Dynamic characteristics of Taiwanese traditional Dieh-Dou timber structures

This study attempts to explore the structural behaviour of traditional Dieh-Dou timber structure under different combinations of bracket structural forms and roof dead loads. The parameters used include two different structural forms (symmetric and asymmetric) and three different levels of roof weight (1.7, 2.6 and 3.5 tons) which represent the span distance between two parallel frames at 3, 4.5 and 6 meters. Two different semi full-scale specimens, made of China Fir (Cunninghamia lanceolata), were mounted and tested on the shaking table of National Centre for Research on Earthquake Engineering (NCREE) in Taipei. Time-history record (TCU 084) from the 1999 Chi-Chi earthquake in Taiwan was used to test at a level of 20, 42, 60, 80 and 100%. System identifications were carried out between every test to monitor the integrity of the structures. Results showed that increase vertical loadings will have significant effect on the natural frequencies and global structural stiffness of the specimens. Next, the experimental results were mapped with the theoretical model for initial stiffness prediction, whereby the entire structural frame was assumed to be a lump mass system with Single-Degree-Of-Freedom (SDOF). The predicted stiffness model is generally in good agreement with the dynamic results of both structural forms. This study suggests that the effects of increasing vertical loadings should be taken into consideration during future evaluation process. Although using SDOF system to estimate the initial stiffness seems highly probable, more work still needs to be undertaken on other types of theoretical models to find out the most optimal evaluation methods for Dieh-Dou timber frame.