Development of External Prestressed Concrete with Large Eccentricities and Establishment of Its Design Method

体外预应力混凝土近年来在桥梁结构中得到广泛应用。然而，从过去的研究中已经知道，体外预应力梁的极限抗弯强度相对小于类似的内粘结梁。采用大偏心距布置预应力筋是提高体外预应力梁抗弯强度的一种可能方法。为了验证这种桥梁的抗弯性能，采用模型试验进行了试验研究。本文通过对两跨连续梁不同布筋方式的试验研究，获得了这种结构的基本力学性能。试验结果表明：1）预应力筋布置方式的线性变换对梁的抗弯性能没有影响;约束钢筋的存在并不影响这些梁的极限强度。2）预应力筋应力增加成正比于跨中变形，直到筋屈服。加载布置的类型影响外部筋的增加率。因此，非对称加载梁的极限抗弯强度降低了约20%。

Externally prestressed concrete has recently become popular in bridge structures. However, it has been known from past studies that the ultimate flexural strength of externally prestressed beams is comparatively lesser than that of similar internal bonded beams. One of the possible methods to enhance the flexural strength of externally prestressed beams is to place the tendons with large eccentricities. To verify the flexural behavior of such bridges, an experimental investigation was conducted using model test. In this study, a series of test was carried out on two span continuous beams consisting of different tendon layouts to obtain the fundamental mechanical behavior of such structures. The following conclusions are made from the test.1) The flexural behavior of the beams was not affected by the linear transformation of the tendon layout. The presence of confinement reinforcement did not influence the ultimate strength of these beams.2) The tendon stress increased proportionally to the midspan deformation until yielding of tendon. The type of loading arrangement influenced the rate of increase in external tendons. As such, the ultimate flexural strength of unsymmetrically loaded beams were reduced by about 20%.