Forging new generations of engineers Beams and Columns Civil Engineering and ArchitectureTM Unit 6 – Lesson 6.1 – Intro to Structural Engineering Forging new generations of engineers Project Lead The Way, Inc. Copyright 2007

BEAMS AND COLUMNS

A “good” design? The building dead load is the only known load. All other forces will vary in magnitude, duration and location. The building is designed for design load possibilities that may never occur. The structural efficiency of a building is measured as the ratio of dead to live load.The building designer strives to keep the ratio low.

Beam Design Beams are used in floors and roofs. Maybe called floor joists, stringers, floor beams or girders. Loads on beams are either concentrated or distributed (uniform loads) Designed for Shear, Moment (bending) and Deflection

Beams Beams are sized appropriately to safely support the loads a structure will carry. Beams are primarily subjected to bending and shear. Deflection and deformation can be calculated. Beams are sized to provide the maximum result with the minimum materials. A factor of safety is included in the design.

Beam Deflection Limit Deflection to WHY?? L/240 of total load (whereas L=length in inches) L/300 of total load L/360 of total load (building use throughout life is unknown) Preferred WHY?? Ceiling cracks in plaster Roof ponding (flat roofs) Visual or psychological reasons Designer’s judgment

Beam Types Simple Continuous Cantilever Moment (fixed at one end)

Beam Types Fixed Moments at each end Propped- Fixed at one end supported at other Overhang

Forces and Supports Supports are translated into forces and moments in a free body diagrams. The following are three common supports and the forces and moments used to replace them. Roller: Pin Connection: Fixed Support: F y x M o

Columns Columns carry primary Axial Loads and therefore are designed for compression. Additional loads from snow, wind or other horizontal forces can cause bending in the columns. Columns then need to be designed for Axial Load and Bending.

Forces F (External) WCOL (External) R1 (Internal) R2 (Internal) RSoil (External) WFTG (External) Forces F (External) WCOL (External) R3 (Internal) Column R2 (Internal) WFTG (External) R4(Internal) Footing

Reference Sources Jefferis, A., & Madsen, D. A. (2001). Architectural Drafting and Design. Albany, NY: Delmar, a division of Thomson Learning. Kane, K., & Onouye, B., (2002). Statics and Strength of Materials for Architecture and Building Construction.(2nd ed.). Saddle River, NJ: Pearson Education, Inc Shaeffer, R. E., (2002). Elementary Structures for Architects and Builders (4th ed.). Columbus, OH: Prentice Hall. http://www.concretenetwork.com/concrete/footing_fundamentals/why_soils_matter.htm http://www.emporis.com/en/ http://www.pbs.org/wgbh/buildingbig/lab/forces.html