Story Drift Research Articles

Dynamic response of RC frames retrofitted with friction-damped brace system through shaking table tests

This study presents the shaking table test results of two-dimensional reinforced concrete (RC) frames retrofitted with a simplified friction damped brace. An easy-to-manufacture and install friction damper with economical design, was proposed and tested under reversed cyclic loading and used to retrofit RC frames. The splice of a conventional steel brace was converted into a friction damper, which not only dissipated seismic energy but also helped avoid the buckling of the steel brace. The test scheme consisted of four RC frames, and the behaviors of the three retrofitted frames were compared with that of a non-retrofitted (bare) frame. The shaking table tests were conducted using an artificial seismic wave that reflected the short-period response characteristics of the Korean earthquake. The test results of the bare and retrofitted frames were analyzed by considering several important performance indicators, such as the cracking and fracture mechanism in the RC frames, base share, and story drift ratios. The results of the shaking table tests demonstrated that the proposed damped brace effectively reduced earthquake-induced drift demands and successfully shifted the fracture and damage concentration from the columns to the beams.

Effects of modeling assumptions on prediction of seismic demands of a single-story RC structure

This study investigates the seismic response of a single-story reinforced concrete (RC) structure subjected to strong ground motions. Effects of modeling assumptions used to idealize the reinforcement slip in beam-column joints and column footing are studied. For this purpose, the numerical model of a single-story, single-bay, three-dimensional asymmetric RC structure, tested on a shake table and its symmetric version, is analyzed. Two modeling approaches are considered to show the significance of rotation associated with the reinforcement slip. Bidirectional nonlinear time-history analyses are conducted using symmetric and asymmetric 3D models. In these analyses, 30 pairs of near-field ground motions, selected and scaled to match the target spectrum, are used. The findings indicate that the neglection of reinforcement slip in numerical model may result in an underestimation of almost 50% in story drift ratio demands.

Impact of strongback on structure with varying damper and stiffness irregularity arrangements

Structures susceptible to soft story mechanisms are particularly vulnerable to earthquakes because damage concentrated at a single story can lead to premature failure of the structure. The strongback, a stiff vertical spine pinned at the structure's base and running its height, has been proposed as a way to impose a more uniform pattern of floor displacements and prevent soft story mechanisms. However, changes in the impact of strongbacks on the performance of structures remain unclear when considering vertical stiffness irregularities at different positions along the height of a structure and different arrangements of energy dissipation devices in a structure. This study aims to address these gaps through an extensive parametric experimental investigation varying the location of vertical stiffness irregularities and the arrangement of dampers in a small-scale four-story elastic structure with and without a strongback. For this study, each configuration of the structure is loaded with shake table-produced seismic ground motion. The results of this study show that, regardless of which story a stiffness irregularity is located, the strongback significantly reduces the maximum story drift in the structure. Furthermore, with the strongback, the maximum story and roof drift are insensitive to damper position and distribution, whereas, without it, the damper position significantly impacts the structural performance. The strongback's ability to protect against soft story vertical irregularities, regardless of their locations, and the insensitivity of structural performance to damper arrangement when utilizing a strongback, presents promising new options for structural design, architectural design, and remediation efforts.

Effects of Infill Panels with Various Configurations on the Non-Linear Dynamic Responses of Reinforced Concrete Structures

Abstract: This study presents the effects of including infill panels on the non-linear dynamic response of a hypothetical reinforced concrete frame when subjected to an earthquake. Infill panels are represented by equivalent diagonal struts using three different configurations, i.e., single, double with three different connection locations with the beams, and triple struts. The main goal is to determine the simplest and most appropriate representation of the infill panels by analogous struts. The effect of panel sizes on the non-linear dynamic response of the structure is also presented in this work. The main results showed that including infill panels in the analysis reduced the natural period, roof displacement, and story drift ratio, increasing the roof acceleration and shear forces at the structure base. Utilizing the triple model and the double strut joined at the midspan of the beams showed a good agreement with those using the complete infill model.

Research on seismic fragility of subway station based on incremental dynamic analysis method

Seismic intensity measure is an significant parameter that affects the accuracy of structural seismic risk assessment, and plays an important role in the performance-based earthquake engineering research framework. Taking a two story, three span, and shallow buried subway station as the research object, a two-dimensional finite element analysis model of soil structure underground in a typical engineering site was established using ANSYS. Ten earthquake records were selected from PEER as input, and the structural seismic fragility analysis method based on incremental dynamic analysis (IDA) method was introduced into the subway station structure. The maximum story drift angle was used as the structural damage index, and three typical seismic intensity measures were selected, the exploration is conducted on the seismic intensity measures applicable to shallow buried subway stations and the variation pattern of seismic response of subway stations with increasing seismic amplitude. The seismic fragility curve of shallow buried subway station structures is established to obtain the failure probability of the structure at different seismic intensity levels. The analysis results indicate that for shallow buried subway stations, PGA is the most suitable seismic intensity measure, and the comparison with existing empirical fragility curves shows that the vulnerability analysis method is feasible and can quantitatively provide the failure probability of structures at different performance levels, providing reference for seismic design of underground structures.

Seismic Assessment of High-Rise Buildings Having Transfer Elements

This paper investigates the seismic behavior of high-rise buildings having transfer elements. Three constructed reinforced concrete (RC) buildings having either transfer slabs or transfer girders were analyzed using the response spectrum (RS) and time-history (TH) methods. For each building, the story shear, bending moment, displacement, drift, and time period were obtained. Furthermore, pushover analysis (POA) method was conducted to evaluate the capability of these buildings to resist the expected seismic loads. Results of the studied buildings showed that, the base shears obtained using pushover analysis are ranging between 50% to 83% of those calculated using the static approach. In addition, the response modification factors (R) for these buildings were calculated to show their sensitivity due to the irregularity of buildings. For the studied cases in this research, the R values given in the building codes were overestimated for the cases with transfer slabs and underestimated for cases with transfer girders.

Seismic behavior of the brick masonry rural building strengthened with polypropylene grid cement mortar coating: Shaking table tests

Brick masonry structures are widely applied around the world, especially in Chinese rural areas, but their seismic performance is not satisfactory due to high brittleness of material and poor integrity of structure. Accordingly, a low-cost and highly efficient strengthening method for brick masonry structure is needed. This paper presents the shaking table tests for a 1/2-scale single-story brick masonry rural building strengthened with polypropylene grid cement mortar coating. The damage states of the test model under earthquake motions with different intensity were observed. The dynamic characteristics including natural frequency and damping ratio were discussed. The seismic response, such as acceleration, displacement, torsion angle, base shear and hysteretic energy dissipation, were analyzed. The results show that the weak areas of the test model were the corners of windows and door, the intersections between longitudinal wall and transverse wall and the top of longitudinal walls. With the input PGA of 1.0 g, the natural frequencies of the test model in the X and Y directions decreased to 93.1 % and 88.2 % of the initial values, respectively, the damping ratio in the X and Y directions increased to 2.56 and 1.61 times the initial values, respectively, and the maximum story drift and horizontal torsion angle were 1/122 and 0.0037 rad, respectively. The comparison between actual earthquake damage and test results showed that the use of polypropylene grid cement mortar coating to strengthen brick masonry rural building could result in good seismic behaviors.

Experimental study and mechanism analysis of out-of-plane seismic performance of reinforced concrete shear walls

Compared with the in-plane seismic performance, the out-of-plane seismic performance of reinforced concrete shear walls is weak and usually neglected, which leads to an inadequate study of the out-of-plane damage mechanism of shear walls and a lack of clear protective measures. In order to compare the similarities and differences in seismic performance of reinforced concrete shear walls when subjected to in-plane and out-of-plane loads in different directions and to clarify the key influencing factors, low cyclic loading tests were carried out on typical shear wall specimens in both in-plane and out-of-plane directions. The moment-curvature simulations of shear wall sections in both in-plane and out-of-plane directions are analyzed. The effects of parameters such as axial pressure ratio, wall thickness, height to width ratio and concrete grade on in-plane and out-of-plane seismic performance were analyzed at the member level in combination with finite element variable parameter analysis; at the structural system level, the time history analysis of 2 frame shear wall structures for single seismic action and main-aftershock sequence is established, and the structural damage is evaluated through the maximum story drift and rotation. The results reveal that the out-of-plane seismic performance of shear walls is significantly weaker than their in-plane seismic performance, with a difference of 1/20∼1/15 times in bearing capacity, where wall thickness and aspect ratio are the main parameters affecting in-plane and out-of-plane seismic performance; when the shear walls in the structure are subjected to seismic action in the out-of-plane direction, their out-of-plane direction will undergo large deformation and damage will occur easily, especially in the Single directional wall with less structure. The out-of-plane nonlinear analysis of the cross-section can be performed more accurately and quickly by using the new principal structure model proposed in this manuscript and some traditional principal structures. In the seismic design of shear walls, both in-plane and out-of-plane seismic performance should be ensured, and the wall thickness and height to width ratio of shear walls should be reasonably controlled.

A Comparative Study of the Seismic Behaviour of G+20 Storey Symmetrical Buildings Constructed with Light Weight Concrete and Normal Weight Concrete

Abstract: Concrete with a density of less than 2000 kg/m^3 is considered lightweight concrete. Structural lightweight concrete (SLWC) is used to reduce the dead load of concrete structures. The purpose of this research is to examine and compare the results of SLWC made with scoria and normal weight concrete (NWC) and normal and light weight concrete(NAL) multistorey buildings. Multistorey buildings are often constructed of ordinary concrete, steel, and other materials. They are subjected to heavy loads, requiring heavy construction that may not be cost-effective. In this paper, a G+20multistorey plan symmetrical building is analysed using the response spectrum method with SLWC and NWC. Bending moment, shear force, storey shear, storey drift, and storey displacement are considered. The results of the NWC and SLWC and NAL buildings are compared . Concluding the research work that when comparing symmetrical plan area cases of normal concrete, light weight concrete and combination of normal and light weight concrete for all the result parameters, light weight concrete seems to be very efficient and most favorable case. Hence should be recommended when this type of construction procedure will be adopted, i.e. always use building with lightweight concrete

Collapse performance of post-tensioned steel frames considering influence of infill walls

The aim of this paper is to study the effect of infill walls on load resisting behaviors of post-tensioned (PT) steel frames against collapse. Three planar PT steel frames are simulated using finite element (FE) method, one of which has no infill wall while the other two are installed with infill walls. The applied loads, lateral displacements, failure patterns, stress developments in infill walls, resisting mechanisms, as well as re-centering capabilities of three PT steel frames are studied and the role that infill walls play is discussed. Parametric analyses are conducted to investigate influences of magnitude of PT forces and critical material properties. Results indicate that infill walls work as compressive struts, significantly increasing initial stiffness, resistance and story drifts of PT steel frames, and play as energy dissipation devices during the collapse process. The existence of opening makes the stiffness distributed discontinuously throughout infill walls, greatly changing the failure pattern and increasing story drifts of PT frames. The resistances of infilled PT steel frames increase with increasing PT forces, bed joints strength and masonry unit strength in the initial stage. A design scheme is also developed to precisely predict the collapse resistance of infilled PT steel frame structures.

Seismic Behavior of Structures with Different Cantilever Projections in Different Zones

Abstract: This research paper focuses on studying how structures with different cantilever projections (1m, 1.25m, and 1.5m) behave during seismic events in different seismic zones. The analysis is conducted for both 5-story and 10-story buildings, following the guidelines provided in IS 1893 (Part 1):2016. The static method is used to assess various parameters, including story drift, frequency and time period in ETABS software. By examining these factors, we can better understand how these structures perform under seismic forces.

Seismic performance of steel structures with seesaw-twisting system using cylindrical steel slit damper

A previous study proposed a seesaw-twisting system (STS) that works in conjunction with a cylindrical steel slit damper (CSSD) by utilizing the torsion of the seesaw member. This study investigated the seismic performance of an STS using a three-story steel moment frame as a prototype building. The seismic response analyses focusing on a typical STS configuration were first performed. The peak inter story drift angles were examined under variations in the beam section, system stiffness and strength, and system specifications. An important characteristic of an STS is its ability to enable the use of long steel rods for bracing between the seesaw member and frame connections spanning multiple stories. Thus, additional frames with four distinct STS configurations were analyzed to examine the peak story drift angles and plastic hinge formation. The effect of the amplification factor on the seismic response of the frame with diverse configurations was discussed. The results showed that the STS with the CSSD efficiently reduced peak story drifts.

A Quantitative Method for Seismic Robustness of RC Frame Considering Resistance Vulnerability of Column and Storey Drift Ratios

The concept of seismic robustness is proposed by combining the concept of seismic performance and structural robustness. The existing qualitative, quantitative and evaluation methods of seismic robustness are all direct researched on the whole structure, and the influence mechanism of its internal components on the overall seismic robustness is still unclear. It is very important to establish a clear relationship between component design and structural seismic robustness for the structural design, reinforcement design and final evaluation of structural seismic robustness. Based on this, taking the column as the starting point, a quantitative method for the seismic robustness of RC frame by the seismic robustness index is proposed, which takes into account the resistance vulnerability of column and influence of column on the storey drift ratios (SDRs). In which, the resistance vulnerability is represented by the defined control vulnerability coefficient Pimax, and the influence on the SDRs are represented by the storey drift ratio importance coefficients (SDRCs) λ. The method not only reflects the essential mechanical properties of the column, but also reflects the effects brought about by different SALs. The feasibility of the method is demonstrated by numerical examples of two types of failures (assuming single column and two columns failure), and four optimization design proposals are proposed for it. The analysis shows that λ of the target columns to the floor where the target columns located are obviously greater than those on the remaining floors of the target frame. The seismic robustness index R decreases sharply with the increase of the seismic action level (SAL). R is different compare single column failure with two columns failure under 4 SALs. The most effective way to improve the R of the frame under a certain SAL is to retrofit its control column.

Seismic performance of glulam frame with friction damper and column shoe: Experimental investigation and simplified numerical model

Resilient timber structure is a new branch of structure design. To reduce seismic damage of timber structures, an innovative resilient glulam frame (IRF) with friction dampers and column shoes was proposed in this paper. The IRF was connected by use of beam-to-column joints with friction dampers and column-base joints with column shoes. An IRF specimen and a conventional glulam frame (CF) specimen, with a scale ratio of 1:2, were tested under reversed cyclic load. The failure modes, hysteretic curves, stiffness degradation, and energy dissipation capacity of the specimens were obtained. Results indicated that the IRF was low-damage except replaceable Shape Memory Alloy (SMA) strips tensile failure. The load-carrying capacity of IRF did not significantly change compared to the CF specimen, but the energy dissipation capacity was enhanced by approximately 100%. A simplified numerical model of timber frames was developed and validated, and then the time-history analysis of multi-story IRF structure was performed. It was further demonstrated that the adoption of IRF significantly reduced the maximum story drift and residual drift of structures, especially during severe earthquakes.

Beam-to-column connection with double-stage yield buckling-restrained steel bar dampers

In this study, double-stage yield buckling-restrained steel bar dampers (DY-BRBDs) were applied at the beam-column joint, where the DY-BRBDs mainly consist of buckling-restrained steel bar dampers (BRBDs) and BRBDs with gaps (Gap-BRBDs) in parallel. First, a theoretical analysis of the mechanical properties of DY-BRBDs was performed. Cyclic loading tests were then conducted on the beam–column joints with the DY-BRBDs. The test results indicated that the DY-BRBDs exhibited stable hysteresis performance and double-stage yield characteristics. Numerical analysis models were created to simulate the hysteretic behavior of the connection. The theoretical values and simulation results were compared with the test results to verify the accuracy of the theoretical analysis and numerical model. Finally, pushover and seismic analyses were conducted on a 10-story steel frame structure equipped with DY-BRBDs, and the seismic performance of the frames with DY-BRBDs was compared with that of a frame with single-stage yield buckling-restrained steel bar dampers. The analysis results indicated that the DY-BRBDs could effectively reduce the story drift and residual drift of the structure and improve the deformation uniformity of the steel frame along the height.

Experimental study on seismic behavior of high strength steel flange-plate connections with box columns

The flange-plate beam-to-column connections are a promising option for reinforced moment-resisting connections in ductile steel frames and have potential applicability in high strength steel frames. However, there have been few investigations on flange-plate connections with high strength steel box columns. In this study, experiments were conducted to evaluate the seismic behavior of high strength steel flange-plate connections with box columns. Seven specimens were designed and tested under anti-symmetrical cyclic loads, comprising three different combinations of Q355 or Q460 steel beams and Q460 or Q690 steel columns. While the expected beam failure mode was observed in five specimens, two specimens experienced ESW joints failure, and one specimen experienced CJP weld failure. These findings highlight the possible impact of welding quality defects in engineering applications. The test results about bearing capacity, rotation stiffness, deformation capacity, and energy dissipation were reported and analyzed. Under the similar design conditions, the use of higher strength steel members results in a decrease in the initial stiffness of the specimens, as well as changes in yielding modes, deformation proportion, and energy dissipation capacity. Six flange-plate connections met the deformation and bearing capacity requirements for special moment frames in AISC 341 with the ultimate story drift angle not less than 0.06 rad. The proposed criteria for determining the minimum size of flange plates was verified in this study, and design recommendations were made for flange-plate connections in high strength steel frames.

A Comparative Study of the Seismic Response of Different Concrete Slab Systems for a Multistory Building in Madinah

Seismic analysis is considered as an important aspect of the design of high-rise buildings, particularly in earthquake prone areas. The structural system choice can have a considerable impact on the building seismic response. The goal of this study is to compare the seismic behavior of multiple slab systems used in a multi-story building in Saudi Arabia's Madinah region. This study's goal is to determine the most effective and efficient slab system performance in a seismic zone. The ETABS V20.3 program was used in this work to model and assess the seismic response of three different types of slab systems: flat, solid, and hollow blocks slab types. Many earthquake aspects, including story displacement, base shear, story drifts, column forces, and bending moments, are estimated for each system. The study examines and assesses each system's seismic response, and the conclusions are given and discussed. According to the findings, the choice of slab system has a considerable impact on the seismic reaction of the building. The hollow block system has the least base shear value and bending moments, while the flat slab system has the greatest. The values in the solid slab system are in the middle. In terms of story displacement and column forces, the study additionally indicates that the hollow block type system performs effectively in terms of story drifts, however, the solid slab system outperforms the others. The study's findings can assist designers and engineers to determine the best slab system for multistory buildings in seismic-prone areas by providing important insight and suggestions.

Seismic behavior analysis and energy-based design of SSTFs with multiple Vierendeel panels

This work presents an energy-based plastic design method for steel staggered truss framing (SSTF) structures with multiple Vierendeel panels. The effectiveness of the method was investigated and the improved seismic performance of plastically designed SSTF structures was verified. First, parameter analysis based on a refined finite element analysis model of steel trusses with multiple Vierendeel panels was conducted. The plastic bending resistance ratio of the chord member to the intermediate vertical member was recommended based on evaluating the failure modes. Then, the energy-based plastic design procedure for the SSTF structure with multiple Vierendeel panels were described step by step. Finally, three SSTF structures were comparatively analyzed by pushover analysis and nonlinear time-history analysis, including a force-based designed SSTF structure with single Vierendeel panels, a plastically designed SSTF structure with single Vierendeel panels, and a plastically designed SSTF structure with multiple Vierendeel panels. Compared with the forced-based designed structure, the plastically designed structures showed slightly lower load-carrying capacities, but much higher ductility. The force-based designed structure had obvious soft stories, while the two plastically designed structures showed more uniform story drift distributions and formed a controllable failure mode. Compared with the structures with single Vierendeel panels, the rotation demand on the chord members of SSTF structures with multiple Vierendeel panels was significantly reduced.

Linear and Nonlinear Dynamic Analysis of Reinforced Concrete Building with V Shape Steel Bracing

In this study, the RC-MRCBFs were used with V braced frame. The core objective of this examination is to understand the earthquake behavior of the RC-MRCBFs in steel V braced frames. Response spectrum analysis (RSA) is used to understand the seismic performance of the steel braced and un-braced RC frames. Total 12 steel braced RC frames and 12 un-braced frames for all 4 story, 8story, 12 stories and 16 stories are studied and observed the seismic parameter such as fundamental time period (FTP), top story displacements, inter-story drift, base shear and story stiffness of the structures. After studying the parametric study of the 4 to 16 story buildings with a linear and nonlinear analysis tool it was observed that to get the effective braced frame with expected failure mechanism, ductility, the columns should be designed such that, they resist at least 50% base shear contributions. It is observed that using the steel V bracing in the low rise to mid-rise buildings, improves the seismic behaviors of the structures. The steel bracing reduces the maximum top story displacements, drift and time period of the building and increases the seismic base shear demand, stiffness of the structures. The result shows that as increasing the base shear contribution in the columns, the drift and displacement of the story increases and base shear decreases. Key Words: Response Spectrum Analysis, displacement, Maximum storey drift, Storey shear, Storey stiffness, braced frame, RC buildings.

Comparative Study of Linear Static Analysis of G+10 Storey Building with and Without Shear Wall in ETABS

Planning, designing, and execution of high-raise building while taking into account the impact of lateral loads such as wind and seismic loads computation with or without shear wall technology in conventional mode is a crucial task for civil engineers. The lateral loads develop high lateral stresses and sway movement in structural members and need adequate stiffness to resist lateral forces along with sufficient strength against vertical gravity loads. In this case, civil engineers establish an effective system for construction of high raise building with the usage of shear wall system is high in-plane stiffness and torsional resistance. Present the authors are considered a G+10 storey commercial shopping mall with a central cut-out at Bhimavaram location which lies in seismic zone III as, per IS 1893(part 1): 2016. The load cases from IS 875 Part I (dead loads), Part II (imposed loads), and Part III (wind loads) are used to create the load combinations in accordance with IS 456: 2000. Two models, with and without shear wall system are taken for comparing the parameters like storey drift, storey displacement, stiffness, shear force, base shear, bending moment and center of rigidity by performing linear static seismic analysis and wind analysis for both models in ETABS software. The simulations concluded that Shear wall system is the efficient and economical way of resisting lateral loads in high rise or multistory buildings.