加筋混凝土梁延性系数计算方法

由于纤维增强复合材料(FRP)筋不存在屈服状态,传统的延性系数计算方法不适用于FRP筋混凝土梁和混合配筋(钢筋+FRP筋)混凝土梁。为了提出一个相对完善的、统一的加筋混凝土梁截面延性计算方法,在对既有各类加筋混凝土梁延性指标计算方法进行分析的基础上,从抗震对结构延性的要求出发,依据延性系数的定义与动力要求统一的原则,推导得出了加筋混凝土结构延性系数-地震力降低系数(μ-C)关系式。依据等位移下的μ-C关系式,提出了加筋混凝土梁延性系数的计算方法。通过对比延性系数计算值与既有试验值,证明了该方法的有效性。对混凝土及钢筋强度、混凝土极限压应变、截面有效配筋率和FRP筋配筋刚度比等影响加筋混凝土梁延性的因素进行了参数化分析。结果表明:加筋混凝土梁的延性随着混凝土强度和极限压应变的增加而提高,随着钢筋强度、有效配筋率和FRP筋配筋刚度比的提高而降低。

Calculation Method for Ductility Coefficient of Reinforced Concrete Beams

Due to the fiber reinforced polymer(FRP)bars no yield state, the traditional ductility coefficient calculation method is not suitable for FRP reinforced concrete beams and hybrid reinforced(steel bars + FRP bars)concrete beams. In order to put forward a relatively perfect and unified method for calculating the ductility of reinforced concrete beams, the existing calculation methods of ductility coefficients of reinforced concrete beams were analyzed. According to the definition of ductility coefficient and the dynamic requirement, the formula of ductility coefficient-seismic force reduction coefficient(μ-C)relation of reinforced concrete structure was derived from the requirement of seismic resistance to ductility of structure. A method for calculating ductility coefficient of reinforced concrete beam was presented according to the formula of μ-C relation under equal displacement assumption. The effectiveness of the method was proved by comparing the calculated values with the experimental results. The factors affecting the ductility of reinforced concrete beams, such as the strength of concrete and reinforcement, the ultimate compressive strain of concrete, the effective reinforcement ratio and the ratio of reinforcement stiffness of FRP bars, were analyzed. The results show that the improvement of concrete strength and ultimate compressive strain is beneficial to the ductility of reinforced concrete beams, while the increase of reinforcement strength, effective reinforcement ratio and FRP reinforcement stiffness ratio has adverse effects on the ductility of reinforced concrete beams.