Differential Settlement Calculation

Differential Settlement Calculation

Differential settlement describes the difference in settlement between two points in the same foundation or building. Total settlement is often not much of a problem as long as the whole building settles at the same rate. Differential settlement of the foundation however can be much more damaging to the buildings structure as this imposes new stresses on the buildings structure and facade.

Differential settlement can lead to unsightly cracking in minor cases and even structural damage or collapse in extreme instances. This is why an estimation of the differential settlement of the foundation as well as the total settlement is often required.

Differential settlement is caused by two main factors. The most common cause is when there are variable ground conditions underneath the building, leading to some parts settling more than others. Where this is the case the differential settlement can be estimated by calculating the total settlement for each part of the structure and comparing. This calculation can be done using other spreadsheets included in the Foundation Settlement Calculation Suite.

Differential settlement can also be caused when a moment is present in the foundation. In this case a single foundation will be subject to differential settlement from one side to the other. When a moment is present one side of the foundation will become stressed to a greater degree than the other. This will cause differential settlement of the foundation. Bowles derived a simple way to estimate this differential settlement occurring across a single foundation which the CivilWeb Differential Settlement Calculation Spreadsheet uses to estimate the differential settlement.

Differential Settlement Calculation - Inputs

First the designer must input the geometrical properties of the proposed foundation. This includes the foundation length and width. These parameters are used to determine Bowles’ Depth Factor which the spreadsheet calculates automatically.

Next the designer must input the moment acting on the foundation and the soil design parameters. These include the soil’s elastic modulus and poisson’s ratio. These parameters can be obtained from testing of the soils though it is usually adequate to use typical values based on the soil description or from experience of the site.

The CivilWeb Differential Settlement Calculation Spreadsheet then calculates the differential settlement which can be expected across the foundation due to the applied moment.  The spreadsheet also  produces a unique analysis graph which shows the designer at a glance exactly what levels of differential settlement which can be expected from differently sized foundations.

This saves the designer from complete numerous iterative calculations in order to optimise the design to suit a particular level of maximum differential settlement. Completing these calculations by hand can take many hours of work. The CivilWeb Differential Settlement Calculation Spreadsheet completes all the calculations instantly allowing the designer to optimise the design in minutes.

The CivilWeb Differential Settlement Calculation Spreadsheet provides a quick and easy way to analyse the potential differential settlement from the moment applied to the foundation. The spreadsheet does not estimate any differential settlement from a change in soil properties along the length of the foundation. In these cases the differential settlement can be estimated by completing a foundation analysis at  one end of the building and then completing the calculations again  for the other side. The CivilWeb Settlement Calculation Suite includes all the tools required for this type of analysis.

CivilWeb Differential Settlement Calculation Spreadsheet

The CivilWeb Differential Settlement Calculation Spreadsheet uses the designer inputs to estimate the differential settlement expected across the foundation. This can be used to assess whether the foundation is suitable as differential settlement can cause damage and cracking to occur in buildings. The CivilWeb Differential Settlement Calculation Spreadsheet includes unique analysis tools which allow the designer to adjust and optimise the foundation design to suit a particular maximum differential settlement in minutes. This can save considerable time on every design compared with completing the calculations by hand.

Buy the CivilWeb Differential Settlement Calculation Spreadsheet now for only £10.