01-02ChapGere.0026

01-02ChapGere.0026 - d 5 250 mm and supports a load P 5 750...

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Solution 1.8-12 Hollow circular column SECTION 1.8 Design for Axial Loads and Direct Shear 57 d 5 250 mm P 5 750 kN s allow 5 55MPa (compression in column) t 5 thickness of column D 5 diameter of base plate ± b 5 11.5MPa (allowable pressure on concrete) (a) T HICKNESS t OF THE COLUMN (Eq. 1) t 2 2 dt 1 P p s allow 5 0 p t 2 2 p td 1 P s allow 5 0 p t ( d 2 t ) 5 P s allow 5 p 4 (4 t )( d 2 t ) 5 p t ( d 2 t ) A 5 P s allow Ê A 5 p d 2 4 2 p 4 ( d 2 2 t ) 2 S UBSTITUTE NUMERICAL VALUES IN E Q . (1): (Note: In this eq., t has units of mm.) t 2 2 250 t 1 4,340.6 5 0 Solve the quadratic eq. for t : (b) D IAMETER D OF THE BASE PLATE For the column, P allow 5 s allow A where A is the area of the column with t 5 20mm. A 5 p t ( d 2 t ) P allow 5 s allow p t ( d 2 t ) D min 5 297 mm D 2 5 88,000 mm 2 Ê D 5 296.6 mm 5 4(55 MPa)(20 mm)(230 mm) 11.5 MPa D 2 5 4 s allow t ( d 2 t ) s b p D 2 4 5 s allow p t ( d 2 t ) s b Area of base plate 5 p D 2 4 5 P allow s b Use t 5 20 mm t 5 18.77 mm Ê t min 5 18.8 mm t 2 2 250 t 1 (750 3 10 3 N) p (55 N / mm 2 ) 5 0 P t D d Problem 1.8-12 A steel column of hollow circular cross sec- tion is supported on a circular steel base plate and a concrete pedestal (see figure). The column has outside diameter
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Unformatted text preview: d 5 250 mm and supports a load P 5 750 kN. (a) If the allowable stress in the column is 55 MPa, what is the minimum required thickness t ? Based upon your result, select a thickness for the column. (Select a thickness that is an even integer, such as 10, 12, 14, . . ., in units of millimeters.) (b) If the allowable bearing stress on the concrete pedestal is 11.5 MPa, what is the minimum required diameter D of the base plate if it is designed for the allowable load P allow that the column with the selected thickness can support? Column Base plate P P t D d A-PDF Split DEMO : Purchase from www.A-PDF.com to remove the watermark...
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