EXPERIMENTAL STUDY ON FLEXURAL PROPERTIES FOR SEGMENTAL PRECAST GIRDERS OF ULTRA-HIGH PERFORMANCE CONCRETE

In order to study the flexural properties for segmental pracast girders of prestressed ultra-high performance concrete (HHPC), 5 test girders were completed, and the study parameters were mainly with or without joints, tenon forms and compressive prestress of UHPC. The failure modes, stress increments of steel strands in the tensive zones, load-deflection curves and strain development laws of the test girders were obtained. The test results showed that all the test girders presented typical flexural failure, and the UHPC in the compression zone was crushed. In the damage case, the maximum compressive strain at the compression edge could reach more than 7.2×10^-3, and the strain along the section height basically met the plane-section assumption and had nothing to do with the joints. Moreover, different from the cracking characteristics of integal casting girders, the cracks of the segmental precast girders mainly occured in the joint. The UHPC girders had good ductility, and segmental precast girders had better ductility than integal casting girders. The prestress influenced the cracking load of the girders but it had little effect on the ultimate load. The flexural capacity of the precast girders were 9% to 15% lower than that of the integal casting girders subjeted to the same compressive prestress, and the forms of joints also influenced the flexural bearing capacity. The bearing capacity of girders with multi-tenon joints was 4.5% lower than that with the single-tenon joint, and the bearing capacity of the flat-tenon members was 5.7% lower than that with the multi-tenon joint. Based on the experimental analysis, it was found that the reduction factor for joints proposed by the AASHTO specification for segmental girder design was basically suitable for the UHPC precast segmental girders, but the reduction coefficient should further considered the type of joint.