高强度螺栓摩擦型连接火灾后抗剪试验研究

建筑火灾发生频繁且对钢结构危害严重,但总体而言绝大多数火灾并未造成钢结构的根本性破坏,尽快鉴定其火灾后安全性并进行加固修复,对于减小灾后间接经济损失意义重大。高强度螺栓摩擦型连接是钢结构最常用的连接方式之一,其火灾后受力性能对整个结构灾后承载的安全至关重要。但目前国内外对高强度螺栓连接高温过火冷却后的受力性能研究极少。本文对高强度螺栓摩擦型连接进行了火灾后抗剪试验研究,得到了连接的抗滑移承载力、极限承载力以及荷载—变形曲线,研究了过火温度、冷却方式对连接受力性能的影响。为模拟火灾中的可能情况,试验考虑了自然冷却、泼水冷却两种冷却方式。试验表明,当高强度螺栓连接的过火温度不超过400°C时,连接的抗滑移承载力、极限承载力下降小,可判定连接仍能承受外部设计荷载,不需要对连接进行加固或替换螺栓;当过火温度超过400°C时,连接的抗滑移承载力、极限承载力开始显著下降,需连接更进一步的检测并进行仔细的结构分析,以确定连接能否继续承受外部设计荷载,以及是否需要采取必要的加固与修复措施。

Experimental Study on Shear Behavior of Bolted Friction-type High-strength Connections after Fire

Fire is the greatest and most universal disaster for buildings,especially for steel structural buildings.In the past 100 years,there were many cases that steel structures collapsed in fire.However,steel structures in most cases were not fatally destroyed.These damaged steel structures may be reused after structural inspection,safety appraisal,reinforcement and strengthening.High-strength bolted connections are widely used in steel structures.As a fundamental part of the whole structure,the behavior of high-strength bolted connection is very important for maintaining the integrity and safety of steel structures.Usually,structural behavior of high-strength bolted connection decreases after fire action due to strength loss and initial preload loss of high-strength bolt. Up to now there are only a fewer studies focusing on the mechanical properties of high-strength bolted connections after fire.To obtain the mechanical properties of high-strength bolted connections after fire including slip load capacity, ultimate capacity and load-deformation curve,a series of experiments were carried out in this study.In order to simulate the behaviors of high-strength bolted connections in fire accidents,both natural cooling and water cooling situations were employed in the tests.The results show that when high-strength bolted connections are exposed to a temperature lower than 400°C,the loss of slip load capacity and ultimate capacity after cooling is considerably small,which means the connections can maintain the external design load after fire.When high-strength bolted connections are exposed to a temperature higher than 400°C,slip load capacity and ultimate capacity decease violently.Hence,a deeper inspection of the connections is necessary to check whether the connections are safe.