Abstract:To study the overall bearing capacity of concrete-filled fire-resistant square steel tubular （CFFRSST） columns under axial compression， six CFFRSST columns were designed and tested. The study examined the ultimate bearing capacity and strain development at key locations of the specimens with different welded residual stresses， slenderness ratios， with-to-thickness ratios， and steel strength grades. Besides， the finite element models （FEM） of CFFRSST columns were established， considering the welded residual stress. Based on the validated FEM， further analyses were conducted to evaluate the influence of the welded residual stress， slenderness ratio and width-to-thickness ratio on the axial compression behavior. The results show that the overall stability coefficients of CFFRSST are higher than that of conventional-strength steel concrete-filled square steel tubular （CSSCFSST） columns due to the lower welded residual stress of fire-resistant steel than conventional-strength steel. Furthermore， the differences in overall stability coefficients between the CFFRSST column and the CSSCFSST column increases initially and then decreases with the increase of slenderness ratios. Short columns are more prone to strength failure， and their ultimate bearing capacity are significantly influenced by the interaction between the steel tube and the concrete. As the width- to-thickness ratio decreases， the concrete compressive strength improves due to the constraint effect， leading to a higher stability coefficient. In contrast， the failure of medium and long columns is primarily governed by second-order effects， where the constraint effect is less pronounced. The stability coefficient of columns is primarily affected by welded residual compressive stress， which increases as the width-to-thickness ratio increases. The ultimate bearing capacity obtained from the parametric analysis were compared with predictions from current design codes. The results show that the predictions from Chinese and American codes are lower than the parametric analysis by about 32% and 9%， respectively， while the European code underestimates it by about 7%， providing the most accurate predictions among the three.

Abstract:To efficiently analyze the non-uniform temperature field of complex steel structures under solar radiation， this paper proposes a parametric analysis method based on the Grasshopper platform. By incorporating meteorological data， shadow effects on structures， and simplified temperature calculation formulas， the proposed method enables efficient and accurate analysis of non-uniform solar temperature fields in complex steel structures.To validate the accuracy of the proposed method， the inclined grid steel structure of the Hytera Global Headquarters Building in Shenzhen was selected as a case study. Real-time temperature and meteorological data were collected from multiple monitoring points over a 10-day period. The results show that the root mean square error （RMSE） of daily temperature deviations between the calculated and measured data is less than 12.5%. Additionally， the calculated non-uniform solar temperature fields were translated into temperature loads for construction process simulation. The solar-induced non-uniform thermal effects were studied during construction， and the recommendations for mitigating thermal effects during the design and construction phases were provided.

Abstract:Based on the concept of ductile joints， a prefabricated concrete beam-column ductile joint is proposed， in which low-yield-point and high ductility rods and steel brackets are used for linkage. A quasi-static cyclic loading test was carried out to evaluate the seismic response of the new prefabricated ductile joint. Three full-scale specimens were designed and manufactured， including two new prefabricated ductile specimens with different forms of ductile linkage and one cast-in-place connection specimen for comparison. The failure modes， hysteretic performance and bearing capacity of the three specimens were compared and analyzed. The new prefabricated ductile joint had about 43% higher yield displacement and about 14% higher peak load than those of the cast-in-place comparison joint， and both ductility and bearing capacity were improved. Moreover， as an integral ductile rod anchor block was embedded in the core area of the joint， the joint showed better overall compatible deformation ability， higher displacement ductility and bearing capacity.

Abstract:A multi-scale model of the whole steel frame based on the substructure method was established. Matlab was used to simulate a 600 s synoptic wind for conducting the dynamic time-history analysis. The fatigue characteristic of the detailed structure was analyzed using the equivalent structural stress method. The critical point of wind-induced fatigue in the three-dimensional garage was explored. The rationality of using a multi-scale model based on the substructure method for analyzing the whole structure was assessed. The effects of flange docking mode， transition angle and cantilever beam length on the fatigue life of the structure were calculated. The results show that the wind-induced fatigue danger position of the three-dimensional garage is at the edge of butt weld between the lower flange of the beam and the cantilever segment on the weak axis side of the middle beam-column joint in the windward surface of the top second layer. The predictions from the multi-scale model structure based on substructure method are in good agreement with the second-order solid element model， satisfying engineering accuracy requirements. The stress concentration at the butt weld is effectively reduced by adopting a center-aligned flange welding mode. The fatigue life of the whole structure increases with the increase of the angle of the transition zone and the length of the cantilever beam segment.

Abstract:This paper introduces an innovative dissipative angle bracket for cross-laminated timber（CLT） structures， which takes advantage of the soft-steel bracket and high-damping rubber to provide superior ductility and energy-dissipating capacity. To investigate the mechanical performance of the innovative dissipative angle bracket， monotonic loading and low-cycle reciprocating loading tests were carried out on twelve specimens. The typical failure modes were summarized， and mechanical properties such as initial stiffness， ductility coefficient， and equivalent viscous damping ratio were obtained. An elastoplastic finite element model of the innovative dissipative angle bracket was established using Abaqus software， and a parametric analysis was conducted based on the validated numerical model. The results indicate that the main failure modes of the innovative dissipative angle bracket include steel bridge yielding fracture， local compressive failure of the base， and rubber deboning， with steel bridge yielding fracture being the primary failure modes. All specimens exhibit ductility coefficients greater than 9.6， and the equivalent viscous damping ratio ranges from 9% to 26%， demonstrating high ductility and good energy dissipation capacity. Furthermore， the parametric analysis results show that the load-bearing capacity of the innovative dissipative angle bracket is positively correlated with the thickness of the steel skeleton， the yield strength of the soft-steel， the shear modulus of the rubber and the adoption of the washer， while the height of the rubber has a negligible effect on the load-bearing capacity of the innovative dissipative angle bracket.

Abstract:During the construction of shield cutting piles， reasonable thrust force and control measures can effectively control the deformation of bridge piles， ensuring structural stability and construction safety. Based on a cutting pile project of Beijing Metro Line 12， the penetration force of the straight section of the double-edged ripper during steady-state cutting is derived based on the Mohr-Coulomb strength criterion. The penetration force model of the arc segment of the double-edged ripper is established based on the contact stress distribution on the cutter surface. The penetration force of the ripper is combined with the mathematical model of cutting pile to obtain the calculation method for the total shield thrust force. The total thrust model is validated based on the measured thrust values on site， and the effect of the thrust force on the deformation of the pile foundation is analyzed. Furthermore， an intelligent management and control platform is built based on the calculation method of the thrust force acting on the pile. The platform and construction control measures are applied to the cutting piles project， and the bridge settlement is simultaneously monitored. The monitoring results show that the maximum vertical settlement of the bridge piers and abutments in the cross-river section during cutting piles is 8.48 mm， and the maximum lateral differential settlement is 1.4 mm， respectively， both within the safe control range.

Abstract:To investigate the interaction behavior between terminal blend （TB） asphalt and aggregate interface， this paper uses molecular dynamics simulation and Materials Studio software to construct models of matrix asphalt， TB modified asphalt， TB composite SBS modified asphalt （TB_SBS）， and TB composite EVA modified asphalt （TB_EVA） and aggregate interface. A comprehensive evaluation of the four asphalt aggregate interfaces was conducted by combining energy， adhesion work， relative concentration distribution， and contact angle tests. The results show that modifiers such as rubber powder， SBS， and EVA significantly improve the adhesion performance of the matrix asphalt. TB_EVA exhibits more significant fluctuations in adhesion work with the matrix asphalt at different temperatures compared with TB_SBS， and the increase in adhesion work is more significant at lower temperatures， with the latter having a greater advantage at higher temperatures. By analyzing the reasons， it can be concluded that rubber particles and EVA modifiers absorb light components and fully swell， affecting the aggregation and distribution of asphalt and resin， thereby improving the wetting and adsorption capacity and interaction force between asphalt and aggregate. In addition， TB_SBS maintains a high level of adhesion energy at different temperatures and the range of adhesion energy variation does not exceed 2.5 mJ/m2. TB_SBS exhibits the best high-temperature resistance， and it is a asphalt with the greatest potential for adhesion at the asphalt aggregate interface. It is speculated that the highly polar S=O group in SBS adsorbs the —OH group in AS and the hydrogen atom present in BR， leading to a significant improvement in its adhesion to the aggregate. The relevant conclusions are consistent with the results obtained from contact angle tests. Although the order of magnitude and numerical values vary due to temperature and spatial scale differences， experiments have verified the reliability and rationality of the simulation method in predicting the adhesion process at the asphalt aggregate interface.

Abstract:Transforming sludge into fluid solidified soil is a novel approach for recycling waste material into treasure and resource utilization. This study aims to evaluate the application performance of an alkali-sulfate activated cementitious curing agent in fluid solidified soil. Using the central composite design （CCD） method， the study elucidates the mechanisms by which water-to-solid ratio and curing agent dosage affect the fluidity， unconfined compressive strength， and water stability coefficient. It also explores the underlying strengthening mechanisms through the evolution of the meso-pore structure. The results indicate that fluidity increases linearly with higher water-to-solid ratios and curing agent dosages. The water stability coefficient negatively correlates with the water-to-solid ratio but positively correlates with the curing agent dosage， although the positive effect diminishes with increasing dosage. In terms of strength development， early-age strength is controlled by the combined effects of water-to-solid ratio and curing agent dosage， while mid- to long-term strength （≥7 d） is primarily dominated by curing agent dosage alone. Lowering the water-to-solid ratio or increasing the curing agent dosage promotes the formation of a dense gel network within the solidified soil， significantly enhancing the unconfined compressive strength. The models established based on CCD show high consistency between predicted and experimental values （R2>0.94）， confirming the reliability of the models. Multi-objective optimization results reveal that when the water-to-solid ratio is 0.87 and the curing agent dosage is 12.1%， the fluid solidified soil not only meets the basic requirements for subgrade engineering （fluidity>80 mm， 28 d unconfined compressive strength>1.0 MPa， water stability coefficient≥0.8）， but also achieves full development of strength across all ages.

Abstract:To better analyze the influence of magnetic pole structure on the utilization rate of permanent magnet and realize the adaptability of plate eddy current damper to multi-directional motion， a bidirectional array structure of Halbach permanent magnet is proposed， and the parameters of seven magnetic circuit structure schemes are compared and analyzed. Firstly， by comparing the test results of a plate-type eddy current damper， the accuracy of simulating the damping performance using a three-dimensional electromagnetic finite element transient analysis method is verified. A Halbach cyclic array plate eddy current damper is fabricated. Based on three-dimensional electromagnetic finite element analysis method， the influence of pole number of permanent magnet， back iron of permanent magnet， air gap， conductor plate and other factors on plate eddy current damping coefficient is studied. The research shows that Halbach bidirectional array eddy current damper can maintain good energy dissipation efficiency under multi-direction motion. Through the analysis of simulation results， it is also found that different types of plate-eddy current permanent magnets have similar damping force velocity gradient curves， and the damping force of plate-eddy current dampers at different speeds can be obtained in a short time by relying on the curve function， which can greatly improve the computational efficiency of plate-eddy current damping force.

Abstract:To improve the wind resistance performance of large-span coal-storage structures， an aerodynamic shape optimization method for free-form reticulated structures is proposed by utilizing the parametric configuration method based on non-uniform rational B-splines （NURBS） theory and surrogate modeling technique. A secondary development of the program is carried out based on Grasshopper and Fortran to achieve an integrated process for design parameter adjustment， automatic model updating， and aerodynamic response calculation， which significantly enhances the automation level of optimization design. The control points of NURBS curves serve as optimization variables， and the maximum displacement is set as the objective. An optimization model for free-form reticulated structures is established accordingly. On this basis， aerodynamic shape optimizations are performed on tri-cylindrical and spherical coal-storage reticulated structures. The results show that， the proposed method， which combines parametric modeling and a Kriging surrogate model， effectively identifies rational aerodynamic shapes and achieves effective optimization. The maximum displacements of optimal cylindrical shells under wind directions of 0° and 30°are reduced by 32% and 18%， respectively， while the extreme value for spherical shells is reduced by 12%. The wind resistance performance of both types of reticulated shells is improved， and the goal of reducing construction costs is also achieved. Thus， a new approach for wind-resistant design and form selection of large-span reticulated structures can be finally provided.

Abstract:Current wind-resistant design specifications for long-span cable-supported bridges adopt single-girder， twin-girder， and triple-girder models to analyze wind-induced responses. These models typically assume that the cable anchor points align horizontally with the bridge deck’s torsional center， ignoring the additional torque induced by cable anchorage eccentricity. This study underscores the importance of incorporating cable-girder anchorage eccentricity to accurately estimate wind-induced deformation in long-span cable-stayed bridges. First， based on the deformation compatibility between anchorage components and the elastic deformation of stay cables， a simplified calculation method for cable anchorage eccentricity is established. Then， a revised analytical framework was developed to calculate nonlinear torsional deformation， fully accounting for cable-girder anchorage eccentricity. A numerical case study on the Sutong Yangtze River Highway Bridge indicates that the additional torque by cable-girder anchorage eccentricity exceeds 20% of the aerostatic torque derived from the bridge deck’s aerostatic torsional coefficient. When the anchorage eccentricity is taken into account， the mid-span torsional deformation of the main girder increased by 67.7% and 26.7% at wind attack angle of 0° and 3°， respectively， while the critical onset velocity of aerostatic instability decreases by 6.3% and 3.0%， respectively. This increased torsional deformation further alters the additional wind angle of attack effect on the main girder.

Abstract:To accurately assess the wind loads on photovoltaic （PV） arrays installed on different sloping terrains， wind tunnel tests and CFD numerical simulations were used to study the wind pressure distribution law on the surface of mountainous PV arrays， and the influence of the wind angle， slope and module tilt angle on the wind loads on PV arrays and the interference effect between modules. The results indicate that a wind direction angle of 0° produces the largest wind pressure distribution and highest mean wind pressure coefficient， representing the most unfavorable wind direction. Increasing the module tilt angle increases the wind pressure on front-row modules， and strengthens the interference effect between modules. Sloping terrain weakens the shading effect among PV arrays. With the increase of the slope， the module wind load does not increase with the increase of the contact wind speed （as the elevation of the rear modules constantly increases）. Instead， it initially decreases and only begins to rise when wind loads transition from wind pressure to wind suction. CFD simulation of wind loads on large-scale PV arrays reveal that shading effects between longitudinal columns are not significant. The influence of topography on the mean velocity of the airflow and turbulence characteristics was also investigated.

Abstract:Ultra-thin glass is used to renovate windows. The thin-glass triple-pane glazing with two cavities is developed， so as to investigate the impacts on the thermal performance of the windows by optimizing glass thickness， adjusting the number and position of low emissivity （low-E） coatings， and filling different inert gases. Firstly， hierarchical and K-means clustering methods are used to cluster glass types in the International Glazing Database （IGDB） to determine seven low-E glass types. Secondly， based on typical window frame structures， single or combined strategies such as inserting thin glass， adjusting the low-E coatings， and changing the filling medium are proposed. Then， based on WINDOW， THERM， and Optics， the thermal performance of thin insulating windows under different renovation strategies is analyzed， and a full-scale experimental platform is built to conduct experimental research on the thermal performance of thin insulating windows. Finally， the impact of different renovation strategies on thermal parameters is quantified by the E-FAST sensitivity analysis method. The results show that compared with low-E insulating windows， the heat transfer coefficient of the renovated thin insulating window can be reduced by 30.64%. The type of cavity medium and low-E coating are the key parameters affecting the thermal performance of thin insulating windows. Compared with the renovation method of replacing the whole window， the renovation method of using thin-glass triple-pane glazing for window renovation can reduce material costs by 83%~87%.

Abstract:In addressing the challenges of low utilization， high costs， and complex processes in solid waste recycling， a novel plan for preparing building insulation material is developed. This strategy employs electrolytic manganese residue （EMR） and fly ash （FA） as silicate materials， uses water glass （WG） as an alkaline activator， and incorporates a hydrogen peroxide foaming technique to produce insulation materials with superior mechanical properties at reduced costs. The findings reveal that WG effectively molds the material and stabilizes the foam within a certain usage range. The acceptable incorporation ranges for EMR spans from 0% to 60%， with an optimal addition of 30% and a ceiling of 60%. At 30% EMR， with 355.4~465.4 g of WG， 8 g of hydrogen peroxide， and 2 g of stabilizing agent， the material exhibits thermal conductivity from 0.084 to 0.093 W·m-1·K-1， compressive strength from 0.92 to 1.43 MPa， and density from 457 to 475 kg·m-3. The cost for the precursor materials per cubic meter of this innovative insulation material is roughly 750￥. The cost of this new material is approximately 24% of that of conventional materials using kaolinite as the precursor material and sodium hydroxide with WG as activators. Furthermore， this insulation material demonstrates low toxic leachate concentrations and effectively immobilizes heavy metals.

Abstract:To achieve low-carbon and high-efficiency operation of the big data park， an integrated energy system （IES） coupling photovoltaic （PV） generation， free cooling， waste heat recovery， and multiple energy storage methods is constructed. An energy consumption model of the integrated energy system is established. Due to the characteristics of nonlinear， multivariable and multi-constraint conditions of the model， a rolling optimization control method based on a genetic algorithm is proposed to deal with the dynamic change of energy supply and demand. This method aims to minimize the system’s operational costs by considering factors such as peak-valley electricity pricing， renewable energy output characteristics， and partial load performance characteristics of equipment， thereby determining the optimal operational strategy for the system. By comparing the simulation results with the results of the rule-based control method， it is found that the rolling optimization can reduce system operating costs by 10.68%~12.63%. In addition， scenarios with different solar radiation intensities are selected for this research. The results show that the improvement in PV utilization rate is greatly affected by the battery operation mode. By adjusting the system operating parameters， the PV utilization rate can be further improved.

Abstract:In response to the current situation where the seismic reliability of seismic-isolated curved girder bridges cannot fully consider the randomness and multidimensionality of seismic motion， this paper systematically studies the seismic performance of seismic-isolated curved girder bridges under multi-dimensional random seismic action from thea perspective of full probability. A dual particle， six-degree-of-freedom model of a seismic-isolated curved girder bridge is established and its nonlinear motion equations are derived. By introducing a stochastic model of the engineering seismic acceleration power spectrum， the spectral representation seismic-isolated random function method is used to generate multidimensional non-stationary vibration time history samples that conform to the same set system. The seismic acceleration time history samples are used as the random excitation input for the seismic-isolated curved girder bridge. The fourth-order Runge-Kutta method is used to obtain the dynamic time history data of the seismic-isolated curved girder bridge structure， and the TVD difference scheme is used to solve its generalized probability density evolution equation to quantify the probability information of the structural dynamic response during earthquake duration. Then， an extreme value stochastic process is constructed to obtain the displacement extreme value distribution functions and system reliability of the lower structure and isolation layer of the seismic-isolated curved girder bridge. The results indicate that considering the multidimensionality of non-stationary random seismic excitation amplifies the dynamic response of seismic-isolated curved girder bridge structures. The probability density evolution method shows superior performance in solving strongly nonlinear structural systems such as seismic-isolated curved girder bridges. By adjusting the reasonable values of the bridge deck width and curvature radius of the seismic-isolated curved girder bridge， the seismic performance of the seismic-isolated curved girder bridge can be improved.

Abstract:To improve the accuracy and computational performance of tunnel crack size measurement， a visual width measurement method based on multi-scale feature fusion of the central axis was proposed. Firstly， the crack width was selected as the research object， and the extraction method of the crack central axis was improved. A template matching strategy was proposed to improve the simplification rate of the central axis pixels generated by the parallel thinning algorithm. Secondly， an optimized central axis branch removal method was proposed to improve the removal effect of redundant branches in the crack skeleton. Finally， the least square method was used to fit the central axis curve， and a width measurement method based on multi-scale direction feature fusion of the central axis of the crack skeleton was proposed. Using the field-of-view angle calibration of a complementary metal-oxide-semiconductor （CMOS） sensor， the pixel width of the crack is converted to the actual crack width. The Huaxi Tunnel in Banan District， Chongqing， was selected as the research object for case analysis. The experimental results showed that， compared with the maximum expansion circle method， the shortest path method， and the orthogonal projection method， the proposed approach reduces the average pixel absolute error of crack width measurement by 9.89 percentage points， 4.67 percentage points and 15.61 percentage points respectively. Moreover， the improved crack axis extraction method achieved a 6.58 percentage points higher pixel simplification rate than that the original method. At the same time， in the crack measurement experiments at different measurement distances， the adaptive ability of the proposed method at different measurement distances was verified.

Abstract:To further improve the efficiency of grid-generated turbulent wind field for large eddy simulation （LES）， an improved turbulence generation method based on LES is proposed in this paper， in which grid-jet can be obtained on the inlet boundary. Then， LES of the flow around a circular cylinder at Re=3 900 is successfully carried out. The results indicate that the turbulent wind field generated based on virtual grid exhibits isotropic characteristics. The turbulence intensity decreases exponentially along the flow direction， and the turbulence integral scale increases linearly along the flow direction. The fluctuating wind power spectrum is consistent with the von Kármán spectrum. In addition， compared to a smooth inflow， the mean drag coefficient of the cylinder decreases in the turbulent inflow， whereas the standard deviation of the drag coefficients and lift coefficients increase significantly， indicating stronger pulsations of the lift and drag forces in turbulent flow. Turbulence also delays flow separation on the cylinder surface and inhibits separation， resulting in a shorter recirculation length and a lower Strouhal number. Vortex shedding becomes unstable and the shedding energy is stronger.

Abstract:In view of the accelerated deterioration of concrete in complex environments of plateaus， such as low pressure， low humidity， low temperature， and large temperature difference， the air bubble stability， air-entraining effect， mechanical properties， shrinkage property， and frost resistance of concrete under plateau environments have attracted much attention. However， the relevant research status remains to be analyzed and summarized. This paper first compares and analyzes the characteristics of air pressure， temperature， and humidity in typical cities of plateau and plain regions in China. The influences of key environmental factors， including low air pressure， low humidity， low temperature， and large temperature difference， on workability， microstructure， mechanical properties， shrinkage property， and frost resistance of cement-based materials are then summarized. The deterioration degree and mechanism of cement-based materials under these key environmental factors are revealed.