Search Results (129)

To systematically investigate the effects of C-shaped and rectangular steel frames on the seismic performance of assembled composite shear walls, this paper, based on the validation of existing pseudo-static test results, employs ABAQUS software to establish refined finite element models, and carries out parametric analyses on C-shaped steel-frame composite shear walls (CSCSWs) and rectangular steel-frame composite shear walls (RSCSWs). With shear-span ratio, axial-load ratio, boundary frame steel plate thickness, and concrete strength grade as variables, a total of 28 numerical models are designed to systematically examine the influence laws of each parameter on bearing capacity, ductility, energy dissipation capacity, and failure modes, and to reveal the performance differences in the confinement mechanisms of the two cross-sectional types. The results indicate that: as the shear-span ratio decreases from 3.0 to 1.0, the bearing capacity increases by up to 171%, but the ductility drops by up to 43%, and the failure mode shifts from flexure-dominated to shear-dominated; increasing the steel plate thickness can simultaneously enhance bearing capacity and ductility, with the peak load increasing by up to 52% and cumulative energy dissipation by over 110%, the mechanism being the synergistic enhancement of the flexural contribution of the boundary frame and the passive confinement effect on the core concrete; increasing the axial-load ratio can improve bearing capacity by about 24%, but significantly impairs ductility and energy dissipation capacity, and it is recommended that the design axial-load ratio be controlled between 0.26 and 0.43; the concrete strength grade has a limited effect on bearing capacity, and as the strength increases, brittle characteristics emerge, leading to a ductility decrease of about 12%; therefore, provided that the strength requirements are met, enhancing the concrete strength grade should not be taken as the primary technical approach for improving the seismic performance of such structures. Comparing the two cross-sectional types, the rectangular cross-section, by providing more uniform and effective lateral confinement, exhibits superior bearing capacity, ductility, and energy dissipation to the C-shaped cross-section across the entire parameter domain, and its performance advantages are more pronounced under conditions of high axial-load ratio and large shear-span ratio. Full article

Landslides in weathered gypsum deposits present significant geotechnical challenges because progressive weathering, groundwater fluctuations, and residual strength degradation strongly influence slope stability. This study investigates the failure mechanism and remediation of a large translational landslide in weathered gypsum deposits in Çankırı, Türkiye. An integrated engineering geological assessment was conducted using data from 16 boreholes, laboratory tests, and groundwater/inclinometer monitoring records, followed by residual shear strength back-analysis and slope stability evaluation. A three-dimensional geological model was developed, and cross-sections were analyzed using the Morgenstern–Price limit-equilibrium method. Back-analysis identified residual shear strength parameters of c′ = 7.5 kPa and ϕ′ = 10° for the weathered gypsum, while laboratory direct shear tests yielded c′ = 4.0 kPa and ϕ′ = 9.9°. The friction angles obtained from the two approaches are nearly identical, whereas the back-calculated cohesion is slightly higher than the laboratory-derived value. Back-analysis parameters were used to design remediation measures, including slope unloading, rock buttress construction, toe fill improvement, and surface/subsurface drainage. Stability analyses increased the factor of safety to 1.76 under static loading, while pseudo-static analyses satisfied the recommended seismic design criterion (FS ≥ 1.10). Equivalent-linear Newmark analyses predicted a permanent displacement of 15 cm, within acceptable limits. The methodology provides a practical framework for assessing and stabilizing landslides developed in weathered gypsum deposits in seismically active regions. Full article

In the preliminary vehicle design process, Finite Element Analysis (FEA) and Multi-Body Dynamics (MBD) simulations require detailed physical parameters that are not available during the conceptual design phase. This study proposes a novel analytical algorithm that uses a virtual weighting approach to rapidly establish a reasonable baseline for these parameters, serving as an efficient analytical precursor to the physical tests, complex dynamic simulations, and optimization methods conventionally applied in later stages. In this study, a dual-layer model for rapid geometric assessment of stability indices and vertical loads in hyperstatic 8 × 8 vehicles is proposed. The model consists of a prognostic Weighted Singular Value Decomposition (SVD) layer and an operative Weighted Pseudo-Inverse (WPI) layer. In the SVD layer, a spectral mode alignment technique is proposed to evaluate the load transmission capacity to predict the stability limits under worst-case operating conditions including extreme maneuvers and wheel failures. In the WPI layer, the optimal distribution of wheel loads is computed under different operating conditions. For a uniform vehicle configuration, a high-resolution continuous sweep of lateral acceleration identifies the exact wheel lift-off point at 0.8621 g, perfectly aligning with the theoretical Static Stability Factor (SSF). By employing a virtual weighting strategy instead of relying on traditional exhaustive physical parameters, this parameter-independent framework provides an analytical load-boundary evaluation and determines the theoretical topological capacity, thereby acting as an essential tool for preliminary conceptual design prior to detailed MBD and FEA analyses. Full article

The full operation of BDS-3 enables users to obtain high-performance positioning services, benefiting from the surge in the number of Global Navigation Satellite System (GNSS) observations with multi-constellation multi-frequency signals. This overabundance is beneficial to improve in-flight navigation accuracy for small unmanned aerial vehicles (UAVs). However, it brings about two-fold challenges for conventional airborne GNSS/SINS tightly coupled (TC) systems. On one hand, limited airborne computing resources suffer from the “curse of dimensionality” caused by extremely high-dimensional GNSS observations (i.e., GNSS pseudo-ranges, pseudo-range rates, and time-differenced carrier phases from multi-system and multi-frequency, such as GPS L1/L2 and BDS B1/B2/B3, totaling up to over 100 observables per epoch), leading to increased calculation burden and potential latency. On the other hand, possible outliers can degrade the obtained navigation accuracy. To enhance overall performance, this paper proposes a computationally efficient Kalman filtering framework for tight integration between airborne GNSS and SINS via a high-dimensional robust information filter. The strategy of kinematic and static information filtering is utilized to handle the matrix inversion complexity caused by high-rate and high-dimensional Kalman measurement updates, and the technique of robust adaptive factor is used to resist the adverse effects of GNSS outliers and modeling errors. Both land vehicular and UAV flight tests indicate that the proposed algorithm outperforms its traditional TC counterparts, demonstrating an over 90% improvement in overall computational efficiency without any loss in accuracy, compared with conventional batch or sequential tightly coupled Kalman filtering. Full article

In order to meet its need of functional improvement, the existing masonry structure generally adopts the method of replacing partial walls with concrete frame columns to expand the openings and reduce the number of the longitudinal walls. However, the partial removal of longitudinal masonry walls and the introduction of large openings may result in a nonuniform distribution of lateral stiffness in plan and consequently induce torsional response under horizontal seismic loading. In order to investigate the seismic performance of the existing masonry structure after replacement, a 1:4 scale four-story brick masonry–concrete structure model was designed and made. Based on the principle of stiffness equivalence, the partial walls on the side of the large openings of the model ground-level floor were replaced by frame columns and frame beams, and then the pseudo-static test was conducted on the model. Through the test, the failure patterns of each floor in the structure and the seismic performance indexes such as hysteresis curve, skeleton curve, displacement ductility, stiffness degradation, and energy dissipation capacity, were obtained. The results showed that the yield load of the ground-level floor with the equivalent frame columns is approximately 138% of that of the second and third floors, while its yield displacement is approximately 59% of that of them. That is, after the structure enters the yield stage, its ground-level floor has good bearing capacity and resistance to deformation. The ground-level floor of the structure consumes the least energy as compared to the second and third floors, while the second floor consumes the most energy and has stiffness mutation, and the damage to the walls in such layer is also the most serious. Hence, seismic strengthening of the second story should be considered to prevent the formation of a weak or soft story and the consequent risk of structural collapse. Although there is a significant difference in the material properties between reinforced concrete frames and masonry structures, it is feasible to use the replacement method based on the stiffness equivalence to solve the problem of structure torsion caused by the irregular plane arrangement. Full article

In view of the key problems such as the weakened seismic performance and reduced safety caused by the expansion of openings at bottom floor of masonry structure to meet the functional requirements, a 1:4 scale model of a four-story brick-concrete masonry structure was designed and fabricated. Based on the principle of stiffness equivalence, the partial masonry walls on the side of the bottom floor with large openings were replaced by reinforced concrete walls, and then the pseudo static test was conducted on the model. Through the test, the seismic performance indexes such as the failure mode of each floor, the displacement, hysteresis curve, skeleton curve, and stiffness degradation were obtained. The results showed that the masonry structure can form a close connection with the reinforced concrete walls and then the whole structure exhibits the characteristic of ductility. There is no sudden change in bearing capacity during the loading and the hysteresis curves show that the structure retained a certain energy dissipation capacity during cyclic loading, without sudden loss of bearing capacity. The displacement of the second floor of the structure changes significantly, and its stiffness should thus be paid more attention to during the design process to avoid the formation of a weak floor. The torsional of the masonry structure with large openings at its bottom floor under earthquake can be avoided through the setting of reinforced concrete walls. Full article

Sustainable landslide hazard mitigation requires scenario-based assessment of nature-based solutions under realistic hydromechanical and multi-hazard conditions. This study evaluates the mechanical effect of Vetiver grass (Chrysopogon zizanioides) on slope stability in Loja, southern Ecuador, through an integrated framework combining geotechnical characterization, direct shear testing, finite element modelling, limit equilibrium analysis, and targeted statistical evaluation. Three fine-grained soils, classified as CH, MH, and ML, were analysed under baseline groundwater conditions, groundwater with an 8 kN/m² surcharge, and groundwater with surcharge plus pseudo-static seismic loading. Vetiver reinforcement increased apparent cohesion by 8.92–27.65% and internal friction angle by 6.90–17.43%, with the highest cohesion gain in ML soil. Numerical results showed that stabilization was controlled by soil type, slope geometry, loading condition, and interaction between the 2.0 m root-reinforced layer and the governing failure mechanism. Under surcharge loading, FS for ML at 0.5H:1V increased from 1.056 to 1.450. Under combined loading, FS increased from 0.217 to 1.440 for ML at 1H:1V and from 0.587 to 2.060 for CH at 1H:1V. Targeted ANOVA/MANOVA for MH soil confirmed the influence of geometry and combined loading. Therefore, Vetiver should be considered a complementary, site-specific, and risk-informed mitigation measure rather than a universal stabilization solution. Full article

Currently, the development of civil engineering industry is gradually slowing down, with the focus gradually shifting toward the reinforcement and renovation of existing buildings. Among these existing structures, reinforced concrete (RC) structure is a kind of structure with high proportion. Therefore, this paper conducts research on the seismic properties of RC buildings after adding new beams to existing columns. This paper first introduces the design situation of the specimen, followed by an experimental investigation of its mechanical properties using pseudo-static tests. Based on the failure patterns and hysteresis curves, the differences between the new-type specimen and RC specimen are analyzed. The findings indicate that, while ensuring load-bearing capacity, the new-type joints exhibit better seismic performance: the bearing capacity and maximum displacement are increased by at most 9.2% and 14.9% respectively, and the fuller hysteresis curve shows that the new-type specimen has better energy dissipation capacity. Finally, this paper extends the analysis of the design parameters of the specimens using finite element components. The modeling results reveal that the bearing capacity varies by less than 1% with different parameters such as connector thickness, concrete strength grade, and bolts quantity and strength, indicating that these parameters have a relatively small impact on the bearing capacity. While for the specimen dimensions and thickness and strength of wrapped steel of beam, the maximum increase in bearing capacity is 32.3% and 6.0%, respectively. Indicating that their impact is quite significant. The findings of this paper provide a reference for structural design and contribute to advancing the work of reinforcement and renovation of existing concrete structures. Full article

After prolonged development, offshore edge- and bottom-water reservoirs have entered an ultra-high water-cut stage. Under long-time multilayer commingled production conditions, accurate dynamic quantification of layer-wise production remains technically challenging, and conventional production allocation approaches often lack the accuracy required for fine-scale reservoir management. To address these challenges, this study proposes a production allocation method that integrates static reservoir properties, dynamic production performance, and pressure-based correction. The resulting layer-wise allocation provides a quantitative basis for evaluating remaining oil utilization and delineating the distribution of remaining oil across individual layers. The method is formulated on the basis of a pseudo-steady-state productivity model that incorporates wellbore imperfection effects. The initial production rate of each layer is calculated by combining reservoir transmissibility with production pressure drawdown. To account for unequal pressure responses among layers under commingled production—resulting from pressure imbalance, limited edge- and bottom-water energy support, and interlayer interference—a correction factor is introduced to adjust the effective production contribution of low-pressure layers. Compared with the PLT test results, the average error of the conventional KH method was 16.7%, whereas the average error of the proposed method was reduced to 6.1%. The average error was reduced from 16.7% to 6.1%, corresponding to a 63.5% reduction in prediction error, indicating that the proposed approach can provide a more reliable estimation of layered production contribution. The proposed method enables continuous and dynamic production allocation for commingled wells without the need for frequent surveys, offering a practical tool for identifying multilayer production imbalance, evaluating remaining potential, and supporting development optimization in offshore oilfields. Full article

Real-time precise point positioning (PPP) is increasingly supported by open satellite-broadcast state-space representation (SSR) services, yet standalone operation with a single service remains vulnerable to limited constellation support, correction outages, latency variations, and service-dependent modeling inconsistencies. In the Asia-Pacific region, MADOCA-PPP and PPP-B2b provide two publicly accessible and complementary SSR sources, but their consistent fusion before user-level PPP estimation remains insufficiently investigated. This paper proposes a correction-domain fusion framework that combines MADOCA-PPP and PPP-B2b orbit and clock corrections before PPP estimation, rather than merging final positioning solutions. Inter-service discrepancies and unknown cross-correlations are handled by a bias-state-aware structured covariance intersection strategy, in which the relative weighting is derived from the respective correction information (inverse variance), preserving statistical consistency and avoiding overconfident fusion. A unified multi-GNSS PPP scheme further supports signal-priority harmonization, broadcast-ephemeris adaptation, correction-age control, and GLONASS inter-frequency and differential code bias handling. Static-station per-epoch (pseudo-kinematic) and offshore kinematic experiments validate the framework. In the static-station test, fusion raised the mean number of valid satellites from 21.98 and 14.98 to 26.56 and improved the horizontal RMS to 0.033 m—better than either standalone service (0.037 m, 0.079 m)—confirming a genuine combination rather than source selection, while the 3D RMS (0.068 m) matched the best standalone service (0.066 m). In the offshore test, fusion achieved the best overall accuracy (0.232 m horizontal, 0.290 m 3D, versus 0.332 m and 0.313 m for the standalone services) and the most satellites (25.4). It also degraded most slowly with increasing elevation cut-off, outperforming both services about threefold at 40°. A normalized-innovation-squared check confirmed the fused covariance is consistent and not overconfident (median ≈ 1.1; within the 99% bound in 100% of epochs). Under single-service outages from 30 s to 600 s, fusion maintained 100.0% availability, confirming its advantage in redundancy, continuity, and resilience. Full article

To explore the evolution of dynamic characteristics of Chuan-Dou timber structures under different damage states, this study takes a typical Chuan-Dou timber structure in Southwest China as the research object. A 1:7 scaled model of a two-story timber frame with five main columns and four secondary columns, three bays, and two rooms was designed and fabricated, and combined pseudo-static and dynamic tests were carried out. When the specimen was in three typical states, namely intact, moderate damage, and severe damage, the sudden release method was adopted to obtain structural vibration responses. The natural frequencies and damping ratios in the X- and Y-directions under each state were identified, and the damage sensitivity differences among stiffness, frequency, and damping ratio were compared and analyzed. The test results show that with the aggravation of damage degree, structural stiffness degrades continuously, and the natural frequency shows a monotonic decreasing trend. The X-direction frequency decreases from 11.178 Hz to 7.8 Hz, and the Y-direction frequency decreases from 6.2 Hz to 5.156 Hz. The damping ratio increases significantly. The X-direction damping ratio increases from 3.552% to 8.951% (an increase of 152.0%), and the Y-direction damping ratio increases from 4.391% to 11.94% (an increase of 171.9%). Comparative analysis shows that the change amplitude of the damping ratio is about 5 to 10 times that of the natural frequency, and it has higher identification sensitivity to structural non-linear damage behavior. This paper innovatively applies the frequency-damping ratio dual-index collaborative determination strategy to Chuan-Dou timber structures, establishes a damage identification method based on the evolution of dynamic characteristic parameters, and discusses the engineering application paths of sensor optimal layout strategy, structural health archive establishment, and post-earthquake rapid screening. The research results can provide experimental basis and technical reference for daily health monitoring, post-earthquake rapid identification, and seismic performance evaluation of traditional timber structures of Chuan-Dou timber structures. Full article

Buckling-restrained braces (BRBs) are widely used to improve the seismic performance of high-rise and long-span structures. This study proposes a triple-tube GFRP–steel buckling-restrained brace (TTGS-BRB) as a lightweight and corrosion-resistant energy-dissipating member for such structures. To investigate its hysteretic behavior, pseudo-static tests were conducted on two scaled TTGS-BRB specimens with different wrapping orientations and end details, and a finite element model was established and validated against the test results for further parametric analyses. The test results showed that the specimen with the ±30° wrapping configuration and end stiffeners exhibited better hysteretic performance than the 90° specimen without end stiffeners, with the yield force increasing from 147.98 kN to 161.68 kN, the cumulative plastic deformation (CPD) increasing from 7.49 to 209.56, and the cumulative plastic energy (CPE) increasing from 5.25 to 199.12. Based on the validated finite element model, the effects of fiber wrapping orientation, end stiffeners, interfacial gap, P_cr/P_y ratio, and steel tube diameter-to-thickness ratio on the hysteretic performance of full-scale TTGS-BRBs were systematically investigated. The numerical results indicate that wrapping orientations within the range of ±0° to ±45°, end stiffening at both ends, an interfacial gap of 1.5 mm between GFRP and steel, an appropriate P_cr/P_y ratio, and a steel tube diameter-to-thickness ratio of less than 24 are beneficial for improving the hysteretic performance of TTGS-BRBs. These findings provide useful references for the design and application of TTGS-BRBs in practical engineering. Full article

This study examines the seismic stability of an underground powerhouse cavern located in the Lesser Himalayan region of Nepal. Both static and seismic loading conditions are analyzed using the finite element method (FEM) and the distinct element method (DEM). Rock mass properties are derived from field investigations and laboratory testing, while empirical correlations are applied to estimate rock mass strength and deformation modulus. Pseudo-static analyses are performed using the FEM-based software Rock and Soil-2-Dimensionsl (RS²) Version 11.027, and dynamic analyses are conducted using the DEM-based software Universal Distinct Element Code (UDEC) Version 5.0 to evaluate deformation and stress redistribution around the cavern. Seismic fragility curves are developed to quantify the probability of damage under varying seismic intensities. Results indicate that a peak ground acceleration (PGA) of 0.25 g increases cavern wall deformation by approximately 15–20 mm compared to static conditions. Fragility analysis shows a probability exceeding 68% for slight damage, while the probability of collapse remains low at approximately 1.7%. Seismic loading also significantly alters stress redistribution along the cavern boundary. Overall, the combined use of numerical modeling and fragility analysis provides a probabilistic framework for assessing seismic risk in underground caverns, offering valuable insights for the design and safety evaluation of hydropower projects in seismically active Himalayan regions. Full article

Ultra-High-Performance Concrete (UHPC) reinforced with steel fibers has emerged as a promising alternative to conventional concrete, which exhibits limited tensile capacity and a low modulus of rupture and is prone to brittle damage under cyclic loading—a critical drawback in seismic applications. The increasing demand for resilient, damage-tolerant construction materials in seismically active regions worldwide has intensified the need to evaluate the seismic performance of UHPC structural systems at the structural scale. However, the seismic behavior of full structural frames built entirely with cast-in-place UHPC remains largely unexplored. This study presents a full-scale experimental evaluation of single-story UHPC frames with two steel fiber volume fractions (1.0% and 1.5%) subjected to pseudostatic in-plane cyclic loading. A conventional reinforced concrete frame was tested for comparison. Key performance parameters—including hysteretic response, stiffness degradation, and energy dissipation—were assessed. The results suggest that the UHPC frames exhibited enhanced performance in comparison to the conventional frame across the measured parameters. The UHPC frame with 1.5% steel fiber content consistently outperformed both the 1.0% UHPC frame and the conventional reinforced concrete frame in terms of lateral strength, initial stiffness, and energy dissipation capacity, highlighting the critical role of fiber dosage in optimizing seismic performance. The 1.5% fiber UHPC frame reached approximately 59 kN in maximum lateral strength and 6.3 kN/mm in initial stiffness, representing increases of around 59% and 58%, respectively, relative to the conventional frame (~37 kN and 4.0 kN/mm). While stiffness degradation was observed in all specimens, the UHPC frames retained higher stiffness values throughout the test. At 5.5% drift, the 1.5% UHPC frame dissipated approximately 146,000 J, compared to 80,000 J for the conventional frame. These findings indicate that steel fiber-reinforced UHPC may improve the cyclic performance of frame structures and could serve as a viable alternative for earthquake-resistant construction. The results reported here should be interpreted as indicative trends rather than statistically generalizable conclusions. A key limitation of this study is that the experimental program focused solely on single-story frames under quasi-static loading; dynamic effects and multi-story behavior were not addressed. Full article

Understanding how gate-opening variations affect the upstream water level is essential for quantitative water allocation and automation in irrigation canals. Using an indoor recirculating rectangular open-channel facility equipped with a standard flat sluice gate, we deployed five upstream water-level gauges (Points 1#D–5#H) and conducted step response tests and pseudo-random binary sequence (PRBS) tests under four representative operating conditions (Q ≈ 30–85 m³/h). For step tests, the upstream water-level dynamics were well approximated by a first-order plus dead-time (FOPDT) model. Under low flow (Condition A, Q ≈ 29.5 m³/h) with a 1.5 → 2.0 cm opening step, the identified parameters were K ≈ −15.4 mm/mm, L ≈ 4.5–5.7 s, and T ≈ 71 s, and the five points exhibited strong spatial consistency. Under higher flow (Condition B, Q ≈ 72.5 m³/h) with a 3.0 → 3.5 cm step, the gain magnitude decreased (K ≈ −10.6 mm/mm), the dead time increased moderately (L ≈ 8.0–10.3 s), and the time constant became smaller (T ≈ 41–43 s), indicating a faster response but weaker sensitivity to gate-opening changes. For PRBS tests, a discrete-time ARX (2,2,1) model was identified between gate opening and the upstream level deviation at Point 3#F. The identified ARX models achieved R² of 0.992 (Condition C) and 0.946 (Condition D), with MAE and RMSE within 0.65–1.85 mm, and residual diagnostics supported the adequacy of the selected model structure. Finally, steady-state gains derived from dynamic identification were consistent with static water-level–flow–opening relations obtained from quasi-steady experiments, providing a physical basis for the models. The proposed simplified models offer a unified and engineering-friendly plant description for designing and comparing controllers such as PID, fuzzy control, and reinforcement learning-based approaches. Full article