100 200 300 "0 100 200 300

Figure 6.14. Shear resistance of beams with tapered cross-section (Leung, Chew and Regan, 1976)

In a more recent publication (Regan, 2000) the author opts for a definition of bw = 2/3 bmin + 1/3 bmax, but admits at the same time that the available evidence is rather scarce. A possible compromise could be to define bw as the average width of the part of the cross-section in tension, with a maximum of 1,25 of the minimum width.

The equations in prEN 1991-1-1:2001 contain as well a term 0,15 Ocp regarding the influence of an axial force on the shear capacity, for instance by prestressing. Basically the influence of prestressing can be taken into account as proposed by Hedman & Losberg (1978). It was argued that, with regard to the behaviour in shear, a prestressed beam can be regarded as a reinforced beam after the decompression moment has been reached. On the basis of this argument the shear resistance was formulated as VRd,c = Vc + Vp where Vc is the shear resistance of a similar non-prestressed beam and Vp is the contribution of the prestressing force to the shear capacity, which can be formulated as Vp = M0/a, where M0 is the decompression moment and a is the distance from the load to the support, Fig. 6.15.

0 0

Post a comment