Tenon-mortise Joints Research Articles

Seismic vulnerability analysis of palace-style timber structures base on lumped mass model considering column rocking effect

To investigate the influence of joint reinforcement on the vulnerability of palace-style ancient timber structures, a spring-rigid rod analysis model was established, considering the mechanical behavior of tenon-mortise joints, column base joints, and bracket set joints. A lumped mass model was proposed using the centroid method and stiffness equivalent method and the accuracy of the simplified model is verified through shake table tests. Additionally, the influence of reinforcement on tenon-mortise joints and bracket set joint on the seismic displacement response was investigated, the optimal reinforcement range for joints was determined. Finally, incremental dynamic analysis was conducted on the model considering joint reinforcement, and the influence of optimal joint reinforcement on the seismic vulnerability of timber structures was researched. The study found that the optimal stiffness enhancement of column frame mortise-tenon joints range from 4 to 6 times and the stiffness of bracket set joints by 2.9 times. The probability of structural collapse of reinforced both mortise-tenon joints and bracket set joints was reduced by 15.56 %. However, individually reinforcing either tenon-mortise joints or bracket set joints only slightly decreases the probability of collapse.

Seismic Performance Analysis of Ancient Palace-Style Timber Structure Considering Column Rocking Effect

ABSTRACT The seismic response of palace-style timber structures is closely related to the rocking characteristics of column. To accurately describe the dynamic characteristics of timber structures, a nonlinear rotational spring is employed to simulate the rocking behavior of column base joints under seismic excitation. Firstly, a spring-rigid rod analysis model that comprehensively considers the nonlinear properties of column base joints, mortise-tenon joints, and bracket set joints is proposed, and a simplified lumped mass model is obtained through centroid method and equivalent stiffness method. The accuracy of the simplified model is verified through shake table tests, and nonlinear dynamic response time-history analysis of the structure is conducted. Based on the verified simplified model, the influence of tenon-mortise joint reinforcement on the seismic displacement response of the structure was further investigated. It was found that carbon fiber sheets reinforcement increased the initial stiffness of the joints by 1.45 times and reduced the displacement response of the structure by 15%. Additionally, the optimal stiffness enhancement of column frame mortise-tenon joints range from 4 to 6 times.

Degradation of Mechanical Performance of Hoop Head Tenon-Mortise Joint of Tusi Manor with Decay Disease in Tibetan Areas in Yunnan

(1) The Hoop Head Tenon-mortise Joint (HHTMJ) in the Tusi Manor in Tibetan areas in Yunnan, China, has a serious decay phenomenon. To understand the effect of decay on the seismic performance of HHTMJ, (2) the five groups of HHTMJ and small-size Pinus kesiya var. langbianensis wood mechanical property testing specimens were placed in an artificially set decay environment and cultivated together with wood decay fungi for 0, 6, 12, 18, and 24 weeks, respectively. Low-cycle repeated loading tests were conducted to compare the failure mode, hysteresis curve, skeleton curve, and cumulative energy consumption of the HHTMJ under different decay cycles. (3) The results indicate that the failure mode of the HHTMJ is fractured at the tenon shoulder, and the deformation and failure of the tenon increase with the increase in decay. Compared with the non-decayed specimens, the ultimate bearing performance of the specimens after 6, 12, 18, and 24 weeks of decay decreased by 8.83%, 16.97%, 19.69%, and 30.22%, respectively. The cumulative energy consumption decreased by 21.6%, 27.4%, 33.2%, and 41.3%, respectively. (4) Decay primarily occurs on the exterior of the tenon, with minimal decay on the interior. The degradation of seismic performance in HHTMJ is relatively close to the degradation observed in small-size wood specimens during mechanical property testing.

Construction Forms and Seismic Performance of the Ancient Chinese Buildings Joined by Tenon–Mortise Joints

Zijincheng, also known as the Forbidden City, is the largest and best-preserved ancient palace-type wooden building in China, built without using a single nail. Since it was built in 1420, it has served as a palace where the emperor lives and works. Almost 600 years old, it has gone through two dynasties (i.e., the Ming and Qing dynasties (AD 1368–AD 1912)) and 24 emperors. It has survived more than 200 devastating earthquakes throughout its history, and it is still standing strong. In this paper, the authors introduce the construction technology of the ancient Chinese wooden structure as well as the greatest secret of the well seismic performance of the Forbidden City. The study found that the secret to the Forbidden City’s ability to withstand many powerful earthquakes lies in the flexibility of its timber structure, which is mainly reflected in the application of the tenon-mortise joints, energy-dissipation capacity of Dougong brackets and shallow-buried columns. The seismic responses of a 1:5 reduced-scale model of Shoukang Palace of the Forbidden City under different earthquake magnitudes are studied through a series of shaking table tests.

Analysis of Rocking Behavior of Tang-Song Timber Frames under Pulse-Type Excitations

This paper investigates the rocking behavior of two free-standing columns capped with a freely supported superstructure in an effort to explain the seismic stability of Tang-Song timber frames subjected to pulse-type excitations. The geometric characteristics of the column determine the acceleration amplitude needed to create uplift of the rocking frame, which also affect the loss of energy during impact along with the mass ratio of the superstructure to the column. Two distinct rocking modes are analyzed according to whether the frame can be limited by the tenon-mortise joint. The expression that yields the minimum acceleration required to overturn the frame is derived within the limits of the linear approximation of the governing equation of motion. Different safety and overturning regions plotted on the stability diagrams indicates that the partially joint limitation may weaken the seismic behavior. The entirely limited frame will rock within the fixed amplitude caused by the joint gap and never topple down. Probability analysis results of the entirely limited frame suggest that a great majority of this type of traditional timber structures have excellent seismic capacity to resist the horizontal excitation.

Study on earthquake resistance behaviors of Taihe Palace by simulation

Taihe Palace in the Forbidden City in Beijing is the largest scale as well as highest level of Chinese ancient palace buildings. To effectively protect Chinese ancient buildings, the Taihe Palace is taken as example to study its earthquake resistance performances. Simulation means is considered for analysis. Based on typical constitutions of Taihe Palace such as freestanding column root, tenon-mortise connection between beam and column, bracket sets (tou-kung), heavy roof, filler wall and so on, its finite element model is built by ANSYS program. By modal analysis, response spectrum analysis and time-history analysis, its dynamic characteristic and seismic performances are discussed. Results show the basic frequency of Taihe Palace is 0.85 Hz, its main modes are of translation in level directions. There is little relation among main modes. Under 8 degree intensity of of frequently occurred earthquakes, internal forces of the building are within permission scopes, which means it is not destroyed. Under 8-degree intensity of rare occurred earthquakes, its maximum deformation value is within the permission scope, reflecting it does not collapse. The constitutions such as freestanding column root, tenon-mortise joint, bracket sets and so on are helpful for earthquake resistance. Thus the Taihe Palace has good aseismic performances.

Shaking table tests on seismic behavior of ancient timber structure reinforced with CFRP sheet

This paper presents an experimental study on seismic behavior of ancient timber structure reinforced with Carbon Fiber Reinforced Polymers (CFRP) sheet. Based on a 1:2 scale one-bay and one-story ancient timber structure destroyed by the simulated earthquake, CFRP was used to reinforce the damaged ancient timber structure. Three seismic waves, including El Centro wave, Taft wave and Lanzhou wave, were input as the excitation wave. The displacement and acceleration response of the Column base, Column head, Pu-pai-fang, Bracket set and Eaves beam, the earthquake shear of structure and the internal force Sun-Mao node were analyzed quantitatively. Furthermore, the failure pattern of structure and dynamic property were analyzed qualitatively. The research shows that the friction and sliding of column base, rotation of semi-rigid tenon-mortise joint and sliding of Bracket set made the amplitude of seismic response of the structure greatly diminish with dynamic magnification factor about 1 which was much smaller than that of concrete structure about 2–4, and completely met the design requirements of Chinese code for seismic design of building. The distribution of the peak shear force of structure along the height appears at head or base of column, rather than must be the column base. The cumulative energy dissipation of three energy dissipation members reinforced with CFRP under different seismic conditions was calculated.

Application of Modern Wood Product Glulam in Timber Frame With Tenon-Mortise Joints and Its Structural Behavior

Tenon-mortise joint is widely used in traditional timber structures around the world. This paper summarizes the results of an experimental study of the structural behavior of tenon-mortise joints made with glulam and CNC technology instead of traditional material and manual work. 30 full-scale tenon-mortise joints were manufactured and tested under monotonic loading, and the effects of dimension, shape, processing error and adhesive were evaluated. It was found that the round rectangular shaped tenon-mortise joints were comparable with traditional joints in terms of structural performance, but were time and labor saving. The variability of the proposed tenon-mortise joints was lower, which would benefit the design value. Applying adhesive between tenon and mortise increased the average stiffness by 4.3 times and average moment capacity by 27.4%, respectively. The gaps between wood members had little effect on the capacity and stiffness in monotonic bending but may influence the energy dissipation ability in cyclic bending. This study showed the feasibility of combining the traditional joinery method with modern wood products and manufacturing technology, which may promote the application of tenon-mortise joints in modern timber structures.

The effect of shoulder on the strength of the oval tenon-mortise joint

This paper presents the results of a parallel examination on the strength of oval tenon-mortise joints in two groups of test joints. Joints from group A were made with both shoulders of tenon, while joints from group B were made without the lower shoulder. Examination of strength was conducted on a chair joints rear leg-rail. The results of the examination indicated that joints in group A (oval tenon with the upper and lower shoulder) had a higher average bending moment capacity in comparison with the joints in group B (oval tenon without the lower shoulder). However, the significance of difference in strength between the two groups of joints was not confirmed by the statistical analysis.

Study on Dynamic Behavior of Ancient Timber Structures Roof

The roof model of the palace timber buildings was established according to the construction technology of the Ying-tsao fa-shih. Based on its analysis of dynamic behavior with shaking table test and ANSYS finite element software, the dynamic behavior of structure and its maximal response under different conditions were gotten, and also the dynamic magnification factor of the beams layer and the whole structure were gotten, at last the results got by shaking table test was compared with the numerical simulation. Research shows that the nature frequency of the model is 1.486 Hz which is much bigger than that of the whole structure; the maximal displacement of beam layer gradually increases with the increase of ground motion intensity and the height of structure; the vibration isolation performance of semi-rigid tenon-mortise joints in rare earthquake (400gal) is better than that in moderate earthquake (220gal) and frequent earthquake (110gal); the dynamic magnification factor between layers was about 1, and roof 0.9 or so.

Strengthening Analysis on Tenon-Mortise Joint of a Face Beam in Tai-He Palace in the Forbidden City in China

To protect Chinese ancient building,by theoretical calculation and finite element simulation sinkage as well as strengthening method on tenon-mortise joint of a face beam in Tai-He Palace in the Forbidden City were studied.2 strengthening methods were considered,by which calculation diagrams as well as finite element models for the beam were built and static analysis were carried out.Based on analysis results,displacement as well as stress distributions of the face beam before strengthened were obtained;Based on laws of cultural relics protection,the 2 strengthening methods were discussed and the more suitable one was selected.Results show that the main cause of sinkage of the face beam tenon relates closely to over great values of bending,tension as well as shearing stress values at the tenon-mortise joint position;The method that strengthening tenon-mortise joint by additional columns under the face beam may bring adverse effects to the substructure,however the method of using steel-wood composite system to strengthen the joint is more suitable which meets the demand of cultural relics protection.

Aseismic Analysis on a Strengthened Chinese Ancient Building by Simulation

In order to protect Chinese ancient buildings,a Qing Dynasty building in Sichuan province was taken as example to study its aseismic characters after strengthened. By ANSYS program,semi-rigid character of tenon-mortise joint as well as contact between wooden constitution and walls were simulated.Then by modal analysis basic frequency as well as main modes of the structure were obtained;By response spectrum analysis inner forces as well as displacements of the structure under 7-degree intensity of seldomly occurred earthquakes were obtained.Results show that after strengthened,main modes of the structure are of translation;Under 7-degree intensity of seldomly occurred earthquakes peak values of displacement as well as inner forces of the strengthened building are all within permissible scopes,which proves its good aseismic characters.

The Earthquake-Resistant Properties of Chinese Traditional Architecture

This article explains why Chinese traditional architecture has effective earthquake-resistant properties. First the many factors that affect the response of buildings to earthquakes are presented. The article goes on to describe the features of Chinese traditional architecture that contribute to reduction of earthquake actions: the shape, configuration, and integrality of the traditional structure, particularly the excellent damping effect of the ductile tenon-mortise joint and the bracket set. Yingxian Pagoda and the Guanying Pavilion, two timber structures built around 1,000 years ago, have resisted many strong earthquakes, and an explanation is given for their excellent performance. The ability of masonry pagodas to withstand earthquakes is discussed with respect to non-occurrence of resonance, and the integrality and configuration. In the conclusion, the author answers the question of whether the good aseismic behavior of Chinese traditional building resulted from measures deliberately taken by the ancient builders.