Analysis Of Transverse Load Distribution And Overloading Effect Based On Space Beam Grillage Method

In order to analyse the accuracy of each effect by using the load transverse distribution coefficient, firstly the thesis use plate unit model to verify the accuracy of space beam grillage model.At the same time, the key effect of the beam grid model is provided to compare with the spatial influence of the vertical and horizontal influence lines of the single beam model.Then take simply supported T beam, box beam, hollow plate, four span continuous T beam and box girder with the same width different span and the same span different width in general map of the Highway Bridge as examples,correction coefficient of the single beam model method relative to space grillage method effect are given. The results show that the differences between shear effects are relatively large.The correction coefficient of bending moment is relatively small.In order to define the problem of selection of orthogonal grid or oblique grid in analysis of skew bridge by using the grillage method, take the 30°simply supported T beam and 30° simply supported box girder as examples, orthogonal grid building,oblique gridand plate element are respectively established,the results show that grid direction should be consistent with the middle cross beam direction if middle cross beam exists;orthogonal grid model is suggested to be built if there is no middle cross beam.In order to analyze the influence of the elastic brace and the rigidity brace on the supporting force, taking simply supported, continuous T beam and box girder as an example,the results show that the differences of simple supported T beam and continuous T beam and simply supported box girder are within 10%, while the difference of continuous box girder is relatively large that is about 15%.the lateral force of the structure is discussed through the setting of the cross diaphragm.In order to estimate the accuracy of the single beam model fundamental frequency and the fundamental frequency solved by the estimation formula in JTG D60—2004[S], take simply supported T beam, box beam, hollow plate, four span continuous T beam and box girder as examples, through the comparative analysis with space beam grillage method, the results show that the calculation method of relative calculation results of grillage method differences are less than 10%.The lane load as the design load in the calculation of the whole bridge in JTG D60—2004[S]General Specification for Design of Highway Bridges and Culverts, vague the overload standard in bridge, and effect of vehicle load on the structure is not clear. Take simply supported and continuous T beam with the same width different span and the same span different width as an example, analyse the standard value of the vehicle load and the effect of the overload vehicleload by using the space grillage method comparatively, the results show that the effect of overloading vehicles often happened in the actual operation on the structure is two times larger than the standard value of the vehicle load.The influence of the side beam is greater than that of the middle beam, and the influence of the negative moment of the top of the pier is greater than that of the middle beam. Two to four overweight vehicles are enough to reach the extreme value of the vehicle load effect for the medium and small span bridge.