Concrete Shear Wall Design

[bertiskorny]

Hello,

I'm a new structural Engineer. For those of you familiar with ETABS v9, I need help designing a concrete shear wall (general).

1) Let's say I have a 2 bay shear wall going up 6 stories. I can label the left piers P1 and the right piers P2, or I can label the piers P1-P12, or label all the piers as P1. Assuming the walls are similar, and I want to utilize "general reinforcement" or "uniform reinforcement" (Design -> Shear Wall Design -> Assign Pier Sections for Checking -> ) what is the best way to label the piers? I do not want the same reinforcement at each floor unless necessary (I.E. for the 1st floor, I can have #10 @ 12" and the rest of the floors at #8 @ 16", etc.).

2)Is it really that tedious of a process to run an analysis then "Design Check of Structure" (Design -> Shear Wall Design -> Start Design/Check of Structure)? For example:

a. Assign Pier Labels for walls (For my structure I would have 12 individual piers, 12 possible walls?)

b. Define Pier Sections for checking (again a possible 12 piers)

c. Run analysis and Design/Check of structure

d. Inspect each individual wall (12 possible) to see if reinforcement satisfies flexure and shear?

e. If wall does not satisfy, unlock and adjust reinforcement accordingly (12 possible again).

 

[WillisV]

1. If the shearwall is continuous in length at each level (by 2 bay I assume you just mean it is a single wall that is 2 bays long) then you can simply assign one pier number to every single piece of wall in the building. ETABS considers each floor independently so assigning the same pier number to level 1 as level 2 will have no effect on the design.

If the shearwall is discontinous at each floor (2 pieces) then you would want to assign a different pier label to each piece of wall.

I would also recommend splitting the wall into pieces that are no more than about 1.5 times tall than they are wide to provide a better mesh.

2. Your process appears correct.

 

[jen4950]

I use uniform reinforcing and assign a single pier label for a continuous segment of vertical shearwall (as WillisV mentioned, ETABS splits it up at story levels)- and in a nutshell I have written a script that boils down the design data outputted from ETABS in a spreadsheet, and optimizes the reinforcement based upon specific criteria- I digress..

If you'll notice on the printed output (text file that I import) it gives you a required reinforcement ratio, and the controlling load cases- I use the required uniform reinforcing ratio from the design module as a starting point (50/50 of that steel in the wall boundary zones, spaced 0.80L apart as a rule of thumb, my script actually goes in and works backwards with the required spacing.

From that you check your boundary zones, flexure and shear with your as specified section; if it doesn't work, add steel as required; if it still doesn't work when you get to about 6% steel, reconsider your model and the configuration.. If it still doesn't work, check your loads.. if it still doesn't work, pack it full of #18 DWIDAGS 6 story, you should be fine with 8's and 9's at 12-

I'm working on a rather large (4M sf in our tower alone; 18M total) and incredibly irregular 65 +/- story, and my rule of thumb is steel is cheap, mistakes and omissions are not- so if there is any question, run the segment by hand (120 individual wall segment geometriesd in this buidling) and make sure you have enough steel. On this project, I'm not using anything less than #7's at 12 across the board.