Leaderboard

See the attached document: ACI 214.4R-03: Guide for Obtaining Cores and Interpreting Compressive Strength Results ACI_2144r_03.PDF

Assalam-o-alaikum! Umair is right. According to ACI 318-11 Section 21.1.4.1, the requirements of section 21.1.4 apply to special moment frames, special structural walls and all components of special structural walls, including coupling beams and wall piers. Since slabs and footings are not mentioned, probably 2500 psi concrete (minimum as per ACI section 1.1.1) may be used for these elements. However, according to ACI section 4.1.1, minimum value of specified concrete compressive (fc′) shall be the greatest of the values required by following three criteria: a. ACI section 1.1.1 requirement i.e., 2500 psi minimum b. Requirement for durability, as per ACI Chapter 4, and c. Actual requirement, from structural strength point of view As such, most likely 3000psi may be likely choice in many cases. On the other hand, use of 2500 psi and 3000psi concrete for most of the small scale projects might not result in appreciable saving in the project cost. From construction point of view also, it will generally be time saving and preferable to use concrete of one compressive strength, as compared to the opposite. Regards.

First , I am Very Happy to Participate in Forum Such As This Forum , I need to Make Engineering Discussion With These Questions 1. Why We Make Scale Factor Between Static And Dynamic Seismic Analysis ? 2. After Scale Factor We Design By Load Combinations Included Dynamic Cases Only Or Static Load Only Or Dynamic And Static ? 3. What is Diaphragm And What is Importance of Diaphragm In Seismic And Wind? 4. When We Define Diaphragm? And We Define As Rigid Or Semi Rigid And What is the Different Between Them? 5. Different Between Displacement And Drift Due to Seismic ? 6. Displacement Due to Seismic Results From Etabs We Multiply it X 0.70 X R ,Why And What About Drift ? 7. We Make 3 Cases For Each Case ( X AND Y ) in Static Analysis What About Dynamic Same Or Not Static Analysis Ex Ex With + Eccentricity Ex With – Eccentricity Ey Ey With + Eccentricity Ey With – Eccentricity 8. Why We Don't Combine Seismic And Wind in Load Combinations? 9. In Dynamic Analysis , Forces Cause Mode Shapes Or Mode Shapes Cause Forces? 10. Difference Between Response Spectrum ( Dynamic ) And Time History , Which Best? 11. What is the Effect of Seismic in Slabs And Beams? 12. Design Of Slabs And Beams By Load Combination Included Seismic Right Or Wrong? 13. After Finishing 3D Model , What are the Checks For Seismic? 14. Slab On Grade , I Put In Etabs Or Not ? 15. How Building Make Damping For Seismic ,What is Factors Damping Depend on? 16. Different Between Point Drift – Story Drift – Diaphragm Drift ?

Assalam-o-alaikum! Shear reinforcement values indicated on the column member are generally the maximum values for the two shear axes, whether these are from on load combo or from two different load combos. Right-cIick on the member reinforcement diagram generally leads straight to load combo resulting in the maximum longitudinal or maximum shear reinforcement. However, as you have indicated, I am unsure, why this does not always happen. Surely, someone else might be able to explain this. Interpretation of shear reinforcement value 'Av/s', given by ETABS, is not very difficult. Since your units are 'kip-in", Av (i.e. cross-sectional area of ties) is in 'sq.in.' and s (i.e., spacing) in 'inches'. For your case, Av/s = 0.045. For 2-legged #3 ties, Av = 0.11x 2 = 0.22 sq. in. Substitution of value of Av in above equation, results in required tie spacing, s = 0.22 / 0.045 = 4.88 in. Regards.

I would use the ground floor as base for seismic loads instead of basement. The reason is that the combination of ground floor diaphragm and perimeter basement wall offers a very rigid system. This statement would be true for buildings with 1 or 2 underground stories. If you have got more stories than a separate analysis for sub structure and superstructure should be done. The above quoted rule is based on my own personal experience. You should ensure that all limit states are satisfied and do your due diligence. I am keeping things as simple as could be kept while replying. Please have a look at the attached documents that explain some aspects about subject thread. Basement Wall with Seismic Earth Pressure.pdf Seismic Performance Of Structures with Underground Stories.pdf Thanks.

Yes, slab connects all the lateral forces resisting elements and acts as diaphragm. Further Reading: http://www.sepakistan.com/topic/87-diaphragm/ http://www.sepakistan.com/topic/1480-diaphragm-flexibility/ Thanks.

Good suggestions have been provided to you. IMHO, you will get ample time after graduation to use softwares. You should improve your understanding of subjects that are being taught to you. Remember, as an engineer, you can't design what you can't understand and visualize. Studies are very important, and you should focus on them. What is your GPA?

This is a critical analysis about approach of codes to reduce seismic forces in terms of over strength factor. overstrength theory.PDF

waqar...thats a nice question....i would like to add that after reading what Ayesha posted...do think about the difference between an inverted and dropped beam design in ETABS....if facing difficulties post it here