Retain may be used to design or review cantilevered concrete retaining walls and bridge abutments with either spread footing or pile foundations.

Program input may be supplied interactively by filling in the GUI tab control form or via an externally created file. Input files may be saved for later editing and reuse. The input may be supplied in either English or SI (metric) units. The program is not dimensionless due to the concrete design formulas, therefore dimensions should be input as specified under Program units in the Program options section.

Concrete design may be performed using either the ultimate strength design procedure or the working stress design method. For working stress design and ultimate strength design the specified load factors are used for calculation of material stress. The load factors for working stress design should be reduced below 1.0 to account for allowable stress increases (ie. use load factor = 0.75 for 33% stress increase). For external stability calculations (sliding, overturning, bearing pressure, etc.), the load factors are internally changed to 1.0 for each specified load. For further information refer to the Load Combinations section.

The soil configuration may either be constant sloped backfill with a uniform surcharge loading or an irregular backfill and surcharge load. The constant sloped backfill uses the user-input lateral pressure coefficients to calculate the force on the wall. The irregular backfill option uses the trial wedge solution procedure with the user-input soil friction angle to calculate the wall forces.

A variety of loads may be specified on the wall, including axial dead and live load at the top which allows the program to simulate a bridge abutment loading. Other top-of-wall loads include moment and shear from wind and earthquake, which allow the program to simulate sound wall loadings. A seismic lateral earth pressure coefficient may be included for use using the Mononabe-Okabe method for constant slope backfill, or an acceleration in G’s may be specified to accelerate the trial wedge for the irregular backfill configuration.

Safety factors for external stability and soil parameters such as friction coefficients and allowable bearing pressure may be specified separately for regular load, wind loads and seismic loads. This gives the user the flexibility necessary for checking multiple load conditions in one design run.