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该文分析和评述了确定体外预应力筋极限应力的三类计算方法,即:粘结折减系数法、基于截面配筋指标的回归方法和基于变形的方法。分析表明,基于变形的方法能够反映体外预应力混凝土梁所具有的构件截面强度与构件整体变形相耦合这一显著特征。在基于变形方法中的两个常用的等效塑性区长度模型中,与构件跨高比和外荷载作用形式相关联的模型过分夸大了荷载作用形式对体外预应力筋极限应力的影响。针对桥梁结构所承受的移动交通荷载,承载能力极限状态下,实际设计中很难判断和选择与荷载作用形式相关联的系数。而与构件失效时关键截面中性轴高度相关联的等效塑性区长度模型中的关键参数在不同试验中则具有较好的稳定性和一致性。该文的研究结果有助于建立简单而正确的体外预应力筋极限预应力计算方法。
This paper analyzes and reviews three kinds of calculation methods to determine the ultimate stress of prestressed tendons in vitro, namely the bond reduction coefficient method, the regression method based on the cross-section reinforcement index and the deformation-based method. The analysis shows that the method based on deformation can reflect the significant feature that the strength of the cross-section of the component of external prestressed concrete beams coupled with the overall deformation of the component. In the two commonly used equivalent plastic zone length models based on the deformation method, the model associated with the component span ratio and the external load acting form excessively exaggerates the effect of the load acting form on the ultimate stress of the external prestress tendons. In view of the mobile traffic load and bearing capacity of the bridge structure, it is very difficult to judge and select the coefficients associated with the form of load in the actual design. However, the key parameters in the equivalent plastic zone length model associated with the neutral axis height of the critical cross-section at failure of the component have better stability and consistency in different experiments. The results of this paper contribute to the establishment of a simple and correct method of calculating the ultimate stress of prestressed tendons in vitro.