钢-STC轻型组合桥面螺栓连接接头区域设计

Design of Bolted Joint Region for Steel-STC Lightweight Composite Bridge Deck

为解决正交异性钢桥面板疲劳开裂和铺装层易损的难题,提出钢-STC轻型组合桥面结构方案。此结构方案应用于含有钢箱梁栓接的旧桥桥面维修时,螺栓连接区域由于存在拼接钢板,导致局部接头区域STC层厚度骤减,刚度下降,受力变形趋于不利,易出现早期开裂现象,需进行局部优化设计。针对这一问题,就接头区域局部提出2项强化构造措施(①局部加密剪力钉、②部分纵向钢筋与拼接钢板局部焊接),并进行足尺条带模型试验。以礐石大桥螺栓连接区域为例,对拟同时采取上述2项措施的情况进行验算。研究结果表明:2项措施均在不同程度上阻滞了STC层顶面接头区域内微裂纹宽度的发展,延缓了开裂,尤其当采取第2项措施或同时采取2项措施时,STC层顶面接头区域晚于一般区域开裂,即接头区域不再是设计计算中需要控制的不利区域;STC层顶面可能出现的最大拉应力为11.5 MPa,小于试验开裂荷载对应的名义开裂应力17.7 MPa,满足设计要求,即钢-STC轻型组合桥面结构方案应用于礐石大桥桥面维修可行。

A steel-super toughness concrete(STC) lightweight composite deck structure is proposed to solve the problem of the fatigue cracking in orthotropic steel deck, and the vulnerability of pavement layer. When the lightweight composite bridge deck was used for the maintenance of the old bridge with bolted steel box girder, the thickness of the STC layer in the joint region suddenly drops, the local stiffness decreases and the deformation tends to be unfavorable all due to the existence of the spliced steel plate. Thus, with early cracking the local optimization design becomes imminent. Accordingly, this paper puts forward two distinct measures to strengthen the joint region: ①increase the arrangement density of shear studs in part;②locally weld the longitudinal reinforcement and sliced steel plate, and the full-scale model tests with two measures were carried out. Our studies showed that the two measures have both hindered the development of microcracks in width in the joint region of the STC layer to different extents, and have both delayed the cracking. When either the second measure was taken or both taken simultaneously, the joint region cracked later than the regular region, which means the joint region was no longer, an unfavorable region needing to be controlled during the design calculation. As an example, we tested these two measures on the joint region of Queshi Bridge, and the maximum tensile stress of STC layer was found to be 11.5 MPa, lower than the nominal cracking stress of 17.7 MPa. The result indicates that the STC lightweight composite bridge deck meets the design requirements, and is applicable for the maintenance of Queshi Bridge.