Defaults Tab

On the defaults tab you can alter the factors of safety, load factors and max/min parameters for the reinforcement, depending on which design code is being used. The default values and factors in the tables are those taken from the various codes and it will be unlikely that you would need to change them without good reason.

The main one of note is the Minimum Surcharge of 10 kN/m2 on the top surface of the soil as recommended by BS 8002, for vehicular traffic either during the construction period or during the design life of the wall. The user could alter this value if it can be shown that a lower figure is acceptable, eg, behind a garden wall where vehicular access is not possible.

There is also an option to check the wall stem for L/d. This, of course, does not include for any rotation of the wall and base as a combined unit.

Factors of safety for use with CP2 design.

Load Factors for use in BS 8002 design.

Load Factors for use in EC7 design.

There is also a tick box option for a Service Bearing Pressure Case. The usual 6 Equ/Geo/Str load cases taken from EC7 are all ULTIMATE load cases and the soil pressure calcs for these should be compared to an ultimate soil bearing resistance entered on the Soil Data tab, not the permissible bearing pressure that many engineers have been used to in the BS design method. Since these 6 cases are ultimate, there is a further need to check the service load case for bearing, hence the tick box introducing load case 7. The service bearing resistance is calculated from the ultimate bearing resistance by dividing it by a factor of safety of 3 – a generally accepted value.

Max and min values for reinforcement in a masonry retaining wall.