The conventional
preflex beams are based on the method of partial prestressing, and allow the tensile
stresses
at the lower concrete of beams. As a consequence, many preflex beams
experience the tensile cracks under the service loads. Introducing additional
prestressing called ’represtressing’ at the lower concrete of beams, there
could be accomplished control of crack problem. For analysis and design of
experiment and improved beam, Design and Analysis Program of
Represtressed Preflexional Composite Beam (DARP), was developed. In the experiment, two actual
sizes of represtressed beams were tested under the imitated service loads. The
results of test have shown that the performance of the represtressed preflex
beams(RPF) are generally excellent for straight simple beams. Although RPF do
not experience the tensile cracks under the service loads, the use of this beam
for the bridge structures couldn’t apply for skewed
bridges. Therefore, newly
invented box-type bridge, Represtressed Preflex - Box Girder Composite
Bridges(RP-Box Girder Bridges) are suggested for the skewed or long span
continuous bridges. Adding the characteristic of low beam depth, high clearance
and economical design of RPF, this suggestion of RP-Box Girder Bridges, is
expected to contribute to practical and economic construction of bridges.