T-shaped Walls Research Articles

Parametric Study on Seismic Performance of Slender T-Shaped RC Walls Subjected to Biaxial Loading

To investigate the effects of parameters on the seismic performance of slender T-shaped RC walls subjected to a biaxial seismic action, a numerical model was established using a fiber-based cross-section and displacement-based beam–column element. The axial load ratio, shear span ratio, flange width to web height ratio, concrete strength grade, stirrup ratio, and longitudinal reinforcement ratio were selected for the parametric study, and the effects of these parameters on the performance degradation under biaxial loading were investigated. Furthermore, a sensitivity analysis of various parameters for the decrease was conducted. The results showed that the bearing and deformation capacities under biaxial loading were both decreased, and the total energy consumption was greater than that under uniaxial loading. The impacts of different parameters and loading paths on the decrease extent were significantly different, and the overall reduction was greater in the flange direction than in the web direction. Under the square loading path, the T-shaped wall had the greatest reduction in its seismic performance, followed by the eight-shaped and cruciform loading paths. The changes in the axial load ratio, shear span ratio, and concrete strength significantly affected the performance degradation under biaxial loading. Accordingly, it is recommended to reasonably consider the values of these three parameters in a multidimensional seismic design to maintain safety redundancy.

Seismic behavior and shear capacity of shear-dominated T-shaped RC walls under cyclic loading

T-shaped walls are widely applied in tall buildings because of their high stiffness and the demand for structural layout, but the flange affects the shear performance of the wall. To investigate the shear failure mechanism of shear-dominated T-shaped reinforced concrete (RC) walls and the difference between the shear performance in the flange-in-tension and flange-in-compression directions, cyclic tests were carried out on three T-shaped RC walls. Numerical models were established for the parametric analysis of shear capacity in different loading directions, and the shear capacity calculation in various specifications was evaluated. The results showed that the failure regions of both specimens with flexural and shear failure were concentrated at the web tip, and the web tips of the shear failure specimens were more seriously damaged. Furthermore, reducing the shear span ratio significantly reduced ductility and energy dissipation capacity and increased the proportion of shear deformation to the total deformation in the plastic hinge area. The decrease in the horizontal distribution reinforcement ratio resulted in the slitting of the T-shaped wall, and the increase in deformation capacity owing to the slit wall compensated for the reduction in deformation capacity caused by the enhancement of the shear effect. Based on the results of the numerical simulation, the current codes failed to consider and distinguish the effect of the tensile and compressive flanges on the shear capacity of the T-shaped wall and were unable to predict the shear capacity of the T-shaped wall well.

Research on shear capacity of Dense-Steel-Column wall structure

Based on the previous experimental study on the shear capacity of the dense-steel-column wall (DSCW), to reveal the failure mechanism of DSCW under seismic load, the finite element analysis (FEA) of six test specimens from the experimental study is carried out, and the FEA results are compared with that of the experimental study. To further study the influences of different factors on the seismic behavior of DSCW and to calculate the shear capacity of DSCW, the parametric study is performed with 90 FEA models considering different parameters such as axial compression ratio (μ), column side length (l), and spacing to side length ratio (l/b). The results show that the local buckling failure of the columns occurs at the bottom of the wall with obvious in-plane bending deformation. Adding diagonal bracings greatly increases the stiffness of the wall, and the shear capacity of the wall with diagonal bracings decreases more slowly under the cyclic load. From the hysteresis curves and skeleton curves, it is seen that all specimens have good energy dissipation capacity and high shear capacity. With the constraint of the out-of-plane wall limb, the L-shaped and T-shaped walls have less deflection, higher shear capacity, and better energy dissipation capacity compared with that of than the |-shaped wall. The parametric study shows that the ductility decreases with the increase of axial compression ratio. The shear capacity of the wall increases with the increase of the column side length and with the decrease of the column spacing to side length ratio. In the end, the calculating formula of the shear bearing capacity of DSCW was put forward, the calculated values are in good aggreement with those of finite element analysis.

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.

Effects of biaxial loading path on seismic behavior of T-shaped RC walls

T-shaped RC walls are commonly used to resist horizontal seismic excitations in multiple directions. The differences in the intensity and spectrum characteristics of two translational components of ground motion cause the wall to experience complex biaxial displacement trajectories, resulting in a different seismic response compared to the behavior derived from conventional uniaxial cyclic tests. Thus, to investigate the seismic behavior and coupling mechanism of T-shaped walls subjected to different magnitudes of loading in two orthogonal directions, this study examined five identical T-shaped walls under uniaxial loading along two principal axes and biaxial loading with three represented loading paths. The test results showed that the mechanical behavior in one direction was significantly affected by the loading in the orthogonal direction owing to internal force redistribution and additional stress caused by the biaxial coupling bending, resulting in vertical variation and intersection of their hysteretic curves. Further, the biaxial loading primarily aggravated the cracking and damage of the flange, which accelerated the performance degradation in the flange direction and reduced the effective flange width involved in resisting web direction load. In addition, the biaxial coupling effect was found to be proportional to the area enclosed by the loading path. Thus, the most severe damage and performance degradation were observed under a square path, followed by an eight-shaped path, with the cruciform path exhibiting the least effect. Consequently, based on the results, recommendations for the design of T-shaped walls subjected to biaxial earthquake actions were proposed.

Experimental study on seismic behavior of dense-steel-column sandwich wall

This paper describes an experimental study on the seismic behavior of the dense-steel-column sandwich walls. Six full-scale specimens which are |-shaped, L-shaped, and T-shaped with or without diagonal braces were tested under low-frequency cyclic load. With the same axial compression ratio, the failure pattern of specimens without diagonal braces is as follows. There was no obvious failure phenomenon at the beginning of the test. As the increase of the horizontal displacement, the steel columns buckled in succession, and the buckling was local in the lower part. As the further increase of the horizontal displacement, the local buckling range of the columns extended till the specimen finally failed. With the same axial compression ratio, the failure pattern of specimens with diagonal braces is as follows. The braces locally buckled under the cyclic load at the beginning of the test. As the increase of the horizontal displacement, the buckling range of braces extended. As the horizontal displacement increases, the braces were fractured and the columns buckled in succession in the bottom until the specimen finally failed. The experimental results show that the diagonal braces can increase the specimens' shear stiffness and shear strength, while the braces can also improve the specimens' ductility and energy dissipation performance. The shear strength of the L-shaped wall is increased by 62.02% with the braces. The ductility coefficient of the T-shaped wall is increased by 110.58% with the braces. Additionally, it is also noted that the seismic performance of the L-shaped and T-shaped walls with end flanges is better than that of the |-shaped wall.

Experimental study of in-plane flexural behavior of screen-grid insulated concrete form rectangular and T-shaped walls

Screen Grid Insulated Concrete Form (SGICF) walls are gaining popularity in the construction of low and mid-rise buildings due to their unique constructability and insulation properties. In order to validate and ensure the safety of this novel construction system in the face of seismic loads, experimental testing aimed to provide information regarding its nonlinear behavior is of significant relevance. This paper aims to describe analytically and experimentally the in-plane flexural behavior of SGICF panels. An analytical model is presented to estimate the design parameters considering the material properties and the element geometry. Ten test specimens were constructed and tested under monotonic and cyclic in-plane lateral loading to assess the model's effectiveness. Test units were divided into two groups, each constructed using different prefabricated forms made of expanded polystyrene. The first group comprised six rectangular-shaped section walls whereas group two comprised four T-shaped section walls. All specimens were designed and detailed to obtain a flexure-controlled response, considering the presented analytical model. Results showed a ductile and stable response for all test specimens, with yielding of the longitudinal reinforcement and compression crushing of the extreme concrete fibers. This study shows that SGICF walls can reach large inelastic deformations, as well as a stable response, similar to that of conventional reinforced concrete (RC) walls with similar geometric properties. Furthermore, it was verified that flexural resistance models for solid cross-section RC members are applicable to Insulated Concrete Form (ICF) walls, taking into account section discontinuities.

Efficiency of injected anchors in connecting T–shaped masonry walls: a modelling approach

The seismic vulnerability of masonry buildings to out-of-plane failure mechanisms is frequently related to poor connections between orthogonal walls. The effectiveness of these connections represents a necessary condition to transfer the horizontal action to the in-plane stressed walls, allowing a box behaviour of the whole structure. Steel injected anchors or tie rods have been widely used in the past to improve connections between orthogonal walls, but proper analytical approaches to evaluate their effectiveness are still a matter of ongoing research. On the other hand, many seismic codes nowadays require assessing the safety improvement achieved with the strengthening interventions and the compatibility with masonry of many techniques has become a matter of debate in the light of the damage frequently caused by the same interventions. In this framework, the present paper focuses on the possibility of using injected anchors made of innovative materials, as pultruded CFRP tubes, in conjunction with traditional grout. For this purpose, a macro-block model, previously validated for the analysis of unreinforced stone masonry structures, is further developed to account for the contribution of these innovative strengthening systems in the out-of-plane response of masonry walls with T-shaped connections. The model, also considering the contributions of frictional resistances at masonry bed joints, is based on the kinematic approach of limit analysis. Literature results concerning full-scale tests of a T-shaped wall are assumed as a reference to validate the proposed approach. Then, the validated model is used to investigate the influence of some design parameters on the performance of the reinforced system and a first attempt to address the design of strengthening interventions with injected anchors is presented.

Hysteretic behavior of T-shaped walls reinforced by high-strength bars: Cyclic loading tests and modelling

The seismic performance of rectangular shear walls reinforced with high-strength bars has been studied in depth, however limited research exists on the hysteretic performance of T-shaped walls built with high-strength reinforcement. As part of this study, two T-shaped shear walls reinforced with Grade HRB600 bars, and subjected to different axial load ratios (0.05 & 0.1), were tested under cyclic loading to study their hysteretic performance. The results show that the failure in such walls is associated with concrete crushing at the free end of the web. In addition, both the strength and envelope areas of the hysteretic loops are larger in the positive loading direction when compared to those loaded in the negative direction. Moreover, the axial load ratio increases the strength, initial stiffness and energy dissipation of such walls. As part of the analytical investigation, a method to model the hysteretic response of T-shaped walls built with high-strength bars is proposed, consisting of a backbone curve and a set of empirical hysteretic rules. The backbone curve consists of a simplified quadrilinear model, represented by points at cracking, yield, peak, and ultimate. The empirical hysteretic rules are based on the Park hysteretic model. The experimental test data in this paper was used to validate the accuracy of the proposed analytical method. The results show that the analytical lateral force–displacement hysteretic curves are in reasonable agreement with the experimental curves, especially in terms of the loading and unloading stiffness, and pinching behavior.

Three-dimensional model for nonlinear analysis of slender flanged reinforced concrete walls

A new, three-dimensional, four-node, macroscopic model element for nonlinear analysis of reinforced concrete walls is developed and implemented in the structural analysis software OpenSees. The two-dimensional, beam-column formulation of the Multiple-Vertical-Line-Element Model (MVLEM) is extended by implementing the geometrical transformation of the element degrees of freedom that convert the model element from a two-node to a four-node element, and by incorporating linear-elastic element out-of-plane behavior. The three-dimensional analytical model developed, namely the MVLEM-3D, is validated based on load-deformation responses and vertical strains obtained from tests on one T-shaped wall specimen tested under uniaxial cyclic loading and four U-shaped wall specimens tested under complex multidirectional loading protocols. In addition, results of sensitivity studies on model geometric discretization and selection of an effective shear stiffness are presented. The model exhibits a high level of numerical stability and computational efficiency for all specimens investigated. Comparisons of experimental and analytical results demonstrate that the proposed MVLEM-3D captures, with good accuracy, the cyclic load-displacement behavior of non-planar walls in loading directions that are parallel to the principal axes of the cross-section. However, the analysis results overestimate the wall lateral strength in diagonal (relative to the principal axes) loading directions by 20–50%. This discrepancy is associated with the inability of the plane-sections hypothesis implemented in the model to capture the experimentally-observed nonlinear strain distributions developing along the wall cross-section due to shear lag effect. Despite this issue, the proposed model is shown to be a powerful tool for practical applications, as nonlinear response history analysis is becoming more common in engineering practice.

Analytical study of the sectional behavior and the effective width of T-shaped reinforced concrete walls

In this article, the sectional behavior (strain and stress) and the effective width in T-shaped reinforced concrete wall are analytically studied. For the parametric study, a nonlinear quadrilateral thin flat layered shell element with 6 degrees of freedom (DOF) per node for the modeling of reinforced concrete wall structures developed by Rojas et al. (2019) is used, varying the axial load (AL), longitudinal steel ratio of the web (LSRW) and flange (LSRF) boundary, aspect ratio (AR) relative to the length of the web of the wall (lw) and height of the wall (hw), and length of the flange (Lf). The parametric study is used to compare the element response that couple the axial, flexion and shear behavior, with a model that only incorporates the coupling of flexion and axial, maintaining plane sections (flexural model). Based on the parametric study, it is calibrated an analytic model of the strain profile of the tension flange of T-shaped walls. Additionally, by including the effect of shear in the model, amplification of the maximum compression strain and a reduction of the maximum tensile strain in the web is observed, mainly in squat walls. Besides, the parametric study is also used to calculate the effective width of T-shaped walls with the flange in tension, finding that it depends mainly on the length of the flange and the roof drift. After initiation of yielding in the flange, the effective width grows quickly, concluding that independent of the geometry and the slenderness, the effective width of the flange in tension covers the entire section if yielding is expected.

Seismic performance of concrete walls reinforced by high-strength bars: cyclic loading test and numerical simulation

This study examines the influence of cross-section shape on the seismic behaviour of high-strength steel reinforced concrete shear walls (HSS-RC) designed with Grade HRB 600 MPa reinforcement. As part of the study, two flexure-dominant walls with rectangular and T-shaped cross-sections, are tested under reversed cyclic loading. Seismic performance is evaluated by studying the failure characteristics, hysteretic curves, energy dissipation, ductility, and reinforcing bar strains in the two walls. As part of the numerical study, two-dimensional (2D) and three-dimensional (3D) finite element modelling (FEM) are used to predict the seismic response of the rectangular and T-shaped walls, respectively. The test results show that compared to the rectangular wall, the flange in the T-shaped HSS-RC wall increased strength, energy dissipation and stiffness, but decreased ductility. The analytical hysteretic curves calculated using 2D and 3D FEM analyses show good agreement with the experimental test results.

Cyclic Tests on T-shaped Concrete Walls Built with High-strength Reinforcement

ABSTRACT Three T-shaped concrete walls built with HRB 600 MPa reinforcement were tested under cyclic loading, and research parameters included axial load ratio and lateral loading direction. As part of the study, the method to obtain the yield strength and deformation was proposed. Test results show that compared to the specimen loaded along the web length direction, the wall loaded at 45° direction has smaller strength, initial stiffness, energy dissipation, and larger drift ratio capacity. The tension strength of HRB 600MPa reinforcement can be fully used in T-shaped walls. The method for yield strength and deformation has reasonable calculation accuracy.

High-Strength Steel Bars in Earthquake-Resistant Reinforced Concrete T-Shaped Walls

High-Strength Steel Bars in Earthquake-Resistant Reinforced Concrete T-Shaped Walls

L-shaped reinforced concrete retaining wall design: cost and sizing optimization

In the context of this study, the design of L-shaped reinforced concrete retaining walls have been scrutinized parametrically depending on the simultaneous analysis of cost and sizing with the use of a recent optimization algorithm. The differences and restrictions of L-shaped reinforced concrete retaining wall design than classical T-shaped walls have been also discussed. The foundation width and the thickness of the wall required for a safe design has been also investigated according to the change of excavation depth, the type of soil dominating field and the external loading conditions. The observed results from optimization analyses shows that the variation of the shear strength angle is the most significant soil geotechnical parameter for supplying an envisaged safe design against sliding, overturning and adequate bearing capacity. Concurrently, the excavation depth is the most important factor that is forming the necessity of the construction of the retaining structure and optimal dimension evaluation. It is also proved that the wall foundation width is the most effected dimension of the retaining structures by the change of design parameters and the cost difference is directly influenced by the change of sizing. A cost-effective wall design can be performed with the use of proposed optimization analysis is capable in a shorter time than the traditional methods. Eventually, it has shown that such optimization methods may be useful to find the optimal design requirements for geotechnical engineering structures.

Effect of ballast retaining walls on the lateral resistance of railway tracks

In this study, the application of a retaining wall was proposed as a solution for reducing the lateral displacement of the ballast layer, particularly in sharp curves and bridges. In this regard, a series of single tie push tests were performed on panels with shoulder ballast widths of 300 mm, 400 mm, 500 mm with and without the presence of L-shaped and T-shaped retaining walls. Overall, it was proven that the application of an L-shaped wall led to a 15.8% increase in the lateral resistance, and that T-shaped walls have a higher impact on the stability of the track. A shoulder width of 400 mm was proposed as the optimum width for ballasted tracks with retaining walls.

Experimental compressive behavior of novel composite wall with different width-to-thickness ratios

Double skin composite wall system owns several structural merits in terms of high load-carrying capacity, large axial stiffness, and favorable ductility. A recently proposed form of truss connector was used to bond the steel plates to the concrete core to achieve good composite action. The structural behavior of rectangular high walls under compression and T-shaped high walls under eccentric compression has been investigated by the authors. Furthermore, the influences of the truss spacings, the wall width, and the faceplate thickness have been previously studied by the authors on short walls under uniform compression. This paper experimentally investigated the effect of width-to-thickness ratio on the compressive behavior of short walls. Compressive tests were conducted on three short specimens with different width-to-thickness ratios. Based on the test results, it is found that the composite wall shows high compressive resistance and good ductility. The walls fail by local buckling of steel plates and crushing of concrete core. It is also observed that width-to-thickness ratio has great influence on the compressive resistance, initial stiffness, and strain distribution across the section. Finally, the test results are compared with the predictions by modern codes.

Response of slender reinforced masonry shear walls with flanged boundary elements under in-plane lateral loading: An experimental study

Past experimental studies have demonstrated that reinforced masonry shear walls (RMSWs) can provide adequate ductility and energy dissipation capacity when acting as the seismic force-resisting system in low-rise buildings. However, slender RMSWs used for these applications, characterized by high height-to-thickness (h/t) ratios, may be vulnerable to out-of-plane instability failure modes when subjected to in-plane seismic loading. Out-of-plane instability may develop when a wall end zone undergoes cycles of high tensile strain, followed by compressive strain during in-plane seismic loading. Out-of-plane instability has the potential to cause unexpected and rapid strength degradation, which can lead to a global collapse. Provisions of the Canadian masonry design standard CSA S304 currently aim to prevent out-of-plane instability by prescribing h/t restrictions. Relaxation provisions were introduced in CSA S304-14 for walls with flanges or boundary elements and for walls subjected to low axial stress, however these provisions have not been experimentally verified. Moreover, prescriptive h/t restrictions disregard many important factors that affect failure modes for RMSWs under in-plane reversed-cyclic loading, including the type of loading protocol (symmetrical or asymmetrical) and the effect of flanges for T-shaped walls. This paper presents a detailed experimental study on the influence of these latter two factors on the out-of-plane response of slender RMSWs subjected to in-plane cyclic loading. The testing program comprised three full-scale RMSW specimens (two T-shaped and one rectangular) subjected to reversed-cyclic loading. A displacement-controlled loading protocol was applied until the lateral load capacity of the specimen was reduced to 80% of its maximum value. The test specimens were designed to be vulnerable to out-of-plane instability, however, although significant out-of-plane displacements were observed in one of the tests, failure of the test specimens was not governed by out-of-plane instability. Detailed descriptions of the specimen responses and a discussion on the key factors affecting the out-of-plane instability failure modes are provided in the paper. The test results confirm that the out-of-plane behaviour of slender RMSWs is similar to reinforced concrete shear walls (RCSWs) in that it is significantly affected by the presence of boundary elements (e.g. [18,11,31,1]) and the type of loading protocol (e.g. [23,24]). This leads to the conclusion that seismic design and detailing provisions for preventing out-of-plane instability in RMSWs and RCSWs should consider these parameters.

Thermal Bridge Effect of Aerated Concrete Block Wall in Cold Regions

As a self-insulating building material which can meet the 65 percent energy-efficiency requirements in cold region of China, aerated concrete blocks often go moldy, frost heaving, or cause plaster layer hollowing at thermal bridge parts in the extremely cold regions due to the restrictions of environmental climate and construction technique. L-shaped part and T-shaped part of aerated concrete walls are the most easily influenced parts by thermal bridge effect. In this paper, a field test is performed to investigate the scope of the thermal bridge effect. Moreover, a heat transfer calculation model for L-shaped wall and T-shaped wall is developed. According to the simulation results, the temperature fields of the thermal bridge affected regions are simulated and analyzed. The research outputs can provide theoretical basis for the application of aerated concrete wall in extremely cold regions.

Partial Insulation of Aerated Concrete Wall in its Thermal Bridge Regions

As a self-insulating building material which can meet the 65 percent energy-efficiency requirements in cold region of China, aerated concrete blocks often go moldy, frost heaving, or cause plaster layer hollowing at thermal bridge parts in the extremely cold regions due to the restrictions of environmental climate and construction technique. In this paper, partial insulation measures of the thermal-bridge position of these parts of aerated concrete walls are designed to weaken or even eliminate thermal bridge effect and improve the temperature of thermal-bridge position. A heat transfer calculation model for L-shaped wall and T-shaped wall is developed. Based on the simulation result, the influence of the thickness on the temperature field is analyzed. Consequently, the condensation inside self-thermal-insulating wall and frost heaving caused by condensation and low temperature will be reduced, avoiding damage to the wall body from condensation..