Dimensional Limits for Beams
ICONS
A c = Gross cross-section area of the column
N d = Axial force calculated under the combined effect of vertical loads and earthquake loads multiplied by load factors
f ck = Characteristic cylinder compressive strength of concrete
7.4.1. Cross Section Conditions
7.4.1.1 - Conditions for the cross-sectional dimensions of beams forming a frame with columns or connected to walls in their own planes are given in (a) to (d) below :
(a) Beam body width shall be at least 250 mm. The beam body width shall not exceed the sum of the height of the beam and the perpendicular width of the column or curtain to the beam.
(b) Beam height shall not be less than 3 times the slab thickness and 300 mm. Elements that do not fulfill this requirement will be modeled together with the floor elements in the analysis, will be equipped like a beam, but will not be considered as frame beam. Also, beam height shall not be more than 3.5 times beam body width.
(c) When the beam height is more than 1/4 of the free span, a longitudinal web reinforcement shall be placed on both sides of the beam body along the beam height. The total longitudinal web reinforcement area shall not be less than 30% of the largest of the total of upper and lower longitudinal reinforcement areas in right or left support sections. The core reinforcement diameter shall not be less than 12 mm and the spacing shall not be more than 300 mm. Horizontal body crossties will be placed at intervals not exceeding 600 mm along the beam height and 400 mm along the beam axis. In like manner to the engagement of the longitudinal reinforcement of the body to engage the reinforcement 7.4.3.1 'in (b) and (c) paragraph apply.
(d) The limitations specified in (a) , (b) and (c) above regarding the beam width and height, except for reinforced concrete beams hinged to columns, tie beams of tie beams (hollow) walls and column beam nodes to frame beams. It is not compulsory for stuck secondary beams
7.4.1.2 - For structural system elements to be dimensioned and equipped as a beam, the design axial pressure force must meet the condition N d ≤ 0.10 A c f ck . Otherwise, these elements will be dimensioned and equipped as columns according to 7.3 .
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