Post-earthquake Performance Research Articles

Seismic performance of a retrofitted heritage unreinforced masonry building during the 2010/2011 Canterbury earthquakes

The Heritage Hotel (formerly Old Government Buildings) is one of the architectural heritage icons of Christchurch, New Zealand. Seismic retrofitting was undertaken on the structure in 1995 to achieve the earthquake loading provisions of the 1992 standard for design loadings (NZS 4203:1992). This building is a distinguished 1909 unreinforced masonry Italian High Renaissance palazzo building. The retrofit work included the installation of new lateral load-resisting structural systems, refurbishment of individual building elements, and partial building demolition with a total cost of approximately NZ$3.75 million. Detailed observations following the 2010/2011 Canterbury earthquakes showed that the building was subject to only minor damage during the September 2010 earthquake, whereas the February 2011 event caused some damage to exterior stonework and flooding in the basement due to liquefaction. This damage was easily repaired, and the building was fully functional by September 2013. Reported herein are details showcasing the success of the seismic retrofit and post-earthquake performance observations.

Multivariable Analysis of Transport Network Seismic Performance: Mexico City

In densely populated urban areas, predicting the post-earthquake performance of a transport network is a particularly challenging task that requires the integration of modeled structural seismic response, damage scenarios, and resulting traffic behavior. Previous approaches assessing the vulnerability and performance of networks after earthquakes have not succeeded in capturing and estimating the interdependencies between seismic risk parameters and key traffic behavior variables. This paper presents a methodology, based on data analysis and optimization, where the dynamic traffic modeling and probabilistic seismic hazard assessment are coupled, to link and characterize key network performance variables after extreme earthquakes and establish a multivariable seismic performance measure. The methodology is used to study the transport network in the southern part of Mexico City for a set of scenarios. The seismic environment is established through uniform hazard spectra derived for firm soil. Damage to structures is estimated considering site response and using fragility functions. Dynamic traffic modeling is developed to simulate damage-induced road closures and resulting in traffic variations. Post-earthquake network performance is evaluated through data envelopment analyses, obtaining sets of seismic performance boundaries, and seismic performance maps. The methodology offers a quantitative tool with applications in the planning of urban areas that are sustainable and seismic resilient.

Seismic assessment of rocking timber walls with energy dissipation devices

The use of rocking walls with seismic fuses is an efficient solution for mass timber structures. This paper presents and compares mass timber wall systems with different types of seismic fuses. These devices range from conventional pinching connectors to self-centring friction connections. Pros, cons and performance measures of each system are described and discussed. Moreover, a preliminary design procedure based on the Direct Displacement Based Design (DDBD) approach is used to specify and size the damping devices. This approach was chosen to assure that the lateral displacements of the systems are appropriately controlled respecting the considered damage limit states.Numerical models are accordingly developed and subjected to non-linear static pushover and dynamic time-history analyses. The results are discussed in relation with the performance objectives considered for different systems. The results confirmed that the use of low damage friction connections as a substitute for traditional pinching connectors could considerably improve the seismic performance of mass timber structures. Nevertheless, with some of these systems, there is potential for having residual displacements that could compromise the post-earthquake performance of the system.

Seismic loss and resilience assessment of single-column rocking bridges

This study focuses on structural systems, which are particularly attractive for bridge design. Specifically, it investigates the seismic performance of single-column bridges, which are either conventionally designed, with the column monolithically connected with the ground (i.e. fixed-base), or designed with the column-footing system able to uplift and exhibit planar rocking motion during an earthquake. Although various researchers have studied the examined structures in terms of their seismic fragility, their seismic losses, post-earthquake functionality and resilience have received less attention. This paper redirects our attention to the main benefits of rocking design over the conventional (fixed-base) design in the aftermath of severe seismic hazard scenarios. The analysis reveals the considerably mitigated (short-term and long-term) seismic losses of the rocking structure compared to the pertinent losses of the fixed-base structure. In addition, the results show the remarkable functionality and resilience of the rocking structure after all the examined seismic hazard scenarios. Importantly, this work unveils that the post-earthquake financial benefits of the rocking structure can be further increased when the structure is carefully designed. In particular, even a small modification of its slenderness can lead to a substantial enhancement of its post-earthquake performance. The above findings illustrate the potential of the rocking structural system as an alternative seismic design paradigm for bridges and serve as the basis for a more rational and holistic seismic assessment framework of single-column rocking bridges.

Seismic study of a widened and reconstructed long-span continuous steel truss bridge

For those steel bridges built decades ago, widening and reconstruction is an alternative and effective strategy to improve their traffic capacity. Seismic study of a widened and reconstructed long-span continuous steel truss bridge is presented in this paper. The width and weight of the bridge deck is therefore significantly increased, but the pile foundations cannot be strengthened because of the construction restriction. As a main traffic line crossing Huangpu River in Shanghai, post-earthquake performance of uninterrupted service function and the lack of ductile components exclude the ductility seismic design of the bridge, therefore the seismic isolation design using friction pendulum bearings is an option. Key design parameters and the comprehensive isolation effects are studied to provide necessary technical supports for the seismic design of the widened and reconstructed bridge. Then, a notable pile cap vibration leading to an unfavourable seismic performance of the pile foundation is observed, and parametric analyses of the possible influence factors are further studied based on a simplified two-degree-of-freedom model of the bridge deck-pile cap interactive structure. On the basis of the achieved influence rules, design suggestions to improve the seismic performance of the pile foundation are proposed consequently.

Seismic resilience assessment of emergency departments based on the state tree method

Hospital emergency departments are highly important systems and treat injured people during earthquakes. It is essential that their functionality is maintained during or recovered immediately after a disastrous earthquake; this is referred to as seismic resilience. A systematic analysis of the involved components and their influence on the functionality are required to quantify the functionality and seismic resilience. A number of studies have analyzed emergency departments under normal operating conditions using various system analysis methods. However, there are few studies on the post-earthquake performance of such systems. To this end, we propose an evaluation framework based on the state tree method to quantify the component’s influences on the functionality and the seismic resilience from an engineering perspective. A typical emergency department is analyzed, and the state tree model is developed. The component contribution to the functionality is explicitly expressed using the fault tree method and the failure transfer mechanism is determined by success paths. The functionality is thus defined as the ratio of successful paths to total possible paths. The system fragility is then calculated based on the full probability theory and the results are used to validate the simulation method. The critical components that significantly affect the functionality and the recovery can be identified while considering a practical repair process. Finally, the resilience curve of the emergency department is developed based on the fragility of the components. The effectiveness of the proposed method for the functionality quantification and the resilience evaluation is fully demonstrated.

Damage observations and remedial options for approximately 1500 legged and flat-based liquid storage tanks following the 2016 Kaikōura earthquake

Detailed inspections of numerous wineries located in New Zealand’s Marlborough region were conducted following the 2016 Kaikōura earthquake. The subject region contains a wide variety of wineries with a global reputation for its wine production. Observations documented and discussed herein highlight the post-earthquake performance of the 684 legged and 895 flat-based stainless-steel wine tanks. Damage data revealed that the legs of legged wine tanks are the most vulnerable element of the legged wine tanks. Earthquake-related damage to the anchorage system was the most commonly documented mode of failure for the flat-based tanks. Damage to tanks with different anchorage systems was also investigated herein, where it was noticed that tanks equipped with energy dissipation devices performed much better than other tanks. The comparison of remedial options for the legged wine tanks and flat-based tanks revealed that skirt extension of damaged legged wine tanks and the replacement of these tanks with flat-based tanks was a common procedure that was performed following the recent earthquakes in New Zealand.

A New Method to Evaluate the Post-Earthquake Performance and Safety of Reinforced Concrete Structural Frame Systems

This study examines the relation between maximum seismic displacements and residual displacements for reinforced concrete building structures. In order to achieve a reliable relationship between these critical structural parameters for the seismic performance of concrete buildings, an extensive parametric study is conducted by examining the nonlinear behavior of numerous planar framed structures. In this work, dynamic inelastic analyses are executed to investigate the seismic behavior of two sets of frames. The first group consists of four planar frames which have been designed for seismic and vertical loads according to modern structural codes while the second group also consists of four frames, which have been designed for vertical loads only, in order to examine older structures that have been designed using codes with inadequate seismic provisions. These two sets of buildings are subjected to various earthquakes with different amplitudes in order to develop a large structural response databank. On the basis of this wide-ranging parametric investigation, after an appropriate statistical analysis, simple empirical expressions are proposed for a straightforward and efficient evaluation of maximum seismic displacements of reinforced concrete buildings structures from their permanent deformation. Permanent displacements can be measured in-situ after strong ground motions as a post-earthquake assessment. It can be concluded that the measure of permanent deformation can be efficiently used to estimate the post-seismic performance level of reinforced concrete buildings.

Post-earthquake Performance of a Slab-Column Connection with Punching Shear Reinforcement

ABSTRACT Brittle punching failures can occur in slab–column connections due to earthquake-induced unbalanced moments. The performance of undamaged specimens and various repair/strengthening techniques have been studied in the past. This paper investigates a less studied scenario, in which a flat slab–column connection severely damaged by an earthquake is subjected to another earthquake without undergoing repair. The performance under this special loading protocol is analysed. It is shown that the drift capacity was not significantly impaired, but both the lateral and bending stiffness were reduced. Other relevant observations regarding the post-earthquake life of slab–column connections are brought to attention.

A streamlined approach for evaluating post-earthquake performance of an electric network

ABSTRACT Resilience and functionality of a community after an extreme event rely on performance of several interdependent systems. Data from historic events show that power network seems to be the most critical lifeline, given the dependency of water, communication, transportation, and gas networks on power. This paper focuses on modeling of the performance of an electric network, after an earthquake, for application in analysis of interdependent systems. The paper proposes a streamlined approach to analyze post-earthquake performance of an electric network to identify regions in a community without power. The proposed approach quantifies damage at the component level using fragilities and a capacity index parameter that measures operability. System level network analysis, based on the capacity of the network, is completed to measure and compare power flow before and after the earthquake. A limiting ratio is defined to identify dark versus bright regions. The procedure is validated for two case studies.

Resilient steel frames installed with self-centering dual-steel buckling-restrained brace

As one type of effective earthquake-resisting structural systems, buckling-restrained braced frames are expected to provide good seismic performance through significant plastic yielding to dissipate earthquake energy. This plastic deformation can cause significant structural damage and residual drift, leading to high retrofitting cost or even demolishment of structures after strong earthquakes. As a result, development of new systems that can not only dissipate seismic energy, but also possess self-centering ability, becomes necessary. This paper makes use of a newly proposed type of self-centering dual-steel buckling-restrained braces (SC-DBRBs). The SC-DBRB consists of a low-yield-point steel and a high strength steel, in which the low-yield-point steel mainly provides energy dissipation ability, and the high strength steel offers self-centering ability and additional energy dissipation ability during strong earthquakes. Compared with a conventional BRB (CBRB) commonly with a typical bilinear constitutive model, the SC-DBRB has a trilinear hysteretic behavior, leading to early re-yielding of the low-yield-point steel during subsequent strain reversals. This early re-yielding mechanism can greatly mitigate residual deformation of the SC-DBRB. In this paper, the constitutive model of the SC-DBRB is first established, and its correlation with main design parameters is also discussed. To demonstrate the self-centering ability of the SC-DBRB and its effect on post-earthquake performance of structures, a series of six-story and nine-story steel frames were numerically investigated using ABAQUS: unbraced frames, CBRB-equipped frames and SC-DBRB-equipped frames. Time history analysis results show that the SC-DBRB can effectively reduce residual drift.

Full-scale shake table tests of the tension-only concentrically braced steel beam-through frame

The tension-only concentrically braced steel beam-through frame (TCBBF) has the potential to enhance the seismic and post-earthquake performance for low-rise buildings in low to moderate seismic regions. To a better understanding of the dynamic response of TCBBFs, full-scale shake table tests under different seismic hazard levels and aftershocks were conducted on a three-story structural model. From the test results, the damage-control and low-residual-displacement behaviors were verified firstly. Under maximum considered earthquake (MCE), the main frame nearly remained elastic while all the braces yielded and there was almost no residual displacement. Under stronger earthquakes exceeding the MCE, yielding occurred at the beam-column connections, and the main frame demonstrated pinching behavior. Meanwhile, the residual displacement of the structure was still at a very low level. The tension-only braces played a key role in the seismic behavior. The existence of prestress made the braces able to sustain a little compression and thus increased the initial lateral stiffness of the structure. The slackness of the brace would enlarge story drift response and also induce dynamic impact due to the sudden tensioning. This impact effect was effectively controlled because of the high ductility of the braces. Tightening the slack braces was a convenient way to restore the structural behavior if the main frame was not damaged.

Performance of winery facilities during the 14 November 2016 Kaikōura earthquake

In-field post-earthquake performance observations of winery facilities in the Marlborough region, New Zealand, were documented following the 14 November 2016 Kaikōura earthquake and subsequent aftershocks. Observations presented and discussed herein include land damage to vineyards and the performance of winery building facilities, legged and flat-bedded storage tanks, barrel racking systems, and catwalks. A range of winery facilities were instrumented with tri-axial accelerometers to capture seismic excitations during aftershocks, with the specific aim to instrument different storage tanks having varying capacities and support systems to better understand the dynamic performance and actual forces experienced up the height of the tanks during an earthquake, with preliminary results reported herein.

Structural Identification of an 18-Story RC Building in Nepal Using Post-Earthquake Ambient Vibration and Lidar Data

Few studies have been conducted to assess post-earthquake performance of structures using vibration measurements. This paper presents system identification and finite element modeling of an 18-story apartment building that was damaged during the 2015 Gorkha earthquake in Nepal. In July 2016, a few months after the earthquake, the authors visited the building and collected its ambient acceleration response. The recorded data are analyzed and the modal parameters of the structure are identified using an output-only system identification method. A linear finite element model of the building is also developed based on the geometry of the building and its material properties to estimate numerically its dynamic characteristics. The identified modal parameters are compared to those of the model to identify possible shortcomings of the modeling and identification approaches. The identified natural frequencies and mode shapes of the first two vibration modes are in good agreement with the model.

Experimental study on dynamic behavior of buried concrete rectangular liquid storage tanks using shaking table

Buried concrete rectangular liquid storage tanks are categorized as key elements in lifeline network for fluid storage, especially potable water. A large number of them were built in Iran before 1980, without taking any seismic considerations, which their performance after an earthquake is a matter of concern. Thus, understanding the seismic behavior of these tanks in terms of water tightness, serviceability conditions, damage levels, and downtime days in case of an earthquake is crucial from the perspective of post-earthquake performance. Furthermore, research into the behavior of such rectangular-shaped tanks is complicated mainly because of the soil–tank–water interaction and the presence of expansion joints. Hence in this study, a series of small-scale experimental tests, using 1 g shaking table, were provided to investigate the effect of amplitude and frequency of input excitation on model responses with regard to the water level, the buried depth, and the density of surrounding soil. The results presented the pattern of soil cracks and showed that empty tanks had greater displacements than full ones. In addition, better performance was observed in the tanks embedded deeper and in denser soil. The damping ratios in full-water tanks were obtained more than in empty ones. Finally, within the framework of this study, the experimental results were compared with ACI 350-6 code; the results of hydrodynamic pressure showed acceptable agreement between two methods, except at the resonance frequency. However, some discrepancy was observed in results related to the phase of the dynamic soil force.

Prototype Testing of a New Passive Energy Dissipation Device for Seismic Retrofit of Bridges

The increasingly demanding performance requirements trigger the development of new devices to eliminate the limitations concerning the post-earthquake performance of available seismic protection systems. The prerequisite for economical earthquake-resistant bridges is the structures’ capacity to absorb and dissipate a large amount of seismic energy. A widely considered strategy for enhancing this capacity is through the use of passive energy dissipation systems for seismic protection of structures. It has been known that majority of the available energy dissipation systems are non-usable after a major earthquake, which increases the risk of collapse during an aftershock. The focus of the current study is given to introduce a new type of passive energy dissipation device with a pending patent that is testified to have an improved energy dissipation capacity without suffering any damage while absorbing energy. Thus, the proposed damper does not require an immediate expensive replacement and keeps its operational capabilities and effectiveness during aftershocks. The paper presents the dynamic performance tests of the first full-scale prototype of the damper that eventually prove it to be a promising design with an improved energy dissipation capacity and stable behavior during and after the dynamic event.

Probabilistic performance-based evaluation of a tall steel moment resisting frame under post-earthquake fires

Purpose This paper aims to develop a framework to assess the reliability of structures subject to a fire following an earthquake (FFE) event. The proposed framework is implemented in one seamless programming environment and is used to analyze an example nine-story steel moment-resisting frame (MRF) under an FFE. The framework includes uncertainties in load and material properties at elevated temperatures and evaluates the MRF performance based on various limit states. Design/methodology/approach Specifically, this work models the uncertainties in fire load density, yield strength and modulus of elasticity of steel. The location of fire compartment is also varied to investigate the effect of story level (lower vs higher) and bay location (interior vs exterior) of the fire on the post-earthquake performance of the frame. The frame is modeled in OpenSees to perform non-linear dynamic, thermal and reliability analyses of the structure. Findings Results show that interior bays are more susceptible than exterior bays to connection failure because of the development of larger tension forces during the cooling phase of the fire. Also, upper floors in general are more probable to reach specified damage states than lower floors because of the smaller beam sizes. Overall, results suggest that modern MRFs with a design that is governed by inter-story drifts have enough residual strength after an earthquake so that a subsequent fire typically does not lead to results significantly different compared to those of an event where the fire occurs without previous seismic damage. However, the seismic damage could lead to larger fire spread, increased danger to the building as a whole and larger associated economic losses. Originality/value Although the paper focuses on FFE, the proposed framework is general and can be extended to other multi-hazard scenarios.

Post-earthquake performance indicators for sewerage systems

This paper presents a set of performance indicators (PIs) for assessing loss of wastewater service and the induced functional impacts in three different phases: emergency response, short-term recovery and long-term restoration. Built on the experience and learning of the Stronger Christchurch Infrastructure Rebuild Team in reinstating the resilience of the Christchurch wastewater system following the Canterbury Earthquakes in 2010–2011, the developed PIs aim to evaluate holistically the structural, hydraulic, environmental, social and economic consequences that might arise due to the earthquake-induced physical damage to sewerage components. This includes sewer pipelines, pumping stations, manholes and council-owned laterals. Furthermore, a framework in which the proposed PIs are integrated into is introduced for demonstrating practical applications. The decision support framework includes three modules, namely: (a) physical damage module, (b) functional impact module and (c) serviceability restoration module. The framework is intended to support the decision-making process in terms of restoration strategy selection and resource allocation in the move towards an effective and informed reinstatement of sewerage systems after earthquakes.

Gaussian process model for maximum and residual drifts of timber-steel hybrid building

The current performance-based building design considers maximum interstorey drift (MISD) ratio as the main structural performance indicator. Observations from past earthquake and reported studies, however, have highlighted that residual interstory drift (RISD) ratio has become an important factor in assessing post-earthquake safety of buildings, and decision in economic feasibility of repair and reconstruction. Improving post-earthquake performance evaluation of buildings enables decision-makers prioritise repair and tag high-risk buildings. The MISD and RISD are subject to uncertainties and have non-linear relation with the input parameters. Thus, in this paper, analytical surrogate model of MISD and RISD ratios are developed using Gaussian process (GP). To show utility of the GP model, a new hybrid building system, cross laminated timber (CLT)–steel moment resisting frame hybrid system, was considered. The hybrid building was design for the seismicity of Vancouver, BC, and meets the current steel design code. For the GP surrogate model, the hybrid building input parameters considered were: infill pattern of the CLT, bracket spacing of the connection between the CLT and steel frame and panel thickness and strength of the CLT. In addition, sensitivity of four ground motion indicators was considered as surrogate input into the GP model: peak ground acceleration, ratio of peak ground acceleration/peak ground velocity, Arias intensity measure and significant duration. In general, the GP model showed good predictive performance of MISD and RISD ratios. In particular, the best predictions were obtained using the ratio of peak ground acceleration/peak ground velocity as a covariate.

Stiffness-Based Design for Mitigation of Residual Displacements of Buckling-Restrained Braced Frames

AbstractBuckling-restrained braced frames (BRBFs) are often used as primary seismic force resisting systems to achieve the desired seismic performance of building frames. However, significant residual displacements of these systems may cause concerns on their postearthquake performance, especially under long duration earthquakes and strong aftershocks. Although backup moment frames (MFs) along with the BRBFs, referred to as dual systems, can be used to mitigate their residual interstory drifts, there is no design criterion on how to determine the section sizes in the MF for this purpose. In the research reported in this paper, a simple mitigation technique was developed, which relies on a stiffness-based design in which the residual interstory drifts can be effectively controlled by increasing the elastic story stiffness using column sections with a higher moment of inertia. Nonlinear time-history analyses were carried out on low-to-high rise BRBFs for a set of 20 design basis earthquake (DBE) level groun...