嵌套连接冷弯斜卷边Z形连续檩条的受弯性能试验研究

本文对嵌套连接的冷弯斜卷边Z形连续檩条的受弯性能进行了试验研究。试验分两部分,一是搭接段极限承载力试验,以确定常用范围内搭接负弯矩段的极限承载力;二是两跨连续檩条试验,目的是确定搭接段截面的抗弯刚度。试验分上下翼缘均有自攻钉和仅上翼缘有自攻钉两种情况。对于承载力试验,搭接长度的范围为截面高度的3～5.625倍。通过对5种不同搭接长度和方式共30个试件的破坏性试验发现,破坏都是由受压下翼缘的屈曲引起,且破坏主要发生在搭接开始处。当中间支座处弯矩是搭接开始处弯矩的两倍时破坏出现在中间支座处,此时单个截面的承载力仍然与破坏发生在搭接开始处的情况接近。在试验所用试件的搭接长度范围内,搭接长度对承载能力的影响不大;但搭接段檩条下翼缘是否有自攻钉对搭接段承载能力有约5%的影响。对两跨连续梁,分搭接长度为跨度的10%和20%的两种情况,上下翼缘均有自攻螺钉和仅上翼缘有自攻螺钉两种构造,共进行了11个试验,试验结果表明,搭接长度较长时搭接

Experimental investigation on nested continuous Z-purlins under gravity loading

This paper reports an experimental investigation on the bending behavior of cold-formed continuous Z-purlins with lapped connections. The first part of the tests was performed on the load-carrying capacity of the lapped segments. The specimens are simply supported beams with cantilevers of the same span length, and concentrated loads applied at the free ends of the cantilevers. The lapped lengths are changed from 3 to 5.625 times the depth of the Z-section. A part of the specimens have self-tapping screws in both flanges, while the others have them only in the top flanges. A total of 30 specimens were tested for the ultimate bending moment of lapped segments. It was found that most of the specimen failed due to buckling of the compressed flange. The failure occurs at the start section of lap. When the bending moment at the support is double that at the start of the lap, then failure appears at the support. The lapped lengths of the connections do not affect the load-carrying capacities of tested specimens, but the connections with self-tapping screws in both flanges can carry 5% more loads than those with self-tapping screw only in the top flanges. The second part of the test was done on the bending stiffness of the lapped segment and two-span continuous beams were tested. The lapped lengths are 10% and 20% of a single span length respectively, again part of specimens have screws in both flanges and the others have screws only in the top flange. 11 specimens were tested in total. It was shown that the lapped length influences the stiffness of the lapped segment. Based on the test, the bending stiffness for moment analysis and the deflection calculation are suggested.