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4 DSM Design Guide

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Information about 4 DSM Design Guide
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Published on January 2, 2008

Author: Mentor

Source: authorstream.com

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DSM Design Guide:  DSM Design Guide DSM Design Guide:  DSM Design Guide Introduction Elastic Buckling Member elastic buckling examples overcoming difficulties Beam, Column, and Beam-Column Design Product Development Design Examples Using the Guide:  Using the Guide (pg. 1) DSM Advantages:  DSM Advantages Practical advantages of DSM: no effective width calculations, no iterations required, and uses gross cross-sectional properties. Theoretical advantages of the DSM approach: explicit design method for distortional buckling, includes interaction of elements (i.e., equilibrium and compatibility between the flange and web is maintained in the elastic buckling prediction), and explores and includes all stability limit states. Philosophical advantages to the DSM approach: encourages cross-section optimization, provides a solid basis for rational analysis extensions, potential for much wider applicability and scope, and engineering focus is on correct determination of elastic buckling behavior, instead of on correct determination of empirical effective widths. (pg. 2) DSM Limitations:  DSM Limitations Limitations of DSM (as implemented in AISI 2004) No shear provisions No web crippling provisions No provisions for members with holes Limited number/geometry of pre-qualified members No provisions for strength increase due to cold-work of forming Practical Limitations of DSM approach Overly conservative if very slender elements are used Shift in the neutral axis is ignored Limitations of finite strip method Cross-section cannot vary along the length Loads cannot vary along the length (i.e., no moment gradient) Global boundary conditions at the member ends are pinned (i.e., simply-supported) Assignment of modes sometimes difficult, particularly for distortional buckling (pg. 6) DSM Design Guide:  DSM Design Guide Introduction Elastic Buckling Member elastic buckling examples overcoming difficulties Beam, Column, and Beam-Column Design Product Development Design Examples Slide7:  (pg. 10) Slide8:  (pg. 12) Elastic buckling upperbounds:  Elastic buckling upperbounds Beams if Mcrl > 1.66My then no reduction will occur due to local buckling if Mcrd > 2.21My then no reduction will occur due to distortional buckling if Mcre > 2.78My then no reduction will occur due to global buckling Columns if Pcrl > 1.66Py then no reduction will occur due to local buckling if Pcrd > 3.18Py then no reduction will occur due to distortional buckling if Pcre > 3.97Py a 10% or less reduction will occur due to global buckling if Pcre > 8.16Py a 5% or less reduction will occur due to global buckling if Pcre > 41.64Py a 1% or less reduction will occur due to global buckling (pg. 9) DSM Design Guide:  DSM Design Guide Introduction Elastic Buckling Member elastic buckling examples overcoming difficulties Beam, Column, and Beam-Column Design Product Development Design Examples Elastic buckling examples:  Elastic buckling examples C, Z, angle, hat, wall panel, rack post, sigma.. (pg. 16) Z-section with lips:  Z-section with lips (pg. 26) Z-section with lips modified:  Z-section with lips modified (pg. 28) Comparison:  Comparison (pg. 26 and 28) Comparison:  Comparison (pg. 26 and 28) DSM Design Guide:  DSM Design Guide Introduction Elastic Buckling Member elastic buckling examples overcoming difficulties Beam, Column, and Beam-Column Design Product Development Design Examples Overcoming FSM difficulties:  Overcoming FSM difficulties The discussions in the following section are intended to provide the design professional with a means to apply “engineering judgment” to an elastic buckling analyses. When in doubt of how to identify a mode, or what to do with modes that seem to be interacting, or other problems; remember, it is easy to be conservative. Select the lowest bucking value (i.e., Pcr, Mcr) of all mode shapes which includes some characteristics of the mode of interest. This ensures a lowerbound elastic buckling response. However, this may be too conservative in some cases, and the challenge, often, is to do better than this and use judgment to determine a more appropriate (and typically higher) approximation. (pg. 42) Multiple modes:  Multiple modes (pg. 46) Global modes at short L:  Global modes at short L (pg. 47) DSM Design Guide:  DSM Design Guide Introduction Elastic Buckling Member elastic buckling examples overcoming difficulties Beam, Column, and Beam-Column Design Product Development Design Examples Beam Chart:  Beam Chart (pg. 58) AISI (2002) Design Manual:  AISI (2002) Design Manual (pg. 61) Column Chart:  Column Chart (pg. 64) DSM Design Guide:  DSM Design Guide Introduction Elastic Buckling Member elastic buckling examples overcoming difficulties Beam, Column, and Beam-Column Design Product Development (later today) Design Examples Design Examples:  Design Examples C-section with lips, C-section with lips modified, C-section without lips (track section), C-section without lips (track section) modified, Z-section with lips, Z-section with lips modified, Equal leg angle with lips, Equal leg angle, Hat section, Wall panel section, Rack post section, and a Sigma section. Beam chart construction and Column Chart construction

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