Fine Analysis Of Light Steel Tube Truss-OSB Composite Floor

The light steel tube truss with Z sharped clips-OSB composite floor which is composed of truss beam and OSB connected by screw is a new composite floor. The light truss beam is made up of rectangular tube and Z clip connected by screw. Past studies are limited to a small amount of tests and simple finite element analysis, lacking fine analysis model. In the thesis, firstly, the nonlinear performance caused by slip of screws is considered by spring element with ABAQUS. Then the fine finite element model of light steel tube truss-OSB composite floor is established. Besides, the results of fine finite element model are compared with the experimental data. Finally, the factors which influence the bearing capacity of composite floor are analyzed comprehensively. Meanwhile, the optimized values of the main influencing factors are obtained.Firstly, the shear performance of screws which connect steel-steel and steel-OSB is studied in the thesis. Then the shear stiffness of screws for variation thickness of plate steel and steel plate-OSB is got through the test. The test results indicate that the thickness of steel plate has a great impact on the shear stiffness of screws which connect steel plate and steel plate. Besides,The thickness of OSB has a great impact on the shear stiffness of screws which connect steel plate and OSB. However, the thickness of steel plate has a little impact on shear stiffness of screws.The fine finite element model which considers the slip of screws, contact and material nonlinearity is established with ABAQUS. Then, the results calculated by finite element are compared with the test results by the final failure pattern, load-deflection curve and load-strain curve. Finally, the results indicate that the failure patterns of the component are almost same in fine finite element and test. Besides, the error of bearing capacity and deflection is very small. Therefore, the fine finite element model is accurate and effective.Finally, the factors which influence the bearing capacity at serviceability limit state and ultimate bearing capacity for composite floor are analyzed by the fine finite element model. The results of analysis indicate that the bearing capacity at serviceability limit state and ultimate bearing capacity can not be improved through increasing the thickness of OSB. Therefore, the thickness of 9mm or 12 mm for OSB is suggested in the thesis. The ultimate bearing capacity can be improved by reducing the space of screws. However, the bearing capacity at serviceability limit state can not be improved by reducing the space of screws. Therefore, the thesis suggests that if the thickness of upper chord rectangular tube is 0.8mm-1.2mm, the spacing of screw is 50mm-150 mm. Besides, the spacing of screw should be smaller when the rectangular tube is thinner. Both the bearing capacity at serviceability limit state and ultimate bearing capacity can be improved by increasing the thickness of the upper and bottom chord rectangular tube. However, the increment of bearing capacity by increasing the upper chord rectangular tube is larger than increasing the bottom chord rectangular tube. The ultimate bearing capacity can not be greatly improved by increasing the height of the upper or bottom chord rectangular tube within a centain height, but the bearing capacity at serviceability limit state can be improved effectively. Finally, according to material dosage optimized analysis, the paper suggested that the ultimate bearing capacity of composite floor is improved by giving priority to increase the thickness of upper chord rectangular tube. The bearing capacity at serviceability limit state of composite floor is improved by giving priority to increase the height of chord rectangular tube.