Seismic Assessment Of Structures Research Articles

Seismic Assessment of Large-Span Spatial Structures Considering Soil–Structure Interaction (SSI): A State-of-the-Art Review

Soil–structure interaction (SSI), which characterizes the dynamic interaction between a structure and its surrounding soil, is of great significance to the seismic assessment of structures. Past research endeavors have undertaken analytical, numerical, and experimental studies to gain a thorough understanding of the influences of SSI on the seismic responses of a wide array of structures, including but not limited to nuclear power plants, frame structures, bridges, and spatial structures. Thereinto, large-span spatial structures generally have much more complex configurations, and the influences of SSI may be more pronounced. To this end, this paper aims to provide a state-of-the-art review of the SSI in the seismic assessment of large-span spatial structures. It begins with the modelling of soil medium, followed by the research progress of SSI in terms of numerical simulations and experiments. Subsequently, the focus shifts towards high-lighting advancements in understanding the seismic responses of large-span spatial structures considering SSI. Finally, some discussions are made on the unresolved problems and the possible topics for future studies.

Seismic assessment of structures with mass and stiffness irregularities under multiple earthquakes

Seismic assessment of structures with mass and stiffness irregularities under multiple earthquakes

Application of Endurance Time Method in Seismic Assessment of RC Frames Designed by Direct Displacement-Based Procedure

This paper addresses the Direct Displacement-Based Design (DDBD) approach of multi-story RC frame structures consistent with changes ‎to design criteria between Turkish earthquake codes of TSC-2007 and TBEC-2018. The corresponding response modification factor (R) of structures designed based on the DDBD approach is also estimated in this research. The design base shear forces of both codes are compared considering different R factors and also with that of the DDBD approach. The results showed that the DDBD approach, as per TBEC-2018, provides RC frame structures with higher R values compared to the similar approach in accordance with TSC-2007. The Endurance Time (ET) method is a time history-based procedure for seismic assessment of ‎structures ‎under intensifying dynamic excitations aided to judge their performance at various intensity levels. Since, up to now, the ET method has not been considered to evaluate the performance of the structures designed by the DDBD approach, this paper addresses this issue. The ET ‎performance curves of RC frames show that structures designed by the DDBD approach in ‎accordance with TBEC-2018 exhibit higher Interstory Drift Ratios (IDRs) values than TSC-2007 at various hazard levels.

Preface of the proceeding of 11th International Symposium on Current Research in Hydropower Technologies

The international symposium on Current Research in Hydropower Technologies (CRHT) aims to bring the researchers and students from the field of hydropower around the world in a common platform to share their research experiences. Since 2018, we have also been publishing papers from this conference in IOP Journal of Physics.This year in the symposium, we received 41 papers from Kathmandu University (KU), Tribhuwan University (TU), Norwegian University of Science and Technology (NTNU), École Polytechnique Fédérale de Lausanne (EPFL), Indian Institute of Technology (IIT-Roorkee), IIT-Delhi and Gujarat Technological University, Uka Tarsadia University and CK Pithawala, Gujarat.In the symposium, the overall event was divided into three sessions. The first group of sessions contained hydraulic turbines as well as hydropower and other technologies. We had presentations related to computational and experimental techniques related to the turbines, as well as civil and environmental aspects of the power plants, including sediment traps, tunnels and finding solutions for fish friendly and sustainable power plants. In the second group, there were sessions related to other forms of renewable energies as well, such as fuel cells, hydrokinetic turbines as well as seismic assessment of structures in hydropower. In the third group, we witnessed presentations related to condition monitoring of turbines, erosion and cavitation problems and some interdisciplinary aspects of the sustainable development.After receiving comments from the presentations and a peer review process, 36 papers have been selected for publication in this proceeding. We hope that the papers will be beneficial for the researchers and students involved in the sector of hydropower.

Explainable probabilistic deep learning framework for seismic assessment of structures using distribution‐free prediction intervals

AbstractA new probabilistic framework is proposed for providing a distribution‐free prediction interval (PI) of seismic responses required for various earthquake engineering applications. The framework overcomes the limitation of point prediction models and avoids the complexity of traditional probabilistic methods. The framework utilizes a few assumptions of probability distributions and requires no prior assumed statistical distribution for the PI. Ensemble probabilistic deep learning models (DLMs) are used to provide quality‐driven PIs of seismic responses for low‐ to mid‐rise buildings with limited irregularity. Considering these systems and ground motions with the aid of Monte Carlo simulation and nonlinear time‐history analysis (NLTHA), huge datasets are generated for training. To have an insight into the probabilistic DLM, explainable artificial intelligence techniques are used. The superiority of the proposed framework in quantifying uncertainties is validated by comparison with the conventional Bayesian method. In addition, its applicability is investigated by providing bounds of seismic fragility curves, life cycle cost, and resilience index obtained by NLTHA for a benchmark case study model. The results showed that the proposed framework is robust and outperforms the conventional Bayesian method in uncertainty quantification for the considered dataset.

The influence of ground motion duration on the energy based assessment of buildings with infill walls

Infill walls are often used in buildings to divide the residential area in order to meet the architectural requirements and are considered as non-bearing structural elements. In some buildings, infill walls are not used in the frames of the ground floors for commercial or other architectural purposes. Thus, vertical infill wall discontinuity is formed and it appears as an irregularity by earthquake regulations. At the same time, this situation has caused damage to the structures in some earthquakes. Nowadays, traditional seismic design based on strength and resistance is considered not an adequate way to design structures under earthquake effects. Besides, the role of ground motion duration on the seismic performance of building structures has been subject of research recently. One of the methods of defining damage in earthquake resistant design is the energy approach. For this purpose, in this study, the effect of infill walls on the seismic assessment of structures exposed to short and long duration ground motions was performed on dissipated seismic energy approach. Nonlinear time history analyses were performed in two cases, fully infilled and infilled except for the ground floor. Classification of ground motion durations is based on a threshold of 25 s of significant duration (D5-95), and ground motions were evaluated as two different recording pairs of short and long duration. Using spectrally matched short and long duration earthquake records, nonlinear time history analyses were performed for building models and the results were evaluated over hysteretic energy. The analyses showed that the hysteretic energy demands depend on both the ground motion duration and the infill wall placement in the building.

Seismic analysis of an ancient masonry palace through two simplified numerical methods

The aim of the paper is to study the reliability of simplified numerical models (SNMs) for seismic structural assessment identification accuracy. The advantages of using SNMs with respect to the traditional finite element approaches come from their commercial availability, the structural templates already implemented, and the reduced computational burden that allow the evaluation of the seismic structural assessment in some minutes instead of days. But the drawback to using SNMs alone in the study of large-scale structures is the crude accuracy justified by the simplifications they assume. This study is conducted on an actual case: the Trentacapilli palace (Bisignano, Calabria, Italy). This palace was chosen because it is subjected to foundation subsidence and includes different structural elements, allowing different kinds of SNMs to be used.

Correlation between non-spectral and cumulative-based ground motion intensity measures and demands of structures under mainshock-aftershock seismic sequences considering the effects of incident angles

One of the pivotal steps in seismic assessment of structures is the definition of functional relationships between an Engineering Demand Parameter (EDP) and a ground motion Intensity Measure (IM). This paper investigates the correlation between widely used non-spectral and cumulative-based ground motion intensity measures and corresponding engineering demand parameters for regular and irregular structures as bidirectional single-degree-of-freedom (2D-SDOF) systems. The correlation is investigated under sequential earthquakes in terms of efficiency and sufficiency, considering various seismic incident angles. Structural performance is expressed as maximum inelastic displacement, MD, maximum inelastic absolute acceleration, MA, residual displacement, RD, and hysteretic energy, EH. The results of extensive parametric analyses show that if the MD, MA, EH and RD of regular systems are considered as demand parameters, the optimal IMs in terms of efficiency and sufficiency are vsq, arms, vrs and vsq, respectively.

Pushover Analysis of Sir M Visvesvaraya Block Nmamit Nitte

Abstract: Pushover analysis is one of the most-used nonlinear static procedures for the seismic assessment of structures, due to its simplicity, efficiency in modeling and low computational time. The previous studies about pushover analysis are almost based on symmetric building structures and unidirectional earthquake excitation. This analysis is conducted to evaluate the seismic capacities of an existing asymmetric-plan building. The seismic response of RC building frame in terms of performance point and the effect of earthquake forces on multi storey building frame with the help of pushover analysis are carried out. In the present study the building frame is designed as per IS 456:2000 and IS 1893:2002. We should also go through ATC-40, FEMA 356. To get knowledge of pushover analysis we have to learn Etabs and should practice to analysis a RC building. The main objective of this study is to check the kind of performance a building can give when designed as per Indian Standards. The pushover analysis of the building frame is carried out by using structural analysis and design software ETABS (Version 19).

Pushover Analysis of Sir M Visvesvaraya Block NMAMIT NITTE

Pushover analysis is one of the most-used nonlinear static procedures for the seismic assessment of structures, due to its simplicity, efficiency in modeling and low computational time. The previous studies about pushover analysis are almost based on symmetric building structures and unidirectional earthquake excitation. This analysis is conducted to evaluate the seismic capacities of an existing asymmetric-plan building. The seismic response of RC building frame in terms of performance point and the effect of earthquake forces on multi storey building frame with the help of pushover analysis are carried out. In the present study the building frame is designed as per IS 456:2000 and IS 1893:2002. We should also go through ATC-40, FEMA 356. To get knowledge of pushover analysis we have to learn Etabs and should practice to analysis a RC building. The main objective of this study is to check the kind of performance a building can give when designed as per Indian Standards. The pushover analysis of the building frame is carried out by using structural analysis and design software ETABS (Version 19).

Linear dynamic analysis of high-rise irregular structures with or without LFRS & frictional damper

This study categorically assists in describing the behavior of Irregular structures consist of G + 20 Storey through linear dynamic analysis for seismic assessment of structures. Linear dynamic analysis or response spectrum analysis helps us to evaluate the several parameters in respect of severe responses in irregular structures. At the time of design, A well analyzed structure shows which fragile part of structure needs to give an attention at the time of design to resist and dissipate the energy of seismic force occur on a structur3e during the earthquake. Response spectrum analysis is a seismic analysis method, which shows the response of structure when a seismic load taken into an account. In this study series of sequential response spectrum analysis of High-rise irregular structures have compared with the similar structures after assigning shear walls, Steel bracings and Frictional dampers respectively, and simultaneously all the purposed structure responses have compared with a regular structure accordingly with same consideration of lateral force resisting system. The complete modelling and analysis have done by the prominent analytical FEM integrated software “ETABS” in the seismic zone IV by considering relevant data for the particular seismic zone by IS 1893 (Part-1) 2016. All the reinforcement criteria for the components of structure has been taken into consideration as per suggested by IS 13920 for the ductile design. The response parameter aims for structures due to seismic loading are in terms of Max. displacement, Storey shear. Ultimately, it was concluded that the shear wall is more desirable than the other for reducing the max. displacement with the average reduction percentage of 61.33%.

Modelling of seismic actions in earth retaining walls and comparison with shaker table experiment

This paper is concerned with the response behaviour of a retaining wall in seismic conditions from a two-dimensional perspective. The backfill was levelled behind the wall for some distance. Both the wall and the backfill were found on a stiff elastic medium. The manner in which the backfill affected the response behaviour of the wall when subject to base excitations was of interest. The wall was idealised into a linear elastic element which responded mainly in flexural actions. The novelty of the paper is in the use of shaker table testing of a scaled down model of the retaining wall and backfill to validate the accuracies of results from numerical simulations. The comparison is mainly based on displacement time - histories at the top of the wall. The alignment with displacement-based approach for the seismic assessment of structures is distinguished from many other investigations which typically put the focus on the behaviour of the backfill pressure. Laboratory testings of backfill materials including triaxial tests have been conducted to determine the value of parameters for characterising the hysteresis properties of the backfill. Calibration of backfill material model has also been shown to simulate the pre yield, post yield and damping behaviour of backfill. The ultimate objective of the paper is to present a viable means of achieving realistic and accurate modelling of the seismic response behaviour of a retaining wall and to provide data for benchmarking simplified (macro) numerical models to be developed in the future for supporting seismic design and assessment.

Piecewise incremental dynamic analysis (PIDA) based on the vector of intensity measures correlated with the structural responses

One of the main drawbacks of conventional incremental dynamic analysis (IDA) is the questionable eligibility of a selected record suite as an appropriate representative of different intensity levels according to probabilistic seismic hazard analysis. The present study proposes an alternative approach to select a suitable set of ground motions at each intensity level by considering the vector of intensity measures (IMs) correlated with an engineering demand parameter (EDP) and the associated weight vectors. Piecewise incremental dynamic analysis (PIDA) is performed using hazard-consistent record suites for the seismic assessment of structures. The PIDA results can present a more reliable prediction of the seismic performance of buildings due to the higher accuracy of this method in selecting ground motions compared to the adaptive incremental dynamic analysis (AIDA), the hazard-consistent IDA, and the conventional IDA conducted by two common record selection methods, particularly for greater values of damage states.

Probabilistic seismic assessment of reinforced concrete bridges using simulated records

A prominent challenge in performance-based earthquake engineering is to select a suitable set of ground motions records with which to perform probabilistic seismic assessment of structures. The most common approach for engineering purposes is to employ actual recordings of worldwide events, given that large earthquakes do not occur frequently hence regional recordings of such events are usually not widely available. To address this not that uncommon issue, regionally simulated ground motions using a stochastic finite-fault method have been proposed as an alternative to real records. This study aims to explore the use of simulated records through a stochastic finite-fault method in probabilistic seismic assessment frameworks for reinforced concrete bridges, when compared to using real records. Direct seismic losses for a case-study existing bridge and a bridge portfolio are estimated and compared, as the reference risk metric. Finally, the similarities between seismic demands, obtained using both real and simulated record sets, are quantified and discussed via statistical hypothesis testing, resulting fragility curves and expected annual losses. The results show how simulated records can be a promising alternative to real records, becoming particularly useful in the absence of available recorded ground motions with specific seismogenic features.

Reliability-based seismic performance of masonry arch bridges

Seismic structural assessment of masonry arch bridges is essential due to their cultural, economic and strategic importance and vulnerability. A realistic and rigorous structural assessment is necessary in order to protect the bridges and use resources carefully. At this time, there are no standardised or widely accepted assessment procedures, and the performance criteria for masonry arch bridges are not available. This study presents an overarching reliability-based seismic assessment methodology based on analytical modelling, laboratory testing and probabilistic assessment. It investigates the performance criteria concept and proposes performance limit states. The methodology is applied to a historical masonry arch bridge in Turkey. To consider rigorously the uncertainties in material properties and seismic input, probabilistic nonlinear analyses are conducted using a detailed 3D finite element model. The results are combined with the proposed limit state definitions to generate the capacity and demand distributions. Both distributions are used in Monte Carlo simulation and First-Order Reliability Method (FORM) to estimate the probability of exceedance and reliability indexes for each limit state. The proposed probabilistic assessment methodology will be a useful approach to obtaining more reliable information about masonry arch bridges' expected seismic performance and for better-informed decision-making, especially when designing intervention actions and post-earthquake scenarios.

Normalized residual displacement spectra for post-mainshock assessment of structures subjected to aftershocks

Residual displacement, as a significant measure of structural inelasticity, is effectively used in post-earthquake seismic assessment of structures. This demand can be considered for seismic evaluation of structures under multiple earthquakes. This study introduces a simple and novel index to predict the residual displacement of mainshock-damaged structures against subsequent aftershock. The proposed index is defined as a ratio between residual displacement of damaged structures against aftershock and peak inelastic displacement of intact structures under mainshock. In this study, constant-strength spectra based on the index are developed considering the effects of important structural characteristics and also significant seismic parameters. Moreover, analytical equations are presented to predict the proposed index for bi-linear single-degree-of-freedom (SDOF) systems considering both the effects of positive and negative polarities of aftershock. Furthermore, an equation is suggested to estimate the peak inelastic displacement of intact systems under mainshock, which is required to compute the index.

Fragility functions for reinforced concrete columns incorporating recycled aggregates

Using recycled aggregates in the production of structural members is a relatively new application that has the potential to become a mainstream practice with effective green policies. Therefore, performance-based seismic assessment of structures constructed using recycled aggregates gains importance. Fragility curves, cumulative distribution functions that represent the probability of being in or exceeding a threshold for a selected engineering demand parameter, can be used in risk evaluation of these structures.In this study, fragility functions are generated by compiling the data of reinforced concrete columns incorporating recycled concrete aggregate available in the literature. The data is first evaluated through physical damage states, and three different damage states, namely Damage State 1, Damage State 2 and Damage State 3, are defined. Each damage state is then mapped to a certain repair category (cosmetic repair, structural repair or structural enhancement) so that damage can be defined in terms of economic loss, which would provide a road map in the disaster management decision making process. Drift ratio is selected as the engineering demand parameter since generally displacement demand is taken into account in the evaluation of seismic performance of structures. Based on the results of the statistical analysis, the median drift ratio values of 0.30%, 1.21%, and 3.25%, and logarithmic standard deviations of 0.95, 0.42, and 0.45 are determined for Damage State 1, Damage State 2, and Damage State 3, respectively, for columns incorporating recycled concrete aggregates. Furthermore, the effect of parameters on the relationship between drift demand and damage is investigated. In addition, seismic performances of the columns are discussed in terms of their ductility capacity. It is also shown that the ductility limit defined according to Paulay and Priestley (1992), and UBC (1997) for the reinforced concrete columns made of natural aggregate concrete is valid also for the columns made of recycled aggregate concrete.Besides, fragility functions are also generated for columns made of natural aggregate concrete in order to compare damage progression in columns made of recycled aggregate concrete with the aim of identifying the variability in drift demand. From the comparison of the fragility curves of these columns, it is found that at the same drift ratio, damage exceedance probabilities of both column types are similar for Damage State 1 and Damage State 2. However, for Damage State 3, at the same drift ratio, the damage exceedance probability of columns incorporating recycled concrete aggregates is higher than that of the columns made of natural aggregate concrete owing to relatively lower lateral load capacity of these columns.

Investigation on residual displacements for SDOF systems with various initial viscous damping models

Nonlinear time history analysis (NTHA) is widely used in estimation of post-earthquake residual displacement demands. However, the choice of initial viscous damping models in NTHA has attracted insufficient attention in study of residual displacements. The more versatile viscous damping model similar to the tangent-stiffness proportional Rayleigh damping commonly used in multi-degree-of-freedom (MDOF) systems is utilized in NTHA of single-degree-of-freedom (SDOF) systems. With different combinations of mass proportional and tangent-stiffness proportional damping terms, the significance of the choice of initial damping models is examined in terms of energy dissipation and residual displacement demands. The residual displacement ratio, defined as the ratio of residual displacements to elastic spectral displacements, is computed for constant-strength SDOF systems when subjected to an ensemble of 240 earthquake ground motions. The results are statistically organized to investigate the effect of initial viscous damping models on residual displacement demands. The difference in residual displacement ratios for various damping models is found to be significant, and dependent on natural periods, relative lateral strength, post-yield stiffness, unloading stiffness degradation and initial damping ratios. The effect of these factors on residual displacement demands of SDOF systems with tangent-stiffness proportional damping, which is confirmed to be most appropriate for nonlinear analysis, is also examined. Finally, the constant-strength residual displacement response spectra are constructed for seismic assessment of structures.

A novel procedure for the assessment of the seismic performance of frame structures by means of limit analysis

Limit analysis is a computationally efficient tool to assess the resistance and the failure mode of structures but does not provide any information on the displacement capacity, which is one of the concepts which most affects the seismic safety. Therefore, since many researchers did not consider limit analysis as a possible tool for the seismic assessment of structures, its widespread employment has been prevented. In this paper this common belief is questioned and the authors show that limit analysis can be useful in the evaluation of the seismic performance of frame structures. In particular, to overcome the limitation on the possibility to evaluate the displacements of a structure based on a limit analysis approach, an approximated capacity curve is reconstructed. The latter is based on a limit analysis strategy, which takes into account the second order effects, and evaluates the displacement capacity considering a post-peak softening branch and a threshold on the allowed plastic rotations. Then, based on this simplified capacity curve, an equivalent single degree of freedom system is defined in order to assess the seismic performance of frame structures. The proposed simplified strategy is implemented in a dedicated software and the obtained results are validated with well-established approaches based on nonlinear static analyses, showing the reliability and the computational efficiency of this methodology.

System-level seismic resilience assessment of reinforced masonry shear wall buildings with masonry boundary elements

The concept of seismic resilience plays an important role in seismic assessment of structures as it assesses the capability of a system to withstand an unwanted event, such as earthquakes, by estimating the losses and determining the system’s functionality and sustainability during and after such event. In this study, a framework was utilized to assess the seismic resilience of Reinforced Masonry Shear Wall (RMSW) buildings as well as studying the impact of incorporating Masonry Boundary Elements (MBEs) at the ends of RMSW. To achieve this goal, a ten-story RMSW building was numerically modelled in OpenSees to assess the seismic performance and resilience of the system when adding confined MBEs. The selected building is located in Montreal, Canada, and initially designed to be built having rectangular walls. Subsequently, the walls were redesigned to integrate MBEs at their outermost fibre to help increase the ductility and strength of the RMSWs. A full 3D wide-column macro-modelling approach was used to simulate the dynamic response of the archetype building. Validation of the modelling approach was done against available experimental tests as an initial step to ensure the robustness of the model in predicting the inelastic response of the building. Subsequently, the models were analyzed against multiple ground motion records using Incremental Dynamic Analysis to identify the initiation of collapse alongside developing the fragility curves of the building. The system-level seismic performance of the building was assessed after incorporating MBEs. The resilience of the building was assessed using the developed fragility functions, and a comparison was made to highlight the effect of using MBEs on the response of the studied RMSW building. The results showed a significant enhancement in the seismic resilience of the building by using confined MBEs at the shear walls’ extreme.