經濟性을 고려한 桁橋의 徑間算定 = Economical Span Lengths of Girder Bridges: A Generalized Formula

다국어 초록 (Multilingual Abstract)

Employing an extended number of relevant factors, a generalized formula is derived that defines the economical span lengths of given girder bridges:

where C: Portion of cost per span of the superstructure regarded independent of span lengths, such as the cost of bearings and expansion joints
P: Cost per site of foundation works, including a well or piles(if any) and a pier
r : Unit cost of variable components of the superstructure, such as the cost (material, fabrication and handling) of concrete, steel, form and tendons
c : Constants comprising a set of linear equation ) that approximate the quantities of variable components
m: Number of variables
The values of the factors appearing in the formula can be readily obtained: C and P from a trial design using a proposed (preliminary) span length and the current unit costs r , and a matrix of a by least-square fitting the variations of variables with regard to span lengths using the data from three or more of existing (if available) or trial designs of similar design characteristics and different span lengths.
Where a design even of a multiple-span bridge of considerable length is summarily developed around a randomly chosen type and span length and "finalized" with no serious efforts made at comparative cost analyses involving the potential alternatives of different types and span lengths, the generalized formula as herein introduced (and applied to sample, modified real-life designs) will hopefully serve the designers and analysts alike.