Study on time-varying seismic vulnerability and analysis of ECC-RC composite piers using high strength reinforcement bars in offshore environment

As the main seismic component of a bridge,seismic damage to the bridge pier has a greater effect on its subsequent service.In the offshore chloride environment,the issues(e.g.,reinforcement bar corrosion and attenuation of concrete strength)of piers caused by chloride ion seriously curtail the normal service life and deteriorate the anti-seismic property of bridge structures.The engineered cementitious composite(ECC)-reinforced concrete(RC)composite pier with high strength reinforcement bars(HSRB)is expected to solve the above problems.This study aims to clarify the time-varying seismic vulnerability(SV)of the HSRBECC-RC composite pier during its full life cycle(FLC).Based on OpenSees,the refined finite element analysis models of RC pier,ECC-RC composite pier,and HSRBECC-RC composite pier have been established.Moreover,using the nonlinear time-path dynamic analysis method,the influence of chloride ion erosion on the time-dependent seismic vulnerability(SV)of these different piers in different service life and different peak ground acceleration(PGA)were analyzed from a dynamic point of view.The research shows that the exceeding probability(EP)of the same damage level increases with the enhancement of service time and PGA and with the increase of destruction,the exceeding probability(EP)of slight damage(DL-1),moderate damage(DL-2),serious damage(DL-3),and complete collapse(DL-4)decreases in turn;the corrosion degree of chloride ion to piers is small during the early service period,the time-varying vulnerability curve of the bridge piers is almost the same as that of a new bridge,and during later service,as the extent of chloride ion corrosion deepens,exceeding probability(EP)under severe damage(DL-3)and complete collapse(DL-4)is increased,and the seismic performance is significantly enhanced.

Performance-based methodology for assessing seismic vulnerability and capacity of buildings

This paper presents a performance-based methodology for the assessment of seismic vulnerability and capacity of buildings. The vulnerability assessment methodology is based on the HAZUS methodology and the improved capacity- demand-diagram method. The spectral displacement (Sd) of performance points on a capacity curve is used to estimate the damage level of a building. The relationship between Sd and peak ground acceleration (PGA) is established, and then a new vulnerability function is expressed in terms of PGA. Furthermore, the expected value of the seismic capacity index (SCev) is provided to estimate the seismic capacity of buildings based on the probability distribution of damage levels and the corresponding seismic capacity index. The results indicate that the proposed vulnerability methodology is able to assess seismic damage of a large number of building stock directly and quickly following an earthquake. The SCev provides an effective index to measure the seismic capacity of buildings and illustrate the relationship between the seismic capacity of buildings and seismic action. The estimated result is compared with damage surveys of the cities of Dujiangyan and Jiangyou in the M8.0 Wenchuan earthquake, revealing that the methodology is acceptable for seismic risk assessment and decision making. The primary reasons for discrepancies between the estimated results and the damage surveys are discussed.

Vector-intensity measure based seismic vulnerability analysis of bridge structures

This paper presents a method for seismic vulnerability analysis of bridge structures based on vector-valued intensity measure （viM）, which predicts the limit-state capacities efficiently with multi-intensity measures of seismic event. Accounting for the uncertainties of the bridge model, ten single-bent overpass bridge structures are taken as samples statistically using Latin hypercube sampling approach. 200 earthquake records are chosen randomly for the uncertainties of ground motions according to the site condition of the bridges. The uncertainties of structural capacity and seismic demand are evaluated with the ratios of demand to capacity in different damage state. By comparing the relative importance of different intensity measures, Sa（T1） and Sa（T2） are chosen as viM. Then, the vector-valued fragility functions of different bridge components are developed. Finally, the system-level vulnerability of the bridge based on viM is studied with Duunett- Sobel class correlation matrix which can consider the correlation effects of different bridge components. The study indicates that an increment IMs from a scalar IM to viM results in a significant reduction in the dispersion of fragility functions and in the uncertainties in evaluating earthquake risk. The feasibility and validity of the proposed vulnerability analysis method is validated and the bridge is more vulnerable than any components.

Time-variant fragility analysis of the bridge system considering time-varying dependence among typical component seismic demands

This paper presents a copula technique to develop time-variant seismic fragility curves for corroded bridges at the system level and considers the realistic time-varying dependence among component seismic demands. Based on material deterioration mechanisms and incremental dynamic analysis, the time-evolving seismic demands of components were obtained in the form of marginal probability distributions. The time-varying dependences among bridge components were then captured with the best fitting copula function, which was selected from the commonly used copula classes by the empirical distribution based analysis method. The system time-variant fragility curves at different damage states were developed and the effects of time-varying dependences among components on the bridge system fragility were investigated. The results indicate the time-varying dependence among components significantly affects the time-variant fragility of the bridge system. The copula technique captures the nonlinear dependence among component seismic demands accurately and easily by separating the marginal distributions and the dependence among them.

Availability of seismic vulnerability index(K_g) in the assessment of building damage in Van, Eastern Turkey

The seismic vulnerability index(Kg) is a parameter that depends on the dynamic properties of soil. With this parameter, it is possible to evaluate the vulnerability of a point-based site under strong ground motion. Since it is related to the natural vibration period and amplification factor, the parameter can be calculated for both soil and structure. In this study, HVSR microtremor measurements are recorded at more than 200 points in the Van region to generate a seismic vulnerability index map. After generating the map, it is determined that the hazard potential and seismic vulnerability index is high at the sites close to Van Lake and at the densely populated city center. Damage information of the buildings investigated after the 2011 Van earthquakes(Mw = 7.1) are placed on the seismic vulnerability index map and it is realized that there may be a correlation between the damage and the seismic vulnerability index. There is a high correlation, approximately 80 percent, between the damage rate map based on the damaged building data and the K_g values. In addition, vulnerability indexes of buildings are calculated and the effect of local soil conditions and building properties on the damage levels are determined. From the results of this study and the site observations after the 2011 Van earthquakes, it is found that structural damage is not only structure-dependent but is also related to the dynamic behavior of soil layers and local soil conditions.

Seismic vulnerability evaluation of axially loaded steel built-up laced members II:evaluations

The test results described in Part 1 of this paper （Lee and Bruneau, 2008） on twelve steel built-up laced members （BLMs） subjected to quasi-static loading are analyzed to provide better knowledge on their seismic behavior. Strength capacity of the BLM specimens is correlated with the strength predicted by the AISC LRFD Specifications. Assessments of hysteretic properties such as ductility capacity, energy dissipation capacity, and strength degradation after buckling of the specimen are performed. The compressive strength of BLMs is found to be relatively well predicted by the AISC LRFD Specifications. BLMs with smaller kl/r were ductile but failed to reach the target ductility of 3.0 before starting to fracture, while those with larger kl/r could meet the ductility demand in most cases. The normalized energy dissipation ratio, EC/ET and the normalized compressive strength degradation, Cr″/Cr of BLMs typically decrease as normalized displacements δ/δb,exp increase, and the ratios for specimens with larger kl/r dropped more rapidly than for specimens with smaller kl/r; similar trends were observed for the monolithic braces. The BLMs with a smaller slenderness ratio, kl/r, and width-to-thickness ratio, b/t, experienced a larger number of inelastic cycles than those with larger ratios.

The Tesistan, Mexico earthquake (M_w 4.9) of 11 May 2016: seismic-tectonic environment and resonance vulnerability on buildings

To highlight the importance of small earthquakes in seismic hazard, a study of the 11 May 2016, Mw 4.9, Tesistan, Mexico earthquake is presented. Due to the close proximity of the event to the city, accelerations were considerably higher than those caused by historical severe earthquakes (6.0 < Mw < 8.2). This paper addresses two objectives related to the Tesistan event: the fi rst is to estimate the focal mechanism solution in order to place the event in the context of the tectonic environment of this area. The second is focused on a vulnerability evaluation of buildings that suff ered resonance. Several building′s typologies with variations in construction system and height are assessed in terms of resonance with the structural and soil periods. The results show that around the Zapopan station, strong damage is expected in intermediate to high-rise buildings (12-30 m) with moment resistant frame systems and in reinforced concrete shear walls. Masonry structures around this station may not present resonance. In contrast, in the surroundings of the Guadalajara station, all intermediate height buildings from 9 to 21 m may present resonance.

Practical seismic resilience evaluation and crisis management planning through GIS-based vulnerability assessment of buildings

The objective of this paper is to demonstrate how assessment of seismic vulnerability can be effective in protection against earthquakes.Findings are reported from a case study in a densely populated urban area near an active fault,utilizing practical methods and exact engineering data.Vulnerability factors were determined due to technical considerations,and a field campaign was performed to collect the required data.Multi-criteria decision making was carried out by means of an analytical hierarchy process including a fuzzy standardization.Earthquake scenarios were applied through an implicit vulnerability model.GIS was utilized and the results were analyzed by classifying the state of vulnerability in levels as very low,low,moderate,high,and very high.Seismic resilience was evaluated as vulnerabilities below the moderate state,being about 40% in an intensity of 6 Mercalli and less than 10% in 10 Mercalli.It is concluded that seismic resilience in the area studied is not acceptable,the area is vulnerable in the expected scenarios,and due to the high seismicity of the region,proper crisis management planning is required in parallel with attempts toward retrofitting.In this regard,an emergency map was developed with reference to the assessed vulnerabilities.

Seismic Vulnerability Analysis of Single-Story Reinforced Concrete Industrial Buildings with Seismic Fortification

As there is a lack of earthquake damage data for factory buildings with seismic fortifications in China,seismic vulnerability analysis was performed by numerical simulation in this paper.The earthquake-structure analysis model was developed with considering the influence of uncertainties of the ground motion and structural model parameters.The small-size sampling was conducted based on the Latin hypercube sampling and orthogonal design methods.Using nonlinear analysis,the seismic vulnerability curves and damage probability matrix with various seismic fortification intensities(SFI)were obtained.The seismic capacity of the factory building was then evaluated.The results showed that,with different designs at different SFIs,the factory building could consistently achieve the three seismic fortification objectives.For the studied factory buildings with the SFI of 6,they satisfied the seismic fortification requirements of“no damage in moderate earthquakes,mendable in strong earthquakes”;for those buildings with SFIs of 7 and 8,the requirement of“no collapsing in super strong earthquakes”was generally met;while for those with SFIs of 9,the requirement of“mendable in moderate earthquakes”was almost satisfied.The results showed factory buildings designed with low SFIs are better at achieving the seismic fortification objectives than those designed with high SFIs.

Seismic vulnerability assessment of urban buildings using the rough set theory and weighted linear combination

Seismic vulnerability assessment of urban buildings is among the most crucial procedures to post-disaster response and recovery of infrastructure systems.The present study proceeds to estimate the seismic vulnerability of urban buildings and proposes a new framework training on the two objectives.First,a comprehensive interpretation of the effective parameters of this phenomenon including physical and human factors is done.Second,the Rough Set theory is used to reduce the integration uncertainties,as there are numerous quantitative and qualitative data.Both objectives were conducted on seven distinct earthquake scenarios with different intensities based on distance from the fault line and the epicenter.The proposed method was implemented by measuring seismic vulnerability for the seven specified seismic scenarios.The final results indicated that among the entire studied buildings,71.5%were highly vulnerable as concerning the highest earthquake scenario(intensity=7 MM and acceleration calculated based on the epicenter),while in the lowest earthquake scenario(intensity=5 MM),the percentage of vulnerable buildings decreased to approximately 57%.Also,the findings proved that the distance from the fault line rather than the earthquake center(epicenter)has a significant effect on the seismic vulnerability of urban buildings.The model was evaluated by comparing the results with the weighted linear combination(WLC)method.The accuracy of the proposed model was substantiated according to evaluation reports.Vulnerability assessment based on the distance from the epicenter and its comparison with the distance from the fault shows significant reliable results.

Assessment of Urban Physical Seismic Vulnerability Using the Combination of AHP and TOPSIS Models: A Case Study of Residential Neighborhoods of Mymensingh City, Bangladesh

Mymensingh, one of the oldest municipalities of Bangladesh, is at great risk against earthquakes because three major faults viz. Dauki fault, Madhupur fault, and Sylhet-Assam fault are located around it, and possesses liquefaction susceptible soil type. The city has great significance from the economic and administrative point of view and recently declared as the 8th administrative division of Bangladesh which directly stimulates the unplanned future expansion. Considering the potentiality of haphazard development and high seismic risk, it is crucial to assess the seismic vulnerability for taking the judicious decision regarding risk reduction measures for the city. The study combines Technique for Order Preference by Similarity to Ideal Solution method (TOPSIS) and Analytical Hierarchical Process (AHP) models to assess the seismic vulnerability of residential neighborhoods of Mymensingh city as the probability of death and damage is remarkable in residential neighborhoods than other land use types. A combined quantitative methodology of AHP-TOPSIS is used in this study to quantify 13 important qualitative and quantitative factors of earthquake vulnerability, decided on expert opinions. The data of 13 vulnerability factors are collected from the Mymensingh Strategic Development Plan (MSDP, 2011-2031) database, done under Comprehensive Disaster Management Programme (CDMP)-II during 2012-2014. Geographic Information System is used in this study to analyze and mapping of seismic vulnerability. Results indicated that 37 residential neighborhoods are very highly vulnerable, 55 neighborhoods are highly vulnerable, 75 neighborhoods are moderately vulnerable and 74 neighborhoods are in the low vulnerable category.

Effect of URM infills on seismic vulnerability of Indian code designed RC frame buildings

Unreinforced Masonry (URM) is the most common partitioning material in framed buildings in India and many other countries. Although it is well-known that under lateral loading the behavior and modes of failure of the frame buildings change significantly due to infill-frame interaction, the general design practice is to treat infills as nonstructural elements and their stiffness, strength and interaction with the frame is often ignored, primarily because of difficulties in simulation and lack of modeling guidelines in design codes. The Indian Standard, like many other national codes, does not provide explicit insight into the anticipated performance and associated vulnerability of infilled frames. This paper presents an analytical study on the seismic performance and fragility analysis of Indian code-designed RC frame buildings with and without URM infills. Infills are modeled as diagonal struts as per ASCE 41 guidelines and various modes of failure are considered. HAZUS methodology along with nonlinear static analysis is used to compare the seismic vulnerability of bare and infilled frames. The comparative study suggests that URM infills result in a significant increase in the seismic vulnerability of RC frames and their effect needs to be properly incorporated in design codes.

Rapid assessment for seismic vulnerability of low and medium rise infilled RC frame buildings

An indexing method for rapid evaluation of the seismic vulnerability of infi lled RC frame buildings in Jordan is proposed. The method aims at identifying low and medium rise residential buildings as safe or in need of further detailed evaluation. Following a rapid visual screening, the building is assigned a Basic Capacity Index(BCI); fi ve performance modifi ers are identifi ed and multiplied by the BCI to arrive at the Capacity Index(CI) of the building. A Capacity Index lower than a limit CI value indicates that the screened building could experience moderate earthquake damage whereas a higher value implies that minor damage, if any, would take place. To establish the basic evaluation parameters; forty RC frame buildings were selected, designed and analyzed using static nonlinear analysis and incorporating the effect of infi ll walls. Effects of seismicity, local site conditions, horizontal irregularities(setbacks and re-entrant corners), vertical irregularities(soft story at ground fl oor level) and overhangs on the seismic performance of local buildings were examined. Assessment forms were designed and used to evaluate and rank 112 sample buildings. About 40% of the surveyed buildings were found to be in need of detailed evaluation to better defi ne their seismic vulnerabilities.

Seismic vulnerability estimation of the building considering seismic environment and local site condition

A procedure is developed to incorporate seismic environment and site condition into the framework of seismic vulnerability estimation of building to consider the effects of the severity and/or frequency content of ground motion due to seismic environment and site condition. Localized damage distribution can be strongly influenced by seismic environment and surficial soil conditions and any attempt to quantify seismic vulnerability of building should consider the impact of these effects. The seismic environment, site and structure are coupled to estimate damage probability distribution among different damage states for the building. Response spectra at rock site are estimated by probabilistic seismic hazard assessment approach. Based upon engineering representations of soil and amplifying spectral coordinates, frequency content and severity of ground motion are considered. Furthermore the impacts of severity and/or frequency of ground motion effects are considered to estimate the seismic response of reinforced concrete building and damage probability distribution for the building. In addition, a new method for presenting the distribution of damage is developed to express damage probability distribution for the building for different seismic hazard levels.

Influence of spiral anchor composite foundation on seismic vulnerability of raw soil structure

A typical single-layer raw soil structure in villages and towns in China is taken as the research object.In the probabilistic seismic demand analysis,the seismic demand model is obtained by the incremental dynamic time history analysis method.The seismic vulnerability analysis is carried out for the raw soil structure of nonfoundation,strip foundation,and spiral anchor composite foundation,respectively.The spiral anchor composite foundation can reduce the seismic response and failure state of raw soil structure,and the performance level of the structure is significantly improved.Structural requirements sample data with the same ground motion intensity are analyzed by linear regression statistics.Compared with the probabilistic seismic demand model under various working conditions,the seismic demand increases gradually with the increase of intensity.The seismic vulnerability curve is summarized for comparative analysis.With the gradual deepening of the limit state,the reduction effect of spiral anchor composite foundation on the exceedance probability becomes more and more obvious,which can reduce the probability of structural failure to a certain extent.

Mapping Seismic Vulnerability and Risk of Cities： The MASSIVE Project

MASSIVE （mapping seismic vulnerability and risk of cities） is a GIS-based earthquake preparedness system that was developed under the European Union Civil Protection Mechanism project （GA No. 070401/2009/540429/SUB/A4）, in order to provide civil protection authorities with accurate, and easily transferable tools for generating up-to-date maps of seismic hazard, seismic vulnerability and seismic risk of buildings, at the scale of the single building block. In addition, MASSIVE developed and ran state-of-the-art models to assess the risk for population evacuation in dense urban agglomerations given an earthquake event. The MASSIVE methodology was designed, implemented and validated considering two European pilot sites, heavily struck by recent earthquakes, which are the western part of the Larger Metropolitan Area of Athens （GR）, and the city of L＇ Aquila in the Abruzzo Region （IT）. The validation of the results using past earthquake records shows that the performance of MASSIVE is prosperous, achieving a correlation between the modeled and the on-site measured PGAs （peak ground accelerations） higher than 0.75, while the correlation between the on-site reported building damages and the ones predicted by the MASSIVE system has been of the order of 0.80.

Seismic Vulnerability of Building Construction Site

Building construction site plays an important role in the economic aspect of a region. So any disruption due to hazard event like earthquake can cause several direct and indirect damages. Direct damages can lead to the loss of equipments and qualified persons. Indirect damages can lead to inflation and loss of purchasing power. To deal with that situation, parameters that govern the vulnerability of building construction site have been identified. Using a MCDM （multiple criteria decision making） method, the priority order of these parameters has been set. Then a PVI （partial vulnerability index） and a GVI （global vulnerability index） are proposed. These indexes allow the classification of building construction sites according to their intrinsic vulnerability and seismic vulnerability respectively that is through the use of a given classification. Several Algerian building construction sites belonging to different seismic zones were considered in order to show the applicability of the method.

Seismic Vulnerability Assessment from Earthquake Damages Historical Data Using Constrained Optimization Technique

This present work falls within the context of efforts that have been made over the past many years, aimed in improving the seismic vulnerability modelling of structures when using historical data. The historical data describe the intensity and the damages, but do not give information about the vulnerability, since only in the ’90 the concept of vulnerability classes was introduced through the EMS92 and EMS98 scales. Considering EMS98 definitions, RISK-UE project derived a method for physical damage estimation. It introduced an analytical equation as a function of an only one parameter (Vulnerability Index), which correlates the seismic input, in term of Macroseismic Intensity, with the physical damage. In this study, we propose a methodology that uses optimization algorithms allowing a combination of theoretical-based with expert opinion-based assessment data. The objective of this combination is to estimate the optimal Vulnerability Index that fits the historical data, and hence, to give the minimum error in a seismic risk scenario. We apply the proposed methodology to the El Asnam earthquake (1980), but this approach remains general and can be extrapolated to any other region, and more, it can be applied to predictive studies (before each earthquake scenarios). The mathematical formulation gives choice for regarding, to the optic of minimizing the error, either for the: 1) very little damaged building (D0-D2 degree) or 2) highly damaged building (D4-D5 degree). These two different kinds of optics are adapted for the people who make organizational decisions as for mitigation measures and urban planning in the first case and civil protection and urgent action after a seismic event in the second case. The insight is used in the framework of seismic scenarios and offers advancing of damage estimation for the area in which no recent data, or either no data regarding vulnerability, are available.

Time-varying seismic fragility analysis of durability damage of high-tensile reinforcement ECC bridge pier

The deterioration of the performance of offshore bridges is particularly prominent due to the complex natural environment,including the coupling effects of earthquake and seawater erosion.In particular,bridge piers are the main energy-consuming and load-bearing components,so that excellent seismic capacity of bridge piers is the key to avoiding bridge damage.Although earthquake resistant behavior of ordinary reinforced concrete bridge piers(ordinary pier)can be improved by increasing the section size and reinforcement ratio of piers,the improvement of the earthquake resistant behavior is limited.To further improve the earthquake resistant behavior of bridge piers,high-tensile reinforcement engineered cementitious composite(ECC)bridge piers are utilized and time-varying seismic fragility analysis are conducted in this study.The refined model of a bridge pier is built by OpenSees.First,the influence of ECC replacement height on pier curvature is analyzed to determine the reasonable ECC height.Then,the time-varying fragility analysis of high-tensile reinforcement ECC piers(ECC composite piers)with durability damage are evaluated considering the time-varying law of materials.Four damage states,slight damage,moderate damage,extensive damage and complete collapse,are utilized in the study.These fragility curves indicate the durability damage can debase the earthquake resistant behavior of piers continually,the exceedance probability of the same state of destruction increases with the increase of peak ground acceleration(PGA)and service time of pier.The results also indicate that the corrosion level of chloride ion to pier is small during the early service period,and the bridge pier vulnerable curve is similar to that of the new bridge pier.As the level of chlorine ion corrosion deepens,transcendental probability is increased.Compared with the ordinary pier,the exceedance probability in each limit state of ECC composite piers is significantly reduced.The proposed ECC composite pies leads to better realistic time-varying earthquake resistant behavior.

Improving the seismic performance of base-isolated liquid storage tanks with supplemental linear viscous dampers

Large tanks are extensively used for storing water,petrochemicals and fuels.Since they are often cited in earthquake-prone areas,the safe and continuous operation of these important structures must be ensured even when severe earthquakes occur,since their failure could have devastating financial and socio-environmental consequences.Base-isolation has been widely adopted for the efficient seismic protection of such critical facilities.However,base-isolated tanks can be located relatively close to active faults that generate strong excitations with special characteristics.Consequently,viscous dampers can be incorporated into the isolation system to reduce excessive displacement demands and to avoid overconservative isolator design.Nonetheless,only a few studies have focused on the investigation of seismic response of base-isolated liquid storage tanks in conjunction with supplemental viscous dampers.Therefore,the impact of the addition of supplemental linear viscous dampers on the seismic performance of tanks isolated by single friction pendulum devices is investigated herein.Four levels of supplemental damping are assessed and compared with respect to isolators′displacement capacity and accelerations that are transferred to the tanks.