Shoring Systems2011 NCAPPA ConferenceNCSU McKimmon Center
Steam Tunnel ShoringNC State University
Ed Levy, PENCSU Design and Construction Services
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Thank audience for coming to this presentation. Introduce presentation and myself.
Project Team and Delivery Method
• Erik Hall, Central Utility Plant Manager, NCSU
• Ed Levy, Design PM, NCSU DCS
• John Boykin, Construction PM, NCSU DCS
• Brian M. Ross, PE, Ross Linden Engineers, PC
• Joseph Bailey, Bailey Contracting
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Introduce Erik Hall, Brian Ross and Joseph Bailey. Designed and then direct selection of pre-qualified T&M contractor.
Background
• Oldest portions built in the 1930’s• Distribution pipes for steam heat and hot water• Tunnel portion running west from Steam Plant • Under steps between Main and North Campus • Behind Riddick, Mann and Broughton Halls• Concrete spalls located near Broughton Hall and underneath Yarbrough Drive
• Closest access points – lifting station at rear of Broughton Hall
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Read the entire slide.
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Underground network of tunnels delivering steam and hot water to various campus buildings.
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Yellow line is the section of tunnel for this project, between two adjacent access points. Circles are the access points. Black rectangle is where the work was performed.
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From Yarbrough, the tunnel goes under parking lots and then directly under some very old concrete steps that lead from north behind Mann Hall to main campus at Reynolds Coliseum.
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The tunnel continues under Yarbrough Drive. The tunnel was built long before the road was built. Yarbrough Drive carries cars and buses from west to east.
Initial observations
• By Plant Operations personnel in early 2010.
• Routine maintenance and inspections.
• Spalled concrete from tunnel walls and roof.
• Deep cracks and large portions fallen.
• Exposed reinforcing steel (rebar) in the concrete.
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Read entire slide. Opportunity for Erik Hall to talk about how often routine maintenance and inspections are performed in this part of the tunnel.
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Closest access was at a lifting station behind Broughton Hall.
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Exposed rebar behind an insulated steam pipe.
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Spalled and cracking concrete behind an insulated steam pipe. Metal part is a pipe support rack attached to the tunnel wall.
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Some loose concrete pieces.
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Some damage also in the tunnel ceiling.
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Large pieces of concrete removed showing exposed and rusted vertical and horizontal rebar.
Investigation
• As‐built drawings on file.
• Surveyed extents and variety of field conditions.
• Risk analysis.
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Original design called for rebar in both directions in the tunnel walls. Additional conduits inside the tunnel added much later.
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1985 project added and upgraded steam line supports.
Contributing Factors
• Age of the structure.
• Limits of initial design of tunnel.
• Subsequent use of land development above and near tunnel.
• Proximity of landscaping elements to the tunnel.
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Read entire slide
Project Constraints
• Safety of Plant Operations Personnel and any others required to access tunnel.
• Tunnel Operations must be maintained.
• Limited access points into tunnel.
• Limited funds available.
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Read entire slide
Repair Option Selection
• Reinforce and encase with new structure from outside.
• Reinforce with fiberglass reinforcing from the inside.
• Provide shoring from the inside.
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Opportunity for Brian Ross to explain the options considered.
Design Options
• Custom‐built steel shoring.Adjustable steel columns and beams with base and
cap plates.
• Off‐the‐shelf shoring system.Hydraulic adjustment with integral base and cap plates.
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Opportunity for Brian Ross to further explain the options considered and chosen.
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Opportunity for Brian Ross to explain the option chosen.
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Opportunity for Brian Ross to explain the design implemented.
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Opportunity for Joseph Bailey to explain the working conditions.
Versatility in placement.
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Opportunity for Brian Ross to describe the typical spacing and variations allowed.
Compact
Few parts
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Manpower and materials were brought in and out at the lifting station by stairs and fixed crane.
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Open to questions. Thank audience for their questions and attention.
