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Shear behavior of ultra-high-performance concrete beams prestressed with external carbon fiber-reinforced

《结构与土木工程前沿(英文)》 2021年 第15卷 第6期   页码 1426-1440 doi: 10.1007/s11709-021-0783-z

摘要: The ultra-high-performance concrete (UHPC) and fiber-reinforced polymer (FRP) are well-accepted high-performance materials in the field of civil engineering. The combination of these advanced materials could contribute to improvement of structural performance and corrosion resistance. Unfortunately, only limited studies are available for shear behavior of UHPC beams reinforced with FRP bars, and few suggestions exist for prediction methods for shear capacity. This paper presents an experimental investigation on the shear behavior of UHPC beams reinforced with glass FRP (GFRP) and prestressed with external carbon FRP (CFRP) tendons. The failure mode of all specimens with various shear span to depth ratios from 1.7 to 4.5 was diagonal tension failure. The shear span to depth ratio had a significant influence on the shear capacity, and the effective prestressing stress affected the crack propagation. The experimental results were then applied to evaluate the equations given in different codes/recommendations for FRP-reinforced concrete structures or UHPC structures. The comparison results indicate that NF P 18-710 and JSCE CES82 could appropriately estimate shear capacity of the slender specimens with a shear span to depth ratio of 4.5. Further, a new shear design equation was proposed to take into account the effect of the shear span to depth ratio and the steel fiber content on shear capacity.

关键词: beam     external prestressing     ultra-high-performance concrete     fiber-reinforced polymers     shear behavior     design equation    

Performance of steel bridge deck pavement structure with ultra high performance concrete based on resin

《结构与土木工程前沿(英文)》 2021年 第15卷 第4期   页码 895-904 doi: 10.1007/s11709-021-0759-z

摘要: This research investigated a pavement system on steel bridge decks that use epoxy resin (EP) bonded ultra-high performance concrete (UHPC). Through FEM analysis and static and dynamic bending fatigue tests of the composite structure, the influences of the interface of the pavement layer, reinforcement, and different paving materials on the structural performance were compared and analyzed. The results show that the resin bonded UHPC pavement structure can reduce the weld strain in the steel plate by about 32% and the relative deflection between ribs by about 52% under standard axial load conditions compared to traditional pavements. The EP bonding layer can nearly double the drawing strength of the pavement interface from 1.3 MPa, and improve the bending resistance of the UHPC structure on steel bridge decks by about 50%; the bending resistance of reinforced UHPC structures is twice that of unreinforced UHPC structure, and the dynamic deflection of the UHPC pavement structure increases exponentially with increasing fatigue load. The fatigue life is about 1.2 × 107 cycles under a fixed force of 9 kN and a dynamic deflection of 0.35 mm, which meets the requirements for fatigue performance of pavements on steel bridge decks under traffic conditions of large flow and heavy load.

关键词: steel bridge deck pavement     ultra-high-performance concrete     epoxy resin     composite structure     bending fatigue performance    

Experimental investigations of internal energy dissipation during fracture of fiber-reinforced ultra-high-performanceconcrete

Eric N. LANDIS, Roman KRAVCHUK, Dmitry LOSHKOV

《结构与土木工程前沿(英文)》 2019年 第13卷 第1期   页码 190-200 doi: 10.1007/s11709-018-0487-1

摘要: Split-cylinder fracture of fiber-reinforced ultra-high-performance concrete (UHPC) was examined using two complementary techniques: X-ray computed tomography (CT) and acoustic emission (AE). Fifty-mm-diameter specimens of two different fiber types were scanned both before and after load testing. From the CT images, fiber orientation was evaluated to establish optimum and pessimum specimen orientations, at which fibers would have maximum and minimum effect, respectively. As expected, fiber orientation affected both the peak load and the toughness of the specimen, with the optimum toughness being between 20% and 30% higher than the pessimum. Cumulative AE energy was also affected commensurately. Posttest CT scans of the specimens were used to measure internal damage. Damage was quantified in terms of internal energy dissipation due to both matrix cracking and fiber pullout by using calibration measurements for each. The results showed that fiber pullout was the dominant energy dissipation mechanism; however, the sum of the internal energy dissipation measured amounted to only 60% of the total energy dissipated by the specimens as measured by the net work of load. It is postulated that localized compaction of the UHPC matrix as well as internal friction between fractured fragments makes up the balance of internal energy dissipation.

关键词: ultra-high-performance concrete     concrete fracture     X-ray computed tomography     acoustic emission    

Exploring the mechanical properties of steel- and polypropylene-reinforced ultra-high-performance concrete

《结构与土木工程前沿(英文)》   页码 1228-1248 doi: 10.1007/s11709-023-0931-8

摘要: This study presents experimental and numerical investigations on the mechanical properties of ultra-high-performance concrete (UHPC) reinforced with single and hybrid micro- and macro-steel and polypropylene fibers. For this purpose, a series of cubic, cylindrical, dog-bone, and prismatic beam specimens (total fiber by volume = 1%, and 2%) were tested under compressive, tensile, and flexural loadings. A method, namely multi-target digital image correlation (MT-DIC) was used to monitor the displacement and deflection values. The obtained experimental data were subsequently used to discuss influential parameters, i.e., flexural strength, tensile strength, size effect, etc. Numerical analyses were also carried out using finite element software to account for the sensitivity of different parameters. Furthermore, nonlinear regression analyses were conducted to obtain the flexural load-deflection curves. The results showed that the MT-DIC method was capable of estimating the tensile and flexural responses as well as the location of the crack with high accuracy. In addition, the regression analyses showed excellent consistency with the experimental results, with correlation coefficients close to unity. Furthermore, size-effect modeling revealed that modified Bazant theory yielded the best estimation of the size-effect phenomenon compared to other models.

关键词: UHPC     MT-DIC     flexural behavior     tensile behavior     steel fiber     polypropylene fiber    

Connection of the prefabricated updeck of road tunnels by a short lap-spliced joint using ultra-high-performancefiber-reinforced concrete

《结构与土木工程前沿(英文)》   页码 870-883 doi: 10.1007/s11709-023-0977-7

摘要: 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.

关键词: UHPFRC     prefabricated updeck     road tunnel     lap-spliced rebars     flexural tests    

Behavior and strength of headed stud shear connectors in ultra-high performance concrete of composite

Jianan QI, Yuqing HU, Jingquan WANG, Wenchao LI

《结构与土木工程前沿(英文)》 2019年 第13卷 第5期   页码 1138-1149 doi: 10.1007/s11709-019-0542-6

摘要: This study presents an experimental and numerical investigation on the static behavior of headed stud shear connectors in ultra-high performance concrete (UHPC) of composite bridges. Four push-out specimens were tested. It was found that no cracking, crushing or splitting was observed on the concrete slab, indicating that UHPC slab exhibited good performance and could resist the high force transferred from the headed studs. The numerical and experimental results indicated that the shear capacity is supposed to be composed of two parts stud shank shear contribution and concrete wedge block shear contribution. The stiffness increment of a stud in UHPC was at least 60% higher than that in normal strength concrete. Even if the stud height was reduced from 6 to 2 , there was no reduction in the shear strength of a stud. Short stud shear connectors with an aspect ratio as small as 2 could develop full strength in UHPC slabs. An empirical load-slip equation taking into account stud diameter was proposed to predict the load-slip response of a stud. The reliability and accuracy of the proposed load-slip equation was verified by the experimental and numerical load-slip curves.

关键词: ultra-high performance concrete     studs     shear strength     FE analysis     push-out test    

Flexural and longitudinal shear performance of precast lightweight steel–ultra-high performance concrete

《结构与土木工程前沿(英文)》 2023年 第17卷 第5期   页码 704-721 doi: 10.1007/s11709-023-0941-6

摘要: In this study, the flexural and longitudinal shear performances of two types of precast lightweight steel–ultra-high performance concrete (UHPC) composite beams are investigated, where a cluster UHPC slab (CUS) and a normal UHPC slab (NUS) are connected to a steel beam using headed studs through discontinuous shear pockets and full-length shear pockets, respectively. Results show that the longitudinal shear force of the CUS is greater than that of the NUS, whereas the interfacial slip of the former is smaller. Owing to its better integrity, the CUS exhibits greater flexural stiffness and a higher ultimate bearing capacity than the NUS. To further optimize the design parameters of the CUS, a parametric study is conducted to investigate their effects on the flexural and longitudinal shear performances. The square shear pocket is shown to be more applicable for the CUS, as the optimal spacing between two shear pockets is 650 mm. Moreover, a design method for transverse reinforcement is proposed; the transverse reinforcement is used to withstand the splitting force caused by studs in the shear pocket and prevent the UHPC slab from cracking. According to calculation results, the transverse reinforcement can be canceled when the compressive strength of UHPC is 150 MPa and the volume fraction of steel fiber exceeds 2.0%.

关键词: precast steel–UHPC composite beam     flexural performance     longitudinal shear performance     parametric study     transverse reinforcement ratio    

超高性能混凝土中钢纤维-基体界面粘结的研究 Review

邓毓琳, 张祖华, 史才军, 吴泽媚, 张超慧

《工程(英文)》 2023年 第22卷 第3期   页码 215-232 doi: 10.1016/j.eng.2021.11.019

摘要:

超高性能混凝土(UHPC)是一种相对较新的水泥混凝土复合材料,由于其优异的机械强度和耐久性,在基础设施建设中具有巨大的应用潜力。钢纤维与基体的界面粘结性能是决定UHPC其他力学性能的主要因素,包括抗拉、弯曲、抗压强度和破坏模式(断裂行为)。本文通过讨论并比较多种纤维拉拔测试方法和分析模型,全面综述了UHPC的纤维-基体粘结行为的研究进展;详细确定并讨论了影响纤维-基体粘结的参数,包括纤维的几何形状和方向、表面处理、基体的组成和强度。最后,基于现有研究,对未来UHPC增强方法和测试细节提出了建议。

关键词: 超高性能混凝土     界面粘结     钢纤维     拉拔行为    

300m 级特高拱坝建设关键技术与实践

王仁坤

《工程(英文)》 2016年 第2卷 第3期   页码 350-359 doi: 10.1016/J.ENG.2016.03.012

摘要:

中国于2000 年成功建设二滩拱坝( 高240 m)以来,至2014 年年底已建成7 座坝高超过200 m 的特高拱坝,其中锦屏一级拱坝(高305 m)、小湾拱坝(高294.5 m)、溪洛渡拱坝(高285.5 m)不仅坝高达300 m 级,而且因地质条件复杂,水推力巨大,抗震要求高,在安全控制技术等方面取得了新的突破。本文主要阐述300 m 级特高拱坝的基础可利用岩体及合理建基面、体形优化设计、安全设计准则、抗震研究与抗震措施、复杂地基的典型处理、混凝土及施工期温控防裂等关键技术。

关键词: 特高拱坝     优化设计     整体安全     抗震安全     混凝土温控    

Effect of cavity defect on the triaxial mechanical properties of high-performance concrete

Yanbin ZHANG; Zhe WANG; Mingyu FENG

《结构与土木工程前沿(英文)》 2022年 第16卷 第5期   页码 600-614 doi: 10.1007/s11709-022-0821-5

摘要: The stress concentration of pipe structure or cavity defect has a great effect on the mechanical properties of the high-performance concrete (HPC) members in deep underground locations. However, the behaviour of HPC with cavities under triaxial compression is not understood, especially when pressurized liquid flows into the fractures from the cavity. This study aims to investigate the effect of the cavity and the confining pressure on the failure mechanisms, strengths, and deformation properties of HPC with a new experimental scheme. In this experiment, the pressurized liquid can only contact the surface of the sample in the cavity, while the other surfaces are isolated from the pressurized liquid. To further explore the effect of the cavity, the same experiments are also conducted on sealed and unsealed intact samples without a cavity. The failure modes and stress-strain curves of all types of the samples are presented. Under various confining pressures, all the samples with a cavity suffer shear failure, and there are always secondary tensile fractures initiating from the cavity sidewall. Additionally, it can be determined from the failure modes and the stress-strain curves that the shear fractures result from the sidewall failure. Based on the different effects of the cavity on the lateral deformations in different directions, the initiation of the sidewall fracture is well predicted. The experimental results show that both the increase of the confining pressure and the decrease of the cavity size are conducive to the initiation of sidewall fracture. Moreover, the cavity weakens the strength of the sample, and this study gives a modified Power-law criterion in which the cavity size is added as an impact factor to predict the strength of the sample.

关键词: high-performance concrete     cavity     conventional triaxial compression     pressurized liquid     modified power-law criterion    

Fresh and hardened properties of high-performance fiber-reinforced concrete containing fly ash and rice

Nguyen-Trong HO; Viet Quoc DANG; Minh-Hieu NGUYEN; Chao-Lung HWANG; Trong-Phuoc HUYNH

《结构与土木工程前沿(英文)》 2022年 第16卷 第12期   页码 1621-1632 doi: 10.1007/s11709-022-0884-3

摘要: Although fibers are used only infrequently as an additive in concrete in the construction industry, fiber-enhanced concrete is known to provide a wide range of advantages over conventional concrete. The main objective of this study was to investigate the influences of fiber type and content on the mechanical properties and durability of high-performance fiber-reinforced concrete (HPFRC) designed using a novel densified mixture design algorithm with fly ash and rice husk ash. Three types of fiber, including polypropylene (PP) fiber, steel fiber (SF), and hybrid fiber (HF), were considered. Based on the results, the inclusion of fibers decreased HPFRC flowability, regardless of fiber type. Although the compressive strength of HPFRC with 1.6% PP fiber content was 11.2% below that of the reference HPFRC specimen at 91 d of curing age, the 91-d compressive strengths of both SF and HF-enhanced HPFRC specimens were significantly better than that of the reference HPFRC specimen. Furthermore, the HPFRC specimens incorporating SF and HF both exhibited better splitting tensile and flexural strengths as well as less drying shrinkage than the HPFRC specimens incorporating PP fiber. However, the fiber-enhanced specimens, especially those with added SF, registered less surface electrical resistivity and greater vulnerability to chloride ion penetration than the reference HPFRC specimen.

关键词: high-performance fiber-reinforced concrete     fly ash     rice husk ash     durability     mechanical strength    

Key technical innovations in the construction of Baihetan Hydropower Station Project

《工程管理前沿(英文)》 2023年 第10卷 第2期   页码 367-372 doi: 10.1007/s42524-023-0253-5

摘要: Key technical innovations in the construction of Baihetan Hydropower Station Project

关键词: ultra-high arch dam     columnar jointed basalt     low-heat cement concrete     temperature controlled crack prevention     million-kilowatt unit     intelligent construction    

通过官能团化处理提高碳纳米管对超高性能混凝土抗冲击性能的增强效果 Article

王佳亮, 董素芬, Sze Dai Pang, 余逊, 韩宝国, 欧进萍

《工程(英文)》 2022年 第18卷 第11期   页码 232-245 doi: 10.1016/j.eng.2021.04.030

摘要:

使用碳纳米管替代微米级纤维可增强超高性能混凝土(ultra-high performance concrete, UHPC)的抗冲击性能,

关键词: 官能团化碳纳米管     混凝土     抗冲击性能     增强机理    

大掺量矿物掺合料高性能混凝土在京沪高铁四标段中的应用

高治双,赵年全,赵常煜,胡明文,苟云龙

《中国工程科学》 2009年 第11卷 第1期   页码 26-31

摘要:

以京沪高速铁路为工程背景,试验研究了矿物掺合料(粉煤灰、粉煤灰-矿粉)对混凝土工作性能、力学性能和耐久性能的影响以及大掺量矿物掺合料高性能混凝土的配制技术。结合实际工程,介绍了大掺量矿物掺合料高性能混凝土原材料选择、配合比设计、施工工艺等方面的控制技术。

关键词: 矿物掺合料     大掺量矿物掺合料高性能混凝土     配制与施工     质量控制    

CC@BCN@PANI core-shell nanoarrays as ultra-high cycle stability cathode for Zn-ion hybrid supercapacitors

《能源前沿(英文)》 2023年 第17卷 第4期   页码 555-566 doi: 10.1007/s11708-023-0882-8

摘要: Exploring cathode materials that combine excellent cycling stability and high energy density poses a challenge to aqueous Zn-ion hybrid supercapacitors (ZHSCs). Herein, polyaniline (PANI) coated boron-carbon-nitrogen (BCN) nanoarray on carbon cloth surface is prepared as advanced cathode materials via simple high-temperature calcination and electrochemical deposition methods. Because of the excellent specific capacity and conductivity of PANI, the CC@BCN@PANI core-shell nanoarrays cathode shows an excellent ion storage capability. Moreover, the 3D nanoarray structure can provide enough space for the volume expansion and contraction of PANI in the charging/discharging cycles, which effectively avoids the collapse of the microstructure and greatly improves the electrochemical stability of PANI. Therefore, the CC@BCN@PANI-based ZHSCs exhibit superior electrochemical performances showing a specific capacity of 145.8 mAh/g, a high energy density of 116.78 Wh/kg, an excellent power density of 12 kW/kg, and a capacity retention rate of 86.2% after 8000 charge/discharge cycles at a current density of 2 A/g. In addition, the flexible ZHSCs (FZHSCs) also show a capacity retention rate of 87.7% at the current density of 2 A/g after 450 cycles.

关键词: CC@BCN@PANI cathode     Zn-ion hybrid supercapacitor     core-shell nanoarrays     high energy density     ultra-high cycle stability    

标题 作者 时间 类型 操作

Shear behavior of ultra-high-performance concrete beams prestressed with external carbon fiber-reinforced

期刊论文

Performance of steel bridge deck pavement structure with ultra high performance concrete based on resin

期刊论文

Experimental investigations of internal energy dissipation during fracture of fiber-reinforced ultra-high-performanceconcrete

Eric N. LANDIS, Roman KRAVCHUK, Dmitry LOSHKOV

期刊论文

Exploring the mechanical properties of steel- and polypropylene-reinforced ultra-high-performance concrete

期刊论文

Connection of the prefabricated updeck of road tunnels by a short lap-spliced joint using ultra-high-performancefiber-reinforced concrete

期刊论文

Behavior and strength of headed stud shear connectors in ultra-high performance concrete of composite

Jianan QI, Yuqing HU, Jingquan WANG, Wenchao LI

期刊论文

Flexural and longitudinal shear performance of precast lightweight steel–ultra-high performance concrete

期刊论文

超高性能混凝土中钢纤维-基体界面粘结的研究

邓毓琳, 张祖华, 史才军, 吴泽媚, 张超慧

期刊论文

300m 级特高拱坝建设关键技术与实践

王仁坤

期刊论文

Effect of cavity defect on the triaxial mechanical properties of high-performance concrete

Yanbin ZHANG; Zhe WANG; Mingyu FENG

期刊论文

Fresh and hardened properties of high-performance fiber-reinforced concrete containing fly ash and rice

Nguyen-Trong HO; Viet Quoc DANG; Minh-Hieu NGUYEN; Chao-Lung HWANG; Trong-Phuoc HUYNH

期刊论文

Key technical innovations in the construction of Baihetan Hydropower Station Project

期刊论文

通过官能团化处理提高碳纳米管对超高性能混凝土抗冲击性能的增强效果

王佳亮, 董素芬, Sze Dai Pang, 余逊, 韩宝国, 欧进萍

期刊论文

大掺量矿物掺合料高性能混凝土在京沪高铁四标段中的应用

高治双,赵年全,赵常煜,胡明文,苟云龙

期刊论文

CC@BCN@PANI core-shell nanoarrays as ultra-high cycle stability cathode for Zn-ion hybrid supercapacitors

期刊论文