Lateral Load-resisting System Research Articles

Experimental and numerical study on steel-concrete composite shear wall using light-weight concrete

In the present study, the behaviour of concrete stiffened steel plate shear wall (CSPSW) using precast light weight-concrete panels is experimentally and numerically investigated. Three one-bay one-story CSPSW specimens were designed, fabricated, and tested. The steel materials and dimensions of all specimens were the same; however, their precast concrete panels were different. One of the specimens had a precast normal-weight concrete panel on one side of the infill steel plate; on the other hand, another specimen had a light-weight one. The third specimen had two light-weight concrete panels on both sides of the steel plate. The quasi-static cyclic test results indicate that CSPSW with a light-weight concrete panel is a reliable lateral load-resisting system for steel structures. In addition, the shear capacity of specimen with light-weight concrete was approximately similar to specimen with normal-weight one. Therefore, it can be inferred the new system is able to reduce the seismic mass and improve the behaviour of steel structures. In this study, the light-weight concrete panel was 36% lighter than normal-weight panel. Based on the test data, specimens could tolerate high inter-story drift between 5.04% and 6.24% until the shear capacity decline in 80% of the maximum shear load recoded in the test. It should be mentioned that the infill steel plate of CSPSW undergoes entirely inelastic deformation and dissipates significant seismic energy through large lateral displacement.

Technical Note: Analytical Evaluation of the Vulnerability of Framed Tall Buildings with Steel Plate Shear Wall to Progressive Collapse

In recent decades, vulnerability of tall buildings to unforeseen loads, induced by progressive collapse, has drawn researchers’ attentions. Steel plate shear walls have long been used as a lateral load-resisting system. It is composed of beam and column frame elements, to which infill plates are connected. There is a growing tendency among engineers to design tall buildings using steel plate shear walls. This paper investigates the progressive collapse-resisting capacity of the strip model of steel plate shear wall system compared with X-braced and moment frame system. The 3D models are used to assess the collapse behavior of typical 50-story building models, under sudden loss of elements from the middle and corner of the exterior frame in the story above the ground. The progressive collapse potential of model structures is evaluated by different nonlinear static and dynamic analyses using conventional analysis software. In this study, the vulnerability of candidate structures subjected to progressive collapse is also assessed by a sensitivity index regarding the sensitivity of structures to the dynamic effect induced by progressive collapse. To identify vulnerable members, the resulting actions of two nonlinear and linear static analyses are compared by the factor of redundancy related to the overall strength of the structure. Comparison of the analysis results indicated that in the steel plate shear wall system, the progressive collapse-resisting potential is more than X-braced and moment frame structure. Sensitive index of highly sensitive elements to the dynamic effect stated that in the structural models, beams are significantly more vulnerable in the moment frame than X-braced and SPSW structure. The index depicted that the vulnerability of columns in X-braced and SPSW structure is more than the moment frame structure.

Seismic response estimation of steel plate shear walls using nonlinear static methods

One of the major components for performance based seismic design is accurate estimation of critical seismic demand parameters. While nonlinear seismic analysis is the most appropriate analysis method for estimation of seismic demand parameters, this method is very time consuming and complex. Single mode pushover analysis method, N2 method and multi-mode pushover analysis method, modal pushover analysis (MPA) are two nonlinear static methods that have recently been used for seismic performance evaluation of few lateral load-resisting systems. This paper further investigates the applicability of N2 and MPA methods for estimating the seismic demands of ductile unstiffened steel plate shear walls (SPSWs). Three different unstiffened SPSWs (4-, 8-, and 15-storey) designed according to capacity design approach were analysed under artificial and real ground motions for Vancouver. A comparison of seismic response quantities such as, height-wise distribution of floor displacements, storey drifts estimated using N2 and MPA methods with more accurate nonlinear seismic analysis indicates that both N2 and MPA procedures can reasonably estimates the peak top displacements for low-rise SPSW buildings. In addition, MPA procedure provides better predictions of inter-storey drifts for taller SPSW. The MPA procedure has been extended to provide better estimate of base shear of SPSW.

Quantification of Linked Column Frame Seismic Performance Factors for Use in Seismic Design

Previous research has proposed the Linked Column Frame (LCF) as a lateral load-resisting system capable of providing rapid return to occupancy for buildings impacted by moderate earthquake events and collapse prevention in very large events. The LCF consists of flexible moment frames (MF) and linked columns (LC), which are closely spaced dual columns interconnected with bolted links. The linked columns (LC) are designed to limit seismic forces and provide energy dissipation through yielding of the links, while preventing damage to the moment frame under certain earthquake hazard levels. The proposed design procedure ensures the links of the linked column yield at a significantly lower story drift than the beams of the moment frame, enabling design of this system for two distinct performance states: rapid repair, where only link damage occurs and quick link replacement is possible; and collapse prevention, where both the linked column and moment frame may be damaged.Here, the seismic performance factors for the LCF system, including the response modification factor, R, the system over-strength factor, Ω0, and the deflection amplification factor, Cd, are established following the procedures described in FEMA P695 [2009]. These parameters are necessary for inclusion of the system in the building code. This work describes the development of archetype structures, numerical models of the LCF systems, incremental dynamic analyses, and interpretation of the results. From the results, it is recommended that R, Ω0, and Cd values of 8, 3, and 5.5 be used for seismic design of the LCF system. A height limit of 35 m (115ft) is recommended at this time as taller LCFs are not considered in this study.

On the equivalent simple models of braced steel shear panels

Through the combination of two types of seismic resisting systems including braced frames and steel shear walls, braced steel shear panel systems can be formed. This new lateral load-resisting system solves some of the defects of current special steel shear walls, such as imposing significant loads on boundary elements along with gravity load effects. Analysis and design of this new structural system underline the importance of having simple and precise finite-element models. To this aim, this paper presents two types of equivalent braced frames termed ‘overall equivalent brace’ and ‘equivalent mid-brace’. The equations of brace area, material strength and strain-hardening ratio are obtained in two states of considering both braces or regardless of compressive brace. Next, non-linear lateral displacement, yield and ultimate values of base shear of one-storey and three-storey equivalent models are compared with the results of strip models. The findings show that the proposed models can obtain acceptable results by considering both braces only with equivalent area along with material strength.

Hysteresis Behavior of Reinforced Concrete Walls

AbstractReinforced concrete walls are the primary lateral load-resisting systems in numerous multistory buildings and nuclear structures located in seismically active regions. Hence, hysteresis behavior prediction of structural walls is of utmost importance in the context of seismic analysis and design. A hysteresis model of reinforced concrete walls, capable of producing requisite structural degradation and pinching characteristics, has been proposed in this research on the basis of the Bouc-Wen-Baber-Noori model. The Livermore solver for ordinary differential equations (LSODE) and genetic algorithms have been used for solving the differential equations and identifying the analytical parameters associated with the model, respectively. A database of wall specimens tested under cyclic loading has been accumulated from literature to successfully calibrate the analytical response with the experimental results. Subsequently, the relationship between the structural features and the model parameters is resolved...

Structural System of Safe House against Tornado and Earthquakes

Every year earthquakes, tornadoes and other extreme windstorm cause fatalities or even kill people, devastate and millions of dollars worth of property. The likelihood that a tornado will strike building is a matter of probability. The study describes the analysis and design, the engineering process the new type of tornado safe room (Fig. 1) according to the FEMA guidance. It also evaluates the effects of in-fill frames and the linear response of reinforced concrete braced frames and comparison with frames with shear wall. The main conclusion drawn from this study is to elaborate that the masonry in-fills, are strongly influence the structural seismic response and contribute to the overall stiffness and can decrease drifts and displacements. Infill walls have significant role in the strength and ductility of RC framed structures and should be considered in both analysis and design globally. These walls make the structure significantly stiffer, and reduce the natural period of the structure. Locally, infill walls changed the load path, the distribution of forces between different elements of the structure, and the change the demand of forces on their adjacent elements of the bounding frame. Due to the high relative stiffness of the infill frames, they act as the main lateral load-resisting system and attract larger portions of the earthquake and tornado induced inertia forces.

Shaking table scaled model test on a high-rise building with CFT frame and composite core wall

A high-rise building named as Fortune Plaza II Office Building is 264 m high employing the composite system consisting of a concrete-filled steel tube frame and a steel plate reinforced concrete core wall in Beijing, China. The height of the building, the lateral load-resisting structural system and the high seismic intensity level of the construction site present a great challenge to structural engineers. According to the peer review committee’s recommendation, a 1/30 scaled model was tested under a series of one- and two-dimensional seismic excitations with gradually increasing acceleration amplitude. This paper, presents the process of model construction and the results of the shaking table tests. The dynamic characteristics, seismic responses and failure characteristics of the model and the prototype structure are investigated. Based on the test results, the conclusions are drawn that the prototype structure can meet the requirements of performance-based seismic design. The design of the structural system is able to ensure the life safety even when subjected to extremely strong earthquake with peak ground acceleration up to .62 g. Some corresponding measures for improving the design of this structure are also put forward.

Analytical investigation of response modification (behaviour) factor, R, for reinforced concrete frames rehabilitated by steel chevron bracing

Steel bracing of reinforced concrete (RC) frames has received noticeable attention in recent years as a retrofitting measure to increase the shear capacity of the existing RC buildings. In order to evaluate the seismic behaviour of steel-braced RC frames, some key response parameters, including the ductility and the overstrength factors, should first be determined. These two parameters are incorporated in structural design through a force reduction or a response modification factor. In this paper, the ductility and the overstrength factors as well as the response modification factor (or seismic behaviour factor) for steel chevron-braced RC frames have been evaluated by performing inelastic pushover analyses of brace-frame systems of different heights and configurations. The effects of some parameters influencing the value of behaviour factor, including the height of the frame and share of bracing system from the applied lateral load have been investigated. It is found that the latter parameter has a more localised effect on the R values and its influence does not warrant generalisation at this stage. However, the height of this type of lateral load-resisting system has a profound effect on the R factor, as it directly affects the ductility capacity of the dual system. Finally, based on the findings presented in the article, tentative R values have been proposed for steel chevron-braced moment-resisting RC frame dual systems for different ductility demands and compared with different type of bracing systems.

Seismic Response of Midrise Light Wood-Frame Buildings with Portal Frames

The seismic response of midrise light wood-frame buildings incorporating portal frames and shear walls were investigated via numerical simulation. Because portal frames and shear walls exhibit different ductility characteristics, of specific interest in this paper is the seismic force-modification factor for the combined building system. An approach to estimate the ductility-related force-modification factor, Rd, for the hybrid light wood-frame building containing two types of lateral load-resisting systems with different Rd was proposed. One-, four-, and six-story buildings with layouts that rely on shear walls only or a combination of shear walls and portal frames were designed using the Rd estimated from the proposed approach. Frequency and nonlinear time history analyses were performed on these multistory hybrid buildings using a modified macro element model to represent the lateral-resistant element in finite-element program, ABAQUS. The results show that the use of a Rd value higher than the lowest Rd factor of the two lateral load-resisting systems is justified.

비틀림 초고층 프로토타입 모델에 대한 시공단계해석의 적용

Abstract With regard to complex-shaped tall buildings whose plans and constructions have been gradually on the increase, this study was aimed to analyze their structural behaviors during construction by applications of construction sequences analyses to prototype models. For twisted tall buildings, total 18 models of with three conditions of a lateral load-resisting system, a twisting angle, and a construction method were selected. A diagrid system and a braced tube system were applied as a lateral load-resisting system. For each lateral load-resisting system, three types of plan with 0, 1, and 2twisting angles and three construction methods with construction sequences of exterior tube and interior frame were assumed. The structural performances of tall buildings under constructions were analyzed with results of lateral displacements from construction sequence analyses. Also, construction performances of the construction period and the maximum lift weight were compared. Keywords :tall building, complex-shape, construction sequence analysis, construction, twisted shapes

Repairable Seismic Moment Frames with Bolted WT Connections: Part I

A moment frame lateral load-resisting system was developed in which inelastic deformations due to seismic loading were intended to be isolated to easily replaceable WT components. Fully bolted connections were utilized to facilitate simple component installation and replacement. In Part I of this series, WT components for the moment frame system were modeled using finite element analysis. Full-scale component testing was performed to verify analytical results. Parameters taken from modeling and testing results were used to develop design provisions. In Part II of this series, an example building was designed using the provisions developed and analyzed under simulated earthquake accelerations to develop appropriate seismic performance factors. WT components designed using recommended geometric parameters resulted in desirable behavior. Recommended design equations correlated well to experimental test results. Experimental results suggested WT components designed using the recommended provisions exhibit adequate low-cycle fatigue performance and deflection capacity to be used with wide flange beams up to a nominal depth of 30 in. (762 mm). Nonlinear time-history analysis suggests seismic performance factors currently published for steel special moment frame systems are appropriate for the proposed WT moment frame system.

Repairable Seismic Moment Frames with Bolted WT Connections: Part II

A moment frame lateral load-resisting system was developed in which inelastic deformations due to seismic loading were intended to be isolated to easily replaceable WT components. Fully bolted connections were utilized to facilitate simple component installation and replacement. In Part I of this series, WT components for the moment frame system were modeled using finite element analysis. Full-scale component testing was performed to verify analytical results. Parameters taken from modeling and testing results were used to develop design provisions. In Part II of this series, an example building was designed using the provisions developed and analyzed under simulated earthquake accelerations to develop appropriate seismic performance factors. WT components designed using recommended geometric parameters resulted in desirable behavior. Recommended design equations correlated well to experimental test results. Experimental results suggested WT components designed using the recommended provisions exhibit adequate low-cycle fatigue performance and deflection capacity to be used with wide flange beams up to a nominal depth of 30 in. (762 mm). Nonlinear time-history analysis suggests seismic performance factors currently published for steel special moment frame systems are appropriate for the proposed WT moment frame system.

Cyclic behavior of SPSW and CSPSW in composite frame

Shear wall systems are one of the most commonly used lateral-load resisting systems in high-rise buildings. The composite steel plate shear wall (CSPSW) systems have strong points, such as high bearing capacity, good ductility and energy dissipation capacity, which have been increasingly used as lateral load-resisting system in steel buildings. This paper describes the experimental work related to the tests of steel plate shear wall (SPSW) system and CSPSW system. Two 1/3 scaled specimens were fabricated and tested. The tested shear wall system consisted of concrete-filled circular hollow section (CHS) steel columns, steel beams, and SPSW or CSPSW. The experimental results were summarized and discussed, which showed that both SPSW system and CSPSW system possessed good ductility and energy dissipation capacity. For SPSW system, the primary mechanism for resisting storey shear arising from lateral loads came from the post-buckling inclined tension field that forms for thin-walled steel plate. For CSPSW system, the reinforced-concrete (RC) panels attached on both sides of steel plates were able to ensure the composite action by preventing the overall buckling of steel plate. Compared with SPSW system, the bearing capacity and energy dissipation capacity of CSPSW system increased evidently.

Energy-Dissipation Mechanisms and Seismic Design Recommendation of Eccentrically Braced Steel Frames

Eccentrically braced steel frames are a lateral load-resisting system which apply high intensity area and it can provide the high elastic stiffness that met higher steel building drift requirement. This paper first provides an introduction of Forces in links and Energy dissipation mechanisms of eccentrically braced steel frames. In that Eccentrically braced steel frames will collapse after the link beams go into plastic deformation under earthquake load, A new analytical model which include shell element apply to link beams with large deformation and plastic deformation and beams element apply to other parts of structure is presented in this paper for analyzing eccentrically braced steel frames energy-dissipation behavior and collapse mechanism. Computer program is complied. After this paper applies nonlinear finite element program to analyze the behaviors of eccentrically braced steel frames under cyclic load, the seismic design recommendations of eccentrically brace are presented.

Evaluation of the Lateral Load-Resisting System of a Stadium Structure

This paper describes an evaluation of the lateral load-resisting system of an existing monolithic, cast-in-place, reinforced concrete (RC) stadium structure completed in the early 1930s. A major renovation/expansion of the stadium completed in the 1990s included modifications of some of the original exterior infill masonry wall, including removal of masonry and enlargement of existing openings. A preliminary study raised concerns about the impact of these modifications on the lateral load resistance of the stadium structure. A new study, which consisted of an evaluation of the structure’s performance using in situ lateral load testing of the structure, numerical analyses, and monitoring of the actual stadium-sway movements during football games, was undertaken in 2006 to determine the adequacy of the lateral load resisting system of the stadium. The results of this study, which are reported in this paper, demonstrate that the masonry modifications made during the renovations/expansion of the stadium did not impair the structure’s resistance to code-prescribed lateral loads and that no major structural repairs were required.

Seismic behaviour of composite shear walls with multi‐embedded steel sections. Part I: experiment

AbstractShear wall system is one of the most commonly used lateral load‐resisting systems in high‐rise buildings. The reinforced concrete (RC) walls studied herein are composite shear walls (CSW) with multi‐embedded steel sections (MSS) at wall boundaries as well as wall middles. In this paper, experimental studies of CSW with MSS are presented and discussed. Sixteen 1/3‐scale specimens with varied structural parameters were tested under static loading and the effects of the parameters on the seismic performance of CSW were studied. It is found that the practice of MSS in RC walls is a good way to improve the structural ductility. CSW with MSS has better energy dissipation capacity than that with steel sections only at boundaries. MSS did not affect the final failure mode of the CSW, but they would restrain the development of cracks and prevent the concrete from serious spalling. For MSS, more steel area configured at the end columns will result in better seismic behaviour of CSW. Copyright © 2010 John Wiley & Sons, Ltd.

In-Plane Experimental Testing of Timber-Concrete Composite Floor Diaphragms

Recent advances in multistory timber building design have led to new structural systems that allow open floor plans with large spans between frames and/or walls. Timber-concrete composite (TCC) flooring can achieve the spans required but has the potential to be flexible under diaphragm actions, which can significantly alter the seismic response of a building. In-plane experimental tests on a 3 m by 3 m one-third scale TCC floor were performed using quasi-static earthquake loading simulation. The experimental results indicate that the deformation between the floor and lateral load resisting systems (LLRS) is much greater than the in-plane deformation of the floor diaphragm. Hence, a floor system with similar aspect ratio can be modeled as a single-degree-of-freedom for future structural analyses. Different connections were considered between the floor unit and lateral restraints, which simulate the LLRS. The connection was either timber-to-timber or concrete-to-timber and incorporated screws or nails acting as dowels or inclined at 45°. Each connection type performed differently in terms of stiffness, strength, ductility capacity, and induced damage. Screws that were oriented at 45° to the connection interface were significantly stiffer than fasteners aligned orthogonal to the interface. There was little difference in the initial stiffness for the concrete-to-timber connection compared to the timber-to-timber connection. The testing indicated that a timber-to-timber interface is more desirable because of construction ease and reparability. The in-plane response of the floor system is modeled using finite elements and compared to experimental results. Design recommendations are provided for the cyclic strength of inclined wood fasteners.

Cyclic Testing and Modeling of Cold-Formed Steel Special Bolted Moment Frame Connections

A cyclic testing of nine full-scale beam-to-column moment connection subassemblies was carried out to support the development of design provisions for a lateral load-resisting system in the AISI S110: Standard for Seismic Design of Cold-Formed Steel Structural Systems—Special Bolted Moment Frames. This type of one-story framing system features C-section beams connected to hollow structural section columns by bearing-type high-strength bolts and is commonly used in industrial platform construction. The test results showed that these specimens had an interstory drift capacity significantly larger than 0.04 rad. The cyclic behavior was characterized by a linear response, a slip range, and a significant hardening response due to bearing at bolt holes. The conventional strong column-weak beam design philosophy is not appropriate for this system. The inelastic action through the bolt slip and bearing in the connection is a ductile yielding mechanism. Beams and columns should be protected to remain elastic by the capacity design principles. Based on the concept of the instantaneous center of rotation of an eccentrically loaded bolt group, a model that can properly simulate the cyclic behavior of the bolted moment connection is presented.

Progressive Collapse-Resisting Capacity of Steel Moment Frames considering Panel Zone Deformation

Panel zone deformation is known to be a major parameter affecting the nonlinear behaviour of moment resisting steel frames subjected to earthquake loads, especially in weak column-strong beam conditions. In this study, the reinforcing effect of the panel zone on the progressive collapse and the capacity of moment resisting steel frames was investigated with the aid of nonlinear dynamic analysis. Both gravity load-resisting system structures with weak panel zones and lateral load-resisting system structures with strong panel zones were studied. The analysis results show that the panel zone deformation is highly dependent on the location of removed columns. The panel zone deformation turns out to be very significant when a column adjacent to an exterior panel zone is removed. On the other hand, the panel zone effect is not significant if a column adjacent to an interior panel zone is removed. As the number of stories increases, the effect of a weak panel zone on the overall behaviour decreases regardless of the panel zone strength and the location of any column removed.