Analytical Strip (Moment Coefficient Method)

Analytical Strip (Moment Coefficient Method)

Analytical strip can be used to analyze and design solid slabs supported by beams or walls. The Bending Moment Coefficient is based on British Standard Design Code BS 8110-1:1997, table 3.14.

The general procedure is as follows : 
  1. Ensure the correct slab edge continuity in set in Slab Properties > Type 
  2. Click on Slab Strip icon in the Modelling Tab. Ensure "Analytical Strip" is selected in Slab Strip Properties > Type (not Finite Element)

  3. Ensure all parameters, especially the Start and End Condition are set correctly. Refer here for more details : Working with Slab Strips
  4. Draw the slab strip by clicking on 2 points - cutting through slabs supported by beams or walls. 
  5. Slab where the strip crosses will automatically be analyzed & designed. Reinforcements calculated according to Moment Coefficient Method will be shown on the screen, as soon as the strip is drawn. 

Generate slab analysis and design report for a particular slab : 

  1. Go to Design tab > Slab Analysis & Design.
  2. Select slab strip then click Interactive Design  the slab's label, slab type, dimension of slabs, slab design and analysis results will be shown. Users are able to manually adjust the slab reinforcement here. 

  3. The output of slab analysis and design can be generated in report format by clicking Report button.

Generate batch slab analysis and design reports: 

  1. Go to Design tab > Slab Analysis & Design > Click Slab Strip Design (Batch Mode) 
  2. If you want to analyse only the slabs of the current storey, then “All Storeys” box should not be checked in the “Slab Analysis and Design” dialog. If you check this option, then all the slabs in the building will be included in the calculations.
  3. Press the "Design" button to run the process.
  4. Click Design report button 
  5. If you close the “Slab Analysis and Design” window, the reinforcements will be inserted or updated (if already exist) in the plan view.

Abbreviations and symbols used in the reports when the slab designs are performed according to the Moment Coefficient Method:



The ultimate load factors are obtained using the first load combination defined in the Standard Load Combination used in the analysis of the building. Therefore, when a customized load combination is used, special care must be taken to have the first combination to reflect the correct load factors.
Span reinforcements for each slab will be selected according to the span moment calculated for that slab. For the calculation of support reinforcements, the biggest support moment of the two adjacent slabs will be selected after redistribution. After determining the steel area required in the support, the area of the reinforcements coming from the spans and passing through the support would be calculated. If these bars don’t satisfy the area required in the support, additional support reinforcement would be provided.     
Limitation: The moment coefficient method is principally for rectangular or squarish slabs. For irregular shaped slabs, example, triangular or polygon slabs, please exercise due engineering judgement; use other appropriate slab analysis and design method, such as FE Floor Analysis with floor slab meshed. 

Demo Video of the Slab Analysis and Design using Analytical Strip



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