Two failure modes ·Compression failure At failure The reinforcements at tensile zone do not yield in tension eo<eob 5>56 E,<8y 。Tension failure At failure The reinforcements at tensile zone yield eo-eob 5<56 Es>Ey
Two failure modes • Compression failure • Tension failure At failure At failure The reinforcements at tensile zone do not yield in tension e0<e0b b The reinforcements at tensile zone yield e0>e0b b s y s y
A,=A.f do<fy N. Nu (c) (d) (a) (b) (a)o=0(b)e<-a()>-(d0= 以上分析是基于A,=A,,若配筋量很大或很小，都会引起 failure mode的变化，如：偏心距较大，但是拉区配筋过大， 不屈服，变成压坏柱
以上分析是基于 ， 若配筋量很大或很小，都会引起 failure mode的变化， 如：偏心距较大，但是拉区配筋过大， 不屈服，变成压坏柱。 ' As As
6.2 Analysis and design of columns (N compression) ·Basic assumptions same as that in pure bending Conditions of compatibility same as that in pure bending Equilibrium equation T+C=T+N M=CZ+T(ho-a)-N(e+h/2-as) The equivalent rectangular block same as that in pure bending
6.2 Analysis and design of columns （N compression) • Basic assumptions same as that in pure bending • Conditions of compatibility same as that in pure bending • Equilibrium equation ( ) ( / 2 ) ' 0 ' ' M CZ T h a N e h as T C T N • The equivalent rectangular block same as that in pure bending
界限相对受压区高度ξb same as that in pure bending same as that in pure bending s 受拉区钢筋有可能屈服，有可能不屈服) when X≤Xb os =Jy X Xub o,<∫ h-1.25x 1.25x 0.8
' s same as that in pure bending s when ub x x s y f ub x x s y f s s s uEs x h x E 1.25 0 1.25 （受拉区钢筋有可能屈服，有可能不屈服） 1) 0.8 ( s u 界限相对受压区高度ξb same as that in pure bending
The approximate stress Os in over reinforced section 6☒0) 2000 行保代血贸高用受 导容 1000 0.81.6东 0 0.20.40.6 1.0i.2 88 8 5340 -0.0033E(3-) 5b=0.528 -1000F 8=合03 ￡-0.8 -f0.8 5-0.8 2000- Test result show:when0.8 , 0.8
Test result show：when 0.8 1) 0.8 ( s u The approximate stress s in over reinforced section