型钢混凝土粘结滑移性能试验研究

Experiment study on bond slip behavior between section steel and concrete in SRC structures

通过淹钢混凝土标准推出试验(push-outtest),对型钢混凝土粘结滑移受力机理、粘结强度和粘结滑移本构关系等关键问题进行研究。采用正交试验法设计16个标准推出试件,主要研究混凝土强度等级、型钢埋置长度、横向配箍率和型钢的混凝土保护层厚度等四个主要因素对粘结滑移性能的影响,考察型钢翼缘外侧、翼缘内侧及腹板与混凝土粘结性能。并设计4个对比推出试件,单独考察型钢翼缘外侧对粘结作用的贡献。试验研究结果表明,在荷载上升阶段和荷载下降阶段内部型钢应变分别呈指数分布和线形分布;在型钢翼缘外侧、翼缘内侧和腹板等不同部位,界面内部滑移具有相近分布规律;在荷载下降阶段,型钢翼缘外侧相对翼缘内侧及腹板对总体粘结作用贡献更大。根据所有试件的加载端和自由端的荷载-滑移曲线试验结果,统计回归出型钢混凝土特征粘结强度和特征滑移值计算公式,并提出型钢混凝土平均粘结应力-加载端滑移本构关系的数学模型(-τSL模型)。

A series of push-out tests were conducted to study the bond mechanism, bond strength and bond-slip constitutive relations between section steel and concrete in SRC structures （steel reinforced concrete structures）. Sixteen standard push-out specimens are designed based on orthogonal design method, to study the differences of bond performance between exterior surfaces, interior surfaces of flanges as well as web surfaces of the section steel, and four main variables including concrete strength, volume ratios of stirrups as well as embedded length and thicknesses of concrete cover of section steel axe taken into account. Four comparison specimens are additionally adopted in which interior surfaces of flanges and web surfaces axe isolated from the concrete, to study separately the contribution of exterior surface of flanges to bond strength. From the test results, along the embeded length, the section steel strain is exponentially distributed at load-ascending stage and linearly distributed at load-descending stage respectively. The slip values and its distribution axe very close on the interfaces at exterior surface, interior surface of flanges and webs of the section steel. The contribution to total bond strength of exterior surface of flanges is bigger than that of interior surface of flanges and web surfaces at load-descending stage, but there is little difference between contributions of different surfaces at load-ascending stage. According to the experimental load-slip curves reordered at load-end and free-end of all specimens, a set of calculation formulas of three characteristic bond strength and three characteristic slippage values are established by regression method, and the mathematic mode of constitutive relations between average bond stress and slip at load-end which is usually named as τ^--SL relations is presented.