1. So in general the advantage of column base and foundation rotational restrain is it will take greater seismic load to form plastic hinges in the beam ends?
2. Can shear wall and braced frames make the beam-column joint completely rigid or will it still rotate? how many percentage compared to...
Ok. It's neigher pinned not fixed.. meaning the foundation is just *put* on top of the rock. You are worried any movement of the rock can transfer to the foundation.. but the foundation is mat foundation.. so any movement of the rock should transfer to it due to the coefficient of friction...
Ron, I know that.. i'm talking of the following context.. where for example dik mentions in
http://www.eng-tips.com/viewthread.cfm?qid=255771
"Higher strength concrete is more brittle and less ductile. It is, however, higher strength... It behaves plastically a little better... but brittle...
If you make the columns very big like 1 meter diameter and add so many rebars like 50 pcs of 25mm grade 60 rebars.. it would still deflect? Or become completely rigid. When this is fully moment connected fixed to the foundation and there is lateral movement, the column would no longer deflect...
It is said that 3000 psi concrete are more ductile than 4000 psi.. by how many percentage? do you use 3000 psi or 4000 psi in your building (ordinary and special moment frames)? I know so many structural engineers who have never use 4000 psi.. they just use 3000 psi.. how about you?
so let me rephrase the question
in page 7 of http://nehrp.gov/pdf/nistgcr8-917-1.pdf
"Base restraint can have a significant effect on the behavior of a moment frame. ASCE 7 - 12.7.1 (Foundation Modeling) states “for purposes of determining seismic loads, it is permitted to consider the...
I know the base is moment connected.. what I meant was zero rotation because it is fixed.. so if the column has zero rotation at the base.. likewise it has zero rotation above at the beam column joint so why worry about seismic forces in the beams? the beams cant rock back and forth or sway from...
Ok. I'm analyzing this material about special moment frames.. http://nehrp.gov/pdf/nistgcr8-917-1.pdf
page 7 mentions:
"Base restraint can have a significant effect on the behavior of a moment frame. ASCE 7 - 12.7.1 (Foundation Modeling) states “for purposes of determining seismic loads, it is...
If rotational restraint can really be RELIED upon.. like using mat foundation on stiff rock. Then it can be an alternative to shear walls and braced frames? Because shear walls need to be symmetrical or torsion can be introduced where the other parts rotate against the stiffer unsymmetric shear...
If you can't make shear walls or braced frames and rely on column foundation rotational restraint (*assuming* you have a stiff soil/rock).. how much can it equal the first two in effectivity?
If you have stiff soil and you don't want to use shear walls or braced frames. How much can you rely...
When you brace the frames.. there is less moment demands on the beams. Likewise if you fixed the column-foundation, there is less moment demands on the beams...
But it seems many structural engineers would rather design better beams to withstands seismic moments than designing better...
Ok, I was tying it to physics.. Inertia has energy and momentum, it has to go elsewhere.. so it either goes to the ground "bending" the soil or every fabric and molecules of the rebars have to compress and take in the energy.. in other words.. act elastically..
Has anyone designed seismic...
So in areas with soft soil. Even if you can make fixed (rotational restrained) column-foundation (rather than pinned) connection. It doesn't help much because the moment is transferred to the foundation which can rotate aginst the soft soil? So fully fixed rotationally restrained...
BAretired.. it means if the soil is soft.. you need to make the foundation big enough such that the entire foundation won't rotate against the soil? meaning about 4 times bigger than normal. Because when the column to foundation is pinned.. it is the column that would rotate.. but if the column...
It is said that when you designed the column to foundation connection to be fixed (and not pinned).. the foundation must transfer the moment (bigger values) to the soil.. but what if the soil is stiff.. what does it mean to transfer the moment from the foundation to soil especially if the soil...
In lateral movements. Inertia is created in the roof or floor and this is transferred to beams.. to columns.. to foundation.. and to soil.. but what if the soil is stiff like rock and you have a more than average sized foundation for complete fixed rotational restraint of the columns. How does...
