Abstract
Dynamic load test of bridge is one of the important indexes to evaluate bridge operation and bearing capacity, however, the test of the lateral distribution of bridge is one of the important means to evaluate the state of bridge. In order to evaluate the stress condition and working performance of a box girder bridge in a mining area under the special load of 100T, dynamic load test and lateral load distribution are studied, dynamic load test is to test the natural vibration frequency damping ratio and impact coefficient of the bridge through pulsating test and traffic running test, the transverse distribution of load is analyzed by deflection method and the experimental value of transverse distribution coefficient is compared with the theoretical value of girder method. The results show that under dynamic load, the first vertical natural vibration frequency of the bridge is 10.986, the damping ratio is 0.015%, and the impact coefficient is 1.07~1.26, the vertical measured fundamental frequency is larger than the calculated fundamental frequency, and the overall stiffness of the bridge meets with the design specification; the transverse connection among the box girders is close and the lateral distribution of load meets with the requirement of the design specification.
Highlights
Project summaryK0+527.81 middle bridge is located in Shan Xin village, line S304 of provincial highway, across the Dian Xi river, the superstructure consists of 6x20m prestressed concrete box girder, its bridge span connection is simple and continuous; the substructure is composed of ribbed slab abutment, double column abutment and abutment pile foundation
As can be seen from table 1, with the speed of the vehicle increases, the impact coefficient increases significantly and the change is small, the dynamic strain curve with time is good, the maximum dynamic coefficient measured by the test is 1.26, the corresponding dynamic strain increment is 0.26, less than the theoretical calculation value of 0.39, it indicates that the bridge deck is comfortable
The vertical bending mode and theoretical mode of vibration mode and the measured mode shape of each the first and second order test, the calculation of the step of the vertical bending theory is shown in figure 5-8. It can be seen from table 2 and figure 5-8. the measured fundamental frequency is higher than the theoretical inherent fundamental frequency, it indicates that the measured structural stiffness is higher than the theoretical stiffness, the ratios of measured fundamental frequency and theoretical fundamental frequency in the first and second vertical bending were 1.131 and 1.073 respectively, meet with the requirements of the specification ≧0.9[7], it shows that the overall structure stiffness of the bridge is good; the vertical bending mode of the first and second order tests agrees well with the theoretical mode, the first and second order damping ratios were 0.015% and 0.022%, damping ratio is very small, it indicates that the overall performance of the bridge is good, the structure has strong anti-attenuation force
Summary
K0+527.81 middle bridge is located in Shan Xin village, line S304 of provincial highway, across the Dian Xi river, the superstructure consists of 6x20m prestressed concrete box girder, its bridge span connection is simple and continuous; the substructure is composed of ribbed slab abutment, double column abutment and abutment pile foundation. This bridge is 60m in length and 3 spans in total, the total width of the bridge is 0.5m+11m+0.5m, and the beam height is 1.8m, the bridge deck pavement is composed of 15cm thick C50 concrete and inorganic waterproof layer, the transverse slope of the bridge deck is 2% and the design load is 100T.
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