ISSN:0253-3839    

DOI:10.1080/02533839.1988.9677093

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

An experimental and analytical study of the shear‐friction strength in orthogonally reinforced concrete with tension acting across the shear plane is presented in this paper. The parameters included in this study are the strength of the concrete, the magnitude of the tensile stress acting across the shear plane, the spacing of the orthogonal array of reinforcement and the angle of the shear plane to the orthogonal array of reinforcement. Based on test results in this study and results obtained by Hofbeck [3], Lin [4], Mattock [6–9] and Wu [11], the design equations in ACI Code [2], PCI Design Handbook [10] and Ref. [7] are modified to predict the shear‐friction strength of concrete reinforced with an orthogonal array of reinforcement.

ISSN:0253-3839    

DOI:10.1080/02533839.1988.9677094

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Determining and modeling of the extent of a treatment process in a reactor require knowledge of the flow characteristics. Residence time distribution (RTD), hydrodynamic dispersion coefficients, and velocity distribution are three important terms. Velocity distribution can be measured by a laser doppler anemometer (LDA) accurately, but RTD and hydrodynamic dispersion coefficients must be analyzed by mathematical modeling and dye testing. In this paper, the mathematical modeling and numerical simulation of a upflow reactor are developed. Rhodamine B and a fluorometer are used in laboratory testing. By applying the Euler FTCS (forward‐time‐center‐space) finite‐difference method, the results of dye tests and convection‐dispersion models are compared. The relationship between hydro‐dynamic dispersion coefficients and flow rates is discussed.

ISSN:0253-3839    

DOI:10.1080/02533839.1988.9677095

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The responses of transient wave propagation in a single dipping layered medium overlaying a half space was investigated in this study. To obtain the responses, a point source located in the dipping layered medium was assumed, and in order to make the results more consistent with real situations, the time functions for source mechanism, such as parabolic ramp function and triangular time function, were considered in this research. Finally, the famous mathematical tool with physical significance, the generalized ray theory [4], was employed to solve the foregoing problem, and the ray paths and responses for the distinct locations on the surface were then obtained and shown in sketches. It was found from the obtained results that the responses decay with the distance from the focus just as expected.

ISSN:0253-3839    

DOI:10.1080/02533839.1988.9677096

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The dynamic impedance of a pile or caisson foundation embedded in a homogeneous visco elastic half‐space was evaluated using the hybrid method. The soil‐foundation system is partitioned into a near‐field and a far‐field by choosing a cylindrical interface passing through the soil region very close to the foundation. The near‐field is modeled by the finite element method while the far‐field is characterized by a frequency‐dependent impedance matrix through the continuum approach. From the results presented, it is shown that the proposed method is very effective and can be widely used for parameter studies in engineering applications.

ISSN:0253-3839    

DOI:10.1080/02533839.1988.9677097

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The present study develops a method called the energy equal partitioning method. This method divides all the solid angles of a radiating source properly so that the energy carried by the beams within each small range of the solid angle are equal. The fraction of energy beams arriving at the wall surface is then examined to obtain the shape factor. This method can be efficiently applied to complex geometries. Comparing the rate of convergence and the cost of computing time shows that the shape factor obtained by the present method is better than that obtained by the Monte Carlo method. The influence of the geometric configuration on the accuracy of the shape factor is also investigated. The shape factor obtained by this method is modified by using the original shape factor as a weighting factor. An iteration procedure is developed. The resulting shape factors satisfy the reciprocity law and energy conservation law and the degree of closeness to the exact shape factors is found to be better.

ISSN:0253-3839    

DOI:10.1080/02533839.1988.9677098

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Rigid‐viscoplastic finite element equations are used for the analysis of metal forming process. With the view of solution accuracy and computation efficiency, the possible overconstraint of the incompressibility condition is avoided by modifying the penalty method in the variational formulation; and both the direct iterative method and Newton‐Raphson iterative method are combined to solve the finite element equations. The forging process of a ball from a cylindrical workpiece is completely simulated by a remesh procedure. The computed results agree well with the experimental measurements. It is shown, during the early stage of plastic deformation, the effect of friction is small, but gradually increases with further plastic deformation. In the finishing stage, the shear plastic deformation is found mainly in the flash portion. As the shape factor of workpiece increases, the filling of the die cavity is more complete, but the required forming energy increases and the variation of microstructure within the final forged product is intensified. The effect of die velocity also improves die cavity filling.

ISSN:0253-3839    

DOI:10.1080/02533839.1988.9677099

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

In this paper we investigate the stresses and displacements around an advancing face of a tunnel in an elastic half‐space as well as the induced three‐dimensional ground surface subsidence. An indirect boundary integral formulation for the analysis of tunnels in an elastic half‐space is derived and the half‐space fundamental solution (Mindlin's solution) is adopted to satisfy the traction‐free condition on the ground surface. For the evaluation of the non‐singular integral in the numerical implementation, a simple and efficient algorithm to automatically search for integration orders is developed by basing on the upper bound of error in Gaussian quadrature. Numerical results for some tunnel problems are studied to demonstrate the accuracy and versatility of the proposed method. In addition, the stresses, displacements, and the induced ground surface subsidence for an advancing circular tunnel in an elastic half‐space are calculated and presented in detail.

ISSN:0253-3839    

DOI:10.1080/02533839.1988.9677100

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Recently, the problem of analysis and optimal control of discrete time‐invariant systems has been extensively studied using finite series expansion of discrete orthogonal polynomials. This paper is to extend the applicable scope of discrete orthogonal polynomials to discrete time‐varying systems. The finite set of Hahn polynomials {qik)],i=0, 1, …,N} is chosen as the finite series expansion basis due to its general form and useful properties. First, for treating the product of two discrete‐time functions by Hahn series expansion, a new algorithm is derived to compute the Hahn series expansion coefficients of productsqi(k)qj(k),i, j=0, 1, …,N. These Hahn coefficients are then used to establish a product operational matrix for relating the Hahn coefficient vector of a product function to those of its component functions. This product operational matrix, along with the relations for connecting the Hahn coefficient vectors of a discrete functionx(k) and its time‐shiftedx(k+1), is finally applied to derive computational algorithms for solving the problems of analysis and optimal control of discrete time‐varying systems via finite Hahn series. Computed results are provided to illustrate the applicability of the proposed algorithms.

ISSN:0253-3839    

DOI:10.1080/02533839.1988.9677101

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

In order to assure safety and serviceability, structural responses are kept within certain limits by active control methods. Control forces as well as responses (displacement and velocity) are considered constraints in an optimal control system. The exact solution of the optimal control system under the aforementioned constraints is derived in the first part of the paper. An approximate solution is also suggested in the paper. An example dealing with a six‐story building is presented in the last part of the paper to demonstrate the application of the approximate approach.

ISSN:0253-3839    

DOI:10.1080/02533839.1988.9677102

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor