| 摘要: | 目前規範只規定設計梁柱構件時，使用一般強度SD420以下鋼筋的剪力筋間距，故本文研究主要是測試高拉力鋼筋SD790，先行利用萬能試驗機做實驗，以伸長計控制鋼筋受拉與受壓應變之反覆振幅，來模擬梁柱構件受地震力，探討耐震設計中橫向箍筋反挫曲(anti-buckling)間距。
測試鋼筋採用D16與D13(一般強度為SD420、高強度為SD790)，主因是SD690大號鋼筋(如D25)適夾具以供測試。故觀察SD790-D13鋼筋與SD420-D13鋼筋，在不同間距(L/db =5.5、6)受到不同振幅作用(εa =±0.5、±1、±2、2.6,-0.4、3.6,-0.4%)，以及SD790-D16鋼筋與SD420-D16鋼筋在不同間距(L/db =4.5、5、6)受到不同振幅作用下(εa =±0.5、±1、±2、2.6,-0.4、3.6,-0.4%)，觀察鋼筋的壽命迴圈數(N¬f)。利用鋼筋壽命迴圈數結果計算材料常數(M、m)，以及觀察鋼筋在不同細長比下受反覆荷重的挫曲、斷裂情形。
測試結果顯示，SD790鋼筋第一迴圈與最終斷裂迴圈受力差異較S420鋼筋為小，但SD790鋼筋斷裂較無預警，其斷裂面較為平整。本文亦分析鋼筋測試數據求鋼筋之有效長度係數k，以及在非線性荷載階段之切線模數(Et)，以計算反挫曲之細長比s/db。結果顯示，¬SD420鋼筋細長比應小於6，如現行ACI318規範之規定，而SD790鋼筋細長比應小於4，故推算SD690-D25鋼筋細長比宜小於5為佳。
;The purpose of the study is to discuss the moderate anti-buckle spacing of SD790/690 rebar. This is because the present standard only specifies the spacing of transverse reinforcement for SD420 bars. Thus, the experiment used the universal testing machine with different bar slenderness ratio to simulate the column components subjected to earthquake loading.
Test specimens adopted 16mm and13mm diameter (common strength SD420 & high strength SD790). That is, SD690 bars normally used for larger diameter like D25 are not available to the testing machine at present. Therefore, SD790-D13 and SD420-D13 bars with different slenderness(s/db =5.5、6) and different amplitudes(εa =±0.5、±1、±2、2.6,-0.4、3.6,-0.4%), and SD790-D16 and SD420-D16 bars with different spacing(s/db =4.5、5、6) and different amplitudes(εa =±0.5、±1、±2、2.6,-0.4、3.6,-0.4%), are provided for the testing. By means of a series of test program, some parameters such as the number of life cycles, behavior of bar fracture and suitable bar slenderness ratio under the cyclic loading will be found.
Test results show the load difference between the first cycle and the final cycle for SD790 bars is smaller than that for SD420 bars. However, the SD790 bars are fractured without warning, and the breaking surface is smooth. This article also analyzes the rebars anti-buckling spacing by measuring the effective length coefficient(k) and non-linear steel modulus(Et) of the testing bars. Thus the slenderness ratio(s/db) of anti-buckling spacing for the rebars can be calculated. It repeals the SD420 bars of s/db shall be smaller than 6 as recent ACI318 suggested. The SD790 bars of slender ratio shall be less than 4.Therefore, the SD690 bars normally used for New RC main bars shall be less than 5. |
