How to check and include the P-delta effect using ETABS software (Lec17)

[@civilengineeringwitharas4776]

Why 0.5 of Live load not Total Live load ? Any Code reference about it ? thank you

[@Eng.tarekyoussef]

Check ASCE 7-10, Commentary Appendix CC for serviceability considerations or check the end of this video "Load combo for checking drifts": kzbin.info/www/bejne/qITGmYCro8uLntEsi=F-ip5p147RvyvO_S

[@samanadel1125]

bro ur the best

[@akshaythakur2395]

sir, can we get to know what is refernace for 1DL+0.25LL as multiplier for P-Delta

[@Eng.tarekyoussef]

P-Delta effects are generally evaluated under service load conditions because these loads reflect the actual conditions the structure will experience during its lifetime. Service loads are the unfactored loads, which include dead loads (DL) and live loads (LL) without any safety factors applied. In structural design, factored loads (which include safety factors) are used for ultimate strength design to ensure safety under worst-case scenarios. However, for evaluating P-Delta effects, which are sensitive to actual displacements and deformations under normal use conditions, service loads are more appropriate. Why 1DL + 0.25LL? The use of 1DL + 0.25LL as a load combination for P-Delta analysis is intended to provide a reasonable estimate of the service load effects on the structure. The factor of 0.25 for live loads accounts for the likelihood that not all live loads will be present simultaneously and fully across the structure. This partial live load factor reflects a more realistic scenario of load application during the service life of the structure. This approach is supported by design standards such as ASCE 7 and AISC 360.

[@akshaythakur2395]

sir, thanks for your reply!!!

[@talfeg]

hi. can please clarify why you choose Beta= 0.5 not equal to1 as a conservative value as mentioned in the Code ?

[@Eng.tarekyoussef]

I was just trying to explain the importance of beta value. sometimes we can take beta=1 (conservative case), however in some cases taking beta=1 will leads to a high value of theta. Therefore, we need to go into details in computing beta value to be more accurate.

[@RCX198]

@@Eng.tarekyoussef Greetings, Could you explain how the beta factor is calculated so as not to use 1.0 or do you have any bibliography on the calculation of said beta factor? Thank you.

[@moh.rizkypradana2775]

sir, what if the P value in story force is empty? is there anything that needs to be added? please confirm sir

[@Eng.tarekyoussef]

You should have "P" as it corresponds to the design vertical loads (gravity loads exist in all floors). In this video I used the load combo of "DL+0.25LL" to get P.

[@khalilothman5638]

why we should use static forces only to check P-Δ effect?

[@Eng.tarekyoussef]

It is much preferable to check the P-delta effect using a static force (ELF) because as shown in ASCE the design story drift should be that one occurred simultaneously due to the applied load. The design story drift obtained from RSA method is the combined response (combination of several modes using SRSS or CQC combination rule), therefore the design story drift obtained from RSA is the combined response of several modes and not occurring simultaneously due to the applied load.

[@NguyenSon-hx6pj]

really appreciate !

[@jichunqin1990]

Sir, if we use response spectrum method, which period should we based? The first one, the second( cracked section) or the third one( with p delta)?

[@Eng.tarekyoussef]

the third one (with P-delta)

[@jichunqin1990]

@@Eng.tarekyoussef if use response spectrum method to analyze building. To check the p-delta effect, should the story shear and drift in that formula be from the equivalent force method? I.e. p delta effect result is same for ELF and RSA?

[@Eng.tarekyoussef]

@@jichunqin1990 It is much preferable to check the P-delta effect using a static force (ELF) because as shown in ASCE the design story drift should be that one occurred simultaneously due to the applied load. The design story drift obtained from RSA method is the combined response (combination of several modes using SRSS or CQC combination rule), therefore the design story drift obtained from RSA is not occurring simultaneously due to the applied load.

[@jichunqin1990]

@@Eng.tarekyoussef Thank you. Very informative.