Search Results (510)

In this study, the seismic vulnerability of the Ferdowsi School building in Tabriz is investigated. The research began with comprehensive fieldwork, during which exploratory surveys and in-depth technical inspections of all structural components were performed. Experimental testing of prismatic masonry specimens was carried out to evaluate their mechanical characteristics, and the resulting properties were then incorporated as input parameters into the numerical model. The seismic vulnerability assessment was then carried out using nonlinear static (pushover) analysis, applying a lateral load pattern proportional to the first vibration mode of the structure. For numerical simulation, the building was modeled in the ABAQUS finite element software using the macro-modeling technique. The results of the nonlinear static analysis indicated that the building does not possess sufficient load-bearing capacity at the target displacement. Damage was primarily concentrated in the form of cracking in the masonry walls as well as in the dome-shaped sections of the roof, requiring the implementation of a seismic retrofitting scheme to enhance the structure’s seismic performance. To rehabilitate the structure, horizontal and vertical reinforced concrete beams were introduced as confining elements for the masonry walls and subsequently applied in the strengthening project. Furthermore, due to the presence of a domed roof at the first-floor level, it was strengthened using FRP composite materials to enhance tensile capacity and ductility. At the second-floor level, where the roof structure is made of timber elements, a steel cable system was employed to improve its strength and diaphragm action. As for the third-floor timber truss roof, the connections were upgraded and reinforced to provide reliable force transmission and to maintain the overall integrity of the structural system. Following the implementation of the retrofitting measures, the structural model was re-analyzed using nonlinear static analysis. The results demonstrated that the proposed strengthening scheme successfully increased the structural capacity up to the target displacement level and satisfied the intended performance requirements. In the final section of the paper, the implementation details of the retrofitting interventions, as well as the practical experiences gained during the implementation process, are presented and discussed. Full article

In this paper, an innovative T-stub connection with square-neck one-side bolts (TS-SNUBC) is developed to improve the bearing capacity and construction reliability of the box column-H beam joint. Twelve T-stub specimens, considering variations in bolt type, flange thickness, and bolt hole orientation, were designed and tested under uniaxial tension. The failure modes, load–displacement responses, ultimate load-bearing capacities, and key quantitative mechanical indicators (initial stiffness, ductility index and cumulative energy dissipation) of the specimens were evaluated. The results indicate that all specimens failed due to the yielding of the thin flange. Specimens with conventional bolts demonstrated the highest load-bearing capacity, followed by those with TS-SNUBC and then slotted one-side bolts. Increasing the thin flange thickness significantly improved the ultimate bearing capacity of the TS-SNUBC specimens. Notably, TS-SNUBC specimens with thin flange thicknesses below 10 mm experienced tear-out failure. Furthermore, specimens with horizontally oriented bolt holes exhibited higher load-bearing capacity than those with vertically oriented holes. A thin flange thickness above 10 mm ensures high initial stiffness, and TF12H has a stiffness of 32.00 kN/mm. Ductility gradually reduces with the growth of thin flange thickness. Energy dissipation decreases sharply when the thin flange is thicker than 10 mm. The joint with 16 mm thick flange, 8 mm thin flange and horizontally arranged square-neck one-side bolts presents the best comprehensive performance. The proposed TS-SNUBC shows favorable bearing performance and initial stiffness, offering a promising solution for reliable and efficiently constructed connections between box columns and steel beams. Full article

Near-fault pulse-like ground motions (NFPLGMs) impose concentrated energy demands that can severely damage bridges, yet their scarcity and the influence of structural parameter uncertainties are often neglected in seismic fragility assessments. This study proposed a synthesis method for NFPLGMs by superposing low-frequency pulse components (extracted via the Gabor wavelet transform and low-pass filtering) with high-frequency stochastic components based on an evolutionary power spectrum. A three-span reinforced concrete bridge was modeled in OpenSeesPy, and Incremental Dynamic Analysis (IDA), together with a quadratic response surface model, were used to plot seismic fragility curves. The damping ratio (ξ), elastic modulus of steel reinforcement (E_s), yield strength of steel reinforcement (f_y), diameter of longitudinal reinforcement (D), and peak ground acceleration (PGA) were treated as random variables. Sensitivity indices were computed using Monte Carlo sampling (n = 10,000). Results show that ξ most strongly affects the displacement ductility ratio of the bridge pier (u_d) (variation of up to 32.6%), while E_s dominates the shear deformation of the bridge bearing (d) (variation of up to 43.8%). Neglecting structural parameter uncertainties overestimates median PGA thresholds (m_R) for different damage states by 1.5%–36.1%, and replacing NFPLGMs with ordinary ground motions overestimates seismic capacity by 1.7%–36.6%. The bridge bearing is consistently more vulnerable than the pier, with a collapse probability of 0.9566 at PGA = 1.0 g. These findings highlight the necessity of incorporating both NFPLGM characteristics and structural parameter uncertainties into bridge seismic fragility assessment. On the other hand, when seismic retrofitting of bridges is carried out using coating materials, priority should be given to more vulnerable components, such as bridge bearings, to improve the utilization efficiency of limited resources. Full article

The seismic fragility of reinforced concrete (RC) bridge piers is critical for urban rail transport systems, as severe pier damage may interrupt post-earthquake operation and threaten network safety. Compared with conventional highway bridge piers, urban rail transport RC solid piers usually have lower axial load ratios, larger cross-sections, and stricter serviceability requirements. However, the combined effects of geometric parameters, reinforcement detailing, and material strength on their cyclic behavior, dynamic response, and seismic fragility remain insufficiently understood. To address this issue, seven 1/4-scale RC solid pier specimens were tested under quasi-static cyclic loading to examine the effects of pier height, transverse reinforcement ratio, and longitudinal reinforcement ratio on damage evolution, hysteretic response, skeleton curves, and energy dissipation. A fiber-based OpenSees model considering bond-slip effects was then established, validated against the tests, and extended to a full-scale prototype pier for parametric analysis. The effects of aspect ratio, axial load ratio, longitudinal reinforcement ratio, stirrup ratio, steel yield strength, and concrete strength were evaluated under cyclic loading and nonlinear dynamic time-history excitations. An incremental dynamic analysis-based probabilistic seismic demand model was further developed using 30 near-fault ground motions, with peak ground acceleration as the intensity measure and displacement ductility as the engineering demand parameter. The results showed that increasing the aspect ratio changed the failure mode from flexure-shear-dominated to flexure-dominated behavior, increasing the ultimate displacement from 122 mm to 155 mm while reducing the peak lateral strength from 263 kN to 248 kN. Increasing the longitudinal reinforcement ratio improved both peak strength and ultimate displacement, from 226 kN to 262 kN and from 120 mm to 160 mm, respectively. The numerical results indicated that aspect ratio, axial load ratio, and longitudinal reinforcement ratio had more pronounced effects on seismic demand and fragility than stirrup ratio. Increasing steel yield strength generally reduced seismic fragility, whereas increasing concrete strength enhanced lateral resistance but did not necessarily improve fragility performance. These findings suggest that the seismic performance of urban rail transport RC solid piers should be evaluated by combining cyclic response, dynamic demand, and fragility-based performance, rather than by maximizing any single design parameter. Full article

Achieving adequate load capacity and ensuring ductile behavior are crucial for reinforced-concrete knee joints to prevent a complete structural collapse if an adjacent member fails. The reinforcement detailing plays a critical role in achieving these factors. In this study, the performance of a knee joint under closing moments was analyzed using innovative truss-shaped reinforcement and simplified mechanical joints, in comparison to traditional reinforcement detailing, through four large-scale specimens. The findings showed that incorporating a truss-shaped reinforcement system with the suggested detailing effectively redistributed stresses in the knee-joint area and decreased stress concentration at the bent-bar zone, thus helping to prevent premature joint failure when compared to conventional specimens. Overall, the proposed system shifted the failure mode towards a highly ductile response. Furthermore, the suggested specimen experienced significant increases in both the yield load and the ultimate load, with the yield-load boost ranging from around 29.5% to 70.5%, and the ultimate-load increase ranging from 20% to 81%. Additionally, the proposed reinforcement system exhibited notably higher displacement capacity, with increases ranging from 88% to 347%. The proposed specimen also showed a considerable enhancement in displacement ductility, with an increase of roughly 160% to 382% relative to traditional specimens. The results matched well with the created analytical models confirming the effectiveness of the proposed load-transfer system. Full article

Four-point bending tests were conducted on precast ultra-high-performance concrete (UHPC) segmental beams reinforced with unbonded prestressing tendons. A nonlinear finite element model was established and rigorously validated against the experimental data to simulate their flexural behavior. The experimental results show that compared with monolithic beams, the segmental beams experience a slight reduction in flexural capacity of 9.22% and 12.44% for the double-joint and triple-joint configurations, respectively. Nevertheless, the segmental beams possess greater ductility reserves; specifically, their average peak displacements increased from 9.83 mm for the monolithic beams to 11.60 mm and 14.78 mm for the double-joint and triple-joint beams, respectively, demonstrating substantially improved ductility. Based on the validated finite element model, extensive parametric analyses were performed. The numerical results indicate that concrete strength and steel strand reinforcement ratio significantly enhance the load-carrying capacity. Furthermore, shifting the joint positions away from the loading points increases the beam’s bending capacity, though this enhancement aggressively flattens out beyond a critical distance threshold of 0.25 L (L is the effective span). Finally, segmental beams with shear-resistant keyed joints exhibit higher overall stiffness and ultimate load-carrying capacity compared to those with plain flat joints. Full article

Hysteretic energy, a critical component of seismic input energy, is predominantly dissipated through the hysteretic behavior of structural members in most conventional structures. The motivation is to establish the conditional probabilistic model of normalized hysteretic energy of the structure after determining its displacement, thereby facilitating the estimation of the Park–Ang damage index. This study develops a probabilistic model for normalized hysteretic energy conditional on the ductility ratio. Three macroscopic hysteretic models, representative of the hysteretic behavior of distinct structural types, are employed to quantify the effects of ground motion characteristics (e.g., magnitude, distance, pulse, duration, and site conditions) and structural properties (e.g., post-yield stiffness and damping ratio). The findings reveal that a lognormal distribution effectively characterizes the normalized hysteretic energy. Among the investigated parameters, ground motion duration leads to a significant influence on the distribution of normalized hysteretic energy (maximum difference up to 30%). To facilitate practical applications, a set of predictive expressions is proposed to estimate the mean and standard deviation of normalized hysteretic energy. The resulting conditional distribution reproduces the empirical distribution derived from the original data, with an average error of approximately 5%. Using established expressions, the required ductility capacity under specified performance objectives can be probabilistically determined in seismic design. Moreover, the established distribution can be used to determine the potential hysteretic energy of the structure for assessing its damage state after an earthquake, as demonstrated through a full-scale shaking table test. Full article

To investigate the effect of crack geometry on tensile deformation and strain localization in X46 pipeline steel thin-walled tubes, uniaxial tensile tests were conducted on specimens containing prefabricated cracks with different sizes, types, and orientations, and full-field strain evolution was characterized by digital image correlation. The material exhibited a favorable strength-ductility balance, with an average yield strength of 324 MPa, an ultimate tensile strength of 553.5 MPa, and an elongation of 27%. Non-cracked specimens showed three deformation stages: uniform deformation, strain localization, and necking instability. In cracked specimens, strain localization initiated at the crack tips and expanded with increasing displacement. Larger cracks significantly intensified crack-tip strain concentration and enlarged the high-strain zone. Through-wall cracks caused stronger localization and earlier local instability than surface cracks because of the loss of wall continuity, whereas small surface cracks had a limited effect on the final localization path. Crack orientation also affected deformation behavior, and the 45° inclined crack produced the most severe X-shaped localization under combined normal and shear stresses. Full article

The piping systems are critical non-structural elements (NSEs) whose seismic performance directly affects the post-earthquake functionality of essential facilities. However, current seismic design provisions for such systems remain largely empirical, and behavioural factors are rarely calibrated using performance-based methods. This study implements an FEMA P695-inspired framework to calibrate the behaviour factor $\left(q_a\right)$for the installation of sway-braced suspended piping restraint systems in following the force-based requirements specified in Eurocode 8. The representative piping archetypes were developed and analysed using non-linear time history analyses under multiple seismic intensity levels derived from the floor response spectra (FRS) of prototype-reinforced concrete buildings. Fragility curves for two limit states were derived with displacement ductility adopted as the engineering demand parameter (EDP) and peak floor acceleration (PFA) used as the intensity measure (IM). The results show that increasing $\left(q_a\right)$ systematically shifts the fragility curves towards lower median PFA values, indicating higher seismic vulnerability at larger behaviour factor values. The effect of piping layout configuration was of secondary importance compared to the applied reduction factor. The implemented approach provides a rational basis for selecting behavior factors consistent with explicit performance objectives and supports further development of performance-oriented seismic design procedures for non-structural systems. The results show that increasing the behaviour factor $\left(q_a\right)$ leads to a systematic shift in the fragility curves towards lower median PFA values and a noticeable increase in the dispersion of the response. A quantitative analysis shows that increasing the behaviour factor $\left(q_a\right)$ from 1 to 4 results in a reduction of up to approximately 60% in median PFA, highlighting a significant increase in seismic vulnerability at higher behaviour factor values. Full article

The seismic design of spatial joints in long-span concrete-filled steel tube (CFST) arch bridges under complex stresses remains a critical challenge in high-intensity seismic zones. This study investigates the seismic performance and failure mechanisms of CFST spatial KT-type joints, using the Pingnan No. 3 Bridge as a case study. Based on similarity theory, four scaled test specimens were designed. The core variable was the axial compression ratio of the main pipe, while the load on the K-branch served as the parametric variable. Quasi-static tests were conducted under constant static loading on the main pipe and K-branches, coupled with low-cycle cyclic loading on the T-branch. Furthermore, nonlinear finite element analysis (FEA) was performed using Abaqus for cross-validation. The results indicate that the primary failure mode of this joint configuration is the shear-punching failure of the main pipe wall at the T-branch intersection. The load–displacement hysteresis curves exhibit a robust “bow-shaped” profile, indicating substantial plastic energy dissipation capacity. Comparative analysis confirms that hollow steel pipe T-branches offer superior ductility in long-span arch bridges compared to concrete-filled alternatives. By extracting shear stress distribution characteristics from the FEA model to precisely locate the neutral axis, this study proposes a theoretical correction to the ultimate load-carrying capacity calculation model. The derived theoretical values demonstrate good agreement with the experimental results. The relative errors between the calculated and experimental bearing capacities of KT783a, KT783, KT700, and KT607 were 1.99%, 0.23%, 2.26%, and 2.45%, respectively, referring to the T-branch out-of-plane bearing capacity predicted by the proposed formula. The proposed theoretical model provides a reliable quantitative basis for the seismic design and local strengthening of similar spatial joints in long-span CFST arch bridges. Full article

Limit state analysis provides building designers with a better understanding of fundamental structural resistance and deformation requirements, resulting in an overall material economy and offering clear safety boundary conditions for intelligent structural design. Cold-formed high-strength steel has extensive application prospects in structural engineering due to its excellent mechanical properties and flexible cross-sectional options. However, most existing research focuses on its ultimate strength-related behavior, lacking sufficient investigation into deformation properties. This study aims to comprehensively reveal the continuous variation laws of structural resistance and ductility of cold-formed high-strength CHSs (circular hollow sections) with different cross-sectional selections under axial load. Through reliable finite element analysis, the effects of yield strength (f_sy) of cold-formed CHSs, diameter-to-thickness ratio (D/t), and cross-sectional slenderness (λ) on compressive performance in the limit state, including failure mode, axial load-end shortening curve, ultimate-to-yield strength ratio (N_u/N_y), and ductility indicators (displacement ductility coefficient (μ) corresponding to the ascending stage and post-buckling ductility degradation coefficient (R_0.85)), were systematically investigated. The results indicate that the dominant failure mode of high-strength CHSs exhibits outward deformation. With an increase of f_sy and D/t, the value of N_u/N_y decreases, and the development of multiple compression performance exhibits significant nonlinearity, which indicates that blindly improving material strength may not necessarily be conducive to developing structural compressive performance or achieving efficient and economical design solutions. To better serve the ductile limit design of high-strength CHSs, combined with available experimental data and simulation results, the upper limit of λ is proposed to be 0.22, and the predictive models of μ and R_0.85 are established, respectively. Full article

To investigate the mechanical performance of prefabricated cable ducts under soil cover and vehicle wheel loads, refined numerical analysis models were established using ABAQUS finite element software (ABAQUS 6.14-4)for three different structural configurations: four-piece type, inverted four-piece type, and layered type. This study is purely based on finite element numerical simulations without experimental validation. By varying the soil cover thickness (0.5 m, 1.0 m, 2.0 m) and the position of the wheel load (offset distance of 0–1.5 m), the displacement distribution, stress development patterns, and damage characteristics of vulnerable parts for the three duct types were systematically analyzed. The results indicate that under soil cover loads, none of the three duct types experienced damage, and the mid-span displacement and tensile stress of the top slab exhibited an approximately linear growth relationship with the soil cover thickness. The layered duct demonstrated the best overall integrity, with a maximum tensile stress of only 0.098 MPa at a soil cover thickness of 2.0 m, which is approximately 5.8% of that of the four-piece duct. Under wheel loads, the four-piece duct experienced damage under an unoffset 105 kN wheel load, with a maximum steel reinforcement stress of 419.6 MPa, exceeding the yield strength. Due to its double-layer reinforcement in the top slab, the inverted four-piece duct exhibited a failure load increased to over 140 kN, with a maximum steel reinforcement stress of only 103.1 MPa, showing significantly improved ductility. Within the analyzed load cases, no stress indicator exceeded the adopted material thresholds, with a maximum tensile stress of only 0.15 MPa, demonstrating the optimal comprehensive performance. The offset of the wheel load significantly reduced the tensile stress in the top slab; when the offset distance increased from 0 to 1.5 m, the reduction in tensile stress of the four-piece duct top slab exceeded 80%. However, it increased the unevenness of stress distribution on both sides of the duct and altered the stress mode of the side walls. All the above findings are obtained from numerical simulations and can provide a theoretical reference for engineering design. The research findings can provide a theoretical basis for the engineering design and optimization of prefabricated cable ducts. Full article

Waste tire disposal and high-ground-stress soft rock roadway instability are pressing global challenges. This study develops sustainable rubber granule concrete (RGC) using waste tire rubber as a key component, aiming to realize waste valorization and floor heave control. RGC’s mechanical properties (uniaxial/triaxial compression, compressibility, ductility) were systematically tested, and its pressure relief mechanism was validated via finite element analysis (ABAQUS/FLAC) and 60-day field monitoring. Results show that RGC with optimal parameters (12% rubber content, 3–4 GPa elastic modulus, 250–350 mm thickness) achieves 64% bottom stress reduction and >40% displacement control. The material’s excellent energy absorption and flexibility address the brittleness of conventional concrete, ensuring stable support in high-stress environments. This work provides a sustainable, cost-effective concrete modification strategy, bridging waste recycling and geotechnical engineering, with broad implications for low-intensity, high-toughness material applications. Full article

This study presents a comparative investigation of target displacement demands, a fundamental indicator in the seismic performance assessment of reinforced concrete frame systems, within the framework of the Turkish Building Earthquake Code (TBEC-2018), American standards (ASCE 41), and European standards (Eurocode 8). To analyse the consistency in performance levels stipulated by different structural design codes, critical variables, including soil class, number of stories, concrete grade, frame span, and soft story at ground level, were parametrically defined. The impact of these variables on the target displacement demands of the structures was examined through a comparative lens. Nonlinear static pushover analyses based on fiber-based modelling were conducted using SeismoStruct software to determine displacement demands under different seismic code formulations across six distinct variables. The displacements obtained for each variable at identical seismic ground-motion levels were evaluated individually. Analytical results reveal that soil degradation significantly increases target displacements across all codes. At the same time, the presence of a high story affects structural ductility and displacement demands, with varying sensitivities across the codes. Notably, it was observed that TBEC-2018 yields more conservative displacement demands in certain spectral regions than those in ASCE 41 and Eurocode 8. The findings provide critical data for understanding the disparities in safety margins among international seismic design standards. Full article

Corrosion of reinforcing steel is a key cause of deterioration in reinforced concrete (RC) structures exposed to coastal environments with chloride presence. The loss of reinforcing steel cross-sectional area, cracking of the concrete cover, and reduction in confinement progressively decrease both strength and ductility of structural elements. This study provides a reproducible, open-access dataset, compiling input parameters and numerical results of the cyclic behaviour of isolated RC columns and RC frames, specifically addressing their nonlinear cyclic response under moderate corrosion (η < 25%), as well as in the non-corroded (baseline) conditions, generated through conventional nonlinear modelling. In terms of modelling, the methodology applies fibre-section modelling for columns and concentrated plastic hinges for beams. Furthermore, the corrosion effects are incorporated by reducing the steel area and ultimate strain, while also accounting for the decrease in compressive strength of the cracked concrete cover. Therefore, the cyclic response is represented by a Pivot-type hysteretic model. It is worth noting that the dataset provides model input information, such as material stress–strain relationships and backbone curves reflecting corrosion-induced deterioration. It also includes structural outputs, such as force–displacement relationships, and envelopes of quasi-static hysteretic cycles for the analyzed columns and frames. Overall, the dataset facilitates the calibration and validation of numerical models for RC structures affected by corrosion. In conclusion, the contribution enhances the reliability of computational simulations and supports the development of predictive tools for structural performance under degradation scenarios. Full article