OPTIMIZATION OF PARTIALLY PRESTRESSED CONCRETE GIRDERS UNDER MULTIPLESTRENGTH AND SERVICEABILITY CRITERIA

A comprehensive study on the optimization of simply supported partiall y prestressed concrete girders is presented. Using sequential quadrati c programming a set of optimal geometrical dimensions, amounts of pres tressing and non-prestressing steel, and spacing between shear reinfor cements are obtained. The constraints used are based upon flexural str esses, fatigue stresses, crack width, ductility, initial camber, defle ction due to both dead and live loads, ultimate moment capacity of the section with respect to cracking moment and factored loads, and the u ltimate shear strength. Results point to the need for non-prestressing steel to obtain economical designs. Minor savings on the material occ ur when the section is allowed to crack. The ultimate moment capacity and the fatigue stress controlled the design in the cracked case. The tensile stress at service and the ultimate moment capacity were the bi nding constraints in the uncracked case. This study automates the desi gn of partially prestressed concrete girders and provides needed desig n solutions to problems which are of importance to practicing engineer s.