Full Scale Experimental Study Of Ultimate Bearing Capacity For Big Dimention Steel Tubular Space Joint

ABSTRACT:The penetrated welded connection design is a key point in the structural design of tubular truss. The stress status of the connection cannot be obtained only from mechanics principle because the connection area has a complex geometric and material property, stress concentration, unpredicted impact factors, and various collapse modals. Furthermore, there is no current local structural steel design code for calculating the connection with the complex stress status due to the interaction effect between the multiple pipes around the connection.In this thesis, the four full-scale connections are made to conduct collapse test for the top and bottom chords of the tubular space truss of the roof, which is employed for the stadium of Guiyang Olympic Sports Centre as a case study. It is introduced of the test scheme, process, phenomenon, and results. The collapse modals are generated by performing an analysis of the test data and comprehending the stress distribution status of the connections on each load sub-step according to the full-step loading test character. Besides, the elasto-plastic finite element analysis (FEA) is performed for the connections to obtain their stress, strain and displacement by considering geometric and material nonlinearity and observing above test loading rules and process in ANSYS FEA Package, in order to demonstrate the strength capacity, plastic development zone, as well as stress and strain distribution status of the connections. Furthermore, the design strength capacity of the connections is calculated based on local Code for Design of Steel Structures, coMPared to the results from full-scale test and FEA analysis.As a result, the plastic hinge only occurs on the local area of the connections, and a majority of area still stays in the elastic status with the strength capacity being 2.5 times of the design load, which shows the connections are safe. On the other hand, the strengthening methods are brought forward for some weak area of the connections. There are two buckling collapse modals, saying local buckling of the chords and axial buckling of the web bars.CoMPared the results of the chords subject to compression from the test with that from the local code, it is summarized that the equations in the local code is rather conservative. Besides, the results from the test are in line with that from FEA with the strength capacity deviation of 8%～4%. On the basis of the results from the test phenomenon, data analysis and FEA, it is suggested that the minimum value from displacement or strength criteria is employed for the ultimate capacity determination of these connections.Finally, the results from this thesis can provide some references to other similar projects based on the analysis method and test for the big dimension tubular space steel joints.