Seismic Performance Assessment Research Articles

On the seismic performance of straight integral abutment bridges: From advanced numerical modelling to a practice‐oriented analysis method

AbstractThe seismic performance of integral abutment bridges (IABs) is affected by the interaction with the surrounding soil, and specifically by the development of interaction forces in the embankment‐abutment and soil‐piles systems. In principle, these effects could be evaluated by means of highly demanding numerical computations that, however, can be carried out only for detailed studies of specific cases. By contrast, a low‐demanding analysis method is needed for a design‐oriented assessment of the longitudinal seismic performance of IABs. To this purpose, the present paper describes a design technique in which the frequency‐ and amplitude‐dependency of the soil‐structure interaction is modelled in a simplified manner. Specifically, the method consists of a time‐domain analysis of a simplified soil‐bridge model, in which soil‐structure interaction is simulated by means of distributed nonlinear springs connecting a free‐field ground response analysis model to the structural system. The results of this simplified method are validated against the results of advanced numerical analyses, considering different seismic scenarios. In its present state of development, the proposed simplified nonlinear model can be used for an efficient evaluation of the longitudinal response of straight IABs and can constitute a starting point for a prospective generalisation to three‐dimensional response.

Seismic Vulnerability Analysis of Masonry Structures Built with Disassembled Brick Wall Sections

Disassembling brick wall pieces into brick wall sections and constructing masonry buildings with disassembled brick wall sections (DBWSs) can reduce construction waste production at source and help achieve carbon peak and carbon neutrality. A finite element model (FEM) for typical MSBD is established based on the calibrated finite element analysis method to evaluate the seismic performance of masonry structures built with disassembled brick wall sections (MSBD). Subsequently, the peak ground acceleration is selected as the ground motion intensity index, and the maximum inter-story displacement angle is chosen as the structural damage index. The 20 ground motion records are selected and scaled by peak acceleration in 0.2 g steps to form 120 structure-ground vibration samples for incremental dynamic analysis (IDA) and seismic vulnerability analysis. The IDA results indicated that with the gradual increase in peak ground acceleration, the maximum inter-story displacement angle increases and the model transits from the elastic stage to the elastoplastic stage. Because the characteristics of ground motion records are different, the order of structural plasticity development will be different and the number of ground motion records needs to be considered in the seismic performance assessment. The calculation model will not collapse under the 7 and 8 degree design-based earthquake and the probability of moderate and severe damage of the structure under the rare earthquake is minimal, according to the seismic vulnerability curves. The seismic vulnerability analysis results indicate that MSBD has good seismic performance under earthquakes and meets the requirements of “perfect subjected to frequent earthquake, reparable subjected to design based earthquake, no collapse subjected to rare earthquake.” The seismic vulnerability analysis based on probability statistics can provide a reference for seismic design and evaluation of earthquake damage.

Fragility curves of Italian school buildings: derivation from L’Aquila 2009 earthquake damage via observational and heuristic approaches

Recent seismic events worldwide have demonstrated the high vulnerability of existing school buildings and the urgent need to have reliable tools for the rapid seismic performance assessment and damage and loss quantification. Indeed, the significant damage observed on structural and non-structural components may have a significant impact in terms of direct and indirect losses making critical the recovery of stricken communities. Although a significant amount of work has been done in developing fragility curves for the residential building stock, only few contributions clearly refer to school buildings that significantly differ in terms of the main characteristics from the residential ones. This research work proposes fragility curves for reinforced concrete and unreinforced masonry public school buildings typical of the Italian building stock, based on the damage observed in the aftermath of the 2009 L’Aquila earthquake. A comprehensive and unique database including data on damaged and undamaged school buildings (2037 records) in the Abruzzo region was built using data from four different sources. Due to limited amount of data, the fragility curves can be very sensitive to the method adopted for their derivation, thus three different approaches (i.e. empirical, empirical-binomial, heuristic) are considered in the paper and the results are compared. Finally, a direct comparison with fragility curves available in the literature for the Italian residential building stock is presented.

Seismic performance evaluation of code compliant and non-compliant RC walls

ABSTRACT Pakistan’s unique geographical location has made it seismically vulnerable. Owing to this, recentearthquakes have revealed the susceptibility of the existing reinforced concrete (RC)buildings in Pakistan. This has raised concerns about the structural performanceof RC buildings because mostmid-rise RC buildingsin Pakistan have shear wall lateral force resisting systems. In this study, a survey ofexisting mid-rise RC buildings in Pakistan's capital territory is used todevelop a database of existing RC shear walls. By using this database, this research aims to provide a seismic performance assessment of existing RC shear wallsto determine their deficiencies and provide necessary experimental data for retrofitting. TwoRC shear wall specimens SW1 and SW2, representing the characteristics of existingRC shear walls are testedunder quasi-static loading. The seismic response of the existing RC mid-risewalls isassessed through the mode of failure, hysteretic behavior, energy dissipation,flexure and shear stiffness,and curvaturedistribution.The findings reveal that the existing mid-rise RC walls in the region did notsatisfy the performance criteria recommended by different seismic codes. Hence a comprehensive retrofitting strategy with building codecompliance are prerequisites to avoid infrastructural and economic losses dueto seismic activity.

Enhancing seismic performance of rigid and semi-rigid connections equipped with SMA bolts incorporating nonlinear soil-structure interaction

Nowadays, using smart connections can improve the performance of buildings with some recentering features that are from the superelastic behavior of Shape Memory Alloys (SMAs). It seems that there is different rigidity between the designed connection and the real one in Steel Moment-Resisting Frames (SMRFs), which can be considered as a problematic issue due to the importance of connections in seismic performance assessment. This paper aims to investigate the seismic limit-state capacities of rigid and semi-rigid connections implemented in the 3-Story, 5-Story, 7-Story, and 9-Story SMRFs considering the nonlinear Soil-Structure Interaction (SSI) effects. A Tcl programming code was developed to model semi-rigid connection and SSI effects using Opensees. Incremental Dynamic Analyses (IDAs) were employed to assess the seismic performance levels of SMRFs considering Near-Fault Pulse-Like (NF-PL) and Near-Fault No-Pulse (NF-NP) records suggested by FEMA-P695. The results showed that assuming semi-rigid connections with rigidity of 80%, 70%, and 60%, significantly decreased the median values of IDA curves compared to rigid connection. Considering the SSI effects can considerably decrease the Sa(T1) values of IDA curves and seismic collapse probability in all soil types; therefore, it is suggested to assume the real condition of the structure by modeling the connection rigidity and the SSI effects. It can be concluded that SMA bolts have the ability to improve the seismic performance of connection to compensate the lack of rigidity in semi-rigid connections of SMRFs; as well as, they can be used as a retrofitting strategy for existing buildings.

Seismic Performance of Internal Partition Walls with Slotted and Bracketed Head-Tracks

ABSTRACT This paper presents the concept, design, construction and seismic performance assessment of internal partition walls with novel slotted and bracketed head-track details. In the slotted head-track walls, the anchors connecting the wall to the slab above are intended to slide within the slot to accommodate the desired in-plane drifts. On the other hand, in the bracketed head-track walls, the story-drift demands are accommodated by sliding of the bolt and flexing of the plastic brackets attached to the slots. In this paper, bi-directional behaviour of a novel flexible bracket is experimentally characterised and a number of wall sub-assemblies with the slotted and bracketed connection details are tested under quasi-static cyclic loading to investigate their seismic performance. The walls with slotted details showed the first signs of damage requiring repair at 0.78% drift. In contrast, when brackets were attached to the slots, the wall remained intact up to 4% drift, demonstrating a superior seismic resiliency.

Effect of interior gravity framing system and composite floor slab action on the lifetime seismic risk assessment of steel frame buildings subjected to mainshock–aftershock sequence

The structural analysis practices of steel moment-resisting frame buildings often neglect the participation of the interior gravity frames and composite floor slab action in their lateral strength and stiffness. In addition, the effects of aftershocks are frequently omitted in steel frame buildings’ seismic performance evaluations. This study investigates the effects of structural modeling assumptions and the incorporation of aftershocks on the seismic vulnerability and time-dependent lifetime seismic risk for a group of steel moment-resisting frame buildings. Three ductile steel moment-resisting frame buildings of four, eight, and twelve stories are examined in this study. The results indicate that the seismic performance of steel special moment-resisting frame buildings is substantially underestimated when based on structural models that ignore additional sources of lateral stiffness and strength owing to the interior gravity frame system and the composite floor slab action. In addition, when ignoring aftershocks from the seismic performance assessment, the possibility of catastrophic failure could be underestimated by a factor of 11 at the end of an assumed 50-year lifetime for the steel frame buildings, underscoring the need to account for aftershock effects in evaluating the collapse safety of the selected buildings.

Probabilistic seismic performance assessment of offshore jacket structures as a basis for engineering decision-making

Jacket structures play an ever-increasing role in meeting the world’s burgeoning energy demand by providing support structure for exploiting offshore wind energy and oil and gas resources. Many of these structures are past their design lifetimes, and thus may have suffered significant degradation, highlighting the importance of investigating their earthquake response in seismically active regions. This study investigates the seismic performance of a typical offshore jacket platform, denoted as baseline structure, as well as four versions with two longer (25% and 50% larger) and two shorter (25% and 50% smaller) natural vibration periods accounting for two levels of degradation and retrofit effects on structural performance. For each case, eleven ensembles of ground motions compatible with the site’s seismic hazard are selected using the generalized conditional intensity measure methodology. The loading uncertainty is incorporated in the performance assessment procedure via probabilistic seismic demand analysis and the demand hazard is quantified. The results provide valuable information regarding reliability of these structures both at design stage and during service life, which can aid decision-making around rehabilitation of older platforms, the suitability of reusing obsolete platforms beyond service lifetime, and risk-based design of new platforms.

A Parametric Study of Fire-Damaged Reinforced Concrete Columns under Lateral Loads

Columns are the structural members of buildings that ensure structural stability. A fire can severely affect the columns' structural performance by degrading the properties of their constituent materials, thereby reducing the strength capacity, stiffness, and stability. In seismic zones, the knowledge of the post-fire behavior of these elements is a fundamental requirement for a realistic seismic performance assessment. This study utilized numerical analysis using the parametric fire model of Eurocode-1 to estimate the post-fire axial and lateral performance of reinforced concrete columns. In the first step, the axial load-bearing capacity was evaluated from a parametric study for cantilever columns. In the second step, the lateral load capacity, force-displacement behavior, stiffness, ductility, energy dissipation capacity, and residual displacements were estimated to determine the impact of fire damage on the behavior of columns under lateral loads. The results showed that both the lateral load capacity and the ductility of the reinforced concrete columns decreased significantly due to fire exposure. This also indicated that fire damage decreases the vertical load-bearing capacity, and the reduction in lateral capacity was attributed to the loss of concrete's compressive strength. The column characteristics that significantly influence the residual response behavior were identified as section size, column height, axial load ratio, and concrete's compressive strength.

Bridge Network Seismic Risk Assessment Using ShakeMap/HAZUS with Dynamic Traffic Modeling

Bridge infrastructures are critical nodes in a transportation network. In earthquake-prone areas, seismic performance assessment of infrastructure is essential to identify, retrofit, reconstruct, or, if necessary, demolish the infrastructure systems based on optimal decision-making processes. As one of the crucial components of the transportation network, any bridge failure would impede the post-earthquake rescue operation. Not only the failure of such high-risk critical components during an extreme event can lead to significant direct damages, but it also affects the transportation road network. The consequences of these secondary effects can easily lead to congestion and long queues if the performance of the transportation system before or after an event was not analyzed. These indirect losses can be more prominent compared to the actual damage to bridges. This paper brings about seismic performance assessment for the Cyprus transportation network from which the decision-making platform can be modeled and implemented. This study employs a seismic hazard analysis based on generated USGS ShakeMap scenarios for the risk assessment of the transportation network. Furthermore, identification of the resiliency and vulnerability of the transportation road network is carried out by utilizing the graph theory concept at the network level. Moreover, link performance measures, i.e., traffic modeling of the study region is simulated in a dynamic traffic assignment (DTA) simulation environment. Finally, for earthquake loss analysis of the bridges, the HAZUS loss estimation tool is used. The results of our investigations for three different earthquake scenarios have shown that seismic retrofitting of bridges is a cost-effective measure to reduce the structural and operational losses in the region.

Seismic performance assessment of a historical masonry-infilled RC building located in the historical peninsula of Istanbul (1940s)

The current paper presents a seismic performance evaluation methodology for masonry-infilled RC buildings based on nonlinear analyses. The entire process is illustrated using a case study of a university building constructed in the 1940s. Firstly, a finite element model of the building representing its existing state was prepared based on the current seismic codes. In the second stage, the seismic performance of the building was determined by pushover analysis. Since the seismic performance of the current building was found to be inadequate, a retrofitting proposal was prepared. The model of the retrofitted building was then examined to determine the effectiveness of the proposed retrofitting techniques. The methodology presented in the study is important in seismic analysis of RC + masonry dual system buildings before and after the retrofitting practice.

Influential Article Review — The Effect of Seismic Excitation on the Passive Stiffness of a Seismically Isolated Bridge Deck

This paper examines the performance of modified bridge elements under simulated earthquake excitations. We present insights from a highly influential paper. Here are the highlights from this paper: This study is on the seismic performance assessment of a seismically isolated bridge structure with passive stiffness modification implementation. Performance of the passive stiffness modification approach is compared with semi-active control implementation on the bridge deck. El Centro NS (north-south) and Kobe EW(east￾west) earthquake excitations are used for the dynamic simulations of the passive case. Results are given in a comparative way for the uncontrolled bridge deck, passive stiffness modification implemented and semi￾actively controlled, seismically isolated bridge deck (Yanik & Aldemir, 2018). Frequency dependent acceleration, velocity and displacement response transmissibility ratios are defined to examine the results. For our overseas readers, we then present the insights from this paper in Spanish, French and German.

Seismic assessment of a railway masonry arch bridge using sensor-based model updating

A large proportion of Iranian railway bridge assets comprises masonry arch bridges, which have been in service for over 70 years. Seismic assessment of such structures is very important, particularly for highly seismic regions. This study assesses the seismic performance of Veresk masonry arch bridge, the longest masonry arch bridge in the Iranian railway network (span length 99 m), spanning a valley 110 m deep, through reliable sensor-based model updating. Dynamic tests are conducted using a test train, composed of six-axle locomotives and four-axle freight wagons, which travels across the bridge; the vibration response of the instrumented bridge is subsequently measured. A high-fidelity three-dimensional finite-element model of the bridge is developed and updated using the measured vibration characteristics: mid-span displacements and natural frequencies. Finally, a seismic performance assessment of the bridge is performed using non-linear static and dynamic analyses for two seismic hazard levels with return periods of 150 and 1000 years. It is found that, for the hazard level with a return period of 150 years, both non-linear static and dynamic analyses give very similar results. However, for the seismic hazard level with a return period of 1000 years, the results of the static analysis are more conservative.

Seismic performance upgrade of substandard RC buildings with different structural systems using advanced retrofit techniques

There has been ongoing deliberation to arrive at promising retrofit strategies for pre-seismic code reinforced concrete (RC) structures. Against this backdrop, the research reported in this study puts forth solutions by focusing on advanced retrofit approaches for improving the seismic performance of substandard RC buildings with structural systems common to medium seismicity regions. High-performance reinforced concrete (HPRC) jacket application and self-centering energy dissipative (SCED) braces are the contemporary retrofit alternatives prioritized in this study to upgrade RC structural systems deficient in stiffness, strength and/or ductility. While these retrofit techniques were previously investigated at the member level, this study focuses on implementing thin-HPRC jacket applications, innovative outrigger-belt truss SCED bracing systems, and hybrid approaches on three-dimensional (3D) fiber-based numerical models representing substandard RC structures with different heights. Inelastic pushover analyses and multi-record dynamic response simulations are conducted to assess the retrofit alternatives by monitoring several local damage indices (LDIs) and the related global damage measure (GDM). The study confirms the effectiveness of retrofit measures for a moment-resisting frame building (MRF) deficient in lateral capacity and a high-rise shear wall (SW) building with insufficient global ductility. The presented systematic methodology accounts for the redistribution of seismic demands after retrofitting critical elements and enables selecting effective seismic retrofit solutions, namely SCED bracing system for MRF structure and hybrid retrofit for the high-rise SW building, using probabilistic seismic performance assessment along with cost and practical considerations.

Seismic Performance Analyses of Pile-supported Transmission Tower-line Systems Subjected to Depth-varying Spatial Ground Motions

ABSTRACT Past major earthquakes have witnessed extensive pile-supported transmission tower-line systems (PSTLs) failing, which highlights the great susceptibility of PSTLs to damage from earthquakes. However, a comprehensive literature review in seismic analysis of PSTLs reveals that two critical aspects, i.e. soil–structure interaction (SSI) and depth-varying spatial ground motions (DVSGMs), have been completely overlooked in numerous previous studies. To be specific, pile-supported transmission towers are generally assumed to be fixed to the ground surface and are excited using uniform ground motion inputs. Such analytical schemes may result in severe misestimates of seismic response predictions of PSTLs. Within this context, the main objective of the present study is to accurately assess the seismic performance of PSTLs by considering SSI and using DVSGMs as inputs. For this purpose, an existing prototype PSTL is firstly selected and the corresponding three-dimensional finite element model is created in ABAQUS software, in which SSI is simulated by the Beam on Nonlinear Winkler Foundation (BNWF) model. Then, the three-dimensional DVSGMs are stochastically synthesized based on the computed ground motion transfer functions (GMTFs) of local sites. Next, seismic performance of the PSTL with SSI, including dynamic responses, ultimate bearing capacity, and failure mechanism, is assessed using the generated DVSGMs as seismic inputs. Finally, a parametric study is conducted to comprehensively examine and discuss the influences of SSI, seismic excitation types, coherence loss, and local site conditions on seismic performance of the PSTL. Numerical results show that seismic performance of PSTLs can be affected significantly by the above mentioned influencing factors. This research is expected to offer a meaningful reference to seismic performance assessments of PSTLs.

Seismic Performance Assessment of Semi Active Tuned Mass Damper in an MRF Steel Building Including Nonlinear Soil–Pile–Structure Interaction

Seismic Performance Assessment of Semi Active Tuned Mass Damper in an MRF Steel Building Including Nonlinear Soil–Pile–Structure Interaction

Analytical Structural Health Monitoring of Shear Wall Building

Abstract: Structural health monitoring techniques have been utilized to inspect the current conditions of structures, as well as their post-earthquake performances. The dynamic characteristics of a building, such as modal periods, shapes and damping ratios can be obtained by analysing the ambient vibration data. It is well-known that dynamic characteristics generated from the finite element model (FEM) and vibration data, even for the intact building, show remarkable differences. Assumptions made in the FEM are one of the main reasons for those differences. To examine feasible solutions to such problems mentioned above Here an attempt has been made to study the behaviour of different structures of reinforced concrete with different heights with and without shear walls. Coupled shear walls have also been studied to understand the comparative merit or demerit of framed structures with shear wall structures. Studies have been carried out on sample model structures and analysis has been carried out by ETABS software. It has been ensured to consider sample models that represent the current practices in structural design to include different structural configurations. Models having varied structural configurations like framed, shear wall, coupled shear wall, central core shear wall, core in core etc. have been taken into consideration. The inherent asymmetry present in the structures have also been dealt. Natural frequencies and mode shapes of the structure were determined by frequency domain decomposition method. In addition, identification of damping was performed due to the fact that damping ratio plays a significant role in the magnitude of inter-story drift during an earthquake. The FEM of the structure was constructed based on design drawings and updated to represent the real mode shapes and frequencies of the structure. By using the updated FEM with standard damping ratio in Indian Earthquake Code and the identified damping ratio, seismic performance assessment of the building for a possible earthquake.

Seismic Performance Assessment of Wide Pile-Supported Wharf Considering Soil Slope and Waveform Duration

Pile-supported wharf (PSW) is one of the primary port structures and is often damaged by earthquakes. To mitigate the risk of seismic damage to a PSW, its seismic performance should be thoroughly assessed. This study aimed to examine the impact of ground displacement on the seismic performance of PSW with a mild soil slope. We performed soil-structure system finite element analysis targeting a wide PSW. The analysis is divided into two scenarios. In the first scenario, the PSW was modeled without regard for the soil slope, whereas the second scenario considered the soil slope. Two waveforms that matched the target spectral acceleration were used to study the effects of the waveform duration on the seismic response of PSW. The analysis results revealed substantial influences of soil slope displacement as well as differences in waveforms on PSW’s seismic performance.

Seismic Performance Assessment of a Pin-bearing Restraint System for Curved Bridge

The traditional restraint systems limit the deformation of curved bridge under temperature load, which results in radial and tangential secondary internal forces in the bridge. This paper proposes a pin-bearing restraint system (PBRS) for curved bridge, which can relax the rotational deformation of curved bridge under temperature load. Its configuration and working mechanism are illustrated. The finite element model of a curved bridge with PBRS is established using ANSYS software, and nonlinear time history analysis is conducted. The pounding force and pounding number between pin and slot under ground motion are analyzed. The pin stiffness, the gap and the ratio of upper structure mass to lower structure mass are selected for parametric study. The results show that the pounding force and pounding number present dramatic changes with pin stiffness. As the pin stiffness increases, the pounding force presents a logarithmic linear tendency, and the pounding number shows a reduce tendency. Gap has little influence on pounding force and pounding number. The radial pounding force and pounding number increase with the increase of mass ratio.

Dynamic and probabilistic seismic performance assessment of precast prestressed reinforced concrete frames incorporating slab influence through three-dimensional spatial model

Dynamic and probabilistic seismic performance assessment of precast prestressed reinforced concrete frames incorporating slab influence through three-dimensional spatial model