What is stiffness modifier?

What is stiffness modifier?

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.

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 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 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.

What is property modifier?

Property modifiers may be used as a scale factor to modify the stiffness of section properties for , , and objects. Property modifiers may frame shell tendon be assigned either to object sections or to the objects themselves.

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.

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 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.”

What do we mean by stiffness?

Stiffness is the extent to which an object resists deformation in response to an applied force. The complementary concept is flexibility or pliability: the more flexible an object is, the less stiff it is.

What do you mean by stiffness?

Stiffness is defined as the resistance to a force causing a member to bend. Stiffness is very important to the end-use performance of many papers.

What is inplane and out of plane stiffness in ETABS?

In ETABS, shell or area element has two types of stiffnesses i.e. inplane stiffness refers as f11, f22 and f12 and out-of-plane stiffness refers as m11, m22 and m12. Refer to the below Figure which shows the direction of local axes and their corresponding stiffnesses:

What are initial stiffness modifiers in ACI code?

As per ACI code, the initial stiffness modifiers are to be assingned for wall/slab/column/beam structural elements. Wall -> Assigned with shell element -> f11, f22,f12 are related to in-plane forces.

What is the flexural modifier for EI 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.

What are the initial stiffness modifiers for wall/slab/column/beam structural elements?

As per ACI code, the initial stiffness modifiers are to be assingned for wall/slab/column/beam structural elements. Slab – 0.25 Ig Wall – 0.70 Ig Beam – 0.35 Ig