Why do we use property modifiers in Etabs?
During earthquake or dynamic load event the section of the concrete cracks and the concrete below the neutral axis or the One in tension region would be ineffective. This leads to decreased stiffness of the section. In order to account for this effect we would use property modifiers in etabs .
What are property modifiers in ETABS?
Property modifiers in ETABS are used to model cracked behavior of concrete sections. They are onlyapplied to concrete members because of cracking.
How do you use property modifiers in Etabs?
When drawing in ETABS the default is to have the 1 axis horizontal and the 2 axis vertical. This means that the flexural modifier for EI should be applied to f22 for wall piers and to f11 for spandrels. If you apply the modifier to both f11 and f22 it hardly affects the results.
What is torsional constant in Etabs?
The significance of Torsional Constant (J) is that when J is multiplied with Shear Modulus (G) it gives Torsional Rigidity. You will have to see books on Advanced Mechanics of Materials to get a more in depth knowledge on this. Coming to its value modification in ETABS, if J is kept as 1, the member will take all the.
What are property modifiers?
Property modifiers may be used as a scale factor to modify the stiffness of section properties for frame, shell, and tendon objects. Property modifiers may be assigned either to object sections or to the objects themselves.
What is f12 in Etabs?
The cracked behavior of shear walls and other shell objects may be modeled in ETABS by using property modifiers to adjust their stiffness. f12 controls shear behavior through the GA component.
Why do we use stiffness modifiers?
Consideration of the stiffness modifiers will reduce the seismic demand on the structure. But at the same time, it will result in relatively higher drifts due to increased flexibility of the structure. The stiffness modifiers are to be used only for structural analysis.
What is S11 and S22 in Etabs?
o S11: Direct stress (force per unit area) acting on the positive and negative 1 faces in the 1-axis. direction. o S22: Direct stress (force per unit area) acting on the positive and negative 2 faces in the 2-axis. direction.
How can we decrease the torsional constant?
However, if you want to redistribute the torsional stresses to some other member e.g. a beam is connected to a slab or a wall and you want the torsional stresses in the beam to be redistributed to the slab or wall then you can set a very low Torsional Modification Factor value e.g. 0.01 for the beam.
What are stiffness modifiers?
stiffness modifiers in ETABS are the factors to increase or decrease some properties of the cross. section for example area, inertia, torsional constant etc. Generally they are used to reduce stiffness of concrete sections to model for cracked behavior of. +4.
What is f11 f22 f12 in Etabs?
According to ETABS manual and ATKINS manual, ” The f11, f22 and f12 modifiers are essentially equivalent to modification factors on the thickness of the shell element. The m11, m22 and m12 modifiers are essentially equivalent to modification factors on the thickness3 of the shell element.”
Are stiffness modifiers required only for analysis or for design as well?
Q-4 Are stiffness modifiers required only for analysis or for design as well? The stiffness modifiers should be considered only for the structural analysis. The analysis results to be derived considering the stiffness modifiers.
What is the effect of modifiers in ETABS model?
Modifiers will affect stiffness, hence everything in the model will be affected, by some degree. In most cases Modifiers in ETABS are used to try to somehow capture the effect of cracking in concrete structures. In SAFE you can do an explicit nonlinear cracking analysis so you don’t need modifiers at all, otherwise you will get wrong results.
When is the default code set in ETABS?
Setting default code i guess is done during the time of installation of the software. If you are asking about adding newer design codes in ETABS, you might want to contact CSI instead.
What is the stiffness modifier used in is 456?
The stiffness modifiers are used to take into account the cracking of RCC sections. IS 456:2000 does talk about stiffness of members in Clause 22.3. However, it does not provide the modifier values to be used. You can refer Code Section 10.11 of ACI 318 for stiffness modifier values suggest by ACI.
What would happen if there is no stiffness modifier in structural engineering?
Stiffness modifiers can have significant effect on the behavior of the structure. In absence of stiffness modifiers the structure would be stiffer and thus attract higher lateral forces due to earthquake. So you might end up with heavily reinforced shear walls , moment frames etc Yes, you are correct.