ساخت و ساز و تجزیه و تحلیل هزینه های پل های بتنی مسلح FRP

This paper describes the use of FRP materials as reinforcements and formwork for a concrete highway bridge deck. It describes the construction process and provides a cost analysis of the project. A continuing research program at the University of Wisconsin–Madison is developing concepts for bridge decks reinforced with fiber reinforced polymers (FRP). This project involved the implementation of one of these concepts in a major highway bridge. Three forms of FRP reinforcing were combined to reinforce the concrete deck: FRP stay-in-place (SIP) forms, deformed FRP reinforcing bars (rebars), and a special prefabricated pultruded FRP reinforcing grid. The research project, supported by the Innovative Bridge Research and Construction Program (IBRC) in the United States, resulted in the construction of a two-span highway overpass on US Highway 151 in Wisconsin. Based on the analysis of the short-term material and labor costs it appears that given the savings in construction time and their potential long-term durability and maintenance benefits, FRP reinforcements for bridge decks may be cost-effective, notwithstanding their currently high initial costs. Optimization of FRP stay-in-place formwork is recommended to decrease the cost of the FRP reinforcing system in the future.

Corrosion of reinforcing steel is a main cause of deterioration of reinforced concrete bridge decks. Freeze–thaw cycles cause concrete cracking followed by corrosion and deterioration, limiting the lifespan of the bridge deck. The University of Wisconsin–Madison has worked in cooperation with the Wisconsin Department of Transportation (WisDOT), the Federal Highway Administration (FHWA), and Alfred Benesch and Company on research projects to extend the lifespan of reinforced concrete bridge decks by using non-corroding materials. The research projects involve the use of Fiber Reinforced Polymers (FRP) in place of conventional steel in bridge decks. A review of recent applications of FRP reinforcements can be found in [1]. While FRP stay-in-place forms and deformed rebar have been used previously in a highway bridge deck [2], this is the first combination of those materials along with a bi-directional FRP reinforcing grid panel selected to reduce construction cost. In addition, this is the first application where prestressed bridge girders were used and where “composite action” was required between the deck and the girders. Details of the design of the two-span reinforced bridge deck using these FRP materials and the development of special provisions that included a material specification for all FRP materials used have been described elsewhere [3] and [4]. That research culminated in the work reported here on the construction process and cost analysis of the FRP reinforced bridge deck.

During construction, data on the materials and labor were recorded to provide a comparison between the two bridges. The total material costs for the FRP reinforced bridge were $632,718. The material costs for the steel reinforced bridge were $391,649.53. This translates to over a 60% materials cost increase over the conventional construction (i.e., the materials for the bridge with the steel deck cost 3/5 that of bridge with the FRP deck). The cost of the individual FRP components was $167,637.60 (deck panels), $64,922.40(grid), and $25,369.10(rebar) for a total FRP material cost of $257,929.10. The cost of the steel reinforcement was $37,060.10. Since this was the first time FRP materials had been used as bridge deck reinforcement in Wisconsin, the FRP manufacturers and cost of the material were predetermined. They were both set in the FRP specifications prior to when the project was let for bidding. With competitive bidding between FRP manufacturers, increased use, and further design optimization, the cost of the FRP system, especially the deck panel (which accounted for over 26% of the total bridge cost), could decrease in the future. An advantage in the use of FRP materials was seen in labor savings. Five hundred and eighty five man-hours were required to install and remove the formwork on the steel reinforced bridge. The steel reinforcement was placed in 128 man-hours. Two hundred and six man-hours were required to place the polystyrene haunches and set the FRP deck panels in place. The two other components of the FRP reinforcement, the grid and rebars, were placed in 104 man-hours. A total of 713 h were spent on the decking and placement of reinforcement on the steel reinforced bridge deck compared to 310 h on the FRP reinforced bridge deck. This translates to a 57% savings in labor costs. An advantage was also seen in the productivity of the concrete pour. The rate of concrete placement on the FRP reinforced deck was 51.15 m3 (66.9 yd3) per hour compared with 29.05 m3 (38.0 yd3) per hour for the steel reinforced deck.