节段预制纤维增强混凝土压杆键齿受力性能试验研究

节段预制桥梁靠近支座处箱梁腹板由于受力复杂，而在键齿处容易发生开裂。为此，以接缝处键齿配筋方式(素齿、构造筋以及体内穿筋)、键齿齿目(单键齿、双键齿)和干接缝角度(30°、45°以及60°)作为试验的设计参数，对8对使用2%配纤率的强度为100.1 MPa纤维增强混凝土干接缝匹配的压杆试件进行试验研究，记录试件的开裂荷载、极限荷载、残余荷载、键齿处的滑移，并观察试件的裂缝发展过程以及破坏模式，研究了试件竖向位移-荷载、键齿处滑移-荷载之间的关系，并采用ABAQUS有限元中的混凝土CDP模型对试件加载进行全过程分析，得到开裂时试件的应力分布以及破坏时试件的损伤分布。研究结果表明：体内穿筋能够提高压杆试件的开裂荷载以及极限荷载，改变破坏模式，增加试件的整体性；键齿内增强构造筋对于干接缝键齿的力学性能以及改变试件破坏模式的影响较小；双键齿齿目试件的开裂荷载、极限荷载以及试件的整体刚度与单键齿齿目压杆试件相比，均有较大提升；3种不同接缝角度试件中，45°试件的开裂荷载、极限荷载以及整体刚度均是最小；对于单键齿试件而言，开裂均是发生在上键齿顶角处，并最终沿着初始裂缝发生劈裂破坏，而对于双键齿试件而言，接缝角度不同，试件破坏方式也不同。DK-30阴齿试件与阳齿试件均发生劈裂破坏，DK-45与DK-60两组试件不仅产生了劈裂破坏而且发生了键齿的斜剪破坏；有限元模型计算结果与试验结果吻合度较高。

Experimental Study on Mechanical Properties of Keys in Segmental Prefabricated Fiber-reinforced Concrete Struts

The web of a box girder near the support of a segmental prefabricated bridge can easily crack at the key because of complex stresses. Eight pairs of compression bar specimens with a fiber ratio of 2% and strength of 100.1 MPa fiber-reinforced concrete dry joint matching were subjected to tests. The variables were the key reinforcement at the joints (plain, structural reinforcement, and internal threading keys), number of keys (single and double keys), and dry joint angle (30°, 45°, and 60°). The values of the cracking load, ultimate load, residual load, and sliding at the key were recorded. In addition, crack development and failure modes were observed. The relationship between the vertical displacement load and sliding load at the key was established, and the concrete damaged plasticity model of concrete in ABAQUS was used to analyze the entire loading process. The stress distribution of each specimen on cracking and the damage distribution of the specimen on breaking were obtained. The results show that the internal reinforcement in the specimen increases the cracking load and ultimate load, changes the failure mode, and increases the integrity of the compression bar. The internal reinforcement of the key minimally influences the mechanical properties of the key with a dry joint and the failure mode of the specimen. The cracking load, ultimate load, and overall rigidity of the double-key specimen significantly improve compared to the single-key specimen. Among the specimens with different joint angles, the cracking load, ultimate load, and overall stiffness of the 45° specimens are the minimum. For the single-key specimen, the first crack typically occurs at the top corner of the upper key in the female specimen and finally splits along the initial crack. For the double-key specimens, the failure modes for different joint angles are different. Finally, the female and male specimens of DK-30 split, and DK-45 and DK-60 undergo not only split failure but also diagonal key shear failure.