Research On Near-fault Strong Motion Record Baseline Correction Experiment System

For a variety of reasons influence, near-fault strong ground motion records usually have the baseline drift problem, that is inappropriate baseline correction would lead to unconventional result or effectively vibration information loss. In the existing research, a series of baseline correction methods were proposed, but the methods have been not the final answer to solve the problem, because of too much subjectivity and conclusion uncertainty of the methods. In our work, some studies were done on the problem based on the current researches.In our work, the studies on the near field strong record baseline correction method were summarized, the cause of the baseline drift was analyzed, the methods proposed in the past studies were summarized, and the problems in the methods were pointed out.For measuring the vibration displacement directly in the shake-table test, in our work, a non-contact dynamic displacement measurement system were developed on MATLAB GUI platform, basing on the movie image processing technology. And the system’s measurement accuracy was discussed by a simple benchmark experiment. In the experiment, the influence of different label schemes and video frame speed were discussed. Based on the test results, we proposed the optimization experiment scheme for the direct vibration displacement measurement under our laboratory conditions.Then, according to the near-fault strong motion observation actual situation, we proposed a new shake-table experiment scheme to verify the record reliability under the accelerometer installed by rotating or tiling in a certain angle and permanent displacement happening conditions. The experiments show that under the single-direction load condition, the record in the loading direction could be corrected to the real value by simple mathematical formula whether the accelerometer installed by rotating or tiling in a certain angle. And the displacement time history and permanent displacement obtain by integrate and correction on the strong motion accelegram could be basically in agreement with the values measured directly under the single-direction load condition.Finally, the work pointed out the direction and thinking of the related researches.