Riverview Heights Darren K. Howard Structural Option Architectural - - PowerPoint PPT Presentation

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Riverview Heights Darren K. Howard Structural Option Architectural - - PowerPoint PPT Presentation

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Riverview Heights Darren K. Howard Structural Option Architectural Engineering Spring Thesis 2005 Advisor: Dr. Ali Memari Riverview Heights Darren K. Howard Structural Option Table of Contents: 1.0 Project Background 2.0 Problem

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Riverview Heights

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

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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:

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Riverview Heights

Darren K. Howard Structural Option

1.0 PROJECT BACKGROUND

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Riverview Heights

Darren K. Howard Structural Option 1.0 Project Background:

  • Conshohocken, Pennsylvania
  • 4 apartment levels
  • 2 levels of partially underground parking
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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
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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
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Riverview Heights

Darren K. Howard Structural Option

2.0 PROBLEM STATEMENT

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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
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Riverview Heights

Darren K. Howard Structural Option

3.0 SOLUTION OVERVIEW

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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
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Riverview Heights

Darren K. Howard Structural Option

4.0 STRUCTURAL REDESIGN

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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

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Riverview Heights

Darren K. Howard Structural Option

4.1 BEARING WALLS

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Riverview Heights

Darren K. Howard Structural Option 4.1 Bearing Wall Redesign

  • Existing bearing walls and unit separation walls:
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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.

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Riverview Heights

Darren K. Howard Structural Option 4.1 Bearing Wall Redesign

  • Redesigned Walls:

Unit separation walls: 6” wide studs @ 24” o.c. Interior bearing walls: 3-5/8” studs @ 24” o.c. Gauge of stud varies from floor to floor

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Riverview Heights

Darren K. Howard Structural Option 4.1 Bearing Wall Redesign 11.51 8-11 6SW-12@24” 1 11.51 6-8 6SW-12@24” 2 7.56 5.3-6.6 6SW-14@24” 3 5.73 3.2-4.4 6SW-16 @24” 4 Allowable (kips) Load (kips) Stud Floor Unit Separation Walls

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Riverview Heights

Darren K. Howard Structural Option 4.1 Bearing Wall Redesign

7.32 5-6 358SW-12@24” 1 5.12 4-4.48 358SW-14@24” 2 4.05 3-3.6 358SW-16@24” 3 2.75 2-2.4 358SW-18 @24” 4

Allowable (kips) Load (kips) Stud Floor Interior Unit Bearing Walls

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Riverview Heights

Darren K. Howard Structural Option

4.2 FLOOR SYSTEM

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Riverview Heights

Darren K. Howard Structural Option 4.2 Floor System Redesign

  • Existing Floor: 16’ to 25’ interior spans
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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

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Riverview Heights

Darren K. Howard Structural Option 4.2 Floor System Redesign

  • Redesigned Joists: 14j10 Marino/Ware Joists

14” deep, 10 gauge joists @ 24” o.c. Allowable p.l.f. = 130 p.l.f. ( δ < L/360) An additional 6” of floor-to-floor height is achieved

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Riverview Heights

Darren K. Howard Structural Option

4.3 LATERAL RESISTANCE

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Riverview Heights

Darren K. Howard Structural Option 4.3 Lateral System Redesign

  • Existing Lateral System: Wood Shear Panel Walls
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Riverview Heights

Darren K. Howard Structural Option 4.3 Lateral System Redesign

  • Design Considerations:
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Riverview Heights

Darren K. Howard Structural Option 4.3.1 Lateral System Redesign

  • Alternative #1: Wood shear panels over cold-formed studs

Greater strength = fewer shear walls required

36 36 1 33 36 2 25 36 3 22 36 4 CF Steel Wood Floor # of Shear Walls Required

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Riverview Heights

Darren K. Howard Structural Option 4.3.2 Lateral System Redesign

  • Alternative #2: Lateral Strap Bracing
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Riverview Heights

Darren K. Howard Structural Option 4.3.2 Lateral System Redesign

  • Alternative #2: Lateral Strap Bracing
  • STAAD frame model of tension braces
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Riverview Heights

Darren K. Howard Structural Option 4.3.2 Lateral System Redesign 7.14 4” x 18ga (both sides) 1 7.14 4” x 18ga (both sides) 2 3.56 2” x 18ga (both sides) 3 3.56 2” x 18ga (both sides) 4 Allowable Load (kips) Lateral Strap Sizes Floor

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Riverview Heights

Darren K. Howard Structural Option

5.0 MECHANICAL

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Riverview Heights

Darren K. Howard Structural Option 5.0 Mechanical Issue

  • Major disadvantage of cold-formed steel

Thermal conductivity

HOT COLD

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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
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Riverview Heights

Darren K. Howard Structural Option 5.0 Mechanical Issue

10.2 13.3

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

7.1 9.4

CF Wall (no thermal break)

3 ½” steel studs, 24” o.c., R-11 batts, ½” ext. plywood, ½” int. gypsum

9.6 10.6

Existing Wall:

2x4 Studs, 16” o.c., R-11 batts, ½”

  • ext. plywood, ½” int. gypsum

Whole-Wall R-Value Clear-Wall R-Value Wall Assembly

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Riverview Heights

Darren K. Howard Structural Option

6.0 ACOUSTICS

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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

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Riverview Heights

Darren K. Howard Structural Option 6.0 Acoustics

  • An additional 5/8” of gypsum is required on both sides
  • f walls to meet acoustical requirements
  • Existing wood floor trusses and the redesigned joists

required resilient channels on the ceiling side

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Darren K. Howard Structural Option 6.0 Acoustics 57 Existing Floor 56 CF Floor Assembly 53 Existing Walls 57 CF Unit Separation Walls and Corridor Walls STC rating System

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Darren K. Howard Structural Option

7.0 COST ESTIMATES

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Riverview Heights

Darren K. Howard Structural Option 7.0 Cost Estimates Estimate of Wood Framing $780,340.20 Total Cost $241, 647.00 Floor Trusses $553, 316.40 2x4 Stud Walls $70,502.40 Wood Panel Shear Walls Cost System

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Riverview Heights

Darren K. Howard Structural Option 7.0 Cost Estimates Estimate of Cold-Formed Framing $1,146,830.20 Total with Either Lateral System $383,875.92 Cold-formed Stud Walls $710,955 Cold-formed Joists $51,984.00 Lateral Strap Bracing $52,387.20 Wood Panel Shear Walls Cost System

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Riverview Heights

Darren K. Howard Structural Option 7.0 Cost Estimates Cold-Formed Framing Additional Costs $1,227,538.60 Total Cold-Formed Cost $80,707.68 Total $53.707.68 Additional layer of 5/8” drywall on walls $27,000 1” rigid insulation Cost System

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Riverview Heights

Darren K. Howard Structural Option 7.0 Cost Estimates Total Costs

  • $447,198.40

Difference in cost $1,227,538.60 Cold-Formed Framing $780,340.20 Wood Framing Cost System CF joists are more than twice the cost of wood floor trusses!!

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Riverview Heights

Darren K. Howard Structural Option 7.0 Cost Estimates Total Costs without Floor Systems + $22,109.60 Difference in Cost $516,583.60 Cold-Formed Framing minus Floor System $538,693.20 Wood Framing minus Floor System Cost System

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Darren K. Howard Structural Option

CONCLUSIONS AND RECOMMENDATIONS

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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

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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

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Riverview Heights

Darren K. Howard Structural Option Questions?