Behavior Of Light Wood Frame Construction Under Wind Load

Light wood frame construction is introduced from North America into China. The dimension lumber and structural wood based panels used in China are usually imported from North America, but some other materials like nails and gypsum boards are made in China. The structural systems of light wood frame construction are the same as those in North America, except for some made-in-China materials used in engineering practice. The performance of the structures in China can differ from those in North America. In the national standard"Code for design of timber structures"GB50005-2003, design of light wood frame construction is only based on the stipulations of constructional arrangements. There are not any stipulations of the design method for resisting wind load, if it is larger than the stipulations. Besides, even at abroad there has not been unified understanding, so far, in the calculation of stiffness of the structure and the analysis of the whole structure under lateral load have not been unified. For this reason, this study of the behaviour of light wood frame construction under wind load has been initiated, which includes the behaviour of the nailed connections, structural components like shearwalls and floor diaphragms and the whole building structure.In this study, a total of 222 sheathing-to-frame nailed joints manufactured with common nails made in China were tested under the monotonic loading protocol, 90 of the same nailed joints were tested under cyclic loading protocol, and 40 bending tests of the common nails to obtain the yield strength and wood properties tests of 1482 specimens were also conducted. 14 full-scale shearwalls and 2 full-scale floor diaphragms were tested. Based on the test results of shearwalls, a FE model was developed, performance of some shearwalls with common dimensions were simulated using the FE model. Furthermore, 2 full-scale light wood frame construction houses, one on site and the other in the laboratory, were tested under simulated lateral wind loads.It was concluded from the study that the bending strength of common nail made in China falls within the internationally accepted range, close to the upper bound, the nails can be used in light wood frame construction; as a result, the strength of nailed connections is to some extent higher than that in North America with the same diameter of nail; gypsum board sheathing tends to be damaged when the lateral drift of shearwall reaches 1/400, as interior sheathings, the resistance and stiffness of gypsum boards can be used to resist lateral wind load to improve the performance and economy of the structures with in the lateral drift of 1/400; light wood frame construction exhibits obvious 3-dimensional behaviour in the whole building testing, and wood floor behaves nearly as a rigid diaphragm in distributing the lateral loads; though non-lateral-resisting members can significantly improve the racking stiffness of the building, the effect has not been taken into account in this study, due to lack of sufficient experimental data; light wood frame construction can resist cyclic wind loads without noticeable degradation in the racking resistance capability; in order to avoid degradation in stiffness it is desirable to limit the maximum inter-story lateral drift to 1/400.According to this study, the allowable inter-story lateral drift of shearwall is limited to 1/400 under serviceability limit state. Similar to that determining the racking strength of shearwalls, methods to determine the lateral shear strength and stiffness of the nailed connections and diaphragms were proposed. Based on the testing data, empirical formulas for calculating the strength and stiffness of the nailed connections were also given and new simplified formulas for calculating the racking strength and stiffness of shearwalls and floor diaphragms were recommended. Two simplified methods were also introduced to analyze the whole building structures in resisting lateral wind loads.Through the study, methods for design of light wood frame buildings resisting high wind loads and checking of the serviceability limit state and ultimate limit state were investigated and recommended. The recommendations can be used as reference to the supplements of design specifications in the national standard GB50005-2003.