tailieunhanh - Theory and Problems of Strength of Materials Part 10

Tham khảo tài liệu 'theory and problems of strength of materials part 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 266 ELASTIC DEFLECTION OF BEAMS METHOD OF SINGULARITY FUNCTIONS ỊCHAP. 10 As the first boundary condition we have dy2ldx - 0 at A 0 which when substituted in Eq. 3 yields C - 0. Integrating a second time we obtain _ 5 . .2 . wt Lx3 wo x The second boundary condition y 0 at A- 0 leads upon substitution in Eq. 4 to c2 - 0. Thus the beam deflection equation is _ 5 wltL Bly - a 12 w0 WfiL1 3L 2 20 A T 4 4 7 5 The deflection at the tip. A L. is found from Eq. 5 to be EIy I L - L4 Using singularity functions determine the equation of the deflection curve of the beam simply supported at points B and c and subject to the triangular loading shown in Hg. 10-8. To determine the external vertical reactions at points B and c we may replace the entire loading by its resultant which acts through the centroid of the triangle. The magnitude of the entire load is the average load per unit length w0 2. multiplied by the beam length L or w0L 2. This acts at a distance 2L 3 from the left end A and is shown by the dotted vector in Fig. 10-8. From statics 2 2 3 4 Therefore Ri n _ _ 5w0L WOL SF. 12 2 Therefore 12 At any station A measured from the origin at A the bending moment in terms of singularity functions is given as the sum of the moments of all forces to the left of that station. Let US examine a portion of the CHAP. 10 ELASTIC DEFLECTION OF BEAMS METHOD OF SINGULARITY FUNCTIONS 267 triangular load of horizontal length X. The resultant of that much of the loading is shown by the dotted vector in Fig. 10-9 and the resultant is of magnitude w A A iX -L 2 and acts at a point distance JA from A. Thus the moment at X due only to the triangular loading is X A or 6Ỉ. where the minus sign is inserted because according to our bending moment sign conventions in Chap. 6 downward loads give rise to negative bending moment. Fig. Ỉ0-9 In terms of singularity functions the bending moment at any station A due to all loadings including reactions is . _ H nU irnL _ L 5wuL 3L 6L 12 4 12

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