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排序方式: 共有810条查询结果,搜索用时 15 毫秒
1.
提出一种基于BP神经网络的结构破损诊断方法,该方法以结构破损前后柔度的变化作为破损诊断网络输入,为了解决由于系统响应样本数据空间分布不均匀对网络收敛速度及网络诊断影响问题,对网络训练样本采用广义空间格点进行了交换,模拟算例及应用实例均表明,本文方法能准确诊断结构破损位置与破坏程度,是一种有效的结构破损诊断方法. 相似文献
2.
3.
A novel method for prediction of the load carrying capacity of a corroded reinforced concrete beam (CRCB) is presented in the paper. Nine reinforced concrete beams, which had been working in an aggressive environment for more than 10 years, were tested in the laboratory. Comprehensive tests, including flexural test, strength test for corroded concrete and rusty rebar, and pullout test for bond strength between concrete and rebar, were condueted. The flexural test results of CRCBs reveal that the distribution of surface cracks on the beams shows a fractal behavior. The relationship between the fractal dimensions and mechanical properties of CRCBs is then studied. A prediction model based on artificial neural network (ANN) is established by the use of the fractal dimension as the corrosion index, together with the basic intbrmation of the beam. The validity of the prediction model is demonstrated through the experimental data, and satisfactory resuits are achieved. 相似文献
4.
Priti Maheshwari P. K. Basudhar S. Chandra 《Geotechnical and Geological Engineering》2006,24(2):313-324
The paper describes a mechanical model for estimating the flexural response of a strip footing, supporting a column (imposing
a concentrated load), resting on a compacted granular bed overlying a reinforcement layer for example, geogrids, geomats etc.
below which lies a loose soil deposit. The footing is idealized as a beam and the reinforcing element is assumed to have finite
bending stiffness and negligible frictional resistance. The upper and lower soil layers are idealized by a series of linear
and discrete springs (Winkler springs) of different stiffness values. To find the response of such a model the governing differential
equations have been derived and expressed in a nondimensional form. A closed form analytical solution of the same has been
obtained subjected to appropriate boundary conditions. Using the present approach the resulting solution for a degenerated
case of a long beam is found to be identical to the same of Hetenyi (1946, Beams on elastic foundations, University of Michigan
press, Ann Arbor, MI). Parametric studies reveal that the ratio of flexural rigidity of upper and lower beam and the ratio
of stiffness of the upper and lower soil layers affect significantly the response of the foundation. 相似文献
5.
Abdullah Al-Khanbashi Shihab W. Abdalla 《Geotechnical and Geological Engineering》2006,24(6):1603-1625
This study reports on waterborne polymer emulsion systems that were used for structural modification of sandy soils. The first
emulsion used was a styrene-acrylic, copolymer emulsion; the second and third were vinyl-acrylic, copolymer-based emulsions.
Specimens were prepared by adding different polymer emulsions to the sand and water in prescribed amounts. The performance
of the different emulsion systems as sand stabilizers was estimated through measurement of the hydraulic conductivity and
compressive strength. Measurements of hydraulic conductivity were conducted in a flexible membrane test apparatus. The hydraulic
conductivity for the three emulsions decreased at different rates, with an increase in polymer content up to 3 wt. (i.e.,
% by weight). Additional increase of polymer content did not introduce significant decrease in hydraulic conductivity, and,
at 5 wt.%, the three emulsions had essentially the same effect. Measurements made on dry cylindrical specimens disclosed remarkable
enhancement in the mechanical behavior of the system. The compressive strength and modulus of elasticity of the examined emulsions
increased with a higher concentration of polymer. Scanning electron microscope (SEM) revealed that the reduction in the permeability
and the improved mechanical properties can be attributed to three dominant structural changes: the development of interconnecting
ties between the sand particles, the development of adhesion between neighboring sand particles in contact, and the covering
of the sand particles with a thin polymer film. 相似文献
6.
JoAnn Browning 《地震工程与结构动力学》2002,31(6):1267-1280
A maximum allowable period criterion is used to determine reasonable stiffness requirements for reinforced concrete frames with the seismicity associated with central and eastern U.S. A general relationship is developed to describe the displacement demand expected for central and eastern U.S. based on a survey of available ground motions, opinions of seismologists, and code‐based provisions. A series of hypothetical reinforced concrete frames is proportioned using a maximum allowable period criterion and evaluated for expected maximum displacement response using non‐linear dynamic analyses and a suite of ground motions. Results indicate that for the reinforced concrete structural systems considered in the study, proportioning for gravity loads will provide sufficient stiffness in central and eastern U.S. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
7.
Most current methods of design for concrete structures under earthquake loads rely on highly idealized ‘equivalent’ static representations of the seismic loads and linear‐elastic methods of structural analysis. With the continuing development of non‐linear methods of dynamic analysis for the overload behaviour and collapse of complete concrete structures, a more direct and more accurate design procedure becomes possible which considers conditions at system collapse. This paper describes an evaluation procedure that uses non‐linear dynamic collapse–load analysis together with global safety coefficients. A back‐calibration procedure for evaluating the global safety coefficients is also described. The aim of this paper is to open up discussion of alternative methods of design with improved accuracy which are necessary to move towards a direct collapse–load method of design. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
8.
考虑轴向变形、双轴弯曲耦合效应的钢筋混凝土柱的弹塑性分析 总被引:6,自引:2,他引:6
在实际地震作用下,高层,特别是高宽比较大的高层结构中,由于倾覆力矩的作用、柱子、特别是外边柱所受轴力的变化将不可忽略。轴向变形与双轴弯曲的耦合作用,将是柱子塑性变形的显著特征。基于材料本构关系的“纤维模型”,能较精确地反映轴向变形,双轴弯曲三者之间的耦合作用。一组钢筋混凝土柱子双轴压弯的计算结果与试验结果的比较,证明了“纤维模型”的有效性和精确性。 相似文献
9.
Introduction Greeting the coming of the 21st century, Professor HU Yu-xian and other Chinese scholars briefed the trend of earthquake engineering in China and aboard (HU, 1999; HU, ZHOU, 1999). The experiences and lessons learning from the destructive earthquakes in China and abroad in re-cent years, the damage action of the large velocity impulse in ground motion in near field in seis-mic design, numerous earthquake examples show that there are many weaknesses in aspects of earthquake p… 相似文献
10.
This paper proposes a simple lattice model for collapse analysis of RC bridges subjected to earthquakes by using the extended distinct element method (EDEM). In the model, a concrete element consists of lumped masses connected to one another by springs, and a reinforcement bar is represented by a discrete model or an integrated model. The proposed lattice model is simple but its parameters are reasonably defined. It has fewer element nodes and connecting springs, which will be of benefit by shortening the CPU time. The processes to determine the initial stiffness of concrete and steel springs, the parameters of the constitutive model and the fracture criteria for springs are described. A re‐contact spring model is also proposed to simulate the re‐contact of the concrete after fracture of springs; and a general grid searching method is used to decrease the CPU time for judging re‐contact after fracture. The lattice model is assessed by numerical simulations and experiments. As an application, a damaged single‐column pier subjected to the Kobe Earthquake in 1995 is analysed by EDEM with the proposed model. The simulation results indicate that the proposed model predicts well qualitatively the collapse process of RC bridges. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献