on the comparative evaluation of three retrofitting techniques, including steel bracing, RC column jacketing, and RC shear walls. These techniques are applied to a representative four-storey RC frame building located in Seismic Zone IV of India. Nonlinear static pushover and dynamic time-history analysis are performed to evaluate the structure and its seismic response prior to and after retrofitting. The evaluation metrics include the base shear capacity, inter-storey drift ratio, ductility, and stiffness. Specifically, the results indicate that all strategies improved the structural performance under seismic loading. RC infill shear walls demonstrated the most significant improvements in the base shear and drift reduction components. Steel bracing offered a balanced enhancement in strength and deformability. RC jacketing effectively strengthened ground-storey columns with a moderate overall impact.

The seismic performance of coupling beams in reinforced concrete shear walls is a critical factor in ensuring the safety and resilience of high-rise buildings, particularly in earthquake-prone regions.According to ACI 318, diagonally reinforced coupling beams are designed to deliver superior seismic performance, including ductility and energy dissipation.However, the intricate layout and congestion of diagonal reinforcement pose significant challenges during construction.To address these issues, this study proposes a new type of reinforcement approach-Equivalent Diagonal Reinforcement (EDR)utilizing diagonal steel elements (DSE) in the form of L-and box-shaped profiles.This study involves both analytical and experimental investigations on three coupling models: one with conventional diagonal reinforcement in accordance with ACI 318 (DRAC) and two, incorporating the proposed EDR system.The EDR-based models use diagonal steel elements in either box-shaped or L-shaped profiles.Experimental and numerical approaches were utilized to assess the seismic behavior of the coupling beams.Cyclic loading tests were conducted to analyze crack propagation, failure modes, and energy absorption, while finite element simulations using ABAQUS/CAE 2022 were employed to validate the experimental findings and provide further insights into stress distribution and post-peak behavior.The findings demonstrate that the proposed EDR system with diagonal steel elements effectively addresses reinforcement congestion issues while achieving desirable performance in terms of stiffness degradation, energy dissipation, and ductility improvement.This study suggests that EDR can serve as a viable alternative to conventional diagonal reinforcement, enhancing both constructability and structural performance.

Multi‐storey modular buildings, constructed from prefabricated steel modules, are gaining popularity due to their efficiency, cost‐effectiveness, and reduced construction time. However, their seismic performance and stability remain key areas of research. While reinforced concrete shear walls are commonly used as seismic force‐resisting systems (SFRS), this study investigates the feasibility of using concentrically braced frames (CBF) as an alternative. Although CBF effectively resists lateral loads, they are susceptible to soft‐storey collapse under seismic excitation. This paper examines the lateral behaviour of two 12‐storey modular buildings, where steel modules serve as the gravity force‐resisting system (GFRS), and either CBF or reinforced concrete shear wall acts as the SFRS. Nonlinear finite element pushover analyses are conducted using OpenSees to evaluate key performance metrics, including global behaviour, inter‐storey drift, and shear distribution between the GFRS and SFRS. The findings highlight the potential for efficiently using CBF in multi‐storey modular steel structures while providing deeper insights into the seismic force distribution between the GFRS and SFRS. Notably, results indicate that the GFRS can carry a significant portion of seismic forces, particularly in the upper stories.

The fundamental period of vibration is a critical structural dynamic characteristic in seismic design. Several expressions for the calculation of the fundamental period have been recommended by different building codes and previous studies. However, further studies are still needed to evaluate the design expressions used for the calculation of the fundamental periods and assess the need for further refinement. In this study, comprehensive fundamental period data from two sources is collected and compared with different formulas from building codes and previous studies. The first data set is obtained from 147 instrumented buildings with various lateral force resisting systems (LFRSs). The second set of period data are collected from the dynamic response simulations of selected structures. Different LFRSs are considered, including steel moment resisting frames (SMRFs), reinforced concrete moment resisting frames (RCMRFs), reinforced concrete shear walls (RCSWs), concentrically braced frames (CBFs), eccentrically braced frames (EBFs), masonry structures and pre-cast structures. The correlations between the derived period expressions with those recommended by the design provisions show that the code approach is conservative enough for SMRFs, CBFs, masonry buildings and pre-cast structures. For RCMRFs, EBFs and RCSWs, the design code is slightly unconservative for low-rise buildings. The outcomes of the study help to arrive at more efficient and cost-effective seismic design of buildings with different characteristics.

This study attempts to develop new simplified approximate formulas to predict the fundamental natural periods of vibration (T) for bearing wall systems engaged with special reinforced concrete shear walls (RCSW) under seismic loads. Commonly, seismic codes suggested empirical formulas established by regression analysis of measured T for buildings during earthquake motions. These formulas depend on structure type, building height, number, height and length of SW, and ratio of SW area to base area of structure. In this study, a parametric investigation is performed for T of 110 selected models of bearing RCSW systems with varying structural height, configuration of horizontal plans including building width, number and width of bays, presence of middle corridors and core SWs. For this purpose, a 3D non-linear response time history (TH) analysis is implemented using ETABS v16.2.1. New formulas to estimate T are anticipated and compared with those obtained from formulas of IBC 2012 and ASCE/SEI 7-10. Moreover, the study examines responses of an arbitrarily two selected test model of 60 m and 80 m in height with presence of SWs having middle corridors. It is observed that the performance of the tested buildings is different through arising of considerable errors when using codes

Several recent research studies have demonstrated that the seismic performance of low-aspect-ratio reinforced concrete (RC) shear walls (i.e., defined herein as walls with height-to-length ratios less than 2) has not been yet adequately quantified to allow for robust risk assessment. This is mainly attributed to the complex nonlinear flexure/shear interaction behavior of such walls, along with their wide spectrum of possible design parameters, leading to major discrepancies in their seismic performance. Despite this unique behavior, most building codes and design standards do not assign distinctive seismic performance factors for such walls. To address this, the main objective of the current study is to propose seismic performance factors for low-aspect-ratio RC shear walls when different wall geometrical configurations and design parameters (e.g., aspect ratios, axial load levels, and seismic design categories) are adopted. These factors are evaluated against the acceptance criteria of the FEMA P695 methodology for Quantification of Building Seismic Performance Factors. In this respect, a numerical model was developed and experimentally validated to simulate the seismic response of 36 low-aspect-ratio RC shear wall archetypes. The model was utilized to perform nonlinear static and dynamic analyses, and collapse fragility curves were then generated to assess the collapse risk of such wall archetypes following the FEMA P695 methodology. According to the methodology, the proposed seismic performance factors were assessed by quantifying the ratio between the median collapse intensity and the intensity of the maximum considered earthquake (MCE). The results showed that R factors of 2.0 and 3.0 for special low-aspect-ratio RC walls with low and high axial load levels, respectively, can limit the probability of collapse under the MCE and are subsequently able to meet the FEMA P695 acceptance criteria.

In order to calculate the shear capacity of a reinforced concrete (RC) shear wall, some models based on the theory of limit analysis (called “Macro model”) are proposed. These models contains many assumptions which need to be certified, and FEM analysis is considered to be a useful method to examine these assumptions. So, in this study, a nonlinear FEM program to analyze RC shear walls was developed, and the correctness of the macro models was examined by using the FEM analysis.

The explosion test and numerical simulation of a full-size specimen were carried out to investigate the dynamic response and failure characteristics of the reinforced concrete shear walls under near-field explosion. The TNT was located at 0.55 m above the top plate center of the reinforced concrete shear wall with an equivalent of 6.4 kg and a proportional distance of 0.296 m/kg1/3. The reinforced concrete shear wall’s reflected overpressure, displacement, and acceleration were measured and analyzed. The laser 3D scanner scanned the backside failure characteristics. An LS-DYNA numerical model was established and validated by the experimental results. The effects of TNT equivalent, reinforcement ratio, concrete strength, and thicknesses on the explosion resistance of the reinforced concrete shear walls were analyzed. The study results show that increasing the reinforcement rate, using high-strength concrete, and increasing the thickness can all improve the blast resistance of reinforced concrete walls, with increasing the thickness being the most effective measure. The peak displacement values of the back of the reinforced concrete shear wall at the center 1/4 height increase with the increase in charge. Using the least square method, the corresponding fitting curve expressions were obtained. The results can provide references for blast-resistant concrete shear walls design.

To improve the lateral stiffness and economy, reinforced concrete shear walls are introduced in buildings. This study aims to conduct the seismic assessment of shear walls in a multi-storey building. In this work, various factors are investigated and their performance is compared for various shapes and types of shear walls with respect to strength, displacement, time period, etc. The building considered for the study purpose is a G+12 residential building and is situated in a high seismic zone. The response spectrum analysis of the building is carried out by using the software ETABS. The results show that shear walls not only reduce the seismic forces in a building, but also are advantageous if they are situated in proper positions.

3D cost optimization of 3 story RC constructional building using Jaya algorithm