Is the design in the allowable stress limit (Full Stress Design) necessarily the optimal design?
This is a question that has been discussed a lot in the engineering literature, and it will be examined from some angles in the following:
1⃣ Many common construction structures are indeterminate structures and the load on each member is related to the stiffness of the members, and it is possible to find a better FullStress option for the structure due to the FullStress figure of all the members due to their false loading. One of the most important examples for such a system is the false twisting of the floors due to the distance of the center of mass from the center of stiffness, which imposes an additional load on the peripheral members of the lateral bearing system.
2⃣ Even assuming that the lateral bearing system is certain, if the stiffness of the system has an effect on the amount of earthquake load (such as the spectral analysis method), the stiffness system that takes a lot of load with a low period and is even designed as FullStress is definitely not an optimal design. .
3⃣ Assuming that the lateral load is certain and does not depend on the lateral stiffness of the structure, by changing the cross-sections, it is possible to reach another FullStress system that has less weight. For example, in a simple metal beam, by increasing the height and decreasing the wing area, better results will usually be obtained.
4⃣ The optimal plan is the low-cost plan and the secondary effects of a FullStress plan should also be seen. For example, a centralized lateral bearing system may have more side effects on the foundation, which leads to the use of piles and . . to be
‼ As a result, for each structure, there are many FullStress responses, only one of which is optimal, and you cannot claim to optimize the structure just by designing FullStress.
(Unfortunately, some famous claimants of structure optimization in Iran still do not know the difference between FullStress design and optimal design and seduce employers by presenting a totally purple design)
Structure optimization group
https://t.me/joinchat/AAAAAD73Vx-xcrLVPWYgkQ
This post is written by Mogh1367