Stay-Cable Replacement Design - PDF Free Download

Existing Cable System Parallel Wires Socket Filler (optional) Strand or Wire Hi-Am Anchors HDPE Sheathing Button Head Strand or Wire Epoxy-Steel Ball Compound Sheathing Sleeve Grout Filled UV Protection UV Protection Tape PE Pipe Wire Grout Copyright Post-Tensioning Institute all rights reserved. Page 3 of 35

Project Background Cracking/splitting of cable cover pipes Rusting and water leakage in anchorage zones Signs of compromise in cables safety In 2002, LADOTD retained CTLGroup to evalute the condition of the stay cables Copyright Post-Tensioning Institute all rights reserved. Page 4 of 35

Inspection Summary 40 out of 72 cables were rated critical Remaining cables had less severe damages Increasing rate of deterioration is evident Timely corrective action was needed Cable replacement selected over repair options based on Life-cycle-cost analysis Copyright Post-Tensioning Institute all rights reserved. Page 9 of 35

Project Scope Assess Current Condition Replacement Cable Design Construction Sequence Design and Structural Analysis Peripheral Design MOT Design Preparation of Construction Documents Cost Estimate Copyright Post-Tensioning Institute all rights reserved. Page 10 of 35

Cable Replacement Design Team Client: LADOTD Prime Consultant: CTLGroup Project Manager: Bridge Engineering Solutions Cable Replacement Design: International Bridge Technologies, Inc. Superstructure Repair Design: TranSystems MOT, Survey & Plans: ABMB Engineers, Inc. Copyright Post-Tensioning Institute all rights reserved. Page 11 of 35

Cable Replacement Objectives Develop a cost effective cable replacement design Minimal engineering by contractors Minimize impact to traffic and MOT requirements Maintain structure capacity for live load, wind force, and construction load effects Monostrand cable system Best available corrosion protection systems Provide for future strand by strand replacement Copyright Post-Tensioning Institute all rights reserved. Page 12 of 35

Cable Replacement Constraints Large spacing of grouped stays Unknown condition of existing stay cables Limited work area, due to MOT constraints Size of replacement cables relative to existing Limited space in anchorage zones. Potential for higher wind loads and wind induced vibration in new cables Copyright Post-Tensioning Institute all rights reserved. Page 13 of 35

Stay Cable Replacement Approach Replace in pairs, Symmetric to tower Use of Temporary Stay Cables Evaluation of anchorage zones to accommodate replacement cables from multiple suppliers Proposed use of Highline to minimize construction space requirements Addition of dampers and cable cross ties for vibration mitigation Copyright Post-Tensioning Institute all rights reserved. Page 14 of 35

Maintenance of Traffic Single lane provided during non-peak traffic Work Area: 12.25 ft width behind barrier Additional 9 ft width adjacent to barrier Copyright Post-Tensioning Institute all rights reserved. Page 16 of 35

Anchorage Zone Modifications Result of increased Cable Anchorage Sizes Designed to accommodate cables from several suppliers C L Cable LEGEND CL Cable Group Existing Bearing Plate, 13" Ø Hole Existing Cross Beam New Bearing Plate and Chair sized for new Anchorage Ring Nut Existing Anchorage Plate Cap New Anchorage Chair New Cable Copyright Post-Tensioning Institute all rights reserved. Page 18 of 35

Temporary Cables Prevent stress increase in existing cables Allow normal use of the bridge during cable replacement Design provided Copyright Post-Tensioning Institute all rights reserved. Page 19 of 35

Temporary Support System Provide means of supporting stay cables during removal and installation operations Design developed assuming Highline or cable way to Limits Work zone requirements Schematic Design of Highline Provided Final Design by Contractor Copyright Post-Tensioning Institute all rights reserved. Page 22 of 35

Construction Summary LaDOTD Project: 450-37-0022 Engineers Estimate: $34.9 mil Bid Opening: 2/25/2009 Low Bid: $30.5 mil (Kiewitt) Top 3 Bidders: $30.5 to $36.7 mil Copyright Post-Tensioning Institute all rights reserved. Page 32 of 35