高强不锈钢钢筋混凝土梁短期受弯裂缝宽度和刚度计算方法研究

部分国产500 MPa不锈钢热轧带肋钢筋具有高延性、低弹性模量的特点，为研究配置此类不锈钢钢筋混凝土梁的短期裂缝与刚度特征，进行了6根配置不锈钢钢筋和2根配置普通钢筋的混凝土梁受弯性能试验，并分析不同混凝土强度和纵筋配筋率对短期裂缝和刚度的影响。试验结果表明：其他条件相同下，不锈钢钢筋梁与普通钢筋梁的裂缝形态基本相同，但不锈钢钢筋梁侧纵筋中心位置和梁底处的裂缝宽度均大于普通钢筋梁的；钢筋屈服前，不锈钢钢筋梁纯弯段的弯矩-平均曲率曲线呈双折线，但其开裂后刚度较普通试件的偏低，二者刚度之比平均为0.63；增加纵筋配筋率可减小裂缝宽度并提高受弯刚度。进一步收集相关文献中9根配置同类型国产不锈钢钢筋梁的试验数据，并对GB 50010—2010中短期裂缝与刚度计算公式的适用性进行评估。分析结果表明，按GB 50010—2010中的短期裂缝宽度公式计算得到的梁侧面纵筋位置处的平均裂缝宽度与最大裂缝宽度较试验值偏大，计算值与试验值之比平均分别为1.348和1.588；短期受弯刚度计算值较试验值偏小，二者之比平均为0.890，有必要对相关公式进行修正。建议将不锈钢钢筋梁的裂缝宽度控制位置调整至受拉边缘，且将裂缝宽度限值取为0.4 mm。通过统计分析，提出短期受弯裂缝宽度和刚度计算公式的修正建议。建议公式计算值与试验值吻合较好。

Study on calculation method of short-term bending crack width and stiffness of concrete beams reinforced with high-strength stainless steel bars

Some domestic 500 MPa grade stainless steel hot-rolled ribbed steel bars have the characteristics of high ductility and low elastic modulus. In order to study the short-term crack and stiffness characteristics of concrete beams reinforced with this type of stainless steel bars, six such concrete beams and two ordinary reinforced concrete beams were tested. The influence of different concrete grades and longitudinal reinforcement ratios on short-term cracks and stiffness was analyzed. The test results show that the crack pattern of the stainless steel-reinforced beams is similar to that of the ordinary beams, but the crack widths at the positions of the longitudinal reinforcement center on the side of the beams and at the bottom of the beams are larger than those of the ordinary beams. The moment-average curvature curve within the pure bending regions of the beams has a bilinear shape, and the stiffness is lower than that of ordinary beams after cracking with an average stiffness ratio of the two being 0.63. The increase of the longitudinal reinforcement ratio leads to a reduction of the crack width and an increase of the bending stiffness. Moreover, the test data of nine concrete beams reinforced with the same type of domestic stainless steel bars in the relevant literature was collected to evaluate the applicability of the formulae of short-term crack width and stiffness in GB 50010—2010. The analysis results show that the calculated values of the average crack width and the maximum crack width at the position of the longitudinal bars on the side of the beam according to GB 50010—2010 are larger than the test results, and the average ratios of calculated values to the test results are 1.348 and 1.588, respectively. The calculated value of stiffness is smaller than the experimental value with an average ratio of the two being 0.890. It is suggested to modify the relevant formulae and adjust the control position for crack width to the tension edge of the beam with the maximum crack width being no more than 0.4 mm. The revised formulae for the short-term crack width and stiffness were proposed based on a statistical analysis. The calculated values of the suggested formulae agree well with the test results.