Optimum Cost Design Research Articles

OPTIMUM COST DESIGN OF R. C. ONE WAY SLABS

In this research , the formulation of optimum cost design for one way reinforced concrete slabs is presented , since it is useful and have a widespread usage among practicing engineering and applied to realistic structures subjected to the actual constraints of commonly used design codes such as the American concrete instituted code (ACI,2005). The formulation contains minimizing an objective function that represent the cost of steel reinforcement and the cost of concrete , which is subjected to many constraints containing : flexural constraints , serviceability constraints and deflection constraints that illustrated with details in this paper . the optimum solution is calculated using the lagrangian multipliers method , and a visual basic computer software were developed to find the optimum solution . Key Words: Optimization , Lagrangian Multiplayer , Optimum Cost Design . One way Slabs .

Optimum cost design of steel box-girder by varying plate thickness

In recent years, steel box-girders have been used extensively and especially for long span due to its high torsional rigidity and rapid erection. In order to decrease the amount of costly steel material, the variations in thickness of web, top flange and bottom flange are always considered in cross sectional design. This design depends on the notable changing of the moment distribution along the length. Variation in plate thicknesses may represent a girder with the least weight; however, this may not be the most economical girder due to the increase in fabrication costs, which are associated with excessive variations in plate thicknesses. A parametric study is carried out to determine the optimum cost design of changing thickness of continuous beam over equal span. The objective function includes material and welding fabrication cost. The parameters varied are the length of span, the loading and the number of segments in each span. Both closed rectangular and open trapezoidal sections are considered. Finally, the relationship between cross-section dimensions of steel box girders is defined. The recommended design guidelines can be useful to the designer in the first stage of the designing procedure when he faces the problem of defining basic structure dimensions that would be close to the optimum ones.

Optimum cost design of reinforced concrete slabs using neural dynamics model

For structural optimization algorithms to find widespread usage among practicing engineering they must be formulated as cost optimization and applied to realistic structures subjected to the actual constraints of commonly used design codes such as the ACI code. In this article, a general formulation is presented for cost optimization of single- and multiple-span RC slabs with various end conditions (simply supported, one end continuous, both ends continuous, and cantilever) subjected to all the constraints of the ACI code. The problem is formulated as a mixed integer-discrete variable optimization problem with three design variables: thickness of slab, steel bar diameter, and bar spacing. The solution is obtained in two stages. In the first stage, the neural dynamics model of Adeli and Park is used to obtain an optimum solution assuming continuous variables. Next, the problem is formulated as a mixed integer-discrete optimization problem and solved using a perturbation technique in order to find practical values for the design variables. Practicality, robustness, and excellent convergence properties of the algorithm are demonstrated by application to four examples.

Optimum cost design of welded box beams with longitudinal stiffeners using advanced backtrack method

The use of longitudinal stiffeners in box girders loaded in bending results in savings in weight and cost. To study these savings the optimized box beams without and with stiffeners are compared to each other. The minimum cross-sectional area design can be solved analytically. A cost function is defined containing material and fabrication (welding) costs. This function is nonlinear in the structural dimensions to be optimized, therefore an advanced backtrack method is worked out and applied. An illustrative numerical example shows the savings.

Cost Optimization of Stiffened Panels Using VICONOPT

A novel and versatile optimum-cost design approach that embraces the ideology of concurrent engineering is described. The approach is incorporated into optimum-design software to permit the determination of the least-cost design for prismatic assemblies of laminated composite plates, which occur in advanced aerospace construction. Comparisons between cost and mass optimum designs of different panel topologies for two proposed manufacturing processes are presented. The different panel topologies were obtained by varying the number of stiffeners and by using either blade or T stiffeners. In total, 40 different panels were optimized separately for manufacturing cost, mass, and total cost, i.e., including running costs. The running costs were included by associating a penalty function with the mass of the panels. The results show that the approach is extremely versatile and enables different topologies and manufacturing processes to be compared in detail.

Optimum Cost Design of Partially Composite Steel Beams Using LRFD

Design of composite steel beams is a trial and error process. The procedure recommended by the Manual of Steel Construction, Load and Resistance Factor Design (LRFD)1 is to first assume a depth for the steel beam and then compute a trial beam size. For a full composite action the number of shear studs is chosen with the assumption that the plastic neutral axis (PNA) is in the concrete slab. For partially composite design the number of shear studs is chosen rather arbitrarily by the designer. The flexural capacity of the composite section is then computed based on the ultimate stress distribution over the cross section. If the capacity is less than the required, the design is revised in one of several ways: by increasing the number of shear studs, by increasing the beam depth, or by choosing a heavier section. These decisions must be based on the designers judgment without any available guidelines. Shear and deflection considerations may force additional changes in the design. The resulting design is usually not the minimum cost design and at best is a feasible design. Several iterations of this entire process may be necessary if the goal is to minimize the cost. The optimum design can directly be obtained by formulating the problem as a nonlinear optimization problem. However conventional methods for solution of these nonlinear programming problems are iterative and require large computer resources.

The optimization of NbTi-Nb/sub 3/Sn high field superconducting magnet used for physics experiments

An approach to optimum-cost design of a multigraded NbTi-Nb/sub 3/Sn high-field superconducting magnet is proposed. Investigation shows that by reasonable choice of the contribution of NbTi and Nb/sub 3/Sn coils to the central field and by properly increasing the beta of both, an optimum-cost design of the NbTi-Nb/sub 3/Sn solenoid magnet can be obtained. As an example, a calculation of a 14-T three-graded NbTi-Nb/sub 3/Sn superconducting magnet with a bore of 31-mm diameter is given.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Minimum cost design of concrete beams with a reliability-based constraint

The optimum cost design of under-reinforced concrete beams is considered by treating all the design parameters as random variables. The design is considered to be safe and adequate if the expected moment capacity of the beam exceeds the design moment capacity by a certain number of standard deviations. The optimum cost design problem is cast as a nonlinear mathematical programming problem and is solved as a sequence of unconstrained minimization problems. Numerical examples are presented to illustrate the effectiveness of the method. The resulting computer program is used to examine the characteristics of optimum designs as effected by changes in the cost coefficients and the design parameters.