三腹杆体外预应力索内力分析及模拟验证

Analysis and simalation verification of internal forces of external prestressing cables with three belly poles

本文提出的三腹杆体外预应力加固简支梁是通过在体外索跨中及两侧1/4处腹杆的伸长来实现预应力的施加,腹杆使体外索内切于抛物线。基于体外索与腹杆的基本假定,介绍了新型转向装置和预应力施加方法。本文推导了体外索的方程和各段索内力表达式,并推出了体外索跨中挠度增量与两侧1/4处挠度增量的关系式。通过循环迭代的方法,得到了索长增量与跨中挠度增量的关系、索长增量与腹杆荷载的数学表达式,并通过有限元软件ABAQUS进行模拟验证。结果表明:靠两端索的内力大于内侧索内力;两侧1/4处挠度增量为跨中挠度增量的3/4;利用推导出索长与腹杆荷载增量的关系与模拟结果对比,结果发现两者基本呈线性关系,并且当荷载步距较小时,理论值与模拟值基本吻合。荷载步距越小,计算精度越高。分析结果为实际工程加固简支梁提供参考。

In this paper,the external prestressing reinforcement simply supported beam of three web bars realizes the prestressing addition through the elongation of the web bar at the middle of the external cable span and at 1/4 on both sides of the cable,the web leads the external cable to inscribe a parabola.Based on the basic assumption of external cable and web link,new steering gear and prestressing method are introduced.The equation of external cable and the expression of internal force of each segment are derived,and the relation between the increment of deflection in the middle span of external cable and the increment of deflection at 1/4 on both sides is derived.The relationship between lock length increment and span mid-deflection increment,and the mathematical expression of lock length increment and web load are obtained by means of cyclic iteration.And through the finite element software ABAQUS,the simulation verification is carried out.The results show that the internal force of the external cable at both ends of the cable is greater than that of the external cable on the inner side;the 1/4 deflection increment on both sides is 3/4 of the mid span deflection increment;the relationship between the cable length and the web load increment is compared with the simulation results;the results show that the relationship between the cable length and the web load increment is basically linear,and when the load step is small,the theoretical value is basically consistent with the simulation value.The smaller the load step distance is,the higher the calculation precision is.The analysis results can be used as a reference for strengthening simple supported beams in practical engineering.