Life Cycle Assessment On Environmental Performance Of The Steel-UHPC Lightweight Composite Bridge Structures

There are two major diseases of the traditional orthotropic steel bridge deck,easy abrasion of the epoxy aphalt layer and fatigue cracking of the steel structure,bothering the bridge engineers around the world.In order to solve these problems,Shao Xudong,a Professor from Hunan University,has proposed a new structure called steel-UHPC light composite decks.Connecting through stud shear,UHPC(Ultra-high Performance Concrete)layer with dense reinforcement and the orthotropic steel deck are coordinated,which effectively reduces the fatigue stress of steel structure,thereby greatly reducing the probability of pavement damage and fatigue cracking of steel structure.For the long term,the steel-UHPC light composite bridge decks will be very friendly to the environment.To analyse the energy saving and carbon emission of the steel SUHPC lightweight composite bridge decks,this paper uses the life cycle evaluation method to evaluate its environmental impact assessment.The boundary condition of the life cycle model of bridge deck structures is based on the ISO 14,040:2006 of the life cycle framework established by International Standard Organization.The life cycle model of lightweight composite bridge decks consists of four stages,includeing raw material preparation,transportation,construction and operation maintenance.Through the research of various literatures,databases and engineering data,the energy consumption and carbon emission in the above four phases were identified,and the factors of energy consumption and carbon emission inventories were established.During the model establishing process,the discrete event method is applied to evaluate the environmental impact of the operation and maintenance stage.At the same time,the calculation methods of energy consumption and the carbon emission in each stage of the life cycle model are proposed,that improved the LCA(life cycle assessment)model of lightweight composite bridge deck structure.During the 100years life cycle of the bridge decks,the frequency of construction maintenance events is a key factor affecting the energy saving and emission reduction of bridge deck structure system.During the stage of construction and operation maintenance,the construction activities could cause the traffic delay of motor vehicles.To evaluate the environmental impact of the traffic delay,firstly,the paper uses the traffic simulation software,VISSIM4.3,to obtain traffic delay data of the bridge deck system,and then the motor vehicle exhaust emission list was obtained through the MOVES2014A,which is a software released by the U.S.Department of Environmental Protection.The result shows that,in the whole life cycle of bridge decks,traffic delay is the most important factor that can not be ignored for the environment assessment.As far as the lightweight composite deck structures,the energy consumption caused by traffic delays accounted for 80%of the total energy consumption of the life cycle.Meanwhile,the sensitivity analysis of three different traffic flow is made,and it is reasonable to determine the traffic flow rate of 2,400v/h.In this paper,the effect of the 10th cross orthotropic slab and the 11th cross steel-UHPC lightweight composite deck slab of the Mafang Bridge are compared.The result shows that the energy saving and emission reduction performance of light composite bridge deck structures are better than that of the traditional orthotropic plates,which decreases by 70%and 68%respectively in energy consumption and carbon emission.