A computer vision-based approach for detecting tenon pull-out damage in ancient timber structures

This paper proposes a meta-model-based parametric Historic Building Information Modelling (HBIM) approach to preserving and renewing traditional timber dwellings, specifically focusing on traditional Bai ethnic residential architecture. The study integrates traditional architectural principles with contemporary digital construction techniques. Traditional Bai dwellings have complex timber structural and spatial characteristics with various components. Results from the application of HBIM demonstrate improved efficiency in documenting and managing structural information, facilitating the maintenance and preservation of heritage buildings. The study concludes that HBIM, supported by parametric and generative design approaches, offers significant advantages in the digital preservation of architectural heritage. This approach not only ensures the structural integrity and historical accuracy of the models but also provides a scalable solution for managing and preserving traditional dwellings in the face of modernization pressures. This research broadens the scope of parametric design within digital construction theory, particularly concerning ancient timber structures. It offers a crucial framework that can inform both future studies and practical efforts in the preservation of heritage buildings.

In order to investigate the seismic performance of damaged ancient timber structures with looseness mortise-tenon joints, the shaking table test of an intact ancient timber structure was carried out. The experimental model’s failure modes, main modal parameters, and dynamic response curves were investigated. In addition, the finite element models (FEMs) with looseness mortise-tennon joints were built by OpenSees, and the natural periods, acceleration, and displacement time history curves of intact FEM and experimental model are compared. Moreover, incremental dynamic analysis (IDA) of damaged models was performed, where the ground peak acceleration (PGA) and maximum inter-story drift ratio θ max are taken as intensity measure (IM) and damage measure (DM) of the motions of the ground, respectively. The seismic fragility of damaged models was studied by probabilistic seismic demand analysis to evaluate the seismic performance of the damaged structures from the perspective of probabilistic.

The semi-rigid mortise-tenon joints in the wooden structures of ancient buildings are often destroyed before beams and columns under major earthquakes, which are the important positions for reinforcement and protection. A new type of shape memory alloy (SMA) preventive reinforcement device is designed, and low-cyclic loading tests are carried out on five reinforced joints and one unreinforced joint. The failure modes, moment-rotation relationship, strength degradation, stiffness degradation, energy dissipation, self–centering ability and deformation capacity of the joints reinforced by SMA strings with different numbers and different pretension strains are studied. A calculation method for bending capacity of straight tenon joints reinforced by SMA strings is established. The results show that the bending capacity of the joints after SMA reinforcement is improved. The maximum bending capacity of the reinforced joint is 1.49 times that of the unreinforced joint. Compared with the unreinforced joint, the strength degradation of the reinforced joints is not serious, which indicates that the SMA strings can still continue to provide the bending capacity for the joints when the rotation is large. The maximum rotational stiffness of the reinforced joint is 2.24 times that of the unreinforced joint. With the increase of the rotation of joints, the energy dissipation of unreinforced joint gradually decreases, however the energy dissipation of reinforced joints increases first and then decreases. At the same rotation, the relative residual deformation decreases with the increase of numbers and of pretension strains of SMA strings, and the self-centering ability is enhanced. The results of research can provide a reference for the preventive conservation of the mortise-tenon joints in ancient timber structures.

ABSTRACTIn order to study the influence of looseness on seismic performance of through-tenon joints, six through-tenon joints specimens in 1:3.2 scale, including one tight-fitted joint and five loose joints, were fabricated according to the Engineering Fabrication Methods of Qing dynasty. The failure modes, mechanical behaviors such as the hysteresis and envelope curves, strength and stiffness degradations, energy dissipation, and deformation of the specimens under low cyclic reversed loading tests were analyzed. Results show that the failure modes of theses joints under positive and negative loadings are bending damage on the big tenon head and tearing damage on the variable cross-section, respectively. The hysteresis curves of joints appear to be anti-Z shape and present typical pinching effect. The greater the degree of looseness is, the more obvious the slippage is. The bending moment, stiffness and energy dissipation of loose joints are lower than those of the tight-fitted joint under the same rotation angle, and the increase in the loose degree cause them to gradually decrease. Meanwhile, the behavior of the through-tenon joints is further simulated by the nonlinear finite element analysis program, and the test results agree well with the numerical analysis results.

According to the investigation on historic structures in Zhaohua Ancient City, there are a total of 210 historic structures in the city, of which the historic timber structures account for 93.8%, namely 197 in total. In this paper, damage degrees of the historic timber structures have been determined, although the timber structures had not considered seismic design when they were built, nearly 60% of the historic timber structures are of relatively minor damage. Besides, based on the analysis on seismic damage of the historic timber structures, the failure modes of the timber structures have been concluded, namely the tenon pullout or tenon break-off, the pillar break-off, the pedestal slip and the retaining wall damage.

Quantitative assessment of the extent of damage to timber structures during the full course of a real fire using the energy equivalence method

The main objective of yoga pose grading is to assess the input yoga pose and compare it to a standard pose in order to provide a quantitative evaluation as a grade. In this paper, a computer vision-based yoga pose grading approach is proposed using contrastive skeleton feature representations. First, the proposed approach extracts human body skeleton keypoints from the input yoga pose image and then feeds their coordinates into a pose feature encoder, which is trained using contrastive triplet examples; finally, a comparison of similar encoded pose features is made. Furthermore, to tackle the inherent challenge of composing contrastive examples in pose feature encoding, this paper proposes a new strategy to use both a coarse triplet example—comprised of an anchor, a positive example from the same category, and a negative example from a different category, and a fine triplet example—comprised of an anchor, a positive example, and a negative example from the same category with different pose qualities. Extensive experiments are conducted using two benchmark datasets to demonstrate the superior performance of the proposed approach.

In recent years, the use of timber as a building material in larger construction applications such as multi-story buildings and bridges has increased. This requires a better understanding of the material to realize such constructions and design them more economically. However, accurate computational simulations of timber structures are challenging due to the complexity and inhomogeneity of this naturally grown material. It exhibits growth inhomogeneities such as knots and fiber deviations, orthotropic material behavior and moisture dependence of almost all physical parameters. Describing the creep response of wood under real climate conditions is particularly difficult. Changes in moisture content, plasticity and viscoelasticity affect moisture-induced stresses and potentially lead to cracks and structural damage. In this paper, we apply a material model that combines time and moisture-dependent behavior with multisurface plasticity to simulate cross-sections of different dimensions over a 14-month climate period. Our findings indicate that considering this long-term behavior has a minor impact on moisture-induced stresses during the drying period. However, during the wetting period, neglecting the time- and moisture-dependent material behavior of wood leads to a significant overestimation of tensile stresses within the cross-section, resulting in unrealistic predictions of wetting-induced fracture. Therefore, simulations during wetting periods require a sophisticated rheological model to properly reproduce the stress field.

Flexural performance of spliced beam connected and reinforced with self-tapping wood screws

Suspended ancient timber structures, characterized by complex construction and unique load-transfer mechanisms, are prone to pronounced dynamic responses under pedestrian walking loads. This study aims to systematically investigate the structural responses from both deterministic and stochastic perspectives. Graded vertical loading tests were conducted to reveal the mechanical behavior and safety redundancy of the structure under pedestrian loads. Based on a stochastic load model, a comprehensive crowd–structure interaction model was developed by incorporating step-frequency synchronization, spatial coherence, and weak crowd–structure coupling effects, enabling accurate prediction of vibration responses. Monte Carlo simulations were employed to evaluate dynamic responses and explore the nonlinear relationship between pedestrian numbers and structural behavior. A parametric prediction model with 95% accuracy was established, allowing reliable response prediction and safety warning. Finally, safety prediction and graded pedestrian control strategies are proposed to support refined protection, intelligent monitoring, and visitor management of such heritage structures.

Effects of inclination on hysteretic behavior of asymmetric ancient timber structures

Optimal design of right-angle viscoelastic dampers for seismic performance of ancient timber structure via improved multi-objective particle swarm algorithm

The majority of existing ancient timber structures have different degrees of damage. The looseness of mortise-tenon joints is a kind of typical damage type. In order to study the influence of looseness on the seismic performance of mortise-tenon joints, six through-tenon joints and six dovetail-tenon joints with scale 1:3.2 were fabricated according to the requirements of the engineering fabrication method of Chinese Qing Dynasty. Each type of joints consisted of one intact joint and five artificial loose joints, and the artificial defect was made to simulate looseness by cutting the tenon sectional dimension. Based on experiments of two types of joints under low-cyclic reversed loading, the seismic behaviors of joints such as failure modes, hysteretic loops and skeleton curves, strength and stiffness degradation, and energy dissipation capacity were studied. Moreover, the comparative analyses of seismic performance between two types of joints were carried out. The variation tendency of seismic behaviors of two types of joints has similarities, and there are some differences due to their different structural styles. The results indicate that squeeze deformation between tenon and mortise of two types of joints occurred. The shape of hysteretic loops of two types of joints is reverse-Z-shape, and the pinching effect of hysteretic loops becomes more obvious with the increase in looseness, among which of through-tenon joints is more obvious than that of dovetail-tenon joints. The carrying capacity, stiffness, and energy dissipation capacity of loose joints are significantly lower than that of the intact one, and the energy dissipation capacity of dovetail-tenon joints is better than that of through-tenon joints. The rotation angles of two types of joints can reach 0.12 rad, and the loose joints still have great deformation capacity.

To evaluate the impact of long‐term corrosion on the seismic performance of ancient wooden structures, a simplified analysis model of an intact ancient wooden structure was established using, the OpenSees finite element software, considering column rocking, mortise–tenon joints, Dougong joints, and the role of plate. The accuracy of the model was verified by comparing it with the results of the shaking table test. A residual mechanical performance model of mortise–tenon joints and Dougong joints in ancient wooden structures under long‐term corrosion was established. The impact of node performance degradation under long‐term corrosion on the seismic response and structural vulnerability was studied. The study indicates, that the nonlinear time‐history analysis values of the structure are consistent with the experimental values, with a peak displacement error within 10%, indicating a small error. When the performance degradation rate of the Dougong joints is less than 15.8%, the peak displacement increase rate of the structure is less than 5%. However, when the performance degradation rate of the mortise–tenon joints is 5.7%, the peak displacement increase rate of the structure is greater than 16.32%. Under horizontal seismic action, the main factor affecting the lateral displacement of the structure is the performance of the mortise–tenon joints in the column frame layer. The performance degradation of the mortise–tenon joints has a significant impact on the performance of the structure under minor earthquakes, significantly increasing the probability of slight damage and moderate damage. However, under major earthquakes, the impact on the structural performance is relatively small, with a slight increase in the probability of severe damage and collapse.

This contribution describes the development and the experimental investigation of innovative enhanced light weight timber frame buildings, which can be a very efficient structural solution for wooden multistory buildings. This development concepts comprise high-performance timber frame walls, also named “powerwalls” with variable arrangement of sheathing planes and dissipative anchorings at the base of the timber buildings, which can limit damages of the timber structure and can be replaced after a significant earthquake. In order to testify the improved performance of the developed elements in the context of a real building, a full scale two storey building core was designed, erected (in the laboratory) and tested experimentally for its seismic performance. The results of the tests are presented. Observations during the test also reveal some aspects of the design and detailing which need consideration in the application of the timber walls in the context of the complete building.