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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    

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    

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    

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    

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    

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    

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    

探索新强韧化机制 开拓超高强度钢新领域

赵振业,李志,刘天琦,朱杰远

《中国工程科学》 2003年 第5卷 第9期   页码 39-42

摘要:

论述了超细化马氏体板条,共格沉淀新强化相(Laves相),M2C碳化物和残余—逆转变奥氏体向马氏体相变诱发塑性等强韧化机理,用超纯洁熔炼、超均匀化及控制相变等工艺,获得一种低碳-14Cr-12Co-5Mo-Me新型超高强度、高塑性、高韧性不锈钢。

关键词: 超高强度不锈钢     马氏体板条     强韧化机理    

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    

一种超高强度钢构件抗疲劳实验研究

赵振业,宋德玉,李向斌,杨树勋,马新闻

《中国工程科学》 2005年 第7卷 第10期   页码 51-55

摘要:

提出了超高强度钢“无应力集中”抗疲劳概念。喷丸、孔挤压、螺纹滚压等表面层组织再造改性造成的残余压应力和高位错密度胞状结构将裂纹推移至亚表面萌生并阻滞其扩展,回复不同应力集中处的疲劳强度至接近钢的固有疲劳强度,形成“无应力集中”表面完整性状态。“无应力集中”抗疲劳概念表述为构件表面形成完整的接近于钢固有疲劳强度的等疲劳强度包络。

关键词: 超高强度钢     抗疲劳     应力集中     表面完整性    

Development and advances in modular multilevel converter based HVDC projects in China

《工程管理前沿(英文)》   页码 183-189 doi: 10.1007/s42524-022-0248-7

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关键词: high voltage direct current     power converter     power systems     renewable energy     ultra-high voltage    

PD pattern recognition based on multi-fractal dimension in GIS

ZHANG Xiaoxing, YAO Yao, TANG Ju, ZHOU Qian, XU Zhongrong

《机械工程前沿(英文)》 2008年 第3卷 第3期   页码 270-275 doi: 10.1007/s11465-008-0042-1

摘要: This paper designs four types of gas insulated substation (GIS) defect models based on partial discharge (PD) characteristics and its defections. The GIS gray intensity images are constructed based on the mass specimens gathered by the ultra-high frequency and high-speed sampling systems. The multi-fractal dimension is founded on the box-counting dimension and multi-fractal theories. The GIS gray intensity images distillation methods, based on multi-fractal characteristics, is put forward. The box-counting dimension, multi-fractal dimension, and discharge centrobaric characteristics of the PD images are also extracted. The characteristic variables are then classified by the radial basis function (RBF) network. Identified results show that the methods can effectively elevate the discrimination of the four types of defects in GIS.

关键词: substation     high-speed     discharge centrobaric     network     ultra-high frequency    

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    

标题 作者 时间 类型 操作

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

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

期刊论文

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

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

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

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

期刊论文

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

期刊论文

探索新强韧化机制 开拓超高强度钢新领域

赵振业,李志,刘天琦,朱杰远

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

一种超高强度钢构件抗疲劳实验研究

赵振业,宋德玉,李向斌,杨树勋,马新闻

期刊论文

Development and advances in modular multilevel converter based HVDC projects in China

期刊论文

PD pattern recognition based on multi-fractal dimension in GIS

ZHANG Xiaoxing, YAO Yao, TANG Ju, ZHOU Qian, XU Zhongrong

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