Omer Ahmed

Hi, Can anyone tell me if the below calculation will be transposed (C and D values) for Water Load acting on Mushroom or Bottom Cone Tank. Please see reference images for calculation (for rectangular tank) and model. Thanks.

Thanks Hamza for referring to the useful material.

I am drowning and you're defining the water 😃

Thanks Babar for referring me to the Code... also a bit change in plans and I have changed it to a basic RC frame structure with Masonry fill walls... Any chance you can guide me to the right Code (preferably with pages) or notes where I can find the formulas for determining the Permissible Shear Stress, T & C Stress and Axial Forces, Max. Bending and Max deflection so I can compare the software determined values with the Max./Permissible ones. I am using ACI 318 as design code. Thanks.

Dear all, I need some help with masonry structure design which I am working on for proposal to the World Bank for funding for disaster resilient houses for flood affected areas. Deadlines given to me are very strict so I am just unable to grasp onto the design of Masonry Structures in detail w.r.t. ACI design code. Currently I have been able to make a basic model on ETABS (v18) and have to check my results (which are relatively simple for common RC structures) however for Masonry structures permissible limits I am just unable to find in ACI Code. Any chance someone can simplify those limits for me for me please? like any notes, or on message, related page numbers etc. Also if any expert can spare some time and check my model for any potential mistakes because it's been a little while since I used this software. P.S. I am working for a Public Company so there is no financial benefit whatsoever and is more of a voluntary support which my company is providing for flooded regions. Thanks for the read.

Hi all, I need some help with retaining wall design. How seismic factors kv/kh (as in UBC97) or cv/ch (as in BCP) are calculated? also how to develop relation between seismic zone of BCP and UBC97? I mean Islamabad/RWP is classified as Zone 2B (PGA value: 1.6-2.4) however same city is classified as Seismic zone 4 in UBC-97, now the problem is that modern software uses IBC so I can used data of UBC97 but how do I find equivalence of seismic zone? Many thanks

@waqar saleem Thanks for the answer to my first question, as for my second question what I mean to ask is how come there is too much variation for Time period in the same building? Once, Time Period is used in Seismic Loading data (value = 0.030 for concrete structures calculated by program- FIXED value!) and then there's Time period table which we usually get as an Output ( from tables or Mode shapes) after analysis which is way higher than 0.030 and comes out to be around 1 sec for 8 story RC building. Are these both different time periods or the same? why there is so much difference in the values? Is "Fundamental Time Period" differ than the "Time Period"? Thanks

@Badar (BAZ) Thank you for your answer. May I ask how we can differentiate between both the time periods? how do we know which one is to be used and where?

I was just looking at ACI/ASCE method for seismic design and had a general question about this new spectrum analysis method. Quest 1 : As it says in the code to use values of (SA 0.2 sec, SA 1sec) which means generalized Time periods are taken as 0.2 for short and 1 sec for tall buildings for given site. Why these time period values are generalized? Isn't it very common for a structure to have a time period way greater than 1 sec?. How we design for buildings having more than (say) 30 stories if we restrict its time period to just 1 sec (maximum)? Quest 2: What is difference between fundamental time period (usually varies from 0.7 to 1.X) which we find as a result, and the one we use in the ETABS seismic data (i.e. 0.030 for concrete)?

Just found an amazing website with lectures on Structural Dynamics and Earthquake Engineering in Pakistan. https://structurespro.info

Can someone please explain why we normally prefer Fixed beams in high rise buildings/structures? Does Fixed beam performs better than Simply Supported beam?

Normally we assume base of a structure to be Hinged or a Pinned base, my question is how does moment resists in Pin/Hinge based structures? where does moment transfers from sub-structure if foundation is isolated and not fixed to the ground i.e. with piling etc.?

Thanks for your help!

@Simple Structures Nicely explained. Pardon my ignorance but could you please explain how moments are resisted from foundation/footing if we assume base to be behaving like a pinned/hinge support?

@Ayesha Pardon my ignorance, so I used to opt for UBC since it have earthquake zones of Pakistani cities. Does IBC or ACI have that as well? The problem with UBC is that it doesn't come in every version of ETABS. I am familiar with Eurocode and ACI but do I need to feed earthquake zone data in Etabs as well if I go with them?

Normally when we display Bending moment/ Shear Force diagram of structure in ETABS, it is shown against some specific load cases or combinations, against which case/combination we should be checking it?, for instance if I plan to calculate steel reinforcement say using Moment Diagram? Please find attached screenshot. Many Thanks.

@Muhammad Hashmi Hi, I am not sure if you understand my question asked in the replies section above.

@Badar (BAZ) @Ayesha thanks for your replies. So I am guessing auto-generated load combos are fine as long as we double-check factors from the codes. I have one more question here, so If I use ACI-318 as a design preference code and UBC-97 for Wind and Earthquake loads, What do I do with the earthquake load factors in Load combinations? I read it somewhere that we need to multiply all the load factors of combos with the Earthquake load in it with 1.1 (as per UBC-97). Can someone please confirm if that's right? As for the Foundation design i.e. Isolated footing, what I mean to ask is that in order to design it (after finding the area of footing), I am going to need a Load and Moment value from super structure which it will be designed to resist. I have attached a screenshot below ( please ignore the values/results) what I want to know is that there are different Load Cases and Combos in Base reaction table, Should I pick the maximum value from of FZ from the table? assuming that we have a Fix base, which Moment value I should pick from the table which it will be designed to resist? Many Thanks.

I am so happy to finally find this phenomenal platform to ask questions from professionals! So I used to work in a private company in Lahore where we would use auto-generated load patterns in ETABS v9. After my MSc from UK I just had an interview at another firm last week where I was embarrassed to know that we should manually generate load combinations instead of using system generated combos for frame design! Now this got more confusing when I saw some YouTube videos where they defined load patterns manually using UBC97 (which is an easy case since it have just 5 load cases I think) but since ETABS v18 doesn't come with UBC-97and ACI load cases have like 19 load cases, (1) should I put all 19 cases manually? (2) What is really wrong with auto-generated frame combinations? why some people on YouTube and interviewer said we have to put them manually? (3) Suppose I need to design a foundation and for that I display Base Reactions after analyzing the structure, against which load combination I should be seeing the values of base reactions? Will it be the one with the maximum value of Pz, calculated from Load combination provided/ generated before? (4) Can we mix multiple design codes in 1 model? I mean what if I use UBC-97 (say in an older version), can I use ACI as a design preference and for Load combination as well? because it confuses me that older versions of ETABS doesn't come with UBC-97 as a design preference code but surprisingly it still have UBC-97 in defining load patterns where we put Dead, Live, Earthquake and Wind load data etc. Since the system allows us to pick different codes at different staged, does this mean there will be no serious effect on results? Many thanks for reading this. Please let me know if there is a need of screenshots to answer.