精细化工厂房钢筋混凝土框架梁上部裂缝控制

Cracking Control on the Top of Reinforced Concrete Frame Beams in Fine Chemical Production Buildings

精细化工生产厂房所处的环境类别通常为二类或三类，传统设计方法采用梁上部、下部相同的最大裂缝宽度限值0．2mm，会使梁上部实配钢筋比强度计算值提高60％以上，这样造成梁上部配筋很大，甚至超筋，也不符合强柱弱梁的建筑抗震概念设计；同时，精细化工生产厂房原材料、中间产品及最终产品通常有腐蚀性，按照防腐蚀规范的要求，建筑习惯做法有防腐面层和50mm配筋的细石混凝土面层。因此，建议精细化工生产厂房采用优化设计方法：梁上部最大裂缝宽度限值按环境类别一类0．3mm控制；梁下部按环境类别二类或三类最大裂缝宽度限值0．2mm控制。按照这种优化的设计方法，梁上部、下部实配钢筋比强度计算值通常均提高了10％-20％，与优化前提高60％相比，这种提高幅度还是合情合理的。

Fine chemical production buildings generally belong to environment classification B or C. Traditional design,in which the maximum crack width on the top or at the bottom of a beam is required not bigger than 0.2 mm, may increase reinforcement of 60% than strength calculation result and cause the ratio of reinforcement on the top of beam become very big, furthermore overreinforced, conflicting with seismic concept design of buildings. At the same time, crude materials, semi-finished products, and termination products in fine chemical production building are normally corrosive, to meet the requirements in the code for anticorrosion design of industrial constructions, floor in architecture discipline is designed with a anticorrosive coating and a 50 mm reinforcing-bars fine aggregate concrete layer. So optimum design is recommended： maximum crack width on the top of a beam is controlled not more than 0.3 mm according to environment classification A ; maximum crack width at the bottom of a beam is controlled not more than 0.2 mm according to environment classification B or C. As a result of optimum design, actual reinforcement may increase 10% 20%. Comparing to the former 60%, the results through optimum design is fair and reasonable.