Convention Center CMU Wall Repair

Carrasquillo Associates designed repairs for a 50 ft. tall exterior concrete masonry unit (CMU) wall. During construction, it was discovered that the wall was constructed without the proper amount of reinforcement, essentially making it unreinforced. CA computed the loads acting on the wall from self-weight, cladding, and wind. Multiple wall sections were considered due to the varying cladding, geometry, and parapet details. Nearly the entirety of the wall was overstressed due to the wind load. CA’s repair involved adding a steel structural support to reduce the wall’s span and thus reduce flexural demands. This significantly reduced the overstressed areas such that localized areas could be strengthened with fiber reinforced polymer sheets. While developing the repair, CA collaborated with the Structural Engineer of Record to ensure that the added steel support would not overload the existing steel columns and braced frames.

Municipal Water Tank Roof Failure

CA investigated the structural integrity of a 275,000 gallon municipal water tank in Vermont. The water tank consisted of a cast-in-place concrete foundation slab, cast-in-place concrete walls, and a precast, hollow-core plank roof with a continuous cast-in-place concrete topping slab over the planks. After only about ten years in service, distress was noted on the underside of the precast, hollow-core planks in the form of cracking and fractured and fallen sections of concrete. CA investigated the distress and alleged failure of the water tank. CA focused on the structural system, construction, and condition of the water tank as well as determining the cause(s) of the observed distress. CA reviewed construction documents, construction specifications, previous engineering and petrographic summary reports, and relevant published literature and industry standards. CA’s field observations, sampling, and petrographic examination revealed that the overall tank structure was in good condition and that the distress in the roof structure was due to an internal sulfate attack mechanism. CA determined that the distress mechanism emanated from planks’ manufacturing process.

GPR Scanning for Artwork Design and Construction

Carrasquillo Associates (CA) performed work related to ground penetrating radar (GPR) scanning for artwork to be installed. Prior to construction, CA scanned and mapped areas around the perimeter and approximately 900 sq. ft. of the art zone’s interior to determine appropriate places for through drilling between double tee stems and embedded anchors in double tee stems. After reviewing available construction documents, drawings, and project related material, CA completed extensive scanning of the parking deck using high resolution GPR equipment. CA mapped the location of precast double tee stems and embedments in the parking deck. Embedments and items found on the underside of the slab were identified as “no drill zones” and the extents of the double tee stems were also mapped. The project was a great success with over 900 sq. ft. scanned, and only one drilled hole encountering an unforeseen embedment.