Lateral Load Displacement Research Articles

Experimental and Numerical Investigation of Unreinforced Masonry Walls with and without Opening

ABSTRACT This paper comparatively addresses the numerical modeling techniques for simulating the nonlinear behavior of unreinforced masonry (URM) walls. An experimental test program including two specimens with and without opening was conducted to document the behavior of the specimens. Both specimens were subjected to constant axial load and monotonically increasing in-plane lateral load during the tests. Two different modeling approaches, macro and detailed micro modeling, were considered to develop the finite element models (FEMs) of URM walls. The numerical simulation was performed using ABAQUS finite element software. The results of both modeling strategies were compared with experimental results in terms of the lateral load–displacement response and crack pattern of URM walls. Based on the comparison, the approaches implemented for numerical analyses are found reasonably applicable for simulating the in-plane response of URM walls with and without opening under lateral load.

Experimental research on seismic performance of steel fiber-reinforced recycled concrete-filled circular steel tube columns

To study the seismic performance of steel fiber-reinforced recycled concrete-filled steel tube (SRACFST) columns, 14 circular specimens with different replacement rates (Rp) of recycled coarse aggregate (RCA), volume fractions (Vf) of steel fiber, axial compression ratios (n), steel tube thickness (t), and concrete strengths were tested to failure under constant axial and lateral cyclic loads. All the specimens exhibited a similar typical compression bending failure mode. Subsequently, the effect of different parameters on the various seismic characteristics in terms of the lateral load-displacement (P−Δ) hysteresis curve, skeleton curve, ductility, stiffness degradation, strength degradation and energy dissipation were obtained and studied comprehensively. The results indicated that the addition of steel fiber to core concrete can effectively compensate for the marginal negative influence of the defects of recycled aggregate concrete (RAC). Furthermore, the lateral bearing capacity, ductility, and energy dissipation capacity were improved as the steel fiber fraction increased. An increase in the thickness of the steel tube resulted in a remarkable improvement in the overall seismic behaviour. However, a higher axial compression ratio resulted in inferior seismic performance, particularly in terms of the deformation capacity and ductility. The bearing capacity and energy dissipation improved as the concrete strength increased. However, the ductility, stiffness stability, and strength stability weakened. The equivalent viscous damping index corresponding near failure attained 0.281–0.414, and the ductility was higher than 3.0. This demonstrated that the SRACFST columns could be used in load-bearing structures in seismic regions. The Code AIJ-2001 was recommended to calculate the compression bending bearing capacity of SRACFST columns under cyclic seismic loading, with an expansion index of 1.15 for calculation accuracy. Further, the fiber modelling (FM) method was established to predict the skeleton curves. The calculated results matched the experimental results well, and this indicated the relevance of this method for further elastoplastic analysis of SRACFST columns during earthquakes.

Numerical Studies on CFRP Strengthened Cold formed Steel built-up Columns

This paper reports the numerical investigation carried out on the Cold-formed steel (CFS) built up columns strengthened with a Carbon fiber-reinforced polymer (CFRP) by using Finite element software ABAQUS/CAE. The CFS sections used in the investigation are built-up Cold formed box sections connected together by screws. Totally 24 columns are considered for the analysis in that twelve columns used are plain CFS and other 12 columns used are CFRP strengthened CFS columns. The geometric properties of the materials considered as 0.6 mm, 0.75 mm and 1 mm thickness with 300 mm, 500 mm and 700 mm depth respectively. All the built-up columns were modeled and analysed using ABAQUS software. From the analysis results, the Ultimate load capacity, buckling behavior and Load-lateral displacement of the Plain and CFRP strengthened columns are obtained and presented in this paper. It is also noted that the numerical results obtained from the ABAQUS software is in good agreement with the experimental results.

Hysteresis behavior of 3D RC exterior beam-column joints strengthened with CFRP sheets and spike anchors

Full-scale 3D exterior beam-column joints lacking shear reinforcement but externally shear-strengthened with carbon fiber reinforced polymer (CFRP) sheets were investigated with respect to their behavior under both gravity and lateral cyclic loadings. For this purpose, three such joints including one control and two experimental ones (strengthened either with CFRP sheets or with both CFRP sheets and spike anchors) were subjected to relevant tests. Prior to CFRP installation, all the externally strengthened specimens were subjected to surface preparation and grooving in order to prevent possible CFRP debonding. The flexural capacity of both the non-strengthened and strengthened joints were estimated using a specially-developed analytical method. Comparisons of the lateral load–displacement hysteresis curves and in the test results revealed that, compared to the control, the externally strengthened joints showed enhancements of 30, 222, and 200% in lateral load-bearing capacity, energy dissipation, and secant stiffness, respectively. It was further found that despite the efficacy of the shear retrofit design proposed for 3D exterior connections, those strengthened with the combined CFRP sheets and spike anchors outperformed the ones solely strengthened with CFRP sheets. The sectional analysis results also revealed that the simple method proposed in this study is well capable of estimating bearing capacity in both the control and strengthened connections with reasonable accuracy.

Experimental tests on built-up cold-formed steel section laced compression members

This paper presents the detailed results of the first experimental tests investigating the behaviour and strength of axially loaded built-up cold-formed steel laced compression members, wholly assembled using Gas-Shielded Metal Arc Welding. The built-up laced test specimens consisted of two longitudinal cold-formed carbon steel channels (chords) placed back-to-back with an internal gap and connected using end batten plates and two parallel planes of single lacing systems. The compression tests were performed using built-up laced members with similar lengths but with various back-to-back gap distance. The compressive strengths, modes of failure and deformed shapes at failure were observed in the tests and reported in this paper. In addition, the load-axial shortening, load-lateral displacement, and load-axial strain relationships were also measured and reported. Overall, the new tests on built-up laced members compensated the lack of data on this form of construction and provided valuable experimental information in terms of buckling behaviour and compressive strength which may be powerfully used to develop nonlinear 3-D finite element models. The compressive strengths measured experimentally were compared against the design strengths determined using the North American Specification, Australian/New Zealand Standard and European Code for the design of cold-formed steel structures. Generally, it is shown that the specifications were accurate for the built-up cold-formed steel section laced compression members except for those failing mainly by overall buckling, where the specifications were considerably conservative.

The influence of flexible sound insulation layers on the seismic performance of cross laminated timber walls

This paper presents the results of an experimental campaign investigating the seismic behaviour of full-size cross laminated timber (CLT) wall systems with sound-insulated shear-tension angle brackets. The main aim of the study was to investigate the influence of more and less flexible soundproofing bedding under the CLT wall. The paper shows a comparison of lateral load-bearing capacity, displacement capacity, ductility and stiffness obtained from racking tests on uninsulated specimens and specimens with various types of bedding insulation and levels of vertical load. Moreover, an analytical procedure to estimate the lateral load-displacement response of CLT walls with bedding insulation is proposed. This model is verified by direct comparison to the experimentally determined lateral load-displacement backbone curves. The results show that the elastomeric bedding does not have a significant effect on the bearing capacity of the wall system tested, but it reduces the stiffness and increases the displacement capacity. Due to the large decrease in stiffness, the insulation causes an overall reduction in ductility. The analytical estimation proposed was able to capture the reduction in lateral stiffness and adequately predict the load-bearing capacity. • Monotonic and cyclic shear tests of walls, analytical model. • The insulation does not significantly influence the lateral load-bearing capacity. • The insulation reduces the lateral stiffness of the wall and overall ductility. • High vertical load can cause irreversible deformation of the CLT slab and insulation. • The analytical model adequately predicted the lateral load displacement response.

Comparative Study of Existing Cement Fly Ash Gravel pile and Encased Stone Column Composite Foundation

The Cement Fly Ash and Gravel (CFG) Pile and Encased Stone Column (ESC) are the ground improvement techniques. The main object of the study is to the numerical analysis of the Both techniques pile group were used to support the Embankment with and without the geotextile both techniques composite foundation by the Finite Element method under static and dynamic load analysis. Numerical simulation has been carried out in Plaxis 3D. A case study from china’s highspeed embankment supported by CFG and ESC have investigated the load caring capacity by soil and pile. While the failure behaviors, settlement, excess pore pressure, and lateral behavior with variable embankment loading and number of geosynthetic effect moreover, the diameter of CFG piles and ESC at various locations in an embankment has been varied to study its influence on the load distribution among the CFG piles/ESC and lateral load displacement of the pile group. The results show that increasing the diameter of both techniques reduced the total settlement and differential settlement of embankment. It observed that the seismic load has a significant effect on the vertical and lateral displacement.

Experimental study of seismic performance of precast shear wall with a new bolt-plate connection joint

Precast shear wall (PSW) have been widely used in structure construction. The connection of the precast part plays an important role in the seismic performance of the PSW. To improve the seismic performance and satisfy various important requirements of the PSW, this paper develops a new bolt-plate connection joint assembled by the high strength bolt with embedded steel plate in the PSW. Experimental study of four shear wall specimens, including one cast-in-situ integral specimen and three PSW specimens with different axial compression ratio, was conducted to investigate the seismic performance of the proposed bolt-plate connection joint under low cyclic loading. The key indexes including horizontal load-lateral displacement curve, skeleton curve, stiffness degradation, strain distribution of connecting device and steel bar are investigated. Results shows that the PSW with the proposed bolt-plate connection joint performed similar failure mode compared to that of the cast-in-situ shear wall (CISSW). The loading-carrying capacity of the PSW with the proposed bolt-plate connection joint is nearly equivalent to that of the CISSW. Note that the proposed connection joint can effectively improve the plastic deformation capacity of the PSW and also enhance the seismic performance and satisfy construction.

Examination of Anchorage of Mesh Wire on Seismic Response of Infilled Walls in RC Frames

The infill walls may lose their positive effects during the first stages of earthquakes, either by leaving their plane or through breakage. That is why it is common to strengthen these walls before design earthquakes or to repair and strengthen them after suffering slight or moderate damage due to the occurrence of an earthquake. In this study, the effect of adding and strengthening these walls on the structural behavior of reinforced concrete structures was investigated. For this purpose, the infill walls were strengthened with a single mesh of reinforcement and covered with plaster. Five one-story, single bay and ½ scaled reinforced concrete frames were cast, one was built without infill, the second with a bare infill wall, and the other three with strengthened infill walls with anchorage of different diameters. All these specimens were tested under cyclic loading type reverse. The tests resulted in important relationships and curves, including the lateral load-lateral displacement, envelope curve-lateral load and lateral displacement, as well as stiffness- lateral displacement and others. Through these results, the effect of adding infill walls and the strengthening procedure of these walls on the structural behavior of the structures was discussed.

Cyclic shear displacement model for reinforced concrete columns

Lateral response of reinforced concrete (RC) columns can be modeled and simulated considering three displacement components: flexural displacement, displacement due to slippage of longitudinal bars at column ends, and shear displacement. The incorporation of shear displacement in a computational model is essential for accurate calculation of lateral load–displacement relationship. The contribution of shear displacement can be significant for RC columns with low displacement capacity or ductility. An easy-to-apply shear displacement model is proposed in this study, and implemented in the open source software, OpenSees. The proposed model is based on a pre-defined envelope or monotonic model and does not require updating of modeling parameters during each cycle. The model is validated using experimental data. New rules are developed for the cyclic model to capture the effects of cracking and change in stiffness and strength during the loading and unloading cycles. Comparison of the calculated and measured shear displacements indicates that the cyclic shear response can be captured by the proposed model.

Prediction of Lateral Load-Displacement Curve of Reinforced Concrete Walls with Openings under Shear Failure

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A versatile numerical model for the nonlinear analysis of squat-to-tall reinforced-concrete shear walls

Reinforced concrete (RC) walls are extensively used to resist lateral forces in tall buildings as well as in the majority of medium to low-rise structures designed for protective purposes. In the framework of seismic performance-based design, where an adequate modeling of the lateral load versus lateral displacement relationship and a full understanding of the damage evolution are required, numerical models represent an effective tool to conduct nonlinear response analyses of such systems. For practical applications and for performing extensive nonlinear analyses, it would be desirable to have a robust yet simple numerical model that is capable of capturing the global and local characteristics of the response for different levels of damage. To this end, this paper presents a finite element-based model implemented in OpenSees [1] capable of simulating the in-plane nonlinear static and dynamic response of RC walls across a broad range of aspect ratios. The proposed model includes (i) the element technology, in which the state-of-the-art isoparametric elements are coupled with layered sections, and (ii) a novel plane-stress plastic-damage concrete material. A simple simulation-based method for determining the concrete material parameters is proposed. Model validation is conducted through a comprehensive comparison against experimental tests collected from the literature. Results show that the proposed numerical tool can be reliably used to simulate the nonlinear global and local response of RC walls spanning a broad range of aspect ratios (from 0.4 to 2.3). Moreover, model hysteresis damping is analytically analyzed to provide modelers with insight into the equivalent damping to employ when nonlinear and equivalent linear dynamic analyses are performed with the proposed model. Finally, an extensive parametric study comprising a total of 12,288 nonlinear simulations is developed to investigate the sensitivity of the numerically predicted response to changes in the concrete model parameters and gain insight into the factors that most affect the walls peak shear and dissipated energy.

Experimental study of laser-welded stainless steel angle columns

Substantial research has been conducted in the last years into the structural responses of cold-formed and hot-rolled stainless steel equal-leg angle columns, whereas there is no experimental data on laser-welded stainless steel angle columns despite these sections being increasingly used in the modern construction industry. To fill this gap and provide benchmarks for design, a comprehensive experimental investigation into the structural strength and stability of laser-welded austenitic stainless steel equal-leg angle columns under pure axial compression was performed and described in this paper. A series of laboratory tests, performing on two test groups of specimens with nominal dimensions of 60 ×60× 6 mm and 100 ×100× 10 mm and different lengths, involved 6 stub column tests and 20 global buckling tests together with measurements on material properties, initial geometric imperfections and residual stresses. The experimental observations reveal that the column ultimate capacity and prevalent failure mode – major-axis flexural–torsional buckling and minor-axis flexural buckling – are highly dependent on the column slenderness and initial imperfections. The full load-lateral displacement, load-torsional rotation and load-axial strain responses of the specimens were fully reported and discussed. The results were employed to evaluate the accuracy of the current European and North American stainless steel design standards. The evaluation results revealed that the codified design procedures yield conservative resistance predictions of laser-welded stainless steel equal-leg angle columns, showing a prospective for their modification and improvement by providing more optimized and realistic results in design considering the actual residual stress distributions, material nonlinearity and strain hardening.

Numerical study of concrete-filled aluminium alloy tubular columns under eccentric compression

Concrete-filled aluminium tubular (CFAT) columns have numerous benefits, such as aesthetic appearance, less self-weight and good corrosion resistance, over conventional concrete-filled tubular columns. A limited body of research exists for CFAT columns, and the research on the behaviour of CFAT columns under eccentric loading is rather rare. Therefore, the present study aims at investigating the eccentric compressive response of CFAT columns by means of numerical analysis. The numerical models were developed considering nonlinear behaviour of the materials. The models were validated against experimental data obtained from concentric compression tests of CFAT columns. The columns used in the experiments were 6082-T6 heat-treated aluminium alloy square tubes filled with 30 MPa cube strength concrete. The validated models were used to study the influence of different loading eccentricities on the behaviour of CFAT columns. The results are discussed in terms of ultimate strengths and load-lateral displacement responses. A comparison is drawn between the column capacities obtained from the numerical analysis and calculated by European standards. It is found that the design formulae provided in Eurocode are conservative for the eccentrically loaded CFAT columns.

Seismic behaviour of novel concrete-filled composite plate shear walls with boundary columns

Concrete-filled composite plate shear walls (CCPSW) with novel enhanced C-channels (CCPSW-ECs) were developed as lateral-shear resisting structural components in high-rise buildings and nuclear facilities. This paper studied seismic performances of CCPSW-ECs through eight cyclic tests. The key influencing parameters on seismic behaviours of CCPSW-ECs were studied in the testing program, i.e., spacing of ECs (S), axial force ratio (nd), thickness of steel tube (tb), width of boundary CFST (Wb), with/without additional strengthening steel tube in boundary column, and with/without boundary CFST column. The CCPSW-ECs failed in flexure with characteristics of yielding and local buckling of faceplates in the CCPSW and steel tube of boundary CFST column, and crushing of concrete core. Introducing strengthening steel tube, using boundary CFST column and enlarging the tb of boundary CFST column acted effectively on improving seismic resistances of CCPSW-ECs. Varying S and nd values exhibited marginal influences on seismic resistances of CCPSW-ECs. This paper developed theoretical hysteretic model to describe skeleton and cyclic load versus lateral displacement behaviours of CCPSW-ECs. Validations against eight test results showed that the developed theoretical model predicted well skeleton/hysteretic load-lateral displacement behaviours of CCPSW-ECs.

Seismic behaviour of masonry infilled hinged steel frames with openings: experimental and numerical studies

This study describes an experimental and numerical investigation on the seismic behaviour of masonry infilled hinged steel frames with openings. Experimental tests of six half-scaled, single-storey and single-bay specimens including one bare hinged steel frame, one solid infilled hinged steel frame, and four masonry infilled hinged steel frames with different opening sizes were carried out under lateral cyclic loading. The cracking patterns, failure modes, hysteretic behaviour, characteristic loads and displacements, stiffness degradation and equivalent viscous damping ratios of these specimens were compared. Furthermore, detailed three-dimensional finite element (FE) models of test specimens were developed in the commercially available FE code ABAQUS, and a series of nonlinear pushover analyses were performed. In particular, the lateral load–displacement relationships of test specimens were numerically simulated and validated against the experimental results. In addition, the mechanical behaviour of infilled walls under lateral loading was investigated.

L-shaped concrete-filled steel hollow-section columns under diagonal cyclic loading

L-shaped concrete-filled steel hollow-section (CFSHS) columns have the potential to be widely used as corner columns, and have the advantage of creating larger usable areas in buildings. However, few experimental tests of this kind of column under diagonal cyclic loading have been reported. Tests on eight L-shaped CFSHS columns with equal legs were conducted to study their hysteretic behaviour; the test variables were: loading angle, concrete compressive strength, axial load level and presence or absence of stiffeners. The failure process and modes, stiffness degradation, ductility and energy dissipation were observed, and lateral load–displacement hysteretic curves and envelope curves were plotted. The results show that L-shaped CFSHS columns have generally good hysteretic behaviour and that the displacement ductility coefficients are in excess of 3 in most cases. Columns with a loading angle of 45° have >10% decrease in ultimate strength but a slightly higher ductility than columns with a loading angle of 0°. The ultimate strength, ductility and energy dissipation of columns all decrease with increasing axial load levels. Discontinuously welded stiffeners can improve the ultimate strength and ductility, but the amplitude is limited. Finally, a finite-element model was developed; the predicted results agree well with the test results.

Residual compressive load-carrying capacity of cross-laminated timber walls after exposed to one-side fire

Cross-laminated timber (CLT) panels are broadly utilized as structural members in modern timber structures. Variation in the residual resistance of CLT walls after fire exposure may lead to disruption of vertical force transmission and, in turn, structural collapse. To investigate the residual compressive load-carrying capacity of CLT walls after exposed to one-side fire, a series of tests were conducted on 3-ply and 5-ply members: axial compression tests, fire tests, and residual compressive load-carrying capacity tests. Combining the initial geometric defects obtained from the test results and the effect of shear deformation, theoretical formulae describing the compressive load-carrying capacity were deduced. Further considering the different mechanical properties over the residual cross-section model after fire, and the relative position between Region A and CLT orthogonal configuration, the calculation method of the residual compressive load-carrying capacity after fire were derived. The results of the residual compressive load-carrying capacity tests showed that the failure mode of the CLT walls after one-side fire was the eccentric compression, and the nonlinear segments of the load-axial and load-lateral displacement curves after fire accounted for larger proportion than those of axial compression tests. For the same total section thickness, the reduction in residual capacity of the 5-ply walls after fire was less than that of the 3-ply walls. The calculation results of the eccentric compression formulae considering shear deformation and initial geometric defect showed good agreement with the test values of axial compression tests. The residual compressive load-carrying capacity after one-side fire was predicted appropriately, which could be used as reference for assessing the residual load-carrying behavior of CLT elements after fire.

Cyclic behaviour of precast reinforced concrete sandwich slender walls

Experimental investigation on the performance of full scale precast RC sandwich slender walls under reversed cyclic loading is reported. Eight full scale precast 3D sandwich slender walls, with two different aspect ratios of 3.0 and 2.63, under in-plane lateral loading were tested. Four of them were designed with end stiffners, while the remaining were without stiffners. In each of four stiffened and four unstiffened walls, only two were provided with additional longitudinal reinforcement, consisting of 12 mm diameter HYSD steel rebars at 300 mm c/c spacing along on two vertical faces. All the sandwich walls were subjected to constant axial load in addition to the lateral incremental monotonic and cyclic loading using displacement control system. The performance of precast sandwich slender walls using lateral load vs. lateral displacement, pattern of cracking, displacement ductility, stiffness degradation and energy dissipation has been evaluated. The experimental results have been validated with the predicted lateral strength predicted by various codes of practice. The additional longitudinal reinforcement and end stiffeners significantly improved the lateral strength, cracking resistance, stiffness, ductility, and energy dissipation of the precast sandwich slender walls under lateral cyclic loading. The precast sandwich slender walls designed with additional longitudinal reinforcement and end stiffeners exhibited marginal improvement in the stiffness under lateral loading. The energy dissipation in the precast sandwich walls decreases in subsequent cycles of lateral displacements. The seismic base shear capacity of the precast sandwich slender walls seems to be better and comparable with the conventional RC walls.

Sustainable lateral strengthening of traditional adobe walls using natural reinforcements

In an attempt to couple sustainability with seismic resistance in adobe constructions, this study endeavors to improve the in-plane lateral performance of adobe walls using natural reinforcing materials. For this purpose, 10 adobe wall panels, each 1000 mm long, 900 mm high and 200 mm thick, were constructed and tested under the combined action of a constant vertical pre-compression stress of 0.3 MPa and lateral displacement reversals of increasing amplitude. Out of these, two specimens were used as control specimens: one wall panel tested without any strengthening and one after being plastered with straw-clay mortar. The remainder were strengthened with either externally-bonded (EB) mesh or near-surface-mounted (NSM) reinforcement and finally finished with a plaster of straw-clay mortar. The experimental intent was to use locally available, sustainable reinforcing materials such as palm fibers and reeds. Nonetheless, a wall panel was also strengthened with a special type of plastic mesh for comparison purposes. The results were described in terms of lateral load–displacement hysteretic behavior, ultimate strength, displacement capacity, ductility factor, energy dissipation, and equivalent viscous damping. The experimental findings revealed that the structural responses of the adobe walls could be significantly improved using natural reinforcement materials. In addition, the externally-bonded (EB) mesh of palm fibers was found to outperform the plastic one of similar grid dimensions. Finally, while both EB meshes of dense grid dimensions and NSM diagonal reeds could significantly improve the in-plane lateral performance of adobe walls, the former was found more effective in increasing energy dissipation capacity and equivalent damping ratio.