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 nonun...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.展开更多
Typically the selection of a residential heating system focuses on first costs rather than the economic or environmental life cycle consequences.The use of life cycle assessment and life cycle cost methodologies in th...Typically the selection of a residential heating system focuses on first costs rather than the economic or environmental life cycle consequences.The use of life cycle assessment and life cycle cost methodologies in the design phase provide additional criteria for consideration when selecting a residential heating system.A comparative case study of a gas forced air and radiant solar heating system was conducted for a 3,000 square foot house located in Fort Collins,Colorado,U.S.A.The initial results of an analysis of the life cycle assessment and the life cycle cost data indicated the gas forced air system was superior,both environmentally and economically.Further data analysis pinpointed solar radiant system components for replacement in an effort to reduce both life cycle environmental emissions and costs.This analysis resulted in a hybrid radiant system using a high-efficiency gas-fired boiler,a choice that lowered both the solar radiant system’s costs and emissions.This new system had slightly lower environmental impacts than both the gas forced air system and solar radiant system.Unfortunately the hybrid system had less impact on the life cycle cost with the hybrid system substantially more expensive then the gas-forced air alternative.展开更多
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,howev...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.展开更多
基金National Natural Science Foundation of China under Grant Nos.51921006 and 51725801Fundamental Research Funds for the Central Universities under Grant No.FRFCU5710093320Heilongjiang Touyan Innovation Team Program。
文摘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.
文摘Typically the selection of a residential heating system focuses on first costs rather than the economic or environmental life cycle consequences.The use of life cycle assessment and life cycle cost methodologies in the design phase provide additional criteria for consideration when selecting a residential heating system.A comparative case study of a gas forced air and radiant solar heating system was conducted for a 3,000 square foot house located in Fort Collins,Colorado,U.S.A.The initial results of an analysis of the life cycle assessment and the life cycle cost data indicated the gas forced air system was superior,both environmentally and economically.Further data analysis pinpointed solar radiant system components for replacement in an effort to reduce both life cycle environmental emissions and costs.This analysis resulted in a hybrid radiant system using a high-efficiency gas-fired boiler,a choice that lowered both the solar radiant system’s costs and emissions.This new system had slightly lower environmental impacts than both the gas forced air system and solar radiant system.Unfortunately the hybrid system had less impact on the life cycle cost with the hybrid system substantially more expensive then the gas-forced air alternative.
基金funded by the Ghent University Special Research Fund under grant 01N01219“Multi-objective societal optimization of structural fire safety investments for uncommon projects using advanced regression techniques”.
文摘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.
文摘为了兼顾电网经济与节能的双重目标,笔者基于全寿命周期成本(life cycle costs,LCC)理论,考虑节能因素,建立了一种新的变压器设计方案LCC评价方法。通过全面分析LCC各项组成,考虑负荷变化对负载损耗的动态影响,提出了更加完善的变压器LCC模型,并通过折现率与通货膨胀率对其进行了经济学修正。基于上述完善的变压器LCC模型,引入临界电价的概念,提出了损耗外LCC与损耗电量的对比分析方法,实现了一个变压器LCC评价辅助决策平台。以某500 k V变压器方案比选为例,论证了评价方法的实用性,并验证了其节能效果。
