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There are eight separate align options available for the Edit menu > Align Points/Lines/Edges command in ETABS. They are:

• Align to X-coordinate of.

• Align to Y-coordinate of.

• Align to Z-coordinate of.

• Align to X grid lines.

• Align to Y grid lines.

• Trim selected lines at.

• Extend selected lines to.

• Align selected points to.

These options are discussed in the subsections below.

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Align to X, Y or Z-Coordinate

For these options you specify the location of the coordinate that you want to align to. Then if the appropriate coordinate of the selected object is within the maximum move allowed of the specified coordinate, the appropriate coordinate of the selected object is changed to the specified coordinate.

For example suppose that you choose to align to an X-coordinate of 4 and suppose that your maximum move allowed is 0.2. Then:

• Any selected point object that has an X-coordinate be-tween 3.8 and 4.2 (in the specified coordinate system) is moved such that it has an X-coordinate of 4. Selected point objects with X-coordinates outside of the 3.8 to 4.2 range are not moved.

• Any selected line object where each of the ends of the line has an X-coordinate between 3.8 and 4.2 (in the specified coordinate system) is moved such that each of its ends has an X-coordinate of 4. Selected line objects with the X-coordinates of one or both ends outside of the 3.8 to 4.2 range are not moved.

• Any selected area object where two adjacent corner points each have an X-coordinate between 3.8 and 4.2 (in the specified coordinate system) is resized such that two adjacent corner points have an X-coordinate of 4.

Selected area objects where there are not two adjacent corner points each having an X-coordinate between 3.8 and 4.2 are not resized. Note that the effect of changing the coordinates of two adjacent corner points of the area object is to move one of its edges.

Align to X or Y Grid Lines

For these options you specify which grid line you want to align to. Then if the appropriate coordinate of the selected object is within the maximum move allowed of the specified grid line, the appropriate coordinate of the selected object is changed to be the same as the specified grid line.

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When you are aligning to X grid lines the X-coordinate of the selected object is examined and if it is in the appropriate range it is modified. The Y and Z coordinates are not affected.

When you are aligning to Y grid lines the Y-coordinate of the selected object is examined and if it is in the appropriate range it is modified. The X and Z coordinates are not affected.

For example suppose that you choose to align to an X grid line at a coordinate of 4 and suppose that your maximum move allowed is 0.2. Then:

• Any selected point object that has an X-coordinate be-tween 3.8 and 4.2 (in the specified coordinate system) is moved such that it has an X-coordinate of 4 to match the grid line. Selected point objects with X-coordinates out-side of the 3.8 to 4.2 range are not moved.

• Any selected line object where each of the ends of the line has an X-coordinate between 3.8 and 4.2 (in the specified coordinate system) is moved such that each of its ends has an X-coordinate of 4 to match the grid line.

Selected line objects with the X-coordinates of one or both ends outside of the 3.8 to 4.2 range are not moved.

• Any selected area object where two adjacent corner points each have an X-coordinate between 3.8 and 4.2 (in the specified coordinate system) is resized such that two adjacent corner points have an X-coordinate of 4 to match the grid line. Selected area objects where there are not two adjacent corner points each having an X-coordinate between 3.8 and 4.2 are not resized. Note that the effect of changing the coordinates of two adjacent corner points of the area object is to move one of its edges.

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Trim or Extend Selected Lines

These options allow you to trim or extend line objects. Recall that in ETABS to insure that a beam is connected to a girder the end of the beam should fall exactly on the girder, not some dis-tance away as it might be drawn in the building plans. If you im-port a floor plan from a *.DXF file it is likely that the beams will be drawn such that they stop short of the girders. Similarly the girders will be drawn such that they stop short of the columns.

These commands allow you to fix such things in your ETABS model.

For these options you specify what you want the selected lines to be trimmed at. Then if the end of the selected line object is within the maximum move allowed of the specified trim (extend) item, the line option is trimmed (extended) to that item.

Four different choices are available for the trim (extend) item.

They are:

• Any line object that has frame section properties as-signed to it.

• Any line object or any edge of an area object.

• Any line object.

• Any edge of an area object.

Note that the specified trim (extend) item need not fall in the same plane as the selected line objects. For example if you choose line objects as your extend item and you select a girder as the object to be extended then that girder can be extended to the line object representing the column even though the girder falls in a horizontal plane and the column falls in a vertical plane.

Consider the example shown in Figure 9-5. Figure 9-5a shows a floor plan as it might be drawn on your building plans. Note that the beams stop short of the girder and the beams and girders stop short of the columns. Also, in this example the beams stop short of the wall.

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You could select Beams 1, 2 and 3 and Girder 1 and execute the Edit menu > Align Points/Lines/Edges command using the

"Extend selected lines to" align option and specifying that the lines are to be extended to "Line or Edge" to obtain the model shown in Figure 9-5b as long as the maximum required line ex-tension is less than your specified maximum move allowed. This would give your model the correct connectivity between the various elements.

The left side of Beams 1, 2 and 3 are extended to meet the top edge of the vertical area object that represents the wall below.

The right side of Beam 1 is extended to meet the vertical line object that represents Column 1. The right side of Beam 2 is ex-tended to meet the horizontal line object that represents Girder 1.

The right side of Beam 3 is extended to meet the vertical line object that represents Column 2. The top side of Girder 1 is ex-tended to meet the vertical line object that represents Column 1.

The bottom side of Girder 1 is extended to meet the vertical line object that represents Column 2.

If you specified that the lines are to be extended to "Edge" then only the left side of Beams 1, 2 and 3 are extended to meet the top edge of the vertical area object that represents the wall be-low. No other line extensions are done in this case.

Girder 1

Column 1

Beam 2

Beam 3

Wall Below

Column 2

a) Floor Plan as Drawn in Building Plans

Girder 1

Column 1

Beam 2

Beam 3

Wall Below

Column 2

b) Floor Plan in ETABS Model

Beam 1 Beam 1

(Above) Figure 9-5:

Example of extend-ing selected lines

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Assume that the beams, girder and column are all assigned frame section properties. If you specified that the lines are to be ex-tended to "Frame Sections" then all of the extensions shown in Figure 9-5b are done except that the left side of Beams 1, 2 and 3 are not extended to meet the top edge of the vertical area object that represents the wall below.

Note the following about trimming and extending selected lines:

• If two or more specified trim (extend) items fall within the maximum allowed move distance to the end of the line then the trim (extend) is done to the item that is closer to the end of the line.

For example, suppose that in Figure 9-5 the right end of Beam 2 is within the specified maximum allowed move distance to both Girder 1 and the edge of the slab. If you select Beam 2 and specify that the lines are to be ex-tended to "Line or Edge" then the right end of Beam 2 is extended to Girder 1, not the edge of the slab, because the right end of the beam is closer to Girder 1 than it is to the edge of the slab.

• Line objects are always trimmed (extended) along their longitudinal axis.

• Specified trim (extend) items (frame sections, line ob-jects or edges of area obob-jects) are only considered if they are visible in the active window. You can use this fea-ture together with the View menu > Show Selection Only command to get additional control of the trimming (extending) of line objects.

Align Selected Points

You can align selected points to the following items:

• Any line object that has frame section properties as-signed to it.

• Any line object or any edge of an area object.

• Any line object.

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• Any edge of an area object.

When you use this option any selected point is aligned with the closest specified item if that item is within the specified maxi-mum move allowed. Specified items (frame sections, line objects or edges of area objects) are only considered if they are visible in the active window. You can use this feature together with the View menu > Show Selection Only command to get additional control for aligning points.

When checking for the closest specified item to a selected point ETABS measures the perpendicular distance to line and edges of area objects. When a point is moved to align with an item it is either moved perpendicular to the line object or edge of the area object.