June 14, 2015
June 14, 2015
June 17, 2015
26.959.1 - 26.959.9
Influence of Boundary Conditions on Building BehaviorWhen architectural engineering students graduate and enter the workforce they will be facedwith analyzing and designing a variety of structural systems. Often times great care is taken inaccurately representing the structural members until it comes to the boundary conditions at thebase of the building. Most students are exposed to fixed boundary conditions, pinned boundaryconditions and roller boundary conditions in their undergraduate courses. These idealizedboundary conditions simplify the analysis, however, choosing which condition is appropriate foran actual building is not always clear. In addition, building boundary conditions can have a largeinfluence on the predicted building performance and associated design. Engineers arechallenged with accurately modeling buildings including the boundary conditions and, therefore,facing this challenge in their undergraduate studies is important for students so that they canmake informed decisions as engineers.In order to expose students to the challenges of accurately modeling boundary conditions,students were asked to determine the appropriate boundary conditions for a nine foot tall two-story steel wide-flange moment frame with the columns bolted to a concrete floor through a steelbase plate. The students predicted the steel frame response by computational models and handcalculations. Students were encouraged to complete the hand calculations first to provide abaseline for the computational models. After predicting the steel frame response the studentsconducted dynamic experiments to measure the actual response of the frame. Since the frame isrelatively simple to model the difference between the student predictions and the experimentalresults were almost entirely due to the behavior/modeling of the boundary conditions. Prior toany experimentation 80% of the students considered a fixed base boundary condition to beappropriate while 20% of the students considered a pinned base boundary condition to beappropriate. Once the structure was dynamically excited by the students, the students discoveredthat the boundary conditions were somewhere between a fixed base and a pinned base boundarycondition and that the boundary conditions were different in the column strong axis direction andthe column weak axis direction.The students enjoyed the opportunity to compare their predictions of the steel frame response tothe dynamic experimentation results. In addition, this exercise challenged students to check theircomputer analysis results with quick hand calculations as well as consider how to appropriatelymodel boundary conditions for actual buildings that fall somewhere in between the idealizedconditions they focus on in their undergraduate courses.
Raney, J. M., & Laursen, P., & McDaniel, C. C., & Archer, G. C. (2015, June), Influence of Boundary Conditions on Building Behavior Paper presented at 2015 ASEE Annual Conference & Exposition, Seattle, Washington. 10.18260/p.24296
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