Seismic Loss Analysis Research Articles

Seismic Risk Analysis of Offshore Bridges Considering Seismic Correlation between Vulnerable Components

To comprehensively evaluate the seismic performance of offshore bridges, a seismic risk analysis of an example bridge was developed based on improved two-dimensional (2D) seismic fragility analysis. Taking a simply-supported beam bridge in an offshore tidal environment as an example, the adverse effects of chloride ion erosion are considered and the seismic response process of the example bridge is simulated using the Incremental Dynamic Analysis (IDA) method. The appropriate damage indexes are chosen for the plate rubber bearing and the pier, and the one-dimensional (1D) seismic fragility curves of single components and the entire bridge are obtained. The correlation coefficients of vulnerable components are quantitatively proposed based on the correlation analysis method, and the 2D seismic fragility curves of the entire bridge are achieved while accounting for seismic correlation between vulnerable components. The seismic risk probability of the entire bridge is finally determined after combining hazard analysis at the bridge site and seismic loss analysis. The results show that there is a significant correlation between vulnerable components and that 2D seismic fragility analysis based on the reliable correlation coefficients of vulnerable components can more comprehensively evaluate the seismic performance of the entire bridge. In the context of seismic disaster reduction research focused on slight and moderate damage caused by moderate-to-small ground motions, this research can provide scientific and technical support for seismic design and seismic risk assessment of offshore bridges.

Nonstructural Seismic Loss Analysis of Traditional and Innovative Partition Systems Housed in Code-conforming RC Frame Buildings

ABSTRACT This study investigates the seismic losses associated with the damage of traditional and innovative partitions housed in code-conforming RC frame buildings. Three-story buildings located in low-to-high seismicity sites in Italy are considered. Nonlinear multiple-stripe analyses are performed according to the conditional spectrum approach. The partition capacities are evaluated according to experimental studies, and the elementary partition costs are derived considering the Italian construction price lists. The seismic assessment is performed considering low-to-severe damage limit states. The seismic losses associated with the partition damage are evaluated; the efficiency of the investigated partitions is provided according to the different seismicity.

Seismic demand model class uncertainty in seismic loss analysis for a code-designed URM infilled RC frame building

Probabilistic seismic risk is affected by several sources of uncertainty. Investigating their influence on loss analysis results is essential to obtain reliable quantitative estimations of seismic performance. Within the framework developed by the Pacific Earthquake Engineering Research (PEER) Center for probabilistic seismic loss analysis, this study incorporates the effect of seismic demand model class uncertainty on seismic risk performance metric estimation. The extended formulation is illustrated with an application example code-designed reinforced concrete moment resisting frame building with unreinforced masonry (URM) infill walls, where model class uncertainty related to URM infill walls modeling is propagated to the estimation of seismic financial losses. Model class uncertainty accounts for the variability arising from the use of different modeling solutions, such as the ones associated with the adoption of three equivalent strut macro-models and their modeling parameters. Probabilistic distributions are assigned to selected infill strut model parameters, and a large set of finite element models (FEMs) are generated for each infill strut model class by sampling the model parameter distributions through Latin Hypercube Sampling (LHS). Expected values of repair cost and life-cycle annualized loss are evaluated and compared for two sets of three building performance models. The first set considers the original (median) values of infill strut backbone parameters, while the second set includes model parameter uncertainty. The uncertainty propagation from structural response results to repair costs is also reported for the six performance models. Finally, the contribution of different structural and non-structural element categories to the financial losses is presented.

Seismic loss analysis of buildings with post-tensioned cross-laminated timber walls

The FEMA P-58 performance-based earthquake engineering methodology was used to assess the economic losses associated with earthquake damage to nonstructural components of two prototype buildings with post-tensioned cross-laminated timber rocking walls. A suite of 22 far-field ground motions were used for nonlinear time history (NLTH) analysis. Truncated incremental dynamic analysis was used to scale the ground motions, and results of the NLTH analyses were used to develop cumulative distribution functions for inter-story drift and peak floor accelerations. The economic factors assessed in the risk analysis included the expected repair cost with respect to spectral acceleration, the probability of exceeding an expected repair cost for selected time periods, and the expected annual loss over different time periods considering various discount factors. It was determined that the ratio of nonstructural repair cost to total building cost at the design earthquake and maximum considered earthquake was lower for the low-rise building than the mid-rise building. However, the probability of nonstructural damage at the service-level earthquake was lower for the mid-rise building than the low-rise building.

Bi‐objective mountain railway alignment optimization incorporating seismic risk assessment

AbstractMountain railway alignment optimization is known as a very complex engineering problem that should consider many factors, such as drastically undulating terrain, geological hazard impacts, and additional constraints. Moreover, many mountain railway projects are located in earthquake‐prone regions and hence are greatly threatened by seismic activity. Thus far, most alignment optimization studies aim at finding the least‐cost solutions within budget but slight attention has been paid to reducing the complex seismic risk through optimization. In this paper, the first known quantitative seismic risk assessment model for railway alignment optimization is presented, which combines probabilistic seismic fragility analysis and probabilistic seismic loss analysis. Three methods for fragility analysis of bridge, tunnel, and earthwork sections are designed and a specific event tree is developed for seismic loss analysis. Moreover, multiple preliminary constraints are specified for alignments traversing active faults. Afterwards, the seismic risk assessment model is combined with a least‐cost model to formulate a bi‐objective optimization model. To solve it, a particle swarm optimization algorithm is improved by blending the crowding distance computation (CDC) and, especially, a novel marginal benefit analysis (MBA) to search for pareto‐optimal solutions during optimization. A prescreening and repairing operator is also designed to handle the fault constraints. Finally, when applying the proposed procedure to a complex realistic railway case, the results show that the hybrid CDC+MBA bi‐objective solver can find better pareto‐optimal solutions than the generic CDC method. Besides, detailed data analysis shows that the present method can produce less expensive as well as safer solutions than the best alignment designed by experienced human engineers.

Optimal structural restoration of historic building in Japan considering lifecycle seismic loss analysis

AbstractAn economic performance evaluation scheme of historic buildings that consider the effect of structural renovation is proposed to provide information facilitating to the selection of reasonable renovation methods for preserving historic buildings. Ground motion scenarios, herein referred to as “lifecycle earthquake scenarios” in accordance with the previous research, were simulated to represent the annual maximum earthquake intensity data from the year of decision‐making until the end year of the building's lifetime. Additionally, the structural characteristics of historic buildings with masonry infill walls as part of the structure were analyzed under the “lifecycle earthquake scenarios.” Through a parametric analysis accounting for the change in structural characteristics and the repair costs in the lifecycle earthquake scenarios, the economic performance of historic buildings was calculated. Based on the results, the demand spectrum that satisfied the economic performance was obtained. This demand spectrum can provide the optimal structural renovation method to facilitate the building owner in making decisions regarding preservation.

Seismic loss analysis of buckling-restrained braced frames considering the effects of modeling uncertainties

Seismic loss analysis of buckling-restrained braced frames considering the effects of modeling uncertainties

Comparative seismic loss analysis of an existing non-ductile RC building based on element fragility functions proposals

A comparative seismic loss analysis is presented for a non-ductile infilled reinforced concrete building evaluating the influence on direct economic losses of different parameters characterizing a building performance model. Propagation of uncertainties to seismic repair cost estimate is investigated in terms of effect of input intensity measures, definition of element fragility and consequence functions specific to non-ductile RC buildings through incremental dynamic analyses and probabilistic performance-based earthquake engineering methodologies. A set of element fragility and consequence functions has been proposed based on experimental data for internal and external beam column joints and on analytical models for masonry infill walls. A quantitative estimate of indirect losses is proposed based on past earthquakes data, incorporating the building inactivity and the delay in the beginning of the reconstruction process. Seismic loss assessment is presented at single hazard levels and critically compared, providing insight into different possible alternatives for performance models implementation. A fully probabilistic life-cycle analysis is carried out to present realistic risk analysis figures for non-ductile reinforced concrete buildings.

A subset simulation based approach with modified conditional sampling and estimator for loss exceedance curve computation

A new stochastic simulation-based approach for the evaluation of loss exceedance curve without repeated reliability analyses, and the generation of samples of input random variables and any function of them conditioned on different levels of loss exceedance is proposed for a comprehensive risk and loss analysis, and investigation. The proposed approach involves the modification of the simulation algorithms in the Subset Simulation and the development of new estimators. It allows for a more comprehensive characterization of the probability distribution of the loss including the tail parts due to combinations of scenarios which can lead to extreme and catastrophic consequences. The approach is robust to the number of random variables involved. The effectiveness and efficiency of the proposed method are shown by an illustrative example involving a seismic loss analysis of a multi-story inelastic structure. A stochastic ground motion model coupled with a stochastic nonlinear dynamic model, and probabilistic fragility and loss functions are considered.

Probabilistic Seismic Loss Analysis for the Design of Steel Structures: Optimizing for Multiple-Objective Functions

An optimized seismic performance-based design (PBD) methodology considering structural and nonstructural system performance and seismic losses is considered to optimize the design of a steel structure. Optimization objectives are to minimize the initial construction cost associated with the weight of the structural system and the expected annual loss (EAL), considering direct economic losses. A non-dominated sorting genetic algorithm method is implemented for the multi-objective optimization. Achieving the desired confidence levels in meeting performance objectives of interest are set as constraints of the optimization problem. Inelastic time history analysis is used to evaluate structural response under different levels of earthquake hazard to obtain engineering demand parameters. Hazus fragility functions are employed for obtaining the damage probabilities for the structural system and nonstructural components. The optimized designs and losses are compared for the structure located in two geographic locations: one in the central United States and another in the western United States.

Empirical loss analysis to support definition of seismic performance objectives for woodframe buildings

Abstract This paper presents an empirical seismic loss analysis procedure for woodframe buildings and examines how it can be utilized to provide input for the development of seismic performance objectives for woodframe buildings in terms of economic loss. This type of performance measure is more directly useful to building owners than qualitative performance levels such as “Life Safety” proposed in first generation performance-based seismic design documents. The procedure combines the PEER loss estimation methodology with the most up-to-date seismic numerical structural models for woodframe buildings and experimental data from full-scale shake table tests. The resulting loss estimates are quite reasonable when compared to observations from the 1994 Northridge, CA earthquake. The procedure is applied to two-story, single-family residential structures to estimate losses as a function of ground motion intensity and building design, and the results are discussed to illustrate how they can be used to help: (1) characterize estimated losses, (2) define performance objectives, and (3) guide design to meet those performance objectives. The study provides the first fully comprehensive application of the PEER methodology to woodframe buildings.

A PORTFOLIO SEISMIC LOSS ESTIMATION CONSIDERING DAMAGE CORRELATION

In a portfolio seismic loss analysis for buildings located in a wide area, it is important to estimate the effect of damage correlation, because a probability mass function of physical loss such as the restoration cost of buildings undergoes effect of correlation except mean value. This paper proposed a practical prediction method for the loss probability mass function of buildings located in a wide area due to earthquakes. The method takes damage correlation into account, which depends on the relative distance between buildings, and a numerical technique based on the theorem of total probability was employed. Numerical results by the proposed method were verified by Monte Carlo simulation, and a good agreement was obtained. A loss probability mass function of 10 buildings located in the Tokyo area due to a scenario earthquake was evaluated for applicability.

Relationships between Strong Ground Motion Peak Values and Seismic Loss during the 1999 Chi-Chi, Taiwan Earthquake

A better real-time assessment of earthquake effects (i.e. seismic intensity estimation)is crucial for hazard mitigation. Especially during the aftermath of a disastrous event,significant reduction of loss can usually be realized through timely execution ofemergency response measures. These effects include strong-ground shaking, groundfailure, and their impact on man-made structures. The descriptive Modified Mercalliintensity scale, though still in common use in many poorly instrumented areas of theworld, is out of date in areas of extensive strong-motion instrumentation. It is desirableto place the earthquake intensity scale on a more quantitative basis based on the actualrecorded ground-motion shaking and carefully compiled damage records. In this paper,we investigated the relationships between earthquake loss, intensity and strong motionpeak values, mainly based on the Chi-Chi earthquake. Both the strong-motion peakvalues and the earthquake loss are related. From the results, we found that peak groundacceleration (PGA) and peak acceleration response spectra at 1 s period (1 s Sa) valuesare two parameters that give slightly higher correlation coefficients than other parametersfor earthquake loss analysis. For intensity estimations, the peak ground velocity (PGV)values and 1 s Sa values are better parameters in the high range and PGA is not stable forsmaller earthquakes. Although PGV values give a slightly lower correlation coefficientand larger standard deviation in seismic loss analysis during the Chi-Chi earthquake, itnevertheless gives more reliable instrumental intensity over a broad magnitude range.1 s Sa is a good parameter for both seismic losses and intensity evaluation. We thusconclude that PGV and 1 s Sa are relatively more stable in damage assessment and,at least in the high end, in intensity estimation. We shall incorporate these findings inour real-time earthquake rapid reporting and early warning systems.