钢-再生混凝土界面黏结机制及强度计算方法

Performance of Interface Bond Mechanism and Method of Strength Calculation between Steel and Recycled Aggregate Concrete

为研究型钢、钢管与再生混凝土界面黏结作用机制,采用服役超50a的混凝土作为再生粗骨料来源,设计了31个试件进行推出试验,试验考虑了配钢形式、再生粗骨料取代率、长径比及混凝土强度等级4个变化参数对钢-再生混凝土黏结性能的影响.试验获取了各试件加载端和自由端的荷载-滑移曲线,并基于实测结果得到了3种钢与再生混凝土的界面黏结强度,分析了各变化参数对黏结强度的影响,探讨了钢-再生混凝土界面黏结强度的计算方法,推导了黏结剪力传递长度的计算公式.研究结果表明,钢-再生混凝土试件的加载端起滑均比自由端发展得早;型钢试件的黏结强度大于圆钢管试件,而圆钢管试件又大于方钢管试件;随再生粗骨料取代率的增加,试件的黏结强度略呈增大之势;随着混凝土强度的提高,试件的黏结强度有一定提高;方钢管与再生混凝土的黏结强度随长径比的增大而减小.

In order to study the interfacial bond failure mechanism among three types of steels and recycled aggregate concrete（ RAC）, a total of 3 ! steel-RAC short columns were designed to the push-out test, and in this experiment, waste concrete serving over 50 years was used as recycled coarse aggregate. Four changing parameters of steel disposition （cross-section shape ）, replacement ratio of recycled coarse aggregate, length to diameter ratio and concrete strength grade were considered to research their influences on bond behaviors of steel and RAC. Curves of load-slip at the end of loading and free end were obtained. The influence of each changing parameter on the bond strength was deeply analyzed. The interracial ultimate bond strength of each specimens was checked by practical bond strength formulas. The formula of interface bonding shear transfer length was deduced. The results show that the starting slip at the loading end developed earlier than the free end. Compared with the ultimate bond strength, the S-RAC＇s was larger than RAC-FCST＇s, and RAC-FCST＇s was larger than RAC-FSST＇s. The bond strength between steel and RAC was increased slightly as the increasing of recycled coarse aggregate replacement rate. Higher concrete strength was conducive to the improvement of bond strength. It would be decreased that the bond strength of square steel tube and RAC as the larger length to diameter ratio.