This study investigates the feasibility of eliminating end blocks from pretensioned continuous bridge girders. The removal of end blocks is estimated to reduce girder cost by 5 to 10%. The girders studied are the Washington State Department of Transportation (WSDOT) Series 14 type, which are characterised by 5-in.-thick webs. Previous research has recommended the elimination of end blocks for simple span bridges. A controlled laboratory test on two 20-ft-long Series 14 girders is performed. The girders are without end blocks and continuous throughout the deck. Their joint details are similar to those normally used in the field. At the continuous end, strains induced in the stirrups are monitored during the detensioning process and during various stages of loading. The load is applied at a distance of 13 ft 10 in. from the continuous end. The limiting load at which the flexural steel yielded is 408 kips. The maximum applied load is 480 kips, which is 54% higher than the ultimate design shear of 325 kips. At ultimate design shear, the deflection of the free end is 1.2 in. Even though the nominal strength of the concrete in the diaphragm is less than that of the girder, the cracks have been restricted to the girders. The maximum 28-day compressive strength of the concrete in the diaphragm is 4,000 psi, as compared to the 9,880 psi of the girders. It is concluded that the modified girders perform effectively under applied loads and hence warrant the removal of end blocks.
Samenvatting