本研究主要在探討配置低鋼筋量之鋼筋混凝土梁分別受到純扭力，扭力與剪力以及扭力與彎矩組合載重作用下之行為，本研究另依據試驗結果探討ACI 318-05與AASHTO LRFD設計規範中與扭力相關設計規定之適用性。本研究根據34根全尺寸鋼筋混凝土梁試體之測試資料，其中包括16根梁試體受純扭力作用、11根梁試體受扭力與剪力組合載重作用、6根梁試體受扭力與彎矩組合載重作用以及1根梁試體受純彎矩作用以進行分析比較。主要研究變數為實心與空心斷面、斷面深寬比值、斷面之鋼筋比值、混凝土抗壓強度、Tu /Vu比值以及T/M比值。
本研究結果顯示如下：
1. 配置低鋼筋量的鋼筋混凝土梁試體之預留扭矩強度值主要受到斷面之抗扭箍筋與縱向鋼筋量比值的影響而並非其總抗扭鋼筋量來控制。
2. ACI 318-05規範對構件受扭力與剪力組合載重作用下最大容許剪應力限制公式之保守性隨Tu /Vu比值增加而提高。
3. 在相同鋼筋量與Tu /Vu比值條件下，空心斷面試體之實測開裂強度、極限強度值小於實心斷面試體。
4. 試體因受到不同組合剪應力所產生之側向曲率會隨Tu /Vu比值減小而先增加後下降，且空心斷面試體之側向曲率大於實心斷面試體。
5. 受扭力與彎矩組合載重作用試體表面混凝土平均主壓應變最大值發生位置會因T/M比值的增加，由試體頂面轉移至側面，進而改變其破壞模式。
6. 試體斷面在受到扭力與彎矩組合作用力下所能提供之變形能量密度則會隨著扭力作用的增加而顯著減小，且試體之開裂扭矩勁度值則會因扭力的增加而減小。
7. AASHTO LRFD設計規範對於構件受扭力與彎矩組合載重作用下的縱向鋼筋量限制公式，可以合理地預測試體之扭矩與彎矩強度互制關係的變化趨勢。

The behaviors of reinforced concrete beams with lower amounts of torisonal reinforcement subjected to pure torsion, combined torsion and shear, and combined torsion and bending, respectively, are investigated. The associated specifications in the torsion design specified in the ACI 318-05 and AASHTO LRFD Codes are also discussed. Test results of thirty-four reinforced concrete beam specimens were used, including sixteen specimens subjected to pure torsion, eleven specimens subjected to combined torsion and shear, six specimens subjected to combined torsion and bending, and one specimen subjected to pure bending, respectively. The main parameters included the solid and hollow sections, volumetric ratio of torsional reinforcement, aspect ratios of the cross section, compressive strength of concrete, torsion to shear (Tu /Vu) ratios, and torsion to bending (T/M) ratios.
The significant results are listed as follows:
1. The adequacy of post-cracking reserve strength for specimens with relatively low amount of torsional reinforcement is primarily related to the ratio of transverse to longitudinal reinforcement factor in addition to the total amounts of torsional reinforcement.
2. The allowable shear stress of ACI 318-05 code for members subjected to combined shear and torsion would become more conservative when the Tu /Vu ratios increase.
3. Under the same condition of Tu/Vu ratios and the amount of reinforcement, the test cracking and ultimate strengths of specimens with hollow sections are lower than those with solid sections.
4. The test lateral curvatures of the specimens increased, and then decreased with the decrease of Tu /Vu ratios. The hollow section specimens had larger lateral curvature than solid section specimens.
5. The location of the maximum average principal compressive strain of concrete shifted from the top to back side of the specimens due to the increase of the T/M ratios, and the failure modes were also changed.
6. The deformation energy densities of the specimens subjected to combined torsion and bending decreased with the increase of torsion. In addition, the ratio of the cracked torsional stiffness also decreased with the increase of torsion.
7. The specification of the amounts of longitudinal reinforcements for the reinforced concrete beam subjected to combined torsion and bending in the AASHTO LRFD provisions can be used to rationally predict the strength interaction of the specimens.

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