Seismic Behavior of Damaged Ancient Timber Buildings: Multi-Scale Finite Element Model, Performance Degradation, and Experimental Verification

This paper presents a multi-scale modeling methodology for predicting the hysteretic behaviors of damaged ancient timber joints as well as the global seismic behavior of damaged ancient timber structures. The mortise and tenon (M-T) joint and column foot (C-F) joint, as the key load-bearing components of the structure, were modeled using detailed solid elements. Timber components that were large in size and not easily damaged were simulated using beam element. The interface connection between the detailed elements and beam elements was achieved using the displacement coordination method. The detailed and the multi-scale finite element models (FEMs) for M-T and C-F joints were established using the ABAQUS. The hysteretic curves, failure modes, and computing efficiency of two types of FEMs were compared. The feasibility of interface connection method of the multi-scale FEM was validated through cyclic loading test results of the joints. Based on the verified multi-scale interface connection method, detailed and multi-scale dynamic analysis models for a hall-type ancient timber building were developed using the ABAQUS, and validated through shaking table tests in terms of their dynamic characteristics and responses. Additionally, parametric analyses were performed to investigate the effects of the gaps between the mortise and tenon, as well as damage to the C-F joint, on the seismic behavior of ancient timber buildings. Degradation formulas for the key parameters of seismic behavior for damaged ancient timber structure were established. It is found that the model predictions were in good agreement with the test results. Under minor earthquakes, damage to M-T and C-F joints had negligible effects on the overall deformation capacity of the structure. However, under moderate earthquakes, a damage degree of 0.3 in the M-T joint resulted in a 6.20% reduction in the maximum inter-layer drift ratio of the Dou-Gong story, while the maximum inter-layer drift ratio of the column-frame story increased by 8.33%. With a damage degree of 0.52 in the C-F joint, the maximum inter-layer drift ratio of the Dou-Gong story and the column-frame story of the structure reduced 17.92% and 12.50%, respectively.