Story Drift Ratio Research Articles

A Comparative Study on Seismic Behaviour of Plan Irregular Buildings

Abstract: Asymmetrical plan irregularities occur when the horizontal layout of a building is non uniform or unsymmetrical in one or more axes. These irregularities may arise from variations in building shape, size, or configuration, leading to nonuniform distribution of mass, stiffness, or load paths throughout the structure. Considering equivalent static analysis (ESA) and response spectrum analysis (RSA) as per IS 1893-Part 1 (2016) considering seismic zones III, structure with square shaped plan performs better than the other shaped models (viz. T, L, H and Plus shapes) with least values of storey displacement and storey drift ratio, and also with higher value of storey stiffness. Thus, square plan shaped structure is seismically more resistant than T, L, H and Plus shaped structures.

Seismic response control of shear frame structure using a novel tuned-mass type composite column

Concrete filled steel tube (CFST) column is widely applied in shear frame structure in seismic-prone area owing to its superior earthquake resistant performance. However, CFST column might still suffer damage under a severe earthquake. This paper proposes a novel tuned-mass type column-in-column (CIC) system to improve the seismic behavior of the CFST column and hence protect the structure. The CIC system is formed by splitting the CFST column into a primary column and a secondary column, while the overall cross section area and hence the load-bearing capacity is not changed. By optimally selecting the springs and dashpots to interconnect the two columns, the CIC can act as a non-conventional tuned mass damper (TMD) to reduce seismic vibrations of structures. To demonstrate the proposed CIC concept, a single-story and a five-story frame structure with and without control are designed. Nonlinear time history analyses are performed to study the seismic responses of these structures considering different seismic design levels, earthquake ground motions and CIC control schemes. Numerical results show that the CIC system can effectively reduce the seismic induced story acceleration, displacement and drift ratio of frame structures with the reduction ratios approximately between 21 % and 30 %, and the ratios on reducing the base shear force and bending moment are between 27 % and 31 %, and between 34 % and 49 %, respectively. The proposed CIC control concept is a new solution for mitigations of seismic responses of CFST frame structures.

An Empirical Spatiotemporal Input Model for Regional Seismic Ground Motions

The development of the economy and technology has attracted greater attention to regional seismic resistance, a key technology for which is the simulation of regional seismic ground motions. This study proposes a simple and highly operable method for the generation of regional seismic ground motions, which includes five steps. First, a seismic ground motion recorded at a seismic station is selected as the original ground motion. The original ground motion is then decomposed into eight sub-signals by wavelet packet transform (WPT). Next, the eight sub-signals are adjusted by the frequency attenuation model. The generated ground motion is then amplitude modulated by the peak ground acceleration (PGA) attenuation model. The frequency attenuation model and the PGA attenuation model are obtained by fitting seismic data from the 1999 Chi-Chi earthquake. Finally, the propagation of the ground motion is considered. The proposed method can provide a time history of seismic ground motions for any point in a region. To investigate the rationality and applicability of the proposed method, the characteristics of the generated seismic ground motions are compared with those of true seismic ground motions. The average error of the PGA of the generated ground motions and the true ground motions is 0.072[Formula: see text][Formula: see text]; thus, the proposed method is suitable for use in small-scale regions. Furthermore, 4-story and 15-story structures are used for structural response analysis. The story drift ratio error between the generated ground and true ground motions is found to be within an acceptable error range. The proposed method provides a new way to generate ground motions for regional seismic investigation.

A Comparative Study Between Conventional Outrigger System and Hybrid Outrigger System considering Performance Index Criterion

Outriggers are regarded as a structural component which can effectively lessen the reactions generated by lateral loads in tall buildings. Depending on the connectivity between the core and the peripheral columns, the outrigger system can be divided into virtual outrigger system and conventional outrigger system (COS). The hybrid outrigger system (HOS) has one conventional outrigger and one virtual outrigger at two distinct floor levels. This study gives a comparison of optimal position and performance between COS and HOS based on formulated performance index criterion (PIC) for building heights of 140, 210, 280 and 350 m by considering variations in stiffness of the outrigger belt wall and beam, the stiffness of the building's core, the height of the structure and the length of the outrigger arm under static wind and equivalent static earthquake load. The outrigger behaviour assessed using PIC takes into account the combined response of displacement at top, absolute maximum inter storey drift ratio and acceleration response at the roof. Based on PIC, performance of both COS and HOS at their evaluated optimal position are compared, and is found that HOS are less effective than COS. Therefore, to enhance the performance of HOS to be in par with COS, an optimization study is performed by increasing the axial stiffness of column, stiffness of outrigger, and stiffness of slab while maintaining the increase in total concrete volume of the structure a minimum. From the findings, PIC values of HOS (PICHOS) for 40 to 100 storeys exhibits an increase of 10 to 1.1, 20.2 to 2.2 and 12.5 to 1.9% for variation in core thickness, length of outrigger arm, and outrigger thickness, respectively, compared to PIC values of COS (PICCOS). For PICHOS to be comparable with PICCOS, increase in the total concrete volume of HOS reduces from 1.4–16.5 to 0.6–2.5% as the model's height increases from 40 to 100 storeys, respectively, suggesting that the HOS with marginal increase in total concrete volume can perform effectively for taller structures.

Design procedure of a shear fuse system for steel moment-resisting frames

In steel moment-resisting frames (MRFs), seismic energy is generally dissipated through the formation of flexural plastic hinges at beam ends. In ensuring such a mechanism, current code provisions limit the utilization of beams with small span-to-length ratios in MRFs. This study presents the design procedure of a novel shear fuse system that integrates replaceable shear links with non-prismatic beams to enhance the performance and repairability of MRFs with small beam span-to-length ratios. The proposed design strategically weakens the beam at its midspan by incorporating a replaceable link, prioritizing shear yielding in the link over flexural yielding in the beam outside the link, thus ensuring adequate frame ductility and protecting the critical beam-to-column connections. It can function as an efficient replaceable shear fuse system, as the damaged fuse can be substituted with a new one following a severe earthquake. In fulfilling the study’s purpose, first, several formulas are developed to provide a comprehensive design procedure. Next, example design calculations are presented for an MRF with a small beam span-to-depth ratio. Ultimately, a numerical investigation is provided to examine the proposed system’s performance compared to conventional MRFs. The results indicate that the proposed shear fuse system provides a more consistent cyclic behavior than the conventional prismatic beam design, exhibiting stable strain-hardening behavior up to the 5 % story drift ratio without noticeable strength degradation. It appropriately shifts the plastic hinges away from the beam-to-column connections while increasing the frame’s overall ductility with 1.14 times greater energy dissipation in the final loading cycles.

Experimental study on seismic performance of stainless steel full-scale frames: Global response

This paper presents an experimental study of the seismic performance of austenitic stainless steel full-scale frames using the pseudo-static test method. The bottom single-span, two-storey substructure of the designed prototype frame was chosen as the test frame. Two full-scale frames were tested, one with a bolt-welded joint and the other with an extended end-plate joint. This paper is the first of two accompanying papers to this experimental study and focuses on the specimen design, testing details and global response of the stainless steel frame under cyclic loading. The test results were utilized to analyse the global response of the frames, encompassing failure mode, bearing capacity, deformation capacity, energy dissipation capacity, the overstrength factor, ductility factor and seismic response modification factor. The experimental findings suggest that the stainless steel frames with two joint types demonstrate consistent ability to dissipate energy during cyclic loading. The structure also performs well in terms of deformation, with uniform inter-storey deformation and no soft-storey detected. The maximum storey drift ratio of the frame is 7%. Prior to reaching a storey drift ratio of 2%, the frames with both joint types exhibit similar cumulative plastic deformation, stiffness degradation, and cumulative energy dissipation.

Shaking table test on seismic performance of a large-span high-rise building

This paper describes investigations in respect of the seismic performance of a large-span high-rise building in a mountainous area. The building consists of a 135 m high shear wall structure and a 174.5 m long steel truss structure, with dampers used to enhance the seismic performance. A 1/40 scale model of the prototype structure was designed, and shaking table tests was conducted. The experiments simulated the wave passage effect and slope amplification effect based on the building site and structural characteristics of the prototype structure. The seismic performance of the prototype structure was analyzed through the damage phenomenon, dynamic characteristics, and dynamic response of the model under earthquake effects. The results show that three seismic waves were delayed by about 0.4 s and amplified by about 1.6 times after passing through the steel frame with viscous dampers, which could effectively simulate the wave passage effect and slope amplification effect in the test. The maximum story drift ratios of the model shear wall structure and steel truss structure were 1/1258 and 1/455 for the SLE and 1/568 and 1/185 for the MCE. The damping devices played a key role in energy dissipation. As a result, this research provides a reference for the seismic design and shaking table testing of large-span high-rise buildings.

Study on the influence of base shear distribution on the seismic response of base-isolated split-foundation structures

ABSTRACT Split-foundation structures with base isolation have multiple isolation layers due to their uneven foundation heights. This complexity adds challenges to the seismic isolation design of split-foundation structures. In this paper, two special parameters, namely the shear non-uniformity factor Φ and the ratio of shear non-uniformity factor Γ, were proposed. Response spectrum analysis and time history analysis on base-isolated split-foundation structures with varying Φ and Γ were conducted to investigate their seismic response and damping effect. The results indicate that Φ primarily affects the seismic response in the lower stories and the upper embedding story. When Φ is too small or too large, it results in an uneven isolation effect. Moreover, when the base shear ratio β z exceeds 0.5, the distribution of plastic hinges is significantly affected by the variations in Φ. Additionally, the story shear and story drift ratio of lower stories in the along-slope direction are generally greater than that of the corresponding story of the non-isolated structure. Therefore, in the seismic isolation design of the split-foundation structure, the base shear at different embedding ends should be reasonably assigned. Special attention should also be given to the adverse effects in the along-slope direction.

Real-time displacement monitoring using camera video records with camera motion correction

Structure from Motion (SfM) method can reconstruct the story drift ratio, but the camera motion produced by earthquakes reduces the measuring accuracy. This paper improves the applicability of the traditional method by correcting camera motion according to the identification of translation and rotation of camera. Experiments at different levels are designed to prove the proposed method. First, one set of experiments proves the motion correction method by the Single-degree-of-freedom (SDOF) system.The error of maximum response is 4.5% for the case with less rotation. As for the camera motion with larger rotation, the average error increases to 7.9%, which still meets the practical utilization. After that, the accuracy of using SfM method is confirmed by the Multi-degree-of-freedom (MDOF) system with the average error of 4.9%. This paper is expected to extend approaches for the application of the SfM method in the case of huge earthquakes.

Proposal for a novel technological damper system (TDS) for the retrofit of reinforced concrete frame structures

Considering the severe earthquakes that have occurred worldwide, it has been observed that even buildings which are constructed in compliance with the seismic regulations, have suffered heavy damage or collapsed. Similarly, in earthquake on February 6, 2023, in Kahramanmaraş, Turkey, many old and new structures were damaged or even collapsed. This situation has compelled researchers to focus on the most current and technological applications for earthquake protection. In the latest research topics, there has been a growing emphasis on the impact of new technological systems targeted at improving the seismic performance of structures constructed with reinforced concrete systems, given the notable occurrence of collapsed buildings with such structural systems in this earthquake. In this study, the developed Technological Damper System (TDS) was employed to enhance the earthquake performance of reinforced concrete structures. TDS is a versatile and adjustable friction-type damper. For this reason, two identical ½ scaled reinforced concrete frames were fabricated for the study, one representing a traditional structure as a reference frame (REF), and the other a frame with the TDS device. After applying quasi-static cyclic tests to the frames, the force-displacement, and force-rotation relationships, as well as energy dissipation capacities were determined for both frames. In addition, the damage conditions of the columns during the tests were assessed based on the plastic rotation limit conditions outlined in Turkish Building Earthquake Code (TBEC 2018). As a result, the frame retrofitted with the TDS device exhibited a significant increase in horizontal load-carrying capacity, ranging from 42.04% to 75%, when compared to the REF. Additionally, it was observed that energy consumption increased between 85% and 220%. The REF reached significant damage levels at 1% and 2% story drift ratios and an advanced damage state at about 3%, in accordance with TBEC 2018. Finally, the behavior of the frame retrofitted with TDS considerably improved according to REF and it reached a significant damage state at 3% story drift ratio.

Seismic Performance Assessment of Composite Frame–High-Strength Steel Plate Wall Core Tube Resilient Structural System

Against the backdrop of China’s continuous promotion of green and low-carbon transformation and the development of construction industrialization, high-strength composite structural systems have significant development prospects. However, their research and application in the field of construction are insufficient. In response to this issue, the study proposes a new high-performance structural system, namely the composite frame–high-strength steel plate wall core tube resilient structural system, which includes a core tube composed of double steel plate concrete composite shear walls and replaceable energy dissipation coupling beams, as well as composite frames. The highest strength grades of the steel plate and concrete used in the composite walls of the core tube are Q550 and C100, respectively. Using a 200 m building as an example, this study designs and establishes models for this high-performance structure and a conventional reinforced concrete frame–core tube structure. Subsequently, the dynamic elastoplastic time history analysis and seismic resilience assessment of structures are conducted under design basis earthquakes (DBEs), maximum considered earthquakes (MCEs), and extremely rare earthquakes (EREs). Research has shown that, compared to conventional structures, the thickness of shear walls of new high-performance structures can be effectively reduced, which helps decrease the self-weight of the structure and improve the available space in buildings. Additionally, high-performance structures exhibit a better performance in controlling the story drift ratio, lower plastic damage and overall stiffness degradation of the structure, and better seismic performance. The seismic resilience of the high-performance structure has been significantly enhanced, especially in terms of minimizing casualties, thereby better ensuring the safety of people’s lives and property.

Uniform deformation distribution of structures at different seismic hazard levels using endurance time method

This paper evaluates the application of the endurance time method in the optimum performance design of structures using the uniform deformation theory. The structures used in this study include shear-building systems with 5, 10, and 15 stories, and steel moment-resisting frames with 3, 7, and 12 stories. Initially, shear-building systems are optimized to have uniform story ductility ratios at low, moderate and high seismic hazard levels separately using three sets of ground motion records and a compatible series of endurance time acceleration functions. The effectiveness and accuracy of the endurance time method are assessed by comparing lateral force distribution obtained from this method with its corresponding attained from ground motion records. Moreover, as the number of stories and target ductility increases, the compatibility of these two methods improves. However, it is found that the optimum structure at one seismic hazard level does not necessarily lead to the optimum structure at other seismic hazard levels. Next, by adding dampers with gap to the systems, a procedure is suggested to optimize these structures at different seismic hazard levels simultaneously. These dampers are activated at moderate and high seismic hazard levels. Finally, similar optimization algorithm is used for steel moment-resisting frames to make their story drift ratios or plastic hinge rotations uniform along the height at different seismic hazard levels. Results show that combining endurance time method and uniform deformation theory leads to a promising optimization procedure that can significantly reduce computational costs with reasonable error.

Seismic Evaluation of Retrofitting Technique Using Bracing Systems for Steel Multi-Story Building

A bracing system is the one of effective retrofitting methods for existing high buildings to support the lateral loads. Structural bracings increase the stiffness and stability of the building and the energy dissipation capacity. In this research, the numerical study of retrofitting a multi-story steel building near Imam Ali Holy Shrine in Najaf, Iraq has been conducted. The retrofitting mechanism includes a test of four different bracing systems such as X-bracing, V-bracing, Diagonal-bracing and IV-bracing located in the x and y-axis of the model. The seismic analysis using the elastic response spectrum method was performed for two types of earthquakes, weak and strong. The comparison among different parameters is discussed such as maximum lateral displacement, story drift ratio and base shear values. The seismic load was applied in two axes of the building model simultaneously and the results of the parameters in the x and y-axis were extracted. The results show that the retrofitting using four bracing system types increases the capacity of energy dissipation of the existing building model to seismic load by reducing the maximum lateral displacement in the x-axis by 55%, 44%, 41%, and 30% for X, IV, V and Diagonal-bracing, respectively. However, the X-bracing has a significant increase of the shear base value of the model by 39% and 49% in the x and y-axis, respectively, which means cost-effective compared with the other bracing types. Therefore, the IV-bracing type has an appropriate effect on the strength of the building against seismic load with reasonable cost-effectiveness.

The Assessment of Structural Damages by Potential M<sub>L</sub> 7.0 Changhua Earthquake in Taiwan Using Hybrid Simulation Method, Modal Analysis and Story Drift Ratio

The Assessment of Structural Damages by Potential M<sub>L</sub> 7.0 Changhua Earthquake in Taiwan Using Hybrid Simulation Method, Modal Analysis and Story Drift Ratio

Shaking table test of a timber building equipped with a novel cost-effective, impact-resilient seismic isolation system

In most cases, construction of Light Frame Timber Buildings (LFTBs) in areas of high seismic hazard requires strong wood frame shear walls and continuous rod systems, which increases the cost of LFTBs. Frictional seismic isolation might be applied to protect LFTBs against extreme ground motions and mitigate the cost of continuous rod systems. However, there are no experimental studies on the response of LFTBs equipped with frictional isolation and subjected to extreme seismic ground motions that might cause impacts between the slider and the perimetral ring or between the isolated base and the perimetral moat wall.This study explores the potential of using impact-resilient frictional isolators as a feasible solution to alleviate stiffening and overturning costs of LFTBs while making them resilient to impacts in case of extreme events. This issue has been researched by evaluating the response of a 1:2 scaled 3-story LFTB isolated with a novel Impact Resilient Double Concave Frictional Pendulum recently developed by the authors. The specimen was subjected to a suite of shaking table tests (white noise, harmonics signals, and seismic records), including strong ground motions such as the Concepcion record (2010 Maule, Chile earthquake, Mw = 8.8) scaled to 130 %. Results indicate that despite being subjected to extreme excitations, peak acceleration ratios (i.e., the ratio of peak floor acceleration to peak ground acceleration) did not exceed 0.75, and story drift ratios were smaller than 0.52 % in most cases. Thus, the superstructure remained in the elastic range without damage. The study demonstrates the potential of achieving effective seismic protection of LFTBs using Impact Resilient devices. In addition, this paper presents a numerical model developed with experimental data, which provides insight into modeling issues such as, for instance, damping properties.

Seismic Performance Evaluation and Comparative Study of Reinforced Concrete Building on a Sloped Terrain with Regular Building by Considering the Effect of URM Infill Walls

This paper focuses on the seismic vulnerabilities of multi-storey buildings in hilly regions like Sikkim and Uttarakhand, where rapid construction is driven by population growth and tourism. The study particularly evaluates step-back buildings on hilly slopes, comparing their vulnerability to standard buildings on flat terrain. Using non-linear analysis to assess structural aspects like displacement and storey drift ratio, the research examines the performance of these buildings in both uphill and downhill orientations against typical three-storey and six-storey structures, respectively. The findings indicate that step-back buildings, especially those without infill walls, are more susceptible to seismic damage. For instance, on the uphill side, a step-back building shows a mean drift ratio 15.11% greater in the X direction and 4.57% greater in the Y direction compared to a three-storey regular building (3SR). This vulnerability is exacerbated when infill walls are absent, with mean drift ratios in step-back buildings being 74.75% and 33% higher in the X and Y directions, respectively. Moreover, at a seismic acceleration of 0.36 g, the mean displacement of a step-back building is 83% greater in the X direction and 51% greater in the Y direction than those with infill walls (SBIN), underscoring the significant role of infill walls in enhancing earthquake resilience. The study also highlights that short columns in step-back buildings are particularly prone to severe damage, especially just above the uppermost foundation level. While infill walls offer substantial mitigation of damage at the Design Basis Earthquake (DBE) level, at the Maximum Considered Earthquake (MCE) level, step-back buildings still endure severe damage compared to regular buildings with infill walls. Consequently, the research establishes that step-back buildings demonstrate greater vulnerability at DBE levels without infill walls and are more susceptible to damage than flat terrain buildings at MCE levels, emphasizing the need for careful design and reinforcement strategies in earthquake-prone hilly areas.

Seismic performance of self-centring connections with two energy dissipation stages for reusable modular steel buildings

This paper presented a feasibility study on a self-centring connection with two energy dissipation stages for use as a combined inter-module and intra-module connection in reusable modular steel buildings. The proposed connection was equipped with shape memory alloy (SMA) disc washers and friction dampers, the former for self-centring and the latter for energy-dissipation functions. The design concept of two energy dissipation stages was to achieve structural longevity and member reuse by 1) enabling rapid recovery after small and medium earthquakes, and 2) facilitating prompt repair if at all needed after large earthquakes. A spring analytical model was proposed, wherein each connection component was symbolised as a rotational spring. Based on the model, a design methodology to meet the two-stage performance goals was derived, where the critical story drift ratio between the two stages was expressed as a function of the properties of friction dampers and SMA disc washers. Detailed finite element simulations were used to validate the proposed design concept and the spring model and to assess the influence of the friction dampers and SMA disc washers on the hysteresis behaviour of the connection. The results demonstrated that the proposed connection would facilitate the design objectives when designed based on the proposed spring model to ensure structural longevity, member reuse, and efficient recovery and repair after seismic events.

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.

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.