Reliability-based life-cycle cost seismic design optimization of coastal bridge piers with nonuniform corrosion using different materials

Reinforcement corrosion is the main cause of performance deterioration of reinforced concrete(RC)structures.Limited research has been performed to investigate the life-cycle cost(LCC)of coastal bridge piers with nonuniform corrosion using different materials.In this study,a reliability-based design optimization(RBDO)procedure is improved for the design of coastal bridge piers using six groups of commonly used materials,i.e.,normal performance concrete(NPC)with black steel(BS)rebar,high strength steel(HSS)rebar,epoxy coated(EC)rebar,and stainless steel(SS)rebar(named NPC-BS,NPC-HSS,NPC-EC,and NPC-SS,respectively),NPC with BS with silane soakage on the pier surface(named NPC-Silane),and high-performance concrete(HPC)with BS rebar(named HPC-BS).First,the RBDO procedure is improved for the design optimization of coastal bridge piers,and a bridge is selected to illustrate the procedure.Then,reliability analysis of the pier designed with each group of materials is carried out to obtain the time-dependent reliability in terms of the ultimate and serviceability performances.Next,the repair time of the pier is predicted based on the time-dependent reliability indices.Finally,the time-dependent LCCs for the pier are obtained for the selection of the optimal design.

Seismic Risk Assessment of Buildings in the Extended Urban Region of Athens and Comparison with the Repair Cost

A complete research of seismic risk assessment is presented herein focused on the existing build- ings of the extended urban region of Athens in Greece. The seismic risk assessment is fulfilled by discriminating the current study in two approaches, probable and actual, conducting afterwards between them a comparison analysis. In the first part, a pilot methodology is developed for the seismic loss assessment in monetary terms regarding the buildings damages, consistent with the National Programme for Earthquake Management of Existing Buildings (NPEMEB). The building stock consists of typical building types of Southern Europe and refers to 750,085 buildings (18.80% of buildings in Greece) situated in the entire region of Athens according to the results of the 2000-1 statistical census. A wider research of seismic risk assessment could include direct losses of infrastructures and indirect economic losses. The evaluation of loss due to building damage in a certain region requires an assessment of both seismic hazard and vulnerability of the building stock in the study area. Four different existing damage scenarios are applied for the vulnerability assessment. The results of the seismic risk assessment for the four different aspects of the es- timated damage and the different soil conditions are presented in a map of the study region. The existing vulnerability curves corresponding to defined types of buildings have been derived from the National Technical Chamber of Greece and also from recently developed DPMs. The last DPMs were obtained in a previous research (Eleftheriadou, 2009) from the process of a created damage database after the 7th of September 1999 Parnitha’s earthquake and comprised 180,945 buildings which developed damage of varying degree, type and extent. In the second part of the research, the seismic risk is evaluated from the available data regarding the mean statistical repair/ strengthening or replacement cost for the total number of damaged structures (180,427 buildings) after the same (1999 Parnitha’s) seismic event. Data regarding the compatible (budget approved according to the ministry’s provisions) repair cost has been collected. The structural losses in monetary terms for the 180,427 buildings damaged structures are evaluated equal to 2450.0 Μ€, 1887.8 Μ€ and 2118.9 Μ€ based on the previously mentioned statistical seismic risk data. The statistically derived repair cost for Attica is compared with the results of the economic loss esti- mation for buildings using the aforementioned risk assessment methodology. From the analysis results, the seismic scenario based on the recently developed DPMs (Eleftheriadou, 2009) pre- sented the better correlation (2627.77 M€) with the total statistically evaluated repair cost (2450.02 M€). It is important to stress that the inclusion of the coefficient parameter S overes- timates significantly the seismic losses. The last result should be taken into consideration in future risk researches. The comparison of the estimated economic loss with the statistical repair cost calibrates the reliability of the commonly used risk assessment method and serves in the im- provement of seismic security prioritizing the criteria for seismic rehabilitation programmes of existing buildings.

Cost-optimization based target reliabilities for design of structures exposed to fire

Adequacy of structural fire design in uncommon structures is conceptually ensured through cost-benefit analysis where the future costs are balanced against the benefits of safety investment.Cost-benefit analyses,however,are complicated and computationally challenging,and hence impractical for application to individual projects.To address this issue,design guidance proposes target reliability indices for normal design conditions,but no target reliability indices are defined for structural fire design.We revisit the background of the cost-optimization based approach underlying normal design target reliability indices then we extend this approach for the case of fire design of structures.We also propose a modified objective function for cost-optimization which simplifies the evaluation of target reliability indices and reduces the number of assumptions.The optimum safety level is expressed as a function of a new dimensionless variable named“Damage-to-investment indicator”(DII).The cost optimization approach is validated for the target reliability indices for normal design condition.The method is then applied for evaluating DII and the associated optimum reliability indices for fire-exposed structures.Two case studies are presented:(i)a one-way loaded reinforced concrete slab and(ii)a steel column under axial loading.This study thus provides a framework for deriving optimum(target)reliability index for structural fire design which can support the development of rational provisions in codes and standards.

Seismic Resilience Analysis of a Concrete-Framed Hospital Building with Viscous Dampers

To study the seismic resilience of a concrete-framed hospital building with viscous dampers,the elastoplastic time history analysis of a three-story concrete-framed hospital building under moderate and rare earthquakes was carried out by finite element analysis software.The structure’s overall response was studied,meanwhile,the seismic resilience of the building was evaluated from three aspects:repair cost,repair time,and casualties.The results show that viscous dampers can effectively reduce the repair cost,repair time,and casualties under earthquakes.Compared with the structure without dampers,the repair cost and repair time of the structure with dampers have been reduced by 67%and 69%respectively under moderate earthquakes,42%and 39%respectively under rare earthquakes,and the seismic resilience grade has been increased from zero to one star.

Performance-based system seismic assessment for long-span suspension bridges under two-level seismic hazard

Since there are few studies on the performance-based seismic evaluation of the long-span suspension bridge system under two-level earthquake hazard in Chinese code,the developed procedure of this study can be regarded as a general program to assess the seismic performance of the overall system for long-span suspension bridges.In the procedure,the probabilistic seismic demand models of multiple bridge components were developed by nonlinear time-history analyses incorporating the related uncertainties,and the component-level fragility curves were calculated by the reasonable definition of limit states of the corresponding components in combination with seismic hazard analysis.The bridge repair cost ratios used to evaluate the system seismic performance were derived through the performance-based methodology and the damage probability of critical components.Furthermore,the repair cost ratios of the overall bridge system that was retrofitted with fluid viscous dampers for the main bridge and changed restraint systems for the approach bridges were compared.The results show that peak ground velocity and peak ground acceleration can be selected as the optimal intensity measurements of long-span suspension bridges using the TOPSIS(technique for order preference by similarity to an ideal solution).The bridge repair cost ratios can serve as accurate evaluation indicators to provide an efficient evaluation of retrofit measures.The seismic evaluation of long-span bridges is misled when ignoring the interaction of adjacent structures.However,the repair cost ratios of a bridge system that has optimum seismic performance are less sensitive to the relative importance of adjacent structures.

Seismic resilience of building inventory towards resilient cities

Resilience of a community after an extreme event depends on the resilience of different infrastructure including buildings.There is no well-established approach to characterize and integrate building resilience for community-level applications.This paper investigates how different potential functionality measures can be used to quantify building resilience indexes,and how the results could be aggregated for a set of buildings to provide an indi-cator for the resilience of an entire community.The quantification of building resilience is based on different functionality measures including repair cost,occupancy level,and asset value.An archetype city block with four different buildings is defined.The individual results for each building are combined using a weight-based ap-proach to quantify the resilience index for the city block.The study then considers small-scale communities with different number of buildings to investigate the influence of contractor availability and collapse probability on the resilience indexes for the set of buildings.Both parameters are shown to be important when quantifying the resilience index.It is also demonstrated that the overall resilience of a community is directly influenced by the resilience of individual buildings.The findings presented here are useful both from the perspective of quantifying the resilience of a community on the basis of its building inventory,as well as for possible inclusion into a holistic framework that aims to quantify community resilience.

Spring tube braces for seismic isolation of buildings

Abstract： A new low-cost seismic isolation system based on spring tube bracings has been proposed and studied at the Structural and Earthquake Engineering Laboratory of Istanbul Technical University. Multiple compression-type springs are positioned in a special cylindrical tube to obtain a symmetrical response in tension and compression-type axial loading. An isolation floor, which consists of pin-ended steel columns and spring tube bracings, is constructed at the foundation level or any intermediate level of the building. An experimental campaign with three stages was completed to evaluate the capability of the system. First, the behavior of the spring tubes subjected to axial displacement reversals with varying frequencies was determined. In the second phase, the isolation floor was assessed in the quasi-static tests. Finally, a scaled 3D steel frame was tested on the shake table using actual acceleration records. The transmitted acceleration to the floor levels is greatly diminished because of the isolation story, which effects longer period and higher damping. There are no stability and self- centering problems in the isolation floor.

考虑资源稀缺性的路面养护措施综合效益全寿命周期费用评估

为提高道路工程中不可再生资源利用的合理性,建立养护措施综合效益的全寿命周期费用评价方法,推动交通运输基础设施的可持续发展,基于全寿命周期费用评价(life-cycle cost assessment,LCCA)理论,引入了资源稀缺性的评价指标,并基于存量稀缺、进口稀缺和技术稀缺3个评价维度,建立了适用于路用材料的项目级资源稀缺性评价体系,同时,将该指标量化为货币当量计入成本清单中。依托江苏省路面养护管理系统数据,将资源稀缺性、经济效益、性能发展3个维度统一,定量分析了再生类、铣刨重铺类和罩面类共3类、12个常见养护措施的综合效益。研究结果表明:考虑资源稀缺性,再生类养护措施旧料利用率较高,具有极佳的资源合理性;EC A-10薄层罩面处治厚度薄、耗材量小,与普通罩面相比能节省50%左右的资源;铣刨料直接废弃、石料来源选择不当将导致额外支出10%~20%的当量成本。考虑综合效益,各养护方案与施工特性(如施工工期、施工水平、工艺先进性等)相关的成本效益接近60%,其中用户间接的经济损失占比超过30%,直接由施工工期决定。因此,建议谨慎选择材料来源及去向以减少不可再生资源浪费,优化养护施工流程以降低用户的间接经济损失,提高施工水平以降低用户的直接油耗开支,开展科学养护决策以降低政府投入成本。

Cost Impact of Increasing Heavy Vehicle Loads on Bridges

This study aimed to investigate the cost impact of meeting the increase in freight demand by doubling the truck weight （AS 1 ）, doubling the traffic volume （AS2）, or legalizing a new-proposed-truck of 97-kip weight instead of the currently legal 80-kip truck （AS3）. The State of Michigan＇s average daily traffic database of year 2001 has been used as a case study. The study was applied only on the very common US Bridge with RC （reinforced concrete） deck over steel girder. Sampling criteria also includes the age of the bridges. The study covered the four-cost-impact categories provided by the NCHRP （National Cooperative Research Program）. The current truck weight and double traffic volume （AS2） show the best scenario to meet the increase in freight demand. However, doubling the truck weight with the current traffic volume （AS 1） was the worst scenario. The use of the proposed 97-kip truck with the current traffic volume （AS3） compromises both, meeting the increase in freight demand and the cost impact.

考虑填充墙力学贡献的规范RC框架办公楼抗震韧性评价

提升建筑结构的抗震韧性是当前工程界抗震减灾的核心任务,根据现代规范设计的钢筋混凝土框架尽管具有较高的抗倒塌安全储备,但其韧性能力并不明确。既有研究在量化结构抗震韧性时,均仅采用结构构件的地震响应作为输入,忽略了非结构构件对整体结构地震响应的影响。针对上述问题,该文根据规范最低要求,设计一栋六层钢筋混凝土框架办公楼,并对其抗震韧性进行评价,明确了该办公楼的抗震韧性与《建筑抗震韧性评价标准》中建议的韧性目标的差距,揭示各类构件对结构韧性的影响。对比研究了填充墙力学贡献对办公楼抗震韧性的影响。研究结果表明:该六层框架办公楼的修复费用主要来源于填充墙和暖通类设备的修复工作,而修复时间主要由结构构件和填充墙的修复时间组成。填充墙的力学贡献会提高该办公楼的抗震韧性,减少结构构件和位移型非结构构件的修复费用和时间约50%,但对加速度型非结构构件的影响较小。

Analysis on carbon emission reduction intensity of fuel cell vehicles from a life-cycle perspective

The hydrogen fuel cell vehicle is rapidly developing in China for carbon reduction and neutrality.This paper evaluated the life-cycle cost and carbon emission of hydrogen energy via lots of field surveys,including hydrogen production and packing in chlor-alkali plants,transport by tube trailers,storage and refueling in hydrogen refueling stations(HRSs),and application for use in two different cities.It also conducted a comparative study for battery electric vehicles(BEVs)and internal combustion engine vehicles(ICEVs).The result indicates that hydrogen fuel cell vehicle(FCV)has the best environmental performance but the highest energy cost.However,a sufficient hydrogen supply can significantly reduce the carbon intensity and FCV energy cost of the current system.The carbon emission for FCV application has the potential to decrease by 73.1%in City A and 43.8%in City B.It only takes 11.0%–20.1%of the BEV emission and 8.2%–9.8%of the ICEV emission.The cost of FCV driving can be reduced by 39.1%in City A.Further improvement can be obtained with an economical and“greener”hydrogen production pathway.

Life-cycle cost analysis of optimal timing of pavement preservation

Optimal application of pavement preservation or preventive maintenance is critical for highway agencies to allocate the limited budget for different treatments. This study developed an integrated life-cycle cost analysis （LCCA） model to quantify the impact of pavement preservation on agency cost and vehicle operation cost （VOC） and analyzed the optimal timing of preservation treatments. The international roughness index （IRI） data were extracted from the long-term pavement performance （LTPP） program specific pavement studies 3 （SPS-3） to determine the long-term effectiveness of preservation treatments on IRI deterioration. The traffic loading and the initial IRI value significantly affects life extension and the benefit of agency cost caused by pavement preservation. The benefit in VOC is one to two orders greater in magnitude as compared to the benefit in agency cost. The optimal timing calculated based on VOC is always earlier than the optimal timing calculated based on agency cost. There are considerable differences among the optimal timing of three preservation treatments.

基于全寿命效费比的地铁上盖隔震(振)结构优化设计方法

隔震(振)技术是提升地铁上盖建筑抗震性能和舒适度的有效措施,优化此类结构设计方法具有现实意义和紧迫性。提出了适用于地铁上盖隔震(振)结构的全寿命效费比评估模型;采用基于结构响应的全寿命评估方法,研究了周期比、质量比、隔震层刚度及阻尼等关键结构参数对地铁上盖隔震(振)结构效益的影响;基于遗传算法提出了地铁上盖隔震(振)结构优化设计方法。研究结果表明:增加隔震层后结构地震损失主要集中于下部结构,上、下部结构质量比越大地震损失越小;上下部结构周期比越大,地震损失越小;隔振层刚度与隔振效益呈正相关;采用提出的优化算法对原型结构优化后,地震损失费用可减小30%,竖向振动加速度级可减小2 dB,验证了该方法的可行性。

不同剪力墙平面布局结构抗震性能及造价分析

文中以贵阳某高层住宅建筑为例,对不同剪力墙平面布局条件下结构的抗震性能及造价情况进行分析。结果表明,随着偏心率的增加,剪力墙结构的结构周期、层间位移以及层间位移角不断降低,其抗震性能有所下降;偏心率越高,所需的钢筋及混凝土材料用量均越大,导致造价更高;所有构件中墙体的总造价占比约63%。因此,未来进行平面布置时,应综合其抗震性能以及工程造价进行优选。

Life-Cycle and Seismic Fragility Assessment of Code-Conforming Reinforced Concrete and Steel Structures in Bucharest, Romania

In this article, the fragility of reinforced concrete and steel structures in Bucharest, a city of high seismic hazard, designed using the recent building codes in Romania, is assessed. A total of 24 reinforced concrete and steel structures with heights varying from five stories to 13 stories were analyzed. Their seismic fragility was evaluated using two procedures from the literature. In the first procedure(SPO2 FRAG), the fragility was derived based on the pushover curves using the SPO2 IDA algorithm, while in the second procedure(FRACAS), the fragility was derived from nonlinear time-history analyses. The analyzed structures were designed for three levels of peak ground accelerations, corresponding to mean return periods of 100,225, and 475 years. Subsequently, the damage assessment of the analyzed structures was performed using ground motions generated from a Monte-Carlo simulated earthquake catalogue for the Vrancea intermediate-depth seismic source. The damage degrees that were estimated using the SPO2 FRAG approach are higher than those estimated using the FRACAS approach. The life-cycle analysis of the structures shows that a further increase of the design peak ground acceleration for Bucharest is feasible from an economic point of view using the SPO2 FRAG results.However, based on the FRACAS results, the opposite conclusion can be drawn. Finally, generic lognormal fragility functions are proposed as a function of building height and structural system.

Design,simulation of different configurations and life-cycle cost analysis of solar photovoltaic-water-pumping system for agriculture applications:use cases and implementation issues

Water is an essential resource for agriculture and the majority of land is irrigated through borewells or wells.The power requirement for an irrigation pump motor is fed by the on-grid power supply but the availability of electricity in rural areas is still questionable.With rising concerns about global warming and the rise in carbon footprints,it is necessary to choose clean and green energy,thereby attaining self-sustainable life.India receives yearly a mean solar irradiation of 6.5 kWh/m^(2)day.Hence,a solar photovoltaic-water-pumping system(SPV-WPS)is a suitable alternative to grid energy;thereby,the farmers would generate electricity through the solar photovoltaic system and become self-sufficient in their energy needs.In this paper,two different agricultural fields in Tamil Nadu,India that deploy flood irrigation and drip irrigation are taken as a case study.The paper discusses the concerns on the use of grid power and their carbon footprint,design and simulation of 4-and 5.5-kW SPV-WPSs using PVsyst 7.1.1,and the advantages of using SPV-WPSs and life-cycle cost analysis on different use cases.The Government of India has introduced a special scheme to promote the installation of SPV-WPSs by offering attractive incentives through PM-Kisan Urja Suraksha evam Utthaan Mahabhiyan(KUSUM)yojana.The results of the case study show that with the use of SPV-WPSs,either with or without subsidy,the farmer could gain a minimum of 250%on the investment with a project lifetime of 25 years.

钢筋沥青隔震层实际工程应用与推广

主要介绍一种新型隔震层的研究、应用与推广,该隔震技术成果包括钢筋-沥青隔震层和钢筋-沥青水平隔震墩。试验研究结果表明该技术有很好的隔震性能,并且价格低廉、施工方法简单,适用于广大农村地区的建筑,也可推广至第三世界国家的农村地区使用。其中的钢筋-沥青隔震层技术已经应用于工程实际,并且对已建成的实际工程进行测试,测试结果表明该技术的减震效果非常好,该实际工程是中国首幢采用这种新型隔震层的房屋,总体造价没有增加。钢筋-沥青水平隔震墩技术的提出,更加方便了该技术在村镇地区民居建筑的中使用。

一种低成本无缆地震仪采集站的研制

随着电子技术的发展,许多新技术被应用到地球物理仪器之中.其中,无缆地震仪采集站具有重量轻、易搬运的特点,适宜应用于如森林、沼泽、沙漠等地面状况复杂的区域,可以在复杂地质条件下方便地进行地震数据采集,是未来地震仪发展的方向.本研究研发了一种低成本无缆地震仪采集站,通过分析无缆地震仪的发展方向,确定了采集站的设计方案,该系统采用了微功耗设计,GPS授时同步与低成本晶振相结合的时钟机制,并设计了基于多项分解的软件滤波器提高24位Σ-ΔADC的动态范围,其低成本、小体积、低功耗的特点使其非常适用于复杂区域下的资源勘探,并可应用于高密度、宽方位等物探新技术当中.

最优性价比的观测系统设计方法研究

三维观测系统优化设计是野外地震采集工作的一个重要环节,影响着后期地震资料采集处理解释的各个工作环节.因此,高质量的观测系统设计是地震勘探工作的关键,然而在无限制的追求高信噪比、高分辨率的地震资料,高难度的野外施工的同时,这往往会带来较大的成本投入.鉴于以上存在的问题,文章着重分析质量最优和成本最优的观测系统设计,通过寻找观测系统参数与采集质量和采集成本的关系,结合二者的优点,提出了最优性价比的观测系统优化设计方法,并通过一个实际工区的试验,体现出该方法的应用效果,为高质量的观测系统设计提供新的思路和方法.

基于“投资-效益”准则的抗震性能目标优化决策

以结构在地震作用下的破坏程度为依据将结构性能水平划分为五级,并选取结构的层间位移角为定量控制指标,建立了"结构破坏程度结构性能水平层间位移角"之间的对应关系.该划分细化和量化了现行规范规定的三级性能水平,为设计人员和业主提供更多选择,使结构抗震设计更加灵活.同时以"投资效益"准则为基本原则,结合地震危险性分析,建立了改进的结构全寿命总费用模型.该模型不仅考虑了结构的初始造价,而且充分根据结构性能失效的特点考虑了结构在各级性能水平下的损失期望,全面注重了结构性能、安全及社会经济等因素,为实现基于性能的结构抗震设计提供了有效的理论依据和可靠的计算方法.