Study on Interactive Computer Program for Seismic Appraisal and Seismic Strengthening of R.C. Frame Structures

In many cases, seismic appraisal of existing structures is carried out by the two step method and seismic strengthening of R.C. frame structures is solved just based on rough calculation or experience of designers, which may lead to either lack of safety or too conservative in design. According to some related criteria and experts experience, a computer program is developed specially for seismic appraisal and seismic strengthening of R.C. frames (not more than 10 storeys) in this paper. Because the progra...

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.

Performance-based seismic design of nonstructural building components:The next frontier of earthquake engineering

With the development and implementation of performance-based earthquake engineering,harmonization of performance levels between structural and nonstructural components becomes vital. Even if the structural components of a building achieve a continuous or immediate occupancy performance level after a seismic event,failure of architectural,mechanical or electrical components can lower the performance level of the entire building system. This reduction in performance caused by the vulnerability of nonstructural components has been observed during recent earthquakes worldwide. Moreover,nonstructural damage has limited the functionality of critical facilities,such as hospitals,following major seismic events. The investment in nonstructural components and building contents is far greater than that of structural components and framing. Therefore,it is not surprising that in many past earthquakes,losses from damage to nonstructural components have exceeded losses from structural damage. Furthermore,the failure of nonstructural components can become a safety hazard or can hamper the safe movement of occupants evacuating buildings,or of rescue workers entering buildings. In comparison to structural components and systems,there is relatively limited information on the seismic design of nonstructural components. Basic research work in this area has been sparse,and the available codes and guidelines are usually,for the most part,based on past experiences,engineering judgment and intuition,rather than on objective experimental and analytical results. Often,design engineers are forced to start almost from square one after each earthquake event: to observe what went wrong and to try to prevent repetitions. This is a consequence of the empirical nature of current seismic regulations and guidelines for nonstructural components. This review paper summarizes current knowledge on the seismic design and analysis of nonstructural building components,identifying major knowledge gaps that will need to be filled by future research. Furthermore,considering recent trends in earthquake engineering,the paper explores how performance-based seismic design might be conceived for nonstructural components,drawing on recent developments made in the field of seismic design and hinting at the specific considerations required for nonstructural components.

Performance-based seismic financial risk assessment of reinforced concrete frame structures

Engineering facilities subjected to natural hazards(such as winds and earthquakes) will result in risk when any designed system(i.e.capacity) will not be able to meet the performance required(i.e.demand).Risk might be expressed either as a likelihood of damage or potential financial loss.Engineers tend to make use of the former(i.e.damage).Nevertheless,other non-technical stakeholders cannot get useful information from damage.However,if financial risk is expressed on the basis of probable monetary loss,it will be easily understood by all.Therefore,it is necessary to develop methodologies which communicate the system capacity and demand to financial risk,Incremental dynamic analysis(IDA) was applied in a performance-based earthquake engineering context to do hazard analysis,structural analysis,damage analysis and loss analysis of a reinforced concrete(RC) frame structure.And the financial implications of risk were expressed by expected annual loss(EAL).The quantitative risk analysis proposed is applicable to any engineering facilities and any natural hazards.It is shown that the results from the IDA can be used to assess the overall financial risk exposure to earthquake hazard for a given constructed facility.The computational IDA-EAL method will enable engineers to take into account the long-term financial implications in addition to the construction cost.Consequently,it will help stakeholders make decisions.

Performance-based concept on seismic evaluation of existing bridges

Conventional seismic evaluation of existing bridges explores the ability of a bridge to survive under significant earthquake excitations. This approach has several major drawbacks, such as only a single structural performance of near collapse is considered, and the simplified approach of adopting strength-based concept to indirectly estimate the nonlinear behavior of a structure lacks accuracy. As a result, performance-based concepts that include a wider variety of structural performance states of a given bridge excited by different levels of earthquake intensity is needed by the engineering community. This paper introduces an improved process for the seismic evaluation of existing bridges. The relationship between the overall structural performance and earthquakes with varying levels of peak ground acceleration （PGA） can successfully be linked. A universal perspective on the seismic evaluation of bridges over their entire life-cycle can be easily obtained to investigate multiple performance objectives. The accuracy of the proposed method, based on pushover analysis, is proven in a case study that compares the results from the proposed procedure with additional nonlinear time history analyses.

Peak displacement patterns for the performance-based seismic design of steel eccentrically braced frames

Performance-based seismic design(PBSD) aims to assess structures at different damage states. Since damage can be directly associated to displacements, seismic design with consideration of displacement seems to be logical. In this study, simple formulae to estimate the peak floor displacement patterns of eccentrically braced frames(EBFs) at different performance levels subjected to earthquake ground motions are proposed. These formulae are applicable in a PBSD and especially in direct displacement-based design(DDBD). Parametric study is conducted on a group of 30 EBFs under a set of 15 far field and near field accelerograms which they scaled to different amplitudes to adapt various performance levels. The results of thousands of nonlinear dynamic analyses of EBFs have been post-processed by nonlinear regression analysis in order to recognize the major parameters that influence the peak displacement pattern of these frames. Results show that suggested displacement patterns have relatively good agreement with those acquired by an exact nonlinear dynamic analysis.

Probabilistic Performance-Based Optimum Seismic Design Framework: Illustration and Validation

In the field of earthquake engineering,the advent of the performance-based design philosophy,together with the highly uncertain nature of earthquake ground excitations to structures,has brought probabilistic performance-based design to the forefront of seismic design.In order to design structures that explicitly satisfy probabilistic performance criteria,a probabilistic performance-based optimum seismic design(PPBOSD)framework is proposed in this paper by extending the state-of-the-art performance-based earthquake engineering(PBEE)methodology.PBEE is traditionally used for risk evaluation of existing or newly designed structural systems,thus referred to herein as forward PBEE analysis.In contrast,its use for design purposes is limited because design is essentially a more challenging inverse problem.To address this challenge,a decision-making layer is wrapped around the forward PBEE analysis procedure for computer-aided optimum structural design/retrofit accounting for various sources of uncertainty.In this paper,the framework is illustrated and validated using a proof-of-concept problem,namely tuning a simplified nonlinear inelastic single-degreeof-freedom(SDOF)model of a bridge to achieve a target probabilistic loss hazard curve.For this purpose,first the forward PBEE analysis is presented in conjunction with the multilayer Monte Carlo simulation method to estimate the total loss hazard curve efficiently,followed by a sensitivity study to investigate the effects of system(design)parameters on the probabilistic seismic performance of the bridge.The proposed PPBOSD framework is validated by successfully tuning the system parameters of the structure rated for a target probabilistic seismic loss hazard curve.The PPBOSD framework provides a tool that is essential to develop,calibrate and validate simplified probabilistic performance-based design procedures.

Research on performance-based seismic design criteria

The seismic design criterion adopted in the existing seismic design codes is reviewed. It is pointed out that the presently used seismic design criterion is not satisfied with the requirements of nowadays social and economic development. A new performance-based seismic design criterion that is composed of three components is presented in this paper. It can not only effectively control the economic losses and casualty, but also ensure the building's function in proper operation during earthquakes. The three components are: classification of seismic design for buildings, determination of seismic design intensity and/or seismic design ground motion for controlling seismic economic losses and casualties, and determination of the importance factors in terms of service periods of buildings. For controlling the seismic human losses, the idea of socially acceptable casualty level is presented and the 'Optimal Economic Decision Model' and 'Optimal Safe Decision Model' are established. Finally, a new method is recommended for calculating the importance factors of structures by adjusting structures service period on the base of more important structure with longer service period than the conventional ones. Therefore, the more important structure with longer service periods will be designed for higher seismic loads, in case the exceedance probability of seismic hazard in different service period is same.

Performance-based global reliability assessment of a high-rise frame-core tube structure subjected to multi-dimensional stochastic earthquakes

When evaluating the seismic safety and reliability of complex engineering structures,it is a critical problem to reasonably consider the randomness and multi-dimensional nature of ground motions.To this end,a proposed modeling strategy of multi-dimensional stochastic earthquakes is addressed in this study.This improved seismic model has several merits that enable it to better provide seismic analyses of structures.Specifically,at first,the ground motion model is compatible with the design response spectrum.Secondly,the evolutionary power spectrum involved in the model and the design response spectrum are constructed accordingly with sufficient consideration of the correlation between different seismic components.Thirdly,the random function-based dimension-reduction representation is applied,by which seismic modeling is established,with three elementary random variables.Numerical simulations of multi-dimensional stochastic ground motions in a specific design scenario indicate the effectiveness of the proposed modeling strategy.Moreover,the multi-dimensional seismic response and the global reliability of a high-rise frame-core tube structure is discussed in detail to further illustrate the engineering applicability of the proposed method.The analytical investigations demonstrate that the suggested stochastic model of multi-dimensional ground motion is available for accurate seismic response analysis and dynamic reliability assessment of complex engineering structures for performance-based seismic resistance design.

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.

Introduction to Technical Specification for Seismic Appraisement and Strengthening of Buildings in the Province of Sichuan

On May 5, 2008, China experienced a devastating earthquake, also known as Wenchuan earth-quake. Many buildings, whose seismic design levels were too low to endure a strong earthquake, were severely damaged or even destroyed in the disaster.

某高校综合楼抗震性能鉴定方法研究

工程检测行业中涉及的民用建筑的鉴定主要包括可靠性鉴定、抗震性能鉴定和危险房屋鉴定。本文从抗震性能鉴定的背景出发,介绍了《建筑抗震鉴定标准》(GB 50023-2009)中存在的瑕疵,及《既有建筑鉴定与加固通用规范》(GB 55021-2021)的改进,结合某高校一栋框架结构的综合楼抗震性能鉴定实例,总结了民用建筑抗震性能鉴定的主要思路,对于同类型工程项目抗震性能鉴定有一定的参考意义。

美国既有建筑抗震性能评估标准简介及与我国标准的对比

对美国既有建筑抗震性能评估标准的发展历程进行了简要梳理,根据ASCE/SEI 41-17介绍了美国既有建筑抗震性能评估标准的基本思路、框架和主要内容。ASCE/SEI 41-17是一部完全基于性能的抗震性能评估标准,采用ASCE/SEI 41-17进行抗震性能评估首先应确定建筑抗震性能目标,包括结构性能水准和非结构性能水准。美国既有建筑抗震性能评估程序分为三级,第一级为筛查,第二级为基于缺陷的抗震性能评估,第三级为系统性评估。与《建筑抗震鉴定标准》(GB 50023—2009)进行了对比,并进行了相关讨论。两国标准在抗震性能评估理念上有诸多相近之处,但在具体方法上有较大差异。美国标准直接进行中大震作用下的抗震性能评估,而我国标准采用小震验算并结合抗震措施评估进行综合鉴定的方法。此外美国标准中还有利用基准建筑进行抗震性能评估的简化方法,值得我国标准借鉴。

某多层厂房改造前结构安全性鉴定及抗震性能评估

该文针对某多层厂房在改造前的结构安全性及抗震性能进行了系统的鉴定与评估。通过现场检测和竣工图纸的分析,建立了相应的模型,对厂房的结构承载力和抗震性能进行了深入研究。厂房为地下二层、地上三层的框架-剪力墙结构,建筑总高度18.50 m,设计使用年限为50年,抗震设防类别为丙类,地震设防烈度为6度。现场调查显示,厂房目前处于闲置状态,未发现明显的沉降或裂缝现象。通过对基础和上部主体结构的检测,结果表明混凝土强度和构件尺寸均满足设计要求,但部分构件的钢筋配置不符合规范。结构承载力和抗震能力的计算分析结果显示,结构承载力和抗震承载力均满足要求,但个别构件的抗震措施需进行加固。最终,鉴定结果将该厂房的安全性等级评定为Bsu级,为后续的改造加固提供了技术支持。

大型煤棚安全性及抗震鉴定分析

文中以某大型煤棚工程为例,采用多种检测方法对该煤棚进行了全面检测,通过三维建模对其进行承载力计算,综合检测及承载力计算结果,对该煤棚进行了安全性鉴定和抗震鉴定,全面分析了该煤棚在荷载作用下的强度、刚度、稳定性,可为类似工程检测鉴定项目提供参考。

某超限高层房屋安全性鉴定与抗震鉴定

针对某超限高层框架-核心筒结构房屋现状的安全性,分析了在地震作用下该房屋的抗震性能。根据现场检测数据及建模计算结果,参照现行规范对该房屋进行安全性检测鉴定,鉴定结果为Asu级。对该房屋结构体系和抗震构造措施进行检测,检测结果均满足规范要求;通过建模对该房屋进行结构抗震计算并采用弹性时程分析法进行多遇地震下的补充计算,结果表明该房屋轴压比、结构最大层间位移角、周期比、剪重比等指标满足规范要求,房屋在地震作用下的承载力满足要求。

既有加固后砌体结构的检测鉴定研究

既有建筑的安全及抗震鉴定中,涌现出越来越多进行过加固的砌体结构。为了明确既有加固后砌体结构具体的鉴定内容及鉴定方法,论文对相应的检测鉴定规范、加固设计规范及施工验收规范进行了总结和归纳,给出了采用砌体结构中常用加固做法的检测重点及计算分析方法,并结合项目实例进行了具体的探讨,以期为后续既有加固工程的检测鉴定提供参考和指导,促进工程检测鉴定技术的标准化。

某混合结构高层建筑的抗震鉴定

混合结构是高层建筑中常见的一种结构类型,但是GB 50023-2009《建筑抗震鉴定标准》对此类建筑的抗震鉴定没有明确的规定。论文以一栋2002年竣工的混合结构高层建筑为例,探讨了此类建筑的抗震鉴定原则及方法,可以为此类建筑的抗震鉴定提供参考。

既有建筑鉴定中主体结构整体牢固性及抗震措施检查方法探析

针对当前既有建筑鉴定中需同时进行安全性鉴定和抗震鉴定的要求,通过作者实际工作中的经验,结合相关的技术标准规范,梳理出结构鉴定中结构整体牢固性及抗震措施检查方法的各类要求并整理成各个表格,方便从事鉴定工作的人员在实际鉴定中明确主要关注的要点,避免因现场鉴定人员能力不同,造成的缺项漏项的情况,避免遗漏检查内容,造建筑物存在重大安全隐患,对建筑的最终安全性评级及抗震鉴定造成影响,达到提升现场鉴定人员的鉴定水平,确保结构安全。通过以上方法的探析供从事结构鉴定相关技术人员在实际工作中使用。

某底层框架砖房结构检测鉴定

随着经济的不断发展,城市更新项目越来越多,由于历史原因,城市中存在大量的底层框架砖砌体结构房屋,多建于20世纪七十年代到九十年代,由于底层为框架结构,刚度薄弱,整体抗震性能较差,在历次震害中破坏也比较严重。文章基于某实际工程的安全性检测鉴定和抗震鉴定结论,对该房屋的后期改造提出相关处理建议,为后期类似工程的改造更新提供参考依据。