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Unformatted text preview: EGN EGN5439 The Design of Tall Buildings 5439 The Design of Tall Buildings Lecture #21 Lecture #21 Preparing the Model for Analysis The Preliminary Analysis The Final (and hopefully, accurate) Analysis L. A. PrietoPortar  2008 Outline: Outline: 1) Approaches to Analysis. Preliminary Analyses Intermediate and Final Analysis 2) Assumptions. Materials Participating Components Floor Slabs Negligible Stiffnesses Negligible Deformations Cracking 3) HighRise Behaviour. 4) Modelling for Approximate Analyses. Approximate Representation of Bents Approximate Modelling of Slabs Modelling for Continuum Analyses 5) Modelling for Accurate Analysis. PlaneFrames Plane Shear Walls 3D Frame and Wall Structures P Effects The Assembled Model 6) Reduction Techniques. Symmetry and Antisymmetry 2D Models of Nontwisting Structures 2D Models of Structures That Translate and Twist Lumping WideColumn DeepBeam Analogies. A buildings response to loading is governed by the components that are stressed as the building deflects. a) Ideally, for ease of analysis, this would only include structural components; b) In reality, other nonstructural elements, such as staircases, partitions, and cladding, become stressed and contribute to the buildings behaviour; c) To simplify analysis, it is assumed that the effects of nonstructural components is small and conservative. By neglecting consideration of the nonstructural and less essential structural components, the problem of analyzing a tall building can be reduced to a more viable size. a) For extremely large or complex structures, it may be necessary to reduce even further the size of the analysis problem by representing some of the structures assemblies by simpler analogous components. Preliminary Analysis: The analyses for early stages of design are used to: Compare the performance of alternative proposals for the structure. Determine the deflections and major member forces in a chosen structure so as to allow it to be properly proportioned. Formation of the model should be rapid and produce results that are dependable approximations. The simplifications adopted in making a preliminary model include: Approximation of members, such as assuming a simple cantilever to represent a complex bent. Simplification of the loading, such as assuming a uniform load across the height of the building. Even with the gross approximations made in simplifying the structure and the loading, it is generally expected that a preliminary analysis should give results for deflections and main member forces within 15% of that from an accurate analysis. The preliminary analysis simplifies the initial model by: a) including only the main structural elements, slabs or plates, columns, shear walls and core elements, girders and beams....
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This note was uploaded on 08/29/2011 for the course CES 4600 taught by Professor Staff during the Fall '08 term at FIU.
 Fall '08
 STAFF

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