Structural Loads Part 2 Civil Engineering and Architecture

Structural Loads Part 2 Civil Engineering and Architecture Unit 6 Structures

In this lesson: Solve the Building Design Problem “Chase” the Load Calculate Beam and Girder Loading Select the Beam and Girder Size the footings

Building Design Problem A Steel Framed Retail Building with Concrete Floors and Flat Roof Please click here to obtain Revit file of the building.

Second Floor Framing Girder Beam Footing Column

Design Steps

Load Chasing for this Problem Calculate beam loading, obtain reactions Transfer reaction loads to girder Carry girder reactions to column then to footing

Foundation Plan

Partial nd 2 Design Area Floor Framing Plan

Tributary or Contributing Area Column B-3 Girder 3 BC Beam B. 3 6’ 8” Width

Calculating Beam Loading Please click here to obtain “Steps for Calculating Beam Loading. ”

Dead and Live Load Documents Click Here for the Live Load Sheet Click Here for the Dead Load Sheet

2 nd Floor Beam, Girder Calculations 2 nd Floor Loading for Beam B. 3 - Dead Load Span Length 18’-0” Dead Load 4” thick concrete slab Flooring- Ceramic Tile Partitions (Drywall with metal stud) Suspended Ceiling Mechanical/ Electrical Items Total DL Assumed Dead Load Weight of Beam: 20 lb/ft 50 lb/ft 2 10 lb/ft 2 8 lb/ft 2 2 lb/ft 2 10 lb/ft 2 80 lb/ft 2

2 nd Floor Beam, Girder Calculations 2 nd Floor Loading for Beam B. 3 - Live Load Retail Space 80 lb/ft 2 Total Load DL + LL (per lineal foot of beam) [80 lb/ft 2 + 80 lb/ft 2 ] x 6. 67 ft = 1067. 2 lb/ft Add the Beam Weight of 20 lb/ft Total DL + LL + Beam Weight = 1087. 2 lb/ft Use 1090 lb/ft

2 nd Floor Beam B. 3 Calculations MD Solids Span Length is 18 feet. Uniform Load w = 1090 lb/ft

2 nd Floor Beam B. 3 Calculations MD Solids – Shear and Moment Diagrams Shear Moment

Allowable Bending Stress = Fb Fb = (Yield Strength) A 36 Structural Steel – 36, 000 psi Fb = (36, 000 psi) = 24, 000 psi Fb = (50, 000 psi) = 33, 000 psi

Section Modulus = M = 44, 145 ft-lbs Fb = 24, 000 psi = SRequired = 22. 073 in 3

MDSolids Design Results B. 3

Design Results for B. 3 - con.

Beam B. 3 Deflection limited to: 216 in = 0. 6 in 360 Professional Development Lesson ID Code: 8009

Beam B. 3 Comparisons Beam Sz (in 3) Deflection (inches) W 10 x 22 23. 2 0. 7523 W 12 x 22 25. 4 0. 5691 W 14 x 22 29. 0 0. 4461 W 10 x 26 27. 9 0. 6165 W 12 x 26 33. 4 0. 4352 W 14 x 26 33. 5 0. 3624 SELECT

Girder 3 BC Calculations Beam B. 3 Span Length is 18 feet. Uniform Load = 1090 lb/ft P 1 = P 2 = (18 ft)(1090 lb/ft) P 1 = P 2 = 19, 620 lb.

Girder 3 BC Moment and Shear

Design Results Deflection Limit = = Deflection Limit = 0. 666” Girder Sz (in 3) Deflection (inches) W 16 x 45 72. 7 0. 5773 W 18 x 46 78. 8 0. 4761

Footing Calculations

Footing Loads Allowable Soil Bearing Capacity = 3000 lb/ft 2 Loads Considered Dead & Live load from 2 nd floor and roof Column’s weight (dead load) Load from 1 st floor slab Dead load from footing

Roof Load Roof Type: Corrugated Steel Deck with insulation and 5 ply membrane roof and gravel, located in Rochester NY. Dead Load Suspended Ceiling Mechanical Equipment Steel Deck Insulation Roof Membrane and Gravel Roof Framing Total DL 2 lb/ft 2 10 lb/ft 2 5 lb/ft 2 2 lb/ft 2 6 lb/ft 2 10 lb/ft 2 35 lb/ft 2

Roof Load – Snow Load Rochester, NY 55 lb/ft 2 Total Load on Roof DL + SL = 35 lb/ft 2 + 55 lb/ft 2 = 90 lb/ft 2 Axial Load on Column B-3 from Roof Tributary Area of Roof = 18 ft x 20 ft = 360 ft 2 (DL + SL)(Trib. Area) = (90 lb/ft 2)(360 ft 2) = 32, 400 lb

Loads on Column and Footing Roof Loads Column B-3 2 nd Floor Loads 1 st Floor/ Slab Loads Soil Bearing Reaction

Loads on Column - Footing Loads on the Column 2 nd Floor Girder x 2 = 2(20, 120 lb) Beams x 2 = 2(9, 810 lb) Roof Concentrated Load Column Self Weight 21 ft x 50 lb/ft (estimated) Total Use 94, 000 lbs = = 40, 240 lb 19, 620 lb = 32, 400 lb = 1, 050 lb 93, 310 lb

Soil Bearing Capacity Available Allowable Soil Bearing Capacity = 3000 lb/ft 2 Footing wt. = (1 ft)(150 lb/ft 3) = 150 lb/ft 2 Soil Capacity Available = 3000 lb/ft 2 - 150 lb/ft 2 = 2850 lb/ft 2 = qnet

Sizing the Footing Load Column Footing = 94, 000 lbs Soil Capacity Available = 2850 lb/ft 2 = qnet Use 6’-0” x 6’-0” Square Footing

The Solutions: Beam B. 3 W 12 x 22 Girder B 3 B W 16 x 45 Footing under Column B-3 6’ x 6’

Curriculum Alignment: Unit 6 – Structural Engineering Lesson 6. 1 – Introduction to Structural Engineering Act. 1. 1 – Structural Calculations Act. 1. 2 – More Load Calculations Lesson 6. 2 – Roof Systems Lesson 6. 3 – Columns and Beams

References: Jefferis, A. & Madsen, D. A. (2001). Architectural Drafting and Design, Albany, NY: Delmar Kane, K. & Onouye B. , (2002). Statics and Strength of Materials for Architecture and Building Construction, 2 nd ed. , Saddle River, NJ: Pearson Education, Inc Shaeffer, R. E. (2002). Elementary Structures for Architects and Builders, 4 th ed. . Columbus, OH: Prentice Hall Manual of Steel Construction, 8 th ed. , American Institute of Steel Construction http: //pbs. org/wgbh/buildingbig/lab/forces. html

Credits: Writer: Constance Bertucci Content Editor: Donna E. Scribner Narration: Donna E. Scribner PLTW Editor: Ed Hughes Production: CJ Amarosa Video Production: CJ Amarosa Audio: CJ Amarosa Project Manager: Donna E. Scribner