| Medium and small span bridges in China are characterized by large capacity and wide coverage,however there are many problems in the traditional small and medium span prefabricated girder bridges,such as monotony of structural forms and materials,poor quality of construction,and deficiency of durability.In order to diversify the structures of small and medium span bridges,improve the quality of highway bridges and promote the industrialization process of bridge,this paper systematically reviewed the domestic and foreign prefabricated forms of medium and small span bridges,and introduced the I-shaped steel plate composite girder bridge and I-shaped PC composite girder bridge,which are widely used in developed countries such as Europe and the United States.Two types of bridges are designed based on the current editions of specifications in China,this paper deeply studied the bearing capacity of the two types of bridges.Subsquently,the structural safety,efficiency in construction and economy of these types of bridges are discussed.The main tasks completed in this paper are as follows:(1)This paper analyzes and compares the characteristics and structural conditions of traditional prefabricated PC girder bridges in China and steel-concret or a variety of concrete composite beam bridges which are widely used in Europe and America.Based on the concept of bridge industrialization,the notion that medium and small span girder bridge assembly system is introduced,which is called ?three systems,two connections and two splices?,the existing bridge types are evaluated.Thus,the I-shaped steel plate composite girder bridge and I-shaped PC composite girder bridge are recommended as the main type of medium and small span prefabricated concrete girder bridge and steel-concrete composite girder bridge.(2)Based on the ABAQUS finite element software,the finite element models of steel plate composite beam and PC beam are established.The accuracy of the simulation is verified by comparing with the typical test results.Based on standard drawings of steel plate composite girder bridge in the United States,steel-concrete composite plate girder bridges in 20-40 m span are preliminary designed according to Chinese specifications.The ABAQUS finite element software is used to investigate the mechanical performance of the full-bridge and single beam based on specifications in China and those in the United States.It is researched by the finite element software ABAQUS how composite girder bridges with double girders and those with multiple girders are destroyed.The study have shown that steel composite girder bridges designed based on Chinese specifications are much safer than those designed based on the U.S specifications.The disaster resistance of composite bridges with double girders are weaker than those with multiple girders.(3)The load test of the 30 m bare beam and composite beam of PC composite beam bridges were carried out to analyze the prestressed loss resulting from friction,relationship between load and deflection,concrete strain at the mid of bridge,development of crack and behavior of bending failure.The formula of the prestressed loss in the form of fold line resulting from friction is given while the pull-plate strand restraining device is used.Experimental studies show that the deck of composite beam bridge contribute to the resistance for bending moment and effectively improve the behavior of beam under bending moment.It is verified that current edition of prestressed concrete design specifications in China is suitable for the PC composite beam design.(4)From the perspective of material consumption,the economics of two kinds of composite beam,T-beam and small box girder are studied.The technical characteristics such as the constructability,speedability of components replacement and the controllability of quality are analyzed.The suggestions for promoting the composite beam bridge come up along with the reflecting on the design concept,specification and steel varieties etc. |
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