Abstract
This paper presents the results of a study on seismic performance of mortise-tenon joints with different lengths that tenons pull out of joints. Three 1:3.52 scaled mortise-tenon joint specimens were fabricated: one with through-tenon joints, one with half-tenon joints, and one with dovetail joints. Seismic data of the joints, such as hysteretic curves, skeleton curves, stiffness degradation rules, and energy dissipation capacity curves, were obtained by low-cycle reversed loading test. The influence of lengths that tenons pull out of joints on the mortise-tenon joints was analyzed. The seismic performance of three types of mortise-tenon joints was compared. The results showed that all hysteretic loops are z shaped. The seismic performance of the through joint was the best among three types of mortise tenon joint. The length that the tenon pulls out of the joint significantly affected the performance of the mortise and tenon joints.
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Experimental Study on Seismic Performance of Chinese Traditional Mortise and Tenon Joints with Different Lengths that Tenons Pull out of Mortise
Junhong Huan,a,b,c,d Tianyang Chu,a,b Xiaodong Guo,c,d,* Zemeng Sun,a,b Xiaoyi Zhou,a,b Wei Wang,c,d and Yating Yang c,d,e
This paper presents the results of a study on seismic performance of mortise-tenon joints with different lengths that tenons pull out of joints. Three 1:3.52 scaled mortise-tenon joint specimens were fabricated: one with through-tenon joints, one with half-tenon joints, and one with dovetail joints. Seismic data of the joints, such as hysteretic curves, skeleton curves, stiffness degradation rules, and energy dissipation capacity curves, were obtained by low-cycle reversed loading test. The influence of lengths that tenons pull out of joints on the mortise-tenon joints was analyzed. The seismic performance of three types of mortise-tenon joints was compared. The results showed that all hysteretic loops are z shaped. The seismic performance of the through joint was the best among three types of mortise tenon joint. The length that the tenon pulls out of the joint significantly affected the performance of the mortise and tenon joints.
DOI: 10.15376/biores.19.1.478-499
Keywords: Ancient timber buildings; Mortise-tenon joints; Seismic performance
Contact information: a: School of Civil Engineering, Shijiazhuang Tiedao University, Shijiazhuang, PR China; b: Key Laboratory of Roads and Railway Engineering Safety Control (Shijiazhuang Tiedao University), Ministry of Education, Shijiazhuang 050043; c: Faculty of Architecture, Civil and Transportation Engineering, Beijing University of Technology, Beijing, PR China; d: Key Scientific Research Base of Safety Assessment and Disaster Mitigation for Traditional Timber Structure (Beijing University of Technology), State Administration for Cultural Heritage, Beijing 100124, China; e: The College of Urban Construction, Hebei Normal University of Science & Technology, Qinhuangdao 066000, China; *Corresponding author: guoxd7797@163.com
GRAPHICAL ABSTRACT
INTRODUCTION
Chinese ancient architecture is an important part of Chinese civilization. According to Sun (2011), the number of existing Chinese ancient buildings is about 264,000. A large proportion of them are timber buildings, such as the Forbidden City in Beijing (Liang 2005). Chinese ancient timber structures architecture plays an important role in the history of world architecture in terms of its special aesthetic, artistic and cultural value; they are national treasures of China. However, data shows (Liang 1984) that since 2221 B.C., nearly 6,000 medium and strong earthquakes occurred in China and a large amount of ancient buildings were damaged and destroyed in the earthquakes. According to historical seismic data, 2 world cultural heritage sites and 169 national key cultural relics protection units were damaged in the Wenchuan earthquake (Wang et al. 2003). Therefore, it is important to conduct seismic research on ancient timber buildings to preserve this valuable cultural heritage.
Research on ancient buildings in China started in the 1980s. Liang Sicheng did a lot of research on the Chinese ancient buildings from the perspective of architecture (Liang 2005). Different from modern architecture, the beams and columns of Chinese ancient timber structures are connected by mortise-tenon joints without any nails, steel plates, or bolts. Therefore, mortise and tenon joints are key loading bearing and transmission parts of timber structures. Dutu et al. (2016), Vieux-Champagne et al. (2014), and Xie et al. (2019) investigated the seismic performance of timber frame systems with infill by cyclic load tests. Wu et al. (2018), Fang et al. (2001), and Shi et al. (2018) conducted experimental and numerical simulation studies on traditional Chinese timber frame structures to investigate their stiffness, damage modes, and other properties. Ali et al. (2012; 2022), Yeo et al. (2016), and Kaori (2019) investigated the dynamic performance of timber frame structures through experiments. Aejaz et al. (2021) used numerical simulations to evaluate the effect of geometric modifications on joint behavior.
Among the various types of mortise-tenon joints, the through-tenon joint, the half tenon joint, and the dovetail joint are the most widely used types of joints in Chinese ancient timber structures. Mortise-tenon joints help ensure the safety of ancient timber buildings in earthquakes (Ma 1991; Fang et al. 2000; Bai and Ma 2018). The mortise-tenon joints can bear and transmit loads and consume seismic energy when large structural deformation occurs in the earthquake. The mortise and tenon joints are important earthquake-resistant structural elements of timber structures (Chang et al. 2004; Zhao et al. 2012; Wu et al. 2019). Zhi (2014), Shields and Hindman (2015), Parisi and Piazza (2000), Hu et al. (2018), and Sha et al. (2021) investigated the mechanical properties of different types of mortise-tenon joints in timber structures. Experimental studies (Chen et al. 2016a; Crayssac et al. 2018) were carried out to investigate the mortise-tenon joints’ mechanical properties and seismic performance. Huan et al. (2019) put forward several reinforcement methods to enhance the mechanical properties of mortise-tenon joints. Shanks et al. (2008, 2009) performed pull-out tests on mortise-tenon joints and studied the stiffness, strength and failure modes of the test models.
Earthquakes (Yang et al. 2000), long-term loads, drying shrinkage (Xu 2006), and other natural environment erosion exacerbated the damage of mortise and tenon joints, especially the tenon pull out of mortise (King et al. 1996). Under the effect of earthquakes, the connection between column and beams loosened. The tenon pulls out, which reduces the load-bearing capacity and integrity of the whole structure. Therefore, it is necessary to investigate the seismic performance of the mortise tenon joints with gaps between mortise and tenon shoulder. Some scholars have studied the seismic performance of mortise-tenon joints with gaps in traditional timber structures. Xue et al. (2017, 2016) studied through-tenon joint and dovetail tenon joints with different looseness and damage degree based on model tests. The results showed that the looseness and damage decrease the energy dissipation capacity and rotational stiffness of the mortise tenon joints. Zhou and Yang (2017) studied structural health problems of mortise-tenon joints of timber buildings in the Forbidden City and recommended some strengthening methods for these tenon-mortise joints. However, studies on the seismic performance of mortise and tenon joints with different lengths that tenon pull out of mortise are rare.
In this study, three 1/3.52 scaled specimens of Chinese traditional timber mortise tenon joints for testing, including one through-tenon joint, one half tenon joint and one dovetail tenon joint, were fabricated according to Ying Zao Fa Shi in Song Dynasty (1950). The low-cycle reversed loading tests were conducted to investigate the seismic performance of different types of mortise-tenon joints. The effects of different lengths tenon pull out of mortise on the seismic performance of the joints were studied. The seismic performance of three types of mortise and tenon joints without tenon pull out of mortise were compared.
EXPERIMENTAL
Design and Fabrication of Specimens
One through-tenon joint, one half-tenon joint, and one dovetail tenon joint were fabricated according to Yingzao Fashi (1950). Yingzao Fashi, which was published in 1103 AD, is a specification for building construction in Song Dynasty of China. Three-dimensional views of mortise and tenon joints in the test are shown in Fig. 1. Dimensions of components are shown in Fig. 2. According to the Buckingham theorem (Kline 1965) and similitude theory, the structural properties of the prototype can be calculated by dividing the corresponding properties of the scaled specimens by the scale factors of the dimensions and mechanical properties of the materials (Chen et al. 2016b). Scale factors of the physical parameters are shown in Table 1.
Fig. 1. (a) Through-tenon joint; (b) half tenon joint; (c) dovetail tenon joint
Table 1. Scale Factors of the Physical Parameters
(a)