Software Knowledge Base

Note ID: 000069 – Applications: SLABS4

Title: SLABS4 manual – Results – Reactions: Static Analysis

Description: Detailed notes on extracting reaction results by Static Analysis

See Also:

Date Created: 25/03/2008

Date Modified: 25/03/2008

The column and wall reactions can be calculated by three alternatives methods:

Static Analysis

Contributory Floor Area - Basic

Contributory Floor Area - Advanced

During the analysis SLABS4 will evaluate the reactions by two methods: Static Analysis and Tributary Area Method.

The Static Analysis approach should be used for slabs supported by R/C columns and walls, where there is proper frame action. The Area Method provides more realistic values for a slab predominantly supported by masonry walls, when the frame action is not present.

The axial load calculated by the Static Analysis in the supporting columns and walls can be displayed by selecting [ Results > Reactions- Static Analysis ] from the Main Menu. Like other results, SLABS4 will display the results based on the Load Case or Load Combination that is selected by the user prior to displaying the results. The screen shot below shows the reactions in the supporting elements for the Live Load case only;

Sample Screen Shot – Static Reactions for the Live Load Case

The bending moments in the top and at the bottom of the columns are given in the local x and y directions separately. If the angle of the column section in plan is equal to zero, then the local x axes is parallel to the global X axes. The bending moment Mx is acting in the direction parallel to side A of the column. The bending moment My is acting in the direction parallel to side B of the column, as shown in the figure below;

Column Results are given along the Local Axes

In a SLABS model the top of each column is attached to the slab and the bottom end is attached to the structure below.

The column fixity can be set to ‘pinned top and bottom’, ‘fixed top and bottom’ or ‘fixed top - pinned bottom’. The type of fixity can be set independently for each column in the model by selecting the appropriate option from the property table. If a pinned support is selected there will be no bending moment results for those columns.

Sample Screen Shot – Property window for column elements, fixity options are highlighted

A tabulated report of the Static Analysis reactions is generated by selecting [ Reports > Reactions – Static Analysis ] from the Main menu

Sample Screen shot – Report showing reaction results by Static Analysis

Note: The moment load is not included in the calculation of the reactions when Floor Area approach is used. The Static Analysis method will only include the effects on the slab due to the moments.