AECT480-Lecture%207

# AECT480-Lecture%207 - Lecture 7 Two-Way Slabs Two-way slabs...

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Lecture 7 – Page 1 of 13 Lecture 7 – Two-Way Slabs Two-way slabs have tension reinforcing spanning in BOTH directions, and may take the general form of one of the following: Types of Two-Way Slab Systems

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Lecture 7 – Page 2 of 13 The following Table may be used to determine minimum thickness of various two- way slabs based on deflection: Minimum Suggested Thickness “h” for Two-Way Slabs Two-Way Slab System: Minimum Thickness h: Flat plate L n /30 Flat plate with spandrel beams L n /33 Flat slab L n /33 Flat slab with spandrel beams L n /36 Two-way beam-supported slab L n /33 L n = clear distance in long direction Flat Plates Flat plates are the most common type of two-way slab system . It is commonly used in multi-story construction such as hotels, hospitals, offices and apartment buildings. It has several advantages: Easy formwork Simple bar placement Low floor-to-floor heights Direct Design Method of Flat Plates per ACI 318-02 Two-way slabs are inherently difficult to analyze by conventional methods of statics because of the two-way bending occurring. Accurately determining the moments on a two-way slab is typically accomplished by finite element computer analysis. Computer analysis of two-way slab
Lecture 7 – Page 3 of 13 The ACI 318 code allows a direct design method that can be used in most typical situations. However, the following limitations apply: 1. Must have 3 or more continuous spans in each direction. 2. Slab panels must be rectangular with a ratio of the longer span to shorter span(measured as centerline-to-centerline of support) not greater than 2.0. 3. Successive span lengths in each direction must not differ by more than 1/3 of the longer span. 4. Columns must not be offset by more than 10% of the span (in direction of offset) from either axis between centerlines of successive columns. 5. Loads must be uniformly distributed, with the unfactored live load not

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## This note was uploaded on 05/01/2010 for the course CEE 615 taught by Professor Parra during the Winter '09 term at University of Michigan-Dearborn.

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AECT480-Lecture%207 - Lecture 7 Two-Way Slabs Two-way slabs...

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