Two Way Slab Design Spreadsheet

The CivilWeb Two Way Slab Design Spreadsheet is an advanced spreadsheet for the design of two way concrete slabs. The spreadsheet can be used to complete all the calculations required for a design in accordance with BS EN 1992 or BS 8110. The spreadsheet completes the calculations instantly and handy design tools show the designer at a glance exactly where the slab design can be improved. This can save the designer hours of detailed design work on every two way spanning concrete slab and ensures that every design is perfectly optimised.

The CivilWeb Two Way Slab Design Spreadsheet can be purchased at the bottom of this page for only £20. The Concrete Slab Design Bundle includes the One Way Slab and Two Way Slab Design spreadsheets as well as our Beam Analysis and Slab Analysis spreadsheets for only £30. Alternatively the Two Way Slab Design Spreadsheet is included in the Concrete Design Suite which includes all of our reinforced concrete design spreadsheets. This is our best value design bundle and can be purchased at the bottom of this page for only £50.

Two Way Slab Design

Concrete floor slabs are very commonly used in all types of buildings and structures. This includes concrete car parks, buildings of all types and marine structures. This is because reinforced concrete is cost effective, durable and versatile. The ability of concrete to take any shape allows the steel reinforcement to be used only where it is needed which reduces costs, and the concrete cover provides shear strength, durability and fire protection.

Concrete slabs can be either installed insitu or precast units can be used. In some cases a composite approach is taken where precast concrete planks act as permanent shutters for the instu poured slab above.

In some cases there can be tens or even hundreds of slabs in a single building with slightly different shapes, spans and loading conditions. When these slabs are designed by hand it can be extremely time consuming to design and optimise each slab individually. In these cases a simple design spreadsheet such as the CivilWeb Two Way Slab Design Excel Sheet can save days of design work and tens of thousands of pounds by optimising each slab design.

Please note that this page refers to floor slabs supported on beams or columns. This page does not deal with ground slabs supported on underlying soils. For pavements and concrete road of all types please see our Concrete Road & Pavement Design section. For ground slabs acting as foundations please see our Raft Foundation Design page.

One way spanning slabs simply span the distance between two parallel beams. This can be analysed as a simple beam using a beam analysis spreadsheet such as the CivilWeb Beam Analysis Suite. One way spanning slabs can be designed using our CivilWeb One Way Slab Design Spreadsheet. This is included in our Concrete Slab Design Bundle which can be purchased at the bottom of this page for £30.

Two way spanning concrete slabs are slabs supported on four columns with one at each corner. This supporting arrangement means that the slab must span in two directions, both X and Y. This leads to significant bending moments and shear forces which must be resisted in both directions leading to double reinforcement in the slab. In many cases the slabs must resist both sagging and hogging moments leading to slabs with double reinforcement in both the top and the bottom of the slab. This can lead to very heavily reinforced sections.

The analysis of two way spanning slabs to determine bending moments is complex. This is due to the fact that bending in one plane affects the bending in the other. However a simplified method of analysis was presented in BS 8110 to estimate with reasonable precision the maximum bending moments, shear forces and support reactions which can be expected from two way spanning slabs. This method was used to create the CivilWeb Slab Analysis spreadsheet. This easy to use analysis spreadsheet is included in our Slab Design Bundle which can be purchased at the bottom of this page.

Two Way Slab Design - Inputs

First the designer must enter the loading conditions acting on the slab. The CivilWeb Two Way Slab Design Excel Sheet allows the designer to enter any combination of sagging and hogging moments and shear forces taken from a separate slab analysis program such as the CivilWeb Slab Analysis Spreadsheet. The Concrete Slab Design Bundle which can be purchased at the bottom of this page includes our Slab Analysis Spreadsheet.

After the loading conditions have been entered, the designer must now input an initial trial slab thickness. This initial thickness can be taken from experience of similar slabs designed in the past or simply guessed, this can be changed after the initial analysis. The spreadsheet completes the initial analysis based on this thickness and determines the validity of the design.

The CivilWeb Two Way Slab Design XLS then presents a design graph which shows the designer the results of the analysis for any thickness of slab. This shows the designer at a glance exactly what the optimum slab thickness is to minimise steel area or to minimise concrete depth. This saves the designer from having to complete the full analysis calculations dozens of times in order to determine an optimum solution.

After the designer has determined the thickness of the slab, next the spreadsheet can be used to design the reinforcement required. The spreadsheet calculates the reinforcement required in both the X and Y directions for both the top and bottom of the slab. The spreadsheet includes our unique reinforcement picker tool which allows the user to complete even the most complex reinforcement design in minutes and ensuring that the most economical bar sizes are used. This design is completed in accordance with either BS EN 1992 or BS 8110.

CivilWeb Two Way Slab Design Spreadsheet

The CivilWeb Two Way Slab Design Spreadsheet is a simple to use and powerful spreadsheet for the design of two way concrete slabs. The spreadsheet completes all the required calculations in accordance with BS EN 1992 or BS 8110. The spreadsheet also includes unique analysis tools including the reinforcement picker tool which allows the designer to complete a fully optimised design in minutes. This saves many hours of detailed design work on every two way slab design and ensures that every slab is optimised to minimise costs.