深圳岗厦北地下综合交通枢纽站桥合建大跨度组合结构复杂节点受力性能研究

A 51. 2 m×48. 0 m column-free atrium was designed in the Gangxia North transportation hub in Shenzhen; the structural span is one of the largest in the world for open-cut underground metro interchanges. In addition, the underground hub structure is also under a busy main road and sustains a 72 m-span overpass. The structure with huge open space, integrated with the underground hub and the upper overpass, is subjected to complex and super heavy loadings and consequently designed including five types of structural members, including concrete filled steel tubular column, steel reinforced concrete beam, steel reinforced concrete column, steel box beam, and reinforced concrete beam. This study was conducted to check the reliability of the above complex joints. Based on the whole structural analysis, the original complex structure was simplified from 9-column structure, 5-column structure, 3-column structure to the final 3-column structure with a cantilever beam to realize torsion consideration. The tested specimen was designed with a 1 / 5 scale. In the test, the specimen was vertically loaded by jacks at 7 locations, with 6 in the frame plane and one out-of-plane on the cantilever beam. The test and numerical analysis results show that, under design loads, concrete cracks develop on the steel reinforced concrete transfer beam, but the measurement illustrates that the steel section and reinforcement bars embedded in the concrete are still working in elastic stage. The maximum deflection of the transfer beam is 1 / 930 span which is within the required range. The piers and beam connection performed safely and satisfactorily under designed loadings. In the process of the action increasing up to 150% of designed loads, the cracks on the transfer beam continued to turn up, grow and extend while the stress of inner sectional steel and bars is still less than their corresponding yield strength. Neither crushing nor spalling of the concrete can be observed in the whole joint. The beam and joint are generally working in elastic stage. Moreover, the torsion moment illustrates obvious effects on the stress and deformation of the transfer beam and intensifies the eccentricity on the steel reinforced concrete column underneath.