Dynamic Characteristics of a Beam in an Existing Brick-concrete Structure

Abstract

With heavy hammer hammering method and road roller vibrating fixed-point method, field tests on dynamic characteristics were conducted for the brick-concrete structure beam of a teaching building. The experiment results of heavy hammer hammering method show that the horizontal and vertical natural frequencies of the heavy hammer are respectively concentrated in 2.726 ~ 5.313 Hz and 3.596 ~ 9.104 Hz, horizontal and vertical peak acceleration values are respectively 489.56 ~ 532.05 m/s2 and 248.77 ~ 494.61 m/s2; the natural frequency of the beam in horizontal direction is close to the vertical, first and second order natural frequencies are around 76.2 Hz and 125.2 Hz, horizontal and vertical peak acceleration values of each measuring point are respectively 1.58 ~ 4.02 m/s2 and 6.10 ~11.82 m/s2, and the peak acceleration follows the law of exponential decay. The experiment results of road roller vibrating fixed-point method show that the natural frequency of each measuring point in horizontal direction and the vertical is consistent, the first three order natural frequencies are 11.63 Hz, 39.94 Hz and 60.54 Hz in turn, and corresponding damping ratios are 0.010, 0.011 and 0.006; the peak acceleration in horizontal and vertical is respectively 0.4486 m/s2 and 0.1731 m/s2. The calculated frequency compared with test results, the first order natural frequency is basically the same, the second order and third order calculated frequencies are respectively larger 10.9% and 64.6% than test results.