Dynamic Analysis of Prestressed Concrete Beams with Openings

There is a growing trend in constructing multistory garages and high-rise buildings where utility ducts are passed through openings in the floor beams. Accommodating the utility services in such a manner minimizes dead space. However, introducing an opening in the web of such beams reduces the beam stiffness and leads to a more complicated structural response. In this paper the dynamic analysis and design of simply supported and continuous prestressed concrete beams with rectangular openings are presented. Several design parameters are varied such as opening width and depth, horizontal and vertical locations of the opening, type of cross section, and presence of more than one opening. The analytical results were compared to test results in the literature. Good agreement was shown between the theoretical and the experimental results. An extensive parametric study was performed on prestressed beams with openings to determine the natural frequencies and the associated mode shapes. Simple methods are proposed to predict the dynamic response including the beam maximum deflection, deflection of the opening chords, and horizontal and vertical stresses at midspan and at the vicinity of the opening.