可恢复组合梁中高强螺栓连接件抗剪性能试验

Experimental Study on Shear Performance of High-strength Bolt Connectors in Recoverable Composite Beams

为探究高强螺栓连接组合梁的功能可恢复性,通过更换失效螺栓对栓接组合推出试件进行了多次损伤-修复,并对滑移前钢-混凝土界面摩擦性能和滑移后螺栓杆抗剪性能展开了详细研究。以滑移失效和承载力破坏失效为临界点,共对24个推出试件开展了力学性能恢复测试,考虑了重装配次数、螺栓预拉力、螺栓强度、螺栓直径和螺栓孔间隙等因素的影响。最后,通过拟合得到了与螺栓预拉力相关的钢-混凝土界面摩擦因数计算公式和螺栓抗剪承载力计算公式,并提出了单个螺栓的荷载-滑移曲线实用公式,可为考虑滑移的组合梁设计提供基础。试验及分析结果表明:若混凝土板没有开裂,则更换螺栓再装配后,磨损的钢-混凝土界面摩擦性能有一定提高,螺栓抗剪承载力不会降低,可以达到原设计要求,证明螺栓连接的组合结构具有较好的可恢复性能;钢-混凝土界面摩擦因数不是定值,界面处理相同情况下,摩擦因数随螺栓预拉力的增加而非线性增大,其极值为0.53~0.56;增大螺栓直径和强度等级可以显著提高抗剪承载力和承压抗剪刚度,但混凝土板破损严重,不利于重复利用;螺栓直径小于20 mm时,螺栓与混凝土强度适配良好,可以充分发挥钢材强度;随螺栓预拉力的增加,混凝土局部压损加重,螺栓抗剪刚度减小,60~100 kN为较合适的预拉力范围。

In order to explore the functional recoverability of high-strength bolted composite beams,damage-repair processes more than once were carried out on the bolted composite push-out specimens by replacing the failed bolts in this paper.Also,the frictional properties of steel-concrete interface before slip and shear performance of bolt shank after slip were studied in detail.With slipping failure and bearing capacity failure as critical points,mechanical property recovery tests were conducted on a total of 24 push-out specimens,taking into account the effects of reassembly times,bolt pretension,bolt strength,bolt diameter and bolt hole clearance.Finally,the design equation of friction coefficient of steel-concrete interface considering bolt pretension and the formula for calculating shear capacity were established through fitting.Simultaneously,the practical formula of load-slip curve for single bolt is presented.The proposed formulas can provide a basis for the design of composite beams considering slip.The experimental and analytical results indicate that if the concrete slab does not crack,after replacing broken bolts and reassembling the specimen,the frictional property of worn steel-concrete interface can be improved to some extent and the shear capacity of bolts cannot decrease.This can meet the original design requirements and proves that bolted composite structures have good recoverable behavior.The friction coefficient of steel-concrete interface is not constant.Under the same condition of interface treatment,the friction coefficient increases nonlinearly with the increase of bolt pretension,and its extreme value is about 0.53 to 0.56.Increasing bolt diameter and strength grade significantly improves the shear capacity and pressure-bearing shear stiffness,but the concrete slabs are seriously damaged,which is not conducive to reuse.When the diameter of the bolt is less than 20 mm,the strength of the bolt and concrete is well matched,and the strength of steel can be fully utilized.With the increase of bolt pretension,the local compression damage of concrete becomes worse,and the shear stiffness of bolts decreases.The appropriate range of bolt pretension is 60 kN to 100 kN.