Seismic Response Of Buildings Research Articles

City-scale buildings damage estimation based on broadband physics-based ground motion simulation of 2021 Ms 6.4 Yangbi, China, earthquake

This article proposed a computational workflow for city-scale building damage estimation based on broadband physics-based ground motion simulation. The dynamic stiffness matrix method in frequency-wavenumber domain is employed for broadband physics-based ground motion simulation of finite fault along with site response correction using equivalent-linear site response analysis approach. With simulated ground motion, seismic response of buildings, using multi-degree of freedom model, is simulated using nonlinear time history analysis, and building damage is evaluated based on a trilinear backbone curve of story’s nonlinear force-drift model. Main advantage of the framework lies in the employed dynamic stiffness matrix method for ground motion simulation, which can efficiently generate broadband ground motions in perfect parallel and naturally capture the physics of finite fault source, propagation path, and spatial variability characteristics of ground motion. To demonstrate the salient features of proposed workflow, the 2021 Ms 6.4 Yangbi earthquake is simulated with frequency resolution up to 20 Hz, and seismic damage of buildings in Yangbi county are estimated. Results show that most traditional wood-adobe structures suffer moderate to severe damage, and engineered seismic buildings (mostly RC frame) in Yangbi county suffer minor damage, which agrees with field investigation results.

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 Response of RC Frame Buildings: Theoretical Formulation and Modeling with Soil-Structure Interaction Analysis

"Seismic Response of RC Frame Buildings: Theoretical Formulation and Modeling with Soil- Structure Interaction Analysis," offers a comprehensive exploration of the seismic response of reinforced concrete (RC) framed structures, with particular emphasis on soil flexibility. Through a meticulous response spectrum analysis, the study delves into the influence of soil flexibility on buildings of varying heights, ranging from five to nine storeys, considering both fixed and flexible support conditions across diverse soil types. The research draws the following significant conclusions: Significance of Soil-Structure Interaction (SSI): Incorporating soil-structure interaction (SSI) into the analysis leads to a noteworthy extension of the natural time period of the structure. This parameter stands as a linchpin in grasping the lateral response of framed structures, underlining its pivotal role in the precision of seismic design calculations. Soil Flexibility and Amplified Base Shear: Enhanced soil flexibility is found to correlate with a proportional increase in base shear. This phenomenon is most pronounced in soft soil conditions, where base shear experiences substantial escalation, particularly in taller buildings. Roof Displacement as a Performance Indicator: Roof displacement, a crucial indicator of structural performance, exhibits an upward trajectory owing to the cumulative effects of SSI. Notably, soft soils manifest higher roof displacements, with these variations becoming more pronounced as the building's height increases. The insights garnered from this analysis underscore the profound influence of SSI on a building's seismic response. Furthermore, the study highlights that advancements in finite element methods (FEM) and computer technology have significantly facilitated the integration of SSI into structural analysis. Therefore, it is imperative to harness these advancements fully to enhance our comprehension of structural behavior and to promote the adoption of secure construction practices in seismic-prone regions.

Backbone curve variations on steel building seismic response

A 4-story steel moment-frame building designed according to ASCE 7 was used in a numerical parameter study to assess the effects of modeling features on peak drift demands. Features studied included strength, stiffness, ductility, and degradation along with several hysteretic models. Attention was given to ASCE 41-type backbone curves. Of particular interest was exploring the effects of degradation, in which an adaptive backbone curve was used to capture both in-cycle and cyclic degradations. Incremental dynamic analyses (IDAs) were performed using a suite of earthquake records to assess the response over a range of shaking intensities. It was found that in-cycle degradation had more influence on the response compared to cyclic degradation for the set of ground motion records that were employed. Moreover, use of the monotonic backbone alone, with its in-cycle degradation, was sufficient. In addition, it was found that increasing strength, stiffness, and/or ductility resulted in decreased peak drift demands, whereas modifying the hysteretic type (elasto-plastic, stiffness-degrading, and pinching) had little effect on peak drifts. These findings indicate that using backbone curves based on envelopes of first-cycle test data, as done in ASCE 41, can result in overly conservative seismic response predictions.

Seismic Performance of Vertical Irregular Steel Frame Structure under Mainshock-Aftershock

Abstract: The majority of the structures are involved with architectural importance and it is highly impossible to achieve uniform structural properties in all directions. Hence earthquake resistant design codes considered it as irregular frames based on relative difference in the story properties. In many cases these irregularities are responsible for structural collapse of buildings under earthquake ground motions. The seismic response of buildings with irregular distribution of stiffness along the height may be differentfrom that ofregular building. Also, past earthquakes showed that structure may be subjected to sequence of ground motions but current codes do not have guidelines for such cases. It is considered that aftershock do not cause any more damage to damaged structure by the preceding mainshock ground motion. In this study steel moment resisting frame buildings are evaluated to understand the seismic response of vertical stiffness irregular frames subjected to mainshock-aftershock ground motions. The 9-story steel moment resisting frame building situated in Los Angeles is used in this study was originally developed as part of the SAC steel project. In this study soft and stiff storey case was considered at three different locations along the height, i.e., at bottom storey, mid-height storey and top storey. The single modification factor is used for irregularity. For comparison purpose dynamic properties of regular and irregular frames are kept same. Two sets of 6 records were selected representing a seismic hazard level of 2% and 10% probability of exceedance in 50 years respectively as mainshock. Two sets of 30 mainshockaftershock ground motion are considered for the study. These ground motions were developed using randomized approach. A non-linear time history analysis of regular and irregular building is carried out separately under mainshock and mainshockaftershock. The effect of building irregularity was studied for single storey modification at bottom storey, mid-storey and top storey with comparison to regular building. The comparison of a regular and irregular building is carried out in terms of maximum roof displacement and interstorey drift ratio. Also, comparison of frames under mainshock and mainshock-aftershock is done.

Numerical studies on the seismic response of a three-storey low-damage steel framed structure incorporating seismic friction connections

A 9 m high, near full scale three-storey configurable steel frame composite floor building incorporating friction-based connections is to be tested using two linked bi-directional shake tables at the International joint research Laboratory of Earthquake Engineering (ILEE) facilities, Shanghai, China, as part of the RObust BUilding SysTem (ROBUST) project. A total of nine structural configurations are designed and detailed. To have a better understanding of the expected system behaviour, as well as effects of other structural and non-structural elements (NSEs) on the overall system response, experimental testing at component level has been conducted prior to the shake table testing. This paper presents an introduction to the ROBUST project, followed by a numerical study on one of the nine configurations of the structure, having Moment Resisting Steel Frame (MRSF) in the longitudinal direction and Concentrically Braced Frame (CBF) in the transverse direction. Hysteretic properties employed in the numerical models are validated against component test results. The predictions of the building's seismic response under selected base excitations are presented indicating the likely low damage performance of the structure.

Effect of a symmetric V‐shaped canyon on the seismic response of an adjacent building under oblique incident SH waves

AbstractTo elucidate whether an irregular topography affects the seismic response of nearby structures, an analytical solution to the dynamic interaction between a symmetric V‐shaped canyon and an adjacent building under the incidence of SH waves is proposed by using the wave function expansion method. The dynamic canyon‐soil‐structure interaction is decomposed into two problems of scattering and radiation. The building is idealized as a shear wall supported by a semicircular rigid foundation. The analytical solution can be degenerated theoretically to the canonical model of a shear wall embedded in a half‐space for either a zero depth‐to‐width ratio of the canyon or an infinite canyon‐building distance. Through a numerical comparison with two past exact solutions to the sole shear wall model as well as the sole V‐shaped canyon model, the correctness of the method in this paper is verified. A systematic parametrical analysis in both frequency and time domains is performed. It is found that the seismic response of the building may be amplified when it is on the wave‐facing side of the canyon. The degree of amplification is closely related to the size and depth‐to‐width ratio of canyon, the wave velocity of half‐space, and the incident angle and frequency content of seismic waves. The potential adverse effects of the V‐shaped canyon on the ground motion input of adjacent buildings should be considered in the seismic design.

Seismic assessment and dissipative bracing retrofit-based protection of infills and partitions in RC structures

A balanced performance improvement of the constituting structural members, infills and partitions is a fundamental requirement in seismic retrofit design of frame buildings. In order to pursue this objective, the response of the non-structural elements must be accurately simulated, so as to evaluate their damage evolution and the correlation with the response of the structural skeleton. In the study presented in this article, diagonal no-tension struts with multilinear “pivot”-type hysteretic behaviour are adopted as substitute elements for masonry infill and partition panels. A trilinear axial force–displacement backbone curve is generated for the equivalent struts and transformed in the lateral force-drift curve of the panels. The latter is then scanned in terms of sequential performance limits and ranges. This model is demonstratively applied to a real case study, i.e. a reinforced concrete frame building damaged by the 2016 Central Italy earthquake, although a retrofit intervention had been carried out a few years before. Based on the results of the time-history assessment analyses in its original conditions, an alternative retrofit solution is proposed, consisting in the incorporation of dissipative braces equipped with pressurized fluid viscous dampers. This technology was selected for its high-damping capacity, as well as for the prompt activation of the constituting devices starting from the early stages of the building seismic response. The verification analyses developed in retrofitted configuration for the main shock records of the 2016 earthquake confirm this property, showing slight damage only in a small number of partitions—instead of the diffused moderate-to-irreparable damage actually surveyed in the building partitions and infills—and safe response of all structural members.

A novel design criterion for I-shape beams of steel MRF buildings in subduction-zone earthquake-prone areas

This paper highlights the difference in the seismic response of 5-storey, 10-storey, and 15-storey steel moment resisting frame (MRF) buildings of various span lengths (6 m, 7.5 m, 9 m), located on Site class C in Vancouver, B.C., Canada, resulted under the mega-thrust subduction zone ground motions against crustal ground motions (GMs). To emphasize on the impact of GM duration on the seismic response of buildings, seven spectrally equivalent short and long duration record pair sets were selected from ground motion databases and employed in analyses. Numerical models that account for P-Δ effects and strength and stiffness degradation of steel MRF beams were used. Detailed nonlinear dynamic analyses were conducted to assess the collapse safety according to FEMA P695 (2009) methodology. The results indicated high probability of buildings’ collapse under the long duration subduction GM suite, with a 38% average reduction in the median collapse capacity. Moreover, tall MRF buildings designed according to the current building code and steel design standard did not satisfy the collapse safety criteria when subjected to subduction GMs characterized by significant duration t5-95 > 60 s, while the middle-rise buildings showed borderline pass. To overcome this drawback, a novel design criterion for I-shape MRF beams is proposed; hence, selecting MRF beam sections of Class 1 that are able to achieve aggregated fatigue coefficient greater than the proposed limit value, the occurrence of low cycle fatigue of plastic hinge region of MRF beams is delayed and the collapse safety criterium is achieved.

Effect of bracing configuration on the seismic response of buildings with re-entrant corners

Effect of bracing configuration on the seismic response of buildings with re-entrant corners

A Review Paper on Comparative Analysis on RCC Structure with Energy Dissipation Device and Composite Structure

Abstract: In recent years considerable attention has been paid to research and development of structural vibration control devices with particular emphasis on mitigation of wind and seismic response of buildings. Many vibration-control measures like passive, active, semi-active and hybrid vibration control methods have been developed. Base isolation is a passive vibration control system. The isolator partially reflects and partially absorbs input seismic energy before it gets transmitted to the superstructure. Lead rubber bearing isolators are placed between the superstructure and foundation, which reduces the horizontal stiffness of the system. It thereby increases the time period of the structure and decreases the spectral acceleration of the structure. The superstructure acts like a rigid body, thus inter storey drift is reduced. This study is concerned with the effects of various vertical irregularities on the seismic response of a structure and controls this response using base isolation. The objective of the study is to carry out response spectrum analysis. The predominant lateral loads acting upon building structures are earthquake and wind induced forces. If wind load is much greaterthan earthquake load, the lateral force resisting system required to tackle wind loading may be enough to resist the smaller earthquake load. In this situation, a seismic base isolator will not bring any benefit to the building system. Furthermore, if time period of a building without isolator is greater, incorporation of isolator will not bring much difference to the building behavior with respect to seismic load. Additionally, for buildings with lowerstructural time periods, incorporation of an isolator will greatly alter the seismic behavior

Influence of Stone Columns on Seismic Response of Buildings Considering the Effects of Liquefaction

In this paper, the behaviour of a soil-foundation system supported on a stone column-reinforced liquefiable soil strata is investigated through finite element analysis. The numerical analyses are performed on a five story reinforced concrete moment resisting building supported on a raft foundation. The influence of stone column slenderness ratio on liquefaction mitigation is studied by varying the length of stone columns at a constant area replacement ratio. The results are obtained based on the excess pore pressure, free-field soil settlement, foundation settlement, acceleration response, superstructure's inter-story drift, and lateral story displacement for each ground motion. The results showed that the liquefaction of free-field soil had a major impact on the foundation settlement and building lateral deformation. With the inclusion of stone columns, excess pore pressure ratio in the free-field region reduced considerably, which had immediate effects on the building's lateral deformation.

Development and Application of a Platform for Multidimensional Urban Earthquake Impact Simulation

Earthquakes can be devastating to cities. Therefore, accurate and efficient simulation of the potential seismic damage to buildings has become an indispensable part of worldwide efforts to mitigate earthquake hazards. Precise simulation results can highlight potential seismic damage and serve as a reference in urban development and for planning post-earthquake rescue operations. In urban areas, simulation of the structural dynamic response during an earthquake is key for planning an appropriate emergency response. Multidimensional visualization of the effects of earthquakes is a popular technique in current earthquake simulation research. In the present study, a dynamic multidimensional simulation method was developed for analyzing the impact of an earthquake on buildings. This method involved conducting three-dimensional (3D) dynamic analysis of data from a seismic capacity database. Polygonal models and seismic capacity data were used in a high-performance computing process to calculate the seismic response of each building in an urban environment. On the basis of the calculations, a platform was developed for multidimensional urban earthquake impact simulation (MDUES). The developed MDUES platform enables analysis of the impact of long-period earthquakes, simulation of the 3D seismic responses of buildings, and visualization of the disaster risk and earthquake impact in a specified area. In summary, simulation of structural seismic responses in an urban setting necessitates a careful examination of the characteristics of ground and building motion, and the results of this simulation can provide a crucial reference for city planning, post-earthquake rescue operations, and seismic damage assessments.

Improving the Seismic Response of Tall Buildings: From Diagrid to Megastructures and Mega-Subcontrol Systems

Background: Diagrid structures, widely used for the tall buildings of the third millennium, are characterized by a very effective behaviour in the elastic field due to the grid triangulation. In particular, under horizontal actions, axial forces and deformations mainly arise in the structural members of the diagrid, thus resulting in the reduction of the shear lag effect and racking deformations. The response to incremental horizontal actions beyond the plastic threshold, however, shows a poor plastic redistribution capacity, with consequent low values of global ductility, in spite of a significant design overstrength. Objective: In this paper, it is proposed to exploit the high elastic efficiency of the diagrid type and use a vibration control system, based on mass damping mechanism with large mass ratios, to reduce a priori the inelastic demands due to seismic actions. Methods: Starting from the analysis of the seismic behavior of archetype diagrid buildings, a case study is selected to assess the effectiveness of the proposed motion-based design approach. For this purpose, the diagrid is first transformed into a megastructure (MS) configuration by densifying the diagonal elements at the most stressed corner areas and transfer floors, suitably chosen. Then, the exterior mega-frame is detached from interior sub-structures, thus allowing for a relative motion between the two structural portions according to a “mega-sub-structure control system” (MSCS), which activates the mass damping mechanism. Results: Time-history analyses carried out on simplified lumped-mass models confirm the effectiveness of the proposed strategy in reducing the seismic response. Conclusion: Finally, the practical feasibility of the MSCS and engineering solutions for the relevant structural organization are discussed.

Multi-Regression Analysis to Enhance the Predictability of the Seismic Response of Buildings

Several methodologies for assessing seismic risk extract information from the statistical relationship between the intensity of ground motions and the structural response. The first group is represented by intensity measures (IMs) whilst the latter by engineering demand parameters (EDPs). The higher the correlation between them, the lesser the uncertainty in estimating seismic damage in structures. In general, IMs are composed by either a single (scalar-based IMs) or a group of features of both the ground motion and the structure (vector-valued IMs); the latter category provides higher efficiency to explain EDPs when compared to the first one. This paper explores how to find new vector-valued IMs, which are highly correlated with EDPs, by means of multi-regression analysis. To do so, probabilistic nonlinear dynamic analyses have been performed by considering a seven-story reinforced concrete building as a testbed. At a first stage, 30 scalar-based IMs have been correlated with 4 EDPs (i.e., 120 groups of IM-EDP pairs have been studied). Afterwards, the structural responses have been classified as elastic, inelastic and a combination of both. It has been analyzed how efficiency behaves when making these classifications. Then, 435 vector-valued IMs have been created to enhance the predictability of the scalar EDPs (i.e., 1740 groups of IM-EDP pairs have been analyzed). Again, the most efficient IMs have been identified. Sufficiency, which is another statistical property desired in IMs, has also been examined. Results show that the efficiency and sufficiency to predict the structural response increase when considering vector-valued IMs. This sophistication has important consequences in terms of design or assessment of civil structures.

Seismic Responses of Buildings after the Mw 6.8 Sivrice Earthquake in January 2020

Seismic Responses of Buildings after the Mw 6.8 Sivrice Earthquake in January 2020

Evaluation of damage index and seismic vulnerability of an existing high-rise building

Seismic analysis of a structure assisted with damage index is vital for an efficient and reliable assessment of any impact of the earthquake on structures. The seismic vulnerability of a structure gives us the quantity associated with its weakness which allows us to estimate the amount of damage caused by future earthquakes. Indian region has been struck with earthquakes of various magnitudes since 1978, and many researchers have given an insight into the seismic vulnerability assessment of the structure after the earthquake has occurred by field investigation. Damage indices quantitatively estimate the degree of seismic damage a structure may suffer from an earthquake. Hence, damage indices can be used for earthquake damage assessment, evaluating the structure's performance, and assisting retrofitting decisions that can be taken based on the damage incurred. Various damage indices have been proposed by a lot of authors in the past, considering various theories and assumptions based on the topographical data of research. However, their reliability under IS code provisions is still ambiguous and questionable. This paper has attempted to investigate the damage index and check the variation for various output characteristics by altering the input parameter using ETABS. The work presented in the paper aims to estimate the seismic vulnerability of an existing building in the city of Coimbatore (India) by adopting the Maximum inter-storey drift ratio (MIDR) as the damage index. Further, the building's seismic response has been investigated by varying the inputs such as soil type and seismic zones using the response spectrum method to understand the various impacts of the input parameters of seismic analysis on the damage index adopted. Among all the cases analyzed, the configuration where the structure was investigated in soft soil under zone 5 has displayed the maximum degree of damage and the maximum displacement response.

Structural irregularity quantification in buildings using vital signs

The complexity of structural irregularity guidelines in seismic design codes is increasing with revised versions of the code to cater to increased construction of iconic shaped buildings coupled with lessons learnt from building failures during past earthquakes. This short communication paper intends to present a medical approach to check the irregularity of a building based on common parameters which are indicators of its deviance from a regular configuration. Similar to the “vital signs” in medical profession, namely, body temperature, pulse rate, respiratory rate and blood pressure which are indicators of health of a human body or its disease-free state, the extend of irregularity of building structures is quantified by four parameters considered as “vital signs” in buildings, namely, time period, average support reaction per bay, distance between center of mass and center of rigidity and lateral displacement of diaphragm center of mass with increasing storeys. An implementation of the approach is demonstrated based on the analysis and result interpretation carried out on five storied building models. The outcomes of regular and irregular buildings differed significantly, which shows that there exists a similar relationship between the seismic response of buildings with various types of irregularities and can be represented using common parameters that need to be incorporated in future revisions of sesmic design codes.

Effect of the infill panels in the floor response spectra of an 8-storey RC building

One of the significant challenges concerning earthquake risk mitigation is the seismic vulnerability assessment of existing buildings that were not designed according to modern codes. Several authors recognized that the infill walls might significantly affect the seismic response of reinforced concrete structures (RC). Still, they are treated as “non-structural” elements by the national and international codes and they are not considered in the seismic assessment of existing RC buildings, and their impact on the seismic response of the structure is neglected. This manuscript aims to study the seismic response of an 8-storey RC structure simulated in the software OpenSees with and without masonry infill walls. The masonry infill walls were simulated considering their in-plane and out-of-plane (OOP) behaviour interaction. Two different studies were performed. First, the study of the impact of the infill walls in the global building seismic response and after that the study of the infill walls seismic performance. Several incremental dynamic analyses were carried out for these studies to study floor accelerations and velocities and determine peak floor acceleration and peak floor velocity. At the same time, floor response spectra were drawn for the design peak ground acceleration, according to Eurocode 8. Acceleration-Displacement Response Spectrum is also obtained and presented according to Eurocode 8. The OOP accelerations and OOP velocities of the masonry infill walls were recorded for all the input ground-motions. The maximum OOP accelerations and velocities reached by the infill panels at each floor were obtained and discussed. The respective infill acceleration and infill acceleration-displacement response spectrum and infill velocity response spectra were then derived and presented. Finally, the amplification of the infills OOP accelerations along the building height will be evaluated and compared with the Eurocode 8 demands. The results show that the infills increase the peak floor accelerations and modify the floor response spectra. The infills OOP accelerations are always 1.2–2 times higher than PFA. The infills acceleration response spectra do not change with the increase of the building height.

Influence of a tunnel on the seismic response of an adjacent tall building considering dynamic interaction of Building-Soil-Tunnel system

Excavating tunnels in urban areas could have a profound effect on the site characteristics and could change the free-field motion due to many different reasons. Although the previous earthquake events have ascertained that the response of the above-ground buildings close to the tunnel will also change, this effect is not well-addressed in the national and international design building codes. In this paper, considering a fully coupled system of tunnel-soil building interaction, the presence of a tunnel on the seismic response of a two dimensional 15-story scaled benchmark building under two far- and two near-field benchmark earthquake records has been investigated. Additionally, non-linear dynamic analyses considering the material and geometric nonlinearity have been applied, and to obtain nonlinear behavior of the soil, Mohr-Coulomb failure criterion and the equivalent linear method are implemented. The interface between structural foundation and soil is simulated by normal and shear springs and, the interaction between tunnel and soil is modeled using Coulomb Friction. As a parametric study, the effect of tunnel shape, cross-sectional area, the burial depth of the tunnel, and the effect of site soil material on the seismic response of the building is evaluated by evaluating the ratio of the structural responses with the presence of the tunnel to the structural responses without the presence of the tunnel. The results showed that the maximum relative displacements of the building for soils with 320 and 150 m/s in the presence of the tunnel decrease at most 10 percent under both far- and near-field earthquake records.