Software Knowledge Base

Note ID: 000058 – Applications: SLABS4

Title: SLABS4 manual – Results - Slab Moments: Slab Moments - General

Description: Detailed notes about extracting moment results including examples

See Also:

Date Created: 25/03/2008

Date Modified: 25/03/2008

The complete set of slab bending moments is made up by the following results;

· Moments X-X

· Moments Y-Y

· Twisting Moment Mxy

· Moment Envelope X-X

· Moment Envelope Y-Y

(where X-X and Y-Y refer to the direction of the moment)

Like the deflection results, all the moment results are displayed on screen based on the Load Case or Load Combination that was chosen by the user prior to selecting the results from the [ Results ] tab on the Main Menu.

Specific results can be extracted at each node using the left mouse button while the moment results are displayed on the screen, as shown below;

Sample screen shot - Bending Moments X-X for Load Combination 1. Results at specific nodes, and a line of contraflexture

The results at the nodes above (‘-982.9’ and ‘647.0’ etc) have units of kNm per unit length (kNm/m’) or per 1.0m width. Note that the slab Mx moment is in the direction of the global X-X axis (horizontal on the screen), i.e. the slab Mx moment is about Y-Y axis.

In order to extract the total negative moment in the slab (over the column) shown in the screen shot above, the user needs to integrate over a distance perpendicular to the direction of the moment (in this example the integration points will be vertical on the screen). The tools used to perform the integration are automatically displayed in the Dynamic Tool Bar (DTB) when required, ie: when the type of results displayed can be integrated.

Sample Screen shot – Bending Moments X-X displayed for Load Combination 1, Integration Tools also highlighted

In order to extract the total negative moment over the supporting column, the steps involved are;

· Ensure the correct moment results and Load Case or Load Combination are selected

· Click on the ‘Integrate over a distance’ icon in the DTB

· Set the snapping mode to ‘Snap to Corner’

· Click on centre of the column and enter a distance or integration width (note: SLABS4 will automatically integrate perpendicular to the results displayed

· The software will then display the total sign of the moment (+/-) and the total integration width

Sample Screen shot – Integrated total Negative Moment over a supporting column

The Moment Envelope results are based on the Load Combinations defined by the user in the Load Combination Factors table, as shown in the screen shot below;

Sample Screen shot – Load Combinations included in the Moment Envelope (envelope used to design the Reinforcement)

The Moment Envelope (in X-X or Y-Y) results are available from [ Results > Moment Envelope ] from the main menu. The envelope results are split into top and bottom moments, and the outer most contour line indicates the point of contraflexture. The switch between the top and bottom moment results is located above the DTB, as shown in the screen shot below;

Sample Screen shot – Moment Envelope contour lines and switch between Top/Bottom moments

It is important to note that the Load Case or Load Combination settings that are displayed on the Task Bar are not relevant when Moment Envelope results are displayed.

The integration tools and integration procedures for Moment Envelope results are the same as the Moment X-X and Moment Y-Y results.