External prestressing with non-binding stranded steel wire is a kind of active strengthening method for existing buildings.Code for Design of Strengthening Concrete Structures(GB 50367-2013) assumes that the stress increment of stranded steel wire is equal to the value of prestressing loss,simplifies the calculation process in external prestressing with non-binding stranded steel wire.To a certain extent,it's conducive to promote it in practical engineering.But this assumption is not clear,and it is easy to cause errors in understanding and application.What's more,it may be less secure.With a numerical example to study the reinforced concrete beams strengthened by external prestressing with non-binding stranded steel wire,the result shows that it does not meet the serviceability limit states under the assumed condition.%无粘结钢绞线体外预应力加固是一种用于既有建筑结构的主动加固方式,《混凝土结构加固设计规范》(GB 50367-2013)假定钢绞线的应力增量值与预应力损失值相等,简化了无粘结钢绞线体外预应力加固的计算,在一定程度上有利于在工程实际中的推广应用.但该假定概念不清晰,容易引起理解和应用上的错误,且计算结果可能偏于不安全.本文以1个算例探讨了无粘结钢绞线体外预应力加固钢筋混凝土梁的设计计算方法,结果显示,在该假定条件下,计算结果已经不满足正常使用极限状态限值.
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