General Structural Design
CNA provides a variety of general structural engineering including cast-in-place concrete, structural steel, and pipe supports and anchors in a variety of underground environments; structural concrete repair; removable covers for access shafts; temporary support of excavation; existing structure evaluation and much more.
Tunnel Evaluation & Repairs
CNA inspected and designed repairs to an urban creek tunnel in multiple locations. The repairs were in a section of the tunnel constructed in 1913 and consisted of an existing cast-in-place concrete roof with limestone block walls and concrete floor.
CNA designed lift-off-cover access points at two locations that created openings up to 16 feet wide for future tunnel access. In another area, a section of floor failed into a void below and a new floor was designed and placed.
Steam Pipe Anchors
CNA has provided evaluations, inspections, designs and construction observations for piping support and anchorage in numerous utility tunnels. The work includes anchorage into a variety of substrates (brick, concrete, steel, rock, etc.) in challenging work conditions, such as confined space and within shafts, active utility lines that cannot be shut off during construction, and extreme cold/heat.
Many of the designs require very precise geometry and consideration of the complex forces they are subject to, which we are happy to provide.