Column Head Reinforcement
is the distance from the column face to the edge of the column head is the diameter of a circular column.
For a rectangular column with a rectangular head with overall dimensions l1, and l2 (li = lci + 2lm; l2 = lc2 + 21h2, li r l2), dcrit may be taken as the lesser of:
(2) For slabs with column heads where 1h > 1.5(d + hH (see Figure 4.23), the critical sections both within the head and in the slab should be checked.
(3) The provisions of 4.3.4.3 apply for checks within the column head with d taken as d^ (see Figure 4.23 for definition of d^).
(4) The distances from the centroid of the column to the critical sections in Figure 4.23 may be taken as: dcrit,ex = 1h + 1.5d + 0.5 lc (4.53) dcrit,in = 1.5 (d + hH + 0.5 lc (4.54)
(5) For column heads where 1.5 hH < 1h < 1.5(hH + d), the distance from the centroid of the column to the critical section may be taken as:
H"
4.3.4.5 Shear resistance
4.3.4.5.1 Slabs or foundations without punching shear reinforcement
(1) The shear resistance per unit length vRdi of nonprestressed slabs is given by:
where rRd is given in Table 4.8, Section 4.3.2.
Pjx and ply relate to the tension steel in x and y directions respectively. d = (dx + dy)/2
dx and dy are the effective depths of the slab at the points of intersection between the design failure surface and the longitudinal reinforcement, in the x and y directions respectively.
(2) For prestressed slabs, Equation (4.56) applies, with:
*cpo Npd/Ac design yield stress of the reinforcement fyd
Npd = prestressing force corresponding to the initial value without losses (equivalent to Pmo in 2.5.4 and 4.2.3). If the prestressing force is different in the prestressing directions, the average value is used. Npd should be calculated with Yp = 0.9.
4.3.4.5.2 Slabs containing punching shear reinforcement
(1) In slabs containing shear reinforcement the shear resistances are given by: vRd2 = 1161 vrd1 vRd3 = vRd1 + C Asw fyd sina/u
where C Asw fyd sina is the sum of the components of the design forces in the shear reinforcement in the direction of the applied force, a being the angle between the reinforcement and the plane of the slab.
For other types of shear reinforcement (e.g. shearheads), vM3 may be determined by test or taken from appropriate documents.
(2) Shear reinforcement should be provided within the critical area.
(3) Where necessary the punching shear resistance outside the shear reinforced area should be checked by considering further critical perimeters.
(4) Detailing requirements for punching shear reinforcement are given in 5.4.3.3. Minimum shear reinforcement should be provided in accordance with 5.4.3.3. The verification of Equation (5.16) can be done by taking into account the total amount of punching shear reinforcement — placed between the critical perimeter and the loaded area — as follows crit where:
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