Load combination

Dear All,

However I'm using Karamba for my research but my question isn't directly about Karamba. It's about structural engineering. I would be grateful if you could answer it:

I'm making some models of RC high-rise buildings to analyse them in Karamba for early stages of architectural design. Therefore I won't go into details. The overall structural layout and its approximate mass would matter in my research.

I consulted a structural engineer about load combinations. He suggested the following combinations and said that these would be enough and safe for preliminary design. I just want to double check it with you if you find it correct, and if you could provide references for it:

3 scenarios:

1- gravity: load combination = (1.2 x dead) + (1.6 x live)

2- wind: (1.2 x dead) + live + wind

3- seismic: (1.2 x dead) + live + seismic

The simulation models site assumed in Dubai. As far as I know IBC codes are valid there. Please correct me if I am wrong. Any help would be appreciated.

Best,

Replies to This Discussion

Permalink Reply by Karamba3D on February 21, 2017 at 1:02pm

Dear Aryan,

yes, normally IBC codes are used in Dubai. I am not too familiar with the IBC load combinations but are you sure that the parital safety factor for wind is unity at the ultimate limit state?

Do you consider the first eigenfrequency and deflections for assessing the usability limit states?

Best,

Clemens

Permalink Reply by Aryan Shahabian on February 22, 2017 at 3:33am

Dear Clemens,

Thank you for your reply. I consulted the structural engineer again.

1- He said that since in my research I need only a rough estimation of the total mass of the structure and the thickness of some elements, to compare three architectural alternatives with similar height and radius (the structures are cylindrical), the above mentioned combinations are for the purpose of simplification.

He provided the following part of IBC for more details as well:

_______________________

1605.2 Load combinations using strength design or load
and resistance factor design.

1.4(D +F) (Equation 16-1)
1.2(D + F) + 1.6(L + H) + 0.5(Lr or S or R) (Equation 16-2)
1.2(D + F) + 1.6(Lr or S or R) + 1.6H + (ƒ1L or 0.5W) (Equation 16-3)
1.2(D + F) + 1.0W + ƒ1L + 1.6H + 0.5(Lr or S or R) (Equation 16-4)
1.2(D + F) + 1.0E + ƒ1L + 1.6H + ƒ2S (Equation 16-5)
0.9D+ 1.0W+ 1.6H (Equation 16-6)
0.9(D + F) + 1.0E+ 1.6H (Equation 16-7)

_______________________

2- Yes I'm considering the first eigenfrequency and deflections.

Best,

Aryan

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