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- To: seaint(--nospam--at)seaint.org
- Subject: Re: need help
- From: Jim Kestner <jkestner(--nospam--at)somervilleinc.com>
- Date: Wed, 08 Nov 2000 08:12:47 -0600
Daniel: The second part of your initial question asked about how do you know whether you have achieved an economical or efficient design. From a practical standpoint, the efficiency would be evaluated based upon cost of the entire building, not just the structural portion. A purely efficient structural design may not always yield an efficient total building design. For example, deeper floor beams may be structurally efficient but will add to the total floor to floor height and therefore will increase the cost of the exterior walls, mechanical runs , stairs and elevators. Your main objective should always be the lowest total cost for the whole building. That said, they may be specific areas that you can investigate. For example, a rigid frame controlled by stress can be optimized by designing members with stress ratios as close to 1.0 as practical. A rigid frame controlled by lateral deflection will require the engineer to evaluate which is more efficient: to stiffen the columns or the beams. This can be evaluated by looking at the deflection component controlled by the stiffness of the column and the deflection component controlled by the beam. The approximate lateral deflection component can be derived from the portal method. Column deflection due to column stiffness= fixed-fixed columns with reverse curvature due to story shear. Column deflection due to beam stiffness = beam end rotation times the column height. Beyond this, keeping the details simple and repetive will make for cost efficencies which will help minimize the total building cost. Jim Kestner, P.E. Green Bay, Wi.
- need help
- From: Daniel Singgih_Rusdy
- need help
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