全无缝桥梁用掺橡胶粉LEM-SHCC路桥连接板拉伸性能及其应用

为了解决全无缝桥梁路桥连接板裂缝宽度与板内力过大等问题，将橡胶粉等体积部分替代细砂掺入应变硬化水泥基复合(SHCC)材料可制备低弹性模量的SHCC材料(LEM-SHCC)，用于全无缝桥梁路桥连接板；进行了5种不同体积橡胶粉掺量(0、5%、10%、15%和20%)LEM-SHCC基本材性(密度、抗压强度和弹性模量)及拉伸性能试验，分析了橡胶粉掺量对LEM-SHCC的强度和变形性能的影响，并采用拉、压应变比差评价了橡胶粉掺量对SHCC材料的影响，获得了LEM-SHCC的最优配合比；针对橡胶粉掺量为15%的LEM-SHCC路桥连接板，研究了最不利荷载作用下(温降荷载)其吸纳变形能力、拉伸变形性能及开裂后裂缝分布规律，并与同尺寸SHCC路桥连接板的各项性能进行了比对；进行了LEM-SHCC路桥连接板的敏感参数(橡胶粉掺量、板底摩擦因数和板长等主要影响因素)有限元对比分析。研究结果表明:橡胶粉的掺入降低了SHCC的弹性模量，提升了SHCC的延性，当橡胶粉掺量达15%时，SHCC的弹性模量降低了40%，而延性却提升了近50%，且裂缝宽度有效地控制在60 μm以内；LEM-SHCC路桥连接板吸纳纵向变形达到10 mm时，LEM-SHCC路桥连接板表面微裂缝多(近180条)，裂缝间距小(15~80 mm)，且开裂后裂缝宽度控制在60 μm以内，此时张拉端板应力为2.1 MPa，锚固端锚固力为150.5 kN，卸载后裂缝闭合，无纤维被拉出或拉断；吸纳同样的纵向变形10 mm时，LEM-SHCC板的内力比同尺寸的SHCC板小；LEM-SHCC板的内力受橡胶粉掺量的影响较大，当其掺量为15%时，LEM-SHCC板性能最优，LEM-SHCC板的内力受板底摩擦因数的影响不大，板长的增加能有效地改善LEM-SHCC板的受力性能，推荐LEM-SHCC路桥连接板的设计长度为8.5 m。 

Tensile performance and application of LEM-SHCC road-bridge link slab mixed with rubber powder for fully jointless bridge

In order to solve the problems of excessive crack width and excessive internal force of the road-bridge link slab for a fully jointless bridge, the isopyknic rubber powder was added to a strain-hardening cementitious composite (SHCC) material to partly replace the fine sand, then the SHCC material with a low elastic modulus (LEM-SHCC) was made, which was used for the road-bridge link slab for a fully jointless bridge. The basic material properties (density, compressive strength, and elastic modulus) and tensile property of LEM-SHCC with five different rubber powder contents (0, 5%, 10%, 15%, and 20%) were tested. The effect of rubber powder content on the strength and deformation performance of LEM-SHCC was analyzed. Meantime, the difference of ratio of tensile strain to compressive strain was used to evaluate the effect of rubber powder content on the SHCC material, and an optimal mix proportion of LEM-SHCC was obtained. For a LEM-SHCC road-bridge link slab with a rubber powder content of 15%, its absorptive deformation capacity, tensile deformation performance, and crack distribution law after cracking under the most unfavorable load (temperature drop load) were studied and compared with all the performance of the SHCC road-bridge link slab with the same size. A finite element comparative analysis for the sensitive parameters of the LEM-SHCC road-bridge link slab (the main influencing factors such as the rubber powder content, friction coefficient at the slab bottom, slab length, and so on) was carried out. Research results show that when the rubber powder is added, the elastic modulus of SHCC decreases, and the ductility of SHCC increases. When the rubber powder content reaches 15%, the elastic modulus of SHCC decreases by 40%, while the ductility increases by nearly 50%, with the crack width effectively controlled within 60 μm. When the absorptive longitudinal deformation of the LEM-SHCC road-bridge link slab reaches 10 mm, the micro-cracks on the surface of the LEM-SHCC road-bridge link slab are dense (nearly 180 micro-cracks), and the crack spacing is small (15-80 mm). The crack width after cracking is controlled within 60 μm. At the same time, the slab stress of the tension end is 2.1 MPa, and the anchoring force of the anchorage end is 150.5 kN. After unloading, the cracks are closed, and no fibers are pulled out or broken. The internal force of the LEM-SHCC slab which absorbs the same longitudinal deformation of 10 mm is smaller than that of the SHCC slab with the same size. The internal force of the LEM-SHCC slab is greatly affected by the rubber powder content, and the LEM-SHCC slab has optimal performance when the content is 15%. The internal force of the LEM-SHCC slab is slightly affected by the friction coefficient at the slab bottom. In addition, the mechanical performance of the LEM-SHCC slab can be effectively improved by an increase in the slab length. It is recommended that the design length of the LEM-SHCC slab should be 8.5 m.