載重不連續之平均值在擬動態實驗之應用

Average of Load Discontinuity Values for Pseudodynamic Testing

陳頡(Chieh Chen)

指導教授 ： 張順益

國立臺北科技大學/工程學院/土木與防災研究所/碩士(2009年)

https://doi.org/10.6841/NTUT.2009.00441

摘要

結構系統離散後的運動方程式在不連續的外力作用下，用較大的時間步長進行逐步積分法時會導致振幅誤差產生，為了克服外力不連續所產生的振幅誤差，便採用較小的時間步長。採用較小的時間步長，經過逐步積分法計算出的位移增量也相對較小，雖然在數值模擬下可以得到十分可靠的結果，但在進行擬動態實驗時，一旦位移增量接近或是小於量測儀器解析度的範圍，就有可能造成誤差掩蓋位移增量，導致不正確的實驗結果。同時較小的時間步長，也會拉長實驗所耗費的時間。本研究提出了一個克服衝擊載重不連續的擬動態實驗技術，只需在逐步積分法運算時，將衝擊載重的不連續點取其平均值，就可以消除由於外力不連續所引起的振幅誤差，因此可取較大的時間步長來進行實驗以防止誤差掩蓋的產生，而且在計算上不會增加計算量，減少了實驗的時間。透過數值模擬與擬動態實驗的驗證，可以更確定此法能夠消除外力不連續所導致的誤差。

關鍵字

擬動態實驗 ； 時間步長 ； 脈衝不連續

並列摘要

The discreted equation of motion under the discontinuous impulse with larger time step will lead to an amplitude distortion in the step-by-step integration. Meanwhile, a research found that the amplitude distortion arising from that discontinuity of impulse is proportional to the step size. In this case, we can reduce amplitude distortion by using the very small time step which can be a reliable aspect in numerically computing, but will cause an inaccurate result in the Pseudo dynamic Testing if the value of step increment is near or under the resolution of the measure system. In this research, the method is proposed to overcome the inaccuracy of discontinuity at the end of an impulse. As processing the step-by-step integration method, to replace the loading input by the average value of the two discontinuity value at the integration point of load discontinuity. Consequently, this method will not only increase no extra calculating in the step-by-step solution but also reduce the extra impulse and displacement to further confirm that it works in both the numerically simulating and the Pseudo dynamic Testing.

並列關鍵字

pseudodynamic test ； time step ； discontinuity in impulse

參考文獻

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