PKIC 结构设计原理 Teprimepledstmicturgdesign B 9 c- 分分 C D The picture shows a simply supported beam without web reinforcement,the role of two symmetrical concentrated loads(CD segment called the pure bending section;AC cut curved section and DB section above)
The picture shows a simply supported beam without web reinforcement, the role of two symmetrical concentrated loads (CD segment called the pure bending section; AC cut curved section and DB section above) B A' D' 1 C' C B σ τ 2 3 A a a F F B' 2 1 3 σcp σtp σcp σtp σcp σtp τ2 σ σ τ1 τ3 2 1 3 >45o 45o <45o 主拉应力 主压应力
JPKIc 结构盘注原裸 Point 2:compressive stress o makes oip decrease andoep increase,a>45 2← Point 1:neutral axis,=0,=T max.a=45 Point 3:tensile stress o makes oip increase and oep decrease,a <45
B A' D' 1 C' C B σ τ 2 3 A a a F F B' 2 1 3 σcp σtp σcp σtp σcp σtp τ2 σ σ τ1 τ3 2 1 3 >45o 45o <45o 主拉应力 主压应力 。 Point 1: neutral axis, = 0, = max, = 45 。 decrease and increase,α > 45 Point 2 : compressive stress makes cp tp 。 increase and decrease,α < 45 Point 3: tensile stress makes cp tp
JPKIc 结构设计原理 Teprimepledstmicturgdesign Oblique section failure reasons: Since under the action of bending moment and shear together,M and V, respectively,in the produce section of the normal stress and shear stress,causing the principal tensile stress and compressive stress,when the principal tensile stress tp>ft,that is generated oblique crack,the failure surface And the beam axis bias. said inclined section failure
⚫ Since under the action of bending moment and shear together, M and V, respectively, in the produce section of the normal stress and shear stress, causing the principal tensile stress and compressive stress, when the principal tensile stress tp> ft, that is generated oblique crack, the failure surface And the beam axis bias. ––– said inclined section failure. Oblique section failure reasons:
JPKIc 箱构试原果 Shear curve section of the beam after diagonal cracks occur,the stress state cross-section a qualitative change,or that the stress redistribution occurs.At this time,can not use the formula to calculate the mechanics of materials beam section on the normal stress and shear stress,because when the full beam is no longer a homogeneous elastic beam. D Beams without web reinforcement after diagonal crack appeared inclined crack map
图4-2 斜裂缝出现后的应力状态 b) C QA D a) C D B Ts a MB B Qd c B' Sa MA z Qc A' A Dc B' A' A Beams without web reinforcement after diagonal crack appeared inclined crack map Shear curve section of the beam after diagonal cracks occur, the stress state cross-section a qualitative change, or that the stress redistribution occurs. At this time, can not use the formula to calculate the mechanics of materials beam section on the normal stress and shear stress, because when the full beam is no longer a homogeneous elastic beam
JPKIC 结构设计原理 Teprnimeipletstrmicturgdesign Stress redistribution phenomenon: B AVc D De Inclined cracks appear before the V by the total cross section of shear resistance.Diagonal crack appears,by B some section of the shear V AA/ resistance,shear pressure area is reduced .'AA/shear stress and compressive stress increases Inclined cracks appear before the bar of any cross-section of longitudinal section of tensile stress at the moment by the Me decision.Diagonal crack appears,the tensile stress in longitudinal reinforcement cross-section inclined cracks the top section from the bending moment at the Ma decision. .longitudinal reinforcement tensile stress increased significantly
Stress redistribution phenomenon: ⚫Inclined cracks appear before the VA by the total cross section of shear resistance. Diagonal crack appears, by some section of the shear VA AA / resistance, shear pressure area is reduced ∴ AA / shear stress and compressive stress increases ⚫Inclined cracks appear before the bar of any cross-section of longitudinal section of tensile stress at the moment by the MB decision. Diagonal crack appears, the tensile stress in longitudinal reinforcement cross-section inclined cracks the top section from the bending moment at the MA decision. ∴ longitudinal reinforcement tensile stress increased significantly 图4-2 斜裂缝出现后的应力状态 b) C VA D C B Ts a MB B vd c B' Sa MA z Vc A' A Dc A