Search Results (1,409)

The combined use of recycled aggregate concrete (RAC) and basalt fiber-reinforced polymer (BFRP) bars offers a promising sustainable and corrosion-resistant solution for reinforced concrete structures. However, the inferior quality of recycled aggregates and the relatively low elastic modulus of BFRP bars can compromise the mechanical and flexural performance of RAC members. To address these issues, hybrid fiber-reinforced recycled aggregate concrete (HFRAC) incorporating polyvinyl alcohol (PVA) and steel fibers was developed, and its mechanical and flexural performances were experimentally investigated. The basic mechanical properties of conventional Portland cement concrete (PC), fiber-free RAC, and RAC with hybrid fiber (HF) contents of 0.6%, 0.9%, 1.2%, and 1.5% were first evaluated. A total of nine beams were subsequently tested under four-point bending to investigate the effects of HF content (0–1.5%) and BFRP reinforcement ratio (0.48–1.98%) on flexural behavior. The results showed that an HF content of 1.2% provided the best performance among the investigated fiber contents at both the material and structural levels. At the material level, compared with RAC, 1.2% HF increased the cube compressive strength, axial compressive strength, elastic modulus and splitting tensile strength by 19.44%, 23.08%, 11.39% and 32.55%, respectively. The incorporation of HF effectively mitigated the mechanical deterioration caused by recycled aggregates, allowing HFRAC to achieve comparable or improved basic mechanical properties relative to RAC. At the structural level, compared with the fiber-free RAC beam, the beam with 1.2% HF exhibited increases of 132.51% and 11.92% in cracking and ultimate loads, respectively, and a 47.9% reduction in crack width, while also demonstrating improved flexural performance compared with the PC beam under the investigated conditions. Three failure modes were observed, namely BFRP bar rupture, balanced failure, and concrete crushing, with balanced failure occurring at a reinforcement ratio of approximately 1.0–1.1%. The hybrid fibers effectively refined cracks through a bridging effect, demonstrating superior crack control compared to increasing the reinforcement ratio alone. This study offers valuable insights into improving the performance of RAC and facilitating the wider adoption of BFRP bars in structural applications. Full article

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

The use of manufactured sand (MS) as a substitute for natural sand or quartz sand in the production of ultra-high-performance manufactured sand concrete (UHPMC) represents a critical approach to alleviating the shortage of high-quality aggregates and promoting low-carbon development. However, after steel fibers and steel rebars are introduced into this material system, the synergistic working mechanism and damage evolution characteristics of the resulting ultra-high-performance manufactured sand-reinforced concrete (UHPMRC) beams under flexural loading remain largely unexplored. Acoustic emission (AE) technology, owing to its high sensitivity to the initiation and propagation of microcracks, enables real-time dynamic monitoring of UHPMRC beams throughout the entire process from the elastic stage to fracture failure, thereby providing an effective means to reveal the internal performance degradation law. Accordingly, this study conducted simultaneous AE monitoring on small-scale reinforced beams under four-point bending and investigated the effects of MS replacement ratios (0%, 50%, 100%) and steel fiber contents (1.0%, 1.5%, 2.0%). Results show that UHPMRC beams with 100% MS replacement and 1.5% steel fiber content achieve optimal performance. Compared to 0% MS specimens, those with 100% MS exhibit superior early stiffness, ductility, and flexural capacity due to the combined effects of steel fibers and MS. Beams with 2% steel fiber content experienced fiber clustering, reducing bridging capability and promoting earlier cracking relative to those with 1.5% fibers. AE energy parameters accurately identified cracking and characterized crack propagation in UHPMRC beams. Increasing MS content raised the proportion of shear cracks while reducing tensile cracks. The highest shear signal proportion occurred at 1.0% steel fiber content. These findings provide a valuable reference for the design of sustainable high-performance reinforced-concrete structures using manufactured sand. Full article

This study investigates the hotspot stress concentration characteristics of rectangular concrete-filled steel tube (CFST) truss joints under bridge deck composite action. Two truss specimens, with and without a reinforced concrete deck, were tested under midspan vertical loading. Nominal stresses and hotspot stresses were measured at typical welded joint details, and finite element models were developed to examine the effect of deck thickness on hotspot stress distribution and potential fatigue-vulnerable regions. The results show that the chord-to-brace intersection corners exhibit much higher hotspot stresses than other locations, indicating that these regions are potential fatigue-vulnerable details requiring attention in fatigue evaluation. Bridge deck composite action significantly changes the load-transfer path and local stress distribution. Compared with the specimen without a deck, the hotspot stresses in the upper joint are markedly reduced, with the maximum reduction at key measurement points reaching approximately 85%. Meanwhile, the controlling hotspot stress location shifts from the chord corner of the upper joint to the brace corner of the lower joint. Increasing deck thickness further reduces the hotspot stresses in the upper joint, whereas the lower joint shows weaker and nonuniform variations. These findings indicate that deck composite action and deck thickness should be considered in the fatigue assessment of rectangular CFST composite truss bridges. Full article

Given that large-scale storage and transportation of liquid hydrogen are key to realizing the hydrogen economy, tank containers have attracted much attention for their flexibility. To minimize evaporation losses, efficient support structures are essential for these liquid hydrogen tank containers. Herein, a carbon fiber-reinforced polymer (CFRP) suspension ring is developed to support the inner vessel of liquid hydrogen tank containers. By using a special resin matrix and optimizing its curing process, the suspension ring capitalizes on a small cross-sectional area and low thermal conductivity, thereby significantly mitigating the cold-bridge heat transferred from the outer vessel to the inner vessel. Experimental results demonstrate that the tensile strength, outgassing rate, and fatigue performance of the suspension ring at both 77 K (liquid nitrogen temperature) and 4 K (liquid helium temperature) can meet the design targets. Notably, its equivalent thermal conductivity was approximately 88% lower than that of a stainless steel structure of the same size. With the integration of this suspension ring into a 40 ft liquid hydrogen tank container, the daily liquid nitrogen evaporation rate was recorded below 0.082%/d. Furthermore, the holding time before the pressure reached 0.14 MPa exceeded 192 h with a 90% liquid hydrogen filling ratio. This work provides key technical support for high thermal insulation, long-endurance liquid hydrogen storage and transportation equipment. Full article

Local scour reduces the lateral restraint provided by surrounding soil and may amplify the impact-induced response of bridge foundations. This study investigates the response of a lattice-shaped diaphragm wall (LSDW) foundation–soil system under predefined local-scour conditions using a three-dimensional explicit finite element model and a nominally rigid steel impactor. A 1:30 reduced-scale configuration was analyzed at impact velocities of 2, 3, and 4 m/s and scour depths of 0, 200, 300, and 400 mm. Increasing impact velocity generally increased wall displacement, velocity, and elastic principal-stress demand, whereas deeper scour reduced the remaining embedment and the restraint provided by the surrounding soil. Relative to the corresponding unscoured conditions, the normalized peak wall-top displacement ratios were 1.28–1.38, 2.01–3.66, and 3.28–5.45 for scour depths of 200, 300, and 400 mm, respectively. The velocity distribution showed an increasingly pronounced rotational contribution as the remaining embedment decreased. Case 9 produced the largest overall response, with a peak wall-top displacement of 398.7 mm and a peak wall-top velocity of 5.2 m/s. Because direct physical validation was unavailable, the results should be interpreted as comparative model-scale trends rather than validated prototype predictions. Full article

Missing bolts compromise the structural integrity of bolted connections in steel bridges and industrial infrastructure. Manual visual inspection remains labour-intensive, subjective, and hazardous in hard-to-reach locations. This study presents a comparative benchmarking framework for unmanned aerial vehicles (UAVs) missing-bolt patch classification using convolutional neural network (CNN), focusing on balancing accuracy and computational efficiency. A UAV-acquired dataset of bolt-centric image patches was developed to evaluate four systematic experimental schemes: (i) a custom lightweight CNN trained from scratch, (ii) the lightweight CNN integrated with Squeeze-and-Excitation (SE) attention blocks across multiple positions, (iii) nine fine-tuned state-of-the-art (SOTA) pretrained CNN backbones, and (iv) SE-enhanced versions of these pretrained models. All architectures were evaluated under a standardised experimental protocol. Results show that the proposed lightweight CNN achieves classification performance comparable to heavyweight pretrained models while requiring significantly lower computational resources. Integrating SE blocks did not improve classification performance for this localised task and, in several configurations, reduced accuracy and training stability. Pretrained transfer learning models achieved high accuracy overall, but their computational complexity limits direct deployment on edge devices and UAV platforms. Grad-CAM visual explanations confirmed that the lightweight CNN consistently focuses on relevant bolt and hole regions. The findings demonstrate that a task-specific lightweight CNN offers a practical balance between inspection reliability and deployment efficiency for automated structural monitoring. Full article

Long-span road–rail steel truss bridges require support-level vibration mitigation without compromising bridge serviceability, train-running safety and comfort, or environmental vibration control. This entirely numerical study establishes coordinated vehicle–bridge interaction (VBI) and vehicle–bridge–soil models for the Wuchang-side $8\times 100 \mathrm{m}$ continuous steel truss approach bridge of the Baishazhou road–rail Yangtze River Bridge. Ordinary steel bearing and anti-vibration spherical steel bearing (AVSSB) schemes are compared under the same track irregularity, train speeds, and one-to-four-line operating cases. Finite AVSSB vertical stiffness produces only limited modal shifts, reduces the impact coefficient by up to 4.4%, and reduces the selected pier lateral acceleration by up to 13.7%, without a discernible deterioration in the derailment coefficient, wheel-load reduction ratio, carbody acceleration, or Sperling comfort index at the reported precision. Frequency selectivity is important in engineering terms because reducing a narrow medium- or high-frequency component does not necessarily reduce the low-frequency-dominated overall ground vibration index. The practical contribution is therefore a system-level screening procedure; an AVSSB may be adopted as a dynamically compatible support modification when selective structural vibration reduction is required, but the speed and multi-line operating scenarios must still be checked independently for environmental vibration compliance. Full article

Accidental web openings caused by impact, corrosion, or conflict-related damage can substantially reduce the strength, stiffness, and stability of steel bridge girders. Although numerous studies have examined beams containing intentionally designed web openings, limited experimental research has systematically compared practical rehabilitation methods for accidental openings in slender-web plate girders. This study experimentally and numerically evaluates several rehabilitation configurations incorporating welded patch plates and transverse stiffeners. Ten slender-web steel girder specimens, each 1800 mm long, 800 mm deep, and 300 mm wide, were tested under monotonic concentrated loading at mid-span. Nonlinear finite element models were also developed to qualitatively examine the principal deformation and instability trends. Relative to the control specimen, the untreated web opening reduced the ultimate load by approximately 43% and exhibited approximately 10% greater deflection at its respective ultimate load. One-sided and two-sided welded patch plates increased the ultimate load of the damaged specimen by approximately 22% and 26%, respectively. Transverse stiffeners increased the ultimate load by approximately 73% while exhibiting substantially lower ultimate-load deflections. The combined use of patch plates and transverse stiffeners provided the greatest improvement, increasing the ultimate load by approximately 101–123% relative to the untreated damaged specimen and substantially reducing lateral instability. The findings demonstrate that effective rehabilitation of slender-web girders requires not only restoration of the interrupted load path but also restraint of web instability. Full article

Distortion-induced fatigue is an important failure mechanism in steel plate girder bridges. Existing studies have advanced the understanding of local stress responses and damage identification of distortion-sensitive details; however, the mechanism by which traffic lane distribution affects distortion-induced fatigue characteristics and governs fatigue damage accumulation remains insufficiently understood. To address this issue, a global–local finite element model was established using ABAQUS 2016 to investigate deformation transfer behavior and fatigue stress responses in a steel plate girder bridge. Longitudinal and transverse load position analyses were conducted to quantify the spatial characteristics of fatigue responses. Furthermore, a lane-distribution-based fatigue damage assessment framework was developed and verified. The results demonstrated that distortion-induced fatigue response is governed by deformation incompatibility, with web gap welds identified as the critical fatigue details under different structural configurations. The transverse displacement at the stiffener end showed a strong correlation with fatigue stress (Spearman coefficients > 0.8). The transverse influence range extended across almost the entire region between the two main girders, indicating that adjacent-lane loads contribute to fatigue damage accumulation. Compared with the single-lane critical load method, the proposed framework better represents fatigue damage evolution under actual lane distributions and captures asymmetric damage between the two girders, with the maximum difference reaching 46.7%. This study provides new insights into distortion-induced fatigue evolution from the perspective of traffic lane characteristics and offers a refined approach for fatigue assessment of existing steel plate girder bridges. Full article

To investigate the Axial–Shear–Flexure Interaction (ASFI) of precast segmental assembled bridge piers, this study proposes a connection system using tapered-sleeve locking steel bar joints and fiber-reinforced concrete (FRC). Four 1:2.5-scaled pier specimens—including single- and double-column configurations, with both cast-in-place and precast segmental designs—were tested under quasi-static cyclic loading. The experimental results show that the precast components exhibited comparable or superior seismic performance, with peak loads in single/double columns being 4% and 5% higher than those in cast-in-place components, respectively; the equivalent viscous damping ratio was 2–4% higher, and residual displacement was reduced by approximately 20%. In addition, an ASFI-based calculation program is developed in Python 3.9 to predict the load–displacement response under combined axial, shear, and flexural actions. The program predicts the peak load of all specimens with errors within 10% but systematically underestimates the peak displacement. Deformation decomposition reveals that shear deformation accounts for 2–7% of the total deformation in single-column piers but increases to 10–17% in double-column piers, confirming the necessity of ASFI modeling for shear-critical configurations. This connection system meets the performance requirement of being “equivalent to cast-in-place,” but the program is only applicable to bearing capacity estimation, and its universality requires further parameter verification. Full article

Existing vibration serviceability criteria for highway bridges were largely developed for conventional steel and concrete structures, and their applicability to lightweight aluminum bridges remains uncertain. This study numerically investigates the dynamic response and vibration serviceability of fully aluminum bridge configurations under moving vehicular loads using ABAQUS. The effects of vehicle speed and span length were examined through midspan acceleration and displacement responses. Serviceability was evaluated using the Wright–Walker acceleration limits and the frequency–deflection criterion of the Canadian Highway Bridge Design Code (CSA S6:25). The results highlight a pronounced vibration sensitivity of the investigated configurations under traffic loading. Full article

This paper investigates the design of aluminium I-beams under major axis bending, fabricated by MIG welding three plates to form the section. The study focuses on beam sizes relevant to pedestrian bridges, with depths ranging from 508 mm to over 2540 mm. The analysis is limited to local buckling behaviour. A total of 600 geometrical material non-linear imperfection analysis-GMNIA and linear buckling analysis-LBA reference numerical results were obtained from validated non-linear shell finite element models. The influence of the heat-affected zone (HAZ) is shown to be pronounced and detrimental to the resistance of welded aluminium beams. Unlike in steel beams, where buckling often governs, local buckling modes in aluminium members may arise but are typically dominated by HAZ-related failure. The effect of strain hardening on the behaviour and resistance of aluminium alloys is examined and compared with current design approaches, which typically assume an idealised plastic plateau similar to steel. The results show that strain hardening significantly enhances resistance and is not captured by existing design methods. The effect of residual stresses in welded aluminium members is also investigated. The results indicate that MIG-induced residual stresses are sufficiently small and have a negligible influence on both structural behaviour and strength. Their effect can be conservatively accounted for by increasing the amplitude of initial geometric imperfections. The study shows that current design recommendations are inconsistent and mostly unsafe for welded aluminium beams bridge sections governed by local buckling. The findings provide improved insight into the behaviour and resistance of such members and contribute to more accurate and efficient design methods. Full article

Aluminium remains relatively uncommon in civil structures; however, its durability and light-weight nature make it an attractive alternative for vehicular bridges. Recent applications use aluminium bridge decks supported by steel girders. However, galvanic corrosion and thermal incompatibility limit full and optimised behaviour. This research explores the use of Bobbin Tool Friction Stir Welding (BTFSW), which improves the welded aluminium behaviour while significantly improving fatigue detail classification, as it is critical for bridges. This configuration optimises material use, reduces structural weight, and supports Accelerated Bridge Construction (ABC) practices by enabling modular prefabrication and rapid installation. The findings highlight aluminium’s potential as a primary bridge material. Full article

WSP was responsible for the design and detailing of Canada’s first GMAW-welded aluminium deck on steel girders bridge for Université Laval. The firm developed welded aluminium panels connected by blind bolts and supported by three steel girders. The 15 m by 8 m structure was fully preassembled for quick onsite installation and designed to support both highway and forest truck loads. Amid post-pandemic procurement and welding challenges, the fabricator, designer, and owner worked closely together throughout construction. While the project experienced delays, quality was prioritised, culminating in a pioneering structure for Canada. This paper explores the construction process, including trials to optimise the 28 mm deep GMAW welds. The fabricator developed an innovative approach for positioning removable backing bars within 10-metre-long hollow extrusions. Non-destructive testing was essential due to the absence of detailed acceptance criteria in current standards. Post-welding deformation control was achieved through several iterations and the post-heating process. The bolting plate method effectively joined hollow aluminium components, and custom features were incorporated to accommodate Université Laval’s research instrumentation. Full article