Limited research has been conducted on the influences of fiber content on close-in blasting characteristics for ultrahigh-performance fiber-reinforced concrete(UHPFRC)beams.This paper aims to address this knowledge ga...Limited research has been conducted on the influences of fiber content on close-in blasting characteristics for ultrahigh-performance fiber-reinforced concrete(UHPFRC)beams.This paper aims to address this knowledge gap through experimental and mesoscale numerical methods.Experiments were conducted on ten UHPFRC beams built with varying steel fiber volumetric fractions subjected to close-in explosive conditions.Additionally,this study considered other parameters,such as the longitudinal reinforcement type and ratio.In the case of UHPFRC beams featuring normal-strength longitudinal reinforcement of diametersΦ12,Φ16,andΦ20,a reduction in maximum displacement by magnitudes of19.6%,19.5%,and 17.4%was observed,respectively,as the volumetric fractions of fiber increased from1.0%to 2.5%.In addition,increasing the longitudinal reinforcement ratio and using high-strength steel longitudinal reinforcement both significantly reduced the deformation characteristics and increase the blasting resistances of UHPFRC beams.However,the effects on the local crushing and spalling damage were not significant.A mesoscale finite element model,which considers the impacts of fiber parameters on UHPFRC beam behaviors,was also established and well correlated with the test findings.Nevertheless,parametric analyses were further conducted to examine the impacts of the steel fiber content and length and the hybrid effects of various types of microfibers and steel fibers on the blasting performance of UHPFRC beams.展开更多
The aim of the Student Workshop “Material Optimization and Geometric Exploration” (ENSA Paris-Belleville and University of Naples Federico II) is to discover the possibilities offered by new materials, starting from...The aim of the Student Workshop “Material Optimization and Geometric Exploration” (ENSA Paris-Belleville and University of Naples Federico II) is to discover the possibilities offered by new materials, starting from their characteristics. The final goal is to build a synthetic pavilion, which in the last session demonstrates ultra-high performances fibre reinforced concrete (UHPFRC) capacities. Designing with UHPFRC requires thinking simultaneously about the geometry, the static, the casting (mainly precast) and the implementation process. The design of the pavilion starts with a widespread geometric exploration using a phylogenetic tree. This approach has the advantage of exploring different designs at the same time without enclosing the creative process in one path. The geometry of the final pavilion is based on a folded surface, called “Yoshimura”, made out of rows of triangles. The profile of the pavilion is bent in order to create a double curvature and so, more stability. The modules are multiplied asymmetrically to minimize the number of the moulds, having at the end just one mould for each row of triangles. The moulds are made with polyethylene terephthalate glycol (PETG) laser-cut sheets which have been folded afterwards. This process has been chosen for both the smooth finishing it delivers and the simplicity of the fabrication process.展开更多
The present paper focuses on compressive strength of Ultra High Performance Fiber Reinforced Concrete (UHPFRC) cube and cylinder under compression testing machine, the experimental determination of test results shows ...The present paper focuses on compressive strength of Ultra High Performance Fiber Reinforced Concrete (UHPFRC) cube and cylinder under compression testing machine, the experimental determination of test results shows +5% variation in compressive strength, differs from normal concrete +20% the ascending in strength development at an increased age under an elevated temperature of the material is identified with addition of hooked end steel fiber. In this study, the optimized mix design developed and the conversion ratios determined to develop relationship between cube and cylinder. The comparison between mean compressive strength ratio for cube and cylinder has been presented to determine high compressive strength. The research work is carried out to achieve enhanced target compressive strength 180 N/mm2.展开更多
Use of UHPFRC(ultra high performance fiber reinforced concrete)cast-in-situ over-lays for repairs and strengthening of bridge decks is already quite a widely used technology,while use of this method for strengthening ...Use of UHPFRC(ultra high performance fiber reinforced concrete)cast-in-situ over-lays for repairs and strengthening of bridge decks is already quite a widely used technology,while use of this method for strengthening of bridge supports is still much less often.This paper describes the first use of this technology for bridge abutments in the Czech Republic,and if we know well,also the first use of such a ribbed over-lay internationally.展开更多
SFRC(钢纤维混凝土)与UHPFRC(超高性能混凝土)是钢桥铺装上常用的两种纤维增强混凝土组合桥面结构.为探究组合桥面结构在局部轮载作用下的受弯性能,本文分别对12 mm钢-75 mm SFRC组合板与12 mm钢-60 mm UHPFRC组合板进行弯拉试验研究,...SFRC(钢纤维混凝土)与UHPFRC(超高性能混凝土)是钢桥铺装上常用的两种纤维增强混凝土组合桥面结构.为探究组合桥面结构在局部轮载作用下的受弯性能,本文分别对12 mm钢-75 mm SFRC组合板与12 mm钢-60 mm UHPFRC组合板进行弯拉试验研究,以探究负弯矩作用下组合板的抗弯性能.试验发现钢-UHPFRC组合板开裂弯矩与极限弯矩均显著大于钢-SFRC组合板;两种组合板在弯拉受力下纯弯段裂缝分布都十分密集,且裂缝宽度小于0.2 mm时,荷载与最大裂缝宽度的关系近似线性;两者破坏形态均为纤维混凝土层受拉断裂.按截面换算法计算UHPFRC层和SFRC层的开裂强度分别为26.42,12.37 MPa,可见在车轮荷载作用下与SFRC桥面板相比,UHPFRC桥面板抗裂性能更好,极限抗弯拉承载力大大提高,表明其抗弯拉和疲劳性能得到增强;按塑性分析方法计算钢-纤维混凝土组合板的抗弯承载力,与试验值近似吻合.展开更多
Prefabricated internal structures of road tunnels,consisting of precast elements and the connections between them,provide advantages in terms of quality control and manufacturing costs.However,the limited construction...Prefabricated internal structures of road tunnels,consisting of precast elements and the connections between them,provide advantages in terms of quality control and manufacturing costs.However,the limited construction space in tunnels creates challenges for on-site assembly.To identify feasible connecting joints,flexural tests of precast straight beams connected by welding-spliced or lap-spliced reinforcements embedded in normal concrete or ultra-high-performance fiber-reinforced concrete(UHPFRC)are first performed and analyzed.With an improvement in the strength grade of the closure concrete for the lap-spliced joint,the failure of the beam transforms from a brittle splitting mode to a ductile flexural mode.The beam connected by UHPFRC100 with short lap-spliced reinforcements can achieve almost equivalent mechanical performance in terms of the bearing capacity,ductility,and stiffness as the beam connected by normal concrete with welding-spliced reinforcements.This favorable solution is then applied to the connection of neighboring updeck slabs resting on columns in a double-deck tunnel.The applicability is validated by flexural tests of T-shaped joints,which,fail in a ductile fashion dominated by the ultimate bearing capacity of the precast elements,similar to the corresponding straight beam.The utilization of UHPFRC significantly reduces the required lap-splice length of reinforcements owing to its strong bonding strength.展开更多
The aim of this study is to develop concrete composites that are resistant to armor-piercing projectiles for defense structures.Different reinforcement configurations have been tested,such as short steel fibers,long s...The aim of this study is to develop concrete composites that are resistant to armor-piercing projectiles for defense structures.Different reinforcement configurations have been tested,such as short steel fibers,long steel fibers,and steel mesh reinforcement.Three different concrete mix designs were prepared as“Ultra High Performance(UHPFRC),High Performance(HPFRC)and Conventional(CFRC)Fiber Reinforced Concrete”.The content of hybrid steel fibers was approximately 5%in the UHPFRC and HPFRC mixtures,while the steel fiber content was approximately 2.5%in the CFRC mixture.In addition,a plain state of each mixture was produced.Mechanical properties of concrete were determined in experimental studies.In addition to the fracture energy and impact strength,two important indicators of ballistic performance of concrete are examined,which are the penetration depth and damage area.The results of the study show that the depth of penetration in UHPFRC was around 35%less than that in HPFRC.It was determined that the mixtures of UHPFRC and HPFRC containing 5%by volume of hybrid steel fibers showed superior performance(smaller crater diameter and the less projectile penetration depth)against armor-piercing projectiles in ballistic tests and could be used in defense structures.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.12102050)the Open Fund of State Key Laboratory of Explosion Science and Technology(Grant No.SKLEST-ZZ-21-18)。
文摘Limited research has been conducted on the influences of fiber content on close-in blasting characteristics for ultrahigh-performance fiber-reinforced concrete(UHPFRC)beams.This paper aims to address this knowledge gap through experimental and mesoscale numerical methods.Experiments were conducted on ten UHPFRC beams built with varying steel fiber volumetric fractions subjected to close-in explosive conditions.Additionally,this study considered other parameters,such as the longitudinal reinforcement type and ratio.In the case of UHPFRC beams featuring normal-strength longitudinal reinforcement of diametersΦ12,Φ16,andΦ20,a reduction in maximum displacement by magnitudes of19.6%,19.5%,and 17.4%was observed,respectively,as the volumetric fractions of fiber increased from1.0%to 2.5%.In addition,increasing the longitudinal reinforcement ratio and using high-strength steel longitudinal reinforcement both significantly reduced the deformation characteristics and increase the blasting resistances of UHPFRC beams.However,the effects on the local crushing and spalling damage were not significant.A mesoscale finite element model,which considers the impacts of fiber parameters on UHPFRC beam behaviors,was also established and well correlated with the test findings.Nevertheless,parametric analyses were further conducted to examine the impacts of the steel fiber content and length and the hybrid effects of various types of microfibers and steel fibers on the blasting performance of UHPFRC beams.
文摘The aim of the Student Workshop “Material Optimization and Geometric Exploration” (ENSA Paris-Belleville and University of Naples Federico II) is to discover the possibilities offered by new materials, starting from their characteristics. The final goal is to build a synthetic pavilion, which in the last session demonstrates ultra-high performances fibre reinforced concrete (UHPFRC) capacities. Designing with UHPFRC requires thinking simultaneously about the geometry, the static, the casting (mainly precast) and the implementation process. The design of the pavilion starts with a widespread geometric exploration using a phylogenetic tree. This approach has the advantage of exploring different designs at the same time without enclosing the creative process in one path. The geometry of the final pavilion is based on a folded surface, called “Yoshimura”, made out of rows of triangles. The profile of the pavilion is bent in order to create a double curvature and so, more stability. The modules are multiplied asymmetrically to minimize the number of the moulds, having at the end just one mould for each row of triangles. The moulds are made with polyethylene terephthalate glycol (PETG) laser-cut sheets which have been folded afterwards. This process has been chosen for both the smooth finishing it delivers and the simplicity of the fabrication process.
文摘The present paper focuses on compressive strength of Ultra High Performance Fiber Reinforced Concrete (UHPFRC) cube and cylinder under compression testing machine, the experimental determination of test results shows +5% variation in compressive strength, differs from normal concrete +20% the ascending in strength development at an increased age under an elevated temperature of the material is identified with addition of hooked end steel fiber. In this study, the optimized mix design developed and the conversion ratios determined to develop relationship between cube and cylinder. The comparison between mean compressive strength ratio for cube and cylinder has been presented to determine high compressive strength. The research work is carried out to achieve enhanced target compressive strength 180 N/mm2.
基金For reconstruction of the bridge,results of research projects FV20472(TRIO)SGS20/108/OHK1/2T/11(CTU in Prague)were partly used.
文摘Use of UHPFRC(ultra high performance fiber reinforced concrete)cast-in-situ over-lays for repairs and strengthening of bridge decks is already quite a widely used technology,while use of this method for strengthening of bridge supports is still much less often.This paper describes the first use of this technology for bridge abutments in the Czech Republic,and if we know well,also the first use of such a ribbed over-lay internationally.
文摘SFRC(钢纤维混凝土)与UHPFRC(超高性能混凝土)是钢桥铺装上常用的两种纤维增强混凝土组合桥面结构.为探究组合桥面结构在局部轮载作用下的受弯性能,本文分别对12 mm钢-75 mm SFRC组合板与12 mm钢-60 mm UHPFRC组合板进行弯拉试验研究,以探究负弯矩作用下组合板的抗弯性能.试验发现钢-UHPFRC组合板开裂弯矩与极限弯矩均显著大于钢-SFRC组合板;两种组合板在弯拉受力下纯弯段裂缝分布都十分密集,且裂缝宽度小于0.2 mm时,荷载与最大裂缝宽度的关系近似线性;两者破坏形态均为纤维混凝土层受拉断裂.按截面换算法计算UHPFRC层和SFRC层的开裂强度分别为26.42,12.37 MPa,可见在车轮荷载作用下与SFRC桥面板相比,UHPFRC桥面板抗裂性能更好,极限抗弯拉承载力大大提高,表明其抗弯拉和疲劳性能得到增强;按塑性分析方法计算钢-纤维混凝土组合板的抗弯承载力,与试验值近似吻合.
基金The work of the first author was sponsored by the Shanghai Pujiang Program(No.20PJ1406100)the National Natural Science Foundation of China(Grant No.52208398)+1 种基金In addition,the financial support from the Sino-German Center for Research Promotion,provided within project GZ 1574,is gratefully acknowledged.The last author acknowledges financial support from the Science and Technology Commission of Shanghai Municipality(No.21DZ1203504)the National Natural Science Foundation of China(Grant No.51808336).Moreover,the interesting discussions with Mr.Enjie HU are gratefully acknowledged.
文摘Prefabricated internal structures of road tunnels,consisting of precast elements and the connections between them,provide advantages in terms of quality control and manufacturing costs.However,the limited construction space in tunnels creates challenges for on-site assembly.To identify feasible connecting joints,flexural tests of precast straight beams connected by welding-spliced or lap-spliced reinforcements embedded in normal concrete or ultra-high-performance fiber-reinforced concrete(UHPFRC)are first performed and analyzed.With an improvement in the strength grade of the closure concrete for the lap-spliced joint,the failure of the beam transforms from a brittle splitting mode to a ductile flexural mode.The beam connected by UHPFRC100 with short lap-spliced reinforcements can achieve almost equivalent mechanical performance in terms of the bearing capacity,ductility,and stiffness as the beam connected by normal concrete with welding-spliced reinforcements.This favorable solution is then applied to the connection of neighboring updeck slabs resting on columns in a double-deck tunnel.The applicability is validated by flexural tests of T-shaped joints,which,fail in a ductile fashion dominated by the ultimate bearing capacity of the precast elements,similar to the corresponding straight beam.The utilization of UHPFRC significantly reduces the required lap-splice length of reinforcements owing to its strong bonding strength.
基金This work was completed when the first author was R&D Manager at ISTON.The authors would like to thank ISTON Corporation and its R&D employees for their contributions.
文摘The aim of this study is to develop concrete composites that are resistant to armor-piercing projectiles for defense structures.Different reinforcement configurations have been tested,such as short steel fibers,long steel fibers,and steel mesh reinforcement.Three different concrete mix designs were prepared as“Ultra High Performance(UHPFRC),High Performance(HPFRC)and Conventional(CFRC)Fiber Reinforced Concrete”.The content of hybrid steel fibers was approximately 5%in the UHPFRC and HPFRC mixtures,while the steel fiber content was approximately 2.5%in the CFRC mixture.In addition,a plain state of each mixture was produced.Mechanical properties of concrete were determined in experimental studies.In addition to the fracture energy and impact strength,two important indicators of ballistic performance of concrete are examined,which are the penetration depth and damage area.The results of the study show that the depth of penetration in UHPFRC was around 35%less than that in HPFRC.It was determined that the mixtures of UHPFRC and HPFRC containing 5%by volume of hybrid steel fibers showed superior performance(smaller crater diameter and the less projectile penetration depth)against armor-piercing projectiles in ballistic tests and could be used in defense structures.
