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.

Degradation process assessment of prestressed concrete continuous bridges in life-cycle

To accurately evaluate the degradation process of prestressed concrete continuous bridges exposed to aggressive environments in life-cycle,a finite element-based approach with respect to the lifetime performance assessment of concrete bridges was proposed.The existing assessment methods were firstly introduced and compared.Some essential mechanics problems involved in the degradation process,such as the deterioration of materials properties,the reduction of sectional areas and the variation of overall structural performance caused by the first two problems,were investigated and solved.A computer program named CBDAS(Concrete Bridge Durability Analysis System) was written to perform the above-metioned approach.Finally,the degradation process of a prestressed concrete continuous bridge under chloride penetration was discussed.The results show that the concrete normal stress for serviceability limit state exceeds the threshold value after 60 a,but the various performance indicators at ultimate limit state are consistently in the allowable level during service life.Therefore,in the case of prestressed concrete bridges,the serviceability limit state is more possible to have durability problems in life-cycle;however,the performance indicators at ultimate limit state can satisfy the requirements.

A Direct-Indirect Cost Decision Making Assessment Methodology for Seismic Isolation on Bridges

Making decisions of when to intervene on bridges taking into consideration more than owner costs is a growing field of interest in earthquake engineering. In particular, bridges can be considered critical links in highway networks because of their seismic vulnerability in terms of direct and indirect losses. This paper aims at defining a general criteria capable of taking into account both these costs in a simplified and efficient formulation. Indirect losses generally neglected elsewhere, are taken into consideration by applying a formulation that assesses investment efficiency. The presented formulation follows the one proposed for buildings by L. Kantorovich, 1975. Direct costs are computed from a Performance Based Earthquake Engineering （PBEE） methodology by the Pacific Earthquake Engineering Research （PEER） center. The problem considers two competitive objectives （maximizing economic efficiency and minimizing costs） in a multi-objective structural optimization procedure. The formulation has been applied to a case study aimed at strengthening a benchmark bridge. The optimum investment has been assessed between several isolated configurations.

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.

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.

Comparative analysis of cast-in-place post-tensioned and steel-concrete composite bridge bent caps

The complexity of the IH-635 Managed Lanes Project, located in Dallas County, Texas, posed several technical and constructive challenges, leading to the adoption of solutions different from the traditional. Two alternative solutions for the pier cap on one of the bridge crossings over IH-35E in the IH-635 project were analyzed in this case study, a cast-in-place post-tensioned concrete cap and an innovative prefabricated steel-concrete com- posite cap. The approach was to use an estimation of direct costs for material and labor and consideration of con- struction time schedules. A supplementary numerical modeling confirmed that both alternatives behave elasti- cally under imposed loads. The direct cost of material and labor for the two alternatives were close. However, the composite alternative required 13 days less construction time, resulting in substantial cost savings from traffic closing in the very busy traffic corridor. Traffic closing costs were substantially higher than the direct costs, especially for the post-tensioned cap. The quantification of the benefits allows more confidence in the utilization of the composites caps, leading to faster completion of bridge projects and substantial economic savings.

Economic Impact of Higher Timber Truck Loads on Louisiana Bridges

Due to the limited amount of funds available for bridge inspection, maintenance and rehabilitation, the evaluation of load capacity for existing bridges is crucial to the Louisiana Department of Transportation and Development. This paper includes the development of a methodology to assess the economic impact of overweight vehicles with permits, hauling Louisiana harvest products on state bridges. The proposed higher truck loads are applied on the existing bridges and their effects are determined using deterministic load capacity evaluations as well as reliability assessments. The target rehability level is derived from bridge structures designed to satisfy AASHTO Standard Design Specifications and also satisfy safe and adequate performance levels. The amount of harvest produced is used to select a representative sample of bridges to provide specific examples of expected changes in load ratings and safety levels. The bridges include simple and continuous span behavior. Strength and serviceability criteria are investigated under current legal loads and the expected changes, due to the proposed new weights, are determined. The results are used to assess the cost of crossing a bridge and the permit fees for the proposed truck weight regulation.

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。

混凝土桥梁结构全寿命可持续性成本量化模型

为了在规划设计阶段定量化地考虑工程结构的环境和社会影响,提出一种综合性的全寿命可持续性成本指标框架和计算模型。在环境影响方面,将空气、水体和土壤污染物的防治成本作为量化指标,提出工程活动、交通绕行和交通拥堵引起的环境成本模型,汇总常见建筑材料和燃料动力的环境成本费率。在社会影响方面,提出社会成本量化模型,涵盖施工和交通安全、客货运输、区域经济、居住环境和公共服务等方面。以沿海桥梁维护方案比选为例,说明全寿命可持续性成本的参数取值和计算方法。结果表明,对于占用车道的桥梁维修方案,环境和社会成本之和远超直接经济成本,而不占用车道的维护方案的环境和社会成本很少,其中环氧涂层方案的可持续性优于电化学除氯方案。

基于路径概率的桥梁全寿命成本计算方法及例证

为解决传统桥梁全寿命设计方法在工程实践中遇到的设计概念模糊、计算方法不明确及与相关规范脱节的不足,以提高公共安全与交通舒适度,降低建造和运营综合成本,提出了基于路径概率并与可靠度结合的混凝土桥梁全寿命成本计算方法。首先,在深入研究桥梁全寿命设计的基础上,依据调研所得桥梁管养投入实际数据,拟合了不同服役地区不同桥梁等级的检测成本计算公式,以及不同公路等级不同养修成本的养修成本取值区间,以此构建了桥梁全寿命成本计算基准。其次,以钢筋在氯离子侵蚀和碳化耦合作用下的锈胀开裂模型为基础,采用路径概率方法构建了桥梁全寿命养修概率模型。然后,通过蒙特卡洛法进行求解,并将养修方案、养修成本通过可靠度指标联系起来,结合规范中关于正常使用极限状态指标的相关规定,提出基于可靠度的全寿命成本计算方法。最后,采用所提方法计算了不同桥梁设计方案在设计使用寿命期内的养修概率,综合建造成本、检测成本和养修成本估算全寿命成本及其对应的可靠度。结果表明:不同可靠度指标的取值对设计方案的全寿命成本有显著影响,随着可靠度指标的提高不同设计方案的经济性均出现先上升后下降的趋势。因此,设计过程目标可靠度的取值不宜过大,可通过一个较低的可靠度指标,适当放宽耐久性设计准入,以允许桥梁在使用过程出现一定的耐久性问题,并通过后续养修进行矫正,这样对于全寿命成本而言,更具有经济性。

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.

基于能源桩的桥面融雪系统经济效益评估

基于能源桩的桥面融雪系统,利用清洁绿色的地热能为道路融雪除冰,从而降低碳排放,与我国“双碳”战略发展趋势相契合。在技术落地过程中,实现优化设计从而降低成本至关重要。通过数值模拟方法,研究了该系统在中国不同气候区的产热量,并计算了三级融雪目标下桥面融雪所需热量。同时,建立了成本测算模型,分析了各气候区代表城市最具经济效益的能源桩融雪方案,并基于该模型开发了计算软件,以简化应用流程。研究结果表明:在短期运行中,桥面建安费和热泵费用是对成本影响最大的因素。然而,在长期运行中电价成为最关键因素;当热通量需求变化时,电力融雪系统的总成本增量约为能源桩融雪系统的2倍;在恶劣气候环境和更严苛的融雪目标下,能源桩融雪系统的相对节省曲线更陡峭,优势显著;此外,国家政策的积极支持能弥补该系统初始投资成本高的短板,增强其市场竞争力。

道路桥梁工程造价的影响因素及降低工程造价措施分析

分析了项目设计和规划、项目设计和规划,以及施工阶段各因素对道路桥梁工程造价的影响,总结了降低工程造价的措施,包括建立完善的造价控制体系,优化施工设计过程,采用先进的造价控制方式,优化工程造价成本管理,完善责任管理制度,优化工程项目成本的过程控制,旨在提高道路桥梁建设中的工程经济效益。

基于全寿命周期的波形腹板钢箱混凝土组合梁桥成本分析

波形腹板钢箱—混凝土组合梁桥作为一种预制结构桥梁,因其结构新颖、施工周期短、自重轻的特点,已在桥梁建设中得到了广泛应用。本文以甘肃景中机场连接线一座波形腹板钢箱—混凝土组合梁桥为例,考虑资金时间价值,采用不同社会成本折现率对该桥全寿命周期成本进行详细的预测分析。结果表明:波形腹板钢箱—混凝土组合梁桥全寿命周期成本受成本分析折现率的影响较大,成本分析折现率越高,全寿命周期成本就越低。另外,随着成本分析折现率增大,建设投资期成本占比增大,运营服役期、拆除回收期成本占比减小。本文的研究结论可为该类型桥梁的投资决策和方案比选提供参考。

桥梁承台深基坑钢板桩围堰施工成本预测分析

制订桥梁承台深基坑开挖钢板桩围堰施工方案,并根据施工方案设计现场劳动力与材料等施工参数;利用鸡群算法优化极限学习机的权重与偏置,把经过优化后的权重和偏置输入极限学习机模型中,构建最好的极限学习机模型;在最佳极限学习机模型内输入施工参数,输出施工成本预测结果,完成桥梁承台深基坑开挖钢板桩围堰施工成本预测。以贵州省重点工程——乌当(羊昌)至长顺高速公路工程TJ-8标段羊昌河大桥为研究对象,进行相关的试验测试。试验结果证明:该方法可有效预测桥梁承台深基坑开挖钢板桩围堰施工时,钢板桩围堰打入阶段与基坑清淤及支撑阶段等不同施工阶段人工费与材料费等成本,成本预测的残差与相对误差均较低。

城市特大景观桥梁的建设造价指标分析

以郑州西四环奥体大桥工程为例,通过对下部基础、桥塔上部及桥墩、主梁及拉索、附属工程、供电照明及防雷接地5个部分进行探讨,分析了郑州西四环奥体大桥的基本组成材料及其造价。结果表明,特大工程建设造价指标的合理分析,能反映各时期工程建设各要素的市场价格变动,有利于顺利开展后期的工程报价与工程结算,为控制项目的成本提供合理的依据。

基于遗传算法的路网级桥梁养护与安全分析

随着交通网络的发展和桥梁结构的老化,养护工作变得更加重要,而传统的养护决策存在工作繁琐、效率低下的问题。因此,研究提出建立桥梁安全风险分析体系,并借助带精英策略的非支配排序遗传算法进行路网级桥梁养护决策。试验结果显示,研究方法在150次迭代后完成收敛,共得出100种有关竹埠港湘江大桥养护的决策。选择其中具有代表性的决策进行分析,考虑次要结构时最优决策经费为252万元,效益费用比达到0.99,不考虑次要结构的最优决策经费为129万元,效益费用比为1.60。且养护后撞击力降低了44.91%,吸收撞击能量提高了38.13%。研究为路网级桥梁的养护与安全风险分析提供了系统、科学的方法,对于提高桥梁养护效益、减少养护成本,以及确保桥梁结构安全具有积极意义。

桥梁工程拉森钢板桩造价合理确定的研究

在市政、公路工程中,拉森钢板桩主要用于河道围堰、基坑支护等临时性工程。本文针对桥梁工程拉森钢板桩造价应用实例进行了研究和总结,发现在确定其造价时出现了套用相关定额计算造价与实际造价差异较大的问题,对产生此问题的原因进行了分析,并论述了如何合理确定拉森钢板桩造价。

桥梁与隧道方案全寿命周期费对比研究——以龙潭过江通道为例

本文通过计算分析形成全寿命周期费用比选图并得出结论:桥梁方案建设期总投资为70.54亿,全寿命周期费用测算值为79.18亿,全寿命周期费用约为建设期总投资的1.12倍。隧道方案建设期总投资为101.16亿,全寿命周期费用测算值119.56亿,全寿命周期费用约为建设期总投资的1.19倍。桥梁方案建设期总投资相比隧道方案节约30.62亿,全寿命周期费用相比隧道方案节约40.85亿。按照全寿命周期费用进行对比,龙潭过江通道应选择投资偏低的桥梁方案。

分析市政斜拉桥造价水平控制因素

在城市建设中,市政工程造价体系在不断完善,但特殊结构桥梁还存在定额不全,以及自身特点对造价水平控制影响因素较多,给造价编制带来很多不可控风险。基于此,论文以石家庄某市政斜拉桥为例,分析对比桩基工程、桥塔结构组成、钢箱梁的使用、桥面铺装以及施工措施等影响因素对造价水平的影响,为工程设计、技术方案的科学合理选择提供经济依据。