Chapter 6: Continuous composite Beams 连续组合梁 By Prof.Chen Shiming Lecture Notes for Presentation 2013
By Prof. Chen Shiming Lecture Notes for Presentation 2013 Chapter 6: Continuous composite Beams 连续组合梁
Objective/Scope To describe the behaviour of continuous composite beams(连续组合梁受力和承载 特性)方 ·Rigid-plastic analysis(塑性极限方法) To determine internal moments and forces, and to evaluate moment redistribution. ·连续组合梁的内力分析，重分布
Objective/Scope • To describe the behaviour of continuous composite beams (连续组合梁受力和承载 特性); • Rigid-plastic analysis(塑性极限方法) • To determine internal moments and forces, and to evaluate moment redistribution. • 连续组合梁的内力分析,重分布
6.1 Introduction Advantages of continuous beams:(特征、优点) .1)greater load capacity due to redistribution of moments;ii)greater stiffness Disadvantages associated with continuous beams: i)increased complexity in design ii)susceptibility to buckling in the negative moment region(局部屈曲，侧扭失稳 ) Design/detailed calculations or global analysis': to determine internal moments and forces in critical regions for the various loading cases and limit states 极限状态的内力分析
6.1 Introduction Advantages of continuous beams : (特征、优点) • i) greater load capacity due to redistribution of moments; ii) greater stiffness • Disadvantages associated with continuous beams: i) increased complexity in design ii) susceptibility to buckling in the negative moment region （局部屈曲，侧扭失稳） • Design/ detailed calculations or ‘global analysis’ : to determine internal moments and forces in critical regions for the various loading cases and limit states 极限状态的内力分析
The salient(turn)point in regard to serviceability and strength needs to take into account that composite beams in hogging bending behave completely differently than beams subjected to sagging bending. In hogging bending the concrete slab is subjected to tension,and this will significantly affect both the stiffness and strength of the cross sections in hogging moment regions
• The salient (turn) point in regard to serviceability and strength needs to take into account that composite beams in hogging bending behave completely differently than beams subjected to sagging bending. • In hogging bending the concrete slab is subjected to tension, and this will significantly affect both the stiffness and strength of the cross sections in hogging moment regions
The concrete in the mid Cracked concrete Reinforcement span region is in compression and the steel in tension Hogging Over the internal support this distribution reverses. The concrete cannot carry Sagging Bending moment diagram significant tensile strains and therefore cracks,the embedded reinforcement as effective in resisting Section X-X Section Y-Y moment.(混凝土开裂，钢 梁易屈曲、失稳) Strain Stress Strain stress
The concrete in the mid span region is in compression and the steel in tension. Over the internal support this distribution reverses. The concrete cannot carry significant tensile strains and therefore cracks, the embedded reinforcement as effective in resisting moment.（混凝土开裂，钢 梁易屈曲、失稳）