Thousand Oaks, CA
Calleguas Municipal Water District, Conduit North Branch
Calleguas Municipal Water District experienced a failure in 140 ft of steel liner within a 78 in. dia. prestressed concrete cylinder pipe (PCCP) water main. The failure resulted in local flooding and loss of service. SGH was retained to evaluate the safety of the as-constructed steel liner and recommend remedial work.
SGH performed a nonlinear finite element analyses of the 3/8 in. welded steel liner to reconstruct the failure and evaluate several reinforcing schemes. Our model included complex geometry at the intersection of longitudinal and circumferential seams, longitudinal back bars, bell rings, and connecting welds. We modeled over 150,000 elements to examine stress concentrations around welds and the effect of improper welds. SGH determined that the failure was due to eccentricities introduced at welds of the liner to the backer bars.