Damage detection of frames using the increment of lateral displacement change

INTRODUCTION Damage detection of structures is very importantfor ensuring and evaluating the safety of structuresystems during their lifetime. The approaches de-veloped in this field may be generally classified intodynamic identification approach using dynamic testdata and static identification approach using static testdata (Wang et al., 2001). The dynamic identificationapproach has been highly developed, although severalinherent drawbacks and problems handicap the fullutilization o…     

Experimental study of structural damage identification based on WPT and coupling NN

Too many sensors and data information in structural health monitoring system raise the problem of how to realize multi-sensor information fusion. An experiment on a three-story frame structure was conducted to obtain vibration test data in 36 damage cases. A coupling neural network (NN) based on multi-sensor information fusion is proposed to achieve identification of damage occurrence, damage localization and damage quantification, respectively. First, wavelet packet transform (WPT) is used to extract features of vibration test data from structure with different damage extent. Then, data fusion is conducted by assembling feature vectors of different type sensors. Finally, three sets of coupling NN are constructed to implement decision fusion and damage identification. The results of experimental study proved the validity and feasibility of the proposed methodology.     

Investigation of newly developed added damping and stiffness device with low yield strength steel

Energy dissipators, isolated-resistant and specific structural forms for earthquake resistance are popular topics in the research to improve shock-resistance. In this work, experimental methods were used to investigate the property of low yield strength steel. Carbon content in LYS material is lower than that in other steels; the ultimate stress is three times the yield stress. The ultimate elongation rate is about 62% and the ductility is 2–3 times that of A36 steel. In order to overcome some defects of ordinary use metallic dampers, the mechanical characteristic of low yield strength steel is used to develop added damping and stiffness for rhombic steel plate absorber. Test of the energy dissipation behavior for this newly developed device indicated that LYS could stably dissipate or absorb the input energy of earthquake. Then, the analytical model for the hysteretic behavior of this new device is proposed. Comparison of experimental data and numerical simulation results showed that this analytical model is suitable for simulating the hysteretic energy behavior of this new device.     

Optimal arrangement of viscoelastic dampers for seismic control of adjacent shear-type structures

The optimal arrangement of viscoelastic dampers (VEDs) used to link two adjacent shear-type structures under seismic excitation was investigated. A two-step optimal design method is proposed. First, optimal parameter expressions of the Kelvin model are used to calculate the optimal stiffness and damping coefficient of the VEDs. Then, using the two-step optimal design method, taking the quadratic performance index as the optimization objective, the optimal arrangement of the dampers is determined. General rules about the optimal arrangement of the VEDs were obtained. The results show that the placement of only one damper between two adjacent shear-type structures should be avoided; if more than one damper is used, they should be distributed on the top and lower floors of the structures. Optimization of the number of dampers had little effect on response reduction. The most important factor was the optimization of the placement of the dampers. Through comparative study, for buildings of equal and unequal heights, the optimal parameters of dampers from parametric studies were shown to match the theoretical results for different numbers and placements of dampers. The level of response reduction was shown to be sensitive to the damping coefficient of the dampers.     

Neuromuscular variables affecting the magnitude of force loss after eccentric exercise

The aim of this study was to examine neuromuscular variables contributing to differences in force loss after participants were exposed to the same relative bout of eccentric exercise. Thirty-six males performed 50 maximal eccentric contractions of the elbow flexors and were stratified into high responders (n?=?10) and low responders (n?=?10) based on force loss 36 h after exercise. Maximal voluntary isometric contractions (MVCs) and electromyography (EMG) were measured at baseline and 36 h after exercise. During eccentric exercise, mean peak torque, mean end-range torque from the final 25% of each trial and total angular impulse were computed over 25 contractions in each of two bouts. The slope of the change in these values for each 25 eccentric contractions was calculated for each participant using linear regression. At baseline, MVC was not different between groups (low responders: 97.0?±?9.6 N?·?m; high responders: 82.7?±?6.4 N?·?m; P?=?0.08). High responders demonstrated a 68% (range 62-78%) reduction in MVC and low responders a 39% (29-48%) reduction after exercise. Peak torque, end-range torque and total angular impulse were 13%, 40% and 33% higher, respectively, in the low than in the high responders (peak torque: P?=?0.0002; end-range torque: P?<?0.0001; total angular impulse: P?<?0.001). The rate of decline in peak torque slope was greater in high than in low responders (P?=?0.044). In conclusion, lower peak torque, end-range torque and total angular impulse during eccentric contractions and a greater peak torque slope may identify high responders to eccentric exercise.     

以高校创新能力提升为基点的研究生教学模式初探——以212程抗震原理与应用课程为例

文章以“高校创新能力提升”为基点,以工程抗震原理与应用研究生课程教学改革为例,对新形势下的研究生教学模式进行了初步探索。提出了涵盖互动式教学、案例教学、同步观摩教学、讲座教学、配套实验教学、网络数字化平台E-learning教学等内容的、新的研究生课程教学体系,以期实现研究生课程教学在“高校创新能力提升”中的功能。     

Nonlinear dynamic analysis of the Three Gorge Project powerhouse excited by pressure fluctuation

This study established a 3D finite element model for 15# hydropower house of the Three Gorges Project （TGP） and performed a nonlinear dynamic analysis under pressure fluctuation. In this numerical model, the stiffness degradation in tension for concrete was considered on the basis of the continuum isotropic damage theory. Natural vibration frequencies of the damaged and undamaged structures were compared after static water pressure was applied. Then a study was further conducted on forced vibration of the powerhouse with pre-existing damages under pressure fluctuation that acts on the flow passage; displacement, velocity and acceleration of the important structural members were afterwards presented and checked. Numerical results show that tensile damages in concrete surrounding the spiral case only exert significant impact upon the dynamic characteristics of substructure but show little effect on the superstructure. Nevertheless vibrations of the powerhouse are still under the recommended vibration limits.     

应用带血管蒂皮瓣、肌（皮）瓣治疗下肢皮肤软组织缺损26例分析

目的:探讨采用带血管蒂皮瓣、肌(皮)瓣修复下肢皮肤软组织缺损、重建功能、再造器官和改善外形的效果。方法:采用带血管蒂皮瓣、肌(皮)瓣,通过局部转移或移位,进行血管、神经吻合,覆盖因创伤造成的下肢软组织缺损。结果:本组共26例患者,一期治愈23例,治愈率88.5%;二期治愈3例,治愈率11.5%,总治愈率100%。结论:由于不同于传统的随意皮瓣,切取范围不受长宽比例限制,手术一次完成。极大可能的修复缺损的皮肤及软组织,保持患肢的长度及功能。     

浅谈小波分析在结构损伤检测中的应用

简要介绍了一维小波分析的基本原理和信号的小波消噪原理,及其在结构损伤检测诊断方面的主要应用,并引例说明小波分析可以弥补傅利叶转换的一些不足之处.