تیرآهن های پس تنیده برش خورده با بخش های Box پیش ساخته
Abstract
1-Introduction
2-Experimental Program
3- Test Results
4- Summary and Conclusions
References
Abstract
It is widely known that the precast segment method facilitates quality control and reduces the costs as well as the construction period. The method, however, has limited applicability since it causes structurally unstable behaviors due to stress concentration in the joints. Against this backdrop, this paper suggested precast segment joints for the improved structural performance and experimentally evaluated the structural performance of the proposed joints in terms of crack pattern, mode of failure, strain, maximum load and displacement ductility. In order to improve constructability as well as structural performance, this paper suggests joints combined with shear key, post tension and steel rod and conducts static load tests. The test results showed that, in terms of maximum load capacity, the resistance of a girder where shear key and post tension are applied to joint details stood at around 86.4% of a monolithic girder’s and demonstrated better ductility behaviors than the monolithic girder.
Introduction
Te precast segmental construction has been widely used in bridge construction due to many advantages such as excellent durability, low life-cycle costs, and quality control since the late 1960s. Te precast concrete segment (PCS) method is widely applied to building structures now as it ensures the high quality and reduces the construction period by minimizing on-site placement work (Wium and Buyukozturk 1984). However, the joints of the spliced girders represent locations of discontinuity through which compression and shear forces are transmitted. Te stifness of the joint can be weaker than those of monolithic girders (Wium and Buyukozturk 1984; Zhou et al. 2005). Nevertheless, there is little information not only on the behaviors and design methods of PCSapplied structures but also the joints between segments that play a signifcant role in these PCS-applied structures (Zhou et al. 2005). Finding it crucial to apply the shear key which ensures high shear resistance and ductility due to transversal interlocking, Zhou et al. (2005) conducted tests with the number of shear keys and the use of epoxy coating on the joint surfaces as variables to analyze efects of individual variables and propose a formula for calculating the shear strength of shear key. Buyukozturk et al. (1990) also considered segment joints as the most important element throughout design and construction, and evaluated the shear strength and deformation of joints through tests on the use of shear key and epoxy and the level of prestressing as variables. Miller et al. (1999) performed tests considering the location of shear key and grouting material as variables that can control the crack of shear key. Tadros et al. (1993) suggested two new methods of connection: one is by using jacking bracket and mechanical splice in pre-tensioned/post-tensioned precast concrete system to connect spliced girder; the other is by applying spacer strut and jacking bracket. It showed that the suggested one has more improved than the existing connection in the aspect of seismic resistance and structural integrity. Saleh et al.