Riverview Heights Darren K. Howard Structural Option Architectural Engineering Spring Thesis 2005 Advisor: Dr. Ali Memari

Riverview Heights Darren K. Howard Structural Option 1.0 Project Background 2.0 Problem Statement 3.0 Solution Overview 4.0 Structural Redesign 5.0 Mechanical Issues 6.0 Acoustical Issues 7.0 Cost Estimates 8.0 Conclusions and Recommendations Acknowledgements Questions Table of Contents:

Riverview Heights Darren K. Howard Structural Option 1.0 PROJECT BACKGROUND

Riverview Heights Darren K. Howard Structural Option 1.0 Project Background: Conshohocken, Pennsylvania 4 apartment levels 2 levels of partially underground parking

Riverview Heights Darren K. Howard Structural Option 1.1 Apartment Structural Systems: Bearing Walls: Wood stud walls Floor: 20” deep, floor trusses Lateral System: Wood Panel Shear Walls

Riverview Heights Darren K. Howard Structural Option 1.1 Parking Structural Systems: Elevated Two-Way concrete slab with drop panels Top slab is a 11” thick “transfer slab” “Transfer slab” picks up random bearing wall loads Concrete columns send loads to spread footings

Riverview Heights Darren K. Howard Structural Option 2.0 PROBLEM STATEMENT

Riverview Heights Darren K. Howard Structural Option 2.0 Problem Statement Lumber is a renewable, but not unlimited resource New building materials will eventually become necessary Alternative materials and methods must be found

Riverview Heights Darren K. Howard Structural Option 3.0 SOLUTION OVERVIEW

Riverview Heights Darren K. Howard Structural Option 3.0 Solution Overview Cold-formed steel buildings are growing in popularity Recyclable material Not susceptible to termite damage Will not burn or harbor mold Will not rot, shrink, warp or split Prices for cold-formed steel have been more stable than lumber Construction methods are very similar to wood framing

Riverview Heights Darren K. Howard Structural Option 4.0 STRUCTURAL REDESIGN

Riverview Heights Darren K. Howard Structural Option 4.0 Structural Redesign Replace existing bearing walls with cold-formed studs Replace wood floor trusses with cold-formed joists Investigate the use of possible lateral systems:  Wood panel shear walls over cold-formed studs  Lateral strap bracing

Riverview Heights Darren K. Howard Structural Option 4.1 BEARING WALLS

Riverview Heights Darren K. Howard Structural Option 4.1 Bearing Wall Redesign Existing bearing walls and unit separation walls:

Riverview Heights Darren K. Howard Structural Option 4.1 Bearing Wall Redesign Design Considerations:  Replace existing unit separation walls with a single cold-formed stud wall  Set studs at a spacing of 24” o.c. rather than 16” o.c.

Riverview Heights Darren K. Howard Structural Option 4.1 Bearing Wall Redesign Redesigned Walls:  Unit separation walls: 6” wide 24” o.c.  Interior bearing walls: 3-5/8” 24” o.c.  Gauge of stud varies from floor to floor

Riverview Heights Darren K. Howard Structural Option 4.1 Bearing Wall Redesign FloorStudLoad (kips)Allowable (kips) Unit Separation Walls

Riverview Heights Darren K. Howard Structural Option 4.1 Bearing Wall Redesign FloorStudLoad (kips)Allowable (kips) Interior Unit Bearing Walls

Riverview Heights Darren K. Howard Structural Option 4.2 FLOOR SYSTEM

Riverview Heights Darren K. Howard Structural Option 4.2 Floor System Redesign Existing Floor: 16’ to 25’ interior spans

Riverview Heights Darren K. Howard Structural Option 4.2 Floor System Redesign Design considerations:  Cold-formed steel joists should require less depth  This will add additional floor-to-floor height in units

Riverview Heights Darren K. Howard Structural Option 4.2 Floor System Redesign Redesigned Joists: 14j10 Marino/Ware Joists  14” deep, 10 gauge 24” o.c.  Allowable p.l.f. = 130 p.l.f. (  L/360)  An additional 6” of floor-to-floor height is achieved

Riverview Heights Darren K. Howard Structural Option 4.3 LATERAL RESISTANCE

Riverview Heights Darren K. Howard Structural Option 4.3 Lateral System Redesign Existing Lateral System: Wood Shear Panel Walls

Riverview Heights Darren K. Howard Structural Option 4.3 Lateral System Redesign Design Considerations:

Riverview Heights Darren K. Howard Structural Option Lateral System Redesign Alternative #1: Wood shear panels over cold-formed studs  Greater strength = fewer shear walls required FloorWoodCF Steel # of Shear Walls Required

Riverview Heights Darren K. Howard Structural Option Lateral System Redesign Alternative #2: Lateral Strap Bracing

Riverview Heights Darren K. Howard Structural Option Lateral System Redesign Alternative #2: Lateral Strap Bracing STAAD frame model of tension braces

Riverview Heights Darren K. Howard Structural Option Lateral System Redesign FloorLateral Strap SizesAllowable Load (kips) 42” x 18ga (both sides) ” x 18ga (both sides) ” x 18ga (both sides) ” x 18ga (both sides)7.14

Riverview Heights Darren K. Howard Structural Option 5.0 MECHANICAL

Riverview Heights Darren K. Howard Structural Option 5.0 Mechanical Issue Major disadvantage of cold-formed steel  Thermal conductivity HOT COLD

Riverview Heights Darren K. Howard Structural Option 5.0 Mechanical Issue Add a thermal break between the exterior and interior space An additional layer of 1” rigid insulation must be installed

Riverview Heights Darren K. Howard Structural Option 5.0 Mechanical Issue Wall AssemblyClear-Wall R-ValueWhole-Wall R-Value Existing Wall: 2x4 Studs, 16” o.c., R-11 batts, ½” ext. plywood, ½” int. gypsum CF Wall (no thermal break) 3 ½” steel studs, 24” o.c., R-11 batts, ½” ext. plywood, ½” int. gypsum CF Wall (thermal break) 3 ½” steel studs, 24” o.c., R-11 batts, ½” ext. plywood, ½” int. gypsum, 1” rigid insulation over ext. plywood

Riverview Heights Darren K. Howard Structural Option 6.0 ACOUSTICS

Riverview Heights Darren K. Howard Structural Option 6.0 Acoustics Cold-formed studs have lower acoustical properties Riverview Heights was designed as an “average” site Unit separation walls and floors need to meet an STC rating of 52

Riverview Heights Darren K. Howard Structural Option 6.0 Acoustics An additional 5/8” of gypsum is required on both sides of walls to meet acoustical requirements Existing wood floor trusses and the redesigned joists required resilient channels on the ceiling side

Riverview Heights Darren K. Howard Structural Option 6.0 Acoustics SystemSTC rating CF Unit Separation Walls and Corridor Walls 57 Existing Walls53 CF Floor Assembly56 Existing Floor57

Riverview Heights Darren K. Howard Structural Option 7.0 COST ESTIMATES

Riverview Heights Darren K. Howard Structural Option 7.0 Cost Estimates Estimate of Wood Framing SystemCost Wood Panel Shear Walls$70, x4 Stud Walls$553, Floor Trusses$241, Total Cost$780,340.20

Riverview Heights Darren K. Howard Structural Option 7.0 Cost Estimates Estimate of Cold-Formed Framing SystemCost Wood Panel Shear Walls$52, Lateral Strap Bracing$51, Cold-formed Joists$710,955 Cold-formed Stud Walls$383, Total with Either Lateral System$1,146,830.20

Riverview Heights Darren K. Howard Structural Option 7.0 Cost Estimates Cold-Formed Framing Additional Costs SystemCost 1” rigid insulation$27,000 Additional layer of 5/8” drywall on walls $ Total$80, Total Cold-Formed Cost$1,227,538.60

Riverview Heights Darren K. Howard Structural Option 7.0 Cost Estimates Total Costs SystemCost Wood Framing$780, Cold-Formed Framing$1,227, Difference in cost- $447, CF joists are more than twice the cost of wood floor trusses!!

Riverview Heights Darren K. Howard Structural Option 7.0 Cost Estimates Total Costs without Floor Systems SystemCost Wood Framing minus Floor System $538, Cold-Formed Framing minus Floor System $516, Difference in Cost+ $22,109.60

Riverview Heights Darren K. Howard Structural Option CONCLUSIONS AND RECOMMENDATIONS

Riverview Heights Darren K. Howard Structural Option 8.0 Conclusions and Recommendations Cold-formed framing is a viable solution if the redesigned floor framing is not included Cost of the cold-formed floor framing was more than twice the cost of wood trusses Cold-formed framing used less material in walls and in lateral systems Using less material translated into lower costs Promising conclusion as the need for alternative building materials becomes greater in the next century

Riverview Heights Darren K. Howard Structural Option Acknowledgements My family and friends A.E. faculty Staff of Cates Engineering Trammel Crow Residential Minno & Wasko Architects Marino/Ware Images courtesy of Marino/Ware, Cates Engineering, and Minno & Wasko Architects

Riverview Heights Darren K. Howard Structural Option Questions?