At 3,709 feet, the M-231 bridge over the Grand River is the seventh longest bridge in Michigan. M-231 is about 7 miles long and connects M-45 (Lake Michigan Drive) in Robinson Township to M-104/I-96 in Crockery Township, Michigan. The two-lane route provides a much-needed additional crossing of the Grand River. The M-231 bridge is supported by one pier driven into the river, and about 15 more on either side of the water.

The cost to build M-231 was $157 million. SME helped to reduce the cost by providing value engineering (VE) to redesign the dolphin structures which protect the bridge pier from impacts of boats, ships and barges. Similar to highway crash barriers for automobiles, dolphins are designed as sacrificial elements that absorb the energy from the impact of a moving vessel to prevent severe structural damage to the bridge pier.

The original design called for each dolphin to consist of a cluster of four, 42-inch diameter by 128-foot long concrete filled pipes. There were a total of six of these clusters: three on the downstream side and three on the upstream side of the pier. SME was retained by C.A. Hull to evaluate whether a more efficient and less costly design option could be engineered. In conjunction with C.A. Hull and Hardman Construction, SME developed a design using single 72-inch diameter piers with one-inch thick steel casing to replace the four pier cluster. Since the single pier protection dolphins were larger in diameter, they were more efficient than the original four-pile clusters. Only six protection piers were needed as compared to 24 piles, offering a significant cost saving to the Michigan Department of Transportation MDOT.

SME provided a comparative “push-over” analysis of both the 4-pile cluster and the single protection pier to evaluate the energy dissipation capabilities of two systems. As seen in the figure below, the energy dissipation of the single 72-inch concrete filled pier is nearly identical to the four 42-inch pile cluster, and MDOT approved the VE substitution.

The performance of the protection pier required the concrete to be confined without any separation from the permanent steel casing. To meet this requirement, Consumers Concrete Corporation developed and supplied a non-shrink concrete mix design using a special shrink reducing admixture for the protection piers.

Mr. Jay Desai, C.A. Hull's project manager, noted that $150,000 was returned to MDOT as a result of this redesign, and the contractors were able to retain a similar amount of savings. With SME fees of approximately $32,000 for the redesign and new plan, total savings were about $300,000 — or about nine times our fee.