To clarify the effect of high stylobate on the seismic performance of traditional timber structures, two 1/5-scaled models (Model 1 and Model 2) were designed, fabricated, and tested on a shaking table. Model 1 represented a typical traditional timber structure with a double hip-and-gable roof, while Model 2 was identical except for the inclusion of a high stylobate. A series of earthquake excitations with increasing intensities were applied, and the failure patterns and dynamic responses of both models were systematically measured and evaluated. The results show that the first two natural frequencies of the two models were comparable, but the dynamic interaction between the high stylobate and the upper timber structure led to the identification of additional higher-order modes. Compared with Model 1, Model 2 exhibited noticeably larger displacement response, inter-story drift, acceleration response, and story shear in the upper timber structure. Additionally, damage assessment based on inter-story stiffness and energy dissipation further indicates that the dynamic interaction between the high stylobate and the upper timber structure led to a pronounced increase in seismic damage of the upper timber structure. These findings demonstrate that the high stylobate plays a critical role in modifying the dynamic characteristics and seismic response of palace-type timber structures. Neglecting this dynamic interaction in seismic analyses may result in substantial underestimation of seismic demands and misjudgment of structural safety.

This study presents a pilot experimental and modelling investigation of the cyclic response of ancient brick masonry walls bonded with loess earthen-mortar. Five wall specimens without replicates were designed using a one-factor-at-a-time scheme to examine preliminary trends associated with mortar-joint thicknesses of 2, 6, and 10 mm and water-to-soil ratios of 0.25, 0.30, and 0.35. Quasi-static reversed cyclic loading tests were conducted, while Digital Image Correlation (DIC) was used qualitatively to trace the within-specimen evolution of strain localization and to examine differences in its spatial pattern and location among the specimens. Within the tested series, the reduction in joint thickness from 10 mm to 2 mm was accompanied by a 10.68% reduction in peak load-bearing capacity (66.17–59.10 kN), a 27.42% reduction in terminal displacement (5.525–4.01 mm), and a 49.24% reduction in cumulative energy dissipated up to test termination. Increasing the water-to-soil ratio from 0.25 to 0.35 was accompanied by a 12.09% reduction in peak load (69.83–61.39 kN). A semi-empirical trilinear restoring force model incorporating cyclic stiffness and strength degradation was subsequently calibrated. For the calibration specimens, the model reproduced the principal features of the measured hysteretic response, with a mean relative deviation of 5.7% for cumulative energy dissipation. The results provide a preliminary experimental and modelling basis for further investigation of heritage masonry constructed with similar materials.

This study systematically investigates the mechanical behavior of loess earthen-mortar ancient brick masonry through uniaxial compression tests, with the aim of characterizing its mechanical response and establishing a damage constitutive model. X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) analyses were employed to validate the mineralogical consistency between the replicated materials and the original samples from the ancient pagoda. Subsequently, masonry specimens with varying earthen mortar joint thicknesses and mortar strengths were fabricated, and uniaxial compression tests were conducted to analyze the influence of joint thickness and water-to-soil ratio on the compressive strength, deformability, and failure modes of the masonry. The results indicate that a decrease in mortar joint thickness significantly reduces both the peak bearing capacity (by 17.64%) and peak strain (by 18.73%) of the masonry, whereas an increase in the water-to-soil ratio leads to reduced mortar strength, thereby significantly weakening the bearing capacity of the masonry (by 19.8%). Furthermore, a thickness-dependent unified damage constitutive model was established based on the two-parameter Weibull distribution. Furthermore, an empirical formula for predicting the compressive strength of such masonry, incorporating the effect of joint thickness, is proposed and validated against test data. These findings provide a solid experimental basis and theoretical support for the mechanical assessment, numerical modeling, and restoration strategies of ancient brick masonry structures bonded with loess earthen-mortar.

This study systematically investigates the compression-shear behavior and failure mechanisms of traditional brick masonry with loess earthen mortar through experimental research, theoretical analysis, and numerical simulation. The effects of water-soil ratio, mortar joint thickness, and lateral pressure on interfacial shear strength and slip characteristics were systematically evaluated. The results indicate that the shear strength is dominated by the friction mechanism and shows a significant positive correlation with lateral pressure (Spearman's r = 0.90). Conversely, Scanning Electron Microscope (SEM) analysis confirms that an increase in the water-soil ratio leads to the formation of a loose, porous microstructure in the mortar, thereby inducing strength degradation. Increasing the mortar joint thickness from 2 mm to 10 mm leads to an average enhancement in shear strength of approximately 9.52%, indicating that thicker mortar joints facilitate better stress distribution and load transfer at the brick-mortar interface. Based on the experimental data, a full-range piecewise damage constitutive model integrating the Weibull distribution and a rational fraction function was established, showing a high correlation with the experimental results (R-2 > 0.94). Furthermore, a modified shear strength calculation formula incorporating a normalized thickness correction coefficient g(t) was proposed, with a maximum error of 10.24% between calculated and predicted values. Finite element analysis using Cohesive interface elements reproduced failure mode and validated the experimental conclusions. This research provides essential theoretical support for the safety assessment and restoration of historical masonry structures with loess earthen mortar and holds significant engineering value.

In situ dynamic tests were conducted on Caiyunjian Tower to investigate the influence of a high stylobate on its dynamic characteristics and seismic response through time–domain and frequency–domain methods. Finite element models were developed for Caiyunjian Tower (wooden structure and platform) and the overall structure including the high stylobate. Subsequently, models were subjected to El Centro, Taft, and Lanzhou waves at varying amplitudes. The seismic response results indicate that the overall structure model exhibits a low natural vibration frequency with closely spaced modal frequencies. As the peak seismic wave acceleration increases, both models exhibit increased acceleration, displacement, and shear responses. The Caiyunjian Tower model shows greater sensitivity to the El Centro wave, whereas the overall structure model is more responsive to the Taft wave. Under seismic waves with identical peak acceleration, the overall structure model exhibits greater dynamic responses than the Caiyunjian Tower model. The high stylobate minimally affects the lower-order frequencies of the upper structure but significantly influences the higher-order frequencies. Therefore, the high stylobate has an adverse influence on the seismic behavior of Caiyunjian Tower.

In order to study the seismic performance of a heritage timber-frame structure with a single circle of pillars and double pyramidal roofs, the Wulong Altar in Xi'an Xingqing Palace Park was taken as an example, in-situ dynamic tests were carried out. The modal of the structure was analyzed by combining the peak picking method and the random subspace method. The finite element (FE) model of the wooden structure was established for dynamic response and seismic fragility analyses. The results show that the 1st-6th natural frequencies are 1.975, 2.150, 2.841, 3.427, 4.654 and 5.363 Hz, respectively. The first 6 damping ratios are 3.3 %, 2.1 %, 6.3 %, 4.1 %, 3.8 % and 3.3 %, respectively. The upper story of the Dougong bracket and roof beams plays a greater role in seismic reduction, and the lateral stiffness of the lower structural story is lower. The PISDs of the lower and upper structural stores are 1/83 and 1/87, respectively. The structure is susceptible to transition from basic intactness to minor damage, and the likelihood of the structure undergoing a transition from moderate to severe damage is larger. The minor damage includes slight inclination of the structure, slight slips of Dougong brackets and pullout of the tenon. The moderate damage includes larger inclination of the structure, larger slips of Dougong brackets, larger pull-out and split of the tenon. And the severe damage can be described as obvious inclination of timber frames, more obvious splits and slips of Dougong brackets, largest pull-out and split of the tenon. The structure maintains a high level of resistance to collapse when the PGA exceeds 1000 cm/s2.

ABSTRACT In order to study the dynamic characteristics and seismic performance of the hybrid brick‐concrete and timber (HBCT) structure, an in situ dynamic characteristic test was carried out, and peak picking method was used to calculate natural frequencies, damping ratios, and vibration modes. Considering semi‐rigid mechanical characteristics, a finite element model of the hybrid structure was established, and the calculation results agreed well with the test results. Kobe, El Centro and an artificial ground motion were input for displacement and acceleration response analysis. A set of fifteen ground motion records were selected, and incremental dynamic analysis and seismic fragility analysis were conducted. Results show that the first and second natural frequencies of the HBCT structure are 4.327 and 4.375 Hz, and the vibration modes are translation in the east–west direction and in the north–south direction, respectively. Taking the Kobe ground motion as an example, the maximum displacement of the pillar top of the second‐floor timber structure is 6.12 times that of the pillar top of the first‐floor brick‐concrete structure. The peak inter‐structural layer drift of 1/155 is less than the standard limit. Dynamic coefficients of the overall structure are less than 1, which indicates that the HBCT structure exhibits good shock absorption performance. The performance at different seismic intensities is in accordance with the “Three‐level and Two‐stage Seismic Fortification Goals,” which means no damage under minor earthquake, repairable damage under moderate earthquake, and no collapse under large earthquake.

Restoring force models play a crucial role in characterizing the nonlinear mechanical behavior of traditional timber joints. This study develops the analytical restoring force models for three key traditional joint types, including Column-Top and Column-Foot joints, typical Mortise-Tenon joints, and Dou-Gong joints, with explicit consideration of plastic deformation damage. The proposed models incorporate multiphase backbone curves and damage-dependent hysteretic rules, which can capture essential joint characteristics by considering the geometrical and mechanical properties of each joint type. The backbone curves characterize the nonlinear load-deformation response, while the hysteretic rules account for stiffness degradation caused by accumulated plastic deformation. Furthermore, a dual-level composite modeling approach using ABAQUS connector elements is proposed. This method eliminates the need for secondary development by employing parallel-connected elements with distinct connector behaviors to simulate complex hysteretic responses. Experimental validation confirms that the models can reflect nonlinear stiffness evolution, pinching behavior, and energy dissipation mechanisms of the joints. These developments provide both fundamental understanding of joint mechanics and practical tools for seismic response analysis of ancient timber structures.

This study aims to investigate the bond behavior at earthen mortar–brick interfaces in historic masonry structures. To that end, a series of combined compression–shear tests were conducted to systematically assess the influence of varying water–soil ratios and applied lateral compression on interfacial bond behavior. A fully decoupled microscopic finite element (FE) framework employing cohesive elements was developed to simulate the bond strength of earthen mortar–brick interfaces and validated using Spearman correlation analysis. The results indicate that increasing lateral compression markedly enhances both the peak displacement and shear strength, although it also reduces inter-specimen correlation by 18%. Notably, even under high lateral compression, the finite element predictions maintained a strong correlation with experimental data (R = 0.86), with a maximum deviation of less than 5%, demonstrating the model’s capability to accurately simulate the bond behavior of loess earthen mortar in masonry. These findings provide essential data and a robust computational framework for the preventive conservation of historic masonry structures.

This paper explores the seismic behavior of the corner Dou-Gong (DG) bracket in ancient Chinese timber buildings. A full-scaled DG was tested by the pseudo-static test to study the failure mode, hysteretic characteristic, stiffness and strength degradation, energy dissipation and deformation capacity of the entire DG as well as the displacement of the DG components. A numerical model verified by the test was established to analyze the stress distribution of the DG and components. Parameter analysis of loading direction, wood grain direction, vertical load, and friction coefficient was also conducted. Results indicate that the positive bearing capacity, stiffness, and deformation capacity of the DG are inferior to the negative, whereas the energy dissipation capacity is excellent. The component's rotation displacement in the overhanging and oblique 45° direction rises with the loading process. The higher the component, the larger the rotation displacement, but the component's sliding displacement does not follow this law. From top to bottom of the DG, the proportion of the component's rotation displacement and sliding displacement decreases and increases respectively. The larger amount of the corner DG components makes its seismic behavior better than the Pingshenke DG. The DG exhibits its maximum positive load in the width direction and the minimum negative load in the oblique 45° direction. The grain direction of Da-Dou and Pingban-Fang can affect the bearing capacity of the DG. Increasing vertical load and friction coefficient enhances the bearing capacity of the DG.

This paper presents the dynamic characteristics and seismic performance of the Chen Xiang Pavilion in Xi’an and the influence of the lower stylobate on the dynamic response of the upper wooden structure. An in situ dynamic test was conducted under ambient vibration to detect the natural frequencies and vibration modes of the structure. Three numerical models, including the upper wooden structure, the lower stylobate, and the whole structure (wooden structure and stylobate), were established. Dynamic characteristic and seismic response analyses were performed on the calculated models to investigate the influence of the lower stylobate on the dynamic response of the upper wooden structure. The simulation results indicated that the lower stylobate significantly affected the dynamic characteristics of the upper wooden structure above the third order. The seismic responses of the upper wooden structure were amplified because of the lower stylobate. Under different excitations, the displacement response of the whole structure was up to 1.99 times relative to the upper wooden structure, and the structural shear forces were increased by 15.3%. The dynamic amplification coefficient was magnified from 0.742~0.948 to 1.024~1.776. The Chen Xiang Pavilion has a good energy dissipation capacity, but the lower stylobate is unfavorable for its earthquake resistance.

This paper is focused on the mechanical performance of the Dou-Gong bracket at the corner under vertical load. A full-scaled specimen was tested under the static compressive load. The load-displacement curves, load distribution law and displacement of components were discussed. A finite element model was established and validated with test results. The deformation and stress of the whole Dou-Gong bracket and main components were analyzed, and the influence of the wood properties and friction coefficients was studied. The results show that there are four stages in the load-displacement curve and the plastic stiffness is 76.36% lower than that in the elastic stage. The components in the oblique 45 degrees direction mainly transfer the force, while the load distribution ratios in the width and oblique 45 degrees directions of the lower layer is closer to 1. The displacements of the components in oblique 45 degrees direction in the No. 2 and No. 3 layers are smaller than those of the components in width direction. With the increase of the compressive strength, the elastic moduli in the radial direction and the friction coefficients, the stiffness in the plastic stage increases and the maximum displacement decreases. However, the compressive strength and the elastic moduli in the longitudinal direction have little effect on the load-displacement curves.

The distinctive structural construction in the overhanging and width directions of Dou-Gong (DG) bracket in ancient timber buildings results in different seismic performances of the DG. To study the effect of loading direction on the seismic behaviors of the DG bracket, the pseudo-static tests are conducted on two Dou-Gong brackets on column in the overhanging direction (DG-1) and width direction (DG-2), respectively. The failure mode, hysteretic behavior, skeleton curve, stiffness degradation, and energy dissipation capacity of the DG are obtained. Besides, the rotational, sliding, and bulging displacements as well as their proportions of DG component’s horizontal displacement are analyzed. In addition, a theoretical model was proposed to calculate the horizontal load of the DG. Results show that the failure modes of DG-1 and DG-2 are rotation and relative slip of DG components, broken of Xiao 1, and embedment of Flat-Beam. DG-1 has a superior bearing capacity, initial stiffness, and energy dissipation capacity compared with DG-2. However, both DGs exhibit good deformation ability and obvious stiffness degradation. The horizontal displacement component of DG-1 increases first and then tends to be stable with the loading displacement, while the component displacement of DG-2 increases gradually. The rotational and sliding displacements of the DG components are significantly larger than the bulging displacement. The higher the DG components, the larger the rotational displacement. The proportion of the component’s sliding displacement is larger than the rotational displacement for DG-1, while the proportion for DG-2 is opposite. The theoretical model for the horizontal load can effectively calculate the bearing capacity of DG brackets.

为研究单围柱重檐攒尖木结构的动力特性及地震响应,以西安兴庆宫五龙坛木结构建筑为例,对其进行原位动力试验,采用峰值拾取法与随机子空间法,分析了结构的前 6 阶自振频率、空间振型及阻尼比.考虑单围柱、榫卯连接、斗栱铺作、抹角梁架空间构造的特征,建立了单围柱重檐攒尖木结构有限元分析模型,计算得到结构的前 6 阶频率、振型及五龙坛原位试验结果吻合较好.结果表明:单围柱重檐攒尖木结构一阶自振频率在1.924～1.975 Hz之间,二阶自振频率在 2.146～2.15 Hz之间,一、二阶振型分别为南北平动与东西平动;三阶自振频率在 2.775～2.841 Hz之间,振型为扭转振动.输入不同幅值的El Centro波、Taft波及兰州波地震激励,在罕遇地震作用下底层最大层间位移角为 1/83,童柱层最大层间位移角为 1/87.

To investigate the seismic behavior of the inclined Dou-Gong (DG) brackets, three full-scaled Dou-Gong bracket between columns with different inclinations along the width direction were tested under the pseudo-static test. The failure mode, hysteretic characteristic, stiffness degradation, deformation and energy dissipation capacity as well as the deformation modes of DG were discussed. Besides, numerical analysis of DG’s stress distribution and seismic behavior of DG brackets inclined in the overhanging direction was also studied. Parameter analysis was conducted to study the effect of frictional coefficient, vertical load and wood properties on the bearing capacity of DG. The results demonstrated that the DG bracket rotates as a whole and the relative slip of Da-Dou and Pingban-Fang leads to the shear damage of Mantou-tenon when DG failed. As the inclination in width and overhanging direction increases, the positive bearing capacity and lateral stiffness decrease, while the negative direction increases. The DG’s negative deformation ability is better than the positive direction and the larger the inclination, the stronger the deformation capacity. However, inclination reduces the energy dissipation capacity of DG. Rotation deformation is the main deformation mode of the DG bracket. Increasing the frictional coefficient, vertical load and compressive strength along the grain improves the bearing capacity of the DG, but the bearing capacity is slightly affected by the elastic modules along the grain. The research results can provide a scientific basis for the performance evaluation and repair protection of inclined DG brackets.

In order to study the seismic performance of full-scale straight-tenon joint, a precise finite element analysis has been conducted based on the orthotropic constitutive relationship of wood and a modified Coulomb friction model. The hysteretic and skeleton curve, stiffness degradation, energy dissipation capacity, deformation capacity, and stress distribution are obtained through the finite element model and test results are utilized for calibration. Besides, parameter analyses considering size effect, friction coefficients, material properties, and axial loads on the column are performed. Results demonstrate that the precise finite element model can well reflect the seismic behavior of the straight-tenon joints. The hysteretic curves in simulation and test results are both anti-"Z" types with an obvious pinching effect. The initial stiffness is large, and stiffness degrades obviously with the increment of rotation. At the same rotation, the larger the scale of the model is, the greater moments and stiffness of the joints are, but the relationship is not linear. Friction coefficients and compressive strength in the parallel-to-grain direction mainly influence flexural capacity of the joint but have little effect on rotational stiffness. The rotational stiffness and flexural capacity are slightly affected by elastic moduli and axial loads.

BackgroundThe COVID-19 pandemic necessitated increased synchronous distance education (SDE) in graduate medical education, presenting challenges for Quality Improvement and Patient Safety (QIPS) best practices, which call for integration with daily clinical care and investigation of real patient safety events.ObjectiveTo evaluate educational outcomes for QIPS training after conversion of a mature, in-person curriculum to SDE.Methods68 postgraduate year (PGY)-1 residents were surveyed before and after the SDE Culture of Patient Safety training in June 2020, and 59 PGY-2s were administered the Quality Improvement Knowledge Application Tool-Revised (QIKAT-R) before and after the SDE QIPS seminar series in July–August 2020. Values before and after training were compared using sign tests for matched pairs (PGY-1) and Wilcoxon signed-rank tests (PGY-2).Results100% (68 of 68) of PGY-1s and 46% (27 of 59) of PGY-2s completed precourse and postcourse surveys. Before the course, 55 PGY-1s (81%) strongly agreed that submitting patient safety event reports are a physician’s responsibility, and 63 (93%) did so after (15% increase, p=0.004). For PGY-2s, the median composite QIKAT-R score was 17 (IQR 14.5–20) before and 22.5 (IQR 20–24.5) after the seminars, with a median difference of 4.5 (IQR 1.5–7), a 32% increase in QIPS competency (p=0.001).ConclusionsPatient safety attitudes and quality improvement knowledge increased after SDE QIPS training at comparable levels to previously published results for in-person training, supporting SDE use in future hybrid curricula to optimise educational value and reach.

A looseness is typical damage for mortise-tenon joints in ancient timber structures. The tenon of the loose dovetail-tenon joints is prone to be pulled out, leading to joint failure in the earthquake. Hence, it is necessary to investigate the seismic performance and deformation damage of loose dovetail-tenon joints. This study conducts pseudo-static and acoustic emission (AE) tests on three full-scaled dovetail-tenon joints to determine the four stress stages of each joint, including slight damage, medium damage, severe damage, and nearly failure. It examines the hysteretic and skeleton curve, stiffness and strength degradation, energy dissipation performance, and the variation raw of the amount of tenon pulled out at each stage. The deformation damage mode, damage degree, and damage evolution equation of the joint at each stage are obtained based on the AE characteristic parameters measured at each stage. The results indicate that as the rotation angle increases, each joint's stiffness and energy dissipation capacity decrease, while the joint bending moment rises and then reduces, and the amount of tenon pulled out increases. The greater the degree of looseness, the lower the bearing capacity of each joint, and the more pronounced the degradation of stiffness and strength. At each stage, the maximum decrease of initial stiffness is 85.75%, and the maximum amount of tenon pulled out is 93 mm. The failure modes of joints are mainly tenon pulled out failure, and extrusion deformation greatly influences the tenon pulled out failure. As the degree of looseness grows, joints are more prone to severe deformation damage under large rotation angles. At the slight and medium stages, the joints primarily suffer from tensile damage of material, but at the severe damage and nearly failure stage, they mainly suffer from shear damage of material. The damage value of each joint increases with the relative stress ratio, and looseness significantly impacts the damage degree of the joint.

To assess the seismic performance of a traditional Chinese palace-style timber structure, an extended discrete element method (EDEM) model has been established. The model has been applied to analyze a single-story and five-bay timber-frame palace architecture, where sliding isolation of the column foot, semi-rigid connections of mortise and tenon joints, and damping characteristics of bracket sets (known as Dougong in Chinese) have been considered. The study investigates the dynamic characteristics, seismic responses, and structural vulnerabilities of the palace building. Results show that an error of the natural frequency between the EDEM model and results from code-recommended empirical formulas is only 6.88%, highlighting the rationality of the EDEM model. Furthermore, the relative displacement response of each position increases with the increment of inputting ac-celeration of seismic waves. The inter-structural layer drift of the column-beam frame is the largest and that of the roof truss is smaller, while Dougongs are the smallest. The likelihood of moderate damage is highest during a small earthquake, while the structure is prone to severe damage under a medium earthquake, The structure is susceptible to collapse under a large earthquake.