Finite Element FE Strip
Slab Strips for the Finite Element Analysis of Solid Slabs Supported by Beams (Span Strip)
As an alternative to the Moment Coefficient Method, “Finite Element Analysis” can be used. To define a slab strip for the “Finite Element Analysis”, the “Finite Element Strip” must be selected, and the “Span Strip” option should be selected. Similar to the Moment Coefficient Method, these strips must pass through the slabs supported by beams and walls. After drawing all strips, you can start the analysis of the slabs by using the "Building Analysis" option or “FE Floor Analysis” option in the “Analysis” ribbon menu. (See “Finite Elements Floor Analysis” chapter for details)
Span reinforcement is calculated according to the maximum moment found in the “Span Zone”. Span Zone is L/4 distance from each axis defining a slab as shown in the sketch. Similarly, support moments are taken from the “Support Zone” which is the L/4 distance in each side of a support. After determining the maximum moment in span or support, ProtaStructure calculates the reinforcement required accordingly.
Fixed Band Strip for Flat Slabs
When you prefer to put a single top and bottom steel along the strip, "Fixed Band" strips are ideal solution, especially for complex plans that Span Band or Support Band strips cannot be used or for small buildings like villas.
Extents of the "Fixed Band" to the left and right side of the strip line is provided by the user. Following the analysis of the floor, all nodes within the region covered by the strip will be scanned and a single maximum positive and a single negative moments are returned (that creates bending along the direction of the strip). Based on these moments a top and a bottom steel is selected and placed along the strip.
To define a Fixed Band Strip, after checking the “Finite Element Strip” box in the Slab Strip Properties, select the “Fixed Band Strip” option from the “Strip Menu”. Then, the strip line can be dragged through the slab panels in the floor.
Band extents can be defined either by entering the left and right distances to the "Left Extent" and "Right Extent" fields, or alternatively by picking a point to the left or right side of the strip line after pressing "Pick Point" button.
Picking points may be a more preferred method of providing strip extents when the strip will be extended up to an existing axis line or a slab edge. You can use "EndPoint" or "Nearest" snap modes before picking a point on the reference line. After picking a point, you can apply the modification to the strip by pressing the "Update" button.
Steel cut length can be adjusted using the "Slab Steel Bars Cut Length" field located in the "Steel Bars" page of the "Slab Design Settings" form.
The FE fixed band strip can only be used if cut across slabs with the same thickness. The reason is the design will only detect the slab thickness nearest to the first end of the strip. If you have many slabs with different thicknesses, then do not use the FE Slab Strip. Use the other method of design using the As required contours as outlined in the Flat Slab Training Manual
Tutorial Video of the Slab Analysis & Design using FE Strip
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