Ultimate Lateral Strength Research Articles

A Study on the Lateral Ultimate Strength and Collapse Modes of Doubly Curved Stiffened Plates

Bows and stems are often subjected to wave slamming loads. Stiffened plates with curvatures in both longitudinal and transversal directions are the basic members of these structures. As a result, it is important to investigate the lateral ultimate strength of the doubly curved stiffened plates. In this study, the non-linear finite element method (NFEM) is selected to investigate the collapse modes and lateral ultimate strengths of the doubly curved stiffened plates. Additionally, the influences of curvature and geometrical properties on the collapse modes and ultimate strengths of doubly curved stiffened plates are investigated. In the NFEM analysis, a series of numerical simulations, covering different aspect ratios, curvatures, and structural scantlings are performed. Different collapse modes of doubly curved stiffened plates under lateral loading cases are observed. The relationships between the collapse modes and the geometrical properties are then discussed based on the numerical results. Moreover, the results also show that larger curvatures along the stiffeners and stronger stiffeners contribute more to the lateral ultimate strengths. Subsequently, an empirical formula is derived and verified for predicting the lateral ultimate strength of the doubly curved stiffened plates. The results of the empirical formula match well with numerical calculations.

Investigating the seismic performance of MRF-CBF dual systems under the effects of staged construction

In steel structures with moment-resisting frame-concentrically braced frame dual systems, as the moment-resisting frame can individually withstand gravity and seismic loads during construction, the braces can be installed on a story-by-story basis simultaneous with the installation of the moment frame or after its complete construction. This issue cannot be investigated and studied using ordinary analysis, where it is assumed that the entire structure is built at once, and then all the involved loads are applied to the completed structure. Accordingly, this research investigated the effects of staged construction in the mentioned dual systems with V, inverted-V (Chevron), and split-X braces. In this regard, three-dimensional models with 5, 10, 15, 20, and 25 stories incorporating these systems were generated and subjected to pushover analysis under cyclic loading protocols. From the results, it was concluded that staged construction could lead to maximum increases of 19.6% in the axial forces in internal columns due to dead load, 9.3% in the displacement corresponding to the first plastic hinge formation, 13.3% in the base shear corresponding to the first plastic hinge formation, 22.9% in the ultimate lateral strength, and 4.6% in the effective lateral stiffness. Also, staged construction was not found to significantly affect the axial forces in corner and braced-bay columns due to dead load and the energy dissipation under cyclic loading protocols.

Experimental investigation of partially confined concrete-filled steel tubular square columns under lateral cyclic loading

This paper presents an experimental investigation on partially confined concrete-filled steel tubular (PCCFST) square columns (i.e., short inner concrete core confinement near the support), using circular hollow section (CHS) configuration as partial inner confinement, under combined axial and cyclic lateral loadings. Hysteretic behavior of load, ultimate lateral strength, energy dissipation capacity, and ductility of the PCCFST columns were studied as a function of (a) the ratio of the height of the inner tube to the diameter of the outer tube (0–2.5) and (b) diameter/width ratio of inner tube to outer tube (0.44, 0.53). Based on the investigation, it has been seen that the height and diameter of the inner CHS have an evident influence on the cyclic performance of the column. Ultimate lateral strength, energy dissipation capacity, and ductility were enhanced by ∼15.3%, 11.4%, and 9.6%, respectively, up to a height of 1.5D of inner CHS. Enhancement of the cyclic performance of PCCFST column with the height of inner CHS beyond 1.5D is not very significant. Based on the limited experimental results herein and code provisions (Eurocode 4), a design rule has been proposed to predict the ultimate lateral strength of the PCCFST columns.

Screw lateral restraint behaviour of timber and polymeric based railway sleepers

Broken spikes/screws were reported to fail in bending at the sleeper hole due to repeated lateral force and have become a major challenge for hardwood timber sleepers. The emergence of polymeric based composite railway sleepers further highlighted this problem as they are perceived to have limited screw lateral restraint. It is thus significant to evaluate the lateral restraint behaviour of timber and the timber replacement composite sleepers. This study investigated the lateral strength of timber, synthetic composite and Ultra High Molecular Weight Polyethylene plastic sleepers at the standard required displacement of 5.1 mm as suggested by the American Railway Engineering and Maintenance-of-way Association and up to failure. The results showed screw yielding and sleeper material hardening even before 5.1 mm displacement while timber and synthetic composites exhibited ultimate lateral strength almost half of plastics’ performance due to the relatively weak shear capacity in the fibre direction. The grain/fibre shear-out failure was noticed in the orthotropic sleeper materials (timber and synthetic composites) while the isotropic material (plastic) mainly exhibited bearing failure. Based on the isotropic hardening rule and Hill’s criterion, the developed finite element models predicted very well the screw lateral deformation and strength of timber and composite sleepers.

Semi-supported Steel Plate Shear Wall with Oblique Sides

This paper presents a new configuration for semi-supported steel plate shear walls to increase their efficiency. For this purpose, the infill steel plate is proposed to be a trapezoidal shape instead of a rectangular one. To find the most efficient inclination angle of lateral sides, a numerical parametric study was conducted. Five different values of inclination angle including 60, 75, 90, 105, and 120 degrees were considered. Furthermore, two thicknesses of 1.75 and 2.00 mm were considered for the steel plate. The area of the steel plate was the same for all the models. The models were analyzed using finite element software ABAQUS. Both geometric and material nonlinearity have been considered. To validate the finite element modeling, the available experimental results were used. According to the results, comparing to the wall with rectangular plate, the inclination angle of 60° increases the ultimate lateral strength and stiffness of the 1.75 mm-thick walls by 46% and 66%, respectively. Furthermore, a simple approximate model is presented to calculate the load-deformation response of the proposed wall using SAP 2000 program. Despite the simplicity of the method, the results were in good agreement with the results of ABAQUS.

Parametric nonlinear static analysis of a RC structure with TLCW exposed to bidirectional earthquake load by using different modelling methodologies

The seismic assessment of Reinforced Concrete (RC) buildings with Two Leaf Cavity Wall (TLCW) masonry infills requires reliable and computationally efficient numeric models. The current study has two main goals. First, to understand the contribution of TLCWs to the nonlinear response of RC buildings subjected to dynamic excitations. Second, to investigate the efficiency and accuracy of continuum-based Finite Element Modelling (FEM) approaches and simplified, structural Discrete Macro Element Modelling (DMEM) approaches in predicting the ultimate behavior of RC buildings infilled with TCLWs by performing pushover analyses. A half-scaled two-bay, two-storey RC building prototype infilled with TLCWs, experimentally tested on a shake table and already numerically investigated in the literature by FEM approaches, is considered with these aims. The responses of the FEM and DMEM models are compared to experimental observations in terms of pushover capacity curves and damage patterns. The analyses confirm the ability of the models to effectively predict the lateral deformability and lateral strength of the prototype with a satisfactory level of accuracy. However, some differences are observed in terms of the building's ultimate lateral strength, attributed to the effects of the boundary conditions at the base of the table, not explicitly described by the numerical models. The emphasis is given to the boundary conditions reached during the excitation of the scaled structural system via shaking table. Finally, in the last part of the paper, parametric analyses are performed on the DMEM model to evaluate the main material parameters governing the response of the building effected by the boundary conditions.

Experimental and analytical investigation of seismic behavior of centercore-retrofitted masonry walls

There are a significant number of historic masonry buildings and monuments in seismic areas all over the world that need to be retrofitted. Conventional methods of seismic rehabilitation conflict with the appearance of the masonry element and cannot be employed in the case of monumental buildings where the façade and finishing are decorative or where the exposed masonry defines the character of the structure. Centercore strengthening method has been developed in recent decades and is used in various projects of seismic rehabilitation. However, due to the lack of sufficient experimental and numerical investigation, there is no analytical model to predict the behavior of masonry components retrofitted using this technique. In this research, the material properties of conventional brick masonry used for the construction of Iranian historic buildings and monuments were obtained through base material tests. Afterward, two masonry walls were tested under reversed cyclic in-plane loading. The results showed that centercore method improved the cyclic in-plane behavior of the specimens including ultimate lateral strength and energy dissipation. Moreover, based on flexure theory an analytical model is proposed for prediction of ultimate lateral capacity of masonry walls and piers strengthened by centercore technique, associated with rocking and toe-crushing mechanisms. In addition, regarding dowel action of reinforcing bars and using “Beams on elastic foundation analogy”, a simple formula is proposed to predict the dowel action capacity of centercore rebar and hence, the diagonal crack strength of the retrofitted wall. Comparing the values calculated by the proposed models with available experimental data, showed that the proposed models accurately predicted the ultimate lateral capacity of the specimens.

EFFECTS OF INFILL WALLS ON BUILDING BEHAVIOUR UNDER SEISMIC LOADS

In the design of Reinforced Concrete (RC) building, infill walls are normally assumed as non-structural elements and they are accepted as vertical uniform loads on beams. Therefore, the RC buildings are designed as bare frame structures. However, in reality, infill walls are present in RC buildings, and the seismic performance of the buildings will be different with and without infill walls. In this study, 5 storey RC buildings with 2 bays and 5 bays in X-direction and Y-direction respectively are considered. The infill walls were replaced as equivalent diagonal struts and the non-linear static pushover analysis was performed to evaluate the effects of infill walls on the overall performance of the structures. The lateral strength capacity and performance point of the building were determined for the conventional (bare frame) method and with the presence of infill walls. The study reveals that the effects of infill walls under seismic loads in significant until elastic region in which the initial stiffness and strength of the structures increases, while lateral deformation capacity decreases. It is also observed that there are no significant changes in terms of ultimate lateral strength and roof displacement of the building as compared within presence of infill walls and bare frame.

Seismic Performance of Two-story RC Frame Retrofitted Using External Steel Frame Equipped with Length-adjustment Device by Pseudodynamic Test

ABSTRACT Seismic retrofitting of exiting building structures is a technical and social issue aimed as earthquake risk mitigation. In this study, a new technique for seismic retrofitting via the attachment of an external steel frame with length-adjustment control box (ESFLC) was developed to strengthen medium-to-low-rise reinforced concrete (RC) buildings. The developed method, categorized as a strength design approach, can be used to perform seismic strengthening construction while residents continue to live within the building, exhibiting excellent constructability because a control box is applied as a length-adjustment device to cope with errors in the field associated with assembly works between the existing structure and reinforcing frame. Two full-size two-story RC frame specimens were designed based on an existing Korean RC building without seismic details; one control specimen and one specimen strengthened with the ESFLC system were used. Pseudodynamic tests were carried out to verify the effects of seismic retrofitting in terms of the maximum response strength, response displacement, and degree of earthquake damage compared with a control RC frame. Nonlinear dynamic analysis was also conducted based on the material properties of the test specimens, including mathematical models that represent the nonlinear hysteresis of the used structural members, to compare the results of the pseudodynamic tests. Test results revealed that the proposed ESFLC strengthening method, externally attached to the existing RC frame, effectively increased the lateral ultimate strength, resulting in reduced response displacement of RC structures under large-scale earthquake conditions. The nonlinear dynamic analysis and test results were in reasonable agreement.

Investigating the seismic behaviour of high-performance steel plate shear walls

Steel plate shear wall (SPSWs) have good ductility, high strength and stiffness, and considerable energy absorption capability. These advantages have been confirmed in experimental and numerical studies. However, despite these advantages, the need for huge columns surrounding the infill plates is the main limitation of SPSWs. Although the high-performance steel plate shear wall (HPSPSW) has solved this shortcoming, there are still some unknowns about this high-performance system. The HPSPSW system is expected to be more economical than other resisting systems due to ease of fabrication, the elimination of complete joint penetration field welds, the elimination of stress transfer from infill plates to main columns, the higher modification factor and no need for huge main columns. A comparison of analysis results of HPSPSW and SPSW systems revealed that the HPSPSW has desirable stiffness, ductility and energy absorption when its length to height ratio is greater than 1.5. In addition, the HPSPSW system had an ultimate lateral strength only 2–5% lower than that of the SPSW. Modification factors were calculated and average values of 6.67 and 8.64 were obtained for the SPSW and HPSPSW systems, respectively. Therefore, a modification factor of 8.5 is suggested for the HPSPSW.

Pseudodynamic Testing of Buildings Retrofitted with External Steel Reinforced Concrete Frames to Increase Lateral Strength for Earthquake Damage Prevention

In this study, a new technique for seismic retrofitting via the attachment of an “external steel reinforced concrete frame” (ESRCF) system was developed to strengthen medium-to-low-rise reinforced concrete (RC) buildings. Two methods (bolting and welding) were developed to connect existing RC frames and external strengthening elements; these methods are technically and practically suited to various construction conditions. The retrofitting method developed in this study can be used to perform seismic strengthening construction, while residents continue to live within the building. The method is categorized as a “strength design approach” implemented via retrofitting, allowing the lateral ultimate load capacity of RC buildings, whose failure mode is shear, to be increased easily. Test specimens were designed based on an existing RC building in Korea lacking seismic data and then strengthened using the ESRCF system. Pseudodynamic and cyclic loading tests were conducted to verify the effects of seismic retrofitting. In total, four RC frame specimens were prepared: one nonstrengthened control specimen for the cyclic loading test, one nonstrengthened control specimen, one specimen strengthened with a welded ESRCF system, and one specimen strengthened with a bolted ESRCF system for the pseudodynamic test. The earthquake response behavior with use of the proposed method, in terms of the maximum response strength, response displacement, and degree of earthquake damage, is compared with a control RC frame. The test results indicated that both the bolting and welding methods used for connecting the existing RC frame to the ESRCF effectively increased the lateral ultimate strength, resulting in reduced response displacement of building structures under large-scale earthquake conditions.

Pseudodynamic testing of a full-size two-story reinforced concrete frame retrofitted with an H-section steel frame installed using a length-adjustment control box

In this study, to overcome the construction drawbacks of conventional seismic retrofitting techniques, we proposed a new H-section steel frame (HSF) system for seismic strengthening of existing medium-to-low-rise reinforced concrete (RC) buildings. This HSF strengthening method exhibits excellent constructability because a control box is applied as a length adjustment device to cope with errors in the field associated with assembly works between the existing structure and reinforcing frame. The method represents a strength design approach implemented via retrofitting, to easily increase the ultimate lateral load capacity of RC buildings lacking seismic data, which exhibit shear failure. Two full-size two-story RC frame specimens were designed based on an existing RC building in Korea lacking seismic data, and then strengthened using the HSF system; thus, one control specimen and one specimen strengthened with the HSF system were used. Pseudodynamic tests were conducted to verify the effects of seismic retrofitting, and the earthquake response behavior with use of the proposed method, in terms of the maximum response strength, response displacement, and degree of earthquake damage compared with a control RC frame. Nonlinear dynamic analysis was performed based on the material properties of the test specimens, including a mathematical nonlinear hysteresis model to compare the results of the pseudodynamic tests. Test results revealed that the proposed HSF strengthening method, internally applied to the RC frame, effectively increased the lateral ultimate strength, resulting in reduced response displacement of RC structures under large-scale earthquake conditions. The nonlinear dynamic analysis and test results were in good agreement.

Experimental behavior of T-shaped concrete-filled steel tubular columns under diagonal cyclic loading

T-shaped concrete-filled steel tubular (CFST) columns have the advantage of avoiding protrusion from walls and can be used as edge columns. The practical structures may be subjected to the earthquake action from different directions, but little attention has been paid to the behavior of T-shaped CFST columns under diagonal cyclic loading. A total of 14 T-shaped CFST columns were tested under constant axial load and lateral cyclic loading. The main variables explored in the test were loading angle, axial load level, concrete compressive strength and section form. The failure mode, lateral load-lateral displacement hysteretic curves, envelope curves, stiffness degradation, ductility, cumulative energy dissipation, deformation and bending moment-curvature curves were investigated. The results show that the hysteretic curves are generally plump and the displacement ductility coefficients are over 3 for the specimens with the axial load levels of less than 0.5. The specimens at 45° and 90° have close envelope curves, while the specimens at 0° exhibit slightly lower lateral ultimate strength and better ductility. The existing codes such as Eurocode 4, AISC 360–10 and DBJ/T 13-51-2010 give obviously higher predictions of initial section flexural stiffness for stiffened specimens without an axial load and conservative predictions for most multi-cell specimens. Furthermore, the existing codes overestimate the serviceability-level section flexural stiffness for most specimens.

Investigating a Combinatorial Lateral Resisting System for Tall Buildings

In this paper, the effect of a combinatorial lateral resisting system, composed of special truss moment frame (STMF) and outriggers, on the behavior of tall buildings is investigated. Outriggers in conjunction with STMFs form an effective system with a great stiffness as well as strength. The STMFs are efficient in controlling the lateral shear displacement, and the outrigger has a high bending stiffness. Therefore, the combination of these two systems presents an excellent system to reduce both the shear and bending displacements. In addition, damage is confined in the expected elements not carrying out gravity loads. Linear and nonlinear analyses were performed for 10, 20, and 40 stories with different systems in order to estimate the efficiency of the presented combined system. The results indicated that the proposed system has a much better performance than special moment frame system in both linear and nonlinear regimes. According to the results, the combined system reduced the drift ratios as well as increasing ultimate lateral strength. In addition, the energy absorption of the proposed system is increased more than 48% that is a valuable achievement.

Seismic retrofit of masonry wall infilled RC frames through external post-tensioning

In this study, an external post-tensioning technique was employed to enhance the seismic performance of infilled RC frames through preventing premature failure of infill walls and increase in their engagement with RC frames. Totally, six 1/3-scale single-story single-bay RC frames were constructed and tested. The frames were divided into two groups based on their aspect ratios. Each group consisted of a bare frame, an infilled frame and a retrofitted infilled frame. All specimens were subjected to a similar quasi-static cyclic loading and their responses were measured through load cells, strain gauges and linear variable differential transformers. Results indicated that the retrofitted infilled frames had higher initial stiffness, ultimate lateral strength and ductility ratio when compared with the bare and un-retrofitted infilled frames. The retrofitted infilled frames also showed a prolonged failure mode and a lower stiffness degradation rate compared to other frames. It was also observed that, compared to other frames, the retrofitted frames had smaller strain values at their critical zones.

共用廊下増築を伴う既存壁式プレキャスト鉄筋コンクリート構造集合住宅建物の耐震性能評価

Significant number of wall-type precast reinforced concrete (WPC) residential buildings exist in Japan, constructed during the 1960-70s.They are assembled using prefabricated concrete panels for the slabs and walls and of high quality in terms of the structural conditions. In order to utilize them, seismic behavior of the existing buildings extended with new corridor and elevator structures were analytically evaluated. Static pushover analyses were conducted considering inelastic behavior of members and connections between the existing precast concrete wall panels. The ultimate lateral strength of the extended buildings were nearly equivalent to that of the existing buildings.

多雪地域に建つ学校体育館の妻壁に起因する屋根型単層ラチスシェルの水平地震時鉛直応答の分析と保有耐力評価

The study deals with school gymnasium structures composed of EP roof type lattice shells, gable walls with a high rigidity and with truss arch frames. The collapse mechanisms of the structure are taken to be a horizontal structural collapse such as the member buckling collapse of the lattice shell and a vertical structural collapse such as the tensile member collapse of the gable wall. The purpose of this study is to investigate the static and the dynamic collapse by means of the both elasto-plastic analyses considering a geometric nonlinearity. The estimation method is also proposed to calculate practically the base-shear strength coefficient and the applied seismic lateral and vertical load distributions on the lattice shells, the gable walls and the truss arch frames. The study is practically useful to determine the collapse mechanism and calculate the ultimate lateral strength on the earthquake-proof design for the damage and safety limit earthquakes.

Experimental Study on the Seismic Performance of Recycled Concrete Brick Walls Embedded with Vertical Reinforcement.

Recycled concrete brick (RCB) is manufactured by recycled aggregate processed from discarded concrete blocks arising from the demolishing of existing buildings. This paper presents research on the seismic performance of RCB masonry walls to assess the applicability of RCB for use in rural low-rise constructions. The seismic performance of a masonry wall is closely related to the vertical load applied to the wall. Thus, the compressive performance of RCB masonry was investigated firstly by constructing and testing eighteen RCB masonry compressive specimens with different mortar strengths. The load-bearing capacity, deformation and failure characteristic were analyzed, as well. Then, a quasi-static test was carried out to study the seismic behavior of RCB walls by eight RCB masonry walls subjected to an axial compressive load and a reversed cyclic lateral load. Based on the test results, equations for predicting the compressive strength of RCB masonry and the lateral ultimate strength of an RCB masonry wall were proposed. Experimental values were found to be in good agreement with the predicted values. Meanwhile, finite element analysis (FEA) and parametric analysis of the RCB walls were carried out using ABAQUS software. The elastic-plastic deformation characteristics and the lateral load-displacement relations were studied.

Strength and Creep Characteristics of Reclaimed Asphalt Pavement–Sand Blend Backfill in Mechanically Stabilized Earth Walls

Using reclaimed asphalt pavement (RAP) as a backfill for mechanically stabilized earth (MSE) walls provides both environmental and economic benefits by allowing in situ recycling for road widening projects. RAP, a well-drained granular material, has lower reinforcing strip pullout strength than A-3 sand and creeps under constant load. The objective of this research was to determine whether blending RAP with A-3 sand would improve RAP's performance in MSE applications. Laboratory specimens of 100% RAP, 100% A-3 sand, and 50% RAP–50% sand blends were compacted by the modified Proctor method and tested for vertical creep with one-dimensional oedometer compression tests at three stress levels to simulate different depths behind an MSE wall. Large-scale test pit testing was performed to determine reinforcing strip ultimate lateral pullout strength; pullout creep at 25%, 50%, and 75% of ultimate pullout; and vertical creep at the three overburden stress levels used in laboratory testing. RAP–sand blends had higher density, friction factors, and pullout strength and developed ultimate pullout strength at lower displacements than either 100% sand or 100% RAP. The RAP–sand blends exhibited more horizontal and vertical creep than 100% sand but significantly less creep than 100% RAP.

Plastic Analysis on the Semi-Rigid Steel Frame-Composite Steel Plate Shear Wall Structure

The semi-rigid steel frame-composite steel plate shear wall structure (SCSW) effectively improves the lateral stiffness of shear wall, making it possible to use the semi-rigid joint. In order to study the plastic failure mechanism of SCSW, a plastic model is established, in which the effects of the rotations of semi-rigid joints and yield deformations of infill steel walls on the energy consumption are considered. Based on that, a design method for the lateral ultimate strength is put forward and a nonlinear FEM model is setup using ANSYS. Through the comparison between plastic analysis results with the finite element results, it is shown that the plastic analysis method is feasible and has a safe redundancy.