5.3 Limitation of neutral axis depthx and three types of failure
5.3 Limitation of neutral axis depth xub and three types of failure
0.0033ε 问题1：那种情况的配筋量多？ 问题2：配筋量多到一定程度，会怎样？ ③ ② ① 问题3：可以用什么方法判断超筋？ 破坏时钢筋的应变 Es Ey 混凝土受压区高度 配筋率 极限弯矩 Os
0.0033ε ③ ② ① 问题1：那种情况的配筋量多？ σs εs εy 问题2：配筋量多到一定程度，会怎样？ 问题3：可以用什么方法判断超筋？ 破坏时钢筋的应变 混凝土受压区高度 配筋率 极限弯矩
At balanced state The relationship among the depth of neutral axis and the maximum concrete strain and steel strain has been given by 8,-， eu=0.0033 Xba Xba The depth of the neutral axis is then ho Xba ho 1+ sy=fy/Es
• The relationship among the depth of neutral axis and the maximum concrete strain and steel strain has been given by • The depth of the neutral axis is then u ba ba y x h x 0 u y ba h x 1 0 a xba h0 εu=0.0033 εy=fy/Es At balanced state
The ultimate strain of concrete =0.0033;and for the HRB400 steel (fy=360N/mm2),the yield strain & 0.001797. ho Xba=- =0.6475ho 0.001797 1+ 0.0033 Hence,to ensure yielding of the tension steel at the ultimate limit state: xa≤0.6475ho
• The ultimate strain of concrete cu = 0.0033; and for the HRB400 steel (fy = 360N/mm2), the yield strain y = 0.001797. 0 0 0.6475 0.0033 0.001797 1 h h xba • Hence, to ensure yielding of the tension steel at the ultimate limit state: xa 0.6475h0