| Cold-formed thin-walled light-gauge steel residential system has been widely used in the world with its good qualities of convenient to construct, easy to assembly and good for bearing under loads. To the entrance of the 1980s, cold-formed thin-walled light-gauge steel residential system was imported to our country. For nearly 30 years, this system has been making rapid development in China. There are a lot of institutions and enterprises to carry on research, and get some corresponding results.In such circumstances, Nest light-gauge steel system came out. It is mainly from web light-gage steel system of Canada, which is consist of rectangle tubes that are made of cold-formed thin-walled steel plate by rolling equipment and butterfly-like clips which are made of cold-formed thin-walled steel plate through the ram device. They are connected by self-tapping screws to form trusses which are the under-load members.Nest light-gauge truss beam is the basic unit of this system, the characteristics of this truss beam is that it is a lattice-plate truss beam. More over, the nodes of rectangle tubes and butterfly-like clips which are connected by self-trapping screws are semi-rigid. Because Nest light-gage steel system is a new comer, relative research is limited nowadays. It is necessary to carry on research for the truss beam of this system.The truss beam of Nest light-gauge system is choused for the main object of study in this paper,specific research as follows:1,In order to get the mechanical characteristics and failure mode,we take the five truss beams with different connections into research by experiments.2,In order to get the relationship between moment and rotation of joint which rectangle tubes connect to butterfly-like clips,we carry on the experiments of the joint.3,Do the analysis of the truss beam by SAP2000. To compared the experimental and analysis results and verify the rationality of the models.4,Put the most reasonable model into optimization design of the Nest light-gauge steel system truss beam,to design the reasonable arrangement of the truss beam.According to the arrangement of experiment and analysis, this article gets the following conclusions:1,According to the experiment, the falure position of truss beams is on the top chord and mainly concentrated in two places, which are the node that the top chord connects the first clips at the end and the node that the top chord connects the midspan clips.2,The joist of rectangular tubes and butterfly-like clips of truss beam is semi-rigid. Analysital results show that the models considering semi-rigid joist approach more nearly to the experimental specimens.3,Altering the spacing of the clips can alter the falure position of tuss beam. The effect on truss beam's bearing capacity is weak when the cpacing among cryptographic clips at the end is small enough. The effect on truss beam's bending rigid is not obvious when altering the spacing among cryptographic clips at the end. Conversely, the effect on truss beam's bending rigid is obvious when altering the spacing among non-cryptographic clips. To add the diagonal bracings can reinforce the end of truss beam, also can increase the bending rigid of truss beam, but it take little effect on bearing capacity of truss beam.4,The effect on bearing capacity of truss beam is obvious and on bending rigid of truss beam is not obvious by altering the cross section's thickness of top chord. Conversely, the effect on bearing capacity of truss beam is not obvious and on bending rigid of truss beam is obvious by altering the cross section's size of top chord.5,Adding board at partitial place on top chord can increase the bearing capacity of the place which top chord is to board with, but the effect on the bearing capacity and bending rigid for the whole truss beam is weak.6,To calculate the bearing capacity and midspan deflection of truss beam accurately, the joist of semi-rigid of truss beam must be considerated for finite element analysis. |
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