Seismic Force-resisting System Research Articles

COMPARISON BETWEEN SMF AND SPSW STEEL BUILDING FOR MIXED-USE RESIDENCE USING THE AHP METHOD

The objective of this work is to compare the Special Moment Frame (SMF) system and the Steel Plate Shear Wall (SPSW) system using the AHP multi-criteria comparison method with the two Seismic Load Resisting Systems (SFRS). From the linear static analysis, dynamic analysis, and nonlinear static analysis (Pushover), representative characteristics of each Seismic Force-Resisting System (SFRS) are determined. These characteristics include the structure's self-weight, target displacement, floor drifts, and seismic response modification factor (R). As a result, two buildings are obtained with different SFRS that comply with the design of their elements and checks according to the regulatory requirements. After determining the capacity curve of each Seismic Force-Resisting System (SFRS) and assessing the performance level of the buildings, the conclusion is drawn that the Special Plate Shear Wall (SPSW) system is more suitable and advantageous compared to the Special Moment Frame (SMF) system. This preference is due to the SPSW system's ability to provide ductility, which translates into higher energy dissipation capacity, and stiffness, which leads to reduced floor drifts in the building.

Seismic performance assessment of post-tensioned CLT shear wall buildings with buckling-restrained axial fuses

Post-tensioned cross-laminated timber (PT-CLT) walls have been demonstrated to be a low-damage seismic force-resisting system (SFRS) due to their self-centering capability. However, there is still a need to examine the seismic performance of such SFRS in high-seismic risk zones. This study evaluates the seismic performance of 6-, 9-, and 12-storey PT-CLT shear wall buildings in Vancouver, Canada, equipped with buckling-restrained axial fuses. The prototype buildings were designed using the displacement-based design method, and the assessment considered the most recent seismic hazard model provided in the 2020 National Building Code of Canada. To conduct nonlinear response history analysis (NLRHA) and incremental dynamic analysis (IDA), numerical models were developed in OpenSeesPy and calibrated based on component- and system-level experimental tests. The NLRHA and IDA results demonstrate that all the studied buildings have adequate collapse margin ratios, with less than a 10% chance of collapsing at the maximum considered earthquakes.

Numerical assessment of TMS 402/602-22 and CSA S304-14 seismic design provisions for partially grouted reinforced masonry shear walls failing in flexure

Despite the economic benefits of using partially grouted reinforced masonry shear walls (PG-RMSWs) as a seismic force resisting system (SFRS) in low-rise buildings, using such a system in mid- and high-rise buildings is still questionable. This is because the literature lacks comprehensive studies investigating different seismic design provisions adopted for rectangular and flanged PG-RMSWs of aspect ratios greater than 2.0 and failing in flexure. Therefore, this study aims to conduct a comprehensive numerical assessment of the seismic design provisions of the North American masonry standards (i.e., TMS 402/602–22 and CSA S304–14) for designing different categories of rectangular and flanged PG-RMSWs failing in flexure. In this regard, 108 PG-RMSWs were designed and modeled using the Extreme Loading for Structures (ELS) software. Afterward, some changes were proposed to the current seismic design provisions in CSA S304–14 and TMS 402/602–22 for rectangular and flanged PG-RMSWs. In addition, a comparison was made between the seismic design provisions for PG-RMSWs and FG-RMSWs, designed according to each RMSW category, to investigate the expected differences in the behavior based on the applied seismic design provisions. Accordingly, additional 36 FG-RMSWs were designed according to CSA S304–14 and TMS 402/602–22. These additional walls were then modeled on the ELS and compared with their PG counterparts. The results show that both standards can be safely used to design rectangular and flanged PG-RMSWs only when using the two proposed provisions for each standard. For CSA S304–14, the possibility of updating clause 16.8.5.2 is concluded, allowing the use of PG-RMSWs without limitations. New seismic force modification factors were also proposed for TMS 402/602–22 for the design of rectangular and flanged PG-RMSWs. Finally, the comparison between rectangular PG and FG-RMSWs failing in flexure and designed according to CSA S304–14 and TMS 402/602–22 shows that the behavior of PG-RMSWs failing in flexure is comparable to FG-RMSWs under certain circumstances. This study is considered a significant step to prove the potential for more economical and safe usage of PG-RMSWs in mid- and high-rise buildings.

Reinforced concrete wall buildings with force‐limiting connections: Modeling effects and uncertainty propagation

AbstractThis paper assesses the effects of (1) the gravity load‐resisting system (GLRS) modeling approach, (2) the seismic force‐resisting system (SFRS) modeling approach, and (3) the uncertainty of the model parameters of the constitutive law of the longitudinal reinforcing steel of the SFRS on the seismic responses of a 12‐story reinforced concrete wall building with force‐limiting connections. This is achieved by conducting nonlinear numerical earthquake simulations. The seismic responses of the building models with force‐limiting connections using two GLRS modeling approaches, (1) a moment frame system and (2) a pin‐base lean‐on‐column system, are compared. The seismic responses of the building models with conventional connections and force‐limiting connections, respectively, using two SFRS modeling approaches, (1) a distributed‐plasticity modeling approach and (2) a lumped‐plasticity modeling approach, are compared. A joint probability density function for the ASTM‐A615 Grade 60 steel available in the literature is used to conduct an uncertainty propagation analysis through Monte Carlo simulation. The uncertainty in the steel model parameters is propagated to the seismic responses of the building models with conventional connections and force‐limiting connections, respectively. The distributions of the mean values of the peak structural responses of the building models are studied. The effects of the GLRS modeling approach on the seismic responses are not significant in the context of seismic performance‐based design and assessment of buildings with force‐limiting connections. The effects of the SFRS modeling approach and the uncertainty in the steel model parameters on the floor total acceleration and force responses are reduced by including force‐limiting connections.

Effect of boundary element detailing on the seismic performance of reinforced concrete masonry shear walls

Laboratory tests demonstrated that reinforced masonry shear walls (RMSWs) can provide sufficient strength and ductility to be considered an efficient seismic force resisting system (SFRS) for mid-rise buildings. The ductility and overall seismic performance of shear walls were increased by providing confinement to the end zones of the walls to form boundary elements (BEs)., which enhanced the ultimate masonry compressive strain and curvature ductility of the walls. Regular stretcher blocks are commonly used in the construction of masonry boundary elements; however, they impose some constraints due to their geometrical characteristics. This study investigated the construction and testing of three half scale specimens of reinforced masonry shear walls with boundary elements (RMSWs+BEs) that were characterized by flexural dominance under reversed cyclic moment and lateral loading. In the lower story panel of a 12-story RMSW building, these walls constitute the plastic hinge zone, which is represented by a plastic hinge wall. In this study, C-shaped masonry units were used instead of stretcher units to construct BEs with different sizes and vertical reinforcement ratios. The findings of this work revealed that employing C-shaped masonry units to construct the BEs was effective in overcoming the construction limits imposed by stretcher units. Additionally, the results of this study demonstrated that when RMSWs+BEs are subjected to quasi-static reversed cyclic loading, they are capable of providing a high level of ductility with minimal loss of strength.

Structural Performance of Buildings with Tension-Only Braced Frame Under Seismic Loading

In accordance with SNI 1726-2019, structures with tension-only braced frames (ToBF) can be used as seismic force-resisting systems for seismic design category (SDC) A to C, with a height of up to 10m. Limited study was done on this subject, hence a numerical study was conducted to better understand the structural performance. The models studied were of regular structures of SDC D, varying in height. The analyses used modal response spectrum analysis (MRSA) for design, and linear response history analysis (LRHA) to evaluate the response. Finally, pushover analyses were conducted to determine the structural performance levels. The study shows that structural design can be done for all models using MRSA, satisfying all requirements. When evaluated using LRHA, results reveal that requirements were not satisfied for structures with heights exceeding 10m. Analysis when reviewed using pushover analysis, results show that the performance levels for all buildings are Immediate Occupancy. However, for models with height exceeding 10m, first yielding occurs at a lower base shear than the design base shear, indicating that the value of R used may not be adequate. Further review reveals that the ToBF can be used as a seismic force-resisting system, with proper design and arrangements.

IDA-Based Collapse Safety Assessment of Torsional-Irregular Buildings, Considering Ductility and Damage

The complexity in nonlinear behavior of torsional-irregular buildings in combination with uncertainty due to the natural randomness of earthquake records has been always a main challenge for buildings’ seismic design. To find a solution to this challenge, three reinforced concrete (RC) building archetypes were designed and next developed into their nonlinear models. Nonlinear static (pushover) analyses were performed to calculate the capacity of the archetype models in all principal and non-principal directions while incremental dynamic analyses (IDAs) were conducted by applying 30 accelerograms from both near-field and far-field earthquakes. The IDA capacity curves, collapse fragility curves and log-normal cumulative distribution functions (CDFs) were established by including both the aleatory randomness and epistemic uncertainty. Despite previous studies wherein fragility curves were given by evaluating structures’ collapse along structural reference axes or simply on [Formula: see text], [Formula: see text]-axes, in this paper, possible building collapse on a critical non-principal direction (where maximum seismic response was observed) was simulated and its probability was accounted for developing IDA curves and log-normal CDFs. Accordingly, this issue was mirrored in computing available/acceptable collapse margin ratios (CMRs). In addition to the well-known outline used for calculating CMRs in the literature (that is based on estimation of collapse capacity in terms of earthquake intensity measure (IM)), the framework proposed here includes a new method for calculating the CMRs in terms of displacement-based drift, ductility, and damage. The superiority of the proposed method over the former is consistent with the buildings’ design procedure that is governed by storey drift control rather than base-shear strength. Refined statistics of CMRs given by taking into account displacement-based responses illustrate the available CMRs exceed the acceptable CMRs, meaning that a satisfactory safety margin against collapse will be anticipated in the targeted building class if a suitable yielding mechanism with sufficient ductility is provided for seismic force-resisting system by applying seismic design provisions of the current codes.

Experimental parametric study of perforated steel plate fuses for mass timber seismic force resisting systems

The lack of practical connections with reliable desired energy dissipation capacity as the main components of a seismic force resisting system (SFRS) is a major obstacle in using mass timber in tall buildings located in seismically active regions. A common method to dissipate seismic energy in timber structures is through the yielding of steel material found in the mechanical connections. Under the induced seismic motions, these dissipative connections are intended to yield while the rest of the structure remains intact with minimum damage. In this research, the focus is on the use of perforated steel plate as a dissipating energy device and a seismic fuse. Previous tests have demonstrated the potential use of perforated steel plates as seismic fuses in mass timber SFRS and confirmed their scalability and predictability. Despite promising results under monotonic loading, their behavior under cyclic loading can be improved. This paper presents an experimental parametric study investigating the effects of the number of rows, shape, and size of perforations, the steel plate thickness, and the steel link size on the mechanical performance of the perforated plates. The obtained hysteresis responses and envelope curves are compared. It is found that the ellipse and stagger patterns possess the largest ultimate displacement and stiffness, respectively. In addition, no significant enhancement in the ultimate deformation was observed in the cyclic response of the fuse, beyond three rows of perforations. Within the range of the configurations considered, the reduced ultimate deformation under cyclic loading remains a technical challenge that needs to be addressed if this type of seismic fuse is to be installed in SFRS. The results will assist with the design of future test programs on full-size mass timber connections consisting of such fuses.

Energy-based seismic design and assessment of ductile linked rocking steel frame

Ductile linked rocking steel frame (DLRF) is an innovative and efficient structural system that combines two gravity-controlled rocking steel braced frames with corrugated steel plate links. DLRF is designed to dissipate input seismic energy through the uplifting and yielding of the rocking column base and yielding of the corrugated steel plate link. To ensure the DLRF can achieve superior seismic performance at various shaking intensities, the equivalent energy design procedure (EEDP) is adopted to design DLRF. In this paper, two prototype DLRF buildings (3 - and 6 - story) were designed using EEDP. Robust numerical models were established to verify the seismic performance of the DLRF. Nonlinear dynamic analyses confirm that the DLRF designed using EEDP can achieve the desired performance objectives at different levels of earthquake shaking intensities. In addition, the results of the incremental dynamic analyses show that DLRF has a sufficient safety margin against collapse. Hence, DLRF can be used as an alternative seismic force-resisting system.

Structural connection with predetermined discrete variable friction forces

This paper presents a simple and practical structural connection able to develop predetermined discrete variable friction forces at target design displacement levels. The innovative connection is termed Modified Friction Device (Modified FD). Modified FDs are used to transfer the seismic induced horizontal forces from the floors to the core wall seismic force-resisting system of a building. The schematics of the physical embodiment of the Modified FD are presented. The components and the assembly of the Modified FD are discussed. The mechanics of the Modified FD are explained. Results from static structural analyses of two types of finite element models of the Modified FD are presented. The first model is developed using solid finite elements and it is used to assess the expected kinematics and the expected force-displacement response of the Modified FD. The second model is developed using a truss finite element and it can be used to efficiently simulate the force-displacement response of the Modified FD in numerical earthquake simulations of structural systems. The force-displacement response of the Modified FD computed using a numerical earthquake simulation of an eighteen-story reinforced concrete core wall building model is presented. The seismic response of the building model with Modified FDs is compared with the seismic response of the building model with monolithic connections and the seismic response of the building model with friction devices with constant friction forces. The results presented in this paper show that it is possible to develop a simple and practical structural connection with predetermined discrete variable force-displacement response to limit the seismic induced horizontal forces transferred between the floors of the flexible gravity load resisting system and the core wall piers in high-performance earthquake resilient buildings.

Evaluation of Seismic Acceleration Demands on Mechanical Support Systems

Earthquakes are among the most influential force of nature that affect human life. Reconnaissance after the severe earthquakes pointed out that seismic performance of non-structural members and elements could be as significant as the structural members in lateral force-resisting systems. As such, it is important for design engineers to recognize the seismic demand on the mechanical systems that support the critical non-structural components (e.g., sprinklers, electrical and mechanical equipment, etc.) in terms of the safety during and after an earthquake as well as functionality and retrofitting cost after an earthquake. The primary goal of this study is to systematically investigate the seismic demands on the mechanical support systems of a typical mid-rise steel structure. For this purpose, non-linear time history analyses are carried out using a suite of ground motion acceleration records to evaluate the seismic demands on both seismic force-resisting system and the support system by means of inter-story drift angle and horizontal accelerations, respectively. Results obtained from the analyses are discussed considering the requirements stipulated in the current national and international buildings and recommendations are made.

Impact of unique practice in concentrically braced frames on their seismic performance

The seismic provisions for special concentrically braced frame (SCBF) expect the braces capable of providing deformation of 10–20 ductility without fracture in order to withstand design earthquake ground motions. Seismic evaluation studies of the design provisions for SCBF, however, are substantially different from those for any other seismic-force-resisting system (SFRS) in three aspects: (a) the original design provision for a SCBF set a b/t ratio limit on braces to prevent fracture, but such b/t ratio limit is proven incapable of preventing brace fracture; (b) SCBF is the only SFRS in which the brace fracture termination of energy-dissipation mechanism is considered normal instead of the limit state of seismic design; and (c) the collapse probability evaluation and development of design parameters (R, Ω0, Cd) are formulated explicitly including potential but uncertain overstrength factors inherently existing in typical steel buildings. This paper describes a comprehensive inquiry into the origin and evolution of the unique practice in SCBF over a span of 30 years (1992–2022) and its impact on seismic performance and potential hazard of steel buildings with SCBF as a designated SFRS in steel buildings. The important conclusions include (a) seismic braces have fracture ductility range of 5–10; (b) the seismic design provisions and performance evaluation on SCBF have been based on post brace-fracture analysis of buildings with SCBF that is extremely unreliable and often overly optimistic; and (c) The unique seismic design practice of SCBF has a significant impact on seismic performance of steel buildings with SCBF.

Experimental assessment on aseismic capacity of a perimeter diagrid concrete core structure: Shake table tests

Perimeter diagrid concrete core (PDCC) is a structural system used for high-rise building applications. Quantifying their seismic safety is of interest to owners and decision makers due to the lack of the comprehensive understanding of the seismic performance of the high-rise PDCC structure. To systematically evaluate the seismic performance, a 36-story PDCC structure has been assessed using 1/20 scaled shake table tests. In addition, a detailed nonlinear finite element model (FEM) of the PDCC structure was built for comparison and analysis with the shaking table test. The damage to the perimeter diagrid bracings, the RC structural walls, the diagonal beam, under earthquake excitations have been assessed and discussed systematically based on the experimental and numerical results. The analysis result shows that the PDCC structure has a high performance under the earthquake load that can be used as an efficient seismic force-resisting system. Under the action of horizontal earthquakes, the axial force of the diagonal braces on the same floor varies greatly, and the axial force of the diagonal brace is related to the number of other diagonal braces on its axis. In terms of seismic damage to the perimeter diagonal braces, the most severe seismic damage is concentrated in the diagonal braces with higher axial forces, while the damage to other diagonal braces with smaller axial forces is less severe. And the seismic damage of diagonal bracing has a tendency to expand to other surrounding diagonal braces.

Seismic response analysis of reinforced masonry core walls with boundary elements

The seismic design of mid- and high-rise reinforced masonry (RM) structures necessitates a reliable seismic force resisting system (SFRS) that provides adequate capacity and ductility. Core walls are commonly used as the SFRS for counterpart reinforced concrete buildings due to the convenience of locating the elevators and staircases inside it. This study introduces reinforced masonry core walls with boundary elements (RMCW+BEs) as a potential SFRS alternative to rectangular reinforced masonry shear walls (RMSWs) with and without boundary elements given their enhanced structural and architectural characteristics in typical RM buildings. A macroscale nonlinear numerical model was developed using the Extreme Loading for Structures software (ELS) to evaluate the seismic performance of RMCW+BEs. A nonlinear time history analysis (NLTHA) was carried out for three archetype RM buildings with 10-, 15-, and 20-story heights designed according to the CSA S304-14 and located in a North American moderate seismic zone. The results showed that utilizing RMCW+BEs as the main SFRS system adequately controlled the seismic demands on RM buildings subjected to typical North American ground motions. However, the 20-story building showed a shear demand exceeding the nominal flexural resistance of the core wall at the plastic hinge region at the base, which was attributed to the adverse effect of the higher modes of vibration effects on the seismic demand parameters. Therefore, the three buildings were redesigned using a dual plastic hinge (DPH) design approach. The numerical results demonstrated that using the DPH reduced the shear demand and mitigated the effect of the higher modes of vibration on the seismic response of the core walls. The findings of this study highlight the need to integrate a new shear demand magnification factor to account for the higher mode effects in estimating the seismic demand of ductile RMSWs in the next generation of the North American design standards for masonry structures.

BLAST LOADING EFFECT ON CHEVRON TYPE BUCKLING RESTRAINED BRACED FRAMES

Buckling Restrained Braced Frames (BRBF) are being used all over the world as a seismic force resisting system in building structures. BRBFs are used due to their high ductility after yielding and the ability to absorb energy. Currently, American Society of Civil Engineers (ASCE) permits the use of BRBFs as a single seismic force-resisting system by quantifying the seismic parameters such as Response Modification Coefficient (R), Over-strength Factor (Ωo) and Deflection Amplification Factor (Cd) in their latest code ASCE 7-16. The purpose of this research is to investigate how a structure built with BRBF to resist seismic forces behaves when subjected to blast loading. In other words, this paper focuses on the effect of blast loading on Buckling Restrained Braced Frames. The investigation is carried out on a Chevron type braced frame. The frame is subjected to a short duration blast loading that lasts only 21.7 mili-second (ms). Blast loading effects on the braced frame are assessed by identifying the weakest plane of failure, deformation characteristics and out of plane bending. The research also investigates the effect of brace core thickness on resisting blast loading. It is observed that the brace core thickness plays a significant role in reducing the deformation characteristics.

Performance-based design of steel frames with self-centering modular panel

The self-centering modular panel (SCMP) is an emerging seismic resilient lateral force-resisting system. This paper intends to develop a performance-based design (PBD) method for steel buildings equipped with the SCMPs based on the concept of direct displacement-based design methodology. The theoretical hysteretic model of the SCMP consisting of the post-tensioned frame (PTF) and four replaceable hysteretic dampers (RHD) is proposed and validated in this paper. Based on the proposed theoretical hysteretic model, the equation for the equivalent damping ratio of the steel buildings with SCMP is developed and the PBD method is proposed. The 3-story and 6-story steel frames equipped with the emerging SCMP are established through the developed PBD procedure. Static analyses were performed to investigate the nonlinear responses of the established buildings. Twenty ground sequences were chosen and scaled to evaluate the seismic responses of the designed steel frames subjected to different seismic intensity levels through nonlinear dynamic analyses. The results of the research show that steel structures equipped with SCMPs established through the developed PBD procedure can display the expected hysteretic behavior and performance under earthquakes. The designed buildings can achieve excellent post-earthquake recoverability by keeping the residual displacement in each story less than 0.5% even under earthquakes with MCE intensity.

BLAST LOADING EFFECT ON CHEVRON TYPE BUCKLING RESTRAINED BRACED FRAMES

Buckling Restrained Braced Frames (BRBF) are being used all over the world as a seismic force resisting system in building structures. BRBFs are used due to their high ductility after yielding and the ability to absorb energy. Currently, American Society of Civil Engineers (ASCE) permits the use of BRBFs as a single seismic force-resisting system by quantifying the seismic parameters such as Response Modification Coefficient (R), Over-strength Factor (Ωo) and Deflection Amplification Factor (Cd) in their latest code ASCE 7-16. The purpose of this research is to investigate how a structure built with BRBF to resist seismic forces behaves when subjected to blast loading. In other words, this paper focuses on the effect of blast loading on Buckling Restrained Braced Frames. The investigation is carried out on a Chevron type braced frame. The frame is subjected to a short duration blast loading that lasts only 21.7 mili-second (ms). Blast loading effects on the braced frame are assessed by identifying the weakest plane of failure, deformation characteristics and out of plane bending. The research also investigates the effect of brace core thickness on resisting blast loading. It is observed that the brace core thickness plays a significant role in reducing the deformation characteristics.

A Procedure for Assessing Low-Cycle Fatigue Life of Buckling-Restrained Braces

AbstractBuckling-restrained brace frames (BRBFs) have been a popular seismic force-resisting system in the US since it was first introduced to the AISC Seismic Provisions and ASCE 7 in 2005. The st...

A Framework for the Quantification of Non-Structural Seismic Performance Factors

ABSTRACT With the advancement of performance-based earthquake engineering (PBEE), the seismic performance of non-structural elements (NSEs) has gained special relevance. The harmonization of the performance of NSEs and of the seismic force-resisting system (SFRS) in a building is fundamental to the PBEE concept. To provide a consistent level of performance for force-based designed SFRSs, the FEMA P695 Methodology provides an objective framework. No equivalent procedure currently exists for NSEs. This paper develops a framework to quantify seismic performance factors for NSEs. An illustrative case study example is presented for the calibration of the behaviour factor for suspended piping seismic restraint installations.

Nonlinear static and dynamic behaviors assessment of self-centering post-tensioned concrete wall with multiple-slit device

Conventional seismic force-resisting systems usually experience significant structural damage, and repairing such buildings is not economical. A new type of seismic force-resisting system is self-centering Post-Tensioned Concrete Wall (PT-CW), in which vertical Post-Tensioned (PT) cables supply the return force of the structure to its initial state. This study is dedicated to investigate the seismic behavior of the self-centering PT-CW system using nonlinear static, cyclic, and response history analyses. The loading and design of the studied buildings are performed in the 3D model, then one of the frames is selected and the nonlinear analyses are done in OpenSees software. In order to increase the absorption energy of PT-CW, a Multi-Slit Device (MSD) is employed. For this purpose, three systems including PT-CW with Energy Dissipators (ED) bars, PT-CW with MSD, and traditional Concrete Shear Wall (CSW) are modeled in Opensees software. These seismic force-resisting systems are applied into three, six, and ten-story buildings. To validate the proposed models, the results of an experimental study are applied. Then, the nonlinear responses of the introduced models are numerically obtained as well. Accordingly, the PT-CW with MSD has more ductility and less strength drop than the other two systems. Finally, ten far-field earthquake records are selected and scaled with the ASCE spectrum to implement NRH analysis. As a result, it is observed that the story drift of the PT-CW with MSD under the applied earthquake records is almost uniform and less than the PT-CW with ED bars.