12.1-b - Lecture 12.1: Two-way Slabs CSA A23.3 Clauses p....

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Lecture 12.1: Two-way Slabs – CSA A23.3 Clauses p. 10 Lecture 12.1: Two-way Slabs – CSA A23.3 Clauses p. 10 The Direct Design Method The Direct Design Method is suitable for two-way slab systems on flexible supports. We will focus on the design of flat-plate slabs using this technique. The Direct Design Method is only applicable under certain conditions as listed in Clause 13.9.1 of the CSA A23.3 Standard: There must be a minimum of three consecutive spans in each direction Successive spans in each direction shall not differ by more than one-third of the long span All loads must be due to gravity only and uniformly distributed The factored live load shall not exceed twice the factored dead load If all these requirements are met one can use the Direct Design Method, otherwise one will have to use another method to determine the moments. 13.9 Direct design method 13.9.1 Limitations 13.9.1.1 Regular two-way slab systems (see Clause 2.2 ) that comply with the limitations specified in Clauses 13.9.1.2 to 13.9.1.5 may be designed using the direct design method. Note: It is possible that in some circumstances the requirements specified in Clauses 13.9.1.2 to 13.9.1.5 will not address concerns related to slab systems with drop panels and/or beams as rigorously as the requirements specified in Clause 13.8 . 13.9.1.2 There shall be a minimum of three continuous spans in each direction. 13.9.1.3 Successive span lengths centre-to-centre of supports in each direction shall not differ by more than one-third of the longer span. 13.9.1.4 All loads shall be due to gravity only and uniformly distributed over an entire panel. The factored live load shall not exceed twice the factored dead load. 13.9.1.5 Variations from the limitations of Clauses 13.9.1.2 to 13.9.1.4 shall be acceptable if it is demonstrated by analysis that the requirements specified in Clause 13.5.1 are satisfied.
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Lecture 12.1: Two-way Slabs – CSA A23.3 Clauses p. 11 Lecture 12.1: Two-way Slabs – CSA A23.3 Clauses p. 11 1. Moments using the Direct Design method As mentioned earlier, for the design of two way slabs we have different methods that we can use to determine the design moments on the slab. In the direct design method, moments are obtained using moment coefficients For design, the slab is considered a series of frames in two directions . These frames extend to the middle of the panels on each side of the column lines
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Lecture 12.1: Two-way Slabs – CSA A23.3 Clauses p. 12 Lecture 12.1: Two-way Slabs – CSA A23.3 Clauses p. 12 (Step 1) In each span of these “frames” it is necessary to calculate the total static moment , M o , as given in Clause 13.9.2.2 . 8
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This note was uploaded on 04/19/2011 for the course CIVE 463 taught by Professor Mirza during the Winter '10 term at McGill.

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12.1-b - Lecture 12.1: Two-way Slabs CSA A23.3 Clauses p....

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