Spotlight Projects:

The Hopper Engineering Associates team provides practical and exciting solutions to unique problems in several industries. To showcase our recent work we choose a project of the month. An archive of previous winners can be found here.

Spotlight Project:

Seismic Margin Evaluation - Various Nuclear Plant Components and Structures
Seismic Margin Evaluation

A utility client requested a seismic margin assessment (SMA) to satisfy NRC regulatory criteria. Various items inside the site's reactor/auxiliary building were identified for the assessment. Of particular interest were unreinforced CMU block walls supporting safety related equipment and concrete shield walls adjacent to safety related equipment. Our task was to verify that these walls were able to withstand the seismic margin earthquake (SME) without collapsing. Because a SME is a beyond design basis event the acceptance criteria in this case was defined as the stability of the wall plus adequate anchorage of essential equipment.


Our analysis followed the conservative deterministic failure margin approach (CDFM) to guarantee a high confidence low probability of failure (HCLPF) of the walls. As part of this process several walls of varying geometry and construction were mathematically idealized. A site specific SME response spectrum was utilized and amplified as necessary to reflect the location of the wall(s) within the reactor/auxiliary structure. Several analysis techniques were required because the large variety of wall configurations and unique boundary conditions. Some of the techniques used in the analysis include time history analysis, the reserve energy method and basic response spectrum analysis in combination with ultimate strength calculations. Our analysis demonstrates that the true collapse capacity of all walls exceeds the demand. A SME maximum acceleration was reported for each wall.

HEA has completed numerous jobs similar to the one shown above (Similar Projects)