The discrete element method (DEM) is an effective approach for simulating seismic cracking and damage processes in ancient masonry pagodas. Accurate representation of masonry behavior and dynamic fracture characteristics requires a reasonable determination of contact parameters between block elements. To address this, a contact parameter selection method for the model based on the physical properties of materials ( α p method) is proposed, incorporating mechanical property tests of masonry under different stress states and referring to the shaking table test results of the Xuanzang Pagoda model in China. It is applied to analyze block interface shear displacements, displacement time histories at monitoring points, and peak displacements of the pagoda model under different seismic conditions. The numerical results are compared with both the elastic theory-based method ( α e method) and experimental measurements. Findings indicate that the α p method provides a more reasonable simulation of the dynamic effects of the pagoda model and the dynamic transmission behavior of the internal infill. Under strong seismic excitation, the error between the predicted dynamic response of the pagoda and the shaking table test results is only 16.3%, which is reduced by 50% compared with the α e method. This approach more effectively captures material deformation and the typical characteristics of seismic damage evolution in pagodas. This research offers a useful reference for discrete element simulations of failure modes and seismic mechanisms in historic masonry structures.

This paper proposes a sleeve-type fully bolted beam-column joint to improve the assembly efficiency of prefabricated reinforced concrete (RC) frame structures. Low-cycle cyclic loading tests were conducted on four connection configurations. The results indicate that, unlike the flexural failure mode observed in cast-in-place joints, the proposed prefabricated joints gradually exhibited a flexure-shear failure mode with increasing connection stiffness. Compared with the cast-in-place joint, the proposed joint showed significantly improved energy dissipation capacity, with the yield load, peak load, and ductility coefficient increasing by 85%, 43%, and 72%, respectively. The sectional stiffness ratio K of the connection region was identified as the key parameter influencing the hysteretic behavior of the joint. When K≤1.48, rapid post-peak degradation occurred; therefore, a recommended value of approximately K = 1.55 is suggested. In addition, the bearing capacity increased by approximately 10%~15% for every 100 mm increase in the connection region length. Considering both economic efficiency and bolt arrangement requirements, the ratio between the sleeve length and beam section height is recommended to be within 0.9~1.05. Moreover, stress concentration was observed in the connection seam region, and the peak stress could be reduced by more than 70% through the adoption of stress-transition steel plates. Finally, based on a trilinear model, a moment-rotation relationship for the proposed joint was established, providing a basis for theoretical analysis and simplified design.

To enable the quantitative evaluation of seismic collapse severity in historic masonry pagodas, this study proposes a dual-parameter damage index based on the Area Loss Ratio (ALR) and Residual Height Ratio (RHR). Seven representative pagodas are modeled using a three-dimensional discrete element method, in which key structural parameters, including internal infill condition, height-width ratio, and opening ratio, are systematically considered. Nonlinear dynamic analyses are conducted under multiple ground motions corresponding to frequent earthquake (PGA = 0.07 g) and rare earthquake (PGA = 0.40 g) to investigate the progressive collapse mechanisms. The results indicate that internal infill significantly enhances global stiffness and reduces seismic responses, while increases in height-width ratio and opening ratio lead to amplified displacement demand and higher collapse susceptibility. Under rare earthquakes, hollow-core and fully opening configurations exhibit pronounced block detachment and partial collapse, with ALR values reaching 10

Reinforced concrete (RC) columns may develop defects due to long-term material degradation or construction deficiencies such as honeycombing and voids, which substantially reduce their load-bearing performance. To address this issue, defective zone replacement using cement-based grouting material (CGM) has been proposed as an effective strengthening technique. In this study, nine axial compression tests were carried out to investigate the failure characteristics, load-displacement responses, strain distribution, and stiffness degradation of RC columns. The effects of varying defective zone replacement thicknesses and locations on the axial compression performance were experimentally evaluated, whereas numerical simulations were conducted to further examine the influence of replacement thickness, grout strength, and defective concrete strength on ductility, load-bearing capacity, and energy dissipation capacity. The results demonstrate that replacing defective concrete with CGM effectively mitigates stiffness degradation in strengthened columns during the plastic stage. Columns strengthened at the lower defective region exhibit higher recovery efficiency in axial load-bearing capacity compared to those strengthened at the midheight defective region. Among the parameters investigated, CGM replacement thickness is identified as the most significant factor influencing strengthening effectiveness. As the replacement thickness increases, the axial compressive bearing capacity and energy dissipation capacity of the strengthened columns improve by approximately 39.9% and 74.8%, respectively, whereas ductility decreases by about 11.3%. Furthermore, after strengthening, the region of high-stress concentration shifts from the defective zone to the intact concrete zone. It is recommended that the strength of the grouting material should not exceed 2.5 times that of the original concrete, and the cross-sectional replacement ratio should be limited to no more than 90%. Based on both experimental and numerical findings, a calculation method for the axial compressive bearing capacity of RC short columns is proposed, incorporating the lateral confinement effect of the outer grouting material on the defective concrete. The predicted results show good agreement with the experimental data.

Seven discrete-element models (R0, C1, C2, D1, D2, T1 T2) of ancient masonry pagodas were developed to study the seismic response differences caused by structural configuration. The models were based on the architectural style of the Xuanzang Pagoda in China. Height-width ratio, opening ratio, and infill materials were selected as control variables. Site-specific ground motions were used to analyze seismic damage patterns and compare the dynamic responses. Considering cumulative damage, a block-loss ratio was introduced to quantify collapse severity under sequential earthquakes. The results show that Model C1, which has the smallest slenderness ratio, has the highest fundamental frequency of 2.83 Hz. Model T1, which uses masonry infill, has the highest tenthorder frequency of 15.24 Hz. Under seismic loading, the high-slenderness Model C2 displays a transverse displacement of 151.75 cm, along with the largest standard deviation and coefficient of variation, indicating strong sensitivity to ground motion and significant global deformation. Under the repeated earthquakes, Model T2, which has no internal infill, reaches a lateral drift of 1.63 m and a block-loss ratio of 51.15%. These results show that infill materials play a key role in the seismic collapse of masonry pagodas. The findings provide valuable reference for selecting priority protection targets and assessing seismic performance.

Abstract This study examined the axial compressive behavior of deficient strength reinforced concrete (DSRC) columns with local defects strengthened using cementitious grouting materials, based on axial compression tests and numerical simulations of nine reinforced concrete specimens. The effects of defect location and grout thickness on compressive performance were evaluated. The results show that, after grouting, local compressive failure still initiated in lower‐strength regions along the column height under axial loading. The ultimate bearing capacity of strengthened specimens increased by up to 35.4%. Grout strengthening effectively reduced cracking in defective regions and delayed reinforcement yielding. However, strengthening exhibited boundary effects, and the recovery of bearing capacity was more sensitive to grout replacement thickness, while defect location had a limited influence on the ultimate capacity. Considering the lateral confinement provided by grout and stirrups, a calculation method for the axial bearing capacity of locally strengthened DSRC columns was proposed. The predicted results showed good agreement with the test data.

This study investigates the seismic performance of deficient-strength reinforced concrete (DSRC) columns strengthened by replacement with cementitious grouting material (CGM). Nine specimens were tested under cyclic loading, including standard, DSRC, and corresponding CGM replacement columns. Additionally, a fiber model built in OpenSees was used to study the effects of defect locations and replacement thicknesses on the seismic performance of strengthened DSRC columns. Parameters such as failure mode, hysteresis, skeleton curves, ductility, energy dissipation, and stiffness degradation were analyzed. All specimens exhibited flexural failure. Middle-defect columns developed cracks more rapidly and extensively than bottom-defect columns. With increasing replacement thickness, both initial cracking and final failure were delayed, and energy dissipation was significantly enhanced. The cumulative energy dissipation of the middle- and bottom-defect columns increased by up to 63% and 106%, respectively. The strengthening effect of middle-defect columns was slightly lower than that of bottom-defect columns. A method was proposed to predict the flexural capacity of the cementitious grouting material-concrete core (CGM-CC) section, which showed good agreement with experimental results. An optimal sectional replacement ratio of 60%-80% for middle-defect columns and 50%-70% for bottom-defect columns is recommended.

The replacement of locally defective concrete with high-strength cementitious grouting material (CGM) is an effective method for the repair and strengthening of engineering structures. To investigate the seismic performance of reinforced concrete (RC) columns strengthened by this method, low-cyclic loading tests were conducted on nine specimens, including defective columns, control column, and repaired columns. The failure characteristics and load-displacement responses were examined, and finite element models were established to evaluate the effects of defect location, replacement thickness, axial compression ratio, reinforcement yield strength, and defect height. The results show that locally defective columns exhibit reduced seismic performance, with insufficient load-carrying and deformation capacities. Defects at the column base are most detrimental to the development of the plastic hinge region, typically leading to premature concrete crushing at the base. After replacement-based strengthening, crack development is restrained, the concrete crushing and spalling zone at the base is reduced, and ductility is improved. The strengthening effect depends on the defect location, and replacement at the column base is more effective than that at the mid-height region. In addition, increasing the axial compression ratio enhances the peak load capacity but slightly reduces ductility, whereas increasing the reinforcement yield strength has little influence on seismic performance. When the replacement height at the column base exceeds half the column height, the strengthening effect tends to stabilize. Based on the experimental and numerical results, a recommended formula for replacement thickness were proposed using the energy dissipation recovery index, providing a reference for the design of replacement-based strengthening for defective RC columns.

The discrete element method is widely used to simulate the seismic response of ancient masonry pagodas. However, the influence of rigid block size on the reliability of seismic damage prediction remains unclear. In this study, the effects of rigid block scale on the seismic response and damage evolution of ancient masonry pagodas are numerically investigated. A reduced-scale pagoda model validated through shaking table tests is adopted as the benchmark. Three discrete element models with block volume ratios of 1:1, 4:1, and 8:1 are established to simulate the dynamic response under seismic loading. The damage evolution processes are compared to evaluate the influence of the computational unit size on the seismic damage assessment. The results show that increasing the rigid block size leads to higher damage propagation rates and larger damaged areas. The computational time step increases with increasing block size, whereas the numerical accuracy decreases as the block size increases. A decision-oriented evaluation based on a utility function indicates that large-scale block models are suitable for capturing global collapse behaviour, small-scale block models effectively reproduce localized damage, and medium-scale block models achieve a favourable balance between accuracy and efficiency for seismic performance assessment. These findings provide practical guidance for selecting appropriate block scales in discrete element method-based seismic analyses of ancient masonry pagodas.

In this paper, a new RC column reinforcement method of spatial special-shaped lattice steel structure combined with prestressed reinforcement technology is proposed to replace the traditional angle steel-encased reinforcement method. Six specimens with different reinforcement forms and prestress levels were designed. The hysteretic behavior, load-displacement relationship, stiffness change and failure mode of each specimen were analyzed by low cyclic loading test. The results show that the peak bearing capacity, yield stiffness and displacement ductility coefficient of angle steel reinforced columns are increased by 7.03 %, 15.2 % and 28.46 % respectively compared with those of unreinforced ordinary columns, while those of prestressed lattice steel reinforced columns with appropriate size are increased by 63.74 %, 39.1 % and 86.45 % respectively, showing good reinforcement effect. And meanwhile it is found that too high or too low prestress level will lead to the decrease of reinforcement effect. It is suggested that the prestress value should be 0.1 Pt (Pt is the design value of bolt pretension). Based on the seismic restoring force model, the restoring force characteristics of the reinforced member are determined, and the seismic damage model is modified based on the seismic damage model. The comprehensive influence coefficient of deformation and energy is introduced, and the seismic damage model suitable for the new reinforced RC column is established. The research results can lay a foundation for the engineering application of the reinforcement technology.

The demand for developing high-strength steel (HSS) earthquake-resilient structure systems presents new challenges in the field of earthquake engineering. A HSS H-beam to box column joint with steel slit dampers was proposed to improve seismic performance and self-centering capacity of the moment frame. Based on seismic design concepts of earthquake-resilient beam-column steel joints, Finite element (FE) models were developed and validated against experimental results. A FE parametric study was then conducted concerning some critical design parameters, including the aspect ratio of the steel beam, energy dissipator/beam yield strength ratio, splicing seam width to beam depth ratio, and steel beam span. The FE analysis showed that increasing the aspect ratio of the beam was beneficial in giving full play to the energy dissipation capacity of the energy dissipator. When the rotation angle (theta) of the beam-column joint was in the range of approximately 0.0075 rad to 0.015 rad, the energy dissipation capacity of the joint tended to stabilize, while when theta was not less than 0.015 rad, the energy dissipation capacity of the beam-column joint exhibited a remarkable increasing trend. When the energy dissipator/beam yield strength ratio (alpha) was not more than 0.6, the deformation of the beam-column joint was mainly concentrated on the energy dissipator. When the alpha was greater than 0.6, the proportion of joint energy dissipation contributed by the yielding of the steel beam increased rapidly. Moreover, when the splicing seam width (lg) to beam depth (hb) ratio was 2.9-8.6 % and the rotation angle of the beam-column joint was less than or equal to 0.04 rad, the hysteresis curves of all beam-column joints were almost coincident. Lastly, with the increase of the steel beam span, the energy dissipation capacity of the joint under the same rotation angle showed an increasing trend, which was beneficial to protect the primary structure from damage. Based on the above research results, it was mainly recommended that the alpha in the design should not exceed 0.6, and the ratio of lg to hb should not be less than 2.9 %.

To address the issues of excessive steel consumption and complex fabrication associated with traditional helical piles, this study proposes a novel type of concrete-filled thin-walled steel tubular pile with spiral ribs. This new design reduces steel usage by over 40 % while significantly improving manufacturing efficiency. Vertical compression tests were conducted on eight model piles to investigate the influence of spiral rib width and pitch on pile–soil bond–slip behavior. Results indicate that the ultimate bearing capacity of the spiral-ribbed pile reaches 12.7 kN, nearly six times that of a conventional steel tube pile (2.1 kN). The failure mechanism is characterized by circumferential shear-slippage along the spiral ribs at an angle of approximately 45°, with soil compaction observed beneath the ribs and a localized loosening zone forming above. A pronounced slip interface was observed around the pile shaft. Compared to straight-shafted piles, the spiral configuration maintains superior load-bearing performance even in the post-slip stage, demonstrating a strong safety reserve. Increasing the spiral rib width from 15 mm to 55 mm enhanced the ultimate bearing capacity by 81.4 %, while reducing the pitch from 300 mm to 165 mm led to a 15.9 % increase—indicating a more pronounced influence of rib width on performance. An optimal spiral configuration is recommended with a width-to-diameter ratio (D/d) of 2.0 and a pitch-to-diameter ratio (S/D) of 1.0. Based on the stress distribution in the surrounding soil, the influence radius extends to approximately 1.4 D, suggesting a minimum pile spacing of 2.8 D in practical engineering applications. Furthermore, a full-scale numerical simulation of pile–soil interaction was conducted, revealing that increasing the pile length from 12 m to 18 m results in the largest gain in ultimate bearing capacity—from 698 kN to 1554 kN. However, stress concentration occurs at the junction between the steel tube and spiral ribs, shifting the failure mode from soil failure to structural failure of the pile body. Therefore, it is recommended that pile length be limited to within 18 m. Finally, a theoretical model for calculating the compressive bearing capacity of spiral-ribbed concrete-filled steel tube piles is established based on the limit equilibrium theory. The findings of this study provide a theoretical foundation for the engineering application of this novel pile type.

To accurately predict the shear capacity of PRC coupling beams with small span-depth ratio, six different machine learning algorithms were used to establish the shear capacity prediction model of PRC coupling beams. The prediction performance of each model is comprehensively evaluated by four performance indicators. The results show that the prediction model based on support vector machine (SVM) algorithm and extreme gradient boosting (XGBoost) algorithm has the best robustness and generalization ability, and the mean absolute percentage error (MAPE) is only 6.72 % and 6.11 % respectively. Subsequently, the data-driven prediction model is compared with the existing semi-empirical shear capacity calculation method and the shear capacity calculation method based on the mechanical model. The analysis shows that the data-driven prediction model has better prediction accuracy and stability than the existing calculation methods, which not only significantly improves the computational efficiency, but also reduces the computational complexity and uncertainty.

This study investigated the impact of soil-structure interaction on the seismic performance of masonry ancient pagodas. For this purpose, shaking table tests were conducted using a pagoda model to simulate the seismic damage patterns and damage evolution of the pagoda under conditions considering soil-structure interaction. Additionally, numerical models were established for both rigid foundation conditions and soil-structure interaction conditions, validated through dynamic characteristic testing and shaking table experiments. The results indicated that under soil-structure interaction conditions, the top of the pagoda cracked first, with severe damage occurring on the second floor. The damage characteristics of the pagoda differ significantly from those observed under rigid foundation conditions. The numerical simulations effectively predicted the dynamic response of the structure. Compared to the results obtained under rigid foundation conditions, the acceleration of the upper structure decreased by 34 %-79 % after considering soil-structure interaction, while the horizontal displacement at the top of the pagoda increased by 1.4 mm-7.8 mm. The inter-story displacement angle of the first floor was amplified by 3-10 times, with significant degradation of stiffness, while the impact on the stiffness of the top floor was relatively minor. The tensile damage to the pagoda was more pronounced, and the damage area shifted from the first floor to the second floor. The findings provide important references for the seismic assessment of masonry ancient pagodas.

The variation in masonry materials along the height of brick-stone hybrid pagoda, its mechanical properties become more complex compared to the pagoda made from a single type of masonry. This study examines the dynamic performance and seismic resilience of the Wukong pagoda in China. Finite element software Abaqus was used to create detailed numerical models of the pagoda structure with brick, stone, and brick-stone hybrid masonry configurations. The seismic response of the three models was compared in terms of acceleration, inter-story deformation, and damage. Results show that tensile stresses are concentrated at the interfaces between masonry blocks and mortar in all models. Tensile cracking and damage occur at the mortar joints at the base of the stone masonry in the stone and the brick-stone hybrid pagodas, while the brick pagoda shows diagonal cracking at the opening corners. The brick-stone hybrid pagoda demonstrates reduced acceleration amplification effects at the brick-stone interface, lowering the upper structure's acceleration response. Notably, it exhibits minimal inter-story displacement and plastic strain damage, indicating superior seismic resistance compared to the single-material pagodas.

In order to study the seismic mechanism of masonry walls with intricate openings reinforced by polypropylene mesh-composite cement mortar, three sets of specimens with door-window openings and one set of specimens without openings were designed and manufactured. Cyclic loading tests were conducted to observe the failure phenomena during loading, which to compare and analyse the hysteretic behavior, load-bearing capacity, and stiffness degradation of each specimen. Finally, finite element numerical simulation was also performed, and the calculation results were compared with the experimental results. The results indicate that comparing the walls after single-sided surface reinforcement and double-sided surface reinforcement to unreinforced wall,the ultimate load-load-bearing capacity increases by 28.06% and 95.1%, the initial stiffness increases by 40.92% and 49.70%, and the ductility coefficient increases by 22.87% and 50.98%, respectively. During loading, the wall without openings experienced shear failure along the horizontal joint, while the wall with openings experienced shear-compression failure at the corner of the opening and between the walls of the door-window. Compared with the wall without openings, the seismic performance indicators of the wall with openings are reduced. After using the polypropylene mesh-composite cement mortar surface layer reinforcement, the development of the main cracks in the wall was inhibited, resulting in the wall experienced diagonal shear failure at the opening corner, and the initial stiffness, seismic load-load-bearing capacity, and deformation capacity were increased. The characteristic load errors of finite element analysis and experimental results for each specimen were all less than 15%. In the wall without reinforcement, the damage was most severe in the wall limbs on both sides of the opening. After reinforcement, the wall damage extended from the walls between the door-window to the corners of the opening, and the distribution of damage was consistent with the experimental failure zone.

A method for identifying structural damage in masonry pagodas based on wavelet packet energy variation was proposed, with the change in wavelet packet energy of dynamic response signals before and after structural damage being used as the damage indicator. Finite element software was employed to establish a numerical model of the Kaiyuan Pagoda. By introducing different types of damage and applying seismic waves in three directions under four working conditions, a seismic response analysis was conducted. The acceleration response signals at feature points on each floor of the structure were subjected to wavelet packet transformation, and the wavelet packet energy was calculated. Based on the wavelet packet energy variation (DSI), damage indicators were determined, and structural damage identification was carried out. The identification results were compared with the preset damage. The results showed that, in the absence of noise interference, the damage indicators clearly correlated with the damage of the masonry pagoda, enabling accurate localization of the damage. Even when Gaussian white noise was added to the acceleration dynamic response signals, the indicators could still accurately identify the damage location, demonstrating good noise resistance. The research results provided an effective method for the damage assessment of masonry pagodas.

Although site effects are essential, they have received limited attention in studies on masonry pagodas. This study integrates shaking table tests and dynamic characteristic tests to develop models of ancient masonry pagodas under various site classifications. The seismic responses were calculated, with analyses of acceleration, displacement, and the spatial distribution of tensile damage. The results show that site classification significantly influences both the dynamic response and damage propagation patterns of the pagodas. The site soil weakens the pagoda's acceleration response. As the soil stiffness decreases, the displacement at the top of the pagoda increases, and the stiffness degradation at the first floor intensifies. The tensile failure at the variable cross-section of the first floor evolved from center-outward expansion to edge-inward development. Initial damage was concentrated at the first-floor eaves and second-floor openings, gradually extending upward with increasing seismic intensity. In Site Class I, damage evolved from localized arc-shaped cracking to overall surface failure, whereas in other site classes, edge cracking was more pronounced. These findings provide a scientific basis for evaluating the seismic performance and site adaptability of masonry pagodas and offer valuable references for their preservation and reinforcement design.

This study introduces an innovative spiral stiffener to mitigate the local buckling issue of thin-walled steel tubular concrete. In response to diverse restraint forms, 5 distinct specimen types were designed to probe the eccentric compression test. behavior & failure modes of the composite member. Test results: Spiral ribs limit steel tube buckling between stiffeners, reduce degree. Vs. ord. concrete-filled steel tube, bearing cap. up from 932kN to 1119kN (20% growth), safety margin from 1.48 to 1.84 (24% incr.). An empirical analysis of impact parameters was conducted, revealing that the pitch($p$p) and width-thickness ratio of the spiral rib(${b_{\rm{r}}}/{t_{\rm{r}}}$br/tr) had a more pronounced effect on the damage morphology of the specimen. Design recommendations were provided: the diameter-thickness ratio of the steel pipe(${d_{\rm{s}}}/{t_{\rm{s}}}$ds/ts)was limited to 110-150, the reinforcement rate($\rho $rho) was between 0.8% and 2%, the pitch was 3.33 times the diameter of the specimen, and the width-thickness ratio of the spiral ribs was between 6 and 10. Through eccentricity(${e_0}/{r_c}$e0/rc) analysis, the damage limitations of this new component were determined to be approximately 0.5 eccentricity for both large and small eccentricities. Finally, based on superposition theory, a formula for ecc. compressive bearing cap. of new member type is proposed.