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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    

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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    

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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    

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Pragmatic multi-stage simulated annealing for optimal placement of synchrophasor measurement units in

Pathirikkat GOPAKUMAR,M. JAYA BHARATA REDDY,Dusmata Kumar MOHANTA

《能源前沿（英文）》 2015年 第9卷 第2期   页码 148-161 doi: 10.1007/s11708-015-0344-z

摘要： Conventional power grids across the globe are reforming to smart power grids with cutting edge technologies in real time monitoring and control methods. Advanced real time monitoring is facilitated by incorporating synchrophasor measurement units such as phasor measurement units (PMUs) to the power grid monitoring system. Several physical and economic constraints limit the deployment of PMUs in smart power grids. This paper proposes a pragmatic multi-stage simulated annealing (PMSSA) methodology for finding the optimal locations in the smart power grid for installing PMUs in conjunction with existing conventional measurement units (CMUs) to achieve a complete observability of the grid. The proposed PMSSA is much faster than the conventional simulated annealing (SA) approach as it utilizes controlled uphill and downhill movements during various stages of optimization. Moreover, the method of integrating practical phasor measurement unit (PMU) placement conditions like PMU channel limits and redundant placement can be easily handled. The efficacy of the proposed methodology has been validated through simulation studies in IEEE standard bus systems and practical regional Indian power grids.

关键词： phasor measurement units (PMUs)     pragmatic PMU placement     simulated annealing (SA)     western region Indian power grid (WRIPG)    

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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    

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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    

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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    

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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    

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Distribution and potential ecological risk of heavy metals in the typical eco-units of Haihe River Basin

Jingling LIU,Tao YANG,Qiuying CHEN,Feng LIU,Binbin WANG

《环境科学与工程前沿（英文）》 2016年 第10卷 第1期   页码 103-113 doi: 10.1007/s11783-014-0686-5

摘要： The distribution and characteristics of seven heavy metals in sediments located in the typical ecological units (eco-units) (e.g., rivers, lakes, and estuaries) of Haihe River Basin were analyzed. The Hakanson potential ecological risk index was used for ecological risk assessment. The results indicated that the concentration scales of As, Hg, Cr, Cd, Pb, Cu, and Zn in the eco-units were 2.08 to 24.80 mg·g , 0.01 to 1135.50 mg·g , 28.70 to 152.73 mg·g , 0.03 to 195765.83 mg·g , 8.65 to 157.82 mg·g , 6.47 to 178.61 mg·g , and 21.09 to 1076.25 mg·g , respectively. The maximum concentrations of Hg, Cd, and Zn showed higher levels than other water bodies around the world. Hg and Cd have high concentrations in Zhangweinanhe River (1135.50 and 195765.83 mg·g , respectively) and Haihe Estuary (790.50 and 548.47 mg·g , respectively). According to the ecological factor, Cd and Hg showed very strong ecological risks. The seven heavy metals, namely, Cd, Hg, As, Cr, Pb, Cu, and Zn, exhibited ecological risk levels in descending order. Based on the potential ecological risk index, Luanhe River and Baiyangdian Lake had moderate ecological risks, whereas every site in Zhangweinanhe River and Haihe Estuary had substantial risk levels. The risk order of the typical eco-units are as follows: Zhangweinan River (2278345.68)>Estuary (161914.74)>Luanhe River (191.54)>Baiyangdian Lake (120.95). These results provided a scientific basis for water environment improvement and risk management of the Haihe River Basin.

关键词： Haihe River Basin     ecological risk     eco-units     heavy metals    

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Reliability prediction and its validation for nuclear power units in service

Jinyuan SHI,Yong WANG

《能源前沿（英文）》 2016年 第10卷 第4期   页码 479-488 doi: 10.1007/s11708-016-0425-7

摘要： In this paper a novel method for reliability prediction and validation of nuclear power units in service is proposed. The equivalent availability factor is used to measure the reliability, and the equivalent availability factor deducting planed outage hours from period hours and maintenance factor are used for the measurement of inherent reliability. By statistical analysis of historical reliability data, the statistical maintenance factor and the undetermined parameter in its numerical model can be determined. The numerical model based on the maintenance factor predicts the equivalent availability factor deducting planed outage hours from period hours, and the planed outage factor can be obtained by using the planned maintenance days. Using these factors, the equivalent availability factor of nuclear power units in the following 3 years can be obtained. Besides, the equivalent availability factor can be predicted by using the historical statistics of planed outage factor and the predicted equivalent availability factor deducting planed outage hours from period hours. The accuracy of the reliability prediction can be evaluated according to the comparison between the predicted and statistical equivalent availability factors. Furthermore, the reliability prediction method is validated using the nuclear power units in North American Electric Reliability Council (NERC) and China. It is found that the relative errors of the predicted equivalent availability factors for nuclear power units of NERC and China are in the range of –2.16% to 5.23% and –2.15% to 3.71%, respectively. The method proposed can effectively predict the reliability index in the following 3 years, thus providing effective reliability management and maintenance optimization methods for nuclear power units.

关键词： nuclear power units in service     reliability     reliability prediction     equivalent availability factors    

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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)    

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Capacity limitation of nuclear units in grid based on analysis of frequency regulation

Yiping DAI, Pan JIANG, Lin GAO, Weimin KAN, Xiaoqing XIAO, Ge JIN

《能源前沿（英文）》 2012年 第6卷 第2期   页码 148-154 doi: 10.1007/s11708-012-0174-1

摘要： The increasing capacity of nuclear units in power grid poses threat to system stability and security. Load disturbance may cause overspeed of the units and trigger the overspeed protection controller (OPC). Repeating actions of valves have a strong impact on the security of the equipment and may result in a collapse of the power system. Based on the analysis of frequency regulation, mathematic models for nuclear units in the grid are established in this paper to simulate the dynamic process when load disturbance occurs. The critical action of the OPC is proposed as the constraint of safe operation for the units. The relationship between different styles of frequency regulation and the allowable capacity of the nuclear units in the grid is discussed. This research can help to estimate the capacity limitation of nuclear units in the grid.

关键词： nuclear units capacity     overspeed     primary frequency control (PFC)     second frequency control (SFC)    

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Optimal operation of energy at hydrothermal power plants by simultaneous minimization of pollution and costs using improved ABC algorithm

Homayoun EBRAHIMIAN,Bahman TAHERI,Nasser YOUSEFI

《能源前沿（英文）》 2015年 第9卷 第4期   页码 426-432 doi: 10.1007/s11708-015-0376-4

摘要： The aim of this paper is simultaneous minimization of hydrothermal units to reach the best solution by employing an improved artificial bee colony (ABC) algorithm in a multi-objective function consisting of economic dispatch (ED) considering the valve-point effect and pollution function in power systems in view of the hot water of the hydro system. In this type of optimization problem, all practical constraints of units were taken into account as much as possible in order to comply with the reality. These constraints include the maximum and minimum output power of units, the constraints caused by the balance between supply and demand, the impact of pollution, water balance, uneven production curve considering the valve-point effect and system losses. The proposed algorithm is applied on the studied system, and the obtained results indifferent operating conditions are analyzed. To investigate in various operating conditions, different load profiles in 12 h are taken into account. The obtained results are compared with those of the other methods including the genetic algorithm (GA), the Basu technique, and the improved genetic algorithm. Fast convergence is one of this improved algorithm features.

关键词： practical constraints of units     pollution function     inlet steam valve     up-ramp rate of units     improved ABC algorithm    

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Energy conservation in China’s coal-fired power industry by installing advanced units and organized phasing

Weiliang WANG, Junfu LYU, Zheng LI, Hai ZHANG, Guangxi YUE, Weidou NI

《能源前沿（英文）》 2019年 第13卷 第4期   页码 798-807 doi: 10.1007/s11708-019-0633-z

摘要： Coal-fired power is the main power source and the biggest contributor to energy conservation in the past several decades in China. It is generally believed that advanced technology should be counted on for energy conservation. However, a review of the decline in the national average net coal consumption rate (NCCR) of China’s coal-fired power industry along with its development over the past few decades indicates that the up-gradation of the national unit capacity structure (including installing advanced production and phasing out backward production) plays a more important role. A quantitative study on the effect of the unit capacity structure up-gradation on the decline in the national average NCCR suggests that phasing out backward production is the leading factor for the decline in the NCCR in the past decade, followed by the new installation, whose sum contributes to approximately 80% of the decline in the national average NCCR. The new installation has an effective affecting period of about 8 years, during which it would gradually decline from a relatively high value. Since the effect of phasing out backward production may remain at a certain degree given a continual action of phasing out backward capacity, it is suggested that the organized action of phasing out backward production should be insisted on.

关键词： coal-fired power     energy conservation     net coal consumption rate     new installation     phasing out backward production     unit capacity structure    

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Occurrence and migration of microplastics and plasticizers in different wastewater and sludge treatment units

《环境科学与工程前沿（英文）》 2022年 第16卷 第11期 doi: 10.1007/s11783-022-1577-9

摘要：

● Reduce the quantifying MPs time by using Nile red staining.

关键词： Microplastics     Municipal wastewater treatment plant     Phthalate esters     Thermal hydrolysis    

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标题 作者 时间 类型 操作

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

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

期刊论文

Pragmatic multi-stage simulated annealing for optimal placement of synchrophasor measurement units in

Pathirikkat GOPAKUMAR,M. JAYA BHARATA REDDY,Dusmata Kumar MOHANTA

期刊论文

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

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

Dynamic response of precast segmental bridge columns under heavy truck impact

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

Distribution and potential ecological risk of heavy metals in the typical eco-units of Haihe River Basin

Jingling LIU,Tao YANG,Qiuying CHEN,Feng LIU,Binbin WANG

期刊论文

Reliability prediction and its validation for nuclear power units in service

Jinyuan SHI,Yong WANG

期刊论文

Construction Technology of Off-Site Precast Concrete Buildings

Ting Gong,Jian Yang,Hao Hu,Feng Xu

期刊论文

Capacity limitation of nuclear units in grid based on analysis of frequency regulation

Yiping DAI, Pan JIANG, Lin GAO, Weimin KAN, Xiaoqing XIAO, Ge JIN

期刊论文

Optimal operation of energy at hydrothermal power plants by simultaneous minimization of pollution and costs using improved ABC algorithm

Homayoun EBRAHIMIAN,Bahman TAHERI,Nasser YOUSEFI

期刊论文

Energy conservation in China’s coal-fired power industry by installing advanced units and organized phasing

Weiliang WANG, Junfu LYU, Zheng LI, Hai ZHANG, Guangxi YUE, Weidou NI

期刊论文

Occurrence and migration of microplastics and plasticizers in different wastewater and sludge treatment units

期刊论文