Dynamic performance of angle-steel concrete columns under low cyclic loading-I:Experimental study

This paper describes low cyclic loading testing of nine angle-steel concrete column （ASCC） specimens. In the tests, the influence of the shear-span ratio, axial compression ratio and shear steel plate ratio on the hysteretic behavior, energy dissipation, strength degradation, stiffness degradation, skeleton curve and ductility of the ASCCs is studied. Based on the test results, some conclusions are presented. The P-A and sectional M -φ hysteretic models for the ASCCs are presented in a companion paper （Zheng and Ji, 2008）.

Dynamic performance of angle-steel concrete columns under low cyclic loading-II:parametric study

Tests of nine angle-steel concrete column （ASCC） specimens under low cyclic loading are described in a companion paper （Zheng and Ji, 2008）. In this paper, the skeleton curves from the numerical simulation are presented, and show good agreement with the test results. Furthermore, parametric studies are conducted to explore the influence of factors such as the axial compression ratio, shear steel plate ratio, steel ratio, prismatic concrete compression strength, yield strength of angle steel and shear span ratio, etc., on the monotonic load-displacement curves of the ASCCs. Based on a statistical analysis of the calculated results, hysteretic models for load-displacement and moment-curvature are proposed, which agree well with the test results. Finally, some suggestions concerning the conformation of ASCCs are proposed, which could be useful in engineering practice.

Research on reasonable winding angle of ribbons of Flat Steel Ribbon Wound Pressure Vessel

Flat Steel Ribbon Wound Pressure Vessels (FSRWPVs) are used in many important industry areas. There is no such kind of pressure vessel exploding on operation for its reasonable structure design. Many explosion experiments on Flat Steel Ribbon Wound Pressure Vessel showed that their limited load pressure is related to the winding angle of the steel ribbons. FSRWPVs with reasonable winding angle have better security and lower cost. Reasonable angels given at the end of this paper facilitate engineering design.

Effect of fiber angle on LYP steel shear walls behavior

Steel shear wall(SSW) was properly determined using numerical and experimental approaches.The properties of SSW and LYP(low yield point) steel shear wall(LSSW) were measured.It is revealed that LSSW exhibits higher properties compared to SSW in both elastic and inelastic zones.It is also concluded that the addition of CFRP(carbon fiber reinforced polymers) enhances the seismic parameters of LSSW(stiffness,energy absorption,shear capacity,over strength values).Also,stress values applied to boundary frames are lower due to post buckling forces.The effect of fiber angle was also studied and presented as a mathematical equation.

Small-angle neutron scattering study on the stability of oxide nanoparticles in long-term thermally aged 9Cr-oxide dispersion strengthened steel

A 9 Cr-oxide dispersion strengthened(ODS)steel was thermally aged at 873 K for up to 5000 h.The size distribution and chemical composition of the dispersed oxide nanoparticles were analyzed by small-angle neutron scattering under a magnetic field.Combined with transmission electron microscopy,Vickers micro-hardness tests and electron backscattered diffraction measurements,all the results showed that the thermal treatment had little or no effect on the size distributions and volume fractions of the oxide nanoparticles in the ferromagnetic matrix,which suggested excellent thermal stability of the 9 Cr-ODS steel.

Regardless of the Puncture Angle, a Tuohy Needle with Sand-Blasted Steel at the Tip of the Bevel Is a Valid Needle on the Ultrasonic Images

Background: A high ability to visualize the needle on the ultrasonic images is necessary to perform the ultrasound-guided nerve block safely. The Rafa Tuohy needleR (Vygon, Paris, France, Rafa) is a non-stimulating Tuohy needle with sand-blasted steel at the tip of the bevel. We examined the degree to which the Rafa enhanced the visibility of ultrasonic images compared with the non-coated Tuohy needle. Methods: We punctured the Blue Phantom. The dimensions of both the Rafa and the non-coated Tuohy needles were 18 G × 80 mm. The puncture angle is 30 degrees and 45 degrees from the Blue Phantom. We measured the intensity of the tip of the bevel at a depth of 0.5, 1.0, 1.5 and 2.0 cm for the puncture angle of 30 degrees, and 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 cm for the puncture angle of 45 degrees. Six anesthesiologists with more than seven years of experience performed three punctures using each needle. Results: As an outcome, we concluded that at a puncture angle of both 30 degrees and 45 degrees, the intensity of the non-coated Tuohy needle decreased with the depth. On the other hand, at an angle of 30 degrees, the intensity of the Rafa needle did not decrease, and at an angle of 45 degrees the intensity only decreased very slightly as the depth increased. Conclusions: The Tuohy needle with sand-blasted steel at the tip of the bevel provided greater visualization than the non-coated Tuohy needle on the ultrasound images.

Joint member angle limits of composite beams and CFT square columns

This work aims to understand the relationship between the member angle limit and the energy ratio for 24 test samples of composite beams and CFT square steel tube columns. This work also compares the formula applicability for member angle limit with the previous test result to provide the basic data for the design of composite beam-CFT column. The evaluation of the member angle limit was performed with concrete compressive strength (fC =22.16 MPa, 30.49 MPa), breadth-to-thickness ratio (B/t=25.0, 33.3, 43.5), and axial capacity ratio (N/N0=0, 0.3, 0.4, 0.5) as the main variables of the test samples. For the relationship between the member angle limit (Ru) and the energy ratio (ES/EC ), the test result shows that the energy ratio becomes lower as the axial capacity ratio and the breadth-to-thickness ratio increase. The energy ratio is lower for the Type B test sample compared with that of Types A and C. For the formula suggested by SATO, the test samples are distributed evenly for comparison between test values and the member angle limit; however, other formulas indicate a deviation. Specifically, for the comparison between R u,cal and R u (Test), Maeda's formula shows severe deviation.

STUDY ON THE MECHANISMS OF EROSION OF METALS AT LOW IMPACT ANGLE

The mechanisms of solid particle erosion of several pure metals and steels at low impact angle were studied comprehensively by SEM observations of the worn surface,wear debris analysis, subsurface hardness measurements, incremental erosion tests and sequential erosion study techniques. It was found that at the beginning of erosion,craters and lips were formed on the surfaces of ductile metals due to the deformation caused by the impacting of the particles.The deformed lips were then forged back and forth again and again in erosion process. As s resuit,small chips of deformed lips were stripped off continuously in the process. All of the evidences show that the erosion mechanisms are encompassed mainly by the process of plastic deformation,lip formation and spalling with ductile metals,while microcutting is more easy to occur with hardened steels.

Experimental Behavior of Recycled Aggregate Concrete Filled Steel Tubular Columns

During the modernization or rehabilitation activity,the demolished structural waste causes large soil pollution and unavailability of natural aggregate is the big concern for the construction industry.Therefore,this manuscript deals with the Composite Steel Circular Column(CSCC)with Recycled Aggregate concrete(RAC)as infill is partly used,with the replacement of 25%and 50%in M30 grade of Concrete.And internal reinforcement steel is fully replaced by rolled steel tubes(circular and square)with varied thickness,ISA-unequal angle.Around 14 specimens are cast and examined under axial load for analysis of the deflection characteristics,the load-bearing capacity along with its buckling behavior.The experimental values are estimated through LVDT(linear variable differential transducer)at 3-phase.The curve of load-deflection is drawn with the load pattern.From the date interpretation,it is found column made of 50%-RAC has more than 25%-RAC.

两种钛合金半穿甲战斗部侵彻单层钢靶性能试验研究

选取亚稳态β型TB17和高损伤容限α+β型TC4-DT两种高韧钛合金材料,对2种钛合金材料在高应变率条件下动态力学响应特性进行测试分析,并应用125 mm火炮发射装置开展2种钛合金半穿甲战斗部侵彻单层钢靶性能试验研究。结果表明,作为半穿甲战斗部的壳体材料,应选择屈服强度与冲击韧性匹配性好的钛合金,其中更应关注钛合金材料的塑性变形能力和抗冲击韧性;随着侵彻着角的增加,侵彻单层钢靶过程弹体头部侵蚀量及径向墩粗程度更严重,不利于弹体保持侵彻强度及装药安定性。

大倾角钢箱提篮拱桥总体设计

考虑施工技术、经济性和景观效果等方面,陕西蔡家坡渭河特大桥主桥采用(35+210+35) m大倾角钢箱提篮拱桥。该桥采用摩擦摆和环向钢丝绳阻尼支座综合减隔震约束体系,以降低结构的地震响应。拱肋为单室等宽钢箱截面,采用主、副拱肋2条悬链线,主、副拱肋共面,设计为横向内倾20°的大倾角,在提高桥梁景观效果的同时,又有效提高了结构的整体稳定性;拱肋设钢-混结合段连接拱脚与混凝土拱座。桥面系采用自重较轻的正交异性钢桥面板结构。吊杆采用抗拉强度1 860 MPa的环氧柔性钢绞线。基础采用Φ2.5 m的钻孔灌注群桩,以抵抗软弱地质条件下荷载的竖向及水平作用力。该桥总体采用先梁后拱的施工方案。整体及局部有限元分析结果表明,桥梁结构力学性能均满足规范要求,设计安全可靠。

水平往复荷载作用下钢箱提篮拱弹塑性力学性能研究

目的 探究倾角、矢跨比及宽跨比三个参数对钢箱提篮拱在水平往复荷载作用下力学性能的影响,为钢提篮拱桥抗震设计提供理论基础。方法 通过改变参数,建立54个钢箱提篮拱有限元模型,在水平往复荷载作用下进行滞回分析,研究钢箱提篮拱水平力-位移滞回性能、极限承载力和拱顶横撑内力、变形在不同参数条件下的变化规律。结果 随着拱肋倾斜角度、宽跨比的增加或矢跨比的减小,结构初期刚度、极限承载能力均有较大提高,但横撑内力也随之增加,并会产生局部失稳破坏,影响结构的承载能力。结论 增加拱肋倾斜角度对钢箱提篮拱横向力学性能有较大改善,但在设计时应注意横撑内力增加带来的不利影响。

小角中子散射谱仪放射性样品测量装置研制

辐照试样研究对评估材料性能具有重要意义。因其带有放射性,常规表征手段受到一定限制,而小角中子散射(Small-Angle Neutron Scattering,SANS)技术几乎不受γ、β等射线的影响,且制样简单。依托中国先进研究堆小角中子散射谱仪,研发了一台放射性样品测量装置,用于放射性试样内部纳米结构的测量分析。装置的屏蔽厚度利用蒙特卡罗模拟进行优化,结合自动换样和远程控制功能,提高了实验效率和安全性。利用该装置成功开展了A508-Ⅲ钢辐照监督试样的小角中子散射实验,结果表明低剂量长周期辐照对压力容器钢纳米结构影响较小。该装置和相关技术方法可用于放射性试样的纳米结构表征。

基于数值模拟的选区激光熔化成形残余应力演化研究

目的以选区激光熔化成形(SLM)试件的残余应力为研究对象,研究残余应力对成形质量的影响,为SLM成形的产业化应用提供理论依据。方法以316L不锈钢粉末为原材料,利用AltairInspire软件的Print3D模块分析SLM成形中支撑、成形角对残余应力的影响及残余应力的演化规律,并进行实验验证。结果SLM成形最大残余应力出现在零件与基板结合面,添加支撑可减小残余应力。零件不同位置残余应力的演化规律不同。顶部残余应力呈先增大后减小的趋势,底部两侧残余应力呈缓慢上升的趋势;底部中间残余应力的演化规律较为复杂:起先残余应力随温度的降低而增大,当温度降到最低点时达最大值;随后在热累积作用下,残余应力先减小后增大,当达到去应力退火温度时,残余应力又减小并在一定范围内波动。残余应力随着成形角的增大呈先增大后减小再增大的趋势,当成形角为60°时,残余应力较小。结论在SLM成形时,在零件底部添加支撑可将最大残余应力位置转移到支撑上,从而减小成形件内部的残余应力,提高成形质量。成形零件不同位置残余应力的演化规律不同,成形角对残余应力的影响也不同,成形时应根据零件工况制定合适的打印策略。

柱脚设角钢的高强钢棒混凝土方柱抗震性能研究

以低粘高强钢棒作为主筋的混凝土柱,能在直至大变形阶段均具有稳定增长的承载力和较小的残余变形,有良好的自复位性能,但耗能能力较延性柱弱。该研究在高强钢棒混凝土方柱的柱脚配置角钢,在保证高强钢棒混凝土柱良好自复位性能的基础上提高其水平承载力和耗能能力。设计并制作了4根柱脚配置角钢和1根无角钢的高强钢棒混凝土方柱,进行低周往复加载试验,研究柱脚有无角钢、角钢厚度和轴压比、剪跨比对柱水平承载力、残余变形和耗能能力的影响。试验结果表明:所有高强钢棒柱加载直至位移角4%仍保持持续增长的承载力,加载位移角为2%和4%时的残余位移角分别在0.5%和1%以内,构件可修复概率分别能达100%和50%;与无角钢柱相比,相同轴压比的柱脚配置角钢的混凝土柱受弯承载力提升率达47%,单循环耗能提升最大达94%,累积耗能提升达24%;随着剪跨比的增加,试验柱的承载力下降;随角钢厚度的增大,承载力提升率增大,而耗能提升率减小。

碳纤维加固输电铁塔角钢有效性分析

以输电铁塔受损角钢为研究对象,借鉴国内外碳纤维增强复合材料(CFRP)加固修复技术,提出采用碳纤维布加固铁塔角钢的方法。该方法采用胶黏剂将碳纤维布粘贴至角钢表面进行加固,加固过程中不会对角钢产生二次损伤,且流程简便,实用性强。通过建立组合结构数值分析模型,研究碳纤维布加固厚度、加固层数、铺层角度和加固方式对组合构件加固效果的影响。结果表明:使用碳纤维布加固角钢对长细比较大构件承载力的相对提高程度会增大;当采用四层铺设厚度共为0.668 mm的碳纤维布时,对角钢极限承载力的提升基本可以满足加固需求;碳纤维布各铺层角度沿角钢轴心受压方向均采用0°方向进行铺设时,可以最大化加固效果;结合经济性考虑,对角钢进行中包加固方式效果要优于全包加固效果。

可控转角摩擦型铰节点滞回耗能研究

提出一种可控转角摩擦型铰节点,介绍了该节点的构造。利用既有试验对有限元软件ABAQUS模型材料参数进行验证,结果表明,试验结果与数值模拟结果吻合较好。建立25个不同参数的节点模型,探究螺栓预紧力、拼板间摩擦系数、梁固定端距销轴轴心距离、梁连接端肋板厚度、梁连接端肋板外伸长度、节点处肋板厚度、节点处肋板外伸长度共7个变化参数对节点滞回耗能的影响。通过拟合获得的数据,建立了节点摩擦反力提高系数与摩擦系数、节点安全储备系数与摩擦系数的关系曲线。结果表明:当节点转角大于设定转角后,节点产生的限位接触使节点反力大幅增加,实现限制节点转角的目的;摩擦系数在0.35左右耗能最大;在节点转角小于设定转角时,滑动摩擦反力与螺栓预紧力的比值约等于摩擦系数;节点最终破坏的总耗能随螺栓预紧力的增加而增大;螺栓预紧力超过规范规定的设计值时,对节点的累积耗能提高程度不明显;梁固定端距销轴轴心距离在梁高的0.95至2倍时耗能最佳;梁固定端距销轴轴心距离过大时,将降低节点的极限反力;梁连接端肋板厚度、梁连接端肋板外伸长度、节点处肋板厚度和节点处肋板外伸长度对节点滞回性能影响不显著。

粗轧板坯自动转钢系统研究与应用

宽厚板生产过程中,其粗轧工艺需控制交叉的锥形辊实现板坯长宽方向的对调,该过程严重依赖人工操作,节奏无法有效控制,制约生产线智能化改造进程。结合视觉检测和自动控制技术设计的粗轧板坯自动转钢系统可有效解决该问题,在粗轧机出入口分别安装视频监控相机,捕捉转钢辊道区域上板坯的状态,利用改进的包含去雾模块的PIDNet(proportional-integral-derivative network)模型提取板坯前景轮廓,通过组合式角度度量方法实时跟踪板坯旋转角度。过程中融合安全限位、位置优选、速度调控、过转修正等策略共同优化转钢控制,保证转钢的安全稳定,自主学习人工经验提升转钢效率。应用结果表明,系统可准确测量板坯角度并实现自动转钢功能,能够替代人工操作,节省能耗,实现智能化生产的目的。

工艺参数对磨料水射流切割钢板效果的影响

基于有限元(FEM)与光滑粒子流体动力学(SPH)耦合方法,利用数值模拟手段研究了磨料水射流切割钢板的加工机理,重点分析了磨料浓度、射流压力、射流角度对切割钢板效果的影响。结果表明,加入磨料的水射流对钢板的切割能力明显提高,切割截面呈“U”型;随着磨料浓度的增大,钢板切割深度呈增加趋势,切口宽度则变化不大;钢板切割深度随射流压力的提高则呈近似线性增加的趋势;当射流角度由垂直(90°)转变为一定倾斜角后,钢板切割深度有所降低,材料的整体去除量略有减少。

强对流天气下输电塔-线体系倒塌破坏与风雨组合系数研究

极端气象灾害给输电线路的安全运行带来了严重威胁,相对低电压等级的角钢输电塔出现了较高频次的倒塌破坏事故。基于现象学非线性滞回模型,开展了输电塔-线体系在强对流天气下的倒塌破坏研究,总结了雨荷载对输电塔响应的影响规律;基于风雨气象记录,进行了风雨组合分析并提出了风雨组合系数。结果表明,在极端强对流天气中,所研究输电塔的薄弱部位主要为第3、4节段,该部位的大量斜材和少量主材陆续屈曲是造成输电塔倒塌的主要原因,极端风雨气象条件下有必要考虑雨荷载对输电塔-线体系响应的影响。不同重现期下风速和雨量的组合值均小于其相应的标准值,该地区50 a重现期下风速和雨量的组合系数建议值分别为1.0和0.7。