This is the state of the practice. Prior to development of the Simplified Method, the
Coherent Gravity Method was used for design of MSE walls reinforced with
inextensible (steel) reinforcements and the Tieback Wedge Method (now the
Simplified Method) was used for design of MSE walls reinforced with extensible
(geosynthetic) reinforcements. Both the Coherent Gravity Method and the Simplified
Method are outlined in Section 11 of the AASHTO LRFD Bridge Design
Specifications (AASHTO, 2010). To select the proper design method, one must
understand reinforcement properties and behavior, so the following sections explain
the behavior differences between inextensible and extensible reinforcements