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Showing content with the highest reputation on 04/07/17 in all areas

  1. WSalaam.. ASD is design based on actual non-factored loads considering reduced material strength capacties. For example, for 100 kN load on a steel beam with yield of 350 MPa, you will design it using 100 Kn load and a strength of 2/3*350 MPa= 232 MPa. The reduction in material strength would provide safety, calculated as ratio of actual strength/ (reduction factor * actual strength). This ratio is called Factor of Safety (FOS). FOS would vary for foundations, steel or concrete design etc. ULS is based on factored loads (load factor as per the statistical probability of likely hood of occurance causing failure) with reduced material capacites. The reduction in material capacites is lower than what ASD has. Like for steel design, material reduction factor is 0.9 only which is a mere 10% reduction. ULS is improved and currently the way to go in most building codes worldwide. Some building codes even prohibit using ASD. The following link contains an excellent reply by @EngrUzair about cost Compairson b/w ASD and LRFD. WSD is same as ASD. Secant modulus represents elastic behavior between stress and strain values (as it is a straight line) whereas tangent modulus gives you relationship in any portion of stress strain curve (elastic, plastic etc). Thanks.
    2 points
  2. A two hour session will be held in the Wah campus of CIIT. The attendees will receive a certificate which can be helpful for engineers in matters of PEC-registration. The speaker will be discussing the topic of performance-based design and evaluation of tall buildings. It is good opportunity for structural engineers to equip themselves with recent advancements regarding the structural analysis and design of tall buildings. The speaker, Dr. NAVEED ANWAR, who is executive director at AIT Solutions, is not only a Structural engineer, but also has been actively involved in software-development of CSI products such as ETABS, SAP2000 and CsiCol. Please find the brochure in the attachment for further details. CPD_Dr Naveed_1.pdf
    1 point
  3. Push over analysis is mostly related to get the capacity of a building for max. displacement. Mainly used for retrofitting of old buildings.. Pushover curve is a strength-deflection curve.. Plot force vs displacement curve.. The pt. where the strength drops drastically is the limit of the storey, its the state describing the collapse of the frame..
    1 point
  4. 1 point
  5. Dear Mr.Rana Waseem, Thanks for your response. I am working on a tall building for which column magnification procedure is found to give inconsistent result. For elastic linear second-order analysis from what I understood, I am approaching as follows: 1. Assigning stiffness modifier to all structural members as indicated in ACI 318-11 10.10.4.1 2. Assigning eccentric column by using Frame insertion point option to option for addition moment from M=P.e. 3. For columns which have problem, I am dividing it into 5-6 segments depending on judgement to capture local P-delta effect of second order moment resulting from deflection in the chord of the frame element between nodes. i.e. M=P x d ( Small delta ) 4. Enabling p-Delta option in Etabs so that it can calculate moment that will result from deflection indicated in Step.3. 5. In design preference, I modified consider eccentricity option to "No" so that it doesn't consider additional moment as I have already defined it in Step2 and also put magnifier to 1. 6. After running the analysis, column with problem in loads that are close to Buckling load will give error. (Though I am still not in favor of conservative buckling load calculation made by ETABS). Any Addition would be appreciated.
    1 point
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