Study On Wind-Induced Vibration Of Long Span Half-through Arch Bridges

Long span half-through arch bridges belong to flexible structure. The buckling under static wind, buffet and vortex shedding vibration will take place easily. Be differ from the long span cable-stayed bridges and suspension bridges, the long span half-through arch bridges belong to 3D structure. The coupled vibration between girder and arches should be taken into account when calculating wind induced response. The wind loads on arches are complex. Some factors, such as wind speeds changing with height and loads spatial correlation and interference between two arches should be taken into account. The vortex shedding vibration will take place at the relative low wind speed because of arches blunt section. So the static stability analysis, the buffeting analysis, the vortex-excited vibration analysis are discussed according to the long span arch bridges features. The research is mainly focused on the following aspects:(1) The wind loads and interference of single arch and double arches are analyzed. Exampled on the Chongqing Caiyuanba Yangzi river bridge, the wind tunnel tests of single arch and double arches are carried out. The numerical simulations of tunnel tests are analyzed. The results show that drag force coefficients variability is small, and lift coefficients variability and moment variability are big. Arch forces coefficients and fluctuating buffeting forces are mainly decided by the space width ratio and the relatively vertical displacement.(2) The methods of long span half-through arch bridges displacement response analysis under the static wind loads are developed. The yield and static stability mechanism of long span half-through arch bridges are analyzed. The results show that the responses are bigger when the static forces nonlinear are taken into account. The internal forces and displacements are bigger at the same wind speed. The static wind initial angle and material yield value have great effects on the limited wind speed. The construction stage limited wind speeds depend on the construction towers'stability.(3) The method of calculating wind power spectrum density (PSD) before two arches is presented. By the fluctuated pressure tunnel tests, the fluctuating wind loads on arches are analyzed. According to the single arch buffeting forces PSD, the ratios between two arches buffeting forces PSD are calculated by equivalent root mean square (RMS), then the wind PSD before two arches are solved. The results show that the method is effective.(4) The finite element method of long span half-through arch bridges couple frequency domain buffeting vibration analysis is derived. The change of wind speed with the height is taken into account. The square root of the sum of squares (SRSS) and complete quadratic combination (CQC) and pseudo excited methods are adopted on the...