Suitability of Bi-linear Restoring Force Model in Earthquake Response Analysis

Based on the data of dynamic tests of small single-storey steel frames,the suitability of simplified hi-linear restoring force model in earthquake response analysis is discussed, and the Maximum displacement response MD, the sum of squares of the displacements in the whole vibrating history SSD, and the total dissipated energy EI are considered respectively as equivalent object.     

响应曲面法优化高粱挤压最佳操作参数的研究

以高粱为原料,研究系统操作参数,包括:物料含水率、喂料速度、螺杆转速、机筒温度对目标参数的影响,并以响应曲面法优化最佳操作参数,优化得到的最佳操作参数为:物料含水率15.77%,喂料速度26.97r/min,螺杆转速181.20r/min,五区温度158.28℃。     

关中西部农村居民地震灾害认知与响应研究-以宝鸡市陈仓区为例

为制定农村防震减灾相关政策并为其提供实证依据。采用问卷调查和比较分析的方法,对宝鸡市陈仓区农村居民的地震灾害认知与响应进行调查研究。结果表明：(1)居民地震灾害知识的准确性和深度不够,防震减灾技能掌握不足;(2)居民有一定的自救互救意识,但主动性和组织性较差,地震谣言辨别能力不强;(3)居民地震灾害认知与响应的总体水平不够理想,其中防震减灾技能最差,自救互救实况最好。表明开展地震灾害知识普及、防震减灾技能培训和地震信息甄别工作是增强农村地区防震减灾综合能力的有效途径。     

Least-square-based Optimization of Frequency Response Function Estimation in Modal Parameters Identification

The accuracy of modal parameters identification has the influence on the quality of dynamic characteristics analysis of mechanical structure directly. And the precision of the frequency response function estimation has the great influence on the accuracy of modal parameters identification. In the engineering the frequency response function can be estimated by the average power spectrum and cross-power spectrum with the hel Pof FFT. As the result of limited frequency resolution in the course of FFT and the noise, the accuracy of modal parameters identification is influenced by the frequency response function estimation. This paper has put forward a least-square-based optimization of frequency response function estimation in modal parameters identification. According to the optimized frequency response function, the peak value can be searched to identify the damped natural frequencies and damping ratio directly. An experiment has been made to validate the proposed method. The result indicates that the damped natural frequencies and damping ratio identified by the optimized frequency response function are closer to the true results than which without the optimized frequency response function. So the accuracy of modal parameters identification can be improved by adopting the proposed method.     

Effects of Response Spectra Dispersion of Earthquake Ground Motions on Probabilistic Seismic Demand Assessment of Bridge Structures

A three-span regular continuous RC girder highway bridge and two bins of real accelerograms were selected for incremental dynamic analysis to study the correlation of the dispersions of response spectra of earthquake ground motions and probabilistic seismic demand assessments of bridge structures. It is found that the dispersions of seismic demands are closely related to the dispersions of response spectra of selected ground motions. The rational selection of real earthquake ground motions to be rationally chosen for dynamic analysis can make the probability distribution of seismic demands in accordance with the real situation and improve the computational precision and efficiency of the probabilistic seismic demand assessment and fragility curve for performance-based earthquake engineering and seismic design of bridges based on probability theory.     

Earthquake Response Properties of the Support Structure of Large Cross Section Tunnel

The response properties of displacement and stress of tunnel support structure are discussed in detail under the action of horizontal earthquake acceleration(Ya),longitudinal earthquake acceleration(Za) and horizontal-longitudinal earthquake acceleration(YZa).This discussion is based on an analysis of the surrounding rock-support structure-earthquake interaction,adoption of an ADINA nonlinear finite element and construction mechanics,and transient dynamic time domain analysis of a large cross section tunnel.Results of analysis show that:(1) Horizontal earthquake acceleration has important influence on horizontal displacement,maximum principal stress,acceleration and velocity.(2) Longitudinal earthquake acceleration has important influence on longitudinal displacement,effective stress,maximum and minimum principal stress,maximum shear stress,acceleration and velocity.(3) When Ya=0.191g and 0.440g or Za=0.141g and their combined action,the initial support of tunnel would be damaged and the local lining would have partial damage.(4) When Ya=0.440g or Za=0.326g and their combined action,the lining of tunnel would be damaged.(5) When Ya=0.880g or l Za=0.652g,the support structure of tunnel would have severe damage.     

Effect of Parameters of Lead Rubber Bearings on Bilateral Seismic Response of Base-Isolated Structures

In order to investigate the influence of three main performance parameters of isolator, i.e. equivalent horizontal stiffness Kf, pre-yield stiffness K1 and yield force Qd, on the bilateral seismic response of base-isolated structures with different site condition, eighteen base-isolated structures different between Kf、K1 or Qd were designed. Based on SAP2000, the bilateral seismic responses of each isolated structure excited by four seismic waves of different site types are analyzed respectively. It is found that, the acceleration response and the base shear response of base isolated buildings under bilateral seismic excitation are influenced remarkably by the aforementioned isolator parameters, and the effect of the parameters on the isolation layer’s displacement response varies from different site conditions. Under the condition of Ⅰ、Ⅱ、Ⅲ site classified in Chinese seismic code, both the top floor’s maximum acceleration and the maximum base shear of base isolated structure show an obvious increase trend with the increasing of Kf,K1 and Qd, However, the isolation layer’s maximum deformation does not change evidently. Under the condition of Ⅳ sites, the effect of isolator parameters on the isolation layer’s maximum deformation is significant and represents obvious regularity. As Kf,K1 and Qd increases, the peak deformation value of isolation layer decreases sharply with the biggest decline of above 80%.     

福州春季塑料大棚内土壤温度日变化特征及其对棚内气温的响应

利用2014年春季在塑料大棚内不同深度的土壤温度数据,分析了各层土壤温度的日变化特征及其对气温的响应。结果表明:(1)晴天塑料大棚内气温和土壤温度均呈正弦曲线日变化。10 cm土壤温度日变化幅度最大,越往深层,土壤温度日变化幅度越小,位相越后,周期越长。(2)阴雨天塑料大棚内气温和10 cm土壤温度日变化呈单峰曲线,除10 cm土壤温度日变化幅度较大外,其余各层土壤温度日变化不明显。(3)不管晴天还是阴雨天,气温日变化幅度均大于土壤各层日变化幅度。晴天塑料大棚内气温及土壤温度的日振幅分别大于阴雨天对应的各层日振幅。     

栽培因素对甘蓝型优质杂交油菜品质性状的影响

为了研究播期、密度、施氮量、施磷量、施钾量5个主要栽培因素对甘蓝型优质杂交油菜品质性状的影响,以‘油研599’和‘三北98’为材料,运用五元二次正交旋转组合设计进行试验研究。结果表明,芥酸含量与播期、施氮量间均呈负相关,与密度呈正相关;硫苷含量与播期呈负相关、与施钾量呈正相关;含油率与播期、施氮量间均呈负相关,与密度、施钾量呈正相关;种子蛋白质含量与播期、施氮量间均呈正相关,与密度、施钾量呈负相关;油酸含量与施磷量呈负相关,与施氮量呈正相关;棕榈酸含量与施钾量呈负相关,与‘油研599’的播期、密度、施氮量、施磷量均呈正相关,与‘三北98’的播期、密度、施氮量、施磷量均呈负相关;硬脂酸含量与播期、密度、施磷量、施钾量间均呈正相关;亚油酸含量与密度、施氮量呈正相关,与施钾量呈负相关;亚麻酸含量与施氮量、施钾量呈正相关;廿碳烯酸含量与播期呈负相关。栽培因素对品质性状的影响有的呈相关,有的呈负相关,正负相关会发生部份相互抵消,每一个处理品质性状的表现都是5个因素综合作用的结果。在5个因素与10个品质性状的50对简单相关中,有26对在2个品种中表现一致,有24对在2个品种中表现不一致。播期、密度、施氮量、施磷量4因素对2个品种芥酸含量的影响较大、播期、密度、施氮量、施钾量4个因素对2个品种棕榈酸含量的影响较小。多个栽培因素的综合作用不能根本性的改善杂交油菜的品质性状。     

Change of Expected Response to Multitrait Selection in a Synthetic Population of Perennial Ryegrass Through Recurrent Selection

The changes in genetic parameters, variances, covariances and heritabilities, caused by the Bulmer effect have been predicted for an artificial breeding population of perennial ryegrass using recursion formulae. This enabled anticipation of the decrease in the expected response to multitrait index selection, using two different sets of economic weights. This theoretical decrease in selection efficiency was found to be quite substantial; it is approximately halved after 4 cycles of individual recurrent selection with a fairly high selection intensity of 5 %. However the synthetic population is improved for 4 out of 5 agronomic traits and could theoretically reach quite a high level of performance after 5 cyles. The choice of economic weights has relatively little influence on the expected genetic progress of each trait.