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Experimental and parametrical investigation of pre-stressed ultrahigh-performance fiber-reinforced concrete railway sleepers

《结构与土木工程前沿(英文)》 2023年 第17卷 第3期   页码 411-428 doi: 10.1007/s11709-023-0928-3

摘要: In this study, ultrahigh-performance fiber-reinforced concrete (UHPFRC) used in a type B70 concrete sleeper is investigated experimentally and parametrically. The main parameters investigated are the steel fiber volume fractions (0%, 0.5%, 1%, and 1.5%). Under European standards, 35 UHPFRC sleepers are subjected to static bending tests at the center and rail seat sections, and the screw on the fastening system is pulled out. The first cracking load, failure load, failure mode, crack propagation, load–deflection curve, load–crack width, and failure load from these tests are measured and compared with those of a control sleeper manufactured using normal concrete C50. The accuracy of the parametric study is verified experimentally. Subsequently, the results of the study are applied to UHPFRC sleepers with different concrete volumes to investigate the effects of the properties of UHPFRC on their performance. Experimental and parametric study results show that the behavior of UHPFRC sleepers improves significantly when the amount of steel fiber in the mix is increased. Sleepers manufactured using UHPFRC with a steel fiber volume fraction of 1% and a concrete volume less than 25% that of standard sleeper B70 can be used under the same loads and requirements, which contributes positively to the cost and surrounding environment.

关键词: pre-stressed concrete sleeper     ultrahigh performance fiber-reinforced concrete     pull-out test     static bending test     steel fiber     aspect ratio     volume fraction    

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

《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    

Model test of the group piles foundation of a high-speed railway bridge in mined-out area

Xin LIANG,Qian-gong CHENG,Jiu-jiang WU,Jian-ming CHEN

《结构与土木工程前沿(英文)》 2016年 第10卷 第4期   页码 488-498 doi: 10.1007/s11709-016-0338-x

摘要: The research on the mechanism of pile-soil-cap-goaf interaction and settlement of high-speed railway bridge located in mined-out area is still relatively rare. By taking the pile group of Guanshandi bridge foundation in Hefei-Fuzhou high-speed railway as the prototype, a model test is carried out. According to the similarity theory, the similar constant is derived and the similar model material is determined. Meanwhile, three types of data including the bearing behavior of piles, and the settlement law, and soil among piles are investigated. It can be found that: the influence of goaf on the bearing capacity of pile is inversely to the loading degree, the larger of loading degree, the smaller impact of goaf on the bearing capacity. There is no negative side friction can been found in pile body and the degree of downward tendency for the barycenter of side friction layout is obvious for piles in goaf. Although the bearing ratio of soil resistance under cap is relatively large, the cap effect is suggested be ignored considering the characteristic of goaf. There is a maximum critical value for the uneven settlement of pile group in goaf, and when the value is reached, the uneven settlement stop growing anymore. In addition, the formula for calculating bearing capacity and settlement of pile group in goaf based on test results, theory analysis and related standard is established.

关键词: high-speed railway     mined-out areas     goaf     group piles foundation     physical model test     bearing capacity     settlement    

A review of salting-out effect and sugaring-out effect: driving forces for novel liquid-liquid extraction

Chuhan Fu, Zhuoxi Li, Zengran Sun, Shaoqu Xie

《化学科学与工程前沿(英文)》 2021年 第15卷 第4期   页码 854-871 doi: 10.1007/s11705-020-1980-3

摘要: Biofuels and bio-based chemicals are getting more and more attention because of their sustainable and renewable properties and wide industrial applications. However, the low concentrations of the targeted products in their fermentation broths, the complicated components of the broths and the high energy-intensive separation and purification process hinder the competitiveness of biofuels and biochemicals with the petro-based ones. Hence, the production and the separation of biofuels and bio-based chemicals in energy-saving, low-cost and greenness ways become hot topics nowadays. This review introduces the separation technologies (salting-out extraction, salting-out, sugaring-out extraction, and sugaring-out) that extract biobutanol, 1,3-propanediol, 2,3-butanediol, acetoin, organic acids and other bio-based chemicals from fermentation broths/aqueous solutions. Salting-out/sugaring-out extraction and salting-out/sugaring-out technologies display the high separating efficiency and the high targeted product yields. In addition, they are easy to operate and require low cost for separating products. Hence, they are the effective and potential technologies for separating targeted products in the wide industrial applications. The successful research into the salting-out/sugaring-out and salting-out/sugaring-out extraction not only affords biofuels and biochemical but also opens a door for the development of novel separation methods.

关键词: salting-out     sugaring-out     extraction     biofuels     biochemicals     application    

Experimental study on behavior of mortar-aggregate interface after elevated temperatures

Wan WANG, Jianzhuang XIAO, Shiying XU, Chunhui WANG

《结构与土木工程前沿(英文)》 2017年 第11卷 第2期   页码 158-168 doi: 10.1007/s11709-016-0374-6

摘要: A push-out test program was designed and conducted to study the meso-scale behavior of mortar-aggregate interface for concrete after elevated temperatures ranging from 20°C to 600°C with the concept of modeled concrete (MC) and modeled recycled aggregate concrete (MRAC). The MCs and MRACs were designed with different strength grade of mortar and were exposed to different elevated temperatures. Following that the specimens were cooled to room temperature and push-out tests were conducted. Failure process and mechanical behaviors were analyzed based on failure modes, residual load-displacement curves, residual peak loads and peak displacements. It is found that failure modes significantly depended on specimen type, the elevated temperature and the strength grade of mortar. For MC, major cracks started to propagate along the initial cracks caused by elevated temperatures at about 80% of residual peak load. For MRAC, the cracks appeared at a lower level of load with the increasing elevated temperatures. The cracks connected with each other, formed a failure face and the specimens were split into several parts suddenly when reaching the residual peak load. Residual load-displacement curves of different specimens had similarities in shape. Besides, effect of temperatures and strength grade of mortar on residual peak load and peak displacement were analyzed. For MC and MRAC with higher strength of new hardened mortar, the residual peak load kept constant when the temperature is lower than 400°C and dropped by 43.5% on average at 600°C. For MRAC with lower strength of new hardened mortar, the residual peak load began to reduce when the temperatures exceeded 200°C and reduced by 27.4% and 60.8% respectively at 400°C and 600°C. The properties of recycled aggregate concrete (RAC) may be more sensitive to elevated temperatures than those of natural aggregate concrete (NAC) due to the fact that the interfacial properties of RAC are lower than those of NAC, and are deteriorated at lower temperatures.

关键词: mortar-aggregate interface     push-out test     elevated temperatures     modeled concrete (MC)     modeled recycled aggregate concrete (MRAC)    

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

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    

Zooming in and out of ferroptosis in human disease

《医学前沿(英文)》 2023年 第17卷 第2期   页码 173-206 doi: 10.1007/s11684-023-0992-z

摘要: Ferroptosis is defined as an iron-dependent regulated form of cell death driven by lipid peroxidation. In the past decade, it has been implicated in the pathogenesis of various diseases that together involve almost every organ of the body, including various cancers, neurodegenerative diseases, cardiovascular diseases, lung diseases, liver diseases, kidney diseases, endocrine metabolic diseases, iron-overload-related diseases, orthopedic diseases and autoimmune diseases. Understanding the underlying molecular mechanisms of ferroptosis and its regulatory pathways could provide additional strategies for the management of these disease conditions. Indeed, there are an expanding number of studies suggesting that ferroptosis serves as a bona-fide target for the prevention and treatment of these diseases in relevant pre-clinical models. In this review, we summarize the progress in the research into ferroptosis and its regulatory mechanisms in human disease, while providing evidence in support of ferroptosis as a target for the treatment of these diseases. We also discuss our perspectives on the future directions in the targeting of ferroptosis in human disease.

关键词: ferroptosis     human disease     iron metabolism     lipid peroxidation     antioxidation    

Mechatronic design of a novel linear compliant positioning stage with large travel range and high out-of-plane

Hua LIU, Xin XIE, Ruoyu TAN, Lianchao ZHANG, Dapeng FAN

《机械工程前沿(英文)》 2017年 第12卷 第2期   页码 265-278 doi: 10.1007/s11465-017-0453-y

摘要:

Most of the XY positioning stages proposed in previous studies are mainly designed by considering only a single performance indicator of the stage. As a result, the other performance indicators are relatively weak. In this study, a 2-degree-of-freedom linear compliant positioning stage (LCPS) is developed by mechatronic design to balance the interacting performance indicators and realize the desired positioning stage. The key parameters and the coupling of the structure and actuators are completely considered in the design. The LCPS consists of four voice coil motors (VCMs), which are conformally designed for compactness, and six spatial leaf spring parallelograms. These parallelograms are serially connected for a large travel range and a high out-of-plane payload capacity. The mechatronic model is established by matrix structural analysis for structural modeling and by Kirchhoff’s law for the VCMs. The sensitivities of the key parameters are analyzed, and the design parameters are subsequently determined. The analytical model of the stage is confirmed by experiments. The stage has a travel range of 4.4 mm× 7.0 mm and a 0.16% area ratio of workspace to the outer dimension of the stage. The values of these performance indicators are greater than those of any existing stage reported in the literature. The closed-loop bandwidth is 9.5 Hz in both working directions. The stage can track a circular trajectory with a radius of 1.5 mm, with 40 mm error and a resolution of lower than 3 mm. The results of payload tests indicate that the stage has at least 20 kg out-of-plane payload capacity.

关键词: mechatronic design     linear compliant positioning stage     large travel range     high out-of-plane payload capacity     spatial parallelogram     voice coil motor     sensitivity analysis    

The German Energiewende and its roll-out of renewable energies: An economic perspective

Sebastian KREUZ, Felix MÜSGENS

《能源前沿(英文)》 2017年 第11卷 第2期   页码 126-134 doi: 10.1007/s11708-017-0467-5

摘要: This paper gives a short overview of the German Energiewende, i.e. the transition of a large and mostly thermal electricity system towards electricity generation from renewable energy source. It discusses both, the motivation of the transitions as future goals and current status. Furthermore, it gives an in-depth view into the changes in economic costs for society as well as electricity price effects, especially for average private households and industrial consumers. It also discusses the benefits of the promotion of renewable energies in Germany.

关键词: electricity system     renewable energy     cost-benefit analysis    

Washing out heavy metals from contaminated soils from an iron and steel smelting site

Guangxu ZHU,Qingjun GUO,Junxing YANG,Hanzhi ZHANG,Rongfei WEI,Chunyu WANG,Marc PETERS,Xiaoyong ZHOU,Jun YANG

《环境科学与工程前沿(英文)》 2015年 第9卷 第4期   页码 634-641 doi: 10.1007/s11783-014-0713-6

摘要: Washing is a promising method for separating contaminants bound to the particles of soil by chemical mobilization. Laboratory batch washing experiments were conducted using deionized water and varying concentrations of oxalic acid, citric acid, tartaric acid, acetic acid, hydrochloric acid and ethylenediaminetetra acetic acid (EDTA) to assess the efficiency of using these chemicals as washing agents and to clean up heavy metals from two heavily polluted soils from an iron and streel smelting site. The toxicity reduction index and remediation costs were analyzed, and the results showed that the soils were polluted with Cd, Pb and Zn. Hydrochloric acid and EDTA were more efficient than the other washing agents in the remediation of the test soils. The maximum total toxicity reduction index showed that 0.5 mol·L hydrochloric acid could achieve the remediation with the lowest costs.

关键词: heavy metals     soil washing     toxicity reduction index     iron and steel smelting site    

Out-of-plane elastic buckling load and strength design of space truss arch with a rectangular section

Senping WANG; Xiaolong LIU; Bo YUAN; Minjie SHI; Yanhui WEI

《结构与土木工程前沿(英文)》 2022年 第16卷 第9期   页码 1141-1152 doi: 10.1007/s11709-022-0866-5

摘要: The out-of-plane stability of the two-hinged space truss circular arch with a rectangular section is theoretically and numerically investigated in this paper. Firstly, the flexural stiffness and torsional stiffness of space truss arches are deduced. The calculation formula of out-of-plane elastic buckling loads of the space truss arch is derived based on the classical solution of out-of-plane flexural-torsional buckling loads of the solid web arch. However, since the classical solution cannot be used for the calculation of the arch with a small rise-span ratio, the formula for out-of-plane elastic buckling loads of space truss arches subjected to end bending moments is modified. Numerical research of the out-of-plane stability of space truss arches under different load cases shows that the theoretical formula proposed in this paper has good accuracy. Secondly, the design formulas to predict the out-of-plane elastoplastic stability strength of space truss arches subjected to the end bending moment and radial uniform load are presented through introducing a normalized slenderness ratio. By assuming that all components of space truss circular arches bear only axial force, the design formulas to prevent the local buckling of chord and transverse tubes are deduced. Finally, the bearing capacity design equations of space truss arches are proposed under vertical uniform load.

关键词: torsional stiffness     strength design     elastic buckling     space truss arches     out-of-plane    

利用基因工程技术大规模消灭害虫

Chris Palmer

《工程(英文)》 2022年 第18卷 第11期   页码 6-8 doi: 10.1016/j.eng.2022.09.004

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

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    

Porous silica synthesis out of coal fly ash with no residue generation and complete silicon separation

《环境科学与工程前沿(英文)》 2023年 第17卷 第9期 doi: 10.1007/s11783-023-1712-2

摘要:

● Both amorphous and crystalline silicon are completely separated from coal fly ash.

关键词: Coal fly ash     Alkali fusion     Micro-/meso-porous Si     Zeolite MCM-48     Crystalline transformation    

标题 作者 时间 类型 操作

Experimental and parametrical investigation of pre-stressed ultrahigh-performance fiber-reinforced concrete railway sleepers

期刊论文

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

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

Model test of the group piles foundation of a high-speed railway bridge in mined-out area

Xin LIANG,Qian-gong CHENG,Jiu-jiang WU,Jian-ming CHEN

期刊论文

A review of salting-out effect and sugaring-out effect: driving forces for novel liquid-liquid extraction

Chuhan Fu, Zhuoxi Li, Zengran Sun, Shaoqu Xie

期刊论文

Experimental study on behavior of mortar-aggregate interface after elevated temperatures

Wan WANG, Jianzhuang XIAO, Shiying XU, Chunhui WANG

期刊论文

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

Jianan QI, Yuqing HU, Jingquan WANG, Wenchao LI

期刊论文

Zooming in and out of ferroptosis in human disease

期刊论文

Mechatronic design of a novel linear compliant positioning stage with large travel range and high out-of-plane

Hua LIU, Xin XIE, Ruoyu TAN, Lianchao ZHANG, Dapeng FAN

期刊论文

The German Energiewende and its roll-out of renewable energies: An economic perspective

Sebastian KREUZ, Felix MÜSGENS

期刊论文

Washing out heavy metals from contaminated soils from an iron and steel smelting site

Guangxu ZHU,Qingjun GUO,Junxing YANG,Hanzhi ZHANG,Rongfei WEI,Chunyu WANG,Marc PETERS,Xiaoyong ZHOU,Jun YANG

期刊论文

Out-of-plane elastic buckling load and strength design of space truss arch with a rectangular section

Senping WANG; Xiaolong LIU; Bo YUAN; Minjie SHI; Yanhui WEI

期刊论文

利用基因工程技术大规模消灭害虫

Chris Palmer

期刊论文

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

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

期刊论文

Porous silica synthesis out of coal fly ash with no residue generation and complete silicon separation

期刊论文