Mortise-tenon Joints Research Articles

Integrated preparation and compression behavior of novel 3D-Kagome lattice sandwich composite assembled by semi-rigid mortise-tenon joints

Integrated preparation and compression behavior of novel 3D-Kagome lattice sandwich composite assembled by semi-rigid mortise-tenon joints

Analytical investigation on the rotational behavior of dovetail mortise–tenon joints between beams and columns in traditional Chinese timber frames

We theoretically analyzed the rotational behavior of beam–column dovetail joints in traditional Chinese timber frames in this study. An analytical model of dovetail joints at both the column head and body was designed by clarifying the moment generation mechanism and effect of rotational embedment yielding in timber perpendicular to the grain on the rotational behavior of joints. An asynchronous manifestation of rotational embedment deformation across the column surface, tenon cheeks, and upper and lower surfaces of the tenon head was analyzed, and the corresponding characteristic yield points and consequent reduction in rotational stiffness were derived in the model. The Inayama embedment theory was used to clarify the effect of rotational embedment with varying end lengths on the movement of the joint rotation center and asymmetric moment generated in different rotation directions of the column head joint. The precision of the analytical model was validated through a comparative analysis by involving nine sets of experimental data, for estimating the initial stiffness, post-yield stiffness, and identified yield points. The implications of the parameters, including the initial gap between the tenon and mortise, geometric dimensions of the dovetail tenon, and friction coefficient, were also discussed. Controlling the ratio of the initial gap and tenon height within 0.01 to ensure a certain rotational resistance of dovetail beam–column joints within the collapse limits of traditional timber frames is recommended considering the significant effect of the initial gap on the initial sliding angle and moment reduction.

Biaxial shaking table tests on a full-scale single-storey traditional Greek stone masonry and timber-framed composite structure

Biaxial shaking table tests were carried out on a full-scale, single-story specimen of a traditional Ottoman-period Greek structure, comprising a stone masonry wall with timber ties and three timber-framed masonry walls with fired clay brick infill. Timber posts and beams were connected with cylindrical mortise-tenon joints. The dynamic characteristics before and after seismic testing were determined with sine sweep tests. The specimen proved capable of withstanding peak ground accelerations equal to the highest seismic zone of Greece. Most damage concentrated in the stone wall, while rocking behavior at the post-sill-beam joints was observed for the timber-framed ones, which only showed minor damages. Finally, interventions are suggested based on the experimental results.

Intergrowth MFI Zeolite with Inverse Al Zoning and Predominant Sinusoidal Channels for Highly Selective Production of Styrene.

ZSM-5 zeolites with accessible micropore architecture and tunable acid-base sites are important shape-selective catalysts. However, the presence of exposed straight channels and the external acid-base sites of conventional ZSM-5 has a negative impact on shape selectivity. Herein, we report on the direct synthesis of an intergrowth ZSM-5 zeolite mimicking the mortise-tenon joints. It can be revealed by various methods that the mortise-tenon ZSM-5 shows an inverse Al gradient from the surface to the core of the zeolite. More importantly, the sinusoidal channels predominantly opened to their external surfaces are constructed. The shape-selective capability of the ZSM-5 zeolite has been fully exploited due to the intrinsic inert external surface and unique sinusoidal channel features, thereby resulting in high styrene selectivity (>90%) and good catalytic stability (>100 h) in the toluene side-chain alkylation reaction. In addition, in situ DRIFTS confirms that this intergrowth ZSM-5 contributes to the formation of more active intermediates of HCOO* and H3CO*, which is another reason responsible for the superior performance.

Seismic performance of Li-Tie type brick masonry infilled wooden frames considering joint damage: Degradation mechanism and hysteretic model

This paper investigated the influence of the damage to column-foot (C-F) joints and the gaps of mortise-tenon (M-T) joints on the seismic behavior of Li-Tie style timber frames with masonry-infilled wall. Five full-scale Li-Tie type brick masonry-infilled timber frames, two without the joint damage, two with the damage to C-F, and one with the gaps of M-T joints, were cyclically tested. The failure modes, mechanical and deformation mechanisms were revealed. The second-order effect, strength degradation law, and the changing laws of the equivalent viscous damping coefficient and strain of the specimens were analyzed. The results showed that when the maximum inter-layer drift ratio was less than 2.4 %, the second-order effect of Li-Tie type timber structure with the masonry infill can be ignored. The masonry infilled timber frames considering the joint deterioration suffered a large strength degradation degree, and a more significant loss of the peak load and ductility. The equivalent viscous damping coefficient of the masonry infilled timber frame considering C-F damage increased by up to 24.67 %, while that of the one including the gaps of M-T joint decreased by 6.67 %. The C-F damage led to an increase in the strain at the beam end, the damage to M-T joint resulted in an decrease in the strain at the beam end. However, the damage to C-F and the gaps in M-T joint had little influence on the strain distribution in the C-F area. Based on the hysteretic, stiffness and strength degradation characteristics, and tests results of the specimens, the new tri-linear hysteretic models of Li-Tie type brick masonry infilled wooden frames with and without the joint damage were established and verified. Good agreement between the model predictions and test results was observed.

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.

Experimental and numerical study on seismic performance of assembled platform canopy with mortise-tenon joints

To investigate the seismic performance of a Y-shaped single-column platform canopy assembled using mortise-tenon joints, a 1:4 scaled specimen with two roof panels was fabricated using a real assembly process. The seismic performances, including the failure mode, hysteretic behavior, bearing capacity, ductility, and energy dissipation capacity, were measured by a low cyclic loading test, and the main influencing parameters, such as the longitudinal reinforcement ratio, linear stiffness ratio of the laminated beam to the precast column, and canopy slab height, were analyzed using validated finite element models. The test results showed that the hysteretic curve presented a pinch effect, indicating shear slip characteristics. The ultimate drift angle was 1/17, and the displacement ductility coefficient was greater than 4.5, indicating that the structure has good deformation capacity and ductility. Plastic hinges appeared at the ends of the laminated beam and base of the prefabricated columns, and the failure mode was the beam-hinge mechanism. The results of the finite element analysis were in good agreement with the test results. Parameter analysis indicated that when the longitudinal reinforcement ratio increased, the seismic performance, including the initial stiffness, ultimate bearing capacity, and ductility, increased. As the linear stiffness ratio of the laminated beam to the precast column and the height of the canopy slab increased, the initial stiffness and ultimate bearing capacity improved significantly, whereas the ductility decreased.

Damaged mortise–tenon joint strengthened using an assembled spring–steel hoop based on a design of similar rotational stiffness

The excessive enhancement of rotational stiffness leads to an uneven distribution of rotational stiffness across the entire timber frame. This uneven distribution concentrates the load effect on the strengthened mortise–tenon joints (MJs), causing localized failure in advance. To address this issue, a reversible and non-destructive strengthening method for the damaged MJs is devised, involving the utilization of an assembled spring-steel hoop. The rotational stiffness of a strengthened MJ is derived from the springs that link the steel hoop of the beam and column, resembling the rotational stiffness of an intact MJ. A comparison of the measured moment-rotation curves of various types of MJ reveals that the rotational stiffness similarity necessitates the strengthened MJ's yield moment and ultimate moment, along with the associated rotation angles, to closely resemble those of the intact MJ. Secondly, a design methodology is developed for the assembled spring-steel hoop, which involves determining the parameters of the connecting spring. The comparative analysis of the hysteretic test results on multiple strengthened and intact MJs indicates that the strengthened MJs exhibit rotational stiffness deviations of less than 12.2 % during the elasticity stage and 6.6 % during the plasticity stage, in comparison to the intact MJs. A spring exhibits a lower ultimate extension compared to timber, leading to a maximum discrepancy of 37.5 % in the ductility coefficients between the strengthened MJs and intact MJs. The strengthened and intact MJs display similar patterns of stiffness reduction and energy dissipation progression.

Experimental Study on Seismic Performance of Artificially Simulated Damaged Hoop Head Mortise–Tenon Joints

Experimental Study on Seismic Performance of Artificially Simulated Damaged Hoop Head Mortise–Tenon Joints

Effects of environmental humidity on the gap of mortise-tenon joints: Experimental and numerical investigations

Mortise-tenon (MT) joints play a vital role in the lateral deformability and seismic performance of traditional timber structures. However, moisture exposure can cause shrinkage-induced gaps and then affect the durability of MT joints. Limited knowledge exists on the humidity response of MT joints. To investigate the effect of environmental humidity on the gaps between mortise and tenon, multiple measurements of moisture content (MC) and shrinkage deformation were conducted on straight MT joints that were subjected to humidity variations. Different ambient conditions and exposure levels were taken into account. Three-dimensional numerical models were established to simulate the humidity response of MT joints. Model validation was then performed by comparing the simulation and experimental results in terms of moisture distribution and gaps. On this basis, quantitative analysis was made to reveal the development mechanism and main influence factors of moisture-induced gaps. Results show that straight MT joints are vulnerable to environmental humidity changes. The observed gap is estimated to cause a decrease of up to 23.1% in the initial elastic stiffness. Although only contributed by the shrinkage deformation of tenons, the vertical gap is theoretically larger than the horizontal one which is attributed to a combination of both mortise and tenon. A clear linear relationship is found between the vertical gaps and the MC decrease, with the product of the radial shrinkage coefficient and tenon height as the theoretical ratio. Controlling the moisture exposure is considered the most effective way to reduce moisture-induced gaps in MT joints.

Experimental and numerical studies on influences of wedge reinforcement on seismic performance of loose penetrated mortise-tenon joints

Wooden wedges significantly affect the rotational stiffness and load-bearing capacity of penetrated mortise-tenon joints (PMTJ). To clarify the role of wedges on the seismic performance of loose penetrated mortise-tenon joints, three types of full-scale PMTJs, including reference, loose, and wedge-reinforced joints, were tested under quasi-static loading. The deformation characteristics, hysteresis curves, rotational stiffness degradation behavior, and energy dissipation of PMTJs with wedge were analyzed. Three-dimensional nonlinear finite element models were established to simulate the wedge effects, and the stress states of joint were analyzed. The results indicated that the ultimate bending moment capacity of reference and loose joints was reached when the splitting failure of tenon occurred, while the wedge-reinforced joint reached such capacity when the transverse compression failure occurred at the wedges. The maximum bending moment of PMTJ with a 10 mm gap and a 25 mm gap were 18.3 % and 55.3 % lower than that of reference joint, while maximum bending moments of wedge-reinforced joint with a 10 mm gap and a 25 mm gap were 12.6 % and 17.03 % larger than that of reference joint, respectively. Numerical simulation showed that wooden wedge reduced stress concentration in the tenon and alleviated compression damage of the tenon. Higher load-bearing capacity and rotational stiffness were observed in joints when hardwood wedges were used, compared with that of soft wood. Wedge reinforcement could effectively improve the load-bearing capacity of loose PMTJ. These results yielded valuable data for the performance evaluation and retrofitting of penetrated mortise-tenon joints with wedges in traditional timber structures.

Use of lower tolerance limits for designing chair frames with round-end mortise and tenon joints

ABSTRACT In this study, the reliability of the mortise-tenon (MT) joints was examined experimentally and numerically. The joint strength has been determined empirically and numerically, but the reliability of the joint does not rely on a single asset – mean and standard deviation. The prediction of its strength also refers to a single value in the future population, but tolerance limits are related to a portion of the future population. Therefore, ensuring joint reliability comes into prominence not only for empirical data but also for theoretical and numerical analysis. For this purpose, the moment capacity of the T-shaped MT joints constructed of white oak was determined, and the lower tolerance limits (LTLs) approach was used to construct confidence/proportion (γ/β) levels for reliability. According to the results, the moment capacity of the MT joints was 341 Nm. The LTL values at 0.95/0.95, 0.99/0.95, 0.95/0.99, and 0.99/0.99 γ/β levels were 231, 226, 187 and 181 Nm, respectively. The normal stresses at each γ/β level were calculated based on the moment capacity and tenon sizes and were compared with the finite element method (FEM). Experimental and numerical results varied from 0.3% to 13.4%. Furthermore, a side frame was imposed to a vertical load of 1000 N on the front leg, and the moment of the joint on the side rail to the back post was measured (196 Nm). The side frame was modeled on ABAQUS – FEM software – and subjected to a moment of 196 Nm on the side rail. The theoretical and numerical results of stresses on joints differed from – 4.3% to 5.8%. The study showed that the reliability value is known, and; the joints could be designed by using FEM.

Achieving sustainable and highly efficient wood bonding through synergistic plant root-driven penetration mode with a hyperactive interface

Wood adhesives are widely used in furniture manufacturing, the construction industry, and the fabrication of the internal components of aircraft, cars, and sports equipment. Therefore, the development of wooden adhesives with high stability, strength, and efficiency is a vital research area. Although most studies have focused on improving the bonding properties of adhesives, achieving direct interface control from wood remains a challenge. This study was designed based on the plant root-driven adhesion method to create a hyperactive-interface self-driven regulated wood capable of spreading adhesive into the wood and inducing crosslinking to improve adhesive strength. A multi-poly silicate network structure with multiple reactive sites was formed through the self-polymerization of sodium silicate and crosslinking with dimethylol dihydroxy ethylene urea (DMDHEU) to achieve densified wood and improve the reactivity of the wood surface and interior. Consequently, the environmentally friendly polyvinyl acetate (PVAc) underwent a self-driven bonding process with the wood. These findings indicate that PVAc penetrated the interior of the wood, disrupting the combination of sodium silicate and DMDHEU and grafting onto the reactive sites. This process resulted in a tightly bonded interface connection. Consequently, the shear strength increased from 4.4 to 5.5 MPa, and the wood breaking rate increased from 21.00 % to 45.80 %, representing a 25 % and 118.10 % increase, respectively. Moreover, the tensile strength of the wood in longitudinal joints, transverse joints, miter joints, and mortise–tenon joints was assessed. The results revealed that the sodium silicate/DMDHEU-regulated wood (SS/DDRW) exhibited significantly higher adhesive strength than the original wood (OW). Hence, this bionic design represents a simple and efficient strategy for developing wood adhesives.

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.

Seismic performance of light wood shear wall infilled timber frame structures with openings

To study the seismic performance of wood frame structures filled with light wood shear walls, three full-size single-layer single span wooden frame structures with infill walls were designed and manufactured. The beams and columns were connected by mortise-tenon joints, and quasi-static tests were conducted on the specimens under reversed cyclic load. The failure modes and load-displacement hysteresis performance of structures with door opening infill wall, window opening infill wall, and solid infill wall were investigated. The seismic performance was analyzed using indicators such as strength, ductility, and equivalent viscous damping ratio. The failure modes of light wood frame filling walls were the tearing of sheathing panel and the failure of nail connections. The filled wall with the opening initially exhibited inclined cracks at the corner of the opening, and then they extended to the periphery. Compared with the solid filled wall, the positive and negative bearing capacity of the structure with door opening decreased, and that of the structure with window opening decreased also. Because the specimens with opening in the filled wall were more conducive to the deformation of the structure when the bearing capacity was not significantly reduced, the ductility of the specimen with door opening was the highest.

Experiment and theoretical study on mortise-tenon joints reinforced by support-type viscoelastic damper

This paper proposes the utilization of support-type viscoelastic dampers to enhance the seismic performance of traditional timber mortise-tenon joints. Four viscoelastic dampers and three T-shaped mortise-tenon joints were manufactured, with two dampers designated for performance testing and the remaining two dampers installed on the mortise-tenon joints. Subsequently, cyclic loading tests were carried out on the reinforced mortise-tenon joints and two control mortise-tenon joints. A comparative analysis was conducted on the changes in the moment-rotation hysteresis curve, skeleton curve, stiffness, and energy dissipation capacity before and after joint reinforcement. Based on the observed deformation characteristics of the joints during the tests, a theoretical moment-rotation model for the reinforced mortise-tenon joint was derived and juxtaposed with the experimental results. The study demonstrates that the viscoelastic dampers exhibit stable stiffness and exceptional energy dissipation under cyclic loading. In contrast, the stiffness of the mortise-tenon joints from the control group degrades significantly with increasing rotational deformation, whereas the joints with dampers maintain relatively stable stiffness. The installation of dampers led to a remarkable improvement, with the maximum moment-bearing capacity and average stiffness increasing by 2.3 times and 1.5 times, respectively. The total energy dissipation of the reinforced joints under the same loading reached 2.69 kN·m·rad, representing a 1.8-fold increase compared to the control joints. The calculated results of the theoretical moment-rotation model for the reinforced joints align well with the experimental results, providing a robust theoretical foundation for the application of support-type viscoelastic dampers in strengthening mortise-tenon joints.

A Wooden Pin Reinforcement of Ancient Chinese Wooden Temple: A Case of Daxiong Hall

Post and lintel frame is a prominent architectural structure in Chinese temple architecture, characterized by its wooden construction. Mortise–tenon joints (MTJs) serve as the primary connection method for these wooden structures, employing straight mortise nodes (SMNs) and through-mortise joints (TMNs). This study presents a method that utilizes wooden pins to reinforce MTJs, enhancing the seismic performance of timber frame structures. Finite element (FE) simulation verifies the effectiveness of wooden pins in reinforcing both SMNs and TMNs, leading to improved load-bearing capacity and ductility of the MTJs. Additionally, the study confirms that reinforced nodes help to restrict the displacement changes within the wooden frame. The paper also investigates the optimal distribution of MTJs reinforced by the wooden pins throughout the structure, with the aim of enhancing the wood frame’s seismic performance. The results show the bearing capacity of MJT reinforced with wooden pins is approximately 11.3% higher compared to that of MTJ without reinforcement. The reinforcement of wood pins effectively controls the horizontal displacement of the overall structure of the wooden frame, which is reduced by about 50%–62% compared with the unreinforced wooden frame. The locating the wooden pin-reinforced MTJs in the outer columns and middle layer columns reduces the structural displacement, which is 31.53% in X direction, 5% in Y direction, and 25.86% in Z direction.

Experimental Study on Wooden Pin Reinforcement of the Typical Mortise-Tenon Joints of Ancient Timber Frames

ABSTRACT The ancient timber frames is the precious architectural heritage of China. The seismic performance of mortise tenon joints (MTJ) directly affects the seismic performance of the ancient timber frames. This study presents a method that utilizes wooden pins to reinforce MTJs, enhancing the seismic performance of timber frame structures. The quasi-static test and finite element model were carried out to study the mechanical properties of the MTJ reinforced by the wood pins. From the failure state of the MTJs, it is found that the main deformation is the slip deformation between mortise and tenon. The mutual friction between the mortise and the tenon has a certain energy dissipation and shock absorption effect. The deformation state, stress distribution, stiffness degradation curve, etc. of the MTJ were obtained by finite element model of the MTJ. Additionally, the study confirms that reinforced MTJ can help restrict displacement changes within the wooden frame. The results show the bearing capacity of MJT reinforced with wooden pins is approximately 11.3% higher compared to that of MTJ without reinforcement. The reinforcement of wood pins effectively controls the horizontal displacement of the wooden frame, which is reduced by about 50%–62% compared with the unreinforced wooden frame. The locating the wooden pin-reinforced MTJs in the outer columns and middle layer columns reduces structural displacement, which is 31.53% in X derection, 5% in Y derection, 25.86% in Z derection.

Sequentially coupled thermal-stress analysis of traditional timber mortise-tenon joints with damage

This paper presents the results of the fire resistance of traditional timber mortise-tenon joints with service damage. Static loading and fire resistance tests were conducted with full scale joint specimens. An elastic damage constitutive model was developed for wood subjected to elevated temperature. Sequentially coupled thermal-stress analysis was conducted with consideration of various load ratios, joint looseness, wood decay and initial cracking in the joint areas. The proposed material model and the sequentially coupled thermal-stress analysis results were found to be in good agreement with the test results. It was also found from parametric studies that the fire endurance of a mortise-tenon joint is decreased by 21.6% and 38.5% as a load ratio changes from 0.3 to 0.35 and from 0.3 to 0.4, respectively. A looseness ratio equal to or larger than 0.15 can noticeably accelerate the displacement development, causing nearly 20% drop in the fire endurance, and 42% drop in the coefficient of rotational stiffness after 30 min of fire exposure, compared with those of a damage free joint. A decay induced 50% reduction in the perpendicular to grain compressive strength of wood can lead to a drop of 29% of the joint fire endurance The generated knowledge can be used as reference for fire risk evaluation of traditional timber structures.

Experimental and numerical investigation on collapse performance of wooden drum-towers in southwest China

The drum-tower belongs to the category of towering structures, and the overall collapse is a common accident in such structures. In order to study the anti-collapse performance of drum-towers, this research used the bottom floor of a wooden drum-tower in the southwest China as a prototype, designing and producing a 1/3 scale structural model. The sudden-column-removal (SCR) method was employed to simulate the structural collapse process, observe collapse characteristics, and analyze the dynamic response of the structure. A finite element model was established, and on the basis of verifying its accuracy, a parameter expansion analysis was conducted. The study indicates that the ductility of wooden drum-towers is relatively poor, and the pulling out of mortise- tenon joints in adjacent components in the failure area is a primary factor for the progressive collapse of the structure. Due to the redistribution of internal forces, the load-bearing status of beams in the failure area changes, experiencing tension, bending moment, and torsion simultaneously, leading to the pulling out, compression, and splitting of mortise-tenon joints. After the failure of these joints, the structure undergoes progressive collapse under the influence of gravity. The dimensions of mortise-tenon joints and the friction coefficient have a significant impact on the anti-collapse performance of the structure. Larger dimensions and friction coefficients result in slower structural damage and more stable structural response. Among these factors, increasing the depth of mortise-tenon joints has the most significant effect.