The lead office told us that the structural plans should be rigidly consistent with the ETABS model. And by rigid, I mean the structural model should exactly be the same in terms of the location of wall and column centerlines.
Come on let’s face the reality: you cannot really model perfectly the actual layout on the structural model. It is far too complex and it will need a lot of simplifications and rationalization in order to arrive at a solution that very nearly represent the actual situation.
But anyway orders are orders and so we need to align ‘em all vertical elements – columns and walls. All you need to do is draw the dxf’s in CAD and import them in the ETABS model. And of course as expected, the dxf of wall lines and columns will not match exactly the walls and columns in the structural model.
Luckily, we didn’t have to remodel the whole walls from scratch. We just need to maximize the use of the Move Joints/Frames/Shells option. It saved us from the horror of having to stitch back the slabs floor by floor (imagine doing this for 30 floors or more!).
Using the move option stated above, the structural modeller will save time and will minimize if not totally eliminate the hassle of drawing a new geometry especially if it is angled and not orthogonal (along the X and Y plane).
Note: You can select the nodes only and all elements attached to it such as columns, beams, slab, and walls will move as well.
For example, a footing must be moved to its final position because of the movement of the column. The footing consists of 4 separate shell elements connected by a common center point as seen in the screen shot below. It is intended that the central point of the footing to be moved beneath the column.
So the first step is to select all 9 joints of the footing. Go to Edit menu and click Move Joints/Frames/Shells option. A popup window should show this:
Click on Pick Two Points on Model and click first the point on the source object you want to move (point 1 on the figure above) and finally click on the point where you want the geometry to be moved (the point beneath the column which is point 2 on the figure). Finally the dialogue box will automatically compute and display the displacements in X and Y direction:
Note that there are instances when a value will appear on the Delta Z. Always remember that in ETABS, the z axis is the vertical axis and if your intent is to move the footing on the X and Y plane only, just set the Delta Z value to zero. Once done you can click either OK or Apply and the footing should move to its intended position:
Now that they are connected, the load transfer should be from the loads to the column to the footing base. For a final check, the central point should connect 4 shells (comprises the footing) and one column with tag C159 in this example and it was connected correctly (see Connectivity Joint Object Information Dialog Box below):
Note that you can also do this for walls. Just make sure to select all points with the same X and Y coordinates in all floors. Where walls are meshed in each floor, it is best to choose the said points on an elevation view so that you can see whether you’re missing any point at all.