ETABS Tutorial 7: Detailed Explanation of Stiffness Modifiers of Shell Elements (Shear Walls & CB)

This video comprehensively explains stiffness modifiers for shear walls and coupling beams in ETABS software. Both shear walls and coupling beams were modeled using a shell element. Each modifier's meaning is carefully explained using easy-to-understand illustrations. Additionally, this video presents an example that demonstrates the significant impact of changing these modifiers on the overall response of the structure.
0:00 Changing the Flexural Stiffness of the Shear Wall
1:03 Mechanics of Cracking of Concrete Members
3:30 Explaining ETABS Stiffness Modifiers
7:01 Illustration of stress distribution based on a Laterally displaced coupled wall system
9:41 In-plane and Out-of-plane bending of shear walls
10:25 Example on the effect of changing the stiffness modifiers
You can access and download the Excel sheets by clicking on the link below:
drive.google.com/drive/folder...

[@shareqinamdar8903]

Good explanation

[@Eng.tarekyoussef]

Thank you

[@muhammadsohailhussain849]

Loved it, Cleared my Concept, Thanks, JazzakAllah

[@Eng.tarekyoussef]

You are most welcome

[@pedjamarkovic6676]

Very good explanation ! Thanks for sharing!

[@Eng.tarekyoussef]

wlc

[@NirjhorKabir]

Informative thank you so much.

[@Eng.tarekyoussef]

You are welcome

[@user-qk1jf5nl7z]

Great job

[@Eng.tarekyoussef]

Thank you

[@Aussie_Engineer]

Superb 🎉

[@Eng.tarekyoussef]

Thank you

[@raghavmoyade7862]

Thank you..

[@Eng.tarekyoussef]

You're welcome

[@muhammadsohailhussain849]

Could you brief the behaviour of modifiers for the bearing wall system please. They don't go under crack or non-cracked just for gravity

[@Eng.tarekyoussef]

In a bearing wall system, the walls primarily carry vertical loads, known as gravity loads. So, when considering modifiers for such walls, it's important to assume an un-cracked section, as cracking can occur due to gravity loads alone, even without considering lateral loads. This ensures that the design adequately accounts for potential cracking under gravity loads.

[@surinderghurdora8537]

Thnq soo much 💯

[@Eng.tarekyoussef]

You are welcome

[@Zorot99]

When should I consider cracked sections for the concrete elements?

[@Eng.tarekyoussef]

In our concrete element design, we focus on the ultimate load condition, anticipating structural component cracking. Consequently, we adjust stiffness to account for this expected cracking effect.

[@was0119]

For shear wall, it is f12 that affects the most (not f11 and f 22)?

[@Eng.tarekyoussef]

"f" represents the axial forces/stresses, "1" corresponds to the face perpendicular to local axis number 1, and "2" indicates the direction of the force acting on face 1 (Same direction as local axis number 2). If the default orientation of the local axis is used for shear walls (local axis 2 oriented in the Z-direction), and by modifying f12, you are essentially changing the axial force or stress acting on face 1 (vertical section) in the direction of local axis 2. This alteration can impact the equilibrium of forces within the member and consequently affect its shear behavior only.

[@anisrehman9353]

Please make a video on expansion joint in building.

[@Eng.tarekyoussef]

Absolutely, I think that's a great idea. I'll definitely consider adding a video on expansion joints as one of the topics in my future uploads. Your suggestion is much appreciated!

[@aldiputra9236]

Normally when I was check using modiefier the reincforcement req be small than if you using default stiffener..why that can be happen you think?? Is it dengerous or not if you reduce the reinforcement because modifier stiffner change??

[@Eng.tarekyoussef]

The reduction in reinforcement requirement when using modifiers compared to default stiffness may occur due to the adjustment in the distribution of loads within the structure. When modifiers are applied, the stiffness characteristics of components is changed, resulting in redistribution of loads within the structure. This redistribution can lead to reduced demands on certain elements, resulting in a lower overall reinforcement requirement. In general, higher stiffness means ==> higher demand forces ==> higher reinforcement ratio

[@calvoh9715]

@@Eng.tarekyoussef so does this means in earthquake, the beam having 0.35I reduction in stiffness and column 0.7I means the beams is more flexible than column, therefore, the beam fails first before column? For reduced reinforcement due to stiffness modifier, what does it mean to the beam? the beam with less reinforcement is forced into ductility?

[@Eng.tarekyoussef]

In seismic design, when a structure experiences an earthquake, the stiffness modifiers (such as 0.35I for beams and 0.7I for columns) are used to represent the reduction in stiffness of elements due to various factors like cracking, yielding, or inelastic behavior. Yes, if the beam has a stiffness modifier of 0.35I and the column has a stiffness modifier of 0.7I, it implies that the beam is relatively more flexible compared to the column. However, it doesn't necessarily mean that the beam will fail before the column. The behavior of the structure during an earthquake is complex and depends on various factors including the stiffness, strength, and ductility of individual elements, as well as their connections. Reduced reinforcement due to stiffness modifiers means that during an earthquake, the stiffness of the structure is reduced due to cracking or yielding of reinforcement. This can lead to increased deformations and redistribution of forces within the structure. Regarding your question about the beam with less reinforcement being forced into ductility, it's important to clarify that ductility is a property of materials and structural elements to undergo significant deformation before failure. In seismic design, ductility is desirable as it allows structures to dissipate seismic energy through controlled deformations rather than sudden failure. If a beam has less reinforcement, it may indeed be forced into ductility more readily during an earthquake because it has less resistance to the applied forces. However, this doesn't necessarily mean that it will fail in a ductile manner unless the design and detailing of the structure are done to ensure ductile behavior under seismic loading.

[@pedjamarkovic6676]

Also, you should consider stiffness modifier on floors, you will obtain more reinforcement in beams!

[@user-qu2tj6ih5z]

شكرا جزيلا ياريت ترسل لنا رابط الملفات

[@Eng.tarekyoussef]

You can access and download the Excel sheets by clicking on the link below: drive.google.com/drive/folders/1WWyrqs8OaJbvIjkEqigb8ki_FDQmfauO?usp=sharing