Persisting challenges for performance-based building assessment

Intense research and refinement of the tools used in performance-based seismic engineering have been made,but the maturity and accuracy of these methods have not been adequately confirmed with actual data from the field. The gap between the assumed characteristics of actual building systems and their idealized counterparts used for analysis is wide. When the randomly distributed flaws in buildings as they exist in urban areas and the extreme variability of ground motion patterns combine,the conventional procedures used for pushover or dynamic response history analyses seem to fall short of reconciling the differences between calculated and observed damage. For emergency planning and loss modeling purposes,such discrepancies are factors that must be borne in mind. Two relevant examples are provided herein. These examples demonstrate that consensus-based analytical guidelines also require well-idealized building models that do not lend themselves to reasonably manageable representations from field data. As a corollary,loss modeling techniques,e.g.,used for insurance purposes,must undergo further development and improvement.     

高层建筑结构抗震选型的智能评价方法

指出了结构整体性能实现的阶段性特征，明确了选型阶段是对结构整体性能进行规划，控制与优化等的关键环节，初步给出了从不同角度表征结构及其相关全系统。全寿命，全性能等客观需求与约束的结构选型性能模型。接着分析介绍了四种智能评价方法（即ES、FIS、ANN、ANNFIS法），给出了集成智能评价支持系统的功能结构框图，在介绍了七种Mamdani模糊推理算法的基础上，将模糊综合评价与模糊推理方法结合。给出了一种兼有两者共同优点的多输入加权模糊推理与去模糊化算法及该算法用于性能评价的过程，最后，通过基于该算法的性能评价实例，给出了结构受力合理性性能评价的七条模糊规则及输入输出参数的评价等级标准，隶属函数及其加权模糊推理的过程与结果，结果表明该方法能较好地表征与利用专家知识，经验与策略，能更好地满足结构选型多性能，多层次的性能评价需要，且评价过程与结果直观，有效。上述工作为表征，量化，控制与优化结构性能，恰当利用与改进各类结构。提高选型质量等奠定了基础。     

Detailed assessment of structural characteristics of Turkish RC building stock for loss assessment models

Assessment of the seismic vulnerability of the building stock in the earthquake-prone Marmara region of Turkey is of growing importance since such information is needed for reliable estimation of the losses that possible future earthquakes are likely to induce. The outcome of such loss assessment exercises can be used in planning of urban/regional-scale earthquake protection strategies; this is a priority in Turkey, particularly following the destructive earthquakes of 1999. Considering the size of the building inventory, Istanbul and its surrounding area is a case for which it is not easy to determine the structural properties and characteristics of the building stock. In this paper, geometrical, functional and material properties of the building stock in the northern Marmara Region, particularly around Istanbul, have been investigated and evaluated for use in loss estimation models and other types of statistic- or probability-based studies. In order to do that, the existing reinforced concrete (RC) stock has been classified as ‘compliant’ or ‘non-compliant’ buildings, dual (frame-wall) or frame structures and emergent or embedded-beam systems. In addition to the statistical parameters such as mean values, standard deviations, etc., probability density functions and their goodness-of-fit have also been investigated for all types of parameters. Functionalities such as purpose of use and floor area properties have been defined. Concrete properties of existing and recently constructed buildings and also characteristics of 220 and 420 MPa types of steel have been documented. Finally, the financial effects of retrofitting operations and damage repair have been investigated.     

Ground motion evaluation procedures for performance-based design

The objective of performance-based earthquake engineering (PBEE) is the analysis of performance objectives with a specified annual probability of exceedance. Increasingly undesirable performance is caused by increasing levels of strong ground motion having decreasing annual probabilities of exceedance. Accordingly, the evaluation of ground motion intensity measures is a vital component of PBEE. This paper provides a brief synthesis of ground motion analysis procedures within a performance-based design framework, and is a summary of a recent report to which the reader is referred for details. The principal topics addressed are probabilistic characterizations of source, path, and site effects, with the discussion of these effects focusing principally on applications in active regions such as California.     

Comparison of velocimeter and coherent lidar measurements for building frequency assessment

Over recent years there has been a growing interest in the building frequency analysis for earthquake and structural engineering fields using ambient vibrations. Simultaneously, velocity measurements with LASER remote sensing techniques have gained more interest for several applications. This paper details the comparison of the frequency analysis obtained using sensitive velocimeter sensor and coherent LIDAR (Light Detection and Ranging) sensor, and applied to one RC existing building. Ambient vibrations recordings were processed using the Frequency Domain Decomposition method for defining the frequencies and mode shapes of the building target, while LASER remote sensing approach used coherent LIDAR method for velocity and frequency measurement. The results of the two systems are discussed. A good agreement is observed, which let us conclude on the ability of the coherent LIDAR to assess the frequency of existing buildings for structural and earthquake engineering fields at long range and without any retroreflector on the structure.     

Microzonation of Banja Luka for performance-based earthquake-resistant design

New microzonation maps for the city of Banja Luka in the Republic of Srpska in Bosnia and Herzegovina are presented based on the uniform-hazard-spectrum (UHS) methodology. The results are compared with the previous generation of microzonation maps published in the early 1970s, which were determined for the largest expected levels of shaking and for the spatial variations based on the soil site properties and the observed damage during the 1969 earthquake. The old and new methods are compared with emphasis on their role in the long-term criteria for regional earthquake-resistant design guidelines and the associated consequences.     

Multi-hazard performance assessment of a transfer-plate high-rise building

Many urban areas are located in regions of moderate seismicity and are subjected to strong wind. Buildings in these regions are often designed without seismic provisions. As a result, in the event of an earthquake, the potential for damage and loss of lives may not be known. In this paper, the performance of a typical high-rise building with a thick transfer plate (TP), which is one type of building structure commonly found in Hong Kong, is assessed against both earthquake and wind hazards. Seismic- and wind-resistant performance objectives are fi rst reviewed based on relevant codes and design guidelines for high-rise buildings. After a brief introduction of wind-resistant design of the building, various methodologies, including equivalent static load analysis (ESLA), response spectrum analysis (RSA), pushover analysis (POA), linear and nonlinear time-history analysis (LTHA and NTHA), are employed to assess the seismic performance of the building when subjected to frequent earthquakes, design based earthquakes and maximum credible earthquakes. The effects of design wind and seismic action with a common 50-year return period are also compared. The results indicate that most performance objectives can be satisfi ed by the building, but there are some objectives, such as inter-story drift ratio, that cannot be achieved when subjected to the frequent earthquakes. It is concluded that in addition to wind, seismic action may need to be explicitly considered in the design of buildings in regions of moderate seismicity.     

Fragility and risk assessment of freestanding building contents

Multistorey buildings often have a valuable inventory consisting of objects that their possible damage during an earthquake will cause unacceptable losses. The paper presents a novel, fully performance-based seismic reliability and risk assessment framework for freestanding structural components and contents that can be modelled as rocking rigid blocks. The seismic response of building contents depends on several parameters such as the geometry of the object, the dynamic characteristics of the building and the storey that the object is located. The demand at the storey level is first obtained, and then the response of the contents is calculated using the storey acceleration response history. The demand of the structure is obtained with the aid of a modified version of the Incremental Dynamic Analysis method and subsequently the fragility curves of the rocking building contents are derived for every storey of interest. Different options for fragility assessment are discussed, and the underlying details of the problem are investigated. A simplified approach, where the fragility of the freestanding components and the structure are derived separately, is also presented. The method combines existing fragility curves and thus is suitable for quickly assessing the reliability of a building's inventory, offering sufficient risk estimates.     

多层砌体房屋地震现场安全性鉴定子系统的研制与开发

本文利用模糊综合评判原理研究了多层砌体房屋地震现场安全性鉴定方法,并以此为基础研制了多层砌体房屋地震现场安全性鉴定子系统。本文将该子系统运用到两个实际问题中,所得结论与专家基于经验的现场鉴定相吻合,初步验证了系统分析模块的可靠性。     

Site dependence and record selection schemes for building fragility and regional loss assessment

When performing loss assessment of a geographically dispersed building portfolio, the response or loss (fragility or vulnerability) function of any given archetype building is typically considered to be a consistent property of the building itself. On the other hand, recent advances in record selection have shown that the seismic response of a structure is, in general, dependent on the nature of the hazard at the site of interest. This apparent contradiction begs the question: Are building fragility and vulnerability functions independent of site, and if not, what can be done to avoid having to reassess them for each site of interest? In the following, we show that there is a non‐negligible influence of the site, the degree of which depends on the intensity measure adopted for assessment. Employing a single‐period (e.g., first‐mode), spectral acceleration would require careful record selection at each site and result to significant site‐to‐site variability of the fragility or vulnerability function. On the other hand, an intensity measure comprising the geometric mean of multiple spectral accelerations considerably reduces such variability. In tandem with a conditional spectrum record selection that accounts for multiple sites, it can offer a viable approach for incorporating the effect of site dependence into fragility and vulnerability estimates. Copyright © 2017 John Wiley & Sons, Ltd.     

Rapid building damage assessment system using mobile phone technology

One common scenario during disasters such as earthquakes is that the activity of damage field reconnaissance on site is not well-coordinated. For example in Italy the damage assessment of structures after an earthquake is managed from the Italian Emergency Authority, using printed forms (AeDES) which are filled by experts on site generating a lot of confusion in filling and transferring the forms to the Disaster Management Operative Center. Because of this, the paper explores the viability of using mobile communication technologies (smart phones) and the Web to develop response systems that would aid communities after a major disaster, providing channels for allowing residents and responders of uploading and distributing information, related to structural damages coordinating the damage field reconnaissance. A mobile application that can be run by residents on smart phones has been developed, to give an initial damage evaluation of the area, which is going to be very useful when resources (e.g. the number of experts is limited). The mobile application has been tested for the first time during 2012 Emilia earthquake to enhance the emergency response, showing the efficiency of the proposed method in statistical terms comparing the proposed procedure with the standard procedure.     

Research on performance-based seismic design criteria

IntroductionAt present, the proper design and construction of buildings for earthquake-resistance is the most effective measure to mitigate the earthquake damage. In a broad sense, the earthquake resistance design should include the following seven contents:1) Determining the seismic design criteria Determining the seismic design goals3) Determining the seismic design parameters (intensity or ground motion) and their numerical values4) Determining the category of importance for buildings and …     

钢筋混凝土剪力墙的变形能力及基于性能的抗震设计

影响钢筋混凝土剪力墙变形能力的主要因素包括高宽比r、轴压比n、边缘约束构件约束程度等.本文首先建立了钢筋混凝土剪力墙端部约束构件的配箍特征值λvw、轴压比n、高宽比r与剪力墙极限位移Δuw之间的关系,即λvw-n-r-Δuw关系,然后通过7个研究机构所进行的钢筋混凝土剪力墙试验对该关系进行了验证.在此关系的基础上,本文提出了钢筋混凝土剪力墙基于性能的抗震设计方法.根据本文方法,设计者可以在已知层间位移角需求θ及确定损伤指标Dw的情况下对剪力墙端部约束构件进行配箍.本文最后通过一算例详细介绍了该方法的设计过程.     

基于性能的地震工程研究的新进展及对结构非线性分析的要求

结合国际地震工程界提出的新一代基于性能的地震工程的框架方法,重点阐述了性能评估中涉及的主要问题。对性能评估使用的静力非线性分析、动力非线性分析方法进行了总结,在此基础上详细阐述了在基于概率的性能评估中有应用前景的增量动力分析方法的概念、相关问题及其应用,并简要介绍了基于增量动力分析思想提出的一些简化方法。最后提出了今后研究的建议,特别是结构非线性分析方面的研究重点。     

A performance-based approach for design of ground densification to mitigate liquefaction

In performance-based geotechnical earthquake engineering, the required degree and spatial extent of ground densification for mitigation of liquefaction beneath a structure should be determined based on the acceptable levels of performance of foundation. Currently, there is no solution for evaluation of the amount of settlement and tilt of footings constructed on a densified ground which is surrounded by a liquefiable soil. This implies the need for numerical procedures for simulation of seismic behavior of shallow foundations supported on both liquefiable and densified subsoil. In this paper, the dynamic response of shallow foundations on a densified ground is studied using a 3D fully coupled dynamic analysis. For verification of the numerical model, simulation of a series of centrifuge experiments has been carried out and the results were compared with the experimental measurements. After verification of the numerical model, a comprehensive parametric study has been performed to develop a methodology for estimating the effectiveness of subsoil densification in reducing liquefaction-induced settlement of shallow foundations. Range of problem variables were considered in a way that the possibility of bearing capacity failure is low enough. The proposed methodology can be utilized for development of a performance-based design procedure for liquefaction hazard mitigation by soil densification.     

Post-earthquake building damage assessment in Yushu using airborne SAR imagery

The synthetic aperture radar (SAR) plays an important role in earthquake emergency response because of its all-time and all-weather imaging capabilities. On April 14, 2010, an MS7.1 earthquake occurred in Yushu county, Qinghai province of China, causing a lot of buildings collapsed. In this paper, the building damage in Yushu city due to the earthquake was assessed quantitatively using high-resolution X-band airborne SAR image. The features of the buildings with different damage levels (collapsed, partial collapsed, non-collapsed) in the SAR image were analyzed first. Based on these building features, we interpreted the individual building damage in Yushu city block by block and got the numbers of the collapsed, partial collapsed and non-collapsed buildings separately for each block, referring to pre-earthquake QuickBird image when necessary. Let the damage index of individual collapsed, partial collapsed, non-collapsed building be 1, 0.5, 0 respectively, the remote sensing damage index of each block was then calculated through remote sensing damage index equation. Finally, the preliminary quantitative relationship between the remote sensing damage index interpreted from the SAR image and that interpreted from the optical image was built up. It can be concluded that a desirable damage assessment result can be derived from high-resolution airborne SAR imagery.     

Consistent floor response spectra for performance-based seismic design of nonstructural elements

The achievement of adequate performance objectives for buildings under increasing seismic intensities is not only related to the performance of structural members but also to the behavior of nonstructural elements. The need to properly design nonstructural elements for earthquakes has been largely demonstrated in the last few years and has become an important objective within the earthquake engineering community. A crucial aspect in the proper design of nonstructural elements is the definition of the seismic demand in terms of both absolute acceleration and relative displacement floor response spectra. In the first part of this study, relative displacement and absolute acceleration floor response spectra were computed for four reinforced concrete moment-resisting archetype frames via dynamic time-history analyses and were compared with floor response spectra predicted by means of two recent simplified methodologies available in the literature. It was observed that one of the existing methodologies is generally unable to predict consistent absolute acceleration and relative displacement floor response spectra. An improved procedure is developed for estimating consistent floor response spectra for building structures subjected to low and medium-high seismic intensities. This new procedure improves the predictions of a relative displacement floor response spectrum by constraining its ordinates at long nonstructural periods to the expected peak absolute displacement of the floor. The resulting acceleration and relative displacement response spectra are then consistently related by the well-known pseudo-spectral relationship over the entire nonstructural period range. The effectiveness of the proposed methodology was appraised against floor response spectra computed from nonlinear time-history analyses.