Optimization of parabolic steel box arches.

Abstract

A generalized optimization procedure has ben formulated and coded into the computer to find the least-weight design of a parabolic box-shaped steel arch of variable corss section subjected to a set of constraints, imposed by geometrical, strength and practical requirements. The strength reqquirements of AISC specifications have been followed. The web is considered to have a smooth profile. The flange areas are varied on the basis of a preassigned number of cut-off points. The iterative search procedure which incorporates dynamic programming and curve smoothening subroutines yield an optimum design within the prescribed constraints.

The applicability of the developed optimization program has been demonstrated with several illustrative examples, which also provide some interesting observations with regard to optimum design. A parametric study realted to rise to span ratio, span length, load intensities and web plate thickness is carried out through several examples. The sensitivity of a parabolic arch to the two important design variables, the span to rise ratio and the web thickness, is investigated.