Research On Structural Characteristic Of A High Strength Light-weight Concrete Continuous Rigid-frame Bridge

Prestressed concrete continuous rigid-frame bridge is a main chosen of largespan bridges, which has such advantages as strong span ability, mature constructiontechnology, low cost of project, good appearance and comfort driving ect,.In recentyears, lots of continuous rigid-frame bridges has been built in our country, and thereare different extent diseases occurred with more than 80 percent of them, amongwhich excessive midspan lag and cracks in box girder are outstanding, which bringgreat harm to structural safety, and they become key technology problems to restrictfurther development of the continuous rigid-frame bridge. Theory and practice athome and abroad indicate that, it is a main approach to seek a perfect composedmatching from material characteristic and structure optimization, to solve excessivemid-span lag and cracks in box girder problems.There are so many advantages like light weight, high strength and good seismicresistance with High Strength Light Weight Aggregate Concrete(HSLC in short), whichmade it successfully applied on continuous rigid-frame bridge in foreign countries, suchas Stolma bridge and Raftsundet bridge in Norway. Research on HSLC continuousrigid-frame bridge is in starting stage, and it is blank in engineering application yet inChina. So, starting from material and structure optimization, a kind of continuousrigid-frame bridge with optimal matching combination of HSLC and normal concrete isput forwarded, and its structural characteristic is studied in this thesis, which solvedexcessive midspan lag and cracks in box girder in continuous rigid-frame bridgeeffectively in this thesis. The research results provide theoretical basis and technology forHSLC to be used on continuous rigid-frame bridge. It has important theoretic andpractical meaning to improve service life, to reduce the maintenance cost, and toguarantee the security of the bridge.Main research results are as follows:1.Development and present status of continuous rigid-frame bridge is introducedbriefly, and structural characteristic of it is expounded. Universal problems asexcessive midspan lag and cracks with continuous rigid-frame bridge are point outdefinitely. After that, a kind of continuous rigid-frame bridge with optimal matchingcombination of HSLC and normal concrete is put forwarded.2.Research on optimal matching relation of structure and material. From threeindices:stress level, structure deflection and internal force, structural characteristics of continuous rigid-frame bridge with different length, different density are studied. Theresearch results indicates:the best ratio of HSLC to normal concrete on continuousrigid-frame bridge is about 0.7. Low density HSLC reduced mid-span deflection,attenuated stress difference and negative moment more at section on top of frusta.3.Long-term deflection analysis of the bridge. Based on double characteristics ofHSLC, which are small density and low modulus, long-term deformability of HSLCcontinuous rigid-frame bridge are analyzed each under dead load, second period deadload and mid-span concentrate load. The research results indicate: HSLC minishedupper deflection in mid-span of continuous rigid-frame bridge; There is obviousinfluence on decreasing degree of the upper deflection with the time of load lasting.The longer the load lasts, the more decreasing degree of the upper deflection will be.4.Research on shear resistence and anti-cracking performance of box-girder.From aspects of shear force, shear stress and principle stress, shear resistence andanti-cracking performance of box-girder on HSLC continuous rigid-frame bridge wasstudied. The research results indicate:HSLC reduced shear force, shear stress of thebridge, increased principle stress reserving on the web, and improved anti-crackingperformance of the web on continuous rigid-frame bridge.Designable ability ofcontinuous rigid-frame bridge superstructure is improved.5.Dynamic characteristic analysis of the bridge. Subspace iteration method wasadopted to calculate natural frequencies, accumulative total contributing ratio ofmode shapes and vibration characteristics of HSLC continuous rigid-frame bridge.The research results indicate: HSLC depressed basic frequency and naturalfrequencies, which made dynamic response of the structure decreased.The research results in this thesis built a new approach for continuousrigid-frame bridge developing to large span, heavy load and light weight. It hasimportant theoretic and practical meaning to extend application field of HSLC,promoting the technology progress of large span continuous rigid-frame bridge, andstrengthening bridge and material subjects intercrossing.