Lateral impact response for prestressed concrete girder bridges with intermediate diaphragms
Is Version Of
Bridge engineers are concerned with the impact damage produced by an over-height vehicle striking the girders of a prestressed concrete (PC) girder bridge. When a bridge is struck by an over-height vehicle, usually the exterior and in some instances one or more of the remaining girders are damaged. The effect of intermediate diaphragms in providing damage protection to the PC girders is not clearly understood. This thesis discusses an analytical study that evaluates the degree of damage protection provided by intermediate diaphragms in PC girder bridges. Also, the study investigated whether a steel intermediate diaphragm would essentially provide the same degree of demage protection as that provided by a particular RC diaphragm. This investigation includes several tasks. The first task was a literature search and a survey of the states departments of transportation to determine the state-of-the-art in the use and design of intermediate diaphragms for resisting lateral impact loads. The second task was a finite-element calibration study that involved strains and displacements of previously documented experimental work and those results predicted by a finite-element analysis. The third task involved finite-element models that were developed for a non-skewed bridge and a skewed bridge. Each model was analyzed with either one RC or two different types of steel intermediate diaphragms. The bridge models were analyzed for a lateral impact load applied at different locations along the bottom flange of an exterior girder. A comparison was made between the induced strains and displacements in the girders for each diaphragm case. This study revealed that intermediate diaphragms have an effect on reducing girder damage in PC girder bridges. When a lateral impact load was applied at a diaphragm location, the RC diaphragm provided more damage protection for the girders than that provided by either of the two selected steel diaphragms. The three types of diaphragms studied essentially provided the same degree of damage protection when a lateral impact load was applied away from a diaphragm location.