Search Results (7,526)

Traditional brick masonry buildings in China are commonly constructed using fired clay grey bricks bonded with glutinous rice mortar, forming a unique historical masonry system with significant cultural value. During long-term service, these structures are vulnerable to environmental deterioration, material aging, and seismic actions, resulting in cracking, deformation, and degradation of structural integrity and load-carrying capacity. Carbon fiber-reinforced polymer (CFRP) sheets have been increasingly applied for strengthening masonry structures due to their high strength-to-weight ratio, corrosion resistance, and convenient installation. However, most existing studies on Fiber-reinforced polymer (FRP)–masonry interfaces have focused on conventional masonry systems, while the interfacial bond behavior and load-transfer characteristics between CFRP sheets and traditional grey brick masonry bonded with glutinous rice mortar remain insufficiently investigated. This study investigates the interfacial bond behavior of CFRP-strengthened traditional grey brick masonry through combined experimental testing and numerical analysis. First, uniaxial compression tests were conducted to determine the mechanical properties of glutinous rice mortar and fired clay grey bricks. Subsequently, double-shear tests considering different CFRP bond widths, bond lengths, and interface integrity conditions were performed to characterize the failure modes, force–displacement responses, and interfacial load-carrying behavior. The effects of interface geometric and integrity conditions were considered to evaluate the load-transfer characteristics of the strengthened interface. Based on the experimental results, a finite element model considering interface behavior was established and verified through comparison with the experimental results, which was subsequently employed to investigate the influence of bond width on interfacial stress transfer behavior beyond the experimental conditions. The results show that interfacial debonding accompanied by near-surface masonry damage dominates the failure process of CFRP–glutinous rice mortar masonry interfaces. Increasing the CFRP bond width enhances the interfacial load-carrying capacity and initial stiffness, while the ultimate capacity exhibits an approximately linear relationship with bond width within the investigated range. Numerical analyses further demonstrate that increasing bond width expands the effective load-transfer region, redistributes interfacial stresses, and delays stiffness degradation. These findings improve the understanding of interfacial bond behavior and load-transfer characteristics in CFRP-strengthened traditional masonry systems and provide references for the design and performance evaluation of strengthening applications in historic masonry structures. Full article

The fatigue failure (F/F) test is an important method for evaluating hair strength. In this study, we evaluate commercial European hair after up to four bleaches. F/F-data were directly fitted using a two-parameter cumulative Weibull distribution (CWD) function, described by lifetime index (λ) and shape factor (β). Fibre samples taken from treated tresses (T) exhibited stable F/F behaviour across multiple treatments, while treated single fibres (S) showed early breakage if treated more than twice. We attribute this effect mainly to the liquor ratio during treatment. In this context, we suggest a strategy to estimate a treatment-related apparent decay constant for λ. The constant for T-samples was determined as k_n = 0.095. This is consistent with DSC results in the literature for the denaturation enthalpy. This may indicate an important role for intermediate filaments in fatigue failure. To possibly establish a link with hair breakage during combing, we investigated the properties of the hazard function for T-samples based on β = 0.92. The model calculations indicate that early failure risks are low but increase exponentially with repeated bleaches. The correspondence with the literature results leads to the hypothesis of a relationship between F/F and combing tests. Full article

Pile foundations transmit structural loads to deeper subsoil strata whenever the soil in the vicinity of the ground surface lacks sufficient strength and stiffness to ensure an adequate factor of safety against ultimate failure or warrant settlements to remain below acceptable limits. In many in situ conditions, piles are embedded in layered subsoil medium. In several circumstances, piles are subjected to tensile loading. Large and high-rise civil infrastructure subjected to wind loading, transport infrastructure under horizontal loading due to moving vehicles, offshore structures withstanding wind and wave loading, underground structures subjected to hydrostatic pressure due to buoyancy, etc., are some examples where tension loads are imparted on the supporting piles. The imparted uplift loads in these tension piles are balanced by the negative skin friction induced at the pile–soil interface. In this paper, an analytical model using systematic application of established upper bound shear stress theory to three-layered soil configurations has been developed to formulate the ultimate uplift capacity of tension piles in three-layered soil. The model adopted appropriate correlations for upper bound interface shear stresses in different soils as well as tensile failure of pile material itself. The developed solution was validated by comparing with available experimental results. Thereafter, a case study was performed to study the influence of the variation of pile geometries and relative stiffness on ultimate uplift capacities. Important conclusions were drawn from the entire study. Full article

Conventional concrete pavement materials remain limited in flexural strength, deformability, post-cracking load-carrying capacity, and impact resistance. To address these deficiencies, this study investigates the effects of polymer modification and ultrashort ultrafine steel fiber reinforcement on the static and dynamic mechanical responses and crack evolution of concrete. The results show that polymer modification enhances deformability, while steel fiber incorporation further increases flexural strength and ultimate flexural strain and improves post-cracking load-carrying capacity. Under repeated impact loading, the nominal impact energy input required for initial cracking and final failure increased; in particular, polymer-modified concrete containing 5% steel fibers showed increases of 938.76% in ultimate flexural strain and 8682.63% in the number of impacts to failure relative to ordinary concrete. The matrix and interfacial morphologies observed by scanning electron microscopy (SEM) were consistent with the macroscopic mechanical responses, supporting the interpretation that polymer modification improves matrix and interfacial integrity, while steel fibers contribute to post-cracking load transfer through crack bridging. Overall, the material exhibited high deformability and damage tolerance, indicating its potential for specialized pavement applications. Full article

Rainfall-induced landslides pose a significant threat to communities and infrastructure in the eThekwini Metropolitan Region, South Africa. This paper presents a geotechnical–hydrogeological property zonation and parameterisation framework developed to support future physically based slope stability modelling. Using a weighted sum analysis in a GIS environment, the landscape was subdivided into distinct property zones by integrating lithology, slope gradient, and landform, with weights derived from a fully reproducible renormalisation of a previously published regional frequency ratio (FR) susceptibility model. This procedure provided the foundation for assigning zone-specific parameters, including effective shear strength parameters (c′ and ϕ′) and saturated hydraulic conductivity (Ksat), derived from laboratory testing, borehole pump testing analysis, and empirical relationships. The approach delineated four geotechnical–hydrogeological zones. A correlation of these zones against an inventory of 819 landslides revealed that over 82% of failures have occurred within Zones 2 and 3. While the hydrogeological conditions of these two susceptible zones range from intermediate to low permeability (K_sat = 10⁻⁵ to 10⁻⁸ m/s), which promotes transient pore pressure build-up, their high failure frequency corresponds closely with shared low shear strength (c′ = 5 kPa) and comparatively low effective friction angle (ϕ′ = 27.5–30°). This identifies shear strength as an important predisposing control on instability, relative to the inherently more stable Zones 1 and 4 (c′ = 10–15 kPa, ϕ′ = 30–35°). Consequently, this zonation and parameterisation approach advances landslide hazard assessment by providing a reproducible, model-ready dataset intended for future transient rainfall-infiltration simulations (e.g., TRIGRS), laying the groundwork for physically based early-warning systems, and supporting risk-informed urban development. Full article

The effects of wide-ranging service temperatures on interfacial bond transfer and slip evolution in high-strength concrete-filled steel tube members have not yet been systematically characterized. A test program involving 15 circular specimens was carried out at temperatures between −60 °C and 60 °C with steel tube wall thicknesses of 2 mm, 3 mm, and 4 mm. Particular attention was given to interface failure patterns, slip development, and stress transfer during loading. Cooling markedly enhanced the interfacial resistance, whereas heating produced a moderate reduction. The increase observed at subzero temperatures was smaller than that commonly reported for conventional concrete-filled steel tubes. Bond capacity also declined as the diameter-to-thickness ratio increased because of reduced confinement from the steel tube. Regression of the experimental data produced expressions for ultimate bond strength and the associated slip. A piecewise constitutive relation was then formulated to represent the complete bond–slip process. The proposed relation was implemented in ABAQUS through distributed nonlinear connector elements and temperature-dependent material properties. Numerical predictions showed close agreement with the measured load–slip responses, characteristic loads, and stress distributions. These results provide a modeling basis for HSCFST members exposed to severe cold and large temperature fluctuations. Full article

Mitigating structural failure and improving the fire safety of concrete infrastructure during severe thermal events depends critically on the high-temperature resilience of Portland cement paste. Given the increasing production of Portland blended cements, understanding their high-temperature behavior is crucial for ensuring the safety of building structures. This study investigates the effects of exposure to high temperatures (up to 1200 °C) on Portland cement pastes containing ground granulated blast furnace slag and quartz powder, focusing on their thermal stability and the chemical reactions occurring under these conditions. In situ X-ray diffraction (XRD) with a heating module was employed to observe real-time phase transformations as the temperature increased, supported by ex situ scanning electron microscopic analysis. The results showed changes in the mineralogical composition, with particular attention to the decomposition of calcium hydroxide and the formation of melilite above 900 °C. These transformations suggest thermal reactions between cement hydrate products (calcium silicates and aluminates) in the presence of slag and quartz powder. Mixtures containing quartz powder exhibited increased porosity and phase transformation shifts at lower temperatures, reflecting the combined effects of quartz addition, reduced reactive binder content, and an increased effective water-to-binder ratio. Notably, lower strength-grade cements containing fly ash (additional alumina source) show higher degrees of formation of calcium–aluminate silicate phases such as melilite upon heating. Compared to conventional studies, the novelty of this study lies in the use of an in situ experimental setup, which uniquely identifies the temperature thresholds of chemical changes and the formation of new phases such as melilite in cement–selected slag mixes, while also capturing their recrystallization upon cooling. Full article

In the subsequent backfilling mining method, the composite structure formed by the ore pillar and the backfill is the key element in ensuring the stability of the working face. Its mechanical behaviour directly affects mining safety and ore recovery rates. In order to elucidate the mechanical response and failure mechanisms of rock-like backfill composite structures (RLBCS) under biaxial loading, specimens with different water-to-cement (W/C) ratios (0.5, 0.6, 0.7 and 0.8) for the rock-like backfill were prepared in this study. Biaxial loading tests were conducted, with digital image correlation (DIC) technology employed simultaneously to monitor the evolution of strain and displacement on the specimen surface. The results indicate that the biaxial strength of RLBCS decreases exponentially as the W/C increases. When the W/C exceeds 0.7, the strength reaches a plateau. The strength contribution of the backfill increases relatively. The axial stress–strain curve exhibits four distinct phases. A pronounced bimodal distribution is observed when the W/C exceeds 0.5. The evolution of lateral strain exhibits a transition point where compression is followed by expansion. The threshold for lateral expansion stress exhibits a non-monotonic variation. The modulus of elasticity decreases as the W/C increases. The apparent structural strain ratio exhibits a non-monotonic variation. The failure pattern exhibits marked asymmetry. The rock-like side shows tensile failure. Where the interface is present, this manifests as localised crushing at the top of the rock-like layer, cracking along the interface, and bulging of the backfill. The W/C ratio of the rock-like material governs the failure mechanism of RLBCS. The strain localisation modes in backfill materials are classified into two types: post-peak abrupt and pre-peak gradual. The evolution of interface strain exhibits four distinct stages: an initial abrupt change, cooperative deformation, crack initiation, and post-peak instability. The spatiotemporal evolution of interfacial delamination and the deformation of the backfill was quantified through displacement field analysis. The research findings provide a theoretical basis for the design of underground mining operations. Full article

Three-dimensional (3D) printing technology has become more and more popular in restorative dentistry; however, information regarding the mechanical properties of 3D-printed restorative materials remains limited. The aim of this study was to evaluate the behavior under compressive loading until fracture of occlusal veneers fabricated from two types of 3D-printed resin composites, Saremco Print Crowntec A2 and Voco V-Print C&B Temp A2, intended for permanent and temporary clinical restorations, respectively. The study design involved scanning a first upper premolar typodont tooth, previously prepared to receive an occlusal veneer restoration, followed by the computer-aided design of the occlusal veneers and resin dies and 3D printing, resulting in 20 samples. The cemented restorations were subjected to mechanical testing using a fracture-resistance test at a speed of 5 mm/min, applied until failure. The recorded failure forces ranged between 571 and 970 Newton (N), values that are comparable to physiological masticatory forces. The absorbed energy was calculated as the area under the force–displacement curve using the trapezoidal integration method. The mean energy at failure was 0.301 Joule (J) (Voco) and 0.244 Joule (J) (Saremco), with Voco demonstrating greater toughness. In terms of fracture pattern classification, the 3D-printed resin with a lower filler content presented a more catastrophic failure mode compared with the material with a higher filler content. Fractographic analysis revealed characteristic fracture patterns and failure-specific features. Higher predictability and greater fracture strength were observed for the low-filled material, as indicated by the Weibull analysis. Full article

(1) Background: Repairing fractured provisional restorations may avoid refabrication, but success depends on substrate chemistry, repair protocol, and aging. This study evaluated shear bond strength (SBS) and failure behavior after chairside repair of PEMA-, PMMA-, and bis-acryl-based provisional materials. (2) Methods: In total, 380 specimens were prepared. Repairs used the substrate material, a dedicated repair system, or flowable composite without pretreatment or after a methacrylate repair primer, an MMA/Bis-GMA primer, or a multifunctional methacrylate coating. Half underwent 5000 thermocycles (5–55 °C). SBS was determined using a notched-edge test based on ISO 29022:2013, and failure modes were evaluated. An HC3-robust three-factor model was followed by Holm-adjusted Welch comparisons. (3) Results: A material × protocol × aging interaction occurred (p < 0.001). Homologous repair yielded 17.88–20.35 MPa for PEMA and 25.09–25.30 MPa for PMMA. Pretreatment improved composite repair across substrates. Pre-test failures affected 40.0% of PEMA and 13.3% of PMMA specimens but no bis-acryl specimens. Unprimed flowable composite produced complete pre-test failure with PEMA, low SBS with PMMA, and moderate SBS with bis-acryl. Thermocycling effects were protocol-dependent. (4) Conclusions: Conventional acrylics should be repaired homologously or after chemical conditioning, whereas flowable composite alone may be suitable for minor, non-load-bearing bis-acryl corrections. Full article

To investigate the mechanical response and evolutionary mechanisms of shear-slip rockburst in fractured rock masses, intact, single-fracture, and double-fracture cubic specimens were fabricated using a self-developed synthetic material designed to reproduce pronounced elastic energy storage and rapid brittle failure. Shear-slip tests were conducted under normal stresses ranging from 0.9 to 3.6 MPa. The impact energy index, elastic energy index, and dynamic failure time of the material were 18.0, 9.2, and 140 ms, respectively. Shear stress, shear displacement, and normal displacement were monitored synchronously, while stress-drop events, shear-surface damage, and rock-powder mass were analyzed to clarify the controlling effects of normal stress and the fracture configuration. The results showed that, as the normal stress increased from 0.9 to 2.7 MPa, asperity interlocking along the shear surface was enhanced, resulting in overall increases in the peak and residual shear strengths and progressive suppression of dilation. At 3.6 MPa, all three specimen types exhibited pronounced stress drops, normal contraction, and complete loss of shear-bearing capacity, indicating a transition from stable frictional sliding to crushing collapse dominated brittle instability. The tested specimens suggest that increasing the number of prefabricated fractures may promote deformation localization and shorten the stable post-peak sliding process. At 3.6 MPa, the shear displacements corresponding to complete instability of the intact, single-fracture, and double-fracture specimens decreased from 9.0 to 7.8 and 6.5 mm, respectively, whereas the maximum stress drops increased from 0.28 to 0.62 and 0.90 MPa. These responses were characterized by earlier instability, increasingly concentrated stress-drop events, and larger individual stress drops. With increasing normal stress, the mass of rock powder increased from 11 to 56 g, indicating that shear surface damage evolved from localized fracturing to intensive crushing and grinding. The shear-slip process comprised four stages: compaction adjustment and load-bearing structure formation, elastic shearing and energy accumulation, damage accumulation and crack coalescence culminating in peak instability, and fragment reorganization with post-peak sliding. These findings provide experimental evidence for identifying shear-slip dynamic instability in fractured surrounding rock. Full article

Fiber-reinforced polymers (FRPs) are increasingly adopted in structural rehabilitation due to their high strength-to-weight ratio, corrosion resistance, and ease of installation, making them suitable for extending the service life of reinforced concrete (RC) infrastructure. Studies on shear strengthening with CFRP was early focused on externally boning (EB) showed premature delamination between fiber and concrete which limits the bonding strength. Hence, this study experimentally evaluates the shear strengthening behavior of RC beams retrofitted using inside-groove bonded CFRP and hybrid techniques. A total of seven beam specimens with identical geometry, internal reinforcement layout, and concrete strength were fabricated and tested under four-point bending to generate a well-defined shear-critical region. The experimental program focused on directly comparing bonding configurations while also examining the influence of groove depth (10 mm and 15 mm) and steel anchorage for concrete cover on structural response and failure mechanisms. The strengthened specimens achieved ultimate load increases ranging from approximately 10% to 23% relative to the control beam. Variation in groove depth within the investigated range did not significantly influence shear capacity, indicating that moderate groove penetration is sufficient to develop effective mechanical interlock. Steel anchors were introduced to restrain concrete cover separation and improve confinement of the bonded region and substantially increase peak load, it successfully mitigated premature cover delamination near stirrup locations and altered the governing failure mode. Full article

The inherent trade-off between strength and toughness in structural materials remains a critical challenge. Inspired by the hierarchical architecture of fish scales, this study proposes a novel overlapping helical composite structure. Multi-material three dimensional (3D) printing technology was employed to fabricate single-edge notched bending specimens. Quasi-static three-point bending experiment was conducted to investigate the mechanical performance of a fish scale-inspired structure. The results show that compared to the stiff bulk structure, the bio-inspired design exhibits a 60.4% enhancement in apparent fracture toughness and a 157.5% increase in energy absorption despite a reduction in flexural modulus and strength. The significant improvement may be attributed to the synergistic effects of crack deflection, which transform the fracture mode from catastrophic brittle failure to progressive damage with a stable post-peak deformation stage. Furthermore, parametric studies reveal that both the linear helical angle and its nonlinear gradient distribution critically govern the toughening efficiency. An optimal linear angle of 19° provides the best overall performance, while a nonlinear gradient (e = 1.75) further shifts energy dissipation towards the post-peak deformation stage, achieving a higher toughening efficiency. This work establishes a fundamental understanding of an overlapping helical coupling toughening strategy and provides a promising design route for high-damage-tolerance composite structures. Full article

Transformer winding failures are driven by the cumulative degradation from repeated short-circuit shocks rather than a single extreme event. Current standards rely on static strength checks using as-manufactured material properties, ignoring both thermal aging and load-history effects. To address this gap, we propose a nonlinear fatigue cumulative damage framework that couples a long-term thermal-aging spectrum, converted into an equivalent aging duration and a global property correction, with a micro-spectrum of individual short-circuit events, discretized into an eight-level variable-amplitude stress history. The resulting six-step workflow shifts the paradigm from passive strength checking to proactive life management, offering utilities a physics-informed framework for estimating the residual fatigue life of aging transformers. Full article

A symmetric integrity seal is worth exactly what its key is worth. Any party holding the keyed-hash (HMAC) key of an Internet of Things (IoT) audit trail can forge a record, re-seal a modified one, and leave no cryptographic trace, so an HMAC-sealed log establishes nothing to an external auditor or regulator beyond the honesty of the operator itself. This paper separates integrity from evidential strength and decomposes the latter into six properties—integrity, authenticity, non-repudiation of the anchored history, third-party verifiability, temporal upper-bounding, and bounded completeness—stating for each what a cryptographic mechanism can and cannot establish. It then presents the Ledger-Anchored Compliance Transformation Layer (LA-CTL), a two-tier architecture for Ambient Assisted Living (AAL) in which edge gateways seal each record with HMAC-SHA256 for operator-side verification and anchor RFC 6962 Merkle roots over sealed batches on a Byzantine fault-tolerant permissioned ledger shared with the auditor and the regulator. Records remain off-chain, preserving erasability under the General Data Protection Regulation. All cryptography is real; the consortium is evaluated both in a seeded network simulation and as four validator processes over sockets under LAN and emulated WAN conditions, at steady load and under the failure of a backup and of the primary. Anchoring is batch-priced rather than record-priced: on-chain state falls to 0.57 bytes per record at batch size 1024, while inclusion proofs grow logarithmically to at most 330 bytes. Holding the Merkle batching constant and varying only the publication substrate shows that most detection capability comes from the batching rather than from the ledger—a single-notary log matches the consortium on tampering, insider re-sealing, deletion and reordering—and that the quorum is distinguished on one attack: compromise of the publisher, which is the attack an operator-selected notary cannot withstand. The insider re-seal that the symmetric baseline accepts by construction is detected in all 10,000 trials. What the anchor does not give is stated with equal care: a commit bounds when the committed bytes existed, not when the event they describe occurred. Full article