有一钢筋混凝土梁,见图1,配料钢筋形状见图2,弯起钢筋的弓背和弯起钢筋下料长度用什么方法计算才能准确呢?已知条件:l_n 为混凝土梁净长度(毫米),弯筋终点与梁支座截面的距离为50毫米,弯筋直径为 d(毫米),混凝土梁截面尺寸为 b×h(毫米),混 There is a reinforced concrete beam, see Figure 1. The shape of the batching reinforcement is shown in Fig. 2. What is the accuracy of calculating the length of the bending and the bending of the steel reinforcement? Known condition: l_n is the net length of the concrete beam (mm) The distance between the end of the bent rib and the section of the beam support is 50 mm, the diameter of the bent bar is d (mm), and the section size of the concrete beam is b×h (millimeter).