Peak Interstory Drift Ratio Research Articles

Comparative seismic analysis of frames with shape memory alloy slip friction dampers

This study investigated the seismic performance of 6-, 9-, and 12-story concentrically braced steel frames utilizing shape memory alloy slip friction dampers (SMASFDFs). For comparison purposes, identical frames equipped with self-centering braces (SCBFs) and buckling-restrained braces (BRBFs) were also designed and analyzed. The seismic performance of considered frames was evaluated through nonlinear static and nonlinear time history analysis (NLTHA) under three seismic hazard levels, i.e., frequently occurred earthquakes (FOE), design basis earthquakes (DBE), and maximum considered earthquakes (MCE). Incremental dynamic analysis (IDA) was conducted to examine the seismic responses, including peak interstory drift ratios (PID), peak floor accelerations (PFA), and residual interstory drift ratios (RID), of the designed frames under varying levels of seismic intensity. Fragility curves considering single and multiple seismic responses were obtained based on the IDA results. The results show that the SMASFDFs have comparable deformation control capacity as the BRBFs while exhibiting zero RID and more uniform deformation distribution over the building height. Moreover, in most circumstances, the joint failure probability is lowest for the SMASFDFs when considering multiple seismic responses. From a seismic design perspective, current results suggest that the SMASFDFs can be designed with the same strength reduction factor (R) if the PID is especially concerned.

Seismic life-cycle cost evaluation of steel-braced frames: Comparing conventional BRBF with emerging SCVDF and HBF systems

In the past two decades, various self-centering bracing systems have been developed to enhance structural seismic resilience. However, compared to conventional bracing systems, their high initial cost and lower efficiency in controlling peak floor accelerations have reduced their economic benefits and limited their application in engineering projects. Accordingly, the self-centering viscous energy-dissipative brace (SCVDB) and the hybrid bracing system (HB), the synergistic combination of the SCVDB and buckling-restrained brace (BRB), have emerged as innovative approaches with exceptional capabilities in passive control over peak floor acceleration demand. Despite their promise, a comprehensive understanding of the life-cycle economic benefits of structures equipped with these bracing systems remains limited. This study aims to comprehensively highlight the life-cycle economic benefits associated with self-centering viscous energy-dissipative braced frames (SCVDFs) and hybrid braced frames (HBFs) compared to traditional buckling-restrained braced frames (BRBFs) across various structural heights using the improved HAZUS assessment methodology. Focusing on 4-, 8-, and 12-story buildings designed with BRBFs, SCVDFs, and HBFs, each maintaining identical peak inter-story drift ratios, the research conducts dynamic analyses combined with Monte Carlo simulations. Critical parameters such as residual inter-story drift (RID) limits defined for demolition, initial construction costs of the SCVDBs, and discount rates are considered. The analyses reveal that the expected annual earthquake-induced loss (EAL) for mid- and high-rise structures is more sensitive to RID limits than those of low-rise structures. The SCVDFs and HBFs exhibit lower EAL than BRBFs, even without considering the demolition situation. The RID limit, initial construction cost of SCVDBs, and discount rates significantly influence the relative economic benefits of SCVDFs and HBFs compared to BRBFs. In most scenarios, HBFs demonstrate superior economic benefits over SCVDFs. The HBF effectively utilizes the synergistic effects of SCVDBs and BRBs, substantially lowering initial construction costs and achieving favorable economic benefits across various structural heights within the considered parameter range.

Strain energy-based uniformity spectrum for elastic deformation control of super high-rise buildings under near-fault pulse-like earthquake excitations

To reasonably control the elastic lateral deformation of super high-rise buildings under near-fault pulse-like ground motions, inspired by a potentially close link between material utilization and normalized strain energy, a novel generalized uniformity spectrum of normalized strain energy (GUSNSE) is proposed via the nonuniform flexural-shear coupled model. With a full understanding of the characteristics of spectral shapes and the influence of shear-flexural stiffness ratios and mass-stiffness nonuniformity, the GUSNSE is fitted by artificial pulses. Utilizing the GUSNSE, a lateral stiffness estimation strategy is developed with the requirement of peak interstory drift ratios (IDRs). The feasibility and effectiveness of the proposed strategy are systematically demonstrated by comparison with not only the original lateral stiffness schemes of three significantly distinct buildings but also those designed for uniform IDRs. The accuracy of the fitted GUSNSE is also validated via the data estimated by four sets of ground motions. The GUSNSE-based strategy is promising as an efficient, reliable, and practical tool for providing lateral stiffness of super high-rise buildings in the preliminary design.

Seismic Response of Vertical Hybrid Concrete/Steel Frames Considering Soil–Structure Interaction

The aim of this study is to investigate the seismic behavior of concrete/steel mixed structures. In engineering praxis, many buildings consist of two parts: one made of reinforced concrete and the other made of steel. There are several difficulties in the code-based seismic design of these structures due to the different dynamic responses of each discrete part. Seismic design codes, such as the IBC and Eurocode 8, do not provide instructions for structures consisting of two parts. In addition, they use a single-loading scenario, but there are many locations that are affected by more than one earthquake in a short period. Another drawback is that recent provisions do not consider soil–structure interaction effects. The specific issue addressed here is the seismic response of mixed structures, which is evaluated through inelastic time–history analysis. More specifically, the response indices involve height-wise distributions for peak interstory drift ratios, maximum floor horizontal displacements, maximum floor accelerations, and plastic hinge formations in the frame elements when they are subjected to seismic sequences of earthquakes, as well as in far fault ground motions for different soil types. The results reveal that sequential ground motions lead to increased displacement demands, and they affect the permanent displacements. This phenomenon appears in both cases of stiff and flexible soil, as well as for both regular and irregular frames. It is found that soil–structure interaction generally leads to lower values of IDR, and maximum horizontal displacement and acceleration in comparison with the case of rigid soil assumptions.

A two-level performance-based plastic design method for multi-story steel frames with double-yielding systems

The performance-based seismic design (PBSD) is usually conducted under design basis earthquakes (DBE), and then, the performance of the designed structures is examined under maximum considered earthquakes (MCE). As a result, it is challenging to simultaneously satisfy the performance targets associated with the DBE and MCE levels. To this end, this study proposes a two-level performance-based plastic design (PBPD) method. The fused steel frames exhibiting trilinear capacity curves are selected as the example structures. The peak interstory drift ratios under the DBE and MCE levels are defined as the performance targets and they are explicitly utilized at the beginning of the design procedure. The expressions of two energy modification factors are first obtained by establishing energy balance equations for single-degree-of-freedom (SDOF) systems under the DBE and MCE levels, respectively. Nonlinear time history analyses (NLTHA) for SDOF systems with various trilinear capacity curves are conducted to derive necessary design parameters. The versatility and flexibility of this design method are achieved by enabling both the primary and secondary yielding systems to yield under the DBE level. To demonstrate and validate the proposed design method, a six-story benchmark steel frame equipped with idealized metallic yielding damping braces is selected and designed with two sets of performance targets. The nonlinear static and NLTHA results proved that the designed structures can simultaneously meet the prescribed performance targets under both DBE and MCE levels.

Seismic performance and vulnerability analysis for bifurcated tunnels in soft soil

This paper investigates the seismic performance of complex comprehensive interchange underground structures. As an example, the seismic performance of Nanjing underground bifurcated tunnels constructed in soft soil is analyzed. A three-dimensional (3D) numerical finite element analysis model is established considering soil-tunnel interaction to analyze the seismic response characteristics and failure mechanism of the bifurcated tunnels. The results show that the tunnel damage degree is closely associated with the deformation response, and that the inter-story drift ratio of the lower layer is significantly greater than that of the upper layer. The pushover analysis method is used to obtain the seismic performance curve of the tunnel, and inter-story drift ratio limits are defined. The IDA procedure is then used to conduct multiple non-linear dynamic time history analyses based on the 3D finite element model, and IDA curve clusters are drawn with peak ground acceleration (PGA) as the earthquake intensity measures and the peak inter-story drift ratio as the damage measures of tunnels. The corresponding IDA percentiles lines are calculated, and the seismic fragility curves of the bifurcated tunnels are established. The post-earthquake functional failure probability of the bifurcated tunnels is obtained under different seismic fortification performance level.

Seismic performance evaluation of reinforced concrete hilly buildings under sequence of earthquakes

SummaryThe present study investigates the effect of earthquake sequences on the response of reinforced concrete hilly buildings having typical configurations, that is, stepback and split‐foundation, with three different story ratios. A set of 30 as‐recorded mainshock‐aftershock sequence of earthquake ground motions is considered for this study. Mainshock acceleration time histories are scaled at two distinct intensity levels to obtain the mainshock‐damaged building. These mainshock‐damaged hilly buildings are then subjected to aftershocks. A comparative study is performed for various response quantities, such as peak interstory drift ratio, peak floor acceleration, and peak roof displacement of undamaged and mainshock‐damaged buildings under aftershocks. Further, fragility analysis is carried out to study the effect of aftershocks on undamaged and mainshock‐damaged hilly buildings. Subsequently, component‐wise seismic loss estimation due to damage in the non‐structural and structural components is performed. It is concluded from the study that the building components that contribute maximum to the expected repair cost ratio vary with respect to the intensity of the aftershocks. Also, the estimated seismic loss is higher in mainshock‐damaged split‐foundation buildings in comparison to stepback buildings.

Seismic behaviour of post-earthquake composite frame structures with different damage levels

Since earthquakes pose a huge threat to buildings, the post-earthquake safety assessment is quite important, especially in earthquake-prone areas. This paper investigates the seismic performance of post-earthquake composite frame structures with different damage levels. Two-stage nonlinear time history analysis is carried out for a ten-story steel–concrete composite frame and the peak ground acceleration (PGA) of the seismic waves is used as the main parameter characterizing the seismic intensity and damage level. In the first stage, the seismic waves with the PGAs of 0.20 g, 0.30 g and 0.40 g are applied to the frame to result in three different damage levels. The peak inter-story drift ratios, residual inter-story drift ratios and plastic hinge ratios of the structure in the first-stage earthquakes are analysed, which presents a uniform distribution pattern for the three damage levels. The composite frame is evaluated as structurally safe at all three damage levels based on the limits of residual inter-story drift ratios given in current standards. In the second stage, the seismic waves with the PGA of 0.40 g are used to explore the residual capacity of the structure subjected to strong earthquakes. The dynamic responses of the intact structure and the structure with different damage levels are compared. The results indicate that despite the recognised structural safety, pre-existing seismic damage can enlarge the lateral deformation, reduce the internal forces and resistance capacity and increase the plastic hinges when the composite frame is exposed to the second-stage earthquakes. Generally, the damage caused by earthquakes with the PGA of 0.40 g will have an obvious influence on the seismic behaviour of the post-earthquake structure, in which situation further safety assessment and structural repairs are necessary.

Machine vision‐based automated earthquake‐induced drift ratio quantification for reinforced concrete columns

SummaryThis paper presents a novel method for estimating the seismic peak interstory drift ratio (IDR) in reinforced concrete (RC) columns after an earthquake using surface crack image analysis. The quantitative representation of the complexity and irregularity of crack images in damaged RC columns is obtained through the consideration of the generalized fractal dimensions. The authors have compiled a comprehensive database consisting of 445 crack maps obtained from cyclic experiments conducted on 110 rectangular RC column specimens exhibiting double‐curvature deformation mode. This database is utilized by the authors to develop and validate the proposed procedure. The research database contains a wide range of structural and geometric features. Five closed‐form equations are developed with the objective of estimating the peak IDR experienced by the RC columns during a seismic event. The predictive equations are derived through the utilization of symbolic regression technique, with the input parameters varying according to the availability of columns characteristic parameters. Results reveal that generalized fractal dimensions, especially D−1, are strong vision‐based indicator of damage in RC columns having correlation coefficients with IDR ranging from 0.82 to 0.92 across the considered plans. The seismic peak IDR obtained through the empirical equations can serve as the input engineering demand parameter (EDP) in the seismic loss estimation frameworks. This allows for the determination of the probability of exceeding damage states for structural and nonstructural components of concrete buildings. Finally, the practical implementation of the methodology is examined by its application to an actual case of a damaged column during the Kermanshah earthquake of magnitude 7.3 that occurred in 2017.

ASCE/SEI 7‐compliant site‐specific evaluation of the seismic demand posed to reinforced concrete buildings with real and simulated ground motions

AbstractState‐of‐the‐art seismic design and assessment methodologies rely on the utilization of ground‐motion records scaled to site‐specific risk‐targeted spectra to perform nonlinear time‐history analyses and estimate mean structural demands. Motivated by the discrepancies in structural response estimates resulting from different selection and scaling methods, this study assesses the implications of utilizing site‐specific simulated ground motions from 3‐D physics‐based wave‐propagation models as opposed to historical records from worldwide catalogs in ASCE/SEI7‐compliant procedures for seismic performance evaluations. A suite of validated realizations of an M7 Hayward Fault earthquake in the San Francisco Bay Area and two modern reinforced concrete moment‐resisting frame buildings are utilized as a case study. The 2014 USGS earthquake hazard and probability maps are employed for the hazard calculations, and the PEER NGA‐West2 database is used for the selection of the real ground motions. The building models are coupled with the simulated and real ground motions to perform a total of 30,552 nonlinear time‐history analyses. Structural demands obtained from real and simulated motions are examined and compared at the regional‐scale in terms of peak interstory drift ratio median and dispersion, and localization along the building height. The correlations between observed structural responses and ground‐motion features are discussed to potentially inform current code‐compliant methodologies for ground‐motion selection. Results show that utilizing site‐specific simulated ground motions that incorporate path, fault geometry, and site‐condition effects as opposed to historical ground‐motion records may lead to differences in the structural demands above 50%. Such differences are highly spatially variable throughout the region and difficult to predict.

Non-linear study of the method of transition in mixed concrete/steel structures

A critical zone is formed at the junction of the lower concrete and upper steel sections in mixed concrete/steel structures in terms of gravity and lateral loads caused by the support reactions of the steel frame. There are two common approaches to transition from concrete section to steel one in this critical zone: the first is the direct pin connection of the steel frame to the concrete frame, and the second is the application of a concrete-steel composite story called the transition story. Until now, various studies have been conducted on mixed concrete/steel structures, but no study has investigated and compared the two mentioned approaches. Considering the importance of this issue, 18 models of mixed concrete/steel structures were formed in the present study according to the two approaches and the different places of connection of the concrete and steel sections along the height of the structure. Fragility curves were generated for all models using Incremental Dynamic Analysis (IDA) under 44 far-field ground motion records and probability function at the complete damage state based on HAZUS technical report. A comparison was made from the strength point of view considering the two approaches to transition. Next, to investigate the non-linear response of the structure at the complete damage state, the Peak Inter-Story Drift ratio (PISD) was obtained in the different levels of collapse intensity from IDA for different stories. The results showed that the application of transition story improves the seismic behavior of mixed concrete/steel structures and increases Median Collapse Capacity (MCC) in 7, 13, and 19-story structures up to 24.63%, 19.54%, and 17.99%, respectively. In addition, it makes the displacement of the structure more uniform and reduces the significant difference of drift in the critical zone.

Assessment of ground motion amplitude scaling using interpretable Gaussian process regression: Application to steel moment frames

AbstractThe process of ground motion selection and scaling is an integral part of hazard‐ and risk‐consistent seismic demand analysis of structures. Due to the lack of ground motion records that naturally possess high amplitude and intensity, the research community generally relies on scaling the records to match a target hazard intensity level. The scaling factors used are frequently as high as 10. Due to the criticism received in previous research studies, the extent of amplitude scaling and its process has become a matter of debate, and various constraints on the scaling factors have been proposed. The primary argument against unrestricted amplitude scaling is the unrealistic nature of the scaled records and the possible biases caused in the engineering demand parameters (EDPs) of structures. This study presents a framework to utilize machine‐learning and statistical techniques for the assessment of ground motion amplitude scaling for nonlinear time‐history analysis (NTHA) of structures. The framework utilizes Bayesian non‐parametric Gaussian process regressions (GPRs) as surrogate models to obtain statistical estimates of EDPs for scaled and unscaled ground motions. The GPR surrogate models are developed based on a large‐scale analysis of five steel moment frames (SMFs) using 200 unscaled as‐recorded ground motions for ten spectral acceleration levels, () (ranging from 0 g to maximum considered earthquake, MCE) and 2500 scaled ground motions representing 50 scale factors (), and the 10 levels for each SMF. For each building, two types of EDPs are considered: i) peak inter‐story drift ratio (PIDR) and ii) peak floor acceleration (PFA). To provide a better interpretation of the GPR surrogate models, the concept of explainable artificial intelligence (i.e., Shapley additive explanation, SHAP) is used to obtain insights into the decision‐making process of the GPR models with respect to the and . Then, for the 10 levels, the GPR‐based EDP estimates under scaled ground motions corresponding to 50 different SFs are compared with the EDP estimates of unscaled ground motions. The comparison is conducted using Kolmogorov–Smirnov (KS) statistical hypothesis test. Results indicate that the range of allowable s depends on two factors: i) intensity level (characterized by ), and ii) the dynamic properties of the building. In general, it is noticed that allowable s range between 0.5 and 3.0 for PIDRs, and from 0.6 to 2.0 for PFAs. Finally, the EDP between the unscaled and scaled ground motions are adhered to various discrepancies observed in different intensity measures representing amplitude‐, duration‐, energy‐, and frequency‐ content of the two sets of ground motions.

Evaluation of seismic response of coupled wall structure with self-centering and viscous damping composite coupling beams

In order to reduce the residual displacement and floor acceleration of coupled wall structures, a novel self-centering and viscous damping composite coupling beam is proposed. The proposed coupling beam consists of the elastic beam segments and the fuse part, which incorporates self-centering friction dampers and viscous dampers. The self-centering friction damper can provide strength and stiffness for the proposed coupling beam and reduce the residual displacement of the coupled wall structure. The viscous damper can add supplemental damping to the system, and this can control the peak lateral displacement demands and floor accelerations of the structure. Moreover, the proposed coupling beam can eliminate the beam elongation effect of the self-centering coupling beam with a rocking behavior. Design methodology and nonlinear numerical model of the proposed coupling beam are developed. The seismic behaviors of the coupled wall structure with the self-centering and viscous damping composite coupling beams (CW-SCVCCB) are assessed and compared with the structure with reinforced concrete coupling beams (CW-RCCB), the structure with steel coupling beams (CW-SCB) and the structure with self-centering coupling beams (CW-SCCB). Analysis results showed that the supplemental viscous damping can effectively reduce the peak interstory drift ratio and floor accelerations of the structure. The residual displacement of the novel coupled wall system is larger than that of the CW-SCCB, however, it is significantly reduced compared with the CW-SCB and the CW-RCCB.

Shake table tests of a corrugated steel sheathed cold-formed steel structure

The corrugated steel sheathed cold-formed steel (CFS) shear wall is an innovative lateral force-resistant system with excellent potential for development. Many research has been conducted on the seismic behavior of this innovative shear wall system. However, dynamic properties as well as the failure mechanism of the CFS structures with corrugated steel sheathing are still unclear. This study aimed to increase knowledge of the seismic performance of CFS structures through the shaking table test, of which the seismic force resisting system was provided by corrugated steel sheathed shear walls. Importantly, this test also took into account the extremely rare precautionary intensity. The main results indicated that damage of CFS structure began to occur in the walls and floors under rare earthquakes and increased further with the seismic intensity. The final damage primarily occurred through the failure of connections and inner panels under extremely rare precautionary intensity. The degree of variation in the dynamic properties of the structure increased further as the damage accumulated. In particular, the damping ratio of the structure in the non-linear phase ranged from 5% to 7.5%. It was unreasonable to assume that the trend of the acceleration amplification factor with structural height was determined as a linear relationship. The peak inter-story drift ratio of the corrugated steel sheathing CFS structure could meet the multi-level seismic precaution requirements of the code. Finally, the seismic performance parameters of the CFS structure were evaluated by numerical simulations. This research will provide a reference for the seismic design of CFS structures under extremely rare conditions.

Mainshock-aftershock effect on the seismic performance of multi-story CBFs equipped with SMA-friction damping braces

This paper aims to understand the effect of mainshock-aftershock earthquake sequences on the seismic performance of multi-story concentrically braced frames (CBFs) equipped with shape memory alloy (SMA) friction damping braces (SMAFDBs), based on a comparison with those equipped with buckling-restrained braces (BRBs). The SMAFDB is a serial connection of SMA damper and friction damper. The friction damper starts to slip and serves as the “fuse” element to protect the SMA damper under destructive earthquake events. Ten ground motion records corresponding to the maximum considered earthquake (MCE) hazard level are defined as the mainshock input, and the aftershock input is generated by appropriately scaling the mainshock input to four seismic hazard levels. To achieve a fair comparison, the considered CBFs are first designed to exhibit identical mean height-wise peak interstory drift ratios under the design-basis earthquake (DBE) ground motions. Then, these two frames are subjected to four suites of mainshock-aftershock earthquake sequences and their seismic responses are compared against each other. It indicates that both the peak and residual interstory drift ratios of the SMAFDB frame (SMAFDBF) are smaller than that of the BRB frame (BRBF) on average during the aftershock earthquakes, which is found primarily attributed to the fact that the former suffers from smaller post-mainshock residual deformation. The higher seismic capacity of the SMAFDBF over the BRBF is also confirmed by conducting fragility analysis. Finally, the recentering capacity under aftershock earthquakes are analyzed for both frames, based on the maximum residual interstory drift ratios.

P-Delta effects on nonlinear dynamic response of steel moment-resisting frame structures subjected to near-fault pulse-like ground motions

The objective of this study is to explore the P-Delta effects on the steel moment-resisting frame structures (MRFs) subjected to the near-fault ground motions with large, medium, and small pulse periods. The 3-, 9-, and 20-story MRFs designed for the American SAC Phase II Steel Project are used as benchmark models. Three near-fault and one far-field ground motion groups, each with 11 different records, are selected for the nonlinear time-history analysis. The P-Delta effects are quantified based on peak inter-story drift ratio (PIDR) demands. When the near-fault ground motions act on the structures, even if the structures have the low height and the earthquake is weak, the P-Delta effects could not be ignored. The nonlinear response of the group with Tp near to T1 is the largest, but the largest P-Delta effects appear in the group with TP slightly larger than T1. P-Delta effects do not influence the prediction of the weakest floor and the PIDR demands due to the ground motions which can trigger higher-mode effects. However, for long-period buildings, P-Delta effects can sharply increase the components’ distortion at the low half of the structure and even change the structural collapse direction, although P-Delta effects would decrease the demands at the middle stories. The panel zones are significantly important components for the seismic performance of MRFs and not only the weakest floor but also all the floors at the low half of the building are worthy of attention in the seismic design of MRFs.

P-Delta Effects on Nonlinear Seismic Behavior of Steel Moment-Resisting Frame Structures Subjected to Near-Fault and Far-Fault Ground Motions

This paper presents a comparison of P-Delta effects on the nonlinear seismic behavior of the steel moment-resisting frame structures (MRFs) subjected to near-fault and far-fault ground motions. The 3-, 9- and 20-story MRFs designed for the American SAC Phase II Steel Project are used as benchmark models. The 40 near-fault ground motions with large velocity pulses, as well as ten typical far-fault ground motions, are selected and scaled for the nonlinear time-history analysis. The P-Delta effect is quantified based on peak inter-story drift ratio (PIDR) demands. The displacement demands of the whole structure and the distortion of the structural components are compared and analyzed. It was found that, at each floor, the P-Delta effect under near-fault ground motions is more significant than that under the far-fault ground motions. The P-Delta effect under near-fault ground motions also increases more rapidly with decreasing structure height even for low-rise structures or low earthquake intensity. It was also found that the P-Delta effect cause the PIDR demands to increase by 10% for all three structures subjected to far-fault ground motions. In contrast, considering the P-Delta effect, the PIDR demands rapidly increase by 45% for the high-rise building subjected to near-fault ground motions. Note that the increasing PIDR demands occur at the weakest floor and with the stronger earthquake intensity. However, the P-Delta effect does not change the location of the weakest floor and the yield sequence of components. The seismic behaviors under far-fault and near-fault ground motions are significantly different, because near-fault ground motions not only have velocity pulse but also possibly trigger structural higher vibration modes. In addition, the P-Delta effect may change the distortion direction of the components so that the prediction of the structural collapse direction may be affected. In addition, it was found that if the structure’s period is near the pulse period, the P-Delta effect becomes more significant with the increase of earthquake intensity, and accordingly, it should not be ignored. Moreover, the P-Delta effect cannot be neglected either for the structures susceptible to near-fault ground motions, even if those structures are not tall or the earthquake intensity is not strong.

Rapid decision-making tool of piloti-type RC building structure for seismic performance evaluation and retrofit strategy using multi-dimensional structural parameter surfaces

Piloti-type reinforced concrete building structures have vertically irregular configurations composing a moment frame for parking spaces in the lower story and heavy-weight shear wall system for residential spaces in the upper stories. Due to these vertically irregular configurations, such building structures are governed by a soft-story mechanism, damage concentration on the first story. Since the 2017 Pohang earthquake led to severe damage to the piloti-type building structures on a regional level, a decision-making tool mitigating the seismic damage for future events is needed. This paper aimed to propose a rapid decision-making tool promptly estimating seismic damage with simple information and determining a retrofit scheme using a pre-developed extensive database, i.e., multi-dimensional structural parameter surfaces. The multi-dimensional surfaces were created using a simplified modeling approach with five structural parameters: period, strength ratio, and ductility controlling failure modes as the input, and peak inter-story drift ratio and demand-to-capacity ratio as the output. The proposed methodology was validated using a finite element model for the piloti-type building structure with a soft-story mechanism. The seismic responses detected from the multi-dimensional surfaces have a slight difference from those of the numerical model. Nevertheless, the rapid tool predicted a reasonable agreement with performance evaluation from the finite element simulation. In addition, the rapid tool provided feasible retrofit options to meet target performance using brief structural information. Due to its simplified process, the proposed tool can be implemented to the regional seismic assessment for the residential areas where the piloti-type building structures were highly concentrated.

A Physical-organizational Method for the Functionality Assessment of A Hospital Subjected to Earthquakes

ABSTRACT Hospitals play vital roles in mitigation and recovery in earthquake-hit communities. This paper aims to clarify the effect of physical damage on hospital organizations and represent a holistic method for the functionality assessment of a hospital. The efficiency of the method is demonstrated based on the case study of a general hospital. The results indicate that the functionality of hospitals would be significantly affected after the maximum considered earthquake. A considerable gap exists between the hospital treatment capacity and the patient demand for medical services. The method will assist hospital stakeholders and managers in design and upgrade criteria selection. Abbreviation: CT: Imaging Procedure; DBE: Design Basis Earthquake; DES: Discrete Event Simulation; DR: Digital Radiography; EDPs: Engineering Demand Parameters; HVAC: Heating Ventilation and Air Conditions; MCE: Maximum Considered Earthquake; OR: Operation Room; PFA: Peak Floor Acceleration; PFV: Peak Floor Velocity; PIDR: Peak Inter-story Drift ratio; RC: Reinforced Concrete; RIDR: Residual Inter-story Drift Ratio; RR: Resuscitation Room; SLE: Service Level Earthquake; UPS: Uninterruptible Power Supply; US: Ultrasound Room; WT: Waiting Time

Seismic performance assessment of reinforced concrete hilly buildings with open story

This study focuses on investigating the effect of one or more open stories in reinforced concrete hilly buildings. Two building configurations, i.e., (i) stepback and (ii) split-foundation, with three different story ratios, are considered. Open stories are provided at different levels in a building according to the prospective location of the approach road level. These buildings are subjected to bi-directional earthquake excitation, and non-linear dynamic analyses are performed under a suite of 22 ground motion records. Dynamic characteristics and seismic responses such as peak inter-story drift ratio, peak floor acceleration, peak roof displacement, and maximum story shear of the buildings are investigated. A probabilistic performance assessment of these buildings with different probable locations of the open story is presented. In general, the probabilistic assessment reveals that the presence of the open story significantly reduces the seismic performance of these buildings. Moreover, the buildings with the open story at the uppermost foundation level are found to be the most vulnerable under earthquake excitation.