Full-scale Experimental Investigation On Direct Welding And Cold-formed Thin-wall Rectangle Tubular Truss

The key technological problem of the direct welding rectangle tubular construction design is the calculation of joint limit load-carrying capacity. This research is being on the rise in our country, involving different level of research Massive research achievements have been published. However, due to limiting research funds and test condition , the research work is mainly focused on computer simulation and individual joint test, Obviously, the research results lack of full-scale test confirmation. In this thesis, a pin truss was stochastically selected from the construction site and then undergone the full-scale destructive test in the structure laboratory. 100 strain measuring points were placed at the location of members and joints, For each joint, 9 vertical, 2 horizontal and 4 corner measuring points were required to confirm structure safety and the rationality of joint design . Many practical achievements were obtained from the test, and the experimental data was consistent with the theoretical expectation. Thorough analysis on the existing standard formula was undertaken. Hopefully, the test may provide some theory basis for the futuristic design of rectangular tubular truss, and provide the full-scale test data for the further revision of the standard of rectangle tubular construction. The main research work is described as follows:1 Experimental confirmation of the calculation model: Through the calculation of truss member strength and the analysis of secondary stress influence and truss rigidity, the consistency comparison between the full-scale truss test data and theoretical expectation showed that truss internal force calculated according to the hinge truss model can be applied practically to construction design . At the stage of elastic design, experimental deviation is small, and experimental value is consistent with theoretical estimation . The experimental data showed that the secondary stress can be ignored, because it only occupies a small proportion of the theoretically calculated value of the axial stress. The limit value of vertical deflection can be calculated according to the hinge model and should be reduced 1.15 times when using in construction design.2 Experimental investigation: The pin truss destructions mainly include truss member destruction and joint destruction . By observing the features of truss destruction, combing with the full-scale test data for determining the whole truss load-carrying capacity and limit destruction load , the safety and rationality of truss design can be estimated . These data may provide helpful reference for truss design in the future. The experimental investigation showed that with regard to truss design, one should not only consider the strength design of truss member , but also pay attention to joint design .Usually, the destruction of joint is the direct reason for destroying the whole truss. The truss load-carrying capacity obtained from the full-scale test is 1.14 times of theoretical value, and the truss limit destruction load is 1.88 times of theoretical value. After the joints are reinforced, the increasing range of the joint load-carrying capacity is varied for different joint pattern. If the whole truss destruction is controlled by the internal force of truss member, the enhancement of truss load-carrying capacity will be apparent when considering the influence of cold-formed effect. The truss member amount and joint load-carrying capacity estimated according to the present standard (GB50017-2007) and (GB50018-2002) can reflect the real features of truss destruction, and the theoretical value is in good agreement with the test data.3 Parameter investigation : The rules for the design of joint limit load-carrying capacity of rectangle tubule are listed for the first time in the present standard in our country. In this thesis , massive example analysis were carried on aiming at the calculation formulas relevant to various joint pattern, the results revealed some rules regarding the effect of joint parameter on joint limit load-carrying capacity, and may provide some reference to the designers on how to better understand and use the standards.