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Thanks for everyone's comments. This is a slender column at a end bay and there is no column above. The amplified moment is giving me hard time to keep the desired column size. I agree not designing for the moment could have too much detail work and still probably be too risky.

Thanks PAStructuralPE. Is there anyway I can get by for the gravity moments, like use a cross type dowels or use dowels in the middle of the column?

I am designing a concrete column and would like to design it for axial only. we have enough shear wall to take the lateral load but in reality the column will be cast together with beams and dowel bars and there will be moment at connections. I want to assume pin connection in the model because...

Brad, I appreciate you and everyones input here. This is a great forum of us engineers to bounce ideals and share opinions. Can you tell me the price you got from the contractor for demoing topping slabs and, if you don't mind, what was the location of the project you mentioned. I am in Kansas...

Brad, We need to increase the live load capacity of the slab by 40%. the 2 way slab will have both positive and negative moment increase demands in two directions. The FRP requires sand blasting on both top and bottom and we probably still need to take out the existing 5" nonstructural...

The current 9" slab has a 5" non-structural (non-reinforced) topping slab on it. we will remove it and replace with structural topping. We will add heavy reinforcement on the top, maybe #5 @ 12" or 8" for negative moment increase. the positive moment is increased by the increased "d" for the...

I need to strengthening a existing 9" thick 2-way slab with new 5" topping slab on it to increase the slab capacity (to increase the "d" for bending and shear). We are going to short blast the existing slab and add a bonding agent and probably add some mechanical dowels. Is there any concerns we...

Kris, Thanks for your input. the manufacturer's opioning was disregard the internal PT force for strength design. With everyone's input here I think we are clear a strain compatibility analysis is required with the PT stress considered.

BA, Thanks for the in put. I just couldn't get my mind strait on this issue. If the concrete cracked and only 2" for stress block in compression, the PT force still will increase the concrete compressive stress in the stress block. This could: 1. reduce the capacity of the section 2. Might...

Thanks for the reply, are you talking about PCI hand book or something, I couldn't find it?

I am designing a Hollowcore slab cantilever 7 foot out. I need to check both service and strength. I think I should design the bending strength of the section at cantilever for 1.2D+1.6L+1.0(P*e) with mild steel on top. the hollow core provider think for strength design we don't need to add the...

I had noticed 14.1.1. I just wanted to know why whould the code treat cantilevel walls and top restrained walls differently.

Civilperson, Thanks for your inputs. I think what I am trying to say is both the cantilever and top restrain retaining wall has bending in the wall. The only difference will be tension on different face and the top restrained wall might have axial loading on it. I thin k the ductility concept...

Yes, We can design the wall for whatever moment based on the the actual conditions and resonable assumptions. But do we need to check for minimum reinforcement for bending per chapter 10, which ensure no brittle failure of the wall.

civilperson In a simple span model, the max moment will be in the middle hight of the wall and it will be always bending toward the basement. We still don't want a brittle failure in the wall.

ACI require Cantilever retaining walls to be designed per Chapter 10. This has higher minimum vertical reinforcement requirements than section 14.3.3. What if I have a basement wall retaining soil. My understanding of the code is it goes to section 14.3.3 for minimun reinforcement. But I think...

Thanks DaveAtkins, You are right, both the DD and EMF method are the same.

Thank for all the replies again. OK, I figured out that for the Direct design method (ACI 13.6), it's not design for twice. Since we have the column strips take a portion of the loading (say,75% ). if we have one way load transfer, we will have 100% on the column strip plus 100% from the...

Thanks for the reponse. But in one way slab design, we are desigining for one load path for the area distributed load. In two way slab design, seems we are designing for the same load for two load paths (two directions), 100% of the load each way.

I have a question about two way slab design. ACI 318 use the area loading design column strips and middle strips in one direction and then use the same loading design the other direction. Are we designing for the same load twice? Any thinking about this. Thanks a lot.