Lateral Load-resisting System Research Articles

Canadian seismic design coefficients for coupled composite plate shear wall/concrete filled (CC-PSW/CF)

Concrete-filled coupled composite plate shear walls (also known as as SpeedCore walls) are gaining acceptance for construction in seismic region throughout North America. Design provisions for this lateral load-resisting system have already been added to ASCE 7-22 and to the American Institute of Steel Construction Seismic Design Provisions. Adequacy of the seismic design parameters used for this structural purpose has been validated in the USA using the FEMA P695 methodology. An interest was expressed by the practicing engineering community to use these walls in Canada, which requires demonstration of satisfactory seismic performance within the Canadian context. As such, new analyses are needed using Canadian-specific sets of ground motions to confirm the adequacy of the seismic design parameters proposed for implementation of these composite walls in the National Building Code of Canada. This paper presents the results of these analyses, showing that the proposed seismic performance factors are appropriate for this structural system in Canada.

Numerical comparison of truss-shaped lateral load-resisting systems with conventional steel shear walls

Steel plate shear wall (SPSW) is considered to be one of the most efficient lateral load-resisting systems. However, this system has some drawbacks, including the difficulty of construction, installation challenges, and potential serviceability issues. Although many studies have been conducted to enhance the seismic performance of SPSWs, these systems have not gained widespread popularity due to their cost and time-consuming installation process. In this study, an innovative structural system called truss-shaped lateral load resisting system (TS-LLRS) is developed and proposed as an alternative to SPSWs to address these challenges and provide architectural advantages. The TS-LLRS is composed of steel elements arranged in the configuration of a 2D truss, connected to the boundary elements within a frame rather than a thin plate. First, a numerical study is performed using five finite element models. The generated models with different arrangements were analyzed and compared with SPSWs regarding structural characteristics such as stiffness, energy dissipation, ultimate strength, and stress distribution. Next, a parametric study was conducted using 64 TS-LLRS finite element models with different arrangements. Two key parameters controlling the behavior of TS-LLRSs were the angle and slenderness ratio of the truss elements. The optimum angle of the truss elements was found to be approximately 45 degrees. Finally, a case study was conducted using a 9-story building. The results demonstrated that TS-LLRS exhibited desirable behavior, which was relatively similar to SPSWs, indicating its potential as an alternative to steel plate shear walls. Additionally, a tentative value of 6.5 has been proposed for the response modification factor of TS-LLRS.

A Review paper on seismic response of various slab systems with and without lateral load resisting systems

With the ongoing modern trends of the construction industry, slab systems like flat slab and post tensioned slabs are widely used in the construction. Flat and post tensioned slab are widely favored by architects and clients for aesthetic reasons. They also do possess a huge advantage structurally over conventional slab arrangement such as Less depth of the slab is required , increasing the floor-to-floor height , longer spans are possible , no beam projections , reduced self-weight of the building and many more. But it comes with its own disadvantages as well such as Brittle punching (shear) failure. Which requires additional reinforcement along the connections of column and slab. Which increases the longitudinal steel required. Slab – column connections are the first point of yielding in higher seismic zones with buildings without lateral load resisting system (LLRS). In higher seismic zones the slabs can resist only the gravity loads and can’t resist the lateral dynamic loading and hence may require additional lateral load resisting system (LLRS) to resist lateral loads such as seismic and wind loads. Thus it becomes essential to study the seismic behavior of conventional slab , flat slab and post tensioned slab systems in high rise RCC structure with and without various LLRS ( lateral load resisting system).This study is aimed to study various literatures related to effects of lateral loads on flat and post tensioned slab system and different LLRS (lateral load resisting system) to make the structure more resistant and economical against such lateral loads considering parameters like story displacement , base shear , stiffness of the connections and time period.

A new hybrid steel–timber rocking seismic force resisting system equipped with U-shaped fuse connections

This paper introduces a new low-damage hybrid steel–timber rocking braced frame with self-centring capability and proposes a design methodology in the framework of Canadian design standards. This system consists of a gravity load-resisting timber frame and a steel concentrically braced frame acting as the lateral load-resisting system that is connected using U-shaped steel fuses. The self-centring capability is achieved by post-tensioning strands and rocking bases within the lateral load-resisting system. The system, along with its components, is first introduced. The proposed design method and system performance objectives are then presented. The seismic performance of the system and the proposed design procedure are validated through numerical analyses considering the interaction between the lateral and gravity load-resisting systems. The results of dynamic analyses confirm the enhanced seismic performance of the proposed hybrid system with almost no residual deformations after the earthquake. Moreover, the proposed design guidelines can accurately predict the system’s seismic response and demands imposed on the members.

Development and implementation of shear wall finite element in OpenSees

Shear walls are widely used as lateral load-resisting systems in high-rise building structures. The design and nonlinear analysis of shear walls under seismic loads for recoverability are complicated and challenging, which demands nonlinear computer modeling procedures. This paper presents a novel finite element named Double Vertical Beam-column with Shell Element (DVBSE) for the nonlinear analysis of complex reinforced concrete shear walls with columns. The DVBSE is implemented in the open-source finite element program OpenSees. The theoretical formulations of DVBSE are described in detail. The accuracy of the developed DVBSE is established by comparing the finite element analysis results with existing experimental data on recoverable steel-GFRP composite bar reinforced concrete shear walls. The comparative study demonstrates that the proposed DVBSE is superior to the commonly used finite element model in simulating the responses of recoverable complex shear walls under seismic loads. These research findings contribute to further advancements in the development of new shear wall elements and lay a solid foundation for the nonlinear numerical simulation of innovative shear walls.

Evaluation of vibration properties of an 18-story mass timber–concrete hybrid building by on-site vibration tests

Timber–concrete hybrid structural systems are a practical option to provide tall mass timber buildings with a lateral load-resisting system. This paper discusses the dynamic behavior of an 18-story timber–concrete hybrid building based on the vibration properties evaluated by on-site vibration tests. First, microtremor measurements and human-powered excitation tests were carried out and the obtained vibration data were analyzed using a stochastic subspace identification method to derive natural frequencies, damping ratios, and mode shapes. Then, a finite-element (FE) model was developed based on detailed structural design information, and its eigenvalues and eigenvectors were compared with the test results. The vibration test results showed various mode shapes, including in-plane deformation of the floor diaphragm composed of cross-laminated timber (CLT) panels. The damping ratios in all the modes were scattered between 1 and 3%, and no frequency dependency was observed. The modal properties of the FE model agreed well with the test results by considering the additional stiffness of non-structural components. In order to simulate the in-plane deformation of the CLT floor diaphragm, detailed modeling of the connection between each CLT floor panel and the connection between CLT floor panels and concrete cores is recommended. The findings provide practitioners with an insight into dynamic properties and FE modeling methods of tall timber–concrete hybrid buildings.

Seismic performance factors of quarter-elliptic-braced steel moment frames (QEB-MFs) using FEMA P695 methodology

One of the newest lateral load-resisting systems is quarter-elliptic-braced steel moment frames (QEB-MFs). The elliptical geometry of this bracing system not only resolves the shortcomings of conventional concentrically braced frame systems but also leads to greater energy absorption. The QEB-MF system's seismic performance factors (SPFs) are specified in this paper using the FEMA P695 approach. To this end, a three-dimensional group of 2-, 4-, 6-, and 8-story archetypes in two distinct seismic design categories (SDC Cmax and Cmin) were designed according to presumed SPFs. The adjusted collapse margin ratio (ACMR) for each archetype was calculated utilizing the results of non-linear static (pushover) analysis and incremental dynamic analysis (IDA) under far-field ground motion (FFGM) records. In order to confirm presumed SPFs, ACMRs were compared to FEMA P695's acceptable values. The results indicate that the ACMR values for the QEB-MF systems that were designed with a response modification factor of 6.5 are acceptable. In addition, the deflection amplification factor and the over-strength factor have been acquired to be equal to 6.5 and 2.5, respectively.

Seismic collapse performance of high-rise mass timber building with buckling-restrained braced frames

The present paper proposes a hybrid building system with the buckling-restrained brace and Glulam frames (BRBGF). For a highly seismic location of Vancouver, Canada, an 18-story building is designed with BRBGF as the lateral load-resisting system for the seismic hazard of NBC 2020. A nonlinear analytical model is developed and validated with the experimental data. Further, 30 pairs of ground motion records are selected to represent the complex seismicity of Southern British Columbia consisting of Shallow Crustal, Subduction Interface, and In-slab faulting mechanisms. The BRBGF system is found to achieve the target of maximum inter-story drift of 2.5% for the 2,475-year return period event. The building also passes the FEMA P695 criteria for acceptable collapse margin for seismic force modification factors of Rd=4 and Ro=1.2. The results from the study indicate the feasibility of high-rise timber buildings in highly seismic regions.

Experimental investigation of post-fire seismic behavior of reinforced high-strength concrete shear walls

Reinforced high-strength concrete shear walls (RHSCSWs) are widely used for lateral load-resisting systems in tall buildings. Due to the high possibility of explosive spalling of high-strength concrete under high temperature, the structural performance of high-strength concrete shear wall may be greatly reduced after fire, which should be paid attention to by the engineering community. In this study, the post-fire seismic performance of RHSCSWs was investigated. Twelve RHSCSW specimens were fabricated and tested under an ISO-834 standard fire. Thereafter, 10 of these specimens were subjected to an in-plane cyclic load to evaluate their post-fire seismic performance. The remaining two specimens were subjected to concentric axial loads because they were severely damaged by explosive concrete spalling in the fire. The investigated parameters of the specimens included the concrete strength, fire exposure condition (one-side or four sides), fire duration, aspect ratio, axial load ratio, surface mortar layer, and strengthening technique (i.e., whether an X-shaped steel brace was installed). Their fire and post-fire structural performances were carefully assessed. The concrete walls with a cube compressive strength of 75.8 MPa were prone to explosive spalling in fire, whereas the concrete walls with a cube compressive strength of 60.3 MPa were not. Moreover, concrete shear walls with surface mortar layers were more likely to experience explosive spalling in fire than walls without such layers. With increasing axial load ratio, the horizontal load-bearing capacities of the shear walls after the fire first increased and then decreased, with the critical value being in the range 0.2–0.25. The specimens damaged by explosive spalling retained considerable axial load-bearing capacities (i.e., 69 % of the sectional concrete compression-bearing capacity of the unfired wall).

Deep multitask learning with label interdependency distillation for multicriteria street-level image classification

Multitask learning (MTL) aims at beneficial joint solving of multiple prediction problems by sharing information across different tasks. However, without adequate consideration of interdependencies, MTL models are prone to miss valuable information. In this paper, we introduce a novel deep MTL architecture that specifically encodes cross-task interdependencies within the setting of multiple image classification problems. Based on task-wise interim class label probability predictions by an intermediately supervised hard parameter sharing convolutional neural network, interdependencies are inferred in two ways: i) by directly stacking label probability sequences to the image feature vector (i.e., multitask stacking), and ii) by passing probability sequences to gated recurrent unit-based recurrent neural networks to explicitly learn cross-task interdependency representations and stacking those to the image feature vector (i.e., interdependency representation learning). The proposed MTL architecture is applied as a tool for generic multi-criteria building characterization using street-level imagery related to risk assessments toward multiple natural hazards. Experimental results for classifying buildings according to five vulnerability-related target variables (i.e., five learning tasks), namely height, lateral load-resisting system material, seismic building structural type, roof shape, and block position are obtained for the Chilean capital Santiago de Chile. Our MTL methods with cross-task label interdependency modeling consistently outperform single task learning (STL) and classical hard parameter sharing MTL alike. Even when starting already from high classification accuracy levels, estimated generalization capabilities can be further improved by considerable margins of accumulated task-specific residuals beyond +6% κ. Thereby, the combination of multitask stacking and interdependency representation learning attains the highest accuracy estimates for the addressed task and data setting (up to cross-task accuracy mean values of 88.43% overall accuracy and 84.49% κ). From an efficiency perspective, the proposed MTL methods turn out to be substantially favorable compared to STL in terms of training time consumption.

Investigation on hysteretic performance of assembled H-shaped steel frame-corrugated steel plate shear wall with different corrugated orientation and wavelength

The hysteretic performance of assembled H-shaped steel frame-corrugated steel plate shear wall (HCSW) was investigated with low cycle reciprocating loading test. The assembled HCSW structure was used as lateral load-resisting system for high-rise building, and its stiffness was excellent. Compared with the traditional steel shear wall, the HCSW had better seismic performance. Moreover, when the frame was not damaged, the embedded corrugated steel plate could be easily disassembled and replaced. Three HCSW specimens with different steel plate corrugation orientation and the corrugation wavelength were fabricated. The hysteretic performance of three HCSW specimens was fully compared. The key issues, failure process, hysteresis curves, skeleton curves, carrying capacity and energy consumption were discussed in depth. The corrugated steel plate was yielded prior to the frame column, indicating that the HCSW specimens behaved as a desirable sequence of material yielding. The energy consumption performance of HCSW specimen was well. The ductility and carrying capacity of HCSW specimen with small wavelength were greater than that of other two specimens. In addition, the hysteretic performance of HCSW specimen was simulated based on the established finite element model analysis. The simulated results of finite element model were in good agreement with the test results. The effects of corrugated steel plate width-to-thickness ratio, width-to-height ratio and axial compression ratio on the performance of assembled HCSW were analyzed and discussed based on the finite element model. And according to the results, the design suggestions of assembled HCSW were given. This research aimed to provide a reference for the design and evaluate the application of current design of provision for assembled HCSW. The application of the HCSW could avoid economic losses and reduce construction time.

Analysis of the Feasibility of a Diagrid Bracing System in Tall Buildings

Abstract: The primary goal of this study is to provide a superior lateral load-resisting system. In this study, the diagrid structural system is considered, with the shear wall core present at the center part of the building and the diagrid bracings provided at the outer periphery of the structure, which is formed of steel material. The diagrid, which is made up of inclined diagonal steel sections, allows the diagonal member to function axially to resist lateral loads. Due to its structural effectiveness and versatility in architectural planning, the diagrid structural system has recently been used in tall buildings. A 14-story Diagrid composite building is selected, and its analysis and design results are presented. The Diagrid bracing system is connected to the end bays, the diagrid bracing system is connected to the mid-end bays, and the diagrid bracing system is connected to the end bays these are the three different types of models that have been studied. The diagrid bracing system has been modeled by using structural steel material, and the remaining structure has been modeled by using concrete material. A standard 60 m x 60 m floor plan has been considered. FEM-based software called ETABS has been used to model and analyze structures. A PT slab and a PT band beam have been used in the model frame for the span of 10 m. By considering all possible load combinations, all structural members made of steel and concrete are analyzed by IS: 800:2007 and IS: 456:2000, respectively

Aerodynamic optimization for corner modification of octagonal-shape tall buildings using computational approach

Tall buildings are particularly susceptible to wind loads, which usually govern the design of lateral load-resisting systems. Therefore, wind loads must be adequately evaluated in the design of tall buildings. Aerodynamic modifications are highly effective tools for reducing wind loads. This paper investigates the effectiveness of corner modification optimization applied on an octagonal-plan-shaped model using computational fluid dynamic (CFD) simulation computational fluid dynamics associated with finite element analysis to alleviate wind-induced loads. Corner aerodynamic modifications such as chamfered, recessed, rounded, and fins are investigated. The corner modification was limited to a cutting radius of 6 m (12% of the building width) with a 0.5 m increment. The main considerations for this optimization procedure are top deflection, inter-story drifts, and the optimal number of additional floors. All corner modifications improve the building's performance, except fins corners resulting in adverse effects. In addition, 47 simulation examples from the case study are evaluated, presented, and discussed. With one additional floor, the optimum shape was able to reduce overall wind loads by 31.67%, resulting in a reduction in the structural response of 24.89% and 24.18% in maximum top deflection and inter-story drift, respectively.

Review of recently constructed concrete wall-steel frame hybrid buildings

Around New Zealand there has been an increasing trend of ‘hybrid’ multi-storey buildings that combine reinforced concrete walls with structural steel framing systems. This study aims to characterise and understand this type of building, focusing on buildings constructed in Auckland and Christchurch from 2014 onwards. Drawings from a total of 50 buildings were reviewed, and their structural features were documented, including building use, building height, lateral load resisting system, ductility, wall configuration, wall construction method, steel framing system and suspended floor system. Meetings with structural engineers were conducted to validate the review findings and to further understand design principles and decisions that lead to these outcomes. A typology comprising five building types with distinct lateral load-resisting systems was proposed based on the building review. Results showed regional differences between Auckland and Christchurch, owing to building use and seismic hazard in the respective cities. Auckland buildings surveyed tended to be residential buildings five storeys or higher made of precast walls connected with steel beams. Christchurch buildings, on the other hand, were primarily commercial buildings three to seven storeys high with dual frame-wall systems. Structural connections between steel frames and concrete walls were also documented, showing that bolted connections with headed stud embedment were most common. The results can be used to identify critical aspects of these mixed structural systems for further investigation and to develop archetype building designs that can be used for modelling and testing.

Seismic resistance of buckling restrained steel slit panels with X-Shaped restrainers

Steel slit panels (SSPs) serving as lateral load-resisting systems are steel plates (SPs) with rows of vertical slits forming a series of flexural links. The main deficiencies of SSPs subjected to shear forces are fair seismic performance characteristics due to either out-of-plane deformation of long links or fracture of relatively short links. To alleviate this problem, novel buckling restrained SSPs with X-shaped restrainers (referred to as XSSPs) are proposed in the current study. The restrainers are placed on both sides of SSPs to restrain only out-of-plane buckling of links. Refined finite element models of these systems are established and verified by the experiments. The explicit analysis is conducted on these models to evaluate the effects of different patterns of X-shaped restrainers on the seismic performance of these systems. Other parameters considered in this work, include the width-to-thickness ratio of the links, the length-to-width ratio of the links, the number of rows of links, and the width of edge stiffeners. It is found from the results that the hysteresis responses of XSSPs are rather stable with a large energy dissipation capacity. The pinching enhancement is particularly high in cases with a lower length-to-width ratio of the links. Applyin more restrainers in XSSPs models with a lower width-to-thickness ratio and a higher length-to-width ratio of the links improved the strength and the initial stiffness significantly. The strength and stiffness increases due to using diagonal X-shaped restrainers can reach up to 400% and 900%, respectively. The XSSPs have exhibited superior energy dissipation increases more than two times compared with the corresponding SSPs and SPs.

Parametric study on the partially interconnected steel plate shear walls with stiffeners

Steel plate shear walls are a popular and effective lateral load-resisting system used in high-rise buildings. However, limited interconnection between the infill plate and boundary elements is recommended to avoid direct demands on the boundary elements and brittle modes of behavior. But previous studies have shown that the absence of interconnection between infill plates and columns in steel plate shear walls with beam-connected systems can reduce the system’s performance significantly. This study proposes procedures to improve the performance of steel plate shear walls with limited infill plate interconnections. Sixty-two parametric computational models were investigated with and without boundary infill plate stiffeners and different infill plate widths to find efficient procedures for eliminating the lack of interconnections. Results show that utilizing boundary stiffeners can increase ultimate strength, energy dissipation, and stiffness by 15%, 20%, and 24% on average. The width of the infill plate and boundary stiffeners are identified as key factors in the system’s performance. Reducing the infill plate width without using stiffeners exacerbates the performance of the lateral resisting system, resulting in a reduction of ultimate strength, energy absorption, and stiffness up to 17%, 24%, and 56%, respectively. Analytical equations are proposed and verified to predict the behavior of steel plate shear walls with partial infill plate interconnections with or without boundary stiffeners. Overall, the study provides procedures and recommendations to improve the performance of steel plate shear walls with limited infill plate interconnections.

Profound Impact of Shear Wall on Stability of Regular and Irregular Reinforced Concrete Structures – A Review

A shear wall is a straight-up segment of a structural system that is inevitable to fend off lateral pressures that are in-plane, including wind and earthquakes. It is one of the main structures that resist vertical and horizontal forces acting in its plane with rather stiff resistance. Provision of stability by assuring ductility of the structure and hence improving the resistance against oblique loads coming on the structure. They are considered as a reinforced braced system that ensures the load-carrying capacity of tall structures. Each component's load attraction is deeply affected by its position and relative stiffness. So, for structural advantages, the dimensions, height, and geometry of the shear wall system should be considered, especially in irregular structures. The type and characteristics of the shear wall should be considered before construction. This review can be recommended for future studies on the stability of structures with lateral load-resisting systems. This study deals with the relative analysis of the research trend on the stability of structures with different shear wall conditions on the topic at hand and the results of the poll, all-inclusive outcomes are provided in conclusions that form the ideas of the additional study.

Automated minimum-weight sizing design framework for tall self-standing modular buildings subjected to multiple performance constraints under static and dynamic wind loads

In recent decades, the shortage of affordable housing has become an endemic issue in many cities worldwide due to the ongoing urban population growth. Against this backdrop, volumetric steel modular building systems (MBSs) are becoming an increasingly compelling solution to the above challenge owing to their rapid construction speed and reduced upfront costs. Notwithstanding their success in low- to mid-rise projects, these assembled structures generally rely on a separate lateral load-resisting system (LLRS) for lateral stiffness and resistance to increased wind loads as the building altitude increases. However, additional LLRSs require on-site construction, thereby compromising the productivity boost offered by the MBSs. To this end, this paper proposes a novel optimisation-driven sizing design framework for tall self-standing modular buildings subjected to concurrent drift, floor acceleration, and member strength constraints under static and dynamic wind loads. A computationally efficient solution strategy is devised to facilitate a meaningful sizing solution by decomposing the constrained discrete sizing problem into a convex serviceability limit stage (SLS) and a non-convex ultimate limit stage (ULS), which can be then solved using preferred local and global optimisation methods, separately. The framework is implemented by integrating SAP2000 (for structural analysis) and MATLAB (for optimisation) through SAP2000′s open Application Programming Interface (API), and demonstrated using a 15-storey self-standing steel modular building exposed to three different levels of wind intensity. A comprehensive performance assessment is conducted on the optimally designed case-study building to investigate its elastic instability behaviour, geometric nonlinear effects on wind-induced response, and impacts of global sway imperfections on member utilisation ratios under wind effects. It is concluded that tall self-standing modular buildings can be achieved economically using ordinary corner-supported modules without ad hoc structural provisions, while consuming steel at similar rates to conventional building structural systems. Furthermore, the proposed sizing framework and solution strategy have proven to be useful design tools for reconciling the structural resilience and material efficiency in wind-sensitive self-standing modular buildings.

ANN-based optimization framework for the design of wind load resisting system of tall buildings

Conventional design methodology for tall buildings is a time-consuming and repetitive trial-and-error procedure with a limited probability of yielding an optimal solution that satisfies architectural, structural and serviceability requirements. Tall buildings are typically slender structures and mainly depend on lateral load resisting systems (LLRS) (e.g., shear walls, cores, and bracing systems) to withstand the lateral load of earthquakes and wind events, where a minor change in their layout, size, or shape will affect the cost tremendously. Consequently, an automated layout optimization procedure will result in a more economic and sustainable design. This paper develops a novel structure-wind optimization framework (SWOF) to find the optimal shear wall layout of tall buildings subjected to wind loads. SWOF is considered a genetic algorithmbased framework that uses an Artificial Neural Network (ANN) surrogate model to evaluate its constraints and objective function. These surrogate models rely on a training dataset prepared using the Finite Element Method (FEM), which has been created using an open application program interface (OAPI) MATLAB code. An optimization problem; is presented to show SWOF's efficiency. SWOF showed significant capabilities in recognizing load direction, critical load cases and inertia concepts without explicitly defining them through the developed code.

Collapse Assessment of Mid-Rise RC Dual Wall-Frame Buildings Subjected to Subduction Earthquakes

In Chile, office buildings are typically reinforced concrete (RC) structures whose lateral load-resisting system comprises core structural walls and perimeter moment frames (i.e., dual wall-frame system). In the last 20 years, nearly 800 new dual wall-frame buildings have been built in the country and roughly 70% of them have less than ten stories. Although the seismic performance of these structures was deemed satisfactory in previous earthquakes, their actual collapse potential is indeed unknown. In this study, the collapse performance of Chilean code-conforming mid-rise RC buildings is assessed considering different hazard levels (i.e., high and moderate seismic activity) and different soil types (i.e., stiff and moderately stiff). Following the FEMA P-58 methodology, 3D nonlinear models of four representative structural archetypes were subjected to sets of Chilean subduction ground motions. Incremental dynamic analysis was used to develop collapse fragilities. The results indicate that the archetypes comply with the ‘life safety’ risk level defined in ASCE 7, which is consistent with the observed seismic behavior in recent mega-earthquakes in Chile. However, the collapse risk is not uniform. Differences in collapse probabilities are significant, which might indicate that revisions to the current Chilean seismic design code might be necessary.