The Research On Loading Efficiency In Load Test Of Small-span And Middle-span Beam Bridges

Short-span and middle-span beam bridges take a large proportion of the bridgeconstructures in our country, which makes it an extremely heavy task to examine thebearing capacity of bridges. In order to guarantee the effect in loading test, coefficient ofefficiency of static load test is adopted in choosing the magnitude and location of load. Interms of the value of coefficient of efficiency of static load test, it is rule to take the valueranging from0.95to1.05, according to The Regulation on Examining and Evaluating theBearing Capacity of Highways and Bridges(JTG/T J21—2011). It says that higherexperimental efficiency of bear load is demanded to be adopted for it can reflect themechanical characteristics of structures to the full extent in the process of changing andcomplex bearing load which is under the effects of various loads. However, there is nodetailed information about the influence of bridge types, loading conditions and loadinglocation towards testing efficiency, which is in need of further research.In this thesis,13meters hollow slab,20meters hollow slab,20meters composite boxbeam (continuous) and25meters composite box beam (continuous) were selected assamples to replace the contour with higher section models such as variable cross-sectionmodels modeling, calculating the characteristic and the influence line of transversedistribution of cross section. After doing that, asking bridge doctor to calculate design loadtransverse distribution coefficient and transverse distribution coefficient of the load test.Then a finite element can be established according to samples’ cross section, using Midas tomake single beam longitudinal bending moment and deflection respectively influence line, awhole section of longitudinal bending moment and deflection influence line. Differentsamples are loaded according to different working conditions of the configuration. As forhollow slabs and composite box girders (continuous), the edge of beam (plate) and thecenter sill (plate) of load effect must be calculated respectively and load according to thesingle beam effect, determining the test load position. The load effect, calculated on thebasis of the integral cross section, shall be carried out in accordance with the overall effectof cross section test load to determine the test load position. Finally, each test section isanalyzed by load test loading efficiency. Combining norms with practical use in bridgeloading test, beam bending moment effect and center sill effect is suggested to beconsidered for controlling loading efficiency with loading efficiency ranging from0.85to1.10.The result of the research thesis can be used as reference in later revision of relevant specification, as well as the the basis for evaluating load capacity of bridge structure.