重庆现浇楼板的三筋构造-Three bar structure of cast
编辑：admin 日期：2020-03-16 20:20 / 人气：
有些人由于对钢筋和混凝土两种材料共同工作的性能缺乏较深入的了解，往往产生一种错觉，误认为在混凝土构件内，放置的钢筋越多越“安全”。其实这种看法是不对的，首先，比设计要求多放置了钢筋，给国家造成了材料的浪费；其次，从结构的受力情况分析，过量放置钢筋并不安全，反而造成隐患，具有一定危险性。
Cast in place is not new to many construction industries. The cast-in-place has its unique advantages, so many people like it, and the cast-in-place method is more and more used by many people. There is a kind of cast-in-place concrete. Why is it unsafe to have more reinforcement in the cast-in-place concrete? Next, let's share it with you.
Because some people lack a deeper understanding of the performance of the two materials working together, they often have an illusion that the more reinforcement placed in the concrete component, the more "safe". In fact, this view is wrong. First of all, more steel bars are placed than the design requirements, causing material waste to the country. Second, from the analysis of the stress situation of the structure, excessive steel bars are not safe, but cause hidden dangers, which has a certain degree of danger.
大家知道，构件在破坏荷载作用下，将产生破坏。对于钢筋混凝土的破坏有三种情况：
１）适筋破坏——这种破坏的特点是：受拉区钢筋达到流限（即屈服点强度），此时即使荷载不再增加，钢筋应变增加也很快，但应力不再增加，这是钢材的性质所决定的。混凝土裂缝沿混凝土断面的垂直高度开展迅速，挠度相应急骤增大。同时受压区混凝土相继达到弯曲抗压强度，出现水平裂缝而压碎，构件便完全破坏。这种破坏是通过挠度变形、裂缝开展等现象表现出来的，它带有“预示性”，人们可以采取应急措施，所以它是安全的。混凝土的截面设计，就是以这种破坏状态作为计算依据的。
As we all know, under the action of failure load, the component will produce failure. There are three types of damage to reinforced concrete:
1) The characteristic of this kind of failure is: the steel bar in the tension area reaches the flow limit (i.e. yield point strength), at this time, even if the load is no longer increased, the steel bar strain increases rapidly, but the stress is no longer increased, which is determined by the nature of the steel. The concrete cracks develop rapidly along the vertical height of the concrete section, and the deflection increases rapidly. At the same time, the concrete in the compression area reaches the bending compressive strength one after another, and the horizontal cracks appear and crush, and the components are completely destroyed. This kind of damage is shown by deflection deformation, crack development and other phenomena. It has "predictability". People can take emergency measures, so it is safe. The section design of concrete is based on the failure state.
2) Over reinforcement failure - if over reinforcement is placed in a member (compared with the amount of steel used for suitable reinforcement), the failure will change qualitatively. Due to the excessive reinforcement, the reinforcement still has great potential under the action of failure load, but the concrete in the compression zone is gradually approaching the bending compression limit. As the concrete belongs to brittle material, once it is damaged, the time is short, rapid and sudden, so the super reinforcement failure is also called "brittle failure". This kind of damage starts from concrete, which is different from that of the suitable reinforcement. When the component is damaged, the deformation of the reinforcement is not significant, and the component does not indicate excessive deflection and cracks. There is no prediction. People have no time to take emergency measures, and the component is suddenly damaged, so it is dangerous and unsafe.
３）欠筋破坏——当钢筋放置过少（与适筋破坏用钢量相比），也将产生类似超筋破坏的“脆性破坏”，但首先引起脆性破坏的不是混凝土，而是钢筋。这是当钢筋完成流限变形后，进入强化阶段产生脆性断裂而引起的。
3) Under reinforcement failure - when the reinforcement is placed too little (compared with the amount of steel used for suitable reinforcement failure), the "brittle failure" similar to the over reinforcement failure will also occur, but the first cause of brittle failure is not concrete, but reinforcement. This is caused by brittle fracture when the reinforcement enters the strengthening stage after the completion of flow limit deformation.
总之，在钢筋混凝土结构中的受力钢筋，是经截面计算而配置的。在施工中应严格按要求的规格、数量放置，不可任意减少或增加。钢筋过多，不能发挥钢筋的受力性能；而钢筋过少，则不能充分发挥混凝土的抗压性能，这些不仅会造成材料的浪费，而且还带来力学性能的变化，影响结构安全。只有放置适量钢筋，才是唯一正确。
In a word, the load-bearing steel bars in reinforced concrete structure are configured by section calculation. During the construction, it shall be placed in strict accordance with the required specifications and quantity, and can not be reduced or increased arbitrarily. Too much reinforcement can not give full play to the mechanical properties of reinforcement, and too little reinforcement can not give full play to the compressive properties of concrete, which will not only cause waste of materials, but also bring about changes in mechanical properties, affecting structural safety. It is the only right way to place the right amount of steel.
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