Search Results (178)

Seismic assessment of reinforced concrete structures requires characterization of member and connection behavior under large cyclic deformations. Moment-resisting frames are widely adopted in seismic regions, but meeting code requirements is problematic when beams are reinforced with prestressing steel strands because their ultimate elongation differs substantially from that of conventional high-ductility reinforcement (e.g., ε_u,k ≈ 3.5% for Y1770S7 strands versus ε_u,k ≈ 7.5% for B500C rebars). This study reports the findings of an experimental program conducted on reinforced concrete beam–column joints (NGS), representative of moment-resisting frame systems typically employed in seismic regions. To explore innovative structural solutions, a biomimetic design strategy was adopted, drawing inspiration from the micromechanics of Picea abies (Norway spruce). Five half-scale (1:2) specimens were subjected to quasi-static, displacement-controlled cyclic loading following the ACI 374.2R-13 (ACI T.1.1R-01) protocol, and their performance was evaluated against prescribed acceptance criteria. Adding one longitudinal steel strand and partially anchoring it in normal concrete (NGS2) and in biomaterial-adapted grout (NGS4) did not increase the amount of dissipated energy when compared to the reinforced concrete conventional solution (NGS1). Moreover, the effects of replacing the rebars with partially anchored steel strands (NGS3 and NGS5) proved to be negative. Full article

Carbon-fiber-reinforced polymer (CFRP) reinforcement is a potential alternative to steel in corrosive environments. However, CFRP is elastic without ductility, and the seismic performance of CFRP-reinforced concrete (RC) columns is inadequately understood. This study characterizes the intrinsic seismic response of concrete columns reinforced with CFRP cable-type bars and spirals under recorded near-fault ground motions. Three reference steel-RC columns are designed as seismic-resistant, non-seismic-resistant, and with post-cracking stiffness equivalent to the CFRP-RC column. The CFRP-RC and seismic-resistant steel-RC columns were tested under cyclic loading, and the results validated finite element (FE) models. Validated models simulated four columns under cyclic loading, and under 11 near-fault records matched to a capacity-derived elastic target spectrum. The results, bounded by selected ground motions and material constitutive models, show that: (1) The tested CFRP-RC column dissipated about 50% less energy than the steel-RC reference; (2) No material-level failure criterion was met under the suite, although peak base shears exceeded the nominal quasi-static capacities; (3) The CFRP-RC column developed the largest transient drift but minimal residual drift, whereas the steel-RC columns limited transient amplitude via hysteretic dissipation yet accumulated permanent offsets; (4) Response of the CFRP-RC column depends on ground motion energy delivery characteristics: concentration, symmetry, and duration. Full article

Discrete-Variable Quantum Key Distribution (DV-QKD) provides a mechanism for establishing secret keys between legitimate parties using quantum-state transmission and authenticated classical post-processing. In this work, the underlying quantum layer follows a biased-basis decoy-state BB84 model using phase-randomized weak coherent pulses, while additional implementation-level mechanisms are integrated to support Cyber-Physical System (CPS) communication. Exponential Double Delta Encoding-based Merkle Tree (EDDE-MT) is employed as a receiver-side detection-record integrity mechanism for detecting deletion, insertion, reordering, or modification of records relative to an authenticated committed detection-event batch. It does not establish the completeness of the original TCSPC acquisition, detect records omitted before commitment, detect physical photon loss, or increase the information-theoretic secrecy of the QKD key. Time-Correlated Single Photon Counting (TCSPC) is used for detection-event and timing acquisition, while 2’s Complement Cyclic Redundancy Check-based Low-Density Parity Check (2CCRC-LDPC) supports error reconciliation. Following privacy amplification, the legitimate parties retain matching copies of the distilled QKD key locally. Discrete Variable Quantum Mellin Transform Cryptography (DVQMTC) uses fresh, non-reused segments of this privacy-amplified key for application-layer payload protection; the Mellin-transform component is treated only as implementation-level preprocessing and not as a cryptographic key-generation mechanism. Side-channel monitoring is performed using Gini Cramer’s V Correlation-Stationary Wavelet Transform (GCVC-SWT), Helical Valley-Principal Component Analysis (HV-PCA), and an Entmax-based hyperbolic Tangent exponential Linear Unit-Bidirectional Long Short-Term Memory (E-TeLU-Bi-LSTM) classifier. On the AES-HD benchmark, E-TeLU-Bi-LSTM achieved 99.24% classification accuracy; this value represents benchmark-level classification performance and is not interpreted as experimental validation of physical side-channel protection in a deployed DV-QKD system. Frequency Division Multiple Access (FDMA) and the Halton Quasi-Sequence-Invasive Weed Optimization Algorithm (HQS-IWOA) are further incorporated as classical network-resource segmentation and load-management mechanisms and do not modify the composable QKD security bound. The contribution of the work is therefore positioned as a system-level engineering integration of QKD key establishment, detection-record integrity, reconciliation, application-layer data protection, side-channel monitoring, and network-resource management for CPS. The information-theoretic secrecy claim remains restricted to the underlying finite-key decoy-state BB84 procedure under the stated security assumptions; no new QKD security theorem, formally new cryptographic primitive, or experimentally validated physical quantum communication capability is claimed. Full article

To investigate the correlation between construction dimensions and seismic performance of Song-dynasty official and local timber structures, two scaled models were subjected to horizontal cyclic quasi-static loading tests. One model is the Goddess Mother Hall of Jinci, and the other is the 7th-grade timber frame described in Yingzao Fashi. The models have similar vertical-layer proportions but differ in bay width, E-fang cross-sectional dimensions, Dou-gong cai-height, and column-top tenon cross-sections. The relative ratio method was used to mitigate the effects of material and scale differences and to focus on the relative contributions of the column-frame and Dou-gong layers to the overall frame. For the Goddess Mother Hall model, which is characterized by a wide bay and thin E-fang, the ratio of the equivalent viscous damping coefficient of the column-frame layer to that of the overall frame remains above 1.0, indicating greater energy dissipation efficiency than the overall structure. However, its stiffness degradation is more pronounced under high vertical loads. The enlarged column-top tenon cross-section and slightly reduced cai height produce a stable increase in the stiffness contribution of the Dou-gong layer, whereas its relative contribution to energy dissipation proportion is smaller than that in the Yingzao Fashi model. The results show that dimensional differences are associated with distinct trends in the stiffness and energy dissipation of the column-frame and Dou-gong layers and that these trends vary with vertical load. This study reveals the coupling relationship between dimensional adjustments and structural performance in official norms and local construction practices, providing a basis and directions for further research on the mechanical effects of dimensional variations in ancient timber structures. Full article

Plastic hinge relocation can reduce damage within reinforced concrete beam–column connections by shifting inelastic deformations away from the connection region. This study experimentally investigates a relocation concept for precast reinforced concrete assemblies based on enlarged beam cross-sections. Four 1:3.5-scale specimens were subjected to quasi-static cyclic loading: one reference specimen and three specimens with increasing relocation distances. The hysteretic response, stiffness degradation, energy dissipation, damage distribution, beam rotation, and concrete surface strain were evaluated. In all relocated specimens, the measurements confirmed that inelastic deformations concentrated near the intended hinge location, while no visible shear damage developed at the beam–column interface. Compared with the reference specimen, the relocated configurations developed 86–175% higher yielding forces and 30–62% higher peak forces, mainly because the reduced effective lever arm increased force and moment demand. They also accumulated more than twice the hysteretic energy over their completed loading histories and showed higher minimum equivalent viscous damping after yielding. The results demonstrate that enlarged beam cross-sections can control the location of inelastic deformation; however, increasing relocation distance also increases force, rotational, and localized deformation demands at the relocated critical section. Full article

SBS-modified asphalt is widely used in high-grade pavements for its excellent rutting and fatigue resistance; however, how its friction behavior evolves under submerged conditions with surface distress remains poorly understood. To address this gap, we developed a rubber–asphalt friction tester to characterize quasi-static rubber–asphalt friction under submerged conditions with three typical distresses: pothole, crack, and surface void. Our results show that friction increases with roughness, load, and water temperature, but degrades progressively under cyclic loading. Among the three distresses, surface void offers the most stable friction performance, whereas pothole exhibits the largest friction loss under repeated loading, identifying them as high-priority repair targets. The positive temperature–friction correlation further implies that wet-skid risks are higher at lower temperatures, providing a basis for seasonal maintenance scheduling. Three-dimensional wear analysis reveals distinct mechanisms: pothole causes localized deep-pit wear, while surface void generates uniform roughening, explaining their contrasting durability. These findings directly support distress prioritization, friction-performance evaluation, and maintenance planning for SBS-modified pavements in rainy environments. Full article

Steel–concrete composite beams offer significant advantages in long-span, heavy-load, and prefabricated construction; however, the concrete slabs are prone to tensile cracking under negative bending moments. To enhance cracking resistance, uplift-restricted and slip-permitted (URSP) perfobond rib (PBL) connectors were adopted with a cast-in-place high-performance concrete (HPC) topping. Five composite beam-steel column joint specimens were tested under quasi-static cyclic loading. The test variables included connector type, cast-in-place concrete type, and reinforcement grade. In addition, refined numerical simulations were conducted on the test specimens. Both test and numerical results show that: (1) The combined application of URSP-PBL connectors and HPC enhanced the cracking resistance of the composite beam, with the initial cracking load and corresponding cracking displacement increased by approximately 50% compared with the control specimen. (2) The ultimate flexural capacity of the composite beams under negative moments showed limited sensitivity to the type of cast-in-place concrete topping and the reinforcement grade within the tested range. (3) The use of URSP-PBL connectors improved the flexural stiffness of the composite beams. (4) The URSP-PBL specimens showed good energy dissipation capacity under cyclic loading, which was further improved with the addition of HPC in the topping. Within the tested range, the reinforcement grade showed limited influence on this performance. This study provides a scientific basis for the crack control design and engineering application of long-span composite beams. Full article

Welded reinforcement cages (WRCs), which connect longitudinal reinforcement and stirrups through welding, have attracted increasing attention for industrialized construction of reinforced concrete (RC) structures. However, the welding process may introduce heat-affected zones, residual stresses, and local metallurgical changes in reinforcing bars, raising concerns regarding the potential influence of welded longitudinal-bar-to-stirrup connections on the seismic performance of RC bridge piers. This study experimentally investigates this issue through quasi-static cyclic tests on two large-scale RC bridge pier specimens with identical reinforcement layouts but different reinforcement connection methods. One specimen adopted conventional tied connections between longitudinal reinforcement and stirrups, whereas the other employed welded connections. The seismic responses of the specimens were evaluated in terms of failure mode, hysteretic behavior, skeleton curve, strength, ductility, stiffness degradation, energy dissipation, residual displacement, and strain development. The results showed that both specimens exhibited flexure-dominated failure with similar crack propagation and concrete-cover spalling characteristics. The differences in yield and peak strengths were within 5%, and the cumulative energy dissipation differed by only 2.1%, indicating comparable global seismic performance. The welded specimen exhibited a slightly larger ultimate displacement (12.8%) and ductility coefficient (9.4%), while the stiffness degradation characteristics remained nearly identical. Although several weld spots detached during the post-peak loading stage, no fracture or necking of the longitudinal reinforcement was observed, suggesting that the adopted welding procedure did not adversely affect the cyclic deformation behavior of the reinforcement. Within the scope of the tested specimens, the results demonstrate that welded longitudinal-bar-to-stirrup connections can maintain the seismic performance of RC bridge piers and provide experimental evidence for the potential application of WRCs in industrialized bridge construction. Further studies involving additional specimens and broader design parameters are required to validate the general applicability of these findings. 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

This study presents a standalone yarn-level assessment of the mechanical and functional durability of polymer-encapsulated electronic yarns (E-yarns) for wearable electronic textile applications. The investigated E-yarns consisted of miniaturised electronic components soldered onto fine conductive wires, protected by polymer encapsulation, and enclosed within braided textile yarn structures. This heterogeneous architecture enables textile-compatible functionality but creates local regions that may be susceptible to damage under various deformation modes. E-yarns incorporating light-emitting diode, photodiode, and resistor components were evaluated under cyclic bending fatigue, torsional fatigue, quasi-static tensile loading, and wash durability conditions. Electrical measurements were used to monitor functional degradation and failure, while X-ray imaging, scanning electron microscopy and finite element analysis were used to examine structural damage, failure localisation, fracture surface morphology, and local stress and strain distribution. The results show that E-yarn durability depended on the imposed loading condition, with distinct mechanical and functional responses observed across the different test modes. The polymer-encapsulated region emerged as a mechanically important feature of the E-yarn architecture, particularly at transitions between encapsulated and non-encapsulated regions. By addressing multiple deformation and loading conditions at the standalone yarn level, this work provides a systematic reliability assessment of polymer-encapsulated E-yarns, enabling intrinsic failure mechanisms to be distinguished from textile integration effects and supporting the development of more reliable yarn-based electronic textiles. Full article

As an innovative structural system aligned with construction industrialization, prefabricated Steel-Reinforced Concrete (SRC) structures are characterized by high load-bearing capacity, efficient material utilization, and rapid construction. In this study, the mechanical behavior, failure mechanisms, and ductility characteristics of a prefabricated SRC multi-floored grain warehouse frame were investigated through quasi-static cyclic loading tests. To complement the experimental program, high-fidelity numerical models were developed using Abaqus, incorporating concrete plastic damage and steel material nonlinearity. The simulation results were rigorously validated against the experimental data. The findings indicate that the specimens exhibited typical shear failure modes with full hysteretic loops, demonstrating substantial energy dissipation capacity (equivalent viscous damping coefficient of 0.261). Notably, the results of the parametric study indicate that the integration of wall panels can significantly increase the load-bearing capacity and lateral stiffness of the frame system. The ductility of the samples was excellent, with displacement ductility coefficients ranging from 3.1 to 3.7. The ultimate inter-story drift angles at failure (1/49–1/38) substantially exceeded the code-specified limit (1/50), indicating robust collapse-prevention capacity. The numerical results strongly agreed with the experimental observations in terms of the hysteretic behavior, failure patterns, and skeleton curves, confirming the reliability of the modeling strategy for subsequent seismic performance analyses and parametric evaluations. Full article

Precast concrete (PC) structures are increasingly adopted in building construction for their sustainable construction advantages. However, theoretical models for seismic design of precast concrete walls with concrete-filled steel tubular (CFST) elements remain limited. The lack of such models hinders the performance-based seismic design and resilience assessment of these hybrid structures. This study investigates the seismic mechanism and develops a restoring force model for precast concrete superposed shear walls with CFST end columns (PCSSWEC). A refined three-dimensional finite element model was established using ABAQUS and validated against quasi-static cyclic test results of three full-scale specimens. The four-stage loading mechanism—elastic, wall cracking, elastoplastic yielding, and ultimate failure—was revealed, with the precast–postcast concrete interface identified as the primary weak link governing post-peak strength degradation. Comprehensive parametric studies examined the influence of shear span ratio (λ = 0.75–3.25), axial compression ratio (n_a = 0.1–0.6), steel tube width-to-thickness ratio (B/t = 20–80), and concrete strength (C30–C60) on seismic performance. Results indicate that intermediate walls (λ = 1.75–2.25) exhibit optimal ductility, and a steel tube with B/t = 40–60 provides a balanced combination of strength and deformation capacity. A tri-linear backbone curve model with explicit formulae for equivalent stiffness and load capacity was developed, along with modified Clough-based hysteretic rules incorporating stiffness degradation through a common yield-point approach. Validation against experimental and numerical results demonstrates reliable model performance for primary structural parameters: lateral load bearing capacity and ultimate drift ratio are predicted within ±10%, while yield load and ductility predictions show larger scatter due to inherent challenges in cyclic behavior characterization. The proposed restoring force model provides a practical tool for performance-based seismic design and resilience assessment of precast concrete buildings. Full article

Numerous existing RC frame buildings in China suffer from seismic deficiencies. This paper proposes a novel Π-shaped connector connection joint for the rapid strengthening of existing beam–column joints: steel plates are wrapped around existing columns, and Π-shaped connectors are welded to link new beam reinforcement. Quasi-static cyclic loading tests were conducted on one RC reference specimen and three strengthened specimens. The strengthened joints showed varying performance—two specimens (JGJ1 and JGJ2) exhibited peak loads below the RC reference, while the best specimen (JGJ3) achieved 9.8% enhancement in peak load and a nearly threefold increase in cumulative energy dissipation. The failure mode transitioned from brittle concrete crushing in the RC specimen to weld cracking and bolt fracture in the strengthened joints, thereby preserving the integrity of the core concrete. Finite element models were established using ABAQUS and validated against the test data. A parametric study investigated the effects of bolt quantity, beam and column dimensions, concrete strength, and steel plate thickness. The FE results indicate that increasing beam height from 400 mm to 450 mm yields the most significant improvement, with peak load increasing by up to 15.59% relative to the base parametric model. Favorable seismic performance was achieved with column concrete grade C50, beam concrete grade C40, steel plate thickness of 6 mm, eight bolts, and connector thickness of 6 mm. The proposed connection provides a potential strengthening alternative for existing RC frame structures. Full article

Reinforced concrete (RC) infilled frames are widely used structural systems; however, seismic design provisions often idealize masonry infill as non-structural, leading to uncertainty in performance assessment. This study experimentally and numerically investigates the role of unreinforced masonry infill in RC frames, focusing on load-transfer mechanisms, strain evolution, and energy redistribution. Two 2/3-scale single-bay, single-storey RC frames (bare and fully infilled) were tested under constant axial load and quasi-static reversed cyclic lateral loading. Reinforcement strain gauges were used to capture local deformation demands, and a nonlinear macro-model was developed and validated against experimental results. Results show that the presence of masonry infill significantly increases ultimate strength, initial stiffness, and energy dissipation capacity, in comparatively more brittle post-peak cyclic behavior and accelerated stiffness degradation that leads to more abrupt post-peak degradation. Strain measurements provide clear evidence of a staged interaction mechanism: at low drift levels, the infill governs lateral resistance through diagonal compression strut action, limiting reinforcement demand in the frame; with increasing drift, progressive cracking and crushing of the infill promote a gradual transfer of forces to the RC frame, reflected by increasing reinforcement strains and stiffness degradation. At higher drift levels, the system transitions to frame-dominated behavior with localized strain concentration and shear failure at column bases or joints. These findings demonstrate that infill significantly modifies structural response and highlight the importance of incorporating strain-based mechanisms in the seismic assessment of infilled RC frames. Full article

To investigate the influence of dry connection methods on the seismic behavior of assembled composite walls, four assembled composite walls were designed and tested. Various dry connection techniques were adopted for the horizontal interfaces, namely sleeve grouting connection, welding connection, box connection, and bolted connection. The failure process, failure mode, bearing capacity, rigidity, steel bar strain, and energy absorption performance of the specimens were investigated through quasi-static cyclic loading tests. The results indicate that all types of connectors can effectively transfer loads and satisfy the conceptual design principle of “strong joint and weak component”. The damage evolution of the specimens is essentially identical, and the limiting drift angles all exceed 1/90. In addition, the shear resistance of the specimens with different connection methods is preliminarily analyzed and estimated. Full article