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混凝土 17

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Ductility improvement of GFRP-RC beams using precast confined concrete block in compression zone

《结构与土木工程前沿(英文)》 doi: 10.1007/s11709-023-0968-8

摘要: Fiber-reinforced polymers (FRPs) have received considerable research attention because of their high strength, corrosion resistance, and low weight. However, owing to the lack of ductility in this material and the quasi-brittle behavior of concrete, FRP-reinforced concrete (FRP-RC) beams, even with flexural failure, do not fail in a ductile manner. Because the limited deformation capacity of FRP-RC beams depends on the ductility of their compression zones, the present study proposes using a precast confined concrete block (PCCB) in the compression zone to improve the ductility of the beams. A control beam and four beams with different PCCBs were cast and tested under four-point bending conditions. The control beam failed due to shear, and the PCCBs exhibited different confinements and perforations. The goal was to find an appropriate PCCB for use in the compression zone of the beams, which not only improved the ductility but also changed the failure mode of the beams from shear to flexural. Among the employed blocks, a ductile PCCB with low equivalent compressive strength increased the ductility ratio of the beam to twice that of the control beam. The beam failed in pure flexure with considerable deformation capacity and without significant stiffness reduction.

关键词: ductility     four-point bending test     glass fiber-reinforced polymer     precast confined concrete block    

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    

Structural performance of a façade precast concrete sandwich panel enabled by a bar-type basalt fiber-reinforced

《结构与土木工程前沿(英文)》 2023年 第17卷 第1期   页码 122-137 doi: 10.1007/s11709-022-0894-1

摘要: In this study, a novel diagonally inserted bar-type basalt fiber reinforced polymer (BFRP) connector was proposed, aiming to achieve both construction convenience and partially composite behavior in precast concrete sandwich panels (PCSPs). First, pull-out tests were conducted to evaluate the anchoring performance of the connector in concrete after exposure to different temperatures. Thereafter, direct shear tests were conducted to investigate the shear performance of the connector. After the test on the individual performance of the connector, five façade PCSP specimens with the bar-type BFRP connector were fabricated, and the out-of-plane flexural performance was tested under a uniformly distributed load. The investigating parameters included the panel length, opening condition, and boundary condition. The results obtained in this study primarily indicated that 1) the bar-type BFRP connector can achieve a reliable anchorage system in concrete; 2) the bar-type BFRP connector can offer sufficient stiffness and capacity to achieve a partially composite PCSP; 3) the boundary condition of the panel considerably influenced the out-of-plane flexural performance and composite action of the investigated façade PCSP.

关键词: precast concrete sandwich panel     basalt fiber reinforced polymer     pull-out performance     shear performance     out-of-plane flexural performance    

Seismic response of precast reinforced concrete wall subjected to cyclic in-plane and constant out-of-plane

《结构与土木工程前沿(英文)》 2021年 第15卷 第5期   页码 1128-1143 doi: 10.1007/s11709-021-0753-5

摘要: This paper provides insight into the seismic behavior of a full-scale precast reinforced concrete wall under in-plane cyclic loading combined with out-of-plane loading replicated by sand backfill to simulate the actual condition of basement walls. The tested wall exhibited flexural cracks, owing to the high aspect ratio and considerable out-of-plane movement due to lateral pressure from the backfill. The wall performed satisfactorily by exhibiting competent seismic parameters and deformation characteristics governed by its ductile response in the nonlinear phase during the test with smaller residual drift. Numerical analysis was conducted to validate experimental findings, which complied with each other. The numerical model was used to conduct parametric studies to study the effect of backfill density and aspect ratio on seismic response of the proposed precast wall system. The in-plane capacity of walls reduced, while deformation characteristics were unaffected by the increase in backfill density. An increase in aspect ratio leads to a reduction in in-plane capacity and an increase in drift. Curves between the ratio of in-plane yield capacity and design shear load of walls are proposed for the backfill density, which may be adopted to determine the in-plane yield capacity of the basement walls based on their design shear.

关键词: precast wall     basement wall     out-of-plane response     quasi-static test     sand backfill     seismic parameters    

Construction Technology of Off-Site Precast Concrete Buildings

Ting Gong,Jian Yang,Hao Hu,Feng Xu

《工程管理前沿(英文)》 2015年 第2卷 第2期   页码 122-124 doi: 10.15302/J-FEM-2015039

摘要: The industrialization of building construction is gradually becoming a new choice of construction technology driven by some great advantages such as high efficiency in construction, low energy consumption and environmental friendliness. Construction management plays an important part to ensure the quality of projects. A comparison between traditional on-site and modern off-site construction methods has been conducted. The streamlining of the process including the fabrication, transportation, stacking and assembling of precast components has also been analyzed with a discussion on the BIM application in the process.

关键词: off-site construction     precast concrete     modular construction     construction management     building information model (BIM)    

Factors affecting the seismic behavior of segmental precast bridge columns

Haitham DAWOOD,Mohamed ELGAWADY,Joshua HEWES

《结构与土木工程前沿(英文)》 2014年 第8卷 第4期   页码 388-398 doi: 10.1007/s11709-014-0264-8

摘要: This manuscript discusses the design parameters that potentially affect the lateral seismic response of segmental precast post-tensioned bridge piers. The piers consist of precast circular cross section segments stacked one on top of the other with concentric tendons passing through ducts made in the segments during casting. The bottommost segments of the piers were encased in steel tubes to enhance ductility and minimize damage. An FE model was used to investigate different design parameters and how they influence the lateral force – displacement response of the piers. Design parameters investigated included the initial post-tensioning stress as a percentage of the tendon yield stress, the applied axial stresses on concrete due to post-tensioning, pier aspect ratios, construction details, steel tube thicknesses, and internal mild steel rebar added as energy dissipaters. Based on the data presented, an initial tendon stress in the range of 40%-60% of its yield stress and initial axial stress on concrete of approximately 20% of the concrete’s characteristic strength is appropriate for most typical designs. These design values will prevent tendon yielding until lateral drift angle reaches approximately 4.5%. Changing the steel tube thickness, height, or a combination of both proved to be an effective parameter that may be used to reach a target performance level at a specific seismic zone.

关键词: finite element analysis     concrete     precast units     bridges    

Seismic performance of precast hollow bridge piers with different construction details

Zhiqiang WANG,Jiping GE,Hongyi WEI

《结构与土木工程前沿(英文)》 2014年 第8卷 第4期   页码 399-413 doi: 10.1007/s11709-014-0273-7

摘要: Currently the design scheme of precast hollow concrete bridge piers will be adopted in bridge design in China, but there is no code including specific design details of precast segmental piers in high seismic risk area. For comparative study of seismic performance of the hollow bridge piers which had different design details, six specimens of hollow section bridge pier were designed and tested. The specimens consist of the monolithic cast-in-place concrete bridge pier, precast segmental prestressed pier with cast-in-place joint and precast segmental concrete bridge pier with dry joints. Results show that all specimens have good displacement capacity. The bridge pier with bonded prestressed strands exhibits better energy dissipation capacity and higher strength. The un-bonded prestressed strand bridge pier displays less residual plastic displacement and energy dissipation capacity. The bridge pier with both bonded prestressed strands at the edge of the section and un-bonded in the center of the section not only exhibits more ductility capacity and less residual plastic displacement, but also shows better energy dissipation capacity. Compared with experimental results of prestressed bridge columns, analytical result demonstrates the developed numerical analysis model would provide the reasonable and accurate results.

关键词: hollow pier     seismic performance     cyclic load     precast concrete     bridge columns    

高强钢筋混凝土预制弧板井壁力学特性分析

荣传新,王秀喜,程桦

《中国工程科学》 2005年 第7卷 第7期   页码 43-49

摘要:

对高强钢筋混凝土预制弧板井壁结构的研究表明,实验结果与数值计算结果基本一致。高强钢筋混凝土预制弧板井壁结构具有很高的承载能力,影响其承载能力的主要因素依次为混凝土的强度等级、厚径比和配筋率。在均布荷载作用下,混凝土的强度等级提高10MPa,极限承载力提高1.26MPa。厚径比每增加1%,极限承载力增加0.85 MPa。增大配筋率对提高其极限承载力作用不大,配筋率增大3倍,极限承载力只增加了0.1MPa。

关键词: 高强钢筋混凝土预制弧板井壁     力学特性     有限元法     ANSYS    

体内-体外混合配束节段预制拼装箱梁足尺模型试验研究

郑开启,卜红旗,刘钊,惠卓,吕志涛

《中国工程科学》 2013年 第15卷 第8期   页码 89-94

摘要:

以南京长江第四大桥引桥为背景,开展了一孔48 m跨径体内-体外混合配束节段预制拼装箱梁的足尺模型试验,以研究该类箱梁在正常使用阶段和施工状态下的结构行为。根据试验箱梁的尺寸参数以及实际约束条件确定了拼装与加载方案。本文重点研究正常使用荷载和梁上运梁两种工况下梁体应力状况与位移变化等结构静力性能,并与试验梁实体有限元模型进行对比分析。研究结果表明:在正常使用阶段,加、卸载后拼装梁体残余变形较小,基本处于弹性工作状态,整体性较好;键齿接缝两侧基本无相对滑移,接缝截面纵向应变沿梁高大致呈线性变化,力学行为基本符合平截面假定;体外预应力束在转向处基本无滑移,体内外预应力增量随跨中弯矩基本呈线性变化;在梁上运梁工况下,实测梁体下缘压应力储备充足,满足运梁安全性要求。

关键词: 节段预制拼装     模型试验     体外预应力     足尺试验    

预铸复合螺箍SRC柱之轴压行为研究

尹衍樑,翁正强,王瑞祯,梁景裕

《中国工程科学》 2006年 第8卷 第12期   页码 16-30

摘要:

开展了一系列大尺寸钢骨钢筋混凝土矩形柱的轴压试验,旨在探讨新型的复合螺旋箍筋或“尹氏螺箍”在矩形SRC柱之使用效益。由于“尹氏螺箍”采用自动化加工制造,可大幅降低箍筋绑扎之人力及缩短工期,极具经济效益,很适合用于预铸工法。依据力学原理探讨SRC柱箍筋用量的合理性,研究参数包括箍筋的型式、间距及钢骨之型式、SRC柱之轴压强度与韧性。由于SRC柱内部的钢骨亦能够围束混凝土,有助于降低SRC柱箍筋之需求量,达到更经济的设计结果;且螺旋箍筋对混凝土的围束效果比传统水平闭合箍筋更好,可提升柱之强度与抗震能力。试验结果显示,配置新型五螺箍之SRC柱可以发展出良好的强度与韧性,且具备良好的经济效益。研究并建立了一组适合这种新型SRC柱之围束箍筋设计方法,以提供学术界与工程界参考。

关键词: 预铸工法     钢骨钢筋混凝土(SRC)     矩形SRC柱     复合螺箍     五螺箍     轴压强度    

Effect of earth reinforcement, soil properties and wall properties on bridge MSE walls

《结构与土木工程前沿(英文)》 2021年 第15卷 第5期   页码 1209-1221 doi: 10.1007/s11709-021-0764-2

摘要: Mechanically stabilized earth (MSE) retaining walls are popular for highway bridge structures. They have precast concrete panels attached to earth reinforcement. The panels are designed to have some lateral movement. However, in some cases, excessive movement and even complete dislocation of the panels have been observed. In this study, 3-D numerical modeling involving an existing MSE wall was undertaken to investigate various wall parameters. The effects of pore pressure, soil cohesion, earth reinforcement type and length, breakage/slippage of reinforcement and concrete strength, were examined. Results showed that the wall movement is affected by soil pore pressure and reinforcement integrity and length, and unaffected by concrete strength. Soil cohesion has a minor effect, while the movement increased by 13–20 mm for flexible geogrid reinforced walls compared with the steel grid walls. The steel grid stresses were below yielding, while the geogrid experienced significant stresses without rupture. Geogrid reinforcement may be used taking account of slippage resistance and wall movement. If steel grid is used, non-cohesive soil is recommended to minimize corrosion. Proper soil drainage is important for control of pore pressure.

关键词: mechanically stabilized earth walls     precast concrete panels     backfill soil     finite element modeling     earth reinforcement    

Self-centring segmental retaining walls—A new construction system for retaining walls

《结构与土木工程前沿(英文)》 2021年 第15卷 第4期   页码 980-1000 doi: 10.1007/s11709-021-0737-5

摘要: This paper reports on an experimental study on a new self-centring retaining wall system. Four post-tensioned segmental retaining walls (PSRWs) were experimentally tested. Each of the walls was constructed using seven T-shaped concrete segments with a dry stack. The walls were tested under incrementally increasing cyclic lateral load. The effect of the wall height, levels of post-tensioning (PT) force, and bonded versus unbonded condition of PT reinforcement on the structural behavior of the PSRWs was investigated. The results showed that such PSRWs are structurally adequate for water retaining structures. According to the results, increasing the wall height decreases initial strength but increases the deformation capacity of the wall. The larger deformation capacity and ductility of PSRW make it a suitable structural system for fluctuating loads or deformation, e.g., seawall. It was also found that increasing the PT force increases the wall’s stiffness; however, reduces its ductility. The residual drift and the extent of damage of the unbonded PSRWs were significantly smaller than those of the bonded ones. Results suggest that this newly developed self-centring retaining wall can be a suitable structural system to retain lateral loads. Due to its unique deformation capacity and self-centring behavior, it can potentially be used for seawall application.

关键词: retaining wall     segmental     precast concrete     unbonded post-tensioning     water retaining wall     seawall    

Precast steel–UHPC lightweight composite bridge for accelerated bridge construction

Shuwen DENG, Xudong SHAO, Xudong ZHAO, Yang WANG, Yan WANG

《结构与土木工程前沿(英文)》 2021年 第15卷 第2期   页码 364-377 doi: 10.1007/s11709-021-0702-3

摘要: In this study, a fully precast steel–ultrahigh performance concrete (UHPC) lightweight composite bridge (LWCB) was proposed based on Mapu Bridge, aiming at accelerating construction in bridge engineering. Cast-in-place joints are generally the controlling factor of segmental structures. Therefore, an innovative girder-to-girder joint that is suitable for LWCB was developed. A specimen consisting of two prefabricated steel–UHPC composite girder parts and one post-cast joint part was fabricated to determine if the joint can effectively transfer load between girders. The flexural behavior of the specimen under a negative bending moment was explored. Finite element analyses of Mapu Bridge showed that the nominal stress of critical sections could meet the required stress, indicating that the design is reasonable. The fatigue performance of the UHPC deck was assessed based on past research, and results revealed that the fatigue performance could meet the design requirements. Based on the test results, a crack width prediction method for the joint interface, a simplified calculation method for the design moment, and a deflection calculation method for the steel–UHPC composite girder in consideration of the UHPC tensile stiffness effect were presented. Good agreements were achieved between the predicted values and test results.

关键词: accelerated bridge construction     ultrahigh-performance concrete     steel–UHPC composite bridge     UHPC girder-to-girder joint    

Dynamic response of precast segmental bridge columns under heavy truck impact

《结构与土木工程前沿(英文)》 2023年 第17卷 第3期   页码 327-349 doi: 10.1007/s11709-023-0911-z

摘要: Considering the wide application of precast segmental bridge columns (PSBCs) in engineering practice, impact-resistant performance has gained significant attention. However, few studies have focused on PSBCs subjected to high-energy impacts caused by heavy truck collisions. Therefore, the behavior of PSBCs under a heavy truck impact was investigated in this study using high-fidelity finite element (FE) models. The detailed FE modeling methods of the PSBCs and heavy trucks were validated against experimental tests. The validated modeling methods were employed to simulate collisions between PSBCs and heavy trucks. The simulation results demonstrated that the engine and cargo caused two major peak impact forces during collision. Subsequently, the impact force, failure mode, displacement, and internal force of the PSBCs under heavy truck impacts were scrutinized. An extensive study was performed to assess the influence of the section size, truck weight, impact velocity, and number of precast segments on the impact responses. The truck weight was found to have a minor effect on the engine impact force. Damage was found to be localized at the bottom of the three segments, with the top remaining primarily undamaged. This parametric study demonstrated that larger cross-sections may be a preferred option to protect PSBCs against the impact of heavy trucks.

关键词: precast segmental bridge columns     heavy truck     collision     dynamic response    

Simplified theoretical analysis and numerical study on the dynamic behavior of FCP under blast loads

Chunfeng ZHAO, Xin YE, Avinash GAUTAM, Xin LU, Y. L. MO

《结构与土木工程前沿(英文)》 2020年 第14卷 第4期   页码 983-997 doi: 10.1007/s11709-020-0633-4

摘要: Precast concrete structures have developed rapidly in the last decades due to the advantages of better quality, non-pollution and fast construction with respect to conventional cast-in-place structures. In the present study, a theoretical model and nonlinear 3D model are developed and established to assess the dynamic behavior of precast concrete slabs under blast load. At first, the 3D model is validated by an experiment performed by other researchers. The verified model is adopted to investigate the blast performance of fabricated concrete panels (FCPs) in terms of parameters of the explosive charge, panel thickness, and reinforcement ratio. Finally, a simplified theoretical model of the FCP under blast load is developed to predict the maximum deflection. It is indicated that the theoretical model can precisely predict the maximum displacement of FCP under blast loads. The results show that the failure modes of the panels varied from bending failure to shear failure with the mass of TNT increasing. The thickness of the panel, reinforcement ratio, and explosive charges have significant effects on the anti-blast capacity of the FCPs.

关键词: precast structure     fabricated concrete panel     blast resistance     theory model     empirical equation    

标题 作者 时间 类型 操作

Ductility improvement of GFRP-RC beams using precast confined concrete block in compression zone

期刊论文

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

期刊论文

Structural performance of a façade precast concrete sandwich panel enabled by a bar-type basalt fiber-reinforced

期刊论文

Seismic response of precast reinforced concrete wall subjected to cyclic in-plane and constant out-of-plane

期刊论文

Construction Technology of Off-Site Precast Concrete Buildings

Ting Gong,Jian Yang,Hao Hu,Feng Xu

期刊论文

Factors affecting the seismic behavior of segmental precast bridge columns

Haitham DAWOOD,Mohamed ELGAWADY,Joshua HEWES

期刊论文

Seismic performance of precast hollow bridge piers with different construction details

Zhiqiang WANG,Jiping GE,Hongyi WEI

期刊论文

高强钢筋混凝土预制弧板井壁力学特性分析

荣传新,王秀喜,程桦

期刊论文

体内-体外混合配束节段预制拼装箱梁足尺模型试验研究

郑开启,卜红旗,刘钊,惠卓,吕志涛

期刊论文

预铸复合螺箍SRC柱之轴压行为研究

尹衍樑,翁正强,王瑞祯,梁景裕

期刊论文

Effect of earth reinforcement, soil properties and wall properties on bridge MSE walls

期刊论文

Self-centring segmental retaining walls—A new construction system for retaining walls

期刊论文

Precast steel–UHPC lightweight composite bridge for accelerated bridge construction

Shuwen DENG, Xudong SHAO, Xudong ZHAO, Yang WANG, Yan WANG

期刊论文

Dynamic response of precast segmental bridge columns under heavy truck impact

期刊论文

Simplified theoretical analysis and numerical study on the dynamic behavior of FCP under blast loads

Chunfeng ZHAO, Xin YE, Avinash GAUTAM, Xin LU, Y. L. MO

期刊论文