共查询到20条相似文献，搜索用时 31 毫秒
1.
Aiming at the lack of the current determination method for voids in practical engineering applications, in order to accurately quantify the voids beneath cement slab, the determination method was proposed with slab edge slab center deflection difference and slab corner slab center deflection difference in the same cement slab for voids.Three dimensional models were set up using the ANSYS finite element method for voids beneath slab corner and slab edge.And the load was simulated with FWD test results.Thereafter, the deflection values were calculated in slab center, slab corner, slab edge under different void depth, void area and load transfer capacity.And the range of deflection diffidence was obtained.With Yantai Weihai expressway, detection data for deflection using Falling Weight Deflectometer were statistically analyzed.And the criteria and correction factors of load transfer capacity were given with simulation and samples analysis.The feasibility of criteria was verified by actual test data.It is found that the simulation values and the test values are in good agreement.The accuracy of void determination by lab edge slab center deflection difference and slab corner slab center deflection difference are 88.5% and 84.6%, respectively, which meet the engineering requirements.The voids were determined under the same conditions with the elimination of deflection variability. 相似文献
2.
Operational Deflection Shapes of large scale electromechanical system can be ex-tracted directly from multipoints response of the operating system by using of the modal shape analy-sis method. Thev can be used for engineers evaluating the practical dynamic beavior of the largescale elecltromechanical system,checking the existence of local reso,iance of the Stibsystem. and in-dentifying the wcakened positions of the rigidity of structure, In this paper the method of measuringand extracting the operational deflection shal1e of the electromecha nical system is given and theavailability of operational deflection shape is proved by analyzing the actual vibration of a large ex-haust fan system as an example. 相似文献
3.
Zhang Jianhui Deng Anfu 《保鲜与加工》1999,(2):84
The application of the element-free method in the bending problems of plates has not been found since it was proposed.In this paper,the element-free method is applied to compute the deflection and the moment of the elastic foundation plate with free boundary,and the corresponding formulas as well as the computer program are developed.Numerical examples show that the accuracy of the method used in the foundation plate problem is satisfactory.Therefore,it is reasonable and feasible for using the element-free method in the plate bending problems. 相似文献
4.
Deflection is one of the most important parameters in process of evaluating bridge's safety and developing structural health monitoring.The basic principles,characteristics and applied field of different sensing technologies in bridge deflection automatic monitoring are analyzed.And the corresponding measuring precision,measuring methods and applicability in different type bridges are also compared.The result shows that both high integration automatization and large scope measurement are developing directions in future. 相似文献
5.
By adopting the energy and finite-element methods with analysis software MATLAB and ANSYS,a detailed and complete solution process for bucking of simply supported rectangular elastic plates is provided.By increasing the triangular series for the deflection function,the amendments have been made to the K values given in references.Through finite element analysis,the expression of K value is fitted out.It is ascertained that the shear stress,taken as a critical shear stress,is reasonable according to the small deflection theory under limited plate deflection.The results of two analytical methods show that the fitting curve of K values used by finite element analysis has more comprehensive practical significance. 相似文献
6.
In this paper, based on the discussion of orthogonal decomposition method for the buckling mode of unsymmetrical structure, taking the variable-section beam-column as an example, a simple and direct method of the second order analysis is presented. In the new method, the conception of enlargement coefficient brought forward by Timoshenko is developed. To begin with the curvature of the variable-section beam-column, the linear equations are set up. With their solution, a group of orthogonal buckling mode can be obtained. The primary deflection can be decomposed to a group of homomorphic deflection similar to buckling mode. Then, the group of deflection is multiplied by corresponding enlargement coefficient and plus the result, finally, the second-order total deflection can be obtained. 相似文献
7.
Timber floors are by far the most common structural systems used in wood-framed residential buildings,and are the only systems with which human occupants are in constant physical contact.In dwellings,the floor vibration due to walking often brings discomfort to the occupants.Designing a house that controls the agonizing vibration of floors is a difficult problem.The vibration performance of five solid wood lumber joist floors was studied as were subjective opinions of evaluators.The 1KN static deflection and fundamental natural frequency were selected as two evaluation indexes of the vibration performance.The results show that when the ratio of the fundamental natural frequency to 1KN static deflection's 0.44 power is larger than 20,the solid wood lumber joist floor can be classiified as acceptable. 相似文献
8.
In this paper artificial neural networks are used for design of large span double layer torsional reticulated shell. The torsional reticulated shells with spans varying between 50.0 - 80.0m are considered, Back -propagation algorithm is employed for training efficient neural networks for evaluation of the maximum deflection, weight and design of double layer torsional reticulated shell. A special method is developed for data ordering to reduce the nonlinearity of data and to increase the speed of training. This approach also provides the necessary stability. It shows that it is feasible to design double layer reticulated shell with artificial neural networks. 相似文献
9.
Owing to the randomness of shrinkage and creep of concrete, random analysis method should be adopted to give a reasonable result with probabilistic guarantee. Stochastic variables for long-term analysis with GL2000 model about creep and shrinkage of concrete were presented. Combining Monte Carlo sampling with the response surface method, the stochastic analysis model was performed which is on time-variant deflection of prestressed concrete bridge. The long-term deflection of a prestressed concrete bridge was analyzed by this model. Sensitivity analysis and parametric study were carried out. And the uncertainty of creep model, elastic modulus of concrete, magnitude of sustained load, and prestress forces are the most important factors for long-term deflection. Furthermore, controlling accuracy of prestress forces and delaying the loading time are helpful to inhibit long-term deflection. 相似文献
10.
通过对全尺寸可拆式钢筋桁架模板在施工阶段的截面力学性能试验,研究了其在单调荷载作用下的破坏形态以及受力机理。并分别采用荷载挠度曲线法和极限弯矩法计算了截面特性。分析表明：施工阶段可以采用上下弦连续的桁架计算模型,荷载挠度曲线法计算结果与理论值偏差较大,其原因是：试件破坏过程由变形控制,而非强度,以及由于连接件与钢筋的相对滑移产生的附加挠度,极限弯矩法计算值与理论值较为吻合。在此基础上,给出了简支或等跨连续（两跨）梁计算模型的最大无支撑长度的建议值。 相似文献
11.
The long term deflection behavior of long span continuous rigid frame bridges has often attracted the attentions in engineering field. Based on the moisture diffusion theory, the calculation method of differential shrinkage deflection was proposed for PC box girder bridges. Finite Element Method(FEM) model of 2 D moisture field were established for typical cross sections of a case bridge. And the distribution law and the time variation characteristics of moisture field were analyzed. Through the deformation coupling condition of moisture field, the drying shrinkage deflection of the bridge was calculated and analyzed. It was found that the differential shrinkage deformation was significant and great error would be with the conventional method. When considering the effect of differential shrinkage, the deflection in mid span was 3.1cm larger than that of the conventional method. Thus, the differential shrinkage was the main reason for long term deflection of long span continuous rigid frame bridges. 相似文献
12.
To explore the vibrating frequencies and rational impact factors of multi-span skew bridge, the recursive algorithm of vibrating frequency and finite element formulations of static and dynamic analysis are established for uniform section multi-span continuous skew bridge. The first five order frequency changes of equal-span multi-span continuous skew bridge and unequal-span multi-span skew bridge are compared. The interaction of vehicle-bridge system for two-span skew bridge is analyzed. The history curves for deflection and moment of middle-span are presented. The influence of obliquity on dynamic deflection and dynamic moment as well as the influence of vehicle velocity and obliquity on impact factors of deflection and moment are investigated. Results show that the fundamental frequency of multi-span skew bridge is identical to that of single span skew bridge. The higher order frequencies of single span skew bridge are distributed in frequencies of multi-span skew bridge, which mix other vibrating frequencies. The more the span number is, the more the other vibrating frequencies mingle. Obliquity has an important influence on dynamical characteristics of skew bridge. Impact effects of vehicle have no harmonious changing rule with vehicle velocity and obliquity. The impact factors of deflection and moment are different for skew bridge. 相似文献
13.
The principle of photoelectric imaging deflection measurement system are presented. The calculation of the image plane's illuminance and contrast are discussed. The relationship among the system's parameters are analyzed. The feasibility of high reflectivital material replacing the system's source are also discussed when illuminance on the ground is high. The result contributes to selecting the parameters of photoelectric imaging deflection measurement system and achieves the long online of deflection. 相似文献
14.
Based on the established cross-anisotropic layered elastic theory,the effect of inverted asphalt pavement structure by granular cross-anisotropy is analyzed.The result shows that,with the decrease of granular horizontal elastic modulus,the pavement surface deflection and tensile strain at bottom of AC are increased,but the tensile stress at bottom of semi-rigid base and compressive strain at top of subgrade are decreased.The thickness of AC has significant effect on the pavement surface deflection,tensile strain at bottom of AC and compressive strain at top of subgrade,while the granular cross-anisotropy has little effect on the critical inverted pavement responses for the thicker AC. 相似文献
15.
Feng Xiangui 《保鲜与加工》1991,(6):111-114
The singular function is combined with Laplace' s transformation to calculate the deflection of stepwise beam. In this way the deflection equation of the beam is conveniently determined. This method is suited for both statically determinate and indeterminete stepwise beams and can simplify the calculation. 相似文献
16.
According to concrete box beam which flanges depth varying along the orientation of cross section, using variational principle of potential energy, new analysis method of shear lag is proposed for single cell concrete box beam. For simply supported girders and cantilever girders, general analysis of varying flange-depths influence on positive and negative shear-lag effect and deflection have be done. It's shown that varying flange-depths have influence both on sectional stress and deflection. Considering the varying flange-depths have effect on the calculation results of up to 15%. 相似文献
17.
Ziui JizhongXu Guoyu 《保鲜与加工》1990,(5):27-35
The calculating burden of the decoupling judgement of multi-area power system load frequeney centrel is very large by tranditional methods. This paper changcs the decoupling judgement problem into a minimum cost network flow problem. The solution algorithm is out-of-kilter . algorithm which is characterized by simple manipaultion, fast and reliable convergence. In the paper, we discuss and calculate the decoupling problem of two arca power system load frequency control. The results show that the proposed approach is feasible and effective. 相似文献
18.
Focusing on the problem of computer operation without hand for the disabled people, a new method of mouse control based on visual analysis of the face poses is proposed. First, the face images from CCD camera are obtained and the face areas are located based on AdaBoost algorithms with Haar features. Then, 5 feature points including 2 eye corners, 2 mouth corners and nose tip are detected with image analysis. After that, with help of the feature points in a predefined frontal face image, the face poses are estimated in the real-time face images. Finally, the 3 deflection angles are adopted to define human computer interactive information, which can be used to determine positions and operations of the mouse in the human computer interactive interface. The experimental results demonstrate the efficiency of our method that the face poses can be estimated accurately as well as the operation information to the mouse be achieved rapidly. It is valuable in human computer interaction for the disabled people. 相似文献
19.
The varied-axial force beam-column is widely used in practice. Unlike the academic method, the numerical method is usually used only to solve its stability problem, but not to give the general answer a series of problems for beam-column. In this paper, firstly, a new conception of dimensionless beam column is presented. Secondly, based on the column deflection curve (CDC) method, the calculation formula for critical load of variable-axial force beam-column is derived. Thirdly, the numerical results under axial symmetric load are derived. Finally, the interaction formula on the critical load of beam-column under concentrated axial load, even distributed axial load and triangular distributed axial load and under these loads acted simultaneously are proposed respectively. The method given in this paper expands the application of CDC. 相似文献
20.
Zhou Shizhen 《保鲜与加工》1996,(2):61-76
In this paper, ultimate loading capacity of eccentric compressed timber column and elastic-plastic behaviour of the material of the cross section are considered.An approximate theoretic method dealing with the maximum mid-span deflection of the column when breaking is advanced.As a result, a formula calculating failure deflection of the rectangular cross section is derived. The results of theoretic calculation are well coincident with those of tests. 相似文献