1 / 22

Gravity Force Resisting Systems

CE 636 - Design of Multi-Story Structures T. B. Quimby UAA School of Engineering. Gravity Force Resisting Systems. Basic Elements. • Horizontal Systems (Floors & Roofs) – Joists, purlins , girders – One-way slabs – Two-way slabs – Waffle Slabs – Flat plates – Space Trusses

beauregard
Download Presentation

Gravity Force Resisting Systems

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CE 636 - Design of Multi-Story Structures T. B. Quimby UAA School of Engineering Gravity Force Resisting Systems

  2. Basic Elements • • Horizontal Systems (Floors & Roofs) • – Joists, purlins, girders • – One-way slabs • – Two-way slabs • – Waffle Slabs • – Flat plates • – Space Trusses • • Vertical Components • – Columns • – Load Bearing Walls • • Horizontal systems are generally unaffected by lateral loads • • Vertical components often are affected by both gravity and lateral loads.

  3. Joists, Girders, Purlins • The system consists of: • a horizontal slab or sheathed surface. • a system of beams (i.e. joists, purlins, girders) supporting the bearing surface. • columns or walls that support the beam system.

  4. Typical Floor Plan

  5. Some Typical Sections

  6. Steel Deck • Use manufacturers load tables. • Used without concrete for roof decks • Used with concrete for floor decks. • Lots of different profiles and gage thicknesses. • Design connection to supports for diaphragm shears

  7. Steel Joists • Use Manufacturer's Span Tables • Industry standards have been produced by the Steel Joist Institute. • Most manufacturers build their joist to SJI specifications

  8. One-Way Slabs • Slab spans between supports on two opposite sides • Generally true for slabs with an aspect ratio of 3:1 or more. • Analyzed and Designed as a beam without shear reinforcement.

  9. One-Way Slab and Beam Behavior • Reference #1, pg. 164

  10. Two-Way Slabs • Support on all edges. • May be “fixed” or “free” at supports. • Moments and shears are somewhat less than seen in one-way slabs of comparable span. • Precise analysis is somewhat complex.

  11. Approximate Flat Slab Behavior • Reference #1, pg. 15

  12. May use Stiff Beams for support • Reference #1, pg. 161

  13. Waffle Slabs • A grid consisting on beams running in two directions. • Slab spans between joists. • Easy to construct with reusable “pans”. • Fairly common in areas that use lots of concrete.

  14. Concrete Waffle Slab • Reference #1, pg. 192

  15. Waffle Slab Behavior • Reference #1, pg. 168

  16. Flat Plates • Slabs supported by columns only. • Slab is divided into strips. • Each strip is designed as a beam to carry a portion of the load. • Punching shear at columns is often a critical problem. • The problem becomes very complex if the columns are not laid out on a rectangular grid.

  17. Flat Slab Supported on Square Column Grid • Reference #1, pg. 163

  18. Punching Shear Resistance • Reference #1, pg. 169

  19. Space Trusses • Generally steel, sometimes wood or concrete. • Used mostly for exposed for roof structures. • Can be used to achieve many different shapes. • Often used for long span roof structures.

  20. Roof for a High School Gym • Reference #2, pg. 54

  21. Alternative Truss Layouts • Reference #1, pg. 198

  22. References • Lin, T.Y., and Stotesbury, S.D., Structural Concepts and Systems for Architects and Engineers, 2nd edition, Van Nostrand Reinhold, 1988. • Ambrose, J., Building Structures, Wiley Interscience, 1988. • Council on Tall Buildings & Urban Habitat, Advances in Tall Buildings, Van Nostrand Reinhold, 1986.

More Related