Understanding Moment of Resistance and Stress Distribution in Beams

• structural mechanics
Dr Jawed Qureshi covers moment of resistance and stress distribution in rectangular beams.
07 Understanding Moment of Resistance and Stress Distribution in Beams
Moment of Resistance or Moment Capacity is like the strength of a beam or structure to resist bending. Imagine a diving board - it can handle a certain amount of weight before it bends too much and breaks.
When a force (like weight) tries to make a structure bend, the moment capacity is the measure of how much bending it can endure before it becomes unsafe.
The stress distribution in a structure shows how the materials inside are handling this bending. It's like checking if the diving board stays strong and doesn't crack under pressure. Understanding these concepts helps engineers build safe and sturdy structures.
Link to lecture slides: tinyurl.com/JQureshiMechanics
00:00 - Introduction
01:33 - Stress distribution across a section
08:12 - Moment of Resistance
09:08 - Example 1: Stress distribution rectangular section
12:50 - Example 2: Moment of Resistance for rectangular beam
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Disclaimer: This material is provided on an 'as is' basis with no warranty. There is no guarantee that the material will meet your requirements, that the material is error-free, that results obtained from the use of the material will be reliable, nor that any errors in the material will be corrected.
Copyright: Dr Jawed Qureshi holds the copyright to this lecture series. He is a senior academic in London, UK with international experience of over 20 years. Dr Qureshi holds a PhD in steel -concrete composite structures from The University of Leeds and has a prior teaching experience at The University of Warwick. He is currently working at a London University as a Senior Lecturer in Structural Engineering and Design.

[@DrJQureshi]

* Correction - Slide 10: The second moment of area, Ixx and Iyy for circular is pi(d)4/64.

[@user-kf8sm6bf6d]

Thanks for such valuable service for engineering community

[@DrJQureshi]

I'm really touched by your kind comments

[@sothattheng8624]

Thanks for your sharing!

[@DrJQureshi]

My pleasure!

[@Mr.Tanveer]

Zabardast

[@DrJQureshi]

Thanks

[@supriyaroy6462]

Thank you so much sir

[@DrJQureshi]

You are most welcome. It’s always pleasure to be of any help.

[@shahmi98]

Thank you so much

[@DrJQureshi]

You're most welcome

[@akashpanda1]

Thanks Sir. Your efforts is highly appreciated.

[@DrJQureshi]

I’m grateful for kind comments!

[@michaelchomba2292]

Thankyou so much Doc. Clear and practical explanation!❤

[@DrJQureshi]

Michael, I'm grateful for your kind comments.

[@adno5933]

Let say, I've got to design a single wind post out of rectangular steel section, grade S275. σ=275N/mm2. Can I use this formula to work out Mcr and compare it with Med (knowing point load on cantilever, say 074kN)?

[@DrJQureshi]

You cannot use these formulae in the lecture to work out buckling moment. Use procedure in another lecture kzbin.info/www/bejne/fmexpp6AjZeKnLMsi=aXba56h4HOMTjZJy to design steel cantilever beam. Please note Lcr for cantilever beam will be 2L.

[@adno5933]

This works for all sections in the Blue Book, however where do I find section properties for non-structural sections such as flat, say 40x20? @@DrJQureshi

[@AhtesamKhan-ix9jn]

Good Morning Sir, I have a question, how to find the deflection for multiple point load on simply supported point..

[@DrJQureshi]

Hi good morning! You apply the same logic. Use equilibrium equations to find reactions. Once you’ve got reactions, you can then find out moment at different point along the length of the beam.

[@AhtesamKhan-ix9jn]

@@DrJQureshi Sir can we apply superposition principal for find the deflection if the the beam subjected to multiple loading at different locations on same beam . Because I have compared the results with staad and risa and i found software also following the superposition principal for calculation of deflection.. please provide your insights..

[@DrJQureshi]

Lecture slides available at tinyurl.com/JQureshiMechanics

[@blueeyedeurasian]

how will i explain in the simplest term if i am asked in an interview about what is moment of resistance?

[@DrJQureshi]

Moment resistance is structural element's ability to withstand and counteract bending forces. Imagine a horizontal beam in a building. When loads or forces act on it, it can start to bend or sag. Moment resistance measures the beam's capacity to resist this bending and maintain its shape. Engineers assess this property to ensure that structures like bridges and buildings can handle the expected loads without deforming or failing. It involves using materials, design, and construction techniques to strengthen the structure's ability to withstand these bending forces.

[@DrJQureshi]

I hope this helps. I suggest using the language that you are comfortable in speaking. May be rephrase to use a common language. In very simple language, moment capacity or resistance is the ability of a cross-section to resist applied bending forces. If this ability is more than applied bending forces, the section is safe in bending. I'm pleased to be of any help to you. My prayers are with you for a successful interview.

[@blueeyedeurasian]

@@DrJQureshi Thank you so much. Honestly, this is the clearest explanation I've gotten so far.

[@DrJQureshi]

WATCH Mechanics playlist tinyurl.com/JQmechanics

[@akashpanda1]

Kindly explain the difference between moment of resistance and bending moment. Are they same, Sir ?

[@DrJQureshi]

Bending is of two types: moment capacity or resistance and applied moment. I mostly take applied bending moment as “bending moment”. The applied moment depends on applied forces, end supports and beam length. For example, for simply supported beam with a central point load applied moment is PL/4, where P is the central point load and L is the length. Moment of resistance or moment capacity is the ability of a section to resist bending. This is determined from flexural formula, stress = My/I, where M is moment of resistance, y is distance from centroid of section to top or bottom of the section and I is second moment of area/moment of inertia. For structural steel stress is 275N/mm2 and for timber stress is 16 N/mm2. I is bd3/12 for rectangular sections, where b is width and d is depth of section. Moment of resistance or moment capacity should be more than applied moment. In that way we ensure that beam can take applied forces. In real-life applications, other considerations for beam design include shear and deflection. I have a complete lecture on steel beam design in steel design KZbin playlist.

[@akashpanda1]

Understanding moment of resistance was very difficult Sir. Because many prescribed text books have not explained it like you. Thank you very much Sir. Can the value of applied bending moment be same as the moment of resistance Sir, or always moment capacity is greater than bending moment?

[@DrJQureshi]

@@akashpanda1 The moment or any other loading capacity should always be more than the applied moment or loading for safe design. The purpose of structural analysis is just to find internal forces due to applied loads and deflections. The purpose of design is to find capacity.

[@akashpanda3410]

Understood Sir. Thanks again.

[@krishalbasnet]

copying clips from the efficient engineer?

[@DrJQureshi]

Clips are used as per fair use policy. It helps people understand the topic better.