RC Walls Research Articles

Machine learning approaches for lateral strength estimation in squat shear walls: A comparative study and practical implications

This study investigated the influence of input parameters on the shear strength of RC squat walls using machine learning (ML) models and finite element method (FEM) analysis. The analyses were conducted on the largest currently available dataset of 639 squat RC walls with a height-to-length ratio of less than or equal to 2.0. The findings suggest that ensemble learning models, specifically XGBoost, CatBoost, GBRT, and RF, are effective in predicting the shear strength of RC short shear walls and using Bayesian Optimization for hyperparameter tuning improves their performance. The axial load had a greater influence on the shear strength than reinforcement ratio, and longitudinal reinforcement had a more significant impact compared to horizontal and vertical reinforcement. The performance of XGBoost model significantly outperforms traditional design models such as ACI 318-19, ASCE/SEI 43-05, and Wood 1990. Additionally, reducing the number of input features from 13 to 10, 8, or 6 still yields reliable predictions with high accuracy. The finding suggests that the use of XGBoost models provides not only comparable accuracy to FEM simulations with non-linear pushover analysis but also the first one can predict the lateral strength in the case of incomplete data which could not be done by FEM. A web application incorporating XGBoost model with various input features can provide valuable insights for predicting the lateral strength of squat shear walls in building structures.

Effect of Combined Blast and Fragment Loading on RC Wall and Its Mitigation Using Composite Sections

Effect of Combined Blast and Fragment Loading on RC Wall and Its Mitigation Using Composite Sections

Efficient three-dimensional shear-flexure interaction model for reinforced concrete walls

This paper describes the formulation of a computationally stable and efficient shear-flexure interaction model for reinforced concrete walls. The model is derived by combining two previously available models, a two-dimensional E-SFI model, and a three-dimensional SFI-MVLEM-3D model. The major enhancement in the model formulation compared to its parent SFI-MVLEM-3D comes from the implementation of a closed-form solution for the calculation of horizontal axial strains at fibers of the wall element. This significantly reduced the number of element degrees of freedom, which resulted in analysis run-time that is reduced to approximately 25% and convergence rate that is increased roughly two times. Validation of the developed analytical model is performed using test results obtained from a slender, flexure-controlled, C-shaped RC wall specimen tested using multidirectional loading protocol, as well as two squat, shear-controlled, box-shaped wall specimens subjected to unidirectional cyclic loading. The comparison of analytical and experimental results revealed that the proposed model captures with good accuracy the stiffness and lateral load capacity of all examined wall specimens under cyclic loading. Model accuracy when predicting contributions of shear deformations was also good, while vertical strains are predicted with reduced accuracy mostly due to plane-sections assumption implemented in model formulation. The proposed analytical model is implemented in computational platform OpenSees.

Method and Experimental Study of Oscillator Frequency Optimization of Distributed Tuned Mass Dampers for Broadband Multimodal Vibration Mitigation of Reinforced Concrete Wall

Distributed tuned mass dampers (dTMD) can effectively mitigate the broadband vibration of a structure. However, when the vibration frequency in question reaches several hundred hertz, traditional optimization methods represented by fixed point theory are difficult to apply due to dense modal density, complex boundary conditions, and vibration inputs. This paper proposes the minimax method based on modal damping to optimize the oscillator’s frequency. Two typical wall panel specimens are tested to evaluate the proposed method. The mode shape of the uncontrolled wall and the vibration mitigation effect of the stacked sandwich-damped TMD under single-point bidirectional excitation is tested. The correlation between the modal damping and the vibration mitigation effect is evaluated. The results show that the RC wall panel has a dense mode when the frequency of interest reaches 300 Hz and above; the distributed stacked sandwich-damped TMDs can effectively mitigate the vibration of the RC wall panel in the frequency range of 200~450 Hz; and that the idea of optimizing the frequency of dTMD based on modal damping is feasible.

Behavior of reinforced concrete walls with integrated tubing system

AbstractA novel tuned liquid wall damper (TLWD) system was developed by incorporating liquid‐filled tubes within concrete walls to improve structural performance versus motion. However, the placement of the hollow tubes within a concrete wall introduces voids, and their effect on the general structural performance of the multifunctional concrete structure is not well understood. The objective of this paper is to further the understanding of reinforced concrete walls equipped with such tubing systems. To this end, experimental testing was performed on three pairs of reinforced concrete walls with circular openings. One pair was tested for four‐point bending, one for axial compression, and the other for pushover. Cracking, failure load, and failure mode were monitored during testing. Finite element (FE) models were developed and correlated with testing results, and results numerically compared against conventional, solid concrete walls also through FE modeling. Results showed that concrete walls with circular opening performed similarly to solid walls for strength, whereas the reduction in strength caused by the tubes did not have significant adverse effects. The strength reduction of the RC wall panel with integrated tubing system is dependent on the configuration of integrated tubing system and the loading condition such as bending moment, axial compression, and in‐plane shear. Finally, the strengths of the walls with openings were calculated following ACI Code, which were compared with those from the test. Overall, results showed that a tuned liquid column damping system can be integrated within a concrete wall to create a TLWD, with the wall preserving its structural function.

EXPERIMENTAL STUDY ON PROPERTIES OF SHEAR WALL USING STEEL FIBER REINFORCED CONCRETE UNDER IN-PLANE LATERAL FORCE

In-plane lateral loading tests were conducted to investigate the structural performance of SFRC shear walls. The test results revealed that steel fiber reinforcement mitigated damage to the walls and enhanced their shear capacity. The number of shear cracks on the SFRC walls at an interstory-drift angle of 1/200 was twice as significant as on the RC wall, and the maximum and residual crack widths were approximately half. Shear stiffness degradation after cracking reduced as the steel-fiber volume ratio increased. 0.5% and 1.0% steel-fiber volume ratios increased the maximum shear capacities by 11% and 17%, respectively.

Post-earthquake performance and damage evaluation of self-centering shear wall with replaceable devices

Self-centering structures have been demonstrated to be an effective method by which to improve seismic resilience. Most related research is focused on the seismic performance of self-centering structures without initial damage, whereas the post-earthquake performance of structures, which is significant for their repair and operation, is less investigated. Based on this, this study aims to evaluate the post-earthquake behavior and explore the damage evolution of a novel self-centering shear wall with replaceable devices, including disc springs to apply restoring force and friction pads to dissipate energy. Cyclic loading tests were conducted on two intact self-centering shear walls to investigate their seismic performance in our previous studies, and limited damage was observed after the tests. Thus, in this study, cyclic loading was directly applied to the two damaged self-centering shear walls to obtain their post-earthquake performance. The results indicate that the damaged self-centering shear walls exhibited satisfactory seismic behavior; their bearing capacity was reduced at small drift ratios as compared to that of the intact specimens, whereas no decrease of their bearing capacity occurred even at a 3% drift ratio. Moreover, the damaged self-centering shear wall exhibited appreciable energy dissipation and self-centering capabilities, and the residual drift ratio was less than 0.5% at a 2.1% drift ratio. However, the damage at the bottom of the RC wall after the post-earthquake test was obvious, revealing that the novel self-centering RC shear wall would need to be repaired after several earthquakes. Therefore, two effective methods were further developed to improve the post-earthquake performance of the novel self-centering shear wall.

Seismic retrofit of reinforced concrete shear walls using fibre reinforced polymer composites

This study studies seismic retrofitting of RC shear walls with externally linked aluminium tube polymers (CFRP). Three stages complete the research study. This method examined two eight-story CFRP-repaired RC shear walls. Excited walls were tested. The wall design was considered in NBC and CSA-A23.3–04. Throughout. The École polytechnique de Montréal's shake table simulated earthquakes to assess wall seismic resistance. Vibrations make the sixth panel more demanding and nonlinear. Panel six finished the tale. The earth's surface and twelfth-level walls were repaired and retested on a shaking table with varying ground motion excitation levels. Ground motion stirred the walls toward the end. Phase 2 involved the erection of three RC shear barriers. My college Structures Laboratory evaluated cyclic lateral stimulation panels. Evaluate the panel's performance. Two FRP panels and the control wall were tested. These panels were evaluated to determine the optimal method. All three ceiling tiles have code-designed parts, including the sixth-story stiffener panel. All building shear walls exceed construction criteria; hence, all wall panels have these features. These walls can handle the eight-story shear stresses. Continuous axial load, synchronized cyclic moment, and shear force were tested on the top panel. The panel could withstand all three forces. FRP retrofitting improved the wall panels' flexural and shear strengths. FRP retrofitting failed. Third, a computational macromodel simulated gripping and recycling wall panels under cyclic pressures. This simulation determined the longer-lasting wall panel type. Control wall panels were tested to discover whether they outperformed retrofitted ones. The two existing RC shear walls and three RC wall panels' FRP-retrofit schemes performed well and enhanced flexural strength, proving the retrofit's key aims. The quadratic numerical macromodel recreated monotonic and cyclic responses in wall panels under cyclic stresses. Nonlinear effects were accounted for using the nonlinear model.

Investigating the impact of design criteria on the expected seismic losses of multi-storey office buildings

The Ministry of Building, Innovation and Employment is developing advice on how to deliver Low Damage Seismic Design (LDSD) protection for buildings through their Tū Kahika: Building Resilience platform. The draft LDSD advice is considering a design drift limit for multi-storey buildings of 0.5% as part of new damage control limit state design checks. The potential impact of this design criterion on the expected annual loss due to repair costs is investigated for generic reinforced concrete wall case-study office buildings of 4- and 12-storeys in both Wellington and Christchurch. The equivalent static method, in line with NZS 1170.5 and NZS 3101, was used to design the buildings to conventional and draft LDSD specifications, representing current and future state-of-practice designs. The draft LDSD advice aims to limit the expected annual loss of complying buildings to below 0.1% of building replacement cost. This research tested this expectation. Losses were estimated in accordance with FEMA P-58, using building responses from non-linear time history analyses. Although it is found that the new drift limit alone may not limit seismic losses to the target values owing to damage to acceleration-sensitive elements, the results do support the intentions of the draft design advice to significantly reduce the expected seismic losses of complying buildings. The study also highlighted the importance of using an accurate approximation of RC wall stiffness for LDSD, and provides insight into different design strategies that could be followed to effectively limit losses in RC wall buildings as part of LDSD.

Investigation of the behavior of slender reinforced concrete walls with complex configurations using nonlinear finite element analysis

Slender RC walls are used commonly in mid- and high-rise buildings to resist lateral loads arising from earthquakes and wind forces. To accommodate architectural constraints, facilitate construction, and maximize structural efficiency, the majority of these walls have complex configurations, comprising planar and non-planar wall elements that often include regular or irregular patterns of openings. To date most laboratory testing of slender RC walls has employed wall specimens with relatively simple configurations and without openings and coupling action which provides only limited understanding of the impact on performance of the variations in configuration and reinforcement detailing observed in real-world construction.This study presents a 3D continuum modeling approach to improve understanding of the behavior of walls with complex configurations and support recommendations for design of these systems. Planar wall data were used to calibrate the continuum-type modeling approach; experimental data characterizing the response of non-planar walls and walls with openings are used to validate the model.

Performance of Medium-Rise Buildings with Reinforced Concrete Shear Walls Designed for High Seismic Hazard

This work has evaluated the collapse fragility of a typical Chilean building for residential use, structured based on shear-resistant RC walls and inverted beams arranged along its entire perimeter, using the incremental dynamic analysis (IDA) for the evaluation of its structural behavior, using for this the 2018 version of the SeismoStruct software. This method evaluates the global collapse capacity of the building from the graphical representation of its maximum inelastic response, obtained through a non-linear time-history analysis, against the scaled intensity of a set of seismic records obtained in the subduction zone, thus creating the IDA curves of the building. The processing of the seismic records is included within the applied methodology to make them compatible with the elastic spectrum of the Chilean design, achieving an adequate seismic input in the two main structural directions. In addition, an alternative IDA method based on the elongated period is applied to calculate the seismic intensity. The results of the IDA curve obtained with this procedure and the standard IDA analysis are analyzed and compared. The results show that the method relates very well to the structure's demand and capacity and confirms the non-monotonous behavior exposed by other authors. Regarding the alternative IDA procedure, the results indicate that the method is inadequate, failing to improve the results obtained by the standard method.

Efficient boosting-based algorithms for shear strength prediction of squat RC walls

Reinforced concrete shear walls have been considered as an effective structural system due to their optimal cost and great behavior in resisting lateral loads. For the slender type of these walls, failure modes are mainly related to flexure, while for the squat type with height-to-length ratios less than two, shear is the dominant factor. Thus, accurate estimation of shear strength for squat shear walls is necessary for design applications and can also be complex due to the various effective parameters. In order to address this issue, first a comprehensive dataset with 558 samples of squat shear walls is conducted, and three hybrid models consisting of genetic algorithms and boosting-based ensemble learning methods, i.e., XGBoost, CatBoost, and LightGBM, are used for estimation of shear strength. The results showed high prediction accuracy, with a coefficient of determination of at least 98.6% for all three models. Genetic algorithm has been proven to be an effective method for tuning boosting-based algorithms compared to manual testing. In addition, the results of the algorithms are compared to their default hyperparameters and other conventional regression Models. Also, multicollinearity and principal component analysis (PCA) were studied. Furthermore, the performance of three tuned models is compared with that of a mechanics-based semi-empirical model and other genetic programming (GP)-based models. Finally, parametric and sensitivity analyses were performed, to demonstrate the ability of the models to identify the most critical parameters with significant influence on shear strength.

Seismic performance evaluation of steel and GFRP reinforced concrete shear walls at high temperature

Fire-induced structural damage to the seismic performance of reinforced concrete shear walls is critical in the event of a fire-earthquake scenario. However, only few researchers have studied the seismic performance of reinforced concrete shear walls at high temperatures. This study focuses on the seismic performance of fiber reinforced concrete shear walls at high temperatures by using finite element (FE) software, ABAQUS. The experimental test available in a literature on seismic behavior of shear walls exposed to fire and thermal properties of glass fiber reinforced polymer (GFRP) bars were used to validate the FE model and showed good agreement and thus used in the simulation.The FE results showed that exposure of RC shear wall to fire reduced the strength of the wall. The strength of walls at the maximum applied drift of 3.2% with concrete cover thicknesses of 20 mm, 25 mm, and 30 mm was dropped by about 70%, 76%, and 85% of the reference shear wall, respectively. Similarly, the strength of RC walls was reduced by about 80%, 75%, and 68% of the reference shear wall for the duration of fire exposure of 30 min, 60 min, and 120 min, respectively. Additionally, the strength of walls due to one side, two sides, or all sides’ exposure to fire was decreased by about 68%, 56%, and 50% of the reference shear wall, respectively. It can generally be concluded that the fire exposure sides has largely affected the strength of the shear wall compared to the other parameters and GFRP bars were more sensitive to temperature than steel bars.

Experimental and numerical investigation on the seismic behaviors of RC shear walls with multiple post-openings before and after strengthening by steel plates

In this paper, the quasi-static tests of seven RC shear walls and the corresponding finite element simulations were carried out to investigate the seismic behaviors of the RC shear walls with multiple post-openings before and after being strengthened by bonding steel plates, including failure modes, bearing capacities, ductility, energy dissipation capacities, structural performance levels, and also the strain distribution of the rebars. The detail arrangements of the post-construction openings are taken into account, on the premise of the same total area of the openings. Not only in the tests but also in the simulations, there is one RC wall with a single post-opening in the center of the wall, one RC wall with two post-openings that are horizontally arranged at the mid-height of the wall, and one RC wall with two post-openings which are vertically arranged at the mid-length of the wall. In addition, other three specimens, with the same opening arrangements as the three types of RC walls motioned above, strengthened by bonding steel plates around the openings, and one shear wall without openings for reference were fabricated. The results showed that the failure modes of reinforced or unreinforced RC shear walls with post-openings are shear failure and flexural shear failure respectively. The seismic bearing capacities of the shear walls with post-openings can be obviously recovered, up to 33.5%, by bonding steel plates. Moreover, the ductility coefficients of those strengthened RC walls were also improved, in the range of 5.6% to 58.1%.

Flexural test for steel-concrete composite walls (aspect ratio 2.0) with steel U-Section boundary element

For high structural performance and constructability, a steel–concrete composite wall with boundary elements of steel U-section was developed. In the present study, cyclic lateral loading tests were performed to investigate the flexural performance of the proposed walls. Test parameters were the type of boundary element, area of steel U-section, and type of web reinforcement. The boundary steel U-section not only provided high flexural strength, but also provided lateral confinement to the boundary concrete and restrained shear sliding of the web concrete. Thus, the flexural strength, deformation capacity, and energy dissipation were significantly greater than those of the counterpart RC wall with conventional boundary reinforcement. Such advantages were pronounced when steel U-section with larger area was used. Further, the use of steel plate beams restrained diagonal cracking and spalling of the web concrete, thus improving the deformation capacity. As strain hardening stress after yielding was developed in the boundary steel section, the strength of the test specimens exceeded the nominal flexural strength based on plastic stress distribution.

Shortcomings of shear wall design as per IS:13920–2016

Reinforced concrete shear walls are almost routinely used in multi-storeyed buildings due to their increased strength, stiffness, and ductility considerations. Shear walls are typically stiffer than regular frame elements. Hence, are subjected to more lateral forces during response to earthquakes. Reinforced concrete walls subjected to compression along with flexure are similar to columns and hence need similar methodology. For a section subjected to compression and flexure, two equilibrium conditions namely force and moment equilibrium equations needs to be solved for any specific load combination. This being a cumbersome and complex proposition, design charts, similar to columns should be used for shear wall design. However, IS 13920:2016 provides closed form expressions for estimation of moment capacity of rectangular RC walls without boundary elements combining these two equilibrium equations by using certain assumption and simplifications which are not conforming to the fundamental philosophies of limit state method as per IS 456–2000. These closed form expressions have several limitations and constraints and the equations are not valid for all the probable positions of neutral axis. In the present work the shortcomings of the codal methodology of shear wall design have been highlighted and method of development of proper design aids for shear wall design have been outlined.

Seismic performance of flanged RC walls under biaxial cyclic loading

Flanged RC walls are frequently utilized to provide strength and stiffness in two horizontal directions, yet the coupling of the bidirectional horizontal components of ground motion are bound to have large impact on the seismic response of flanged walls. However, few data exist characterizing the performance of flanged walls subjected to biaxial cyclic loading. Aiming to provide an insight into the influence of the biaxial coupling effect on the seismic behavior of flanged RC walls, three T-shaped and two L-shaped walls were tested under uniaxial and biaxial loading. Subsequently, a finite element model was employed for parametric studies and generating numerical data for a detailed comparison of the seismic performance of the flanged walls under uniaxial and biaxial loading. The results showed that the coupling of alternating loadings in orthogonal directions intensified the cracking and damage of flanged walls, resulting in the reduction of the bearing and deformation capacities, an increase in the proportion of flexural deformation in the plastic hinge area, acceleration of the energy dissipation process, and a more significant shear lag effect as opposed to uniaxial loading. Furthermore, the damage aggravation as well as reduction in seismic performance of L-shaped wall due to the biaxial coupling effect were more obvious than that of T-shaped wall. Based on the test and numerical results, the reduction of the ultimate inter-story drift ratio caused by biaxial loading was quantified through statistical analysis and the derived reduction factors can provide reference for the performance-based seismic design and anti-collapse design of flanged RC walls under multi-dimensional seismic action.

Experimental Study on Seismic Behavior of Coupled Steel Plate and Reinforced Concrete Composite Wall

The coupled steel plate and reinforced concrete (C-SPRC) composite wall is a new type of coupled-wall system consisting of steel coupling beams (SCBs) that join two SPRC walls where the steel plate shear wall (SPSW) is embedded in the RC wall. Although the C-SPRC wall has been extensively constructed in high-rise buildings in seismic regions, research on its behavior has rarely been reported. No code provisions are available for directly guiding the preliminary design of such coupled-wall systems. In the research, three 1/3-scaled C-SPRC wall subassemblies including one-and-a-half stories of SPRC walls and a half-span of SCB were tested under simulated earthquake action, considering the fabrication method of the embedded SPSW and the shear-span ratio of the SPRC walls as two test variables. The prime concern of the research was to evaluate the influences of those popular design and construction parameters on the seismic behavior of the C-SPRC wall. Deviating from the beam tip loading method used in conventional subassembly tests, the lateral cyclic load in this research was applied at the top of the wall pier so that the behaviors of both walls and SCBs could be examined. The test results exhibited the great seismic performance of the subassemblies with the coupling mechanism fully developed. The energy dissipation capacity and inter-story deformation capacity of the subassembly with the assembled SPSW were roughly 9.4% and 13.2% greater than those with the conventional welded SPSW. Compared with the subassembly with the shear-span ratio of 2.2, the interstory-deformation capacity of the one with the shear-span ratio of 2.0 was increased by approximately 13.4%, while the energy dissipation capacity was decreased by 10.9%. The test results were further compared with the simulation results using the proven-reliable finite element analysis with respect to the hysteretic curves, skeleton curves, energy dissipation capacities and failure patterns.

Finite Element Analysis of Axially Loaded RC Walls with Openings Strengthened Using Textile Reinforced Mortar for Sustainable Structures

Sustainable solutions in the building construction industry promotes the use of innovative materials such as textile reinforced mortar (TRM) as a strengthening technique resulting in a reduced life-cycle cost. This paper presents a nonlinear finite element analysis (FEA) of TRM strengthened RC walls with cut-out openings under axial loading. FEA models were developed and validated with two experimental tests from the literature. Subsequently, a parametric study was performed to investigate the contribution of TRM in strengthening RC walls considering various opening sizes, types, numbers and orientations of window openings, and TRM strengthening configurations. The parametric study results revealed that strengthened models with smaller opening sizes had higher axial strength enhancement. Furthermore, the increase in the axial load capacities of walls with door and window openings were 34 and 26%, respectively, as compared to the corresponding control ones. TRM was more effective with a lower opening aspect ratio (Ho/Lo). In addition, confining the wall piers with U-shaped TRM jackets was the most effective configuration in improving the walls’ axial strengths with maximum enhancements of 16 and 22% as compared to the models strengthened with side-bonded sheets and strips, respectively. Finally, the axial strengths of the FEA models were also compared with the existing empirical solution and showed reasonable correlation with an average discrepancy of 15%.

Experimental Investigation on the Cyclic In-Plane Behavior of GFRP-Reinforced Concrete Shear Walls

The current study presents an experimental investigation performed on slender reinforced concrete shear walls, representing a common lateral-load resisting system of mid-rise buildings. The walls were reinforced with steel and glass fiber-reinforced polymer (GFRP) bars and tested up to failure under reversed quasi-static cyclic loading to investigate the capability of GFRP bars in reinforcing RC shear walls under seismic loads. Moreover, the effect of the GFRP reinforcement ratio on the structural response, deformation performance, and failure mode resulting in RC walls, compared with its behavior when reinforced with steel bars, is also investigated. Six full-scale shear walls with an aspect ratio of 3.25 were constructed. The reference wall was entirely reinforced with steel bars. Two specimens were reinforced by hybrid scheme of GFRP–steel bars. The remaining three shear walls were entirely reinforced with GFRP bars. The overall performance of each wall was characterized by investigating the lateral load capacity, hysteretic response, cracks propagation, ductility, and the behavior of energy dissipation. The experimental results showed that GFRP-reinforced concrete walls had an elastic behavior characterized by a stable hysteretic response with recoverable deformation of more than 80% of the ultimate load. However, sudden and brittle failure was attained for the wall with a high GFRP reinforcement ratio. GFRP decreases the displacement ductility of the shear walls by an average of 32.9%, depending on the reinforcement ratio, compared to that reinforced by steel bars. Moreover, lower energy dissipation through inelastic deformation was obtained for the walls reinforced with GFRP bars. Nonetheless, when GFRP bars are combined with steel bars, acceptable levels of dissipated energy are attained compared to the steel-reinforced wall.