高烈度区斜拉桥横向约束方案优化分析

为了确定强震作用下斜拉桥合理的横向抗震约束体系,以可克达拉大桥为工程背景,采用非线性时程分析法,分析了4种横向约束体系即横向滑动体系、全限位体系、位移相关型减震体系和速度相关型减震体系对强震区大跨度桥梁地震响应的影响,重点对钢阻尼器的屈服荷载和黏滞阻尼器的位置及相关参数进行优化分析,并与其他体系的地震响应进行了对比。结果表明：在强震作用下,对于大跨度桥梁横向滑动体系和全限位体系均不是理想的抗震体系;而在墩梁、塔梁之间设置减隔震装置可以有效减少横桥向的墩梁、塔梁的相对位移及地震剪力和弯矩;然而,从桥梁正常使用的角度来看,塔梁之间布设横向钢阻尼器装置优于黏滞阻尼器装置。     

考虑滑移和剪切变形的单箱双室组合箱梁剪力滞效应

为准确分析单箱双室组合箱梁的剪力滞效应,考虑钢混凝土的界面滑移效应和钢腹板的剪切变形,针对顶底板和翼板定义不同的剪力滞翘曲位移函数,基于能量变分法推导出单箱双室组合箱梁剪滞效应的控制微分方程及其闭合解。以单箱双室组合箱梁算例为基础,利用该方法分析其剪力滞效应的规律,结果表明：在同时考虑滑移和剪切变形时,组合箱梁的挠度比初等梁理论解大,且其挠度随界面滑移刚度的增大而减小;组合箱梁在均布荷载作用下,滑移量与荷载值近似成正比关系;在相同条件下,钢箱梁底板的剪力滞效应较混凝土顶板显著。     

刚性连体位置对非对称双塔连体结构动力可靠度的影响

考虑地震动的非平稳性,变化连体位置,对非对称双塔连体结构运用虚拟激励法进行非平稳随机激励下的动力可靠度研究。采用刚度退化的Bouc-Wen模型模拟塔楼各楼层的滞变特性,建立非线性化动力方程。运用混合精细积分法对每一时刻的响应进行求解,得到连体位置变化时非对称连体结构在非平稳随机激励下的时变方差。基于首次超越破坏准则与Markov假定,研究非平稳随机地震激励下连体结构的动力可靠度。运用上述理论,在8度罕遇地震作用下对某非对称双塔连体结构进行随机地震响应与动力可靠度分析。研究结果表明,地震作用下结构的层间位移响应呈现强烈的非平稳性,变化连体位置对连体结构的随机地震响应与动力可靠度将产生显著影响。     

上覆分数阶粘弹性饱和场地土位移地震放大系数

考虑土体液相和固相的耦合作用,将基岩上覆场地土视为两相饱和多孔介质。为了考虑饱和场地土的粘弹性特性,其固相土骨架的应力应变关系利用分数阶Kelvin粘弹性模型来描述,建立了上覆分数阶粘弹性饱和场地土在简谐地震波作用下的运动控制方程。运用分数导数的性质并考虑上覆场地土的边界条件和透水性条件求解了上覆分数阶粘弹性场地土在简谐地震波作用下的振动问题,得到了饱和场地土的位移地震放大系数。采用数值算例分析讨论了分数导数的阶数、液固耦合系数、土体模型参数、基岩土体剪切模量比等参数对位移地震放大系数的影响。研究结果表明,分数导数的阶数、液固耦合系数、土体模型参数、基岩土体剪切模量比对饱和场地土的地震响应有较大的影响,通过压实场地土,可以达到增大液固耦合系数减小地震响应的作用,通过增大饱和场地土的粘性和剪切模量也可以减小地震反应。     

填充床中细小颗粒渗流行为的DEM模拟

为进一步探索COREX过程固体物料的运动状态,对COREX过程中涉及到的细小颗粒渗流行为进行了DEM模拟。考察不同颗粒直径比、阻尼系数及滑动摩擦系数对细小颗粒渗流行为的影响,特别是计算得到不同模拟参数下细小颗粒在填充床内的运动轨迹。模拟结果显示,渗流过程中细小颗粒的平均渗流速度为一定值。随着颗粒直径比的增加,颗粒竖直方向的渗流速度逐渐减小,停留时间与径向弥散逐渐变大。随着颗粒间阻尼系数的增加,颗粒渗流速度逐渐增加,停留时间逐渐减小,径向弥散逐渐变小。滑动摩擦系数对细小颗粒的渗流行为影响较小。从细小颗粒运动轨迹分析可知,颗粒直径比变大时,细小颗粒易在空隙中缓慢移动,易趋于静止床层中,导致颗粒沉积。随着颗粒间阻尼系数变小,颗粒运动轨迹向填充床边缘发展,偏离床层中心。     

Y形偏心支撑高强钢框架结构抗震性能

在Y形偏心支撑高强钢框架结构抗震性振动台试验的基础上,建立了试验试件的有限元模型,并验证了分析的正确性。设计了一个9层的Y形偏心支撑高强钢框架结构,以耗能梁段长度、耗能梁段腹板高厚比、高跨比为参数,对9层结构进行了非线性动力时程分析,研究了以上参数对结构抗震性能的影响。研究结果表明,改变耗能梁段长度、高跨比对结构层间侧移、耗能梁段性能、框架柱弯矩、耗能能力均有不同程度的影响,对框架柱轴力、基底剪力无显著影响;改变耗能梁段腹板高厚比对结构耗能能力有影响,对结构层间侧移、耗能梁段性能、框架柱受力、基底剪力无显著影响,并给出了相关设计建议。     

栽植密度对毛白杨无性系生长性状遗传变异的影响

为了选择最适栽培品种及栽培措施,通过毛白杨无性系区域化密度栽培试验（以4个无性系和7种栽植密度采用完全随机区组设计,以河北威县营造的试验林为研究对象）,揭示密度对无性系生长的作用规律。结果表明：从造林当年开始,树高、胸径在无性系间就具有显著差异,S86和BT17无性系明显优于1316和B331无性系;密度对胸径生长的显著影响在造林后2年出现,且显著程度随林龄增大而增大,密度对树高生长的影响在造林后2~3年差异最大;密度×无性系互作对4年生林分胸径、树高的影响不显著;833株/hm2是4个无性系密植的最小底线,高于该密度无性系对胸径的影响,随林龄和密度增大而减小,低于该密度随林龄增大而增大、随密度减小而降低;高密度下无性系对树高的影响随林龄增大或密度减小呈先降低后增大趋势,低密度下随林龄增大呈先增后降趋势;无性系对胸径遗传变异系数的影响在密度间差异不大,无性系×区组互作变异系数及基因型内株间变异系数2年生前在密度间差异较大;无性系×区组互作对树高遗传变异系数的影响随年龄增大呈先增后减趋势,而树高在株间的变异系数随年龄增大而增大;以无性系均值计算的树高广义遗传力在密度间不显著,以单株值计算的树高广义遗传力在密度间差异显著,而2种方式计算的胸径广义遗传力在密度间差异均极显著,在年龄间差异均不显著。     

地震序列下拉索模数伸缩缝联间限位分析

主震作用下桥梁结构可能已发生联间相对变位,强余震作用将进一步加剧桥梁上部结构的碰撞或落梁灾害,以某连续梁桥为例进行地震序列分析,并对比有无拉索模数伸缩缝两种情况下的地震响应,结果表明:拉索模数伸缩缝能够有效限制主余震各阶段联间相对位移,对避免主震后产生联间残余位移的桥梁结构在强余震作用下发生碰撞、落梁具有重要意义;同时,拉索模数伸缩缝使桥梁各联间协同作用,从而墩梁相对位移得到相应的控制,桥墩受力亦有所改善。     

土壤基质势对盐碱地设施番茄生长及光合指标的影响

为指导滨海盐碱地设施番茄中前期的合理灌溉,以春茬番茄为研究对象,采用滴灌方式灌溉,设置4个不同基质势处理(-10、-15、-20、-25 kPa),研究其对设施番茄中前期生长及光合指标的影响。随着滴头正下方0.2 m深度处土壤基质势的降低,灌溉水次数明显减少;株高、茎粗、叶长生长指标随着基质势降低逐渐减小,-10、-15 kPa处理间差异不显著;生物量随基质势下降逐渐减小,低于-15 kPa的基质势番茄植株鲜重降低明显,-10、-15 kPa间差异不显著;净光合速率、气孔导度、蒸腾速率、胞间CO₂浓度等光合指标随基质势降低呈减小趋势,-10、-15 kPa处理间各指标差异不显著,与其他2个处理达到显著水平;总根长、总根体积、总根表面积随基质势降低逐渐减小,-10、-15 kPa处理间指标差异不显著,而>4 mm的粗根系数量以-15 kPa基质势处理下最高,与其他3个处理均达到显著水平。在滨海盐碱区番茄中前期生长阶段,以控制滴头正下方0.2 m深度处土壤基质势下限-15 kPa指导灌溉为宜。     

湿养条件下红萍产量与能耗的关系研究

【研究目的】通过不同人工光源能耗下湿养红萍的产量试验,明确红萍湿养产量与人工光源能耗之间的关系。【方法】在自行研制的红萍湿养栽培装置上,利用T4荧光灯设置3个不同的光强范围,并在相同湿养空间下设计5个不同的光源配置方案进行红萍湿养的产量比较试验。【结果】单位湿养面积下,红萍表面光照强度在6000-7000Lux时产量最高,单位能耗日产鲜萍量也最高,过低（3000-4000Lux）和过高的光强（9000-10000Lux）都会影响红萍产量和单位能耗日产鲜萍量的提高;红萍湿养的产量与扎入湿养介质根的数量和长度呈显著正相关;同一湿养空间下,降低层间距,减少荧光灯使用数量,可以提高能耗转化产量的效率。【结论】相同湿养空间下,保持红萍表面光照强度在6000-7000Lux,通过适当增加层数或者降低层间距来调整人工光源配置以达到降低能耗的目的,可以实现以较低能耗获得较高产量的效果。     

Parameter Optimization Analysis of Viscous Dampers for Dissipation Structure

The design method of parameter optimization of nonlinear viscous dampers for dissipation structure was analyzed based on response surface methods. The method included experimental design, finite element analysis, fitting the response surface function and parameter optimization. Taking a reinforced concrete frame structure for an instance, the mathematical model of parameter optimization of viscous dampers for dissipation structure was established by taking the minimum all damping force as objective function and taking the interlayer maximum displacement less than limits as constraints, and then the damper parameters were optimized using the method of nonlinear programming optimization. The results show that the method of parameter optimization of viscous dampers based on response surface method can ensure the structural displacement is less than limit and the construction cost can be reduced.     

Research on Seismic Behavior of Top-bear Arch Bridge with Viscoelastic Damping Braces

This paper proposes a new method of structure control that to set damping braces in a top - bear arch bridge. Lumped damping can be introduced to structures to reduce seismic response. The FEM analysis of Nimu bridge which is braced with viscoelastic dampers had done. The results show that the viscoelastic damping braces can remarkably decrease displacement within the arc plane, which is an efficient structure control method.     

Seismic Performance Analysis and Optimum Design of RC Frame Structure Retrofitted by Viscidity Dampers

For a reinforce concrete frame structures which is not satisfied the standard for seismic appraiser of building, viscidity dampers are used to retrofit the structure. Four reinforce schemes are selected in which six same viscidity dampers are located at different position of the structure. Compared seismic performance of the retrofited structure with unretrofited one, an optimum scheme where viscidity dampers should better set is obtained. Then the number and technical parameter of viscidity dampers are adjusted, and seismic performance of the structure are calculated. The results are compared and a more economic scheme is obtained because the cost is lowest and the displacement of the structure under earthquakes is satisfied the standard for seismic appraiser of building. Several rules and advices are gotten about how to use the viscidity dampers to retrofit reinforce concrete frame structures. The conclusion about viscidity dampers are useful for similar actual engineering.     

Design optimization of magneto-rheological damper based on finite element parametric language

The mountain hazards like snow avalanches, landslides, rock falls, debris flows and so on all have strong power of destruction which seriously threaten human’s lives and belongings. Therefore, it is necessary to study more the development of these disasters in order to prevent them. Setting up obstacles is the primary measure to control the movement and deposition process of mountain hazards. For the study of the influence of this measure on the development of disasters, the numerical simulation calculation aiming at the flow and deposition process of the granulars flowing past different built obstacles was made by the theory of SH granular flow and the method of finite volume discretization based on Roe's Scheme. Futhermore, the influence of different settings of obstacles on the granular flow is discussed. The numerical results show that the settings of obstacles have a great effect on the process of granular flow. That is, the effective precaution against the disasters is no other than setting up the obstacles correctly. As the numerical simulation calculation can optimize the setting of obstacle, it provides a reasonable and economic reference scheme of disaster prevention and planning of mountain area.     

Damping Force of Electro-rheological Damper

There are three working modes of electro rheological(ER) damper, flow mode of fixed electrode, shear mode of slide electrode, mixer mode of slide electrode. The damping force is analyzed for gas-filled ER damper of flow mode of fixed electrode. There are three sections of damping force, and they are background damping force of a fluid viscosity, electric damping force of applied electric field and pressure of gas. The characteristic of ER damper is adjustable by electric filed strength for electric damping force. At the same time, some structure factors of ER damper are discussed.     

Theoretical Analysis and Numerical Simulation of Variable Curvature Friction Pendulum Isolation Bearing

The basic structure of Variable Curvature Friction Pendulum Isolation Bearing (VCFP) is introduced. Based on the principle of mechanical equilibrium, theoretical analysis on two types of VCFP which are Variable Frequency Pendulum Isolation Bearing (VFPI) and Conical Friction Pendulum Bearing (CFPI) are conducted. The stiffness of each VCFP is derived, and the recovery characteristics were discussed and the computing formula of maximum residual displacement was deduced as well. Moreover, with the use of ABAQUS software, the models with solid element of each VCFP are built, and the hysteresis property under low cyclic loading and recovery characteristic are simulated. The comparative analysis of VCFP and Friction Pendulum Bearing (FPB) are also conducted. The results show that: 1) the numerical simulation results are identical to the theoretical analysis; 2) according to its plump hysteresis loops, the hysteresis property of VCFP is favorable, further more, its effective viscous damping ratio and coefficient of energy dissipation are higher than FPB, which indicates its greater ability in energy dissipation; 3) the stiffness of the VCFP is determined by curvature radius, that is, sliding surface function. And its stiffness decreases with the increase of bearing displacement through rational design. And then its isolation period increases as the displacement increases and the low frequency resonance problem of isolated structures can be well solved; 4) compared with FPB, the softening mechanism of stiffness can make the shear force transferred to superstructure decrease; 5) the maximum stress of bearing appears when the bearing reaches its designed displacement, and in general it may situate in the edge of ball joint surface of slider or bearing plate 6) the maximum residual displacement of VCFP depends on both friction coefficient and the parameters of sliding surface function, therefore, parametric design based on analysis or simulation is necessary so as to control the maximum value in an acceptable range in engineering.     

Improved Modal Capacity Spectrum Method for Estimating Seismic Performance of Structures

Performance-based seismic design involves how to confirm inelastic displacement demand of structures under earthquake in concise and reasonable way. Two shortages need to improve in analyzing the elastic-plastic seismic responses of structures if the traditional capacity methods are employed. The shortages are the uncertainty of equivalent high damp of elastic-plastic structures and the limitation of the higher order vibration mode effect being not taken into account. To solve these problems, the authors propose the concept and analyzing process of improved capacity spectrum method based on modal pushover analysis and the elastic seismic responses spectrum modified by strength reduction coefficient and ductile coefficient. The example of analyzing the performance of frame structure is shown which may be a simple and effective method used in engineering. This method has application potential in Performance-based seismic design.