摘要：
This paper proposes beam-only connected steel plate shear walls (BSWs) and composite shear walls (BCWs) to mitigate the seismic risk of concrete-filled double-steel tube (CFDST) frames. As a new type of structural system, limited works have been reported on the performance limit definitions and risk-informed assessment of them due to the lack of experimental and analytical data. According to the cyclic tests results performed by the authors and the guidance of FEMA 356, three stage of limit states are defined and the corresponding results are recommended. Then, an elaborate numerical model is developed that considering the nonlinear behaviour of materials, panel zone, beam-column joints and shear walls, and the model is validated by the test results. Besides, three CFDST buildings with different height and two CFDST buildings with BSW or BCW are modeled based on the validated numerical model. Finally, seismic fragility analyses as well as seismic risk assessments are conducted on these models, and the annual occurrence probability and collapse probability of the structure within 50 years are calculated. The results show that both BSWs and BCWs can effectively mitigate the seismic responses and risks of CFDST buildings, and the collapse probability of buildings within 50 years decreases from 7.7 % to 1.39 % and 1.24 % due to the equipped BSWs and BCWs, respectively.
This paper proposes beam-only connected steel plate shear walls (BSWs) and composite shear walls (BCWs) to mitigate the seismic risk of concrete-filled double-steel tube (CFDST) frames. As a new type of structural system, limited works have been reported on the performance limit definitions and risk-informed assessment of them due to the lack of experimental and analytical data. According to the cyclic tests results performed by the authors and the guidance of FEMA 356, three stage of limit states are defined and the corresponding results are recommended. Then, an elaborate numerical model is developed that considering the nonlinear behaviour of materials, panel zone, beam-column joints and shear walls, and the model is validated by the test results. Besides, three CFDST buildings with different height and two CFDST buildings with BSW or BCW are modeled based on the validated numerical model. Finally, seismic fragility analyses as well as seismic risk assessments are conducted on these models, and the annual occurrence probability and collapse probability of the structure within 50 years are calculated. The results show that both BSWs and BCWs can effectively mitigate the seismic responses and risks of CFDST buildings, and the collapse probability of buildings within 50 years decreases from 7.7 % to 1.39 % and 1.24 % due to the equipped BSWs and BCWs, respectively.
通讯机构：
[Wang, HD ] C;Cent South Univ Forestry & Technol, Sch Civil Engn, Changsha 410004, Peoples R China.
关键词：
Calcareous sand;EICP;Stress-strain curve;Calcium carbonate content;Statistical damage constitutive model
摘要：
The enzyme-induced calcium carbonate precipitation (EICP) technique was utilized to cement calcareous sand. The mechanical properties of EICP-cemented calcareous sand at various cementation degree were investigated using consolidated drained triaxial compression tests. A statistical damage constitutive model tailored for EICP-cemented calcareous sand was also developed based on damage mechanics theory. The findings are as follows: (1) The EICP technique significantly enhances the cementation of calcareous sand. As the number of grouting operations increases, the peak deviator stress of the cemented material gradually increases, with the maximum enhancement approaching 2.5 times. Moreover, during the stress decay phase following the peak stress, the decay rate of the cemented sand accelerates, displaying a more pronounced brittle characteristic. (2) With the increased calcium carbonate content, the peak eccentric stress of the cemented body increases significantly, and there is an obvious nonlinear exponential correlation between them. (3) The statistical damage constitutive model, formulated based on Lemaitre's strain equivalence principle combined with a log-normal distribution and the Drucker–Prager strength criterion, accurately predicts the stress–strain curves, effectively simulating the complete stress–strain evolution of EICP-cemented sand under different numbers of grouting operations and varied confining pressure conditions. (4) At higher cementation levels or lower confining pressures, the internal damage process of the EICP-cemented calcareous sand specimens intensifies, indicated by the rapid increase of the damage variable D with axial strain. The research findings can provide a crucial theoretical foundation for the application of EICP technology in the treatment of island reef or roadbed foundations, aiding in the analysis and prediction of the mechanical properties of EICP-cemented calcareous sands.
摘要：
Due to the complex and diverse terrains in China, the unequal height piers are commonly used for high-speed railway track-bridge system (HSRTBS). The unequal pier height may amplify the seismic responses of the components in HSRTBs. Besides, the energy dissipation steel device (EDSD) is suggested to control the damages. Therefore, how to balance the effect of the unequal pier height and the arrangement of these devices is an essential issue. This paper proposed U-shaped EDSD, and investigates how the device arrangements affect the seismic responses of 5-span 4-pier HSRTBs with three typical pier height configurations. The cases of HSRTBS are equal height piers, symmetrical piers, and asymmetrical piers. The results show that the peak response on the rail of the HSRTBS with unequal height piers is about 10% higher than the equal height cases. A proper arrangement of the proposed U-shaped EDSD could reduce the response of the HSRTBS by approximately 50%. However, a negative influence may occur if the devices are placed on only several piers of the HSRTBS with asymmetrical unequal height piers, which needs attention from designers. Similar findings are observed in the seismic fragility results. This research could provide insights into the seismic response control of HSRTBS with unequal height piers.
期刊：
Case Studies in Construction Materials,2025年:e04772 ISSN：2214-5095
通讯作者：
Jinyang Fu
作者机构：
[Maolong Xiang; Junsheng Yang; Jinyang Fu] School of Civil Engineering, Central South University, Changsha, 410075, China;[Zhiqiang Liu] China Railway Southwest Research Institute Co. Ltd., Chengdu, 611731, China;[Cong Zhang] School of Civil Engineering, Central South University of Forestry and Technology, Changsha, 410004, China
通讯机构：
[Jinyang Fu] S;School of Civil Engineering, Central South University, Changsha, 410075, China
关键词：
3D printing technology;Gypsum-based material;Elaborated tunnel model;Stratified rock mass;Physical model test
摘要：
This study proposed and applied innovative methods for constructing elaborated tunnel models and stratified rock masses, utilizing 3D printing technology and gypsum-based materials. In the test, three types of elaborated tunnel models and a traditional model are constructed and their application effects are compared in physical model tests. Experimental results indicate that elaborated models with base structures, such as inverted arch filling, more accurately represent the deformation and damage observed in actual tunnels. The precision of these elaborated models is enhanced by 3D printing technology, while gypsum-based materials effectively simulate the failure of tunnel structures under high in-situ stress. Additionally, horizontally soft-hard stratified rock masses are well replicated by employing the self-leveling characteristics of the slurry of gypsum-based similar materials. Furthermore, the failure characteristics of tunnel structures and stratified rock masses are investigated in the test. Under high horizontal in-situ stress, cracks in tunnel structures and failures in surrounding stratified rocks are concentrated in the vault and base of the tunnel, and the damage to the surrounding rocks manifests as the bending of rock layers and shear-slip failure of the rock mass. Therefore, to prevent damage to tunnels in nearly horizontally stratified strata subjected to high in-situ stress, it is crucial to reinforce the structures and surrounding rocks at both the bottom and vault of the tunnel.
This study proposed and applied innovative methods for constructing elaborated tunnel models and stratified rock masses, utilizing 3D printing technology and gypsum-based materials. In the test, three types of elaborated tunnel models and a traditional model are constructed and their application effects are compared in physical model tests. Experimental results indicate that elaborated models with base structures, such as inverted arch filling, more accurately represent the deformation and damage observed in actual tunnels. The precision of these elaborated models is enhanced by 3D printing technology, while gypsum-based materials effectively simulate the failure of tunnel structures under high in-situ stress. Additionally, horizontally soft-hard stratified rock masses are well replicated by employing the self-leveling characteristics of the slurry of gypsum-based similar materials. Furthermore, the failure characteristics of tunnel structures and stratified rock masses are investigated in the test. Under high horizontal in-situ stress, cracks in tunnel structures and failures in surrounding stratified rocks are concentrated in the vault and base of the tunnel, and the damage to the surrounding rocks manifests as the bending of rock layers and shear-slip failure of the rock mass. Therefore, to prevent damage to tunnels in nearly horizontally stratified strata subjected to high in-situ stress, it is crucial to reinforce the structures and surrounding rocks at both the bottom and vault of the tunnel.
摘要：
The research aimed at evaluating the creep properties of glulam beams connected with steel joining plates and bolts (GBSBs) made of Larix gmelinii. Three GBSBs and three intact Glulam beams of identical dimensions were subjected to long-term service loads, with their mid-span deflection behavior monitored and analyzed to understand the creep mechanisms and material performance impacts over an extended period. After 900 days of loading, the average mid-span deflection of the intact Glulam beams and the GBSBs were 18.55 mm and 27.70 mm, respectively. Three existing creep models and a modified Burger model were adopted to fit the long-term deflection curves of the specimens. The modified Burger model provided satisfactory accuracy capturing the trend of creep behavior and demonstrated superior capability in predicting the trend throughout the service life period. It was also found that the elastic deformation emerged as the main deformation form within the beams, and the viscoelastic deformation may potentially govern the deformation. Additionally, theoretical calculations of the long-term deformation using the timber long-term deformation calculation method specified in Eurocode 5 were conducted. These results are in good agreement with the calculation results according to Eurocode 5.
The research aimed at evaluating the creep properties of glulam beams connected with steel joining plates and bolts (GBSBs) made of Larix gmelinii. Three GBSBs and three intact Glulam beams of identical dimensions were subjected to long-term service loads, with their mid-span deflection behavior monitored and analyzed to understand the creep mechanisms and material performance impacts over an extended period. After 900 days of loading, the average mid-span deflection of the intact Glulam beams and the GBSBs were 18.55 mm and 27.70 mm, respectively. Three existing creep models and a modified Burger model were adopted to fit the long-term deflection curves of the specimens. The modified Burger model provided satisfactory accuracy capturing the trend of creep behavior and demonstrated superior capability in predicting the trend throughout the service life period. It was also found that the elastic deformation emerged as the main deformation form within the beams, and the viscoelastic deformation may potentially govern the deformation. Additionally, theoretical calculations of the long-term deformation using the timber long-term deformation calculation method specified in Eurocode 5 were conducted. These results are in good agreement with the calculation results according to Eurocode 5.
期刊：
European Journal of Education,2025年60(2):e70078 ISSN：0141-8211
通讯作者：
Qian Wang
作者机构：
[Qian Wang; Shiwang Hou; Sixian Wan] School of Advanced Interdisciplinary Studies, Hunan University of Technology and Business, Changsha, People's Republic of China;[Xin Feng] School of Civil Engineering, Central South University of Forestry and Technology, Changsha, People's Republic of China;[Hao Feng] Engineering Department, Country Garden Group, Foshan, People's Republic of China
通讯机构：
[Qian Wang] S;School of Advanced Interdisciplinary Studies, Hunan University of Technology and Business, Changsha, People's Republic of China
摘要：
To prepare undergraduates for complex careers, interdisciplinary higher education is gaining popularity. However, implementing interdisciplinary learning in engineering management is challenging due to the complex and intertwined knowledge structures. While smart education platforms provide access to extensive knowledge bases, the intricate web of relationships can overwhelm undergraduates. Therefore, innovative technologies are needed to create a coherent knowledge system. Knowledge graphs, derived from artificial intelligence, are pivotal tools for connecting knowledge points across courses. This study begins by explaining the necessity of constructing interdisciplinary knowledge graphs. It then uses engineering management as a case study to outline a strategic framework for developing a knowledge graph. Finally, it analyses the benefits and challenges of applying knowledge graphs in interdisciplinary higher education.
摘要：
To address the specific demands for early-strength materials in ecological slope emergency restoration projects and ecological slope construction in cold regions, this study has developed Ecological Porous Concrete (EPC) with low-alkali characteristics and enhanced early-strength advantages through a synergistic mechanism of alkalinity regulation and strength enhancement. This provides new material support for advancing the ecological restoration technology system within the context of carbon neutrality. In this study, we systematically investigated the influences of triethanolamine (TEA) and nano-silica (NS) on the mechanical properties and CO 2 absorption capacity of EPC cementitious materials. The results indicate that the incorporation of TEA and NS effectively mitigates the issue of reduced early strength in EPC caused by oxalic acid, leading to a significant improvement of 33.3% in the early mechanical properties. Furthermore, the addition of TEA and NS promotes crystal nucleation and growth during the hydration reaction of EPC cementitious materials, facilitating the transition from the nucleation and growth (NG) process to the impingement (I) process, and enhances the CO 2 sequestration capacity of the EPC cementitious materials. Planting tests demonstrate that the early-strength EPC exhibits excellent vegetation performance, fulfilling the practical needs of the project. These research findings offer robust technical support for accelerating the construction speed of EPC and ensuring project quality. They are of considerable significance in promoting the industrialized application of EPC in green building and ecological restoration fields, particularly in cold region engineering and emergency ecological slope restoration projects.
To address the specific demands for early-strength materials in ecological slope emergency restoration projects and ecological slope construction in cold regions, this study has developed Ecological Porous Concrete (EPC) with low-alkali characteristics and enhanced early-strength advantages through a synergistic mechanism of alkalinity regulation and strength enhancement. This provides new material support for advancing the ecological restoration technology system within the context of carbon neutrality. In this study, we systematically investigated the influences of triethanolamine (TEA) and nano-silica (NS) on the mechanical properties and CO 2 absorption capacity of EPC cementitious materials. The results indicate that the incorporation of TEA and NS effectively mitigates the issue of reduced early strength in EPC caused by oxalic acid, leading to a significant improvement of 33.3% in the early mechanical properties. Furthermore, the addition of TEA and NS promotes crystal nucleation and growth during the hydration reaction of EPC cementitious materials, facilitating the transition from the nucleation and growth (NG) process to the impingement (I) process, and enhances the CO 2 sequestration capacity of the EPC cementitious materials. Planting tests demonstrate that the early-strength EPC exhibits excellent vegetation performance, fulfilling the practical needs of the project. These research findings offer robust technical support for accelerating the construction speed of EPC and ensuring project quality. They are of considerable significance in promoting the industrialized application of EPC in green building and ecological restoration fields, particularly in cold region engineering and emergency ecological slope restoration projects.
作者机构：
[Zhan, Xue-fang; Zhao, Tian-pu; Wang, Fang; Wang, Hao-lei; Zhao, Yi-bin] Cent South Univ Forestry & Technol, Civil Engn Dept, Shaoshan South Rd 498, Changsha 410004, Peoples R China.
通讯机构：
[Zhao, YB ] C;Cent South Univ Forestry & Technol, Civil Engn Dept, Shaoshan South Rd 498, Changsha 410004, Peoples R China.
关键词：
Fully jointless bridges;Microcracked R-ECC road-bridge link slabs;Seasonal temperature variation;Traffic loads;Crack development;Rebound deflection;Sensitive parameter finite element analysis
摘要：
A novel road-bridge link slab utilizing rubberized engineered cementitious composites (R-ECC) has been proposed for fully jointless bridges (FJBs). Preliminary research has shown that R-ECC road-bridge link slabs possess superior deformation absorption capacity, tensile strength, and crack control capabilities. However, micro-cracks developed on the surface of these slabs due to seasonal temperature fluctuations. While R-ECCs demonstrate improved bending ability compared to conventional ECCs, they exhibit lower compressive strength. Further research is necessary to investigate the crack development and bending deflection of microcracked R-ECC road-bridge link slabs under vehicle loads, which will help determine the suitability of R-ECCs for this application. The microcracked R-ECC slab has a great crack control capacity, and the rebound deflection measured in the experiment is less than the allowable value, indicating that the microcracked R-ECC slab meets the durability and strength standard. A sensitivity parameter finite element analysis was conducted considering the effects of slab thickness and equivalent elasticity modulus of the foundation on the R-ECC road-bridge link slab. Two evaluation indexes 'C(t)' and 'C(e)' are proposed to evaluate the performance and construction cost of the R-ECC slab. To improve performance and minimize construction costs, a design thickness of 180mm and an equivalent elasticity modulus of the foundation of 800MPa were recommended for the R-ECC road-bridge link slab.
作者机构：
[Shuai He; Jian Yin; Sijiao Li; Yangyi Zhu; Sizhe Liu; Yihao Chen] School of Civil Engineering, Central South University of Forestry and Technology, Changsha, 410004, China
通讯机构：
[Jian Yin] S;School of Civil Engineering, Central South University of Forestry and Technology, Changsha, 410004, China
摘要：
The low pozzolanic activity of fly ash (FA) leads to reduced early-age strength in high-volume FA cement systems (HVFAC). While the individual addition of triethanolamine (TEA) or nano-silica (NS) can enhance the mechanical properties of HVFAC, the synergistic effect of their combined incorporation remains unclear. This study investigates the synergistic effect of TEA and NS on the early hydration process and the mechanism of later-stage strength enhancement in HVFAC, using methods including compressive strength testing, isothermal calorimetry, the hydration kinetics model (K-D), TG, Rietveld-XRD, MIP, and SEM-EDS. The results showed that the compressive strength(CS) of mortar with TEA+NS reached 17.0 MPa at 1 day and 56.8 MPa at 28 days, representing increases of 32.8% and 42.0% over the control group, respectively. The 28-day CS improvement (42.0%) significantly exceeded the combined effect of using TEA and NS individually (25.8%). The addition of NS overcame the early hydration inhibition of C 3 S caused by TEA, promoted the formation of calcium hydroxide (CH), and enhanced the pozzolanic reaction(PR) of FA, resulting in a 14.3% increase in early hydration heat release compared to the control.Moreover, TEA+NS accelerated the formation of AFm phases, increased the amorphous phase content, and chemically bound water. MIP results showed that the porosity of the paste decreased from 29.58% to 22.16% with the addition of TEA+NS. SEM-EDS analysis confirmed that TEA+NS promoted the PR of FA and that NS reacted with microcrystalline CH incorporated within the C-S-H gel, reducing the Ca/Si ratio and improving the compactness of the C-S-H structure.
The low pozzolanic activity of fly ash (FA) leads to reduced early-age strength in high-volume FA cement systems (HVFAC). While the individual addition of triethanolamine (TEA) or nano-silica (NS) can enhance the mechanical properties of HVFAC, the synergistic effect of their combined incorporation remains unclear. This study investigates the synergistic effect of TEA and NS on the early hydration process and the mechanism of later-stage strength enhancement in HVFAC, using methods including compressive strength testing, isothermal calorimetry, the hydration kinetics model (K-D), TG, Rietveld-XRD, MIP, and SEM-EDS. The results showed that the compressive strength(CS) of mortar with TEA+NS reached 17.0 MPa at 1 day and 56.8 MPa at 28 days, representing increases of 32.8% and 42.0% over the control group, respectively. The 28-day CS improvement (42.0%) significantly exceeded the combined effect of using TEA and NS individually (25.8%). The addition of NS overcame the early hydration inhibition of C 3 S caused by TEA, promoted the formation of calcium hydroxide (CH), and enhanced the pozzolanic reaction(PR) of FA, resulting in a 14.3% increase in early hydration heat release compared to the control.Moreover, TEA+NS accelerated the formation of AFm phases, increased the amorphous phase content, and chemically bound water. MIP results showed that the porosity of the paste decreased from 29.58% to 22.16% with the addition of TEA+NS. SEM-EDS analysis confirmed that TEA+NS promoted the PR of FA and that NS reacted with microcrystalline CH incorporated within the C-S-H gel, reducing the Ca/Si ratio and improving the compactness of the C-S-H structure.
期刊：
Construction and Building Materials,2025年483:141795 ISSN：0950-0618
通讯作者：
Ke Ding
作者机构：
Hunan Province Key Laboratory of Engineering Rheology, Central South University of Forestry and Technology, Changsha 400014, China;College of Civil Engineering, Central South University of Forestry and Technology, Changsha 410014, China;Dongying Development Zone Haifu Aquaculture Center, Dongying 257092, China;[Ke Ding] Hunan Province Key Laboratory of Engineering Rheology, Central South University of Forestry and Technology, Changsha 400014, China<&wdkj&>College of Civil Engineering, Central South University of Forestry and Technology, Changsha 410014, China;[Chao Zeng] College of Civil Engineering, Central South University of Forestry and Technology, Changsha 410014, China<&wdkj&>Dongying Development Zone Haifu Aquaculture Center, Dongying 257092, China
通讯机构：
[Ke Ding] H;Hunan Province Key Laboratory of Engineering Rheology, Central South University of Forestry and Technology, Changsha 400014, China<&wdkj&>College of Civil Engineering, Central South University of Forestry and Technology, Changsha 410014, China
摘要：
As an environmentally friendly material, the ecological porous concrete has made certain progress in mix design, physical and mechanical properties, and plant compatibility etc. However, the relationship between its complex internal pore structure and macroscopic properties still needs to be further studied. In the paper, the compressive strength, porosity, and fractal dimension of pore structure of the ecological porous concrete with coarse aggregate particle sizes ranging from 19 to 26.5 were investigated. The standard cubic specimens were tested for compressive strength after 28 days. Monts method and the image analysis method were used to calculate porosity, while the image analysis was used to determine equivalent pore size distribution. The fractal dimensions of pore structures were analyzed using the box-counting method. The ecological porous concrete exhibited an average compressive strength of 8.76 MPa, porosity ranging 25 %-30 %, dominant equivalent pore sizes of 5–7 mm, and fractal dimensions between 1.2 and 1.8. Notably, the porosity values derived from Monts method were slightly lower than those from the image analysis method. A linear relationship between fractal dimension and porosity was established through the least-square fitting method. This study bridged fractal geometric characteristics of pore structures with macro-micro performance of the ecological porous concrete, providing novel insights for optimizing its environmental and engineering applications. The established correlations offer a fresh perspective for advancing research on performance prediction and material design.
As an environmentally friendly material, the ecological porous concrete has made certain progress in mix design, physical and mechanical properties, and plant compatibility etc. However, the relationship between its complex internal pore structure and macroscopic properties still needs to be further studied. In the paper, the compressive strength, porosity, and fractal dimension of pore structure of the ecological porous concrete with coarse aggregate particle sizes ranging from 19 to 26.5 were investigated. The standard cubic specimens were tested for compressive strength after 28 days. Monts method and the image analysis method were used to calculate porosity, while the image analysis was used to determine equivalent pore size distribution. The fractal dimensions of pore structures were analyzed using the box-counting method. The ecological porous concrete exhibited an average compressive strength of 8.76 MPa, porosity ranging 25 %-30 %, dominant equivalent pore sizes of 5–7 mm, and fractal dimensions between 1.2 and 1.8. Notably, the porosity values derived from Monts method were slightly lower than those from the image analysis method. A linear relationship between fractal dimension and porosity was established through the least-square fitting method. This study bridged fractal geometric characteristics of pore structures with macro-micro performance of the ecological porous concrete, providing novel insights for optimizing its environmental and engineering applications. The established correlations offer a fresh perspective for advancing research on performance prediction and material design.
作者机构：
[Chen, Ying; Huang, Jingxiang; Cheng, Xiang; Liu, Lei; Wang, Shuaifeng; Liu, Peng] Cent South Univ, Sch Civil Engn, Changsha 410000, Peoples R China.;[Huang, Jingxiang; Cheng, Xiang; Liu, Lei; Yu, Zhiwu; Wang, Shuaifeng; Liu, Peng] Natl Engn Res Ctr High Speed Railway Construct, Changsha 410000, Peoples R China.;[Li, Qizhi; Shao, Guangqiang] China Construct Second Engn Bur Ltd, Beijing 100160, Peoples R China.;[Yu, Zhiwu; Liu, Peng] China Railway Grp Ltd, Beijing 100039, Peoples R China.;[Wang, Lingling] Guizhou Univ, Sch Civil Engn, Guiyang 550025, Peoples R China.
通讯机构：
[Liu, P ] C;Cent South Univ, Sch Civil Engn, Changsha 410000, Peoples R China.;Natl Engn Res Ctr High Speed Railway Construct, Changsha 410000, Peoples R China.;China Railway Grp Ltd, Beijing 100039, Peoples R China.
摘要：
The effects of high-temperature modified phosphogypsum (HPG), incorporated at contents of 40%, 50%, and 60%, on the compressive strength and elastic modulus of mortar and concrete were investigated. Additionally, the influence of graded granulated blast furnace slag powder (GGBS), quicklime, and silica fume on the mechanical properties of HPG-based mortar (HPGM) and HPG-based concrete (HPGC) was discussed. Moreover, the microstructure of HPGM was analyzed using scanning electron microscopy (SEM). A two-dimensional mesoscale model of HPGC was developed to predict how variations in HPG content, coarse aggregate characteristics, and interfacial transition zone (ITZ) characteristics influence the compressive strength and elastic modulus of HPGC. The experimental results showed that high volumes of HPG weakened the mechanical properties of HPGM and HPGC, while appropriate amounts of mineral admixtures offset the negative effects caused by calcium hydroxide (Ca(OH)2) crystals and impurities within the system. The simulation results indicated that the maximum deviation between the mesoscale model prediction and experimental data was only 8.38%, which verified the accuracy of the mesoscale model prediction. The compressive strength of HPGC initially decreased and subsequently increased with the rise in the modulus and content of coarse aggregate, whereas it declined with higher HPG dosage and increased ITZ thickness. In contrast, the elastic modulus of HPGC showed a gradual increase with rising coarse aggregate content and improved ITZ mechanical properties, while it decreased as HPG content and ITZ thickness increased.
摘要：
Fatigue crack growth in headed stud and welding seam under I-II mixed loading are experimentally investigated. The modified CTS specimens are abstracted both from the headed stud and the welding seam. The influences of I-II mixed loading angle and ratio on fatigue crack growth are investigated and clarified. The correlation of the fatigue crack growth rate (FCGR) data with different formulas of equivalent SIF range are discussed and the intrinsic parameters of FCGR under I-II mixed loading are recommended. Results show that the fatigue crack exhibits a notable deviation under the I-II mixed loading. Crack deviation in WM specimens is smaller than that in the BM specimens, but there are 1–2 additional slight deviations as the crack passes through the weldment. The MTS and S criteria accurately predict crack deviation for base metal (BM) specimens but show larger errors for weld metal (WM) specimens. The crack closure effects in headed stud and welding seam are much more significant in case subjected in I-II mixed loading than that in mode I loading and mode II loading. Fatigue crack growth in welding seam is faster than that in headed stud. The Δ K V, eff formula by Borrego et al. has the best relevance for mixed mode FCGR data in both the headed stud and welding seam.
Fatigue crack growth in headed stud and welding seam under I-II mixed loading are experimentally investigated. The modified CTS specimens are abstracted both from the headed stud and the welding seam. The influences of I-II mixed loading angle and ratio on fatigue crack growth are investigated and clarified. The correlation of the fatigue crack growth rate (FCGR) data with different formulas of equivalent SIF range are discussed and the intrinsic parameters of FCGR under I-II mixed loading are recommended. Results show that the fatigue crack exhibits a notable deviation under the I-II mixed loading. Crack deviation in WM specimens is smaller than that in the BM specimens, but there are 1–2 additional slight deviations as the crack passes through the weldment. The MTS and S criteria accurately predict crack deviation for base metal (BM) specimens but show larger errors for weld metal (WM) specimens. The crack closure effects in headed stud and welding seam are much more significant in case subjected in I-II mixed loading than that in mode I loading and mode II loading. Fatigue crack growth in welding seam is faster than that in headed stud. The Δ K V, eff formula by Borrego et al. has the best relevance for mixed mode FCGR data in both the headed stud and welding seam.
作者机构：
[Hu, Yi; Wang, Da; Sun, Hongyu; Hu, Y; Wang, Luyu] Cent South Univ Forestry & Technol, Sch Civil Engn, Changsha 410004, Peoples R China.;[Jiang, Liqiang; Zhou, Shizhong] Cent South Univ, Sch Civil Engn, Changsha 410075, Peoples R China.
通讯机构：
[Hu, Y ] C;Cent South Univ Forestry & Technol, Sch Civil Engn, Changsha 410004, Peoples R China.
关键词：
Axial capacity;Cold-formed steel;Light-weight foam concrete-filled;T-section special shape
摘要：
This paper proposes T-section special shape light-weight foam concrete-filled (FCF) cold-formed steel (CFS) built-up columns, which can be used as the side columns that easily connect CFS shear walls from three directions. Light-weight foam concrete was used to mitigate the buckling failure and to increase loading capacity of the columns. Axial compression tests were conducted on four hollow columns and six FCF-CFS columns, and the failure modes as well as the buckling mechanisms of these specimens are analyzed. Finally, the codes from different countries are used to predict the ultimate capacity of these specimens. The results show that (1) the ultimate capacity of the specimens increased to 37.0∼294.5 % if 10 MPa FCF was used, and the improvement was 70.8∼170.7 % if 6 MPa FCF was used; (2) the FCF mitigated local buckling of the specimens and improved their ductility, however, the final failure modes did not obviously change; (3) although the GB50018–2002 and the AISI-S100 can effectively calculate the ultimate capacity of the hollow specimens, almost all codes cannot accurately predict the ultimate capacity of FCF-CFS specimens due to the complex behavior between the built-up special-shape section and FCF. The results provide insights for performance enhancement of columns in CFS structures.
This paper proposes T-section special shape light-weight foam concrete-filled (FCF) cold-formed steel (CFS) built-up columns, which can be used as the side columns that easily connect CFS shear walls from three directions. Light-weight foam concrete was used to mitigate the buckling failure and to increase loading capacity of the columns. Axial compression tests were conducted on four hollow columns and six FCF-CFS columns, and the failure modes as well as the buckling mechanisms of these specimens are analyzed. Finally, the codes from different countries are used to predict the ultimate capacity of these specimens. The results show that (1) the ultimate capacity of the specimens increased to 37.0∼294.5 % if 10 MPa FCF was used, and the improvement was 70.8∼170.7 % if 6 MPa FCF was used; (2) the FCF mitigated local buckling of the specimens and improved their ductility, however, the final failure modes did not obviously change; (3) although the GB50018–2002 and the AISI-S100 can effectively calculate the ultimate capacity of the hollow specimens, almost all codes cannot accurately predict the ultimate capacity of FCF-CFS specimens due to the complex behavior between the built-up special-shape section and FCF. The results provide insights for performance enhancement of columns in CFS structures.
作者：
Haijun Chen;Yong Cai*;Zong Lai Peng;Yipei Zeng;Xiaoyong Lv;...
期刊：
Structures,2025年77:109109 ISSN：2352-0124
通讯作者：
Yong Cai
作者机构：
[Haijun Chen; Yong Cai; Laifu Zhang] School of Civil Engineering, Central South University, Changsha 410075, China;[Zong Lai Peng; Yipei Zeng] China Construction Fifth Bureau Installation Engineering Co., LTD, China;[Xiaoyong Lv] School of Civil Engineering, Central South University of Forestry and Technology, Changsha 410004, China
通讯机构：
[Yong Cai] S;School of Civil Engineering, Central South University, Changsha 410075, China
摘要：
Structural assessment of roadway bridges is great of importance due to the advanced development of transportation and heavier moving vehicles. In this study, improved closed-form solutions for the vibration behavior of thin-walled beams subjected to the motion of a heavy vehicle are proposed. Initially, the developed governing coupled differential equations of thin-walled beam motions are established for vertical, lateral and torsional directions rooted in the Vlasov and Euler-Bernoulli theories of beams. In practice, a moving vehicle crossing a bridge can also produce harmonic vertical and lateral loads in addition to its own weight, as well as torsional moment induced by the engine's counterbalance. Therefore, the vehicle mass, two-directional tire harmonic loads and the torsional moment of the counterweight are incorporated in the developed equations. Subsequently, employing the differential transformation methods, the closed-form solutions for vibration behavior and bending moment of beams are obtained. Moreover, a thorough comparison of the beam responses with the published literature and FEM demonstrates the correctness of the derived solutions. Finally, an important factor, the dynamic amplification factor (DAF) accounting for dynamic impact of moving vehicles on a bridge, is introduced in an in-depth parametric analysis to explore the effect of the mass inertia and higher-modes vibration and tire harmonic loads on the dynamic responses of beams involving natural frequency, beam deflection, bending moment as well as the critical velocity. The numerical analyses highlight the substantial influence of vehicle mass inertia on roadway bridges, especially with heavier vehicles at higher speeds.
Structural assessment of roadway bridges is great of importance due to the advanced development of transportation and heavier moving vehicles. In this study, improved closed-form solutions for the vibration behavior of thin-walled beams subjected to the motion of a heavy vehicle are proposed. Initially, the developed governing coupled differential equations of thin-walled beam motions are established for vertical, lateral and torsional directions rooted in the Vlasov and Euler-Bernoulli theories of beams. In practice, a moving vehicle crossing a bridge can also produce harmonic vertical and lateral loads in addition to its own weight, as well as torsional moment induced by the engine's counterbalance. Therefore, the vehicle mass, two-directional tire harmonic loads and the torsional moment of the counterweight are incorporated in the developed equations. Subsequently, employing the differential transformation methods, the closed-form solutions for vibration behavior and bending moment of beams are obtained. Moreover, a thorough comparison of the beam responses with the published literature and FEM demonstrates the correctness of the derived solutions. Finally, an important factor, the dynamic amplification factor (DAF) accounting for dynamic impact of moving vehicles on a bridge, is introduced in an in-depth parametric analysis to explore the effect of the mass inertia and higher-modes vibration and tire harmonic loads on the dynamic responses of beams involving natural frequency, beam deflection, bending moment as well as the critical velocity. The numerical analyses highlight the substantial influence of vehicle mass inertia on roadway bridges, especially with heavier vehicles at higher speeds.
摘要：
The high alkalinity of silicate cement in Ecological Porous Concrete (EPC) inhibits plant growth, and synergistically regulating alkalinity and strength is challenging. In this study, a ternary composite alkalinity-reducing system of Diatomite-Oxalic Acid-Ferric Sulfate was proposed. The effects of the composite alkali-reducing system on the pH, mechanical properties, porosity, and permeability coefficient of EPC were systematically analyzed, and XRD, FTIR, TG, and SEM multiscale characterization were used to elucidate the mechanism of alkalinity reduction and strengthening. The results indicated that the composite alkali-reducing system accelerated the cement hydration reaction and significantly consumed Ca(OH)₂, and the pH of the EPC decreased to 8.49 after 56 d. Meanwhile, the iron-rich C-(F)-S-H gel with a low Ca/Si ratio generated in the cementation system synergistically reinforced the matrix structure with AFt crystals. The compressive strength and split tensile strength of EPC at 56 days were enhanced to 14.8 MPa and 1.97 MPa, respectively, under the premise of guaranteeing the porosity (20%-30%). This study provides a theoretical basis for the alkalinity-strength synergistic modulation of EPC, which promotes its application in ecological restoration projects.
The high alkalinity of silicate cement in Ecological Porous Concrete (EPC) inhibits plant growth, and synergistically regulating alkalinity and strength is challenging. In this study, a ternary composite alkalinity-reducing system of Diatomite-Oxalic Acid-Ferric Sulfate was proposed. The effects of the composite alkali-reducing system on the pH, mechanical properties, porosity, and permeability coefficient of EPC were systematically analyzed, and XRD, FTIR, TG, and SEM multiscale characterization were used to elucidate the mechanism of alkalinity reduction and strengthening. The results indicated that the composite alkali-reducing system accelerated the cement hydration reaction and significantly consumed Ca(OH)₂, and the pH of the EPC decreased to 8.49 after 56 d. Meanwhile, the iron-rich C-(F)-S-H gel with a low Ca/Si ratio generated in the cementation system synergistically reinforced the matrix structure with AFt crystals. The compressive strength and split tensile strength of EPC at 56 days were enhanced to 14.8 MPa and 1.97 MPa, respectively, under the premise of guaranteeing the porosity (20%-30%). This study provides a theoretical basis for the alkalinity-strength synergistic modulation of EPC, which promotes its application in ecological restoration projects.
摘要：
Glued-in rod connections (GIRc) in timber or bamboo joints are characterized by high stiffness, strength, and aesthetic appeal. In this study, pullout tests were conducted on 42 specimens of GIRc in side-pressure laminated bamboo lumber (SPLBL) parallel to grain to investigate their failure modes and characteristics. The effects of edge distance, adhesive layer thickness, and slenderness ratio on the mechanical properties of GIRc in SPLBL were discussed. According to the experimental results, four failure modes were observed: splitting failure of SPLBL, splitting failure of the glue layer of SPLBL, pullout failure of the threaded rod, and yielding failure of the threaded rod. The first two failure modes can be avoided by increasing the edge distance and modifying the production process of GIRc, while the load-bearing capacities of the latter two failure modes are primarily determined by the slenderness ratio and the mechanical properties of the threaded rods. The strength and stiffness of the specimens increased with edge distance and slenderness ratio, reaching a peak at an adhesive layer thickness of 2 mm. One-way ANOVA indicated that the slenderness ratio significantly affects the mechanical properties of the specimens. The applicability of existing load-bearing capacity calculation models was discussed. Based on the existing models and experimental data, a prediction equation for the load-bearing capacity of GIRc in SPLBL was proposed. This prediction equation was validated against a database including various engineered bamboo materials, rod materials, and adhesive layer thicknesses, demonstrating superior generality compared to other equations. Finally, a reliability analysis of the GIRc in SPLBL was conducted using the central point method of the first-order second-moment method, and an approximate solution for the critical anchorage slenderness ratio was obtained. The prediction equation and the reliability analysis results can serve as references for the engineering design of GIRc in bamboo structures.
摘要：
In research on using vehicles to extract bridge frequencies, single degree-of-freedom vehicles and two-dimensional bridges cannot fully simulate vehicle-bridge interaction and bridge frequency extraction. Therefore, a method of using two-axle vehicles to extract the vertical and flexural-torsional frequencies of three-dimensional (3D) bridges is proposed. First, the feasibility of this method is theoretically verified by analytical methods. Subsequently, a signal enhancement approach, combining successive variational mode decomposition (SVMD) and a designed window function, is proposed. SVMD performs modal decomposition on vehicle signals, while the window function reduces noise in vehicle signals and enhances bridge signals, resulting in a low-noise spectrum. The investigations indicate that bridge frequencies extracted by the proposed method exhibit a relative error of <5 %, which meets engineering requirements. Moreover, the method is insensitive to vehicle parameters and is not limited by two-axle vehicle types. Notably, vertical acceleration spectra of two-axle vehicles, filtered using the signal enhancement approach, can resist the effect of road roughness noise on bridge frequency identification. This study further advances the vehicle scanning method and offers a practical approach to bridge health monitoring.
In research on using vehicles to extract bridge frequencies, single degree-of-freedom vehicles and two-dimensional bridges cannot fully simulate vehicle-bridge interaction and bridge frequency extraction. Therefore, a method of using two-axle vehicles to extract the vertical and flexural-torsional frequencies of three-dimensional (3D) bridges is proposed. First, the feasibility of this method is theoretically verified by analytical methods. Subsequently, a signal enhancement approach, combining successive variational mode decomposition (SVMD) and a designed window function, is proposed. SVMD performs modal decomposition on vehicle signals, while the window function reduces noise in vehicle signals and enhances bridge signals, resulting in a low-noise spectrum. The investigations indicate that bridge frequencies extracted by the proposed method exhibit a relative error of <5 %, which meets engineering requirements. Moreover, the method is insensitive to vehicle parameters and is not limited by two-axle vehicle types. Notably, vertical acceleration spectra of two-axle vehicles, filtered using the signal enhancement approach, can resist the effect of road roughness noise on bridge frequency identification. This study further advances the vehicle scanning method and offers a practical approach to bridge health monitoring.
作者机构：
[Qin, Hongxi; Liu, Xuan; Tang, Ao] Cent South Univ Forestry & Technol, Sch Civil Engn, Changsha 410004, Peoples R China.;[Deng, Changjun; Zou, Chunrong; Chen, Yang; Hu, Anqing; Deng, CJ] China Railway Southwest Res Inst Co Ltd, Chengdu 611731, Peoples R China.;[Tang, Ao] Hunan Zhongda Digital Innovat Technol Co Ltd, Changsha 410018, Peoples R China.
通讯机构：
[Deng, CJ ] C;China Railway Southwest Res Inst Co Ltd, Chengdu 611731, Peoples R China.
关键词：
structural health monitoring;building information modeling;condition assessment;butterfly arch bridge;remote data management
摘要：
The developments in building information modeling (BIM) technology provide a new approach for remote real-time visualized bridge health monitoring and structural damage detection, but so far, there are scarcely any application cases of a BIM-based SHM system for butterfly arch bridges around the world. This paper reviewed the recent progress on the butterfly arch bridge and its requirements for the integration between SHM and BIM. Based on an actual project in southwest China, work on the spatial mechanical properties, the analysis of monitoring requirements, and the design of functional modules of SHM are elaborately conducted. Subsequently, the lightweight BIM is established and integrated into the web client-side of the SHM system with the skeleton-template method, CATIA platform, and sensor data. With the implementation of user-defined virtual sensor parameter linkage, the design of the specific databases is accomplished in the SQL server environment. Based on one actual incident that saw an overweight/oversize vehicle (with the weight of 80 t, 2015) pass over the arch bridge, the fuzzy relation synthesis and data cleaning method were improved to compare the standard deviation with the threshold value of the correlation degree, and a method is adopted to evaluate the structural operation behavior of the bridge and the service condition of the BIM-based SHM system after the ultra-limit accident. The study results evince the validity and efficiency of the BIM-based SHM system, which could lay a foundation for the visualized assessment and early warning system of long-span bridges.
摘要：
Based on the elaborate 3D solid finite element (FE) model established by ABAQUS software, a pseudo-static analysis was conducted on a special-shaped concrete-filled steel tubular column composite frame structure. The FE model considers the confinement effect of both the steel tubes and the tensile bars exerting on the core concrete. The results of the numerical analysis concerning failure modes, load-displacement hysteretic curves, load-displacement skeleton curves and stiffness degradation-displacement curves demonstrate a strong correlation with the existing quasi-static test data. Furthermore, an in-depth analysis was conducted on the impact of the axial compression ratio of column on the plastic energy dissipation distribution mechanism. With an axial compression ratio of the column ranging from 0.1 to 0.55, the composite frame structure primarily relies on the energy dissipation of beams, while the columns serve as supplementary support, thereby exemplifying the principle of "strong column-weak beam." As the axial compression ratio rises to the range of 0.6-0.8, the composite frame structure transitions a "strong beam-weak column" structural system. Combined with the longitudinal compressive strain of the steel tube at the bottom of the column, a quantitative evaluation method for seismic damage is proposed, grounded in indexes of "stiffness damage" and "energy damage." Then, the threshold values of energy damage and stiffness damage are determined across four distinct levels: "elastic stage in small earthquake," "elasto-plastic stage in medium earthquake," "plastic stage in heavy earthquake" and "failure stage." The proposed method effectively evaluate the damage severity of special-shaped CFT column composite frame structure subjected to seismic events.
