钢-混凝土组合试件长期推出试验与有限元分析

采用推出试验和有限元方法研究了采用不同剪力连接件的钢-混凝土组合试件的界面长期滑移和应变发展过程; 参考Eurocode 4中推出试验标准试件, 设计了2组试件用于长期推出试验; 分别采用栓钉和PBL作为剪力连接件, 采用螺杆施加长期荷载, 测试了长期加载过程中的界面滑移、混凝土应变和钢梁应变; 同步加载测试了150 mm×150 mm×300 mm的混凝土试块的长期变形, 并以此变形计算混凝土徐变系数; 对比了徐变模型对计算结果的影响, 并讨论了不同混凝土徐变模拟方法。研究结果表明: 界面滑移和混凝土应变在加载初期增长较快, 加载120 d后达到稳定状态; 栓钉试件和PBL试件的最大界面滑移分别为0.162和0.068 mm, 最大值均位于界面底部; 栓钉试件和PBL试件的混凝土最大应变分别为7.30×10-5和1.34×10-4, 最大值均位于混凝土板底部; 钢梁应变在整个试验过程中基本保持稳定, 未出现明显的应力重分布, 栓钉试件和PBL试件的钢梁最大应变分别为3.7×10-5和6.5×10-5, 最大值均位于钢梁顶部; 混凝土徐变是影响钢-混凝土组合试件长期性能的主要因素, 不同混凝土徐变模型计算所得混凝土徐变系数与测试值的偏差为60%~140%, 说明混凝土徐变模型对有限元结果影响显著; 采用指数函数拟合混凝土徐变系数测试结果的拟合误差为2.4%, CEB-FIP90模型计算所得混凝土徐变系数在加载后期与测试值的误差为3.71%, 建议无法实测时可采用CEB-FIP90模型计算混凝土徐变系数。 

Long-term push out test and finite element analysis of steel-concrete composite specimens

The long-term interface slip and strain development process for steel-concrete composite specimens with different shear connectors were investigated through the push out test and finite element method. Referring to the standard specimen of push out test in the Eurocode 4, two sets of specimens were designed for the long-term push out tests. The studs and PBLs were used as the shear connectors, respectively, the long-term load was applied by screw rods, and the interface slip, concrete strain and steel girder strain were measured during the long-term loading process. The long-term deformations of concrete specimens with the dimensions of 150 mm×150 mm×300 mm were loaded and tested synchronously to calculate the concrete creep coefficient. The effect of creep model on the calculation result was compared, and different concrete creep simulation methods were discussed. Research result shows that the interface slip and concrete strain increase rapidly at the initial stage of loading and keep stable in 120 d after loading. The maximum interface slips of stud specimens and PBL specimens are 0.162 and 0.068 mm, respectively, and located at the bottom of interface. The maximum concrete strains of stud specimens and PBL specimens are 7.30×10-5 and 1.34×10-4, respectively, and located at the bottom of concrete slab. The steel girder strain remains basically stable during the whole test process. There is no obvious stress redistribution. The maximum steel girder strains of stud specimens and PBL specimens are 3.7×10-5 and 6.5×10-5, respectively, and located at the top of steel girder. The concrete creep is the main factor affecting the long-term performance of steel-concrete composite specimen. The errors between the concrete creep coefficients calculated by different concrete creep models and the test values are 60%-140%, indicating that the concrete creep model has a significant impact on the finite element results. When using the exponential function to fit the test result of concrete creep coefficient, the fitting error is 2.4%. The error between the concrete creep coefficient calculated by the CEB-FIP90 model and test value is 3.71% at the later loading stage. The CEB-FIP90 model is recommended to calculate the concrete creep coefficient when the actual test cannot be carried out.