PEC剪力墙抗侧性能试验研究

随着装配式结构在我国的应用与推广,PEC构件由于其便于批量化生产、快速装配的特点,在工程中的应用价值得以大大提高。部分企业开始尝试在实际工程中应用PEC构件,提出了一种新型剪力墙构件——PEC剪力墙。以实际工程应用为出发点对3个足尺PEC剪力墙试件进行低周拟静力水平加载试验,观察了PEC剪力墙的试验现象、破坏过程,通过分析关键部位应力、应变情况,考察了在往复荷载作用下的破坏模式、变形特征;分析了PEC剪力墙在低周往复荷载作用下的滞回曲线、骨架曲线、耗能能力、延性、承载力以及刚度等力学性能,对其抗侧性能进行了评价;对比了卷边构造措施对其破坏特征、变形以及抗侧性能的影响,并检验其有效性;对比分析了不同轴压比对卷边构造PEC剪力墙抗侧性能的影响。试验结果表明:1)PEC剪力墙试件均为弯曲屈服后破坏,在达到最大承载力前钢翼缘均已经屈服;试件SW1底部混凝土压溃破坏,外侧钢翼缘出现局部屈曲,试件SW2与SW3底部钢翼缘未发生屈曲,最终发生底座锚固破坏。2)试件SW1的滞回曲线比较饱满,有较强的塑性耗能能力,试件SW2和试件SW3滞回曲线有一定程度的捏缩现象,试件的延性系数均大于3.4,有较好的变形能力,承载力退化程度很低,刚度后期退化变缓,在1/30层间位移角内具有稳定良好的承载能力。3)卷边构造的设置加强了对PEC剪力墙底部混凝土的约束,延后了底部混凝土的压溃破坏,使PEC剪力墙具有更好的承载性能。4)高轴压比下,试件会较早出现受压屈服,PEC剪力墙的初始刚度会有一定的提高,但其延性与耗能能力会下降。5)相比于混凝土剪力墙,PEC剪力墙的变形能力更接近钢板剪力墙,PEC剪力墙抗震设计的控制变形限值可适当放宽。

配置可更换角钢连接构造的钢框架试验研究

提出了一种适用于抗弯钢框架的可更换组合梁连接构造,钢梁翼缘处由可更换角钢连接,并进行了一系列试验研究。在预期地震作用下,损伤集中于角钢,方便震后更换。同时,考虑到震后建筑功能的快速恢复,使钢梁上方混凝土楼板内发生的裂缝宽度在可接受的微小程度范围内。试验研究分为三个阶段:纯钢梁连接构造的梁柱子结构试验,组合梁连接构造的梁柱子结构试验,以及配置可更换组合梁连接构造的钢框架动力试验。首先简要回顾前两阶段的研究成果,随后报告了第三阶段的研究工作,即配置可更换连接构造的缩尺钢框架的振动台试验。结果表明:形状与尺寸设计中考虑了塑性变形需求与防止净截面断裂破坏风险后,角钢可以有效吸收地震输入的能量,避免其他构件先行损伤;合理设计的连接构造可以避免混凝土严重开裂或者压溃;当主要构件保持弹性或轻微塑性时,快速更换角钢是可行的;更换角钢后,结构的刚度和承载力可以恢复到初始状态。

Preparation and application of a phosphorous free and non- nitrogen scale inhibitor in industrial cooling water systems

A novel environmentally friendly type of calcium carbonate, zinc （Ⅱ） and iron （Ⅲ） scale inhibitor Acrylic acidallylpolyethoxy carboxylate copolymer （AA- APEL） was synthesized. The anti-scale property of the AA-APEL toward CaCO3, zinc （Ⅱ） and iron （Ⅲ） in the artificial cooling water was studied through static scale inhibition tests. The observation shows that both calcium carbonate, zinc （Ⅱ） and iron （Ⅲ） inhibition increase with increasing the dosage of AA-APEL. The effect on formation of CaCO3 was investigated with combination of scanning electronic microscopy （SEM）, transmission electron microscopy （TEM）, X-ray powder diffraction （XRD） analysis and fourier transform infrared spectrometer, respectively. The results showed that the AA-APEL copolymer not only influenced calcium carbonate crystal morphology and crystal size but also the crystallinity. The crystallization of CaCO3 in the absence of inhibitor was rhombohedral calcite crystal, whereas a mixture of calcite with vaterite crystals was found in the presence of the AA- APEL copolymer. Inhibition mechanism is proposed that the interactions between calcium or iron ions and polyethylene glycol （PEG） are the fundamental impetus to restrain the formation of the scale in cooling water systems.

Cyanation and cyanomethylation of trimethylammonium salts via electrochemical cleavage of C–N bonds

We have developed a practical and mild electrochemical protocol for cyanation and cyanomethylation of trimethylammonium salts through a pathway involving C–N bond cleavage without the need for an exter-nal stoichiometric reducing agent or a sacrificial anode.The reaction employs tosyl cyanide(TsCN)or azido allyl alcohol as the cyanation or cyanomethylation reagent,respectively.It shows high functional group compatibility and can be applied for the cyanation of natural product derivatives.Preliminary mechanistic studies indicate the involvement of a radical addition pathway.

Thermal Management of Electrified Propulsion System for Low-Carbon Vehicles

An overview of current thermal challenges in transport electrification is introduced in order to underpin the research developments and trends of recent thermal management techniques.Currently,explorations of intelligent thermal management and control strategies prevail among car manufacturers in the context of climate change and global warming impacts.Therefore,major cutting-edge systematic approaches in electrified powertrain are summarized in the first place.In particular,the important role of heating,ventilation and air-condition system(HVAC)is emphasised.The trends in developing efficient HVAC system for future electrified powertrain are analysed.Then electric machine efficiency is under spotlight which could be improved by introducing new thermal management techniques and strengthening the efforts of driveline integrations.The demanded integration efforts are expected to provide better value per volume,or more power output/torque per unit with smaller form factor.Driven by demands,major thermal issues of high-power density machines are raised including the comprehensive understanding of thermal path,and multiphysics challenges are addressed whilst embedding power electronic semiconductors,non-isotropic electromagnetic materials and thermal insulation materials.Last but not least,the present review has listed several typical cooling techniques such as liquid cooling jacket,impingement/spray cooling and immersion cooling that could be applied to facilitate the development of integrated electric machine,and a mechanic-electric-thermal holistic approach is suggested at early design phase.Conclusively,a brief summary of the emerging new cooling techniques is presented and the keys to a successful integration are concluded.

Cyclic stress-strain behavior of structural steel with yield- strength up to 460 N/mm^2

This paper presents a constitutive model based on Ramberg-Osgood equation to describe the hysteresis material behavior of structural carbon steel with nominal yield strength between 235 to 420 N/mm^2. The proposed model was calibrated against a series of cyclic material tests with strain amplitude varying from 0.5% to 2.0%. A simple relationship between the modular parameter K and the yield strengthfy was proposed. The calibrated Ramberg-Osgood model revealed excellent agreement with the experimental results and captured further the experimental behavior of test specimens with nominal yield strength of 460 N/mm^2. The proposed constitutive model was also adopted in conjunction with the combined kinematic/isotropic materials description in ABAQUS to mimic a full scale experimental test under cyclic loading. The numerical results revealed close agreement with the experimental observations.

Dynamic material performance of cold-formed steel hollow sections： a state-of-the-art review

This paper presents a literature review focused on the material performance of cold-formed, carbon steel, hollow structural sections under impulsive （highly dynamic） loading. Impulsive loading, represented by impact and blast, is characterized by a very rapid, time-dependent loading regime in the affected members and materials. Thus, the effect of high-strain-rate loading is initially reviewed. Next the material toughness, an important energy-absorption property and one measure of a material＇s ability to arrest fracture, is considered by means of studying the Charpy V-notch behavior. The response of hollow sections under axial and lateral impact loading is then reviewed. Studies of blast on hollow sections, most of which fall under the categories of contact/near-field loading or far-field loading are presented. Under large-scale field blast experiments, cold-formed hollow sections have shown excellent behavior. Software for modeling blast loading and structural response, the latter including single degree of freedom analysis and explicit finite element analysis, is described and discussed.

Initial stiffness and moment resistance of reinforced joint with end-plate connection

In beam-to-column joint with bolted end-plate connection,the structural details of column flange reinforced by backing plate and column web panel reinforced by supplementary plate are analyzed.The joint is divided into some basic components,and the initial stiffness of each component is obtained.Especially,the initial stiffness of reinforced components is drawn by theoretical model and finite element analysis.The initial stiffness of reinforced joint can be obtained by assembling the initial stiffness of each component.The design moment resistance of column flange reinforced by backing plate is deduced based on yield line method,and the design moment resistances of other components are deduced based on present codes.The design moment resistance of the reinforced joint is then determined by the minimum of the design moment resistances of all components.By comparison with the results of finite element calculation,it is verified that the method to calculate the initial stiffness of reinforced joint is accurate enough to be used to estimate the rigid behavior of the joint and to make parametric study.

Seismic performance of prestressed concrete stand structure supporting retractable steel roof

The seismic behavior of a structural system composed of pre-stressed concrete stand supporting a retractable steel roof was studied,which is typically based on the prototype of engineering project of Shanghai Qizhong Tennis Center.By elasto-plastic finite element analysis and shaking table test,the following were investigated:the effects of roof configurations in opening and closing,the effect of pre-stress on the structural seismic response,and the failure mechanism of the spatial stand frame systems featured with circularly arranged columns and inverse-cone type stands.It was found thatthe roof status has great effect on the natural period,vibration modes,and seismic response of the whole structure,the stand response to horizontal seismic excitation is stronger in roof opening configuration than in closing state,and the response mode is dominantly translational rather than rotational,though the stand is characterized by its fundamentally torsional vibration mode.The study indicated that the pre-stressed inversecone stands can keep the system from global side-sway collapse under gravity loads,even in the case that most columns loose moment capacity.

A Study of the Truncated Square Pyramid Geometry for Enhancement of Super-hydrophobicity

Super-hydrophobic surfaces are quite common in nature,inspiring people to continually explore its water-repellence property and applications to our lives.It has been generally agreed that the property of super-hydrophobicity is mainly contributed by the microscale or nanoscale(or even smaller)architecture on the surface.Besides,there is an energy barrier between the Cassie-Baxter wetting state and the Wenzel wetting state.An optimized square post micro structure with truncated square pyramid geometry is introduced in this work to increase the energy barrier,enhancing the robustness of super-hydrophobicity.Theoretical analysis is conducted based on the wetting transition energy curves.Numerical simulation based on a phase-field lattice Boltzmann method is carried out to verify the theoretical analysis.The numerical simulation agrees well with the theoretical analysis,showing the positive significance of the proposed micro structure.Furthermore,another novel micro structure of rough surface is presented,which combines the advantages of truncated pyramid geometry and noncommunicating roughness elements.Theoretical analysis shows that the novel micro structure of rough surface can effectively hinder the Cassie-Baxter state to Wenzel state transition,furthefly enhancing the robustness of the surface hydrophobicity.

A model study on affordable steel residential housing in China

The main research purpose of this paper is to acquire a series of designed concept of"affordable housing"in key geographical areas of East China through the development of innovative,economical,flexible,reproducible and affordable residential houses using intensive steel solutions.Toward this goal,both the residential housing conditions and the development of steel residential building in China are widely investigated.Affordable housing in China is then,based on the investigation,defined as green humanized multi-storey housing comprised of medium-small type dwellings whose construction cost is not much higher than that of traditional reinforced concrete buildings and the maintenance cost is low.Taking this definition as a guiding ideology,detailed architectural and structural design of a steel affordable housing model in terms of a collective housing form with repeatable living units has been carried out.Comparisons of project cost and energy consumption between the designed steel residential housing and the corresponding reinforced concrete building show that the former is not more expensive and consumes less energy than the latter.

Thermal Analyses of Power Electronics Integrated with Vapour Chamber Cooling

Insulated gate bipolar transistor(IGBT)power module is used for power switching transistor devices in the power supply and motor control circuits in both hybrid electric vehicles and electric vehicles.The target of heat flux of IGBT is continuously increasing due to the demand for power rating improvements and miniaturisation.Without suitable efficient cooling technolo-gies,excessively high temperature and uneven temperature distribution can cause high thermal stress,eventually leading to severe module failures.Therefore,highly efficient cooling solutions are highly required.Vapour chamber with phase change can provide quick heat transfer and low temperature gradient.This study proposes a new IGBT structure integrated with vapour chamber.The tests and simulation results indicate that the thermal and thermo-mechanical performances of IGBT integrated with vapour chamber are better than those of the IGBT with copper baseplate module.The thermal resistance between the junction and heat sink is reduced from 0.25 to 0.14°C/W,and the temperature uniformity is greatly improved due to the phase change in the vapour chamber.The simulation also investigates the thermal stress distribution,deformation and thermal fatigue lifespan of IGBT power electronics module.A reduction of 21.8%in thermal stress and an increase of 9%in lifespan of Sn-3.5Ag solder are achieved.