Major Building and Special Structures

Transcription

1 TECHNICAL SESSION 1 Major Building and Special Structures Moderator Russell B. Price, P.E. Suncoast Post-Tension L.P. Houston, Texas

2 2004 PTI Technical Conference Session 1 Dennis Wittry -- Denver's Invesco Field Stadium Post-Tensioning at Invesco Field at Mile High Dennis M. Wittry, P.E., S.E. Walter P. Moore & Associates, Inc. Houston, Texas Post-tensioning was used extensively at Invesco Field at Mile High, the new 76,152-seat home to the Denver Broncos (NFL) and Colorado Rapids (MLS). The structural framing for the concourses of the stadium consist of 8 wide, 29 deep post-tensioned circumferential pan joists framing to post-tensioned 33 wide x 29 deep transverse girders. This structure was developed through post-bid, value engineering exercises with the concrete sub-contractor, Phipps/Baker, joint venture of Baker Concrete and Phipps Construction. The two-way post-tensioned system was considered due to the long joist spans (40 to 50 ) and high superimposed loads (3 topping slabs, 100 psf live loads and numerous masonry walls). Early scheme studies had concluded that a system of cast-in-place girders and columns with precast concrete double tee infill, which has been used for several other NFL stadiums, was the most economical. Schematic pricing of the two-way post-tensioned scheme, however, indicated an approximate $2 million savings over the original scheme. Creative long-pan forming and shoring systems developed by Baker Concrete and structural design that eliminated the need for reshoring resolved initial concerns about schedule and quality of finish. Additionally, the post-tensioned system allowed for a shallower structural depth, providing additional mechanical plenum space and allowing for the floor-to-floor height at one of the suite levels to be reduced for additional cost savings. Concerns with the original precast infill system were as follows: Curved Geometry Flying Formwork Structural Depth Coordination between precast and cast-in-place Excessive Topping Slab Advantages to the use of this two-way, post-tensioned system were: Cost. Approximately $2 million savings over original structural system. Geometry. The cast-in-place concrete system was better able to handle the varying geometry and loading. Structural Depth. Post-tensioning allowed for the structural depth to be reduced by 5 typically. Durability. As an open-air stadium, exposure to the elements was a major concern. Post-tensioning allowed the tensile stresses to be limited therefore reducing the number and size of flexural cracks. Reduced congestion. The original mild-girder system typically required multiple layers of reinforcement. Post-tensioning significantly reduced the amount of reinforcement required and eliminated the need for multiple layers of reinforcement in most members. Deflection. With significant extents of masonry, most of the concrete framing was under strict deflection limits. In most cases, post-tensioning allowed for these deflection limits to be meet without increasing member sizes. Challenges to the two-way, post-tensioned system used: Schedule. The original schedule of the precast infill system had to be maintained. Closed Geometry. The closed geometry required one-way pulls with building sections of almost 300 feet. Pour strips were required at two floors to allow the concourse to be closed. Education. The Owner and Sub-contractors were not familiar with post-tensioning and education was required to dispel post-tensioning myths. Copyright - Post-Tensioning Institute 2 All rights reserved

3 2004 PTI Technical Conference Session 1 Dennis Wittry -- Denver's Invesco Field Stadium 2004 Post Tensioning Institute Conference Case Study: Invesco Field at Mile High Stadium Presented by Dennis M. Wittry, P.E., S.E. Walter P. Moore and Associates, Inc. Presentation Outline Overview of Invesco Field Why Did we Choose PT? Original Scheme Advantages of PT Scheme Challenges The Results Questions Overview of Invesco Field Overview of Invesco Field Located in Denver, Colorado Denver Broncos (NFL) Colorado Rapids (MLS) 76,125 seat Stadium 5 th Largest in NFL 124 Suites $408,000,000 Total Cost Completed August 2001 Overview of Invesco Field 1,700,000 Square Feet 5 Framed Levels Upper and Lower Concourse Levels 2 Suite Levels & 1 Club Level Concourse Structural System 2-way Post-Tensioned CIP Concrete PT Pan Joists and PT Girders 256 Miles of Post-Tensioning Charlotte to Atlanta 244 miles Overview of Invesco Field Design/Build Joint Venture Turner Construction HNTB Corporation Architects HNTB Sports Architecture Fentress Bradburn Architects Burtram A. Bruton and Associates Structural Engineer Walter P. Moore The Sheflin Group Copyright - Post-Tensioning Institute 3 All rights reserved

4 2004 PTI Technical Conference Session 1 Dennis Wittry -- Denver's Invesco Field Stadium Overview of Invesco Field Overview of Invesco Field Contractor Turner Construction Empire Construction Services Alvarado Construction Concrete Sub-Contractor Gerald H. Phipps Baker Concrete Post-Tensioning Supplier/Installer Suncoast Post-Tension - Supplier Parker Steel - Installer Why Did We Choose PT Originally We Didn t! Why Did We Choose PT Original Concourse Structural System Mildly Reinforced CIP Concrete Frame with Double Tee Infill Preferred System by Turner Construction Used At 3 Other NFL Stadiums by Turner Bank of America Stadium (Charlotte) M&T Bank Stadium (Baltimore) Paul Brown Stadium (Cincinnati) Other Schemes Reviewed Structural Steel Mild Reinforced Concrete Beam and Slab Original Precast Infill System Copyright - Post-Tensioning Institute 4 All rights reserved

5 2004 PTI Technical Conference Session 1 Dennis Wittry -- Denver's Invesco Field Stadium Original Concourse Structural System Advantages of the Precast System Lateral Frame Provided by CIP Elements Double Tees Could Easily Handle Spans Double Tee Spans of up to 50 + Quick Erection Time Precast is Very Prevalent in Denver Turner was Very Familiar with System Least Costly Scheme of 3 Initially Considered Why Did We Consider Changing? Geometry Curved Concourse Geometry 6 Different Radii Around Bowl Limited Repetition for Precast Load Variations Reduced Repetition Why Did We Consider Changing? Geometry Curved Concourse Geometry 6 Different Radii Around Bowl Limited Repetition for Precast due to Geometry Load Variations Reduced Repetition Excessive Flying Formwork Radial Beams Required for Lateral Stiffness Almost as Much Shoring as for full CIP Deck Structural Topping Slab Required Why Did We Consider Changing? Depth Limitations Girders were Overly Congested Trade Coordination Tolerance Issues b/w CIP and Precast More Crane Time Excessive Jointing in Topping Slab Pattern to follow edges of Double Tees Copyright - Post-Tensioning Institute 5 All rights reserved

6 2004 PTI Technical Conference Session 1 Dennis Wittry -- Denver's Invesco Field Stadium Why Did We Choose PT Solution: Two-Way Post-Tensioned Cast-in-Place Pan Joist System Tendon Support Bar Unbonded Post-Tensioning 24 5 VARIES: TYP 30, 53, OR 66 8 Post-Tensioned Joists Why Did We Choose PT Why Did We Choose PT Unbonded Post-Tensioning Top Mild Reinf. 5 Bottom Mild Reinf Post-Tensioned Joist Beyond Post-Tensioned Joists Post-Tensioned Girder Why Did We Choose PT Post-Tensioned Girder Advantages PT Girders Reduce Congestion Cast-in-Place Better Handles Geometry PT Joists Allowed for Long Spans Shallower Structural Depth Allowed for a Reduction in Building Height Inherent Lateral Stiffness Better Crack Control & Durability Fully Encapsulated Tendons Copyright - Post-Tensioning Institute 6 All rights reserved

7 2004 PTI Technical Conference Session 1 Dennis Wittry -- Denver's Invesco Field Stadium Why Did We Choose PT Challenges Schedule Needed to Maintain Tight Construction Schedule Solution: Custom Long Pan Forms Minimized Shoring Expedited Pan Turnover Formwork Re-Use Critical to Economy Adjustable End Cap Increased Formwork Repetition Upgrade Framing to Eliminate Reshores Added Value Provided Higher Finish Level for Exposed Panwork Custom Long Pans Why Did We Choose PT Challenges Closed Geometry Concourse Broken into 8 Sections Required One-Way Pulls Sections Up to 280 Long Solution: Add Tendons for 1 st Pour of Each Section Pour Strip Used to Close Circle Stress Pockets in Slab for Add Tendons The Results Challenges Myths and Rumors Regarding PT CIP Post-Tensioning not Prevalent in Denver Owner & Sub-Contractors Didn t Understand PT Solution PT Education Session Lead by Walter P. Moore / Baker Concrete / Suncoast Owner, Contractor and All Major Subs Represented Explained Benefits of PT and Dispelled Myths Copyright - Post-Tensioning Institute 7 All rights reserved

8 2004 PTI Technical Conference Session 1 Dennis Wittry -- Denver's Invesco Field Stadium The Results Delivered On Schedule Improved Durability Improved Architectural Appearance $2,000,000 Saved Over Precast Infill System! Questions? Copyright - Post-Tensioning Institute 8 All rights reserved

9 Construction of the Four Seasons Hotel and Tower in Miami Phil Arana, P.E. Ricardo Lizarazu, P.E. Suncoast Post-Tension, L.P. Miami Division A general overview of the Four Seasons Hotel and Tower at Miami building is presented. Structural concepts, structural main frame-work and the posttensioned slab systems are discussed. Architectural, as well as essential structural challenges regarding mixed use, functionality and local environmental conditions are described. Detailed information about the core inside a core structural system, as well as the wind analysis is given. Construction phase problems and main concerns are addressed and solutions adopted are illustrated. Special attention is given to the primary slab system used on the elevated levels, in which a post-tensioned concrete slab was used. Illustrations are mainly focused on solutions given during the construction phase on issues related to the pour sequence of the slab, pour breaks and schedules, as well as special connection details developed for joining the slab system to the main inner core system and to the perimeter column-beam frame. This was done to allow reduction of overall construction time using a system of jump-forms for the inner core, which required the casting of the slabs after the walls of the inner core were poured. Details are presented for the use of post-tensioning on transfer areas of slabs and on shear walls. A final discussion is made on the future of high-rise construction. Copyright - Post-Tensioning Institute 9 All rights reserved

10 FOUR SEASONS BUILDING STRUCTURAL CONCEPTS STRUCTURAL MAIN FRAMEWORK POST-TENSIONED CONCRETE SLAB SYSTEM FOUR SEASONS HOTEL AND TOWER FACTS: Location:....Miami Owner:... Millennium Partners, NY Construction Manager: Bovis Lend Lease, Miami Architect:... Bermello Ajamil & Partners Architect:... Gary Edward Handel Assoc. Structural Engineer:.... DeSimone Consulting Eng. Post-tension Specialty Eng. & Supplier... Suncoast Post-tension Courtesy of Millennium Partners GENERAL FACTS Courtesy of Desimone Consulting Engineers Tallest Building South of Atlanta Tallest residential building south of New York City Among 50 tallest buildings in the world 8th tallest residential building in the world 67 floor mixed use Retail, Parking, Office, Hotel, Condominium Total area: 1,900,000 ft 2 Value $ 257,000,000 Date of Completion of Construction: 2003 HOTEL AND TOWER FEATURES 789 ft tall building 222 Rooms in 5 star Four Seasons Hotel 45,000 ft 2 fitness and spa facility 186 luxury condominiums 84 room extended stay apartments 200,000 ft 2 Class A office space 2 Acre pool terrace 10,600 ft 2 of retail space 934 parking spaces MAIN STRUCTURAL FACTS Reinforced Concrete Structure Tubular Lateral System Core Shear Walls & Perimeter Columns Post-tensioned slabs Span between supports between 40 and 50 ft Wind Tunnel Analysis Courtesy of Bovis Lend Lease Courtesy of Bovis Lend Lease Copyright - Post-Tensioning Institute 10 All rights reserved

11 CONSTRUCTION PHASE Formwork consisted of flat slab spanning between interior cores and perimeter beam-column frames. Cores were formed independently of a crane using PERI-ASC self climbing system After very short learning curve, form contractor crew accomplished very effective schedules. Fast cycle had to be slowed down to a 4-day cycle in order to not climb too far ahead of slab and facade work. Courtesy of Peri - Formwork and Scaffolding Courtesy of Peri - Formwork and Scaffolding UPPER LEVELS LAYOUT UPPER LEVELS SOFFIT LAYOUT Columns at facade Spandrel beam STRUCTURAL SLAB DESIGN BANDED TENDON LAYOUT General Layout of PT system Pour Sequence Pour Schedule Slab connection to main frame system Link beam construction PT anchorage placement Form savers for main mild reinforcement Breakdown areas Use of PT at transfer levels Copyright - Post-Tensioning Institute 11 All rights reserved

12 BANDED TENDON PERSPECTIVE DISTRIBUTED TENDON LAYOUT UNIFORM TENDON PERSPECTIVE POUR SEQUENCE - SCHEDULE Copyright - Post-Tensioning Institute 12 All rights reserved

13 INNER CORE SLAB CONNECTION TO MAIN FRAME SYSTEM PT ANCHORAGE PLACEMENT & REINFORCEMENT FORM SAVERS Top Slab Rebar Form Saver Copyright - Post-Tensioning Institute 13 All rights reserved

14 PT Reaction CONNECTION OF SLAB TO THE OUTER FRAME Maximum efficiency of PT tendons Column Schematic Not To Scale Bar placing due to anchor plate location Maximum efficiency of PT tendons Copyright - Post-Tensioning Institute 14 All rights reserved

15 LINK BEAM CONSTRUCTION Copyright - Post-Tensioning Institute 15 All rights reserved

16 BREAK-DOWN AREAS Link beams extended out to shorten spans and/or for stiffening areas Drops used to shorten spans and/or for stiffening areas USE OF POST- TENSIONING AT TRANSFER LEVELS Copyright - Post-Tensioning Institute 16 All rights reserved

17 Columns that will be hanging from this level Columns starting at this level 3rd Level 4th Level 3rd Level 4th Level Uniform cables with harped profile to receive band Concentrated band to pick up columns PT Tendons Profile at 4th Level Uplift force from band Column Reaction Copyright - Post-Tensioning Institute 17 All rights reserved