Search Results (2,383)

On-site multi-pass welding in building steel structures often induces transverse shrinkage, affecting assembly accuracy and final geometry. Pass-by-pass thermo-elasto-plastic simulation can capture the welding process but is computationally expensive for large steel components. This study proposes an efficient framework for predicting welding-induced transverse shrinkage in H-shaped steel beams by integrating merged weld-pass modeling, a shrinkage function model, and an equivalent indirect action method. A Q355B single-sided V-groove butt-welded plate was simulated to compare the original weld-pass model with three merged schemes. The balanced three-pass scheme preserved the main mechanical response while reducing computation time from 18.863 h to 5.528 h. Based on flat-position and vertical-position plate-welding simulations, a layered shrinkage function model was developed using a plate baseline term and a geometric coupling correction term, with LOOCV RMSE, MAE, and maximum absolute error values of 0.2855 mm, 0.2424 mm, and 0.5123 mm, respectively. The predicted shrinkage was then converted into an equivalent temperature load. The equivalent indirect action method achieved an MAE of 0.1883 mm, RMSE of 0.2713 mm, MAPE of 9.2685%, Pearson coefficient of 0.9730, and R² of 0.9042. This framework supports rapid transverse-shrinkage prediction and construction accuracy control for site-welded H-shaped steel beams. Full article

The exterior frame of super-high-rise steel structures with inclined columns and dense beams contains numerous welded joints and complex constraints, making field welding prone to residual stress and cumulative displacement. Taking the 19th erection segment of the Tianjin China Overseas City Plaza main tower as an example, this study monitored welding-induced stress and column-top displacement using vibrating-wire strain gauges and BeiDou GNSS, and established a finite element model based on the equivalent indirect action method to evaluate different welding sequences. The results show that stresses near welds evolve in stages during lower-flange, web, and upper-flange welding. Adjacent welding causes limited disturbance after the completed joint has stabilized, whereas lower-layer welding can induce secondary shrinkage in upper-layer welded regions. The simulated residual stresses and column-top offsets show reasonable agreement with the monitoring results in terms of overall magnitude and distribution trend, with mean values 2.50% and 6.22% lower than the measurements, respectively. Welding sequence significantly influences deformation. Horizontal grouped skip welding improves construction efficiency by about 30%, and vertical reverse welding further reduces the mean column-top offset by 53.31% and controls the maximum column-top offset within the project-specific limit. Therefore, under the studied structural configuration and construction conditions, the combined sequence of horizontal grouped skip welding and vertical reverse welding is recommended as a practical welding-sequence scheme. Full article

Intumescent coatings are widely used to enhance the fire resistance of structural steel. In contrast to traditional fire protection methods, this novel flexible intumescent protection offers several key advantages: universal compatibility with other coatings (via non-contact wrapping), resistance to extreme temperatures (−60 °C to +90 °C), all-weather usability, and suitability for light-gauge cold-formed thin-walled steel structures. This paper describes the development and investigation of these fire-protective, flexible intumescent coatings based on eco-friendly binders (silicone polymers and acrylic resins) with varying intercalated graphite (IG) content from 0% to 40%. An IG content of 25–40% enables a steel I-section with a section factor of 294 mm⁻¹ to reach its limit state at 44 min (compared to 15 min for unprotected steel). Fire tests on steel beams with a section factor of 172 mm⁻¹ demonstrated that samples reached the deflection limit state at the 64th and 66th minutes, respectively. Thermogravimetric analysis (TGA) was used to determine the temperature ranges for the thermal decomposition and expansion of the IG. Mechanical property studies revealed the influence of IG on the elastic modulus and tensile strength. Accelerated climatic testing in moderately cold conditions and salt spray chamber tests confirmed that the intumescent roll coating has no negative impact on the steel substrates. Full article

To improve deformation compatibility in the negative-moment regions of continuous steel–ultra-high-performance concrete (UHPC) composite girders, this study investigates a controlled-slip bolted shear connector in which bolt-hole clearance is intentionally used as a deformation-release parameter. A three-dimensional nonlinear push-out finite element model was developed in ABAQUS and validated against reported high-strength bolted connector tests. Parametric analyses were then conducted to clarify the effects of bolt-hole clearance, bolt preload, and interface friction on the load–slip response, local UHPC bearing damage, and bolt stress state. The results show that increasing the radial clearance from 0.1 mm to 2.0 mm increases the peak slip from 6.51 mm to 9.17 mm, whereas the peak resistance remains within 661.79–693.86 kN. Bolt preload mainly changes the initial frictional restraint and slip initiation, but has limited influence on the ultimate resistance. Damage and stress distributions further indicate that larger clearance delays UHPC hole-wall bearing damage, while increasing the bending–shear demand on the bolt shank. The results indicate that reserved bolt-hole clearance can be used to increase connector slip capacity while maintaining a comparable shear-resistance level within the investigated parameter range. Full article

To address the challenges of low bearing capacity in Northeast China’s paddy-field soft foundations and the limitations of summer power line construction, a standardized design method for a novel prefabricated modular steel temporary bridge is proposed. Based on the Winkler elastic foundation beam theory, the operating characteristics of rigid short beams and the subgrade reaction distribution under heavy loads were analyzed. On this basis, combined with in situ static load tests and finite element analysis (FEA), the mechanical performance of the temporary bridge under the static loads of crawler-type and six-wheel construction machinery was investigated. The results indicate that when the bridge deck is subjected to a 25-ton construction vehicle, the maximum stress and displacement in the mid-span condition remain well below the material yield strength and the allowable limits stipulated in the Specifications for Design of Highway Steel Bridges (JTG D64-2015). Furthermore, the temporary bridge structure maintains excellent operational stability under a 100-ton extreme construction load and eccentric loading conditions. This study elucidates the mechanical behavior of the temporary bridge, providing a scientific theoretical basis and engineering reference for the design of temporary transit structures in complex environments such as soft paddy field foundations. Full article

This paper presents a code-based static verification of the FA125 hydraulic drilling rig mast under its governing design load combination. Unlike the previously published dynamic investigation of the same platform, the present work establishes the baseline static load path, identifies the governing structural members, evaluates the local stress state in the mast-to-support connection plates, and computes the effective safety coefficients. The mixed finite element model integrates the lattice mast, the support frame, and the base assembly, utilizing beam elements for the slender load-bearing members and shell elements for the localized plate-type connection regions. The governing load combination encompasses structural self-weight, maximum hook load (14.90 kN), and the reactive torque transmitted by the drilling head (0.50 kNm). The maximum mast-top displacement was limited to 4.75 mm. The critical beam elements were located within the lateral base-support region, developing peak compressive and tensile stresses of 70.08 MPa and 69.21 MPa, respectively. The highest localized shell-level von Mises stress (23.62 MPa) was concentrated within the mast-to-support interface connection plates. The results mathematically confirm that the existing FA125 steel structure satisfies the active design criteria, providing a distinct static reference map required for subsequent structural optimization, lightweighting, and selective material substitution. Full article

Semi-rigid connections play a critical role in steel structures; however, most existing component-based approaches do not explicitly account for stiffness degradation and post-yield residual stiffness, which may reduce the accuracy of moment–rotation predictions. To address this limitation, direct numerical simulations (DNSs) of representative T-stub beam-to-column joints were conducted to investigate their nonlinear rotational behavior. Based on the observed joint response, a Joint Component Model (JCM) capable of representing sequential yielding, stiffness evolution, and residual rotational stiffness was developed. Constitutive relationships were derived, and a parameter identification procedure directly relating joint geometry and component mechanical properties to the model parameters was established. The proposed model was subsequently implemented in ANSYS and validated through analyses of T-stub joints and steel frames subjected to static and dynamic loading. The results showed good agreement between the JCM and DNS in terms of moment–rotation relationships, force–displacement responses, and dynamic time-history responses. Compared with DNS, the proposed model significantly reduced computational time while maintaining satisfactory prediction accuracy. The proposed JCM therefore provides an efficient and reliable component-based modeling framework for modeling semi-rigid steel connections and capturing stiffness evolution throughout the entire joint rotation process. 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

To overcome the inherent drawbacks of cast-in-place reinforced concrete bracing—such as long construction periods and difficult demolition—as well as the relatively high construction cost of steel structure bracing, while fully incorporating the respective technical advantages of these two traditional support systems, this paper proposes a novel hybrid prefabricated reinforced concrete (RC)–steel structure foundation pit bracing system. In order to investigate the overall bearing capacity variation in the standard components of this structure under complex external forces in foundation pits, a numerical model was established using the finite element software ABAQUS. The study examines the trend of the axial compressive bearing capacity of a single standard beam segment as the steel thickness of its external stiffening sleeve varies, as well as the effects of eccentric loading, oblique loading, and the presence or absence of auxiliary supports on the structural bearing capacity of multi-segment beam assemblies. The numerical analysis results show that the bearing capacity of a single beam segment exhibits a strong correlation with the variation in sleeve thickness, and a fitting curve of compressive strength as a function of thickness was derived. For the multi-segment assembly, an increase of 1 mm in the load eccentricity in the Y and Z directions reduces the ultimate peak load by approximately 20.95 kN and 23.94 kN, respectively; in the XY and XZ planes, an increase of 1° in the eccentric angle of the oblique load reduces the peak ultimate bearing capacity by about 6.02 kN and 9.67 kN, respectively. Auxiliary supports have a relatively minor influence on the structural bearing capacity. This research thoroughly explores the bearing capacity of the prefabricated steel–concrete composite and steel structure foundation pit bracing under complex working loads, providing strong support for engineering design and demonstrating broad application prospects. Full article

This study investigates the flexural behavior, load-carrying capacity, and crack propagation of concrete beams reinforced with hybrid glass-fiber-reinforced polymer (GFRP) and steel bars. To evaluate the structural performance, concrete beam specimens with cross-sectional dimensions of 150 mm × 300 mm and a total length of 2050 mm were fabricated using a design concrete compressive strength of 35 MPa and tested under flexural loading. Each tested specimen featured a distinct hybrid reinforcement configuration to investigate the influence of bar arrangement on the mechanical behavior. Flexural cracks were systematically monitored using a crack-width comparator gauge at specific loading stages, accounting for key milestones such as ultimate load capacity and sudden load drops. The experimental findings were complemented by an analytical model to validate the performance parameters and predict the ultimate capacity. The results demonstrate that the specific configuration and arrangement of hybrid reinforcement significantly influence the post-cracking stiffness and crack growth. Specifically, the hybrid configuration effectively balances the ductile response of steel with the brittle behavior of GFRP, achieving significant control over serviceability crack widths and an enhanced ultimate load-carrying capacity. Experimental results indicated that for elements exhibiting identical axial stiffness, the reinforcement layering configuration provided a 66% improvement in the deformability factor alongside a 10% enhancement in the load-carrying capacity. It is recommended that the steel tension reinforcement be positioned in the inner layer at a spacing of about two times the GFRP bar diameter to mitigate corrosion risks. Additionally, it was established that the theoretical load capacity accounted for 70% to 86% of the experimental load capacity. Full article

To address the problems of large terrain variation, limited foundation construction, and poor adaptability of conventional supports in mountain photovoltaic projects, this study establishes finite element models of four flexible photovoltaic support systems, including one single-layer cable system and three double-layer cable systems. Under the same span, module layout, and loading conditions, the deflection, cable force, support reaction, equivalent steel consumption, and torsional performance of the different systems are compared under symmetric and asymmetric loading. The results show that the single-layer cable system has the lowest material consumption and better constructability in mountain terrain, but its torsional stiffness is relatively weak. The double-layer systems provide better overall stiffness and torsional resistance, but require more steel and impose larger foundation reactions. The single-layer cable system is then selected for further analysis. To ensure geometric nonlinear convergence, the structural analysis relies on established catenary cable and beam element formulations under incremental loads. Based on the parameter analysis, a combination of 40° for the bottom ground cable and 50° for the top ground cable is recommended to reduce structural reaction moments. Finally, as a simplified structural analysis approach to avoid exhaustive global modeling, a two-span equivalent model for intermediate columns, a single-span equivalent model for edge columns, and a table-based selection procedure are proposed, providing a reference for the rapid design of mountain multi-span flexible photovoltaic supports. Full article

Staggered-floor steel-reinforced concrete beam–column joints are extensively applied in turbine buildings of nuclear power plants to meet the requirements of spatial layout and pipeline arrangement. Such joints feature distinct geometric discontinuity and suffer additional torsion effects as well as asymmetric stress distribution when the middle column is lost, which greatly impairs the structural progressive collapse resistance. In this study, three 1/5-scale joint specimens, consisting of two staggered-floor steel-reinforced concrete joints and one reinforced concrete joint, were tested under vertical monotonic static loading. The failure pattern, deformation property, torsional performance, strain development and load-bearing mechanism were comprehensively analyzed. Finite element models considering the coupling effect of torsion, bending and shear were established and validated via ABAQUS. The test results show that the peak load-bearing capacities of the SRC-1, SRC-2, and RC specimens were 148.2 kN, 149.7 kN, and 69.3 kN, respectively. Compared with the RC specimen, the peak load-bearing capacity of the SRC specimens more than doubled, indicating that the embedded H-section steel can significantly improve the load-bearing capacity of staggered beam–column joints. However, when the staggered height distance was increased from 140 mm to 280 mm, the ultimate collapse displacement of the specimens decreased from 340 mm to 310 mm, indicating a reduction in deformation capacity. The finite element model reasonably reproduced the specimens’ primary load–displacement response and damage characteristics, with a peak load error of 8.93% for SRC-1. Finally, corresponding design recommendations are put forward for staggered-floor steel-reinforced concrete joints in nuclear power plant structures. Full article

Based on the hydrostatic transmission principle, a new method for high-throughput characterization via surface microstrain effects after cold isostatic pressing is proposed. Typical key metallic materials (steels, titanium alloys, and superalloys) were processed under a pressure of 190 MPa with a holding time of 30 min, and surface microstrain effects and characteristics of the specimens were explored via white light interference profilometry, scanning electron microscopy, atomic force microscopy, focused ion beam processing, and transmission electron microscopy. It is shown that all the metallographic polishing specimens exhibit a similar tendency, and two main categories of typical microstrain fields can be detected after CIP processing: (1) slight microstrain and (2) significant microstrain. Significant microstrain with roughening of the surface (roughness increasing) after CIP processing can be detected only in a few microregions. Microregions with weaker micromechanical properties can be characterized and screened in a high-throughput manner through evaluation of the significant microstrains. A new application strategy is proposed for high-throughput characterization of mechanical homogeneity and mechanically weak zones, using the surface microstrain effect during cold isostatic pressing and surface profile analysis. Regions with significant microstrain showed surface roughening (S_q: 6.1 nm→139.7 nm, S_a: 4.8 nm→94.4 nm). Full article

This study investigates hybrid fiber-reinforced polymer (FRP)–steel-reinforced concrete (RC) beams by using three-dimensional finite element models. The research systematically analyzes the influence of key parameters, including FRP type, FRP bar ratio (ρ_f), the ratio of FRP to total reinforcement (ρ_f/ρ_t), and concrete strength. The load–deflection response of the hybrid RC beams is analyzed in detail. The results show that the investigated parameters have a relatively limited influence on the cracking moment, but significantly affect both the yield and ultimate moments. When ρ_f/ρ_t increases from 0 to 0.75, the yield moment decreases by up to 44.34%. When ρ_f increases from 0.55% to 0.88%, the yield moment increases by 50.63%. Meanwhile, increasing the concrete strength significantly enhances the ultimate moment, with a maximum increase of 38.46%. In addition, an energy ductility index is adopted to quantitatively evaluate the structural ductility. The results indicate that the energy ductility index is consistently lower than the conventional ductility index. Finally, to improve the accuracy of theoretical predictions, a semi-empirical simplified formula is proposed for estimating the FRP bar stress at the ultimate state of hybrid beams. The verification results show that the proposed prediction method agrees well with the experimental data, demonstrating that the simplified formula has good applicability and reliability within the parameter range investigated in this study. Full article

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