North Shore Equitable Building

North Shore Equitable Building
Stephan Northrop – Structural Option Advisor: Dr. Hanagan April 13, 2011

Presentation Outline Building Introduction Existing Building Information Problem Statement Proposed Solution Structural Depth Codes & Loads Proposed Gravity System Proposed Lateral System Foundation Assessment Acoustic Analysis Breadth Conclusion Acknowledgements & Questions Stephan Northrop Structural Option

General Building Information Building Introduction Existing Building Information Problem Statement Proposed Solution Structural Depth Codes & Loads Proposed Gravity System Proposed Lateral System Foundation Assessment Acoustic Analysis Breadth Conclusion Acknowledgements & Questions Location: Pittsburgh’s North Shore Owner: Continental Real-Estate Occupancy Type: Low rise commercial Delivery method: Design build Dates of construction: Oct ’03 - Dec ‘04 Cost: $70 million Size: 6 stories, 180,000 sq. Ft. 87’1” building height Stephan Northrop Structural Option

Existing Structural System Building Introduction Existing Building Information Problem Statement Proposed Solution Structural Depth Codes & Loads Proposed Gravity System Proposed Lateral System Foundation Assessment Acoustic Analysis Breadth Conclusion Acknowledgements & Questions Foundation 5 ½” Slab on grade 18” Auger Cast Piles Steel H piles Light rail transit line accommodation Stephan Northrop Structural Option

Existing Structural System Building Introduction Existing Building Information Problem Statement Proposed Solution Structural Depth Codes & Loads Proposed Gravity System Proposed Lateral System Foundation Assessment Acoustic Analysis Breadth Conclusion Acknowledgements & Questions Foundation 5 ½” Slab on grade 18” Auger Cast Piles Steel H piles Light rail transit line accommodation The foundation consists of a 5 ½” slab on grade supported by grade beams and a combination of auger cast piles and steel h piles. The foundation is designed to accommodate a light rail transit line passing below the eastern most bays of the building. Stephan Northrop Structural Option

Existing Structural System Building Introduction Existing Building Information Problem Statement Proposed Solution Structural Depth Codes & Loads Proposed Gravity System Proposed Lateral System Foundation Assessment Acoustic Analysis Breadth Conclusion Acknowledgements & Questions General Floor Framing Gravity System 5 ½” Lightweight composite floor slab Steel wide flange beams and girders W14 steel columns Lateral System N/S Direction: Braced frames E/W Direction: Steel moment frames Steel wide flange beam and girders. Beams range in size from w18x40’s to w21x44’s. Girders range in size from w24x62’s to w30x116’s. Columns ranging from W14x48 to W14x311. Stephan Northrop Structural Option

Existing Structural System Building Introduction Existing Building Information Problem Statement Proposed Solution Structural Depth Codes & Loads Proposed Gravity System Proposed Lateral System Foundation Assessment Acoustic Analysis Breadth Conclusion Acknowledgements & Questions General Floor Framing Gravity System 5 ½” Lightweight composite floor slab Steel wide flange beams and girders W14 steel columns Lateral System N/S Direction: Braced frames E/W Direction: Steel moment frames The lateral system Braced frames running in the north/south direction along grid lines C and F Steel moment frames running in the east/west direction along grid lines 2 and 3 Stephan Northrop Structural Option

Problem Statement Building Introduction Existing Building Information Problem Statement Proposed Solution Structural Depth Codes & Loads Proposed Gravity System Proposed Lateral System Foundation Assessment Acoustic Analysis Breadth Conclusion Acknowledgements & Questions Subgrade light rail transit line poses vibration and noise control issues Large bay sizes are required Project Goals Improve noise control Maintain existing grid layout When this building was designed, engineers were faced with the task of designing the structure to accommodate the subway line that passes below the building. This subway line has the potential to produce unwanted noise pollution that could spread into the office spaces. Because of this, large bay sizes are a requirement so that the foundation does not interfere with the subway line. Although the existing composite steel structure is a very economical choice for this design, an alternate concrete structure will be investigated for the purpose of this thesis in order to put a greater emphasis on improving noise reduction. The goals of this project will be to improve noise control and maintain the existing grid layout. Stephan Northrop Structural Option

Proposed Solution Building Introduction Existing Building Information Problem Statement Proposed Solution Structural Depth Codes & Loads Proposed Gravity System Proposed Lateral System Foundation Assessment Acoustic Analysis Breadth Conclusion Acknowledgements & Questions Structural Depth Study Redesign the structure as a one way concrete pan joist and beam system Investigate the impact on the building foundation Acoustic Analysis Investigate the noise reduction benefits of a concrete structure Cost & Schedule Analysis (not presented) Investigate the cost and scheduling implications of a concrete structure the proposed solution for this thesis will be to redesign the structure as a one way concrete pan joist and beam system. Since a concrete structure will increase the building weight, the bearing capacity of the foundation will have to be adjusted as well Since noise reduction is a key goal of this thesis project, an acoustical analysis will be performed. Finally, to fully compare the new and existing structures, a cost and schedule analysis will have to be performed as well. Due to time constraints, the cost analysis will not be included in the presentation today. Stephan Northrop Structural Option

One Way Concrete Pan Joist and Beam System
North Shore Equitable Building Proposed Solution Building Introduction Existing Building Information Problem Statement Proposed Solution Structural Depth Codes & Loads Proposed Gravity System Proposed Lateral System Foundation Assessment Acoustic Analysis Breadth Conclusion Acknowledgements & Questions One Way Concrete Pan Joist and Beam System Inherent noise & vibration reduction Ability to accommodate long spans Decreased floor depth Possibility of decreased construction costs A one way pan joist and beam system was chosen for several reasons. Not only does concrete have inherent noise and vibration reduction qualities, but a one way system has the ability to accommodate greater spans than a post-tensioned system. It was discovered in tech 2 that a post-tensioned system would not be able to support the 44 by 38 bay on the west side of the building without exceeding the allowable compression stress limit. Also, a one way system will decrease the floor to floor height, whereas a hollow core plank system, which was also looked at in tech 2, will increase the the floor heights. Stephan Northrop Structural Option

Codes & Loads Building Introduction Existing Building Information Problem Statement Proposed Solution Structural Depth Codes & Loads Proposed Gravity System Proposed Lateral System Foundation Assessment Acoustic Analysis Breadth Conclusion Acknowledgements & Questions Existing Design 100 PSF live loads at all levels AISC 9th edition, ACI , and ASCE 7-95 used for design Redesigned Structure 80 PSF live load at all upper levels 100 PSF live load at ground level ACI and ASCE 7-05 used for redesign In the existing design, the engineers chose to conservatively design for a 100 psf live load rather than the required 50 psf live load. An 80psf live load was used in the redesign to be conservative but also to avoid over designing the structure. Since this building was designed over 10 years ago, ACI and ASCE 7-95 were used in the design For this thesis, ACI and ASCE 7-05 will be used. Stephan Northrop Structural Option

Proposed Gravity System Building Introduction Existing Building Information Problem Statement Proposed Solution Structural Depth Codes & Loads Proposed Gravity System Proposed Lateral System Foundation Assessment Acoustic Analysis Breadth Conclusion Acknowledgements & Questions Slab/Pan Joist Design Normal weight, 4000 psi concrete Designed using Excel spreadsheets and hand calculations 24.5” deep floor system Slab 4.5” thick slab with #3 12” o.c. Pan Joists 20” depth, 7” width Spaced at 60” o.c. 2 #9 top bars & 2 #10 bottom bars For the design of the gravity system, design guides were referenced to estimate member sizes, and then an Excel spreadsheet and hand calculations were used to size the members. Normal weight, 4000 psi concrete was used throughout the design. The slab for this structure is 4.5” thick reinforced with #3 bars at 12” o.c. The pan joists for this structure are spaced at 60” o.c. with a width of 7” and a depth of 20” reinforced with #9 top and #10 bottom This brings the total floor thickness to 24.5”, a full 10” thinner than the existing system. Stephan Northrop Structural Option

Proposed Gravity System Building Introduction Existing Building Information Problem Statement Proposed Solution Structural Depth Codes & Loads Proposed Gravity System Proposed Lateral System Foundation Assessment Acoustic Analysis Breadth Conclusion Acknowledgements & Questions Girder Design Designed using Excel spreadsheets and hand calculations 24.5” x 40” Girders used for 44’ spans 24.5” x 32” girders used for spans less than 44’ Spans > 40’ reinforced with #9 and #10 bars Spans < 40’ reinforced with #8 bars given the building’s symmetrical nature, only four different types of girder designs exist in the redesigned structure. 24.5 x 40 girders are used to span 44’ distances, shown in blue on the right 24.5 x 32 girders are used for all other spans, shown in red Girders spanning > 40’ are reinforced with #9 and #10 bars Stephan Northrop Structural Option

Floor System Framing Plan Floor System Framing Plan
North Shore Equitable Building Proposed Gravity System Building Introduction Existing Building Information Problem Statement Proposed Solution Structural Depth Codes & Loads Proposed Gravity System Proposed Lateral System Foundation Assessment Acoustic Analysis Breadth Conclusion Acknowledgements & Questions Floor System Framing Plan Decreased tributary area No additional columns necessary Floor System Framing Plan Once the design process was under way, the decision was made to have pan joists running both horizontally and vertically in the structure. This was done in order to eliminate excessive tributary areas while also avoiding the addition of extra columns Excessive tributary area Disrupted open floor space Stephan Northrop Structural Option

Stairwell & Elevator Shaft Framing Stairwell & Elevator Shaft Framing
North Shore Equitable Building Proposed Gravity System Building Introduction Existing Building Information Problem Statement Proposed Solution Structural Depth Codes & Loads Proposed Gravity System Proposed Lateral System Foundation Assessment Acoustic Analysis Breadth Conclusion Acknowledgements & Questions Stairwell & Elevator Shaft Framing Beam widths of 24”, 20” and 16” used Spans range from 20’ to 44’ #6 and #8 bars used for reinforcing Stairwell & Elevator Shaft Framing Rather than use shear walls, which would introduce unwanted torsion, the stairwells and elevator shafts are framed with concrete beams of varying widths. All Beams have a 24.5” depth with widths of 24”, 20” and 16” depending on the loading condition. #6 bars and #8 bars are used to reinforce all 3 beam sizes. Stephan Northrop Structural Option

Proposed Gravity System Building Introduction Existing Building Information Problem Statement Proposed Solution Structural Depth Codes & Loads Proposed Gravity System Proposed Lateral System Foundation Assessment Acoustic Analysis Breadth Conclusion Acknowledgements & Questions Column Design Designed using an Excel spreadsheet and hand calculations Checked using spColumn Exterior Columns 24”x48” L-shaped columns at all corners 24”x48” Rectangular columns along exterior Interior Columns 30”x30” and 26”x26” square columns at 1st level Sizes decrease with ascending floor level Columns for the redesigned structure are sized using excel and hand calculations and checked using sp column exterior columns consist of 24x48 L-shaped columns at the building corners and 24x48 rectangular columns These columns are overdesigned for gravity loads, but play an important role in the lateral system as will be explained shortly. Stephan Northrop Structural Option

Proposed Gravity System Building Introduction Existing Building Information Problem Statement Proposed Solution Structural Depth Codes & Loads Proposed Gravity System Proposed Lateral System Foundation Assessment Acoustic Analysis Breadth Conclusion Acknowledgements & Questions Column Design Designed using an Excel spreadsheet and hand calculations Checked using spColumn Exterior Columns 24”x48” L-shaped columns at all corners 24”x48” Rectangular columns along exterior Interior Columns 30”x30” and 26”x26” square columns at 1st level Sizes decrease with ascending floor level Interior columns range in size from 30x30 square columns at the ground level to 20x20 at the 6th level as seen in the diagram on the right Stephan Northrop Structural Option

Proposed Lateral System Building Introduction Existing Building Information Problem Statement Proposed Solution Structural Depth Codes & Loads Proposed Gravity System Proposed Lateral System Foundation Assessment Acoustic Analysis Breadth Conclusion Acknowledgements & Questions Ordinary concrete moment frames L-shaped and rectangular columns along exterior to add stiffness Concrete shear walls at core avoided to minimize torsion Moving on to the lateral system The lateral system consists of ordinary concrete moment frames spanning both east/west and north/south Supplimented with the L-shaped and rectangular exterior columns which act as small shear walls to add stiffness Stephan Northrop Structural Option

Proposed Lateral System Building Introduction Existing Building Information Problem Statement Proposed Solution Structural Depth Codes & Loads Proposed Gravity System Proposed Lateral System Foundation Assessment Acoustic Analysis Breadth Conclusion Acknowledgements & Questions ETABS Computer Model Modeling Assumptions Rigid Diaphragms used at all levels Building mass represented as diaphragm additional area mass Cracked moment of inertias considered Rigid end offsets applied to all members using a factor of 0.5 To evaluate the lateral system, an ETABS model was developed. Several important assumptions were made during the modeling process All members, both lateral and gravity, were included in the model to increase stiffness and obtain more accurate results. Also, Wind and seismic load cases were input into ETABS as separate load combinations Stephan Northrop Structural Option

Wind & Seismic Loading Application
North Shore Equitable Building Proposed Lateral System Building Introduction Existing Building Information Problem Statement Proposed Solution Structural Depth Codes & Loads Proposed Gravity System Proposed Lateral System Foundation Assessment Acoustic Analysis Breadth Conclusion Acknowledgements & Questions Wind & Seismic Loading Application Wind Forces Calculated using ASCE 7-05 MWFRS North/South direction controls due to a larger exposure area Wind loads calculated using the ASCE 7-05 Main wind force resisting system. Stephan Northrop Structural Option

Wind & Seismic Loading Application
North Shore Equitable Building Proposed Lateral System Building Introduction Existing Building Information Problem Statement Proposed Solution Structural Depth Codes & Loads Proposed Gravity System Proposed Lateral System Foundation Assessment Acoustic Analysis Breadth Conclusion Acknowledgements & Questions Wind & Seismic Loading Application Seismic Forces Calculated using ASCE 7-05 Controls over wind due to building weight R = 3.0 for ordinary concrete moment frames CuTa = 1.76 s (controlling period) Seismic Loads calculated using ASCE 7-05’s equivalent lateral force procedure. Both wind and seismic forces were user defined in the ETABS model. Stephan Northrop Structural Option

Relative Stiffness & Center of Rigidity
North Shore Equitable Building Proposed Lateral System Building Introduction Existing Building Information Problem Statement Proposed Solution Structural Depth Codes & Loads Proposed Gravity System Proposed Lateral System Foundation Assessment Acoustic Analysis Breadth Conclusion Acknowledgements & Questions Relative Stiffness & Center of Rigidity Stiffness of moment frames range from (K/in) to (K/in) Center of mass at center point of building Very little eccentricity due to symmetrical design Stephan Northrop Structural Option

Proposed Lateral System Building Introduction Existing Building Information Problem Statement Proposed Solution Structural Depth Codes & Loads Proposed Gravity System Proposed Lateral System Foundation Assessment Acoustic Analysis Breadth Conclusion Acknowledgements & Questions Story Deflections Stephan Northrop Structural Option

Existing Pile Cap Design
North Shore Equitable Building Foundation Assessment Building Introduction Existing Building Information Problem Statement Proposed Solution Structural Depth Codes & Loads Proposed Gravity System Proposed Lateral System Foundation Assessment Acoustic Analysis Breadth Conclusion Acknowledgements & Questions Existing Pile Cap Design Redesigned Pile Cap Existing System 18” Auger cast piles (290 K capacity) 5 piles per typical pile cap Bearing capacity = 1450 K per pile cap Redesigned System K axial load per column ” piles per pile cap Stephan Northrop Structural Option

Acoustic Analysis Building Introduction Existing Building Information Problem Statement Proposed Solution Structural Depth Codes & Loads Proposed Gravity System Proposed Lateral System Foundation Assessment Acoustic Analysis Breadth Conclusion Acknowledgements & Questions Noise Sources under consideration 95 dB subway below grade 71 dB passenger car at parking sublevel Mechanical system at roof level Target dB value at level 1 = 38 dB or less Calculations Performed Transmission Loss through S.O.G. and parking level STL comparison of new and existing roof structures Stephan Northrop Structural Option

Acoustic Analysis Building Introduction Existing Building Information Problem Statement Proposed Solution Structural Depth Codes & Loads Proposed Gravity System Proposed Lateral System Foundation Assessment Acoustic Analysis Breadth Conclusion Acknowledgements & Questions Noise Sources under consideration 95 dB subway noise at level 1 71 dB passenger car noise at level 1 Mechanical noise at roof level Calculations Performed STL at parking sublevel STL at Level 1 STL comparison of new and existing roof structures Target dB value at level 1 = 38 dB or less Stephan Northrop Structural Option

Acoustic Analysis Building Introduction Existing Building Information Problem Statement Proposed Solution Structural Depth Codes & Loads Proposed Gravity System Proposed Lateral System Foundation Assessment Acoustic Analysis Breadth Conclusion Acknowledgements & Questions Conclusions Noise transmission is not an issue in the redesigned system Noise reduction is improved at the roof level Noise reduction is improved in the redesign: Increase in slab thickness and density Increase in building weight leads to decreased vibrations Stephan Northrop Structural Option

Drawbacks to redesigned Structure All Project Goals were achieved
North Shore Equitable Building Conclusion Building Introduction Existing Building Information Problem Statement Proposed Solution Structural Depth Codes & Loads Proposed Gravity System Proposed Lateral System Foundation Assessment Acoustic Analysis Breadth Conclusion Acknowledgements & Questions Drawbacks to redesigned Structure Excessively large column and girder sizes Increased building weight Increase construction time Final Conclusion: Costs outweigh benefits Existing structure is the most economical All Project Goals were achieved Noise control is improved Existing grid layout is maintained Additional Benefit: Construction cost is decreased Stephan Northrop Structural Option

Acknowledgements Building Introduction Existing Building Information Problem Statement Proposed Solution Structural Depth Codes & Loads Proposed Gravity System Proposed Lateral System Foundation Assessment Acoustic Analysis Breadth Conclusion Acknowledgements & Questions Primary Project Team: Mike Hudec Continental Real-Estate Robert Modany Continental Real-Estate Dina Snider Strada Architects Ken Ash Michael Baker Louis Mittleman Michael Baker The Pennsylvania State University: Dr. Linda Hanagan Prof. M Kevin Parfitt Prof. Robert Holland Ryan Solnosky, Shaun Kreidel and Dr. Andres Lepage The entire AE faculty and staff A special thank you to my friends and family for their constant support Stephan Northrop Structural Option

Building Introduction Existing Building Information Problem Statement Proposed Solution Structural Depth Codes & Loads Proposed Gravity System Proposed Lateral System Foundation Assessment Acoustic Analysis Breadth Conclusion Acknowledgements & Questions Questions & Comments Stephan Northrop Structural Option

Final Thesis Presentation Stephan Northrop Structural Option

Additional Information Stephan Northrop Structural Option

Figure 5-15: East/West Wind Pressure Elevation View
North Shore Equitable Building Additional Information Figure 5-15: East/West Wind Pressure Elevation View Stephan Northrop Structural Option

Additional Information E/W wind story forces N/S wind story forces Stephan Northrop Structural Option

Additional Information E/W Seismic story forces Stephan Northrop Structural Option

North Shore Equitable Building

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