Evaluation of AASHTO load factor and resistance design methods for benchmarked braced excavations

摘要

To evaluate the effects of load factor and resistance design on current design practice, a limited number of constructed and monitored braced excavations are first benchmarked with a non-linear analysis approach. The obtained benchmarked models are then reanalyzed with AASHTO (2010) LRFD factors applied in separate design case scenarios. Each analysis is carried out with both limit equilibrium and non-linear analysis methods. Subsequently, results from all combinations are evaluated and compared. The results of this LRFD exercise have been particularly revealing. In many cases, the design methods fail to produce adequate safety factors for wall moment or support reactions compared to the benchmarked models. Whilst a seasoned professional would quickly realize these design code misbehaviors, a not so experienced engineer might blindly produce code consistent designs that are clearly unsafe regarding some critical aspects. For this reason, the authors encourage that noted LRFD inconsistencies are officially addressed in the near future.