在上讲中,我们介绍了矩形、T形和工形截面的受弯构件斜截面承载力的计算方法,现在需要补充一点:在受弯构件中还有这样一类构件,它的底部受拉边沿纵向不是水平的,而是倾斜的。因为一般简支梁(受弯构件)跨中弯矩大,需要有较大的梁高;支座弯矩为零,梁高可以适当减小。为了经济合理,人们常将梁的截面不做成等高的,而做成不等高的。这就是我们通常称之为变截面梁。变截面简支梁就是梁跨中截面高度大,支座截面高度小,梁的截面高度沿纵向是变化的,跨中最大,向着支座逐渐减少。一般梁的上部保持水平,只是它的下部 In the last lecture, we introduced the calculation method of the oblique section bearing capacity of the bending members of rectangular, T-shaped and I-shaped sections. Now we need to add one point: In the bending members there is such a kind of components, the bottom of which is pulled. The longitudinal direction of the edge is not horizontal but inclined. Because the general moment beam (bending member) has a large bending moment in mid-span, a larger beam height is required; the bending moment of the bearing is zero, and the beam height can be appropriately reduced. In order to be economically reasonable, people often make the cross section of the beam not equal, but they are not of equal height. This is what we commonly call variable cross-section beams. The variable cross-section simply supported beam is a beam with a large mid-section height and a small cross-section height of the bearing. The cross-section height of the beam is changed along the longitudinal direction, and the cross-section is the largest and gradually decreases toward the bearing. The upper part of the general beam remains horizontal except for its lower part