Reinforced Concrete Structural Walls Research Articles

On estimating the drift capacity of reinforced concrete walls with lap splices at their bases

AbstractFailures in reinforced concrete (RC) structural walls have been reported to occur at longitudinal lap splices in earthquakes as far back as 1964 (Kunze et al. in JP 62:635–650, 1965) and as recently as 2023 (Pujol et al. in ES 63:777, 2024). Design codes such as ACI318-19 (2019) and JSCE Standard Specification for Concrete Structures (2007) have been adjusted accordingly and have banned the placement of lap splices near sections where longitudinal reinforcement is expected to yield in reinforced concrete structural walls. But minimizing lap splice vulnerabilities in new construction does not address existing buildings that may be vulnerable to earthquakes because of lap splices placed at or near critical sections. A simple, rapid assessment technique should be adopted to address the large number of existing buildings with potentially vulnerable RC walls. To investigate the deformation capacity of structural walls with lap splices near sections where longitudinal reinforcement yields, a two-part experimental program is ongoing: four large-scale walls with non-staggered lap splices were tested at Purdue University (Pollalis Drift capacity of reinforced concrete walls with lap splices, Purdue University: West Lafayette, 2021) and two large-scale walls with staggered lap splices have been tested at the University of Canterbury (Kerby et al. Experimental study of staggered lap splices in RC structural walls, 2023). Results from these six tests are added to a dataset of 15 previous tests of walls with non-staggered lap splices compiled by Almeida et al. (JSE 143:853, 2017). A method to estimate drift capacity of walls with lap splices is proposed based on estimates of lap splice strength, steel stress–strain relationships, and moment-area theorems. Two sets of assumptions can be used to produce estimates of drift capacity. The first set of assumptions applies when detailed information of reinforcement stress–strain relationships is available, and the second set of assumptions applies when reinforcement stress–strain relationships must be assumed. Both sets of assumptions produce reasonable estimates of the drift capacity of walls with lap splices, and the second set of assumptions can be used for rapid assessment given minimal information about the detailing and material properties of a wall.

Effect of Wall Size on the Rotation Capacity of Reinforced Concrete Structural Walls

Effect of Wall Size on the Rotation Capacity of Reinforced Concrete Structural Walls

Seismic behavior of an innovative assembled composite structural wall

In order to solve the problems of corrosion and premature buckling of the exterior steel plate of the double-steel composite structural wall (DSCW), this paper proposed an innovative assembled composite structural wall (ACW). The concrete layers are innovatively utilized in ACW as protection layers to prevent steel plates from corrosion and early buckling. Six ACW specimens and a reinforced concrete (RC) structural wall were tested under cyclic load, and the seismic performance was evaluated. The results showed that: i) the displacement capacity decreased and the strength degraded rapidly as the stud spacing increased; ii) an increase in reinforcement ratio mitigated the concrete crushing at the wall toe and the steel plates buckling; and iii) two exterior concrete layers effectively delayed the yielding of steel plates, improving the ductility and flexural strength of ACWs, but one exterior concrete layer caused the out-of-plane torsion failure. In addition, ACW was better in terms of ductility, load capacity, and energy dissipation capacity compared to traditional RC structural walls. Finally, three different codes were evaluated, and the calculated results of AISC 360–22 were conservative compared with the experimental results.

A hybrid approach for seismic fragility analysis of reinforced concrete structural walls independent of failure pattern

Establishing seismic fragility relationships of reinforced concrete (RC) structural walls plays an important role in the seismic risk and resilience assessment of RC structures. However, RC structural walls have different failure patterns under earthquake excitations, and different analytical models are commonly required to simulate the seismic responses of RC structural walls with different failure patterns. This brings to the difficulty of seismic fragility analysis for a wide variety of RC structural walls due to the failure-pattern-dependence. To overcome this shortcoming, a hybrid approach was developed in this study to establish the seismic fragility relationships of RC structural walls independent of failure patterns by combing experimental data and numerical simulation. The experimental data was collected from past quasi-static tests of RC structural walls having different failure patterns. The Bouc-Wen-Baber Noori (BWBN) model was used to describe the complicated hysteretic behaviors of RC structural walls under different failure patterns, whose model parameters were calibrated using the collected experimental data. Based on the calibrated BWBN models, an equivalent single-degree-of-freedom (ESDOF) system was employed to predict the seismic demand of RC structural walls. Furthermore, the predicted seismic demand of RC structural walls was compared with the seismic capacity that was both identified from the collected experimental data, developing the seismic fragility relationships of RC structural walls independent of failure pattern. For facilitating the application in practice, artificial neural network (ANN) models are finally developed to predict model parameters of the cumulative lognormal distribution for generating the seismic fragility relationships of RC structural walls rapidly. The investigation indicated that the proposed approach provides a promising way to perform the seismic fragility analysis for a wide variety of RC structural walls.

Machine learning based prediction model for plastic hinge length calculation of reinforced concrete structural walls

Reinforced concrete structural walls (RCSWs) are integral part of buildings and other structures and are used to carry in-plane and out-plane loads. For assessment purposes and to ensure safety and resilience of the structure, the curvature, capacity, and strain demands of RCSWs need to be estimated. Nonlinear numerical models are increasingly used in earthquake engineering design and assessment, where it is critical to develop high fidelity simulation tools to precisely forecast the global and local behavior of RCSWs. Plastic deformations concentrated in small regions, i.e. plastic hinges, and characterized through the concept of plastic hinge length (PHL), are conventionally used to define the inelastic response of RCSWs. In this study machine learning (ML) algorithms were leveraged in evaluating the PHL of RCSWs. A database containing 721 planar and nonplanar RCSW samples were utilized for training and testing ML models. Four different algorithms were employed, namely: XGBoost, CatBoost, Random Forest (RF), and genetic programming. The RF model outperformed other ML counterparts. The results of the best ML model were also compared against empirical equations available in literature and nonlinear regression analysis. The proposed ML model provided much better predictions than the existing relationships. Predictions of most empirical models were found to be extremely over (or under) conservative. The proposed ML model was also presented via an online tool where users can obtain the PHL of any RCSW simply by inputting wall parameters and clicking a run button.

System overstrength factor induced by interaction between structural reinforced concrete walls, floors and gravity frames: Analytical formulation

In multi-storey structural wall buildings, the structural walls are required to resist additional shear force due to their interactions with the floors and gravity-resisting system, which is not fully catered for in current seismic design provisions and assessment guidelines. This paper scrutinizes the mechanics of the interaction between structural reinforced concrete (RC) structural walls, floors and gravity frames in multi-storey RC structural wall buildings during elastic and nonlinear response phases. It also investigates the implications of this interaction on design of multi-story RC wall buildings. Generic expressions are derived to predict the drift and rotation profiles of multi-storey RC wall buildings. Then, a simple hand calculation method is developed to estimate the system (moment) overstrength of multi-storey RC wall buildings due to system (wall-floor-frames) interaction. The proposed method is applied to a prototype building with different slab dimensions and stiffness, and verified by comparing with the system overstrength factor obtained using finite element analysis. The simplified method estimates, and the nonlinear finite element analyses results agree, that a system overstrength factor of 1.7 can be used to account for the 3D interaction between the structural walls, floors and gravity frames in design and assessment of typical ductile RC wall buildings.

Failure Mode Detection of Reinforced Concrete Shear Walls Using Ensemble Deep Neural Networks

Reinforced concrete structural walls (RCSWs) are one of the most efficient lateral force-resisting systems used in buildings, providing sufficient strength, stiffness, and deformation capacities to withstand the forces generated during earthquake ground motions. Identifying the failure mode of the RCSWs is a critical task that can assist engineers and designers in choosing appropriate retrofitting solutions. This study evaluates the efficiency of three ensemble deep neural network models, including the model averaging ensemble, weighted average ensemble, and integrated stacking ensemble for predicting the failure mode of the RCSWs. The ensemble deep neural network models are compared against previous studies that used traditional well-known ensemble models (AdaBoost, XGBoost, LightGBM, CatBoost) and traditional machine learning methods (Naïve Bayes, K-Nearest Neighbors, Decision Tree, and Random Forest). The weighted average ensemble model is proposed as the best-suited prediction model for identifying the failure mode since it has the highest accuracy, precision, and recall among the alternative models. In addition, since complex and advanced machine learning-based models are commonly referred to as black-box, the SHapley Additive exPlanation method is also used to interpret the model workflow and illustrate the importance and contribution of the components that impact determining the failure mode of the RCSWs.

Cyclic tests of full-scale fiber-reinforced concrete (FRC) walls with steel and hybrid fibers for low-rise buildings

Industrialized reinforced concrete (RC) systems have become a solution widely used in developing countries as an efficient alternative system for housing construction, compared with traditional masonry infilled frames and reinforced masonry systems. These systems provide high efficiency in construction through an appropriate planning of activities, budget, staff, equipment and materials, generating a fast and effective massive production process. This study aims at optimizing the construction time by replacing the welded-wire steel meshes with fiber-reinforced concrete (FRC) in the web of the walls without affecting the serviceability and seismic performance of low–rise housing. Eight full-scale isolated RC structural walls (one with conventional welded-wire steel, three with steel fiber and four with hybrid fibers) were designed and tested under in–plane quasi–static cyclic loads. The parameters evaluated are the characteristics of the fiber reinforced concrete mixture (volume fraction of fibers and type of fibers) and the amount of reinforcement at the boundary elements. The paper discusses the measured performance of structural walls in terms of failure modes, hysteresis curves, and contribution of fibers to shear strength. Based on the test results, recommendations are presented for FRC walls in order to achieve a lateral performance similar to that of conventional steel reinforced concrete wall for low-rise housing.

Hybrid testing of capacity designed RC structural walls for the determination of nonlinear seismic shear amplification

AbstractHybrid testing is an effective experimental method to study the dynamic behavior of structural elements under various types of loads. The hybrid testing method enables the seismic responses of large structural elements to be reproduced, such as the responses of reinforced concrete (RC) shear walls in a laboratory environment without needing to include the large masses typically encountered in multistory buildings. In this study, a test specimen corresponding to the base plastic hinge zone of an eight‐story RC structural wall was tested in a laboratory environment, whereas the remainder of the wall was modeled numerically to evaluate the seismic shear amplification due to nonlinear higher mode effects. A method is presented for controlling three degrees of freedom of a specimen with high axial stiffness and high lateral stiffness at the beginning of the test and the substantially reduced stiffness after cracking and yielding of the specimen. Because the duration of an uninterrupted test would have been very long, a method was used to stop and restart the test at will so that the whole test could be performed over several days. Seismic shear amplification due to nonlinear higher mode effects in a structural wall with yielding occurring at the base is measured for the first time in a hybrid test . The test results clearly present seismic shear amplification that is larger than building codes recommended values.

Experimental and analytical investigations into the seismic behavior and resistance of corroded reinforced concrete walls

Chloride attacks will deteriorate the physical and mechanical properties of materials and finally degrade the seismic performance of reinforced concrete (RC) structural walls. At present, there are difficulties in evaluating the seismic resistance of RC structures with walls in offshore environments due to insufficient research on the cross-fields of material corrosion and seismic performance of corroded structural walls. In this paper, accelerated corrosion tests and quasi-static cyclic loading tests were conducted on seven RC structural walls to investigate their performance under the combined influencing parameters of corrosion level, aspect ratio, axial force, and reinforcement ratio. Afterward, a modified model was proposed and verified to obtain predictions about seismic responses of corroded structural walls based on experimental data. Finally, prediction equations for lateral load resistance of corroded structural walls with different aspect ratios were derived from parametric investigation through the proposed modeling method. The comparative analysis demonstrates that the proposed model and equations produced good predictions and could be adopted to evaluate the residual seismic performance of corroded RC structural walls.

Drift Capacity at Axial Failure of RC Structural Walls and Wall Piers

A large number of reinforced concrete (RC) buildings constructed prior to the mid-1970s in earthquake-prone regions rely on lightly reinforced or perforated perimeter structural walls to resist earthquake-induced lateral loads. These walls are susceptible to damage when subjected to moderate-to-strong shaking; a number of such cases were observed in past earthquakes. Despite these observations, there are limited studies reported in the literature that investigate the loss of axial (gravity) load-carrying capacity of damaged walls and wall piers, primarily due to limited experimental data. This study utilized a comprehensive database that includes detailed information on more than 1,100 RC wall tests. To study wall axial failure, the database was filtered to identify and analyze data sets of tests on shear- and flexure-controlled walls. The findings indicated that axial failure occurs in flexure-controlled walls with special and ordinary detailing, and that axial failure mechanisms include complex phenomena influenced by various parameters. For diagonal shear-controlled walls, axial failure results from sliding along a critical crack plane extending diagonally over the height of the wall when the shear friction demand exceeds the shear friction capacity. Based on the results, expressions were developed to predict lateral drift capacity at axial failure of RC walls and piers.

Seismic response of reinforced concrete wall buildings with nonlinear coupling slabs

Reinforced concrete (RC) structural walls are widely used in high-rise buildings as the lateral force resisting system because of their inherent economy, stiffness, and strength. The floor plan configuration of residential buildings in Chile consists mainly in assemblies of large longitudinal walls and shorter transverse walls coupled by floor slabs. The coupling effect of the slabs has affected the response and the observed damage of RC buildings in recent earthquakes. The main objective of this article is to assess the seismic response of a RC structural wall building with coupling slabs. Additionally, the effect of the amount of slab reinforcement on the seismic response of the building is evaluated. To achieve the proposed objectives, seven three-dimensional models of a case study building were developed using shell-type elements in DIANA. The first four models aim to evaluate the effect of using elastic slabs with reduced (i.e. cracked) moment of inertia. The last three models consider nonlinear behavior for both walls and slabs. The response of the building was estimated using nonlinear static analysis and the seismic performance is evaluated from the results of roof displacement and shear, moment, and axial forces of the walls. Additionally, the seismic performance is evaluated from the strain demands of concrete and steel in both walls and slabs. Relevant conclusions about the building behavior, slab demands, and failure mode are drawn.

Experimental study on the effects of bi‐directional loading pattern on rectangular reinforced concrete walls

AbstractIn this experimental study, three identical reinforced concrete (RC) walls were tested under three different lateral loading patterns. These loading patterns were cyclic in‐plane, skewed with 45° angle and clover leaf. The main objective was to investigate the effects of these bi‐directional loading patterns on the seismic behavior of slender rectangular RC walls. The results showed significant increase in tensile and compressive strains in concrete and longitudinal bars that led to earlier cover concrete spalling and bar buckling in the specimens subjected to bi‐directional loading. The neutral axis depth and compression zone were found to be substantially larger when subjected to bi‐directional loading and this led to the occurrence of concrete crushing and bar buckling in the web. Moreover, lateral instability failure triggered earlier in the specimens under bi‐directional loading, as a result of reduction of out‐of‐plane stiffness of the wall. However, bi‐directional loading did not significantly increase out‐of‐plane buckling of the wall in terms of out‐of‐plane displacement. In‐plane and out‐of‐plane shear cracks formed in one of the specimens subjected to bi‐directional loading, whereas the same wall under in‐plane loading developed only flexural cracks. It was also found that in‐plane shear deformation was larger when the wall was subjected to bi‐directional loading. The results of this experimental study emphasize the need for further investigation of the effects of bi‐directional loading on RC structural walls.

Seismic Performance of Existing RC Structural Walls Retrofitted in Flexure by Wall End Plate

A study was conducted for the flexural retrofit of an old apartment house composed of a reinforced concrete (RC) shear wall structure. For the shear wall, a vertical retrofit was performed to both ends of the wall targeting the slender wall to improve the flexural performance. The retrofit materials were steel plate, epoxy, and non-shrink grout, and they were connected to the existing shear wall using post-installed chemical anchors. The concrete at the wall ends was broken and retrofitted as much as necessary to maintain the shear wall’s length. The points to be noted are the fracture of the welded part of the flexural retrofit and the chemical anchor’s pulling. After the real scale specimen was fabricated by simulating the existing shear wall, the retrofit effect was experimentally verified by breaking the wall ends, retrofitting the ends, and applying repeated cyclic lateral loads. A total of three specimens were fabricated and retrofitted using steel plates and steel tubes. Since this experiment evaluated the flexural performance, the experiment was performed with a cantilever setting. The flexural retrofit effect using steel was analyzed through the load–displacement relationship, stiffness degradation, and energy dissipation, and through this, the bond of the retrofit and the behavior of the wall were verified.

Strain Nonlinearity and Shear Lag Effect in Compressive Flange of Reinforced Concrete Structural Walls

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Reliability-Based Design Methodology for Reinforced Concrete Structural Walls with Special Boundary Elements

Reliability-Based Design Methodology for Reinforced Concrete Structural Walls with Special Boundary Elements

Experimental Evaluation of Inelastic Higher-Mode Effects on the Seismic Behavior of RC Structural Walls

Most midrise and high-rise reinforced concrete (RC) buildings rely on RC structural walls as their seismic force resisting system. The contribution of higher lateral modes to the elastic response of RC structural walls produces base shear forces significantly larger than those resulting from the static code procedure. The relative contribution of higher lateral modes increases due to an additional dynamic effect occurring while the RC wall is yielding at the base. Accordingly, the first-mode contribution saturates and reduces as its corresponding period elongates and higher modes assume a more relative contribution. This paper describes an original pseudodynamic hybrid test that has been used to experimentally measure the shear amplification during an earthquake excitation of a model shear wall structure. The experimental results show that the shear amplification factor due to nonlinear higher modes effects can be larger than 1.5. Additionally, the test results indicate that the modern structural codes appear to be conservative in calculating the shear force resistance of RC structural walls.

Empirical Expressions for Deformation Capacity of Reinforced Concrete Structural Walls

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Effect of construction joints on the seismic performance of RC structural walls

A survey of earthquake damage in reinforced concrete (RC) structural walls after the 2008 Wenchuan Earthquake in China showed unexpected phenomena at the location of a construction joint at the base of the wall, suggesting that the construction joint has an impact on the seismic performance. In this study, the test of six medium-scale RC wall specimens (height-to-length aspect ratio 2.1) with and without construction joints at the footing-wall interface were implemented under the pseudo-static reversed cyclic lateral loading, and the failure process, hysteretic response, and energy dissipation capacity were investigated. It showed that wall specimens without a construction joint exhibited better seismic performance than comparable specimens with a construction joint, mainly reflected by a higher lateral load capacity, better energy dissipation capacity, and longer plastic hinge length. A numerical model was developed using the multiple-vertical-line-element-model (MVLEM) to simulate the response of RC walls with construction joints, and walls with different axial load ratios and boundary element reinforcement ratios were studied. Results indicated that the presence of a construction joint reduces the lateral load capacity of RC wall. The influence of construction joint on the lateral load capacity is more obvious when the boundary element reinforcement ratio and axial load ratio are both low. These results show that the presence of construction joints should be considered to accurately predict the response of RC walls subjected to seismic loading conditions.

Bar buckling in ductile RC walls with different boundary zone detailing: Experimental investigation

The performance of reinforced concrete (RC) structural walls during the past earthquakes in New Zealand (2010–11) and Chile (2010) have highlighted the susceptibility of these critical structural components to several undesirable modes of failure. One such failure mode is premature buckling of the longitudinal reinforcing bars, which has also been observed in experimental tests of flexurally-dominant structural walls. This paper presents the results of an experimental program investigating the effects of transverse reinforcement detailing on buckling resistance of longitudinal reinforcement located in the boundary regions of RC structural walls. Three large-scale rectangular walls with different boundary zone transverse reinforcement detailing were tested under in-plane cyclic loading. The effects of these three types of detailing are reported in terms of drift capacity, buckling length of the longitudinal bars and cumulative energy dissipation capacity of the specimens. The test results confirm that bar buckling modes depend on transverse reinforcement detailing, which consequently also influences the ultimate flexural deformation capacity of ductile walls. By comparing the responses of the tested wall specimens, the inadequacy of code-compliant transverse reinforcement to restrain bar buckling is discussed and the effect of improved transverse reinforcement detailing (designed using a mechanics-based approach) on deformation capacity of slender walls is scrutinised.