ACI:What are the factor of load cases in analysis of piles 2

[OSE]

Hi All,

I am working in project designed by ACI.

With members of the body structural part( slab, beam, column) I used combination with factored load (these combination are shown detailly in ACI).

to calculate the numbers of pile, I want to use allowable stress design (in which Force at top of pile compared with allowable capacity of pile), and use combination with unfactored loads. But I can not find provision showing detailly about these combination in ACI.

Could you kindly please give me a detail table about these above combination, for example:

1. f1D+f2L;
2. f3D+f4L+f5W;
3. f6D+f7L+f8E;
...
with f1=; f2 = ...

I am looking forward to hearing from you

 

[DaveAtkins]

D + L
D + 0.75L + 0.75W
0.6D + W
D + 0.75L + 0.75(0.7E)
0.6D + 0.7E

With these load combinations, a 1/3 increase in allowable capacity is not permitted.

DaveAtkins

 

[OSE]

Thanks DaveAtkins!

Your counsel are highly appreciated.

One more question:
I found in IBC that "when having more than two or more transient load act simultaneously with the dead load,IBC 1605.3.1.1 permit a 25% transient load reduction-> have factor = 0.75 in these cases. And I found the same in ACI standard;

But: About a 40% reduction of dead load in combination (0.6D+W, 0.6D+0.7E), I only found in IBC, did not in ACI;
Could you kindly show me:Where in ACI say about this reduction or where in ACI permit use IBC code (because in my project I have to use ACI code)

I look forward to hearing from you

 

[OldPaperMaker]

OSE,

Chapter 8 (of ACI318-08), Section 8.2, defaults to ASCE 7. Chapter 2 of ASCE7,"Combinations of Loads" calls out the Basic Combinations in 2.3.2. IBC Section 1605.3 is similar to ASCE7.

I hope that this answers your question.

 

[hokie66]

OSE,

In the two cases you asked about the 0.6D does not represent a 40% reduction in dead load. Rather it is a 40% reduction in the stabilising effect of the dead load against the wind or earthquake load. In other words, watch the signs.

 

[DaveAtkins]

ACI would not have a 0.6 factor anywhere, because concrete is designed using ultimate strength design, not allowable stress design.

DaveAtkins

 

[OSE]

Dear All,

Thanks for your answers. They make me understand clearly about load combination.

I wish that we can discuss more in future.

With very best wishes,

OSE