Showing papers in "Engineering Optimization in 1975"

Mathematical models for developing regional solid waste management policies

Abstract: Various mathematical programming models are applied to evaluate operational (static one-period) and dynamic investment. (multiperiod) policies of regional solid waste management (SWM). Special attention is paid to the use of mixed integer programming (MIP) models for dynamic investment policies. The common objective of minimizing the present value of overall investment and/or management costs is extended to deal explicitly with land-use policies by evaluating the sequencing of landfilling operations. The question of abandonment or upgrading of facilities is introduced into the mathematical framework because of its importance in the light of more restrictive standards. The decision as to which process should be installed at what location and at what time, as well as the decision which landfill should be operated and when, is identified in the MIP model. Considering the limitations of the data base and the model formalism, the question of the usefulness of relying on one optimal solution from a mod...

Architectural optimization-a review

Abstract: The introduction of numerical methodologies to Architecture is very recent. However, the last ten years has seen the application of optimization techniques to many of the problems of Architecture previously considered to be non-numeric: this paper reviews the panoply of these applications. The optimization problem which appears to have attracted the most attention is that of the layout of spaces or planning. Various techniques have been applied to this combinatorial problem but as yet there appears to be no algorithm available which produces a global optimum. The development of sites in cities has also been treated as an optimization problem with considerable success; various search methods as well as dynamic programming have been applied here. The methods used to control the internal physical environment of buildings (building services) have been examined systematically from an optimizing viewpoint. Detailed services such as aii-conditioning and vertical transportation have been treated. Materials select...

Optimum expansion ratio of castellated steel beams

Abstract: In this paper, the authors present a numerical analysis for the optimum expansion ratio based on the elastic as well as the plastic method of analysis. The elastic analysis program is based on an iterative process and involves the calculation of allowable loads corresponding to potentially critical flexural and shear stresses at each increment of the expansion ratio. The plastic analysis program considers three types of collapse mechanisms: (1) Vierendeel mechanism, which is caused by the formation of plastic hinges at the four reentrant corners; (2) Flexural mechanism, which occurs when the flanges of the critical panels become completely plastified; and (3) Failure caused by the yielding and rupture of a welded joint. An experimental program involving the testing of five beams expanded to different depths has confirmed the theoretical predictions.

Computational efficiency in structural optimization

Abstract: This paper investigates, using a sequential unrestrained optimization technique, the computational efficiency of unrestrained minimization algorithms. Minimization algorithms which use no derivatives, first derivatives, and first and second derivatives are used to optimize a variety of structural engineering problems. Derivatives are obtained by direct differentiation and with finite difference formulae. Conclusions are made concerning the efficiency of the finite difference formulae and of the optimization algorithms considered.

Optimum cost design of a steel-framed building

Abstract: The paper describes an investigation into the minimum cost design of a steel portal framed building. Computer programmes have been developed which permit:1)The simple “plastic” design of this type of structure in accordance with the relevant B.S. Codes and common industrial practice. 2)The costing of any “feasible” design in accordance with a cost model devised in conjunction with several members of the steelwork fabrication industry.3)The economical determination of the “least cost” design from the hyperspace of “feasible” designs.It has been assumed that the optimum shape of a structure (i.e. the specific combination of problem variables which produces the design of least cost) is a function of material and fabrication costs only. Accordingly, for any feasible design, the cost is defined as the sum of the individual material and fabrication costs for the structural steelwork, purlins and cladding. A model has been devised in which the problem has been formulated as a constrained non-linear optimization ...

Solution of some combinatorial optimization problems encountered in water resources development

Abstract: The solution of some constrained combinatorial optimization problems encountered in the preinvestment planning of large-scale water resources systems is discussed. Mathematical structures are formulated for several problems involving the optimal selection, sequencing and timing of a set of water resources development projects which, in the aggregate, must satisfy a number of continuous time demand projections at every point in a finite planning horizon. An overview of four different solution techniques is also given. Specifically, myopic decision rules, integer programming formulations, and both implicit enumeration by branch-and-bound algorithms and dynamic programming algorithms are discussed. A computational comparison of these solution techniques on a number of real-world water resources problems of various sizes is also reported.

Optimum limit state design of highway bridge superstructures using geometric programming

Abstract: A number of studies, by the author and others, have shown that the Limit State Design method can, when applied to the design of bridge superstructures, produce more rational and economic designs than conventional methods. Most studies have been made on the assumption that the basic structural layout, proportioning, and material characteristics would be determined by the rules used for conventional design. The authors have pointed out that these rules are possibly no longer applicable and that greater economies could be obtained by some form of optimization procedure. This paper describes the application of Geometric Programming to the solution of such a problem. It is shown that excellent results can be obtained with a simplified version of the technique in which the “degree of difficulty” is reduced to zero. The superiority of Geometric Programming as an optimum design technique is demonstrated by comparing the results for the example chosen with those obtained by alternative methods.

Hybrid computer optimization of a catchment simulation model

Abstract: The optimization of a two-parameter river catchment simulation model is described. The parameter K1 controls the rate of infiltration into the soil, and the second parameter, K2, is used in the routing equation. The Simplex direct search method is used and is implemented on a hybrid computer. The computer programme forms an n-dimensional “simplex” (n being the number of parameters) from initial trial values of the parameters, and uses the basic operations of reflection, expansion and contraction to find the optimum value of the objective function. The operations are carried out according to the value of the objective function at each apex of the “simplex.” The peripheral devices linked to the hybrid computer are used to give a continuous display of the optimization process, and the effects of systematically varying the parameters are studied by plotting sample hydrographs for various pairs of parameter values and by plotting the surface of the objective function.