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Abstract A new welded joint of steel bracing is proposed. This new joint can be fixed soon after excavation without second welding，which can be rotated in some degree and can be prestressed. These measures can overcome the disadvantages of traditional welded joint，i.e. time increase of deep foundation exposure when using welding joints of diagonal bracing，inconvenient fixation of the slant angle immobility of diagonal bracing，and the prestress not being born on diagonal bracing after welding. It makes the time-space effects on deep foundation excavation obviously being reduced in soft clay areas. The bearing capacity of welded joints is studied by static load test on a welded steel rack with the same size. The test results reveal that the bearing capacity of the welded joint satisfies the requirements of design with a load of 2 500 kN. The whole structure remains stable only with some parts of the welded joint being yielded when load reaches 3 000 kN，and local concrete ahead of the embedded steel plate is crushed. The performance of the welded joint in the process of loading is simulated by finite element method(FEM). The calculation loading curve is consistent well with the test. The new welded joint of diagonal bracing can be used widely in deep foundation excavation with further processing.
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Received: 04 January 2009
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