Search Results (188)

High-speed railway track–bridge systems (HSRTBSs) in near-fault high-seismicity regions face combined threats from pulse-type seismic excitations, vertical earthquake components and track defects, which may trigger structural damage and deterioration of track regularity. This paper establishes refined OpenSEES coupled numerical models for a typical 32 m simply supported girder bridge equipped with CRTS II slab ballastless track, considering both conventional spherical steel bearings and friction pendulum bearings (FPBs). Nonlinear time-history analyses are performed with near-fault pulse-like and far-field non-pulse ground motions to explore the influences of peak ground acceleration (PGA), vertical-to-horizontal acceleration ratio (αVH), and CA mortar void length. The results demonstrate hierarchical controlling effects of these parameters. PGA dominates the overall seismic response; sliding layer damage follows the sensitivity sequence PGA > αVH > CA mortar void, whereas post-earthquake traffic capacity degradation obeys PGA > CA mortar void > αVH. Near-fault pulse-like ground motions produce more severe structural damage compared with far-field inputs. FPB isolation yields a maximum pier-top seismic reduction ratio of 86.73% and effectively mitigates structural deformation, but cannot eliminate track irregularity originating from CA mortar void defects. Conditional on the 0.2 g seismic level and the given structural configuration adopted in this study, αVH = 0.65 and the 1.95 m critical CA mortar void length for longitudinal track constraint failure can serve as reference values, though they are not universally applicable for all track–bridge systems. This work provides insights for seismic design, CA mortar defect remediation and post-earthquake traffic assessment of near-fault isolated HSRTBSs. Full article

In the process of subway construction, the control of construction quality and accuracy is the core link. Deviation in the construction of a steel spring floating slab foundation under the rail can easily cause problems such as abnormal rail installation, insufficient adaptability of vibration isolators, and decreased vibration reduction performance, seriously threatening the safety of train operation and increasing maintenance difficulty. In view of this, this article addresses the issue of excessive deviation in the construction of a subway steel spring floating slab track, and systematically identifies the main types of spatial geometric deviations in each process. Based on on-site measured data, the distribution pattern and statistical characteristics of construction deviations in each process were revealed through data statistical methods, and the causes of deviations were analyzed. Based on the quantitative analysis of structural characteristics and deviation sources, a mathematical model of the underground foundation space was constructed using the spatial geometric transformation method. Combined with the process sequence relationship, a deviation transmission model for floating slab track construction was established, clarifying the deviation analysis process and providing theoretical support for subsequent research on construction correction. Full article

Building Information Modeling (BIM) usually represents a building as a static snapshot of the model’s state. Dynamic extensions, such as Internet of Things(IoT)-enabled sensing or immersive visualization, already exist, but the underlying data model remains state-based. The Industry Foundation Classes (IFC) standard does not define a formal mechanism that would link the same physical element across successive phases of a building’s life cycle. Design, construction, and operation are recorded in separate IFC files, and the same element is assigned different Globally Unique Identifiers (GUIDs) in each. The result is fragmentation of the element’s identity, loss of the history of property changes, and the inability to formulate cross-phase queries. This paper proposes the BIM-Phase ontology based on the fundamental Descriptive Ontology for Linguistic and Cognitive Engineering (DOLCE) ontology, which solves this problem by introducing a distinction between a building element as an endurant and its life cycle phases as perdurants. The ontology comprises nine classes, six object relations, and six axioms expressed in Web Ontology Language 2 Description Logic (OWL 2 DL). Phase properties and relations are represented using a reification pattern, which maintains full compatibility with the expressiveness of OWL 2 DL. The ontology was validated using an example of a single-family residential building developed in Autodesk Revit. Three structural elements (external wall, floor slab, and column) were tracked across three phases of the life cycle. Eight competency questions covering scalar, constitutional, and mereological changes were defined and mapped to ontology constructs, confirming that the BIM-Phase enables the recording of changes and the formulation of cross-phase queries that are impossible in classic IFC. All eight questions were answered correctly on the published knowledge graph, and the HermiT reasoner confirmed the logical consistency of the model. The findings show that preserving element identity across phases requires only a minimal ontological layer on top of existing standards. We recommend introducing persistent, phase-independent identifiers of building elements alongside IFC GUIDs, as this single change enables full lifecycle change tracking. Full article

The gradual deterioration of interfacial performance in CRTS II (China Railway Track System II) slab ballastless tracks during long-term service can significantly affect structural stability and durability. Existing studies have mainly focused on the fatigue performance of the overall track system and individual structural layers, whereas probabilistic fatigue-life modeling of the interlayer interface remains relatively limited. This study investigates the fatigue life behavior of the track slab-CA (cement-asphalt) mortar interface under cyclic loading. An exponential stress life relationship was combined with a two-parameter Weibull distribution of fatigue life at a specified stress ratio to establish a multi-parameter Weibull-based probabilistic framework that links fatigue life, stress ratio, and failure probability. Push-out and positive tensile fatigue tests were conducted on composite specimens to obtain interface fatigue lives under different stress ratios. Leveraging the multi-parameter Weibull model and experimental data, the L-BFGS-B (Limited-memory Broyden-Fletcher-Goldfarb-Shanno with Box constraints) algorithm was employed to optimize the model parameters and construct a probabilistic fatigue life model. The calibrated model was then used to analyze the fatigue behavior of the slab-CA mortar interface under tangential and vertical loading. The results show that the proposed probabilistic framework provides good agreement with the interface fatigue test data and enables the fatigue-life distribution and failure probability of the interlayer interface to be evaluated under different stress ratios. The findings provide a probabilistic basis for fatigue assessment and durability analysis of CRTS II slab ballastless track interfaces. Full article

Using the Suzhou East Station integrated transportation hub as a case study, this paper investigates the train-induced vibration responses and their distribution patterns under various operating conditions of high-speed railway lines, intercity lines, and subway lines. The results show that train speed is the dominant factor: the high-speed railway passage controls floor vibrations in most stories, while line distance also plays a role for some floors. No significant amplification is observed under multi-train convergence; the vibration level is similar to that of the most unfavorable single-train condition. Therefore, only the most unfavorable single-train condition needs to be considered. As vibrations propagate upward through the floors, high-frequency vibrations gradually attenuate while low-frequency vibrations are amplified, leading to an overall amplification of vibrations at the top floors of some buildings. The floor vibration response level decreases as the vertical stiffness of the structural member increases. Cantilevered slabs and mid-span areas are vibration-sensitive zones. For station–city integrated transportation hubs with high-speed railways running underneath, track vibration mitigation measures should be prioritized, such as thickening the track slab. Thin side-wall vibration mitigation pads have a poor vibration reduction effect. When diaphragm walls are rigidly connected to the station and buildings, they amplify the building’s vibration response. Full article

With the integrated development of high-speed railways and urban underground rail transit, large high-speed railway station buildings are often seamlessly connected or even co-constructed with subway structures, forming a complex structural system that integrates high-speed rail, subway, and station buildings. To investigate the dynamic performance of such “ integrated station-bridge” station buildings constructed with subways, this paper takes Yichang North Station as an engineering case study and examines its vertical dynamic characteristics under multi-source train-induced loads. The station adopts a structural configuration where the station tracks are fully integrated with the station building, while the main lines are separated from it. To accurately simulate the entire process of train operation, this study established a refined “train-track-station” spatially coupled dynamics model that incorporates high-speed and subway trains, tracks, and the station structure. Based on this model, various operational scenarios were systematically analyzed, including high-speed trains passing at different speeds, parallel operation of multiple train lines, and combined operation of high-speed and subway trains. The results demonstrate that, when single or multiple high-speed train lines pass through the station at the design entry speed of 80 km/h, the vertical vibration acceleration of the elevated waiting level meets human comfort standards. The train-induced vibration response is transmitted and superimposed along the “column–beam–slab” path, resulting in localized acceleration peaks at the mid-span regions of beams and slabs directly above the tracks. Second, the impact of subway train operation alone on the vibration of the elevated level is significantly weaker than that of high-speed trains. Furthermore, under combined high-speed and subway train operations, the additional vibration contribution from subway trains shows a decreasing trend as the number of simultaneously operating high-speed train lines increases. The findings of this study validate the effectiveness of the structural design of Yichang North Station in terms of train operational safety and passenger waiting comfort. The revealed patterns of multi-source vibration transmission and superposition can provide important theoretical and numerical references for the dynamic optimization design and vibration control of similar integrated transportation hub structures. Full article

To address the problems of easy cracking and the difficulty in balancing construction schedule and structural quality in the construction of ultra-long concrete slabs, this paper takes the ultra-long floor slab project of an inpatient building in the Science City Campus of Chongqing University Cancer Hospital as the research object, and conducts research on temperature and crack control in the construction of the alternative bay method. The key structural mechanical parameters are determined through theoretical calculation. The temperature and deformation changes during the whole process of concrete pouring are tracked by combining on-site monitoring and finite element simulation, and the effects of different construction parameters are compared and analyzed. The results show that when the alternative bay method is adopted, the overall temperature distribution of the floor slab is uniform, and there are obvious differences in deformation at different positions. The center of the first-poured slab has smaller deformation, the beam side has larger deformation, the later-poured slab has larger overall deformation, and tensile deformation occurs on both sides of the construction joint. Reasonably dividing the pouring blocks, optimizing the pouring sequence and extending the pouring interval can significantly reduce the tensile deformation of concrete and alleviate stress concentration. This study confirms that the alternative bay method can effectively reduce the risk of temperature-induced cracking in ultra-long floor slabs and provide technical reference for seamless construction of similar above-ground structures. Full article

The prefabricated polyurethane-solidified track bed (PPSTB) combines the adjustability of ballasted tracks with the low maintenance requirements of slab tracks, offering a promising solution for railway sections on deformable foundations. This study investigates the interaction and mechanical behaviors of the polyurethane-solidified ballast (PSB) modules and bulk ballast under laboratory loading. A series of unconfined uniaxial tests, confined ballast box tests, and cyclic loading tests were conducted, complemented by discrete element method (DEM) simulations to analyze mesoscopic particle evolution. Under monotonic compression, the stress–strain curve exhibits three distinct stages with an average elastic modulus of 19.66 MPa, where the central aggregate framework acts as the primary load-bearing structure. Confinement increases the modulus by 33.57% and yields a nearly linear stress–strain relationship, attributed to a more compact and uniform contact distribution. Furthermore, under cyclic loading, the PSB shows enhanced energy dissipation and deformation resistance compared to conventional ballast. These findings provide a theoretical basis for the structural design and long-term performance assessment of the PPSTB. Full article

In deep geothermal engineering, concrete slabs are prone to thermal cracking. The aggregates and pores are the core influencing factors for this failure behavior. However, existing research methods are unable to accurately capture the microscopic evolution process of thermal cracking and cannot clarify the intrinsic mechanism of how the characteristics of aggregates and pores affect the initiation and propagation of cracks. This limitation restricts the in-depth understanding of the laws of concrete thermal cracking. To address this deficiency, this study employs the discrete element method (DEM) and combines the particle flow program PFC2D to construct a microscopic model of concrete disks. By setting reasonable temperature parameters and thermal load boundaries, a numerical simulation system matching the actual deep geothermal high-temperature environment is established. Three sets of quantitative variables were designed: aggregate particle size (0.003, 0.004, 0.005, 0.006), aggregate volume fraction (0.35, 0.40, 0.45, 0.50), and porosity (0.11, 0.12, 0.13, 0.14). Through controlled variable simulations, the influence laws of each variable on the formation, propagation path, and time evolution of concrete thermal cracks were explored. The quantitative research results show that an increase in aggregate particle size significantly accelerates the generation and propagation of cracks. When the particle size is 0.006, the number of cracks is the highest and the propagation rate is the fastest. The aggregate volume fraction is negatively correlated with the final number of cracks, and 0.50 is the optimal fraction, at which the number of cracks is the smallest. A decrease in the fraction will lead to intensified stress concentration in the cement paste and a sudden increase in the number of cracks. An increase in porosity significantly disrupts the material continuity. When the porosity is 0.14, the bifurcation and connection of cracks are the most significant, while a low porosity of 0.11 can effectively inhibit the overall development process of thermal cracks. In addition, compared with traditional experimental methods and continuous medium numerical simulation techniques, the discrete element method has unique advantages in revealing the internal mechanism of concrete thermal cracking at the microscopic level. It can achieve real-time tracking of the evolution of discrete micro-cracks and the internal stress distribution characteristics. This study enriches the microscopic theoretical system of concrete thermal cracking and provides reliable quantitative references and technical support for the design of thermal crack resistance of concrete in deep geothermal engineering and the optimization of material composition. Full article

In this study, an on-site installation type track slab using glass fiber-reinforced polymer (GFRP) reinforcing bars was developed and analyzed for its structural response to high-speed train loading. Concrete track slabs have the most severe deterioration in track circuit characteristic values due to the conduction influence of existing steel bars. Therefore, a track slab applying an insulator and lightweight GFRP reinforcement by replacing the existing steel bar was proposed from a design perspective. In order to present the validity of the proposed method, a full-size specimen was manufactured and a structural performance test was conducted, and the results were compared and verified through three-dimensional numerical analysis. The results showed that the new orbital slab applying the GFRP reinforcement has satisfactory insulation and provides sufficient structural performance that can replace the existing steel bar. Full article

In this work, the deformation behavior of a long-span steel–concrete composite girder cable-stayed bridge under temperature loads and its subsequent impact on ballastless track systems were investigated. An integrated finite element model (FEM) of the bridge–track system was developed by taking the Taiziping Wujiang River Bridge (with a main span of 300 m) in Chongqing, China, as a case study. The model incorporates composite girders, pylons, stay cables, rails, and double-block slab tracks. Then, the integrated FEM systematically analyzed structural responses to various temperature loading scenario, namely uniform temperature change, differential temperatures among key components (girder, deck, pylons, and cables), and deck–girder temperature difference. The results show that the girder’s maximum vertical displacement linearly correlates with the temperature variations of the composite girder, upper pylon, and cables, with corresponding temperature sensitivity coefficients of 2.3 mm/°C, 2.78 mm/°C, and −5.8 mm/°C. While the ballastless track coordinates well with the composite girder in vertical deformation, the maximum longitudinal relative displacement occurs between rail and track at the ends of the bridge. Moreover, field monitoring data were used to establish a high-precision relationship between ambient temperature and structural temperatures of key components, enabling successful prediction of girder’s vertical deformation. The findings provide a theoretical basis for the control of thermal deformation during the operation and maintenance of similar long-span composite girder cable-stayed bridges. Full article

To address the challenges of winter pavement icing and the disposal of organic waste, this study developed a sustained-release deicing filler utilizing biochar derived from spent coffee grounds (SCGs). The material was synthesized through high-temperature carbonization, followed by physical adsorption of chloride salts and surface hydrophobic modification to control release rates. The study made asphalt mixtures and replaced normal mineral filler with the SCG material by volume at ratios of 0%, 50%, 75%, and 100% to test road and deicing performance. Wheel-tracking tests showed that the additive improved high-temperature stability and dynamic stability went up by 27.04% at the 75% replacement level. Salt dissolving created voids and slightly lowered water stability at high dosages, but all performance numbers still met the current engineering rules. Rutting slab tests at −5 °C showed the 100% replacement mix cut snow coverage to 11.43% in 60 min and proved it works for deicing. Pull-out tests measure the bond strength between ice and pavement at −5 °C, −7 °C, and −9 °C. The SCG deicing material weakens ice sticking and the bond strength for the 100% group at −5 °C was 0.35 kN, which is about 57.8% lower than the control asphalt. The bond strength of the deicing mix at −9 °C was still lower than the normal mix at −5 °C. This big drop in stickiness means the pavement stops ice from packing hard and makes mechanical removal easier. This study shows that the prepared deicing materials exhibit excellent sustained-release performance and snow-melting efficiency while ensuring satisfactory road performance. SCG deicing materials can effectively reduce snow accumulation on road surfaces in winter, lower the difficulty of ice-layer removal, and realize the sustainable utilization of SCGs. Full article

Vibration and noise generated by rail transit systems pose significant constraints on their environmental sustainability. Although extensive research has been conducted by scholars on vibration and noise in rail transit, quantitative studies specifically investigating the influence of train speed on the vibration and noise of elevated rail transit are scarce. Therefore, this study selected a typical elevated section of Wuhan Metro Line 21 and systematically performed field tests to measure the vibration and noise induced by trains passing at speeds of 20, 40, 60 and 80 km·h⁻¹. Based on the test results, the vibration characteristics of the rails, track slab, and bridge structure, as well as the radiation characteristics of wheel–rail noise and bridge structure-borne noise under different speeds, were investigated. The study further explored the impact of train speed variation on the vibration and noise of the elevated rail transit system. The results indicate that the vibration acceleration levels of both the outer and inner rails increase significantly with train speed. Each time the speed doubles, the vibration level rises by approximately 11.5 dB for the outer rail and 10.0 dB for the inner rail. The vibration of the track slab and bridge structure is notably lower than that of the rails. Each time the speed doubles, the vibration acceleration level at various measurement points increases by an average of about 8.5–9.0 dB. Wheel–rail noise is primarily concentrated in the frequency bands around 630 Hz and 3150 Hz. Each time the speed doubles, the trackside noise level increases by an average of approximately 7.2–7.6 dB(A). Noise measured under the bridge shows a distinct peak around 100 Hz, which aligns with the vibration frequency of the bottom slab. Due to the shielding effect of shrubs, noise in the 63–100 Hz frequency band is attenuated at measurement points above ground level. Each time the speed doubles, bridge structure-borne noise increases by about 4.5–5.0 dB(A), representing a lower growth rate compared to wheel–rail noise. The findings of this research are expected to contribute to vibration and noise reduction strategies and support the sustainable development of rail transit systems. Full article

Railway transport is increasingly promoted as a sustainable and low-carbon mode of transportation. However, track-induced vibration propagation remains a significant challenge, particularly in metro systems situated near residential areas, where vibrations can transmit through the infrastructure into nearby buildings, disturbing residents and damaging structures. This study aimed to evaluate the cause of the significantly different vibration impact on nearby buildings caused by two nominally identical adjacent slab tracks on a metro line in Austria. Controlled weight drop tests were carried out in both track directions, and accelerations were measured to characterize wave transmission and energy dissipation. The data were processed using frequency response functions and Short-Time Fourier Transform to extract time–frequency signatures, modal parameters, and propagation delays. A three-dimensional finite element model of the railway superstructure was then calibrated against the experimental modal properties and transfer functions and used to simulate cracking or stiffness loss in the sleeper–slab region. The simulations reproduced the observed increase in slab acceleration and underground strain energy, linking the anomalous vibration transmission to hidden stiffness loss rather than to global design differences. Overall, the study demonstrates that combining impact testing, advanced signal processing, and calibrated finite element modelling provides an effective framework for diagnosing track defects and guiding the design and maintenance of more sustainable, low-vibration urban rail infrastructure. Full article

This study examines a top-chord-free open-web steel-truss composite floor in which the concrete slab functionally replaces the traditional top chord and works jointly with vertical square-tube web members and a square-tube bottom chord. Two scaled specimens—with and without concrete infill in the end shear-bending blocks—were fabricated and tested under static loading. The load–deflection response delineates three stages: elastic, elastic–plastic, and failure. Tests show that infilling the shear-bending blocks does not enhance global mechanical performance. In the elastic range, the mid-span open-web section satisfies the plane-section assumption with a linear strain profile, whereas the solid-web section exhibits a bilinear distribution. A validated ANSYS finite-element model reproduces the measured responses and supports a parametric study showing that span-to-depth ratio, opening-to-span ratio, slab (flange) thickness, and width-to-span ratio significantly affect ultimate capacity and deflection. Design recommendations are proposed: span-to-depth ratios of 11–14 and opening-to-span ratios of 0.04–0.07. An equivalent-stiffness-based simplified linear-elastic deflection formula with a reduction factor is derived, which accurately tracks deflection evolution and enables serviceability-driven selection of web spacing and overall structural depth. Full article