考虑钢纤维混凝土卓越韧性的铺面结构设计理论

High strength steel fiber reinforced concrete (SFRC) has excellent post cracking performance, but the current pavement design methods allow no the surface cracking, and do not consider the bearing capacity of steel fiber reinforced concrete at the plastic stage. In addition, the current industrial floor design guidelines are based on the ultimate bearing capacity of the Winkler foundation plate, which is on the basis of rigid plastic theory. This theory is applicable for fixed-point loads, but not the movable loads, and its mechanical hypothesis is relatively rough. Besides, most of the current domestic and international researches on the performance of SFRC do not consider the distribution of steel fiber, thus how to apply the results to the actual project remains to be demonstrated. In this project, the mechanical properties of SFRC materials in the elastic and plastic phases are studied by double-punch test and beam test. The relationship between the distribution of steel fibers and the mechanical properties is studied based on CT technology. Secondly, the theory of ultimate bearing capacity of existing foundation plate is improved by elastic-plastic theory and field test, and extended to the rectangular plate, and the design method of SFRC pavement structure under fixed load is established. Furthermore, Through the bending test of foundation beam, the constitutive relation of SFRC under the condition of repeated load, and small beam fatigue life equation considering toughness is established ; Finally, transversely isotropic plate theory and elastic-plastic finite element method are used to study structural response of the SFRC pavement under the action of flow load, and the appropriate structural analysis method is established.

高强钢纤维混凝土（SFRC）具有卓越的裂后韧性，但现行国内外道路、机场铺面设计方法均以不允许面层开裂为设计准则，无法计入该优点；现行工业地坪设计方法虽可考虑SFRC裂后韧性，但它仅适用于定点荷载且其力学假设较粗糙；另外，现有国内外SFRC性能研究大都未考虑钢纤维分布影响，其成果难以直接指导铺面工程实践。本项目拟通过双冲试验及小梁弯曲试验，弄清SFRC材料弹性和塑性阶段的力学性能；应用CT技术研究钢纤维在混凝土中分布规律及与其力学特性间的关系；基于弹塑性理论及足尺试验对现有地基板极限承载力理论加以改进和验证，并拓展至弹性地基上矩形板，建立适合定点荷载的SFRC铺面结构设计方法；通过地基梁弯曲试验，弄清重复荷载条件下的SFRC弹塑性本构关系，建立计入SFRC裂后韧性的小梁疲劳寿命方程；采用横观各向同性板理论和弹塑性有限元法，研究带裂缝铺面的结构响应，建立适合流动荷载的SFRC铺面设计方法。

现行国内外道路等承受流动荷载作用的铺面结构设计方法不能考量允许带裂缝工作的钢纤维混凝土卓越韧性；现行建筑地面、工业地坪设计方法虽可考虑钢纤维混凝土裂后韧性，但其力学模型粗糙且仅适用于定点荷载工况，亟待改进。第三，钢纤维混凝土中钢纤维分布与成型方式密切相关，室内成型试件与实际工程面板浇筑之间的差异有待厘清。.通过X-ray CT技术及室内力学试验研究了包括成型方式、基体强度、钢纤维长度和掺量、粗骨料最大粒径等不同条件下的钢纤维分布规律及钢纤维混凝土强度特征，揭示了钢纤维分布在室内试模成型与室外浇筑成型中差异本质，提出了评价铺面钢纤维混凝土抗裂性能与力学强度的试件成型与测试方法；建立了通过四点弯曲试验反推钢纤维混凝土本构关系的方法，厘清了静态一次荷载和重复荷载条件下的钢纤维混凝土的弹塑性本构关系，建立了计入钢纤维混凝土裂后韧性指数的小梁弯曲疲劳寿命方程。证实了用电感试验法评判钢纤维在混凝土中掺量及分布方向性的可行性，为快捷且低成本的评价试钢纤维分布提供了新手段。.基于弹塑性理论对现有地基板极限承载力理论加以改进和验证，足尺寸试验证实了板极限破坏时裂缝宽度与Re,150时裂缝宽度相对应，完善了适合定点荷载作用的钢纤维混凝土铺面结构设计方法；推演得到四边自由的文克勒地基上正交异性双层板的解析法，建立了可考虑带裂缝工作的铺面结构力学响应，回归给出了路面板在轴载作用下路面板层底最大弯拉应力值公式，建立了适合流动荷载作用的钢纤维混凝土铺面结构设计方法。