Design of reinforced concrete helical staircase using Euroode2 3

[tadjou laura]

Hi

My name is Boris. A new member of the forum.

Usually in Eurocode for design of reinforced concrete theoritically we read from CHART(TABLES 177 of REYNOLDS AND STEEDMAN, 2005]. From this chart we can easily do the structural analysis or calculate the forces (vertical shear, radial horizontal shear, Axial forces, Torsion, horizontal moment, vertical moment at different angles.

Where can i find this chart please?? I Searched it on google but can't find it. please is there any document where i can get this chart from??

 

[tadjou laura]

Sir @BAretired may be is the version because i'm using Robot 2025

 

[BulbTheBuilder]

Office buildings typically have a 2-3kN/m2(40-60psf) which doesn't really sound heavy to me. Corridors will have 5kN/m(100psf).

What is the span of your beams, what are their tributary widths, are there transfer columns?
Keeping consistent beam depth / beam sizes is a good construction practice. If you need to deepen your beam for deflection then go ahead, sometimes, adding extra to reduce load onto the beam helps avoid increasing the depth.

Post a picture of your layout with dimension and beam sizes. That might help us as we can't exactly visualise what you're saying

 

[BAretired]

Sir @BAretired may be is the version because i'm using Robot 2025

Perhaps so. Can you post it using PDF or JPG?

 

[tadjou laura]

Hi Sirs;

Many thanks for the responses and answers. My apologies, i spent a lot of time to prepare this architectural and structural plans to get feedback from experts like you.

For the structural plans, there are already size. Started with presize as 300x300 for beams and columns and raft of thickness 490.

The foundation below is a raft foundation, as from image send before the raft has a punching shear failure in localized distances of some columns.

Hope to get a feedback, and if any detail info want from the project will very happy to answer. Here are the links for the plans sent

Many thanks

Boris

 

[tadjou laura]

architecture

 

[tadjou laura]

Structure

 

[tadjou laura]

Another thing is the conference room at the G+3 floor, no columns are supposed to be passed and we've decided to use rc solid slebs .

Simulated in the Robot, even (300x1000)mm column, not only can't support that amount of load but there a large deflection of 80mm.

 

[BulbTheBuilder]

I'm actually writing my end of year project.

Is this your end of year project?

 

[BulbTheBuilder]

First, review your structural general arrangement. You have longer span with shallow depth. I am assuming this isn't Post-tensioned (PT) slab/beam system, I don't know if PT is done a lot in Cameroon, but I want to highly doubt it.

What grade of concrete are you using? I anticipate something like 35Mpa for this structure with high yield Grade 500Mpa reinforcement. Anything lesser, then you'll need more columns than before. If this is a schoolwork, you can simplify it by keeping your max beam length at 6.5metres. Your slabs might be around 175mm but will work.

Regarding the foundation, what is the soil bearing pressure? What are the environmental conditions? I see basements, have you decided on your retaining wall?

 

[BAretired]

architecture2.rar and structure.rar are WinZip files. I cannot open them unless I buy WinZip, which I do not want or need. Put the bloody drawings out in a different format.

Actually, I don't think we should be helping you at all if this is a school project. You are expected to seek the information for yourself.

 

[BulbTheBuilder]

By the way, BAretired, WinRar is a free even after its 40-day trial. You might want to look into that if you ever have to purchase a ZIP app.

I did extract the file, but it is a lot if that's actually a school project. I think OP's first language is free so I will give her a pass. Tadjou laura, kindly attach PDF, JPEG, PNG files to post on this forum so other can easily access and assist you. Also, what's the scope of your project work? Are you doing both architectural and structural aspect? Is it a group or individual work?

 

[BAretired]

@ BulbTheBuilder,
Well, I tried to open those the .rar files and WinZip asked me to register and pay some sort of a fee. I didn't look into it beyond that, but I really don't need the hassle, so unless we get some useful information, I'm out of here.

 

[tadjou laura]

Hi Sir @BulbTheBuilder

My Sincere apology for the lateness, was actually working and reviewing the GA as you suggested Sir @BulbTheBuilder. The retaining wall are located at the East and south facade of the project. The engineer that's constructing the project uses an fck of 20Mpa, but for this Master thesis(end of year project) that i'm working alone, decided to go for fck=30Mpa. The environmental class, choose XC3, because the raft might be sometimes exposed to salty rain water and XC2 for other structures. The soil bearing pressure was proposed by the geotechnician as Ks=6318KN/m2/m with SF3 and admissible sigma SLS of 160kN/m2.

For the slab, the architect proposed 20cm and the shallow depth is due to sizing in robot, because the deflection in the slabs was very high especially in the G+3 and G+4 levels at the locations of the conference room. So i didn't had any choice because went for RC solid slab. Except there's another solution Sir.

Thanks

Boris

 

[tadjou laura]

Hi Sir BAretired

M Sincere apology, the Master thesis will be done in september so hope you could forgive me for this lateness please.

Done the general arrangement already except if there's any correction. Here are the architecture and structural pdf file attached. preparing to merge the PDF file to send

Thanks

Boris

 

[tadjou laura]

section, elevation

 

[tadjou laura]

Floor plans basement to G+4 + parapet in order. The columns inserted are not the real column.

 

[tadjou laura]

GA plans, in order from floor basement to parapet.

 

[tadjou laura]

Please if there's any correction, suggesttion or any info. Will be happy to respond as quick as possible Sirs.

 

[tadjou laura]

Haha, yeah Sir @Bulb The Builder, post tension slab beam system is used but in bridges in Cameroon. For most of high standing building, we usually use composite slab system.
But for this project the engineer use 20Mpa, surely to keep some money in the pocket lol.

 

[BulbTheBuilder]

so unless we get some useful information, I'm out of here.

I understand!

Tadjou laura, this is an end of year project so presentation of files/documents is important. People should easily get the information from documents you submit. You can combine files into 1 PDF with your comments/concerns so others can review. People have busy schedule so please make it easy for them to help.

I have had a very long day and it's quarter to mid night here so I will review the new attachment tomorrow. But I will leave you with some comments to think about.

The retaining wall are located at the East and south facade of the project

What about West and North? Don't you have two levels of basement?

The engineer that's constructing the project uses an fck of 20Mpa, but for this Master thesis(end of year project) that i'm working alone, decided to go for fck=30Mpa.

20Mpa was never going to work, 30Mpa is better. Since you are working on it alone, can you modify layouts to add extra columns? You can make them round columns if they are in open spaces.

The soil bearing looks good, you shouldn't have foundation issues. For a school project, if you don't know how to use Robot don't stress. Take a strip where you anticipate higher moments and do I hand calc check. If your loads are higher than you can bet punching shear would control. You can pick a typical column and check shear stresses for 3m thick raft.

For the slab, the architect proposed 20cm and the shallow depth is due to sizing in robot

20cm is fair. You can use 16mm for the design with 12mm for shrinkage and temperature. I don't use Robot but you should be able to have control of your modelling.

because the deflection in the slabs was very high especially in the G+3 and G+4 levels at the locations of the conference room. So i didn't had any choice because went for RC solid slab. Except there's another solution Sir.

Yes, I am not surprised about the deflection. Yours are really big. You might want to consider waffle slab if you intend to keep those bay sizes.