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用預应力元宝筋加固鋼筋混凝土屋面梁,具有施工简单,受力明确,取材容易,用鋼量较少等优点,同时,它直接以力的形式提高和改变原构件的刚度,裂縫和承载力,比增加材料的方法补强結构物更为优越,因此,近年在国内已被广泛采用。但对混凝土标号较低,配筋率較高的T形或I形截面鋼筋混凝土薄腹屋面梁,采用这种加固方法,經常会使构件截面形成超配筋,因此,预应力筋不能充分发揮其計算强度,对提高构件抗弯承載力的效果不大。此外,在某些构造細节上如处理不当,也会影响加固效果。以下談談笔者在工作中的一些体会和看法。一、强度計算一般可按图1采取下列二种計算方法: 1.取原构件为自由体,将預应力筋的垂直分力P′(P′>P)和水平分力N(N=σ′_2A,σ′_2>σ_2,σ′_2的取值問題見本文三中所述)視为外力,作用于构件上,并与构件的外荷截組合后,按偏心受压驗算构件强度。
Reinforced concrete roof beam with prestressed ingot reinforcement has the advantages of simple construction, clear stress, easy drawing, less steel consumption and the like, and at the same time, it directly increases and changes the rigidity, crack and bearing capacity of the original structure in the form of force , Which is more superior than the method of reinforcing materials to reinforce the structure. Therefore, it has been widely adopted in China in recent years. However, for reinforced concrete thin-walled roof beams with low-grade concrete and high reinforcement ratio, the reinforcement method often results in the over-reinforcement of the cross-section of the structure, so that the prestressing tendons can not be sufficiently developed Exert their computational strength, to improve the flexural strength of members is not effective. In addition, improper handling of certain structural details can also affect the reinforcement effect. The following talk about some of my experience in the work and views. I. Calculation of Strength Generally, the following two calculation methods can be adopted according to Figure 1. 1. Taking the original component as free body, the vertical component P ’(P’> P) and the horizontal component N (N = σ The value of _2A, σ’_2> σ_2, σ’_2 can be seen as the external force, acting on the component and combined with the external load of the component. The strength of the component is calculated according to the eccentric compression.