Tham khảo tài liệu 'bruhn - analysis and design of flight vehicles structures episode 2 part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | A14. 8 BENDING SHEAR STRESSES. SOUND AND OPEN SECTIONS. SHEAR CENTER. inches to left of point b as shown in Fig. . For bending about the centroidal z axis without twist the resultant of the Internal shear flow system would obviously due to symmetry of section about X centroidal axis lie on the X axis hence shear center for the given channel section is at point 0 in Fig. . The external load of 100 lb. would have to be located inches to the left of the centerline of the channel web If bending of the channel without twist is to occur. A14. 8 Shear Stresses for Unsymmetrical Beam Sections. In chapter A13 which dealt with bending stresses In beams three methods were presented for determining the bending stresses in beams with unsyrametrlcal beam sections. The bending stress equations for these three methods will be repeated here - Method 1. The Principal Axis Method. zp b Xp Xp IZp Method 2. The Neutral Axis Method. Ơ - --------------------------------- 10 Method 3. The Method using section properties about centroidal z and X axes. For brevity this method will be called the k method. Ơ - - ka Mz - kx M X - k Mjj. - kx Mj. z 11 where k - _lỵz . k_Tx IX z Ixz B -z íẳz a T I J2- I Xx 1Z ixz In referring back to the derivations of equations 5 6 and 7 the above equations 9 10 and 11 can be written In terms of beam external shears Instead of external bending moments as follows - Method 1. The Principal Axis Method. 7X- ap xp Qy - s Zp A - 2 Xp A------------------ 12 XZp Method 2. The Neutral Axis Method. vn _ . Qy - -- 2 Zp A------------------------------ 13 Method 3. The k Method. qy - ka 7X - ki v2 2 X A - k vz - kx vx 2 z A----------------- 14 EXAMPLE PROBLEM USING THE THREE DIFFERENT METHODS. Fig. shows a Zee Section subjected to a 10 000 lb. shear load acting through the shear center of the section and in the direction as shown. The problem will be to calculate the shear flow qy at two points on the beam section namely .
