tailieunhanh - Structural Steel Designers Handbook Part 12

Tham khảo tài liệu 'structural steel designers handbook part 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | SECTION TWELVE be found by proportion from those previously calculated. Thus the moment at the support is 210 X MLL----------00302------------172 ft-klps and the moment at midspan is 110 X MLL --------0302----- 90 ft-kips . 3 2 Impact. For a 30-ft span impact is taken as 30 . At midspan M X 90 27 ft-kips. At supports M -172 -52 ft-kips. Total Floorbeam Moments. The design moments previously calculated are summarized in Table . Properties of Floorbeam Sections. For stress computations an effective width so of the deck plate is assumed to act as the top flange of member III. For determination of so the effective spacing of floorbeams Sf is taken equal to the actual spacing 180 in. The effective span le with the floorbeam ends considered fixed is taken as X 30 X 12 252 in. Hence Sf le 180 252 From Table for this ratio S- and s X 180 95 in sf Fig. and c . The neutral axis of the floorbeam sections at midspan and supports can be located by taking moments of component areas about middepth of the web. This computation and those for moments of inertia and section moduli are given in Table . Floorbeam Stresses. These are determined for the total moments in Table with the section properties given in Table . Calculations for the stresses at midspan and the supports are given in Table . Since the stresses are well within the allowable the floorbeam sections are satisfactory. TABLE Moments ft-kips in Floorbeam with Orthotropic-Plate Flange Mdl MLL M Total M Midspan 104 90 27 221 Supports 0 -712 -52 -224 BEAM AND GIRDER BRIDGES TABLE Floorbeam Moments of Inertia and Section Moduli a At midspan Material A d Ad Ad2 Io I Deck 95 X 381 4 070 4 070 Web 21 X 3 8 290 290 Bottom flange 10 X 1 -54 580 580 327 4 940 d 327 in X 327 -2 210 Ina 2 730 Distance from neutral axis to Top of deck plate - in Bottom of