纤维混凝土组合桥面板裂缝宽度计算方法

Crack Width Calculation Method of Fiber Reinforced Concrete Composite Bridge Deck

摘要:

为了考虑纤维混凝土中纤维对裂缝的桥接作用并计入其对抑制组合桥面板混凝土裂缝产生与发展的有利作用，提出了一种纤维混凝土开裂后残余应力的计算方法和考虑残余应力的裂缝宽度计算方法。综合考虑影响混凝土开裂后残余应力f_R,1的因素有：纤维屈服应力σ_y、纤维体积率V_f、混凝土抗压强度f_cm、纤维长度l_f、纤维特征参数a，推导了上述因素对影响纤维混凝土开裂后残余应力的相关性。基于35组纤维混凝土梁三点加载缺口梁试验数据进行回归分析，并得到了具有95%保证率的f_R,1计算公式。在欧洲规范混凝土裂缝宽度计算方法的基础上，考虑纤维混凝土开裂后残余应力的贡献，提出了一种组合桥面板负弯矩区裂缝宽度的计算方法。通过一个纤维混凝土组合桥面板负弯矩加载试验对该计算方法进行验证，结果表明，计算得到的开裂后钢筋应力及裂缝宽度与试验结果吻合较好。

关键词:桥梁工程;裂缝宽度;残余应力;纤维混凝土组合桥面;负弯矩区

Abstract:

To consider the crack bridging effect of steel fibers in fiber reinforced concrete (FRC) and its beneficial effect of restricting crack initiation and development in composite bridge deck, a calculation method of residual stress and cracking width was proposed. The main parameters influencing the residual stress f_R,1 were yielding stress of fiber σ_y, fiber volume fraction V_f, compression strength of concrete f_cm, fiber length l_f, fiber aspect ratio a. The correlation between the afore mentioned parameters and the residual stress was derived. Based on the linear regression analysis from test results of 35 three-point bending tests on notched beam recorded in the literature, an equation to calculate f_R,1 with 95% confidence level was proposed. Including the contribution of residual stress in the calculation method for the composite structure under negative moment suggested by Eurocode 4, a crack width calculation method for FRC composite bridge deck was proposed. A FRC composite bridge deck specimen subjected to negative moment loading was used to validate the calculation method. The results show that the calculated rebar stress and crack width fits well with the tested value.

Key words:bridge engineering;crack width;residual strength;fiber reinforced concrete composite deck;negative bending region