Point Load / Concentrated Load

Point load (also called concentrated load) is a load applied at a single specific point on a structural member, expressed in kN or N. Distinguished from uniformly distributed load (UDL, kN/m), point loads represent realistic site conditions where loads are not idealised as spread — wheel loads from vehicles, equipment legs, beam reactions on columns, secondary beam reactions on primary beams, and stored equipment on slabs. IS 875 Part 1 (dead load) and Part 2 (imposed/live load) tabulate concentrated loads alongside UDL values for various applications.

For a simply-supported beam of span L carrying a point load P at distance a from the left support: maximum bending moment M = P×a×(L−a)/L (at the load point, when a < L/2 — moment is largest under the load). For P at midspan (a = L/2): M_max = PL/4 = 0.25 PL. Compare with UDL of total magnitude w × L: M_max = wL²/8 = 0.125 wL × L = 0.125 (total load) × L. So a point load at midspan produces 2× the moment of an equivalent total UDL — point loads are more severe than UDL of the same magnitude.

Design considerations: (1) for slabs, point loads require local punching shear check at d/2 from the load point per IS 456 Cl. 31.6; for thin slabs, a thin-slab finite-element check is needed. (2) for beams, the point load at any location can be equally critical — pattern loading with concentrated load placed to maximise positive or negative moments. (3) IS 875 Part 2 specifies concentrated loads alongside UDL — for example, a residential floor at 2 kN/m² UDL has alongside a 2.5 kN concentrated load applied at the most-adverse location (usually 1.0 m from a support); the design must satisfy both. (4) IS 875 Cl. 3.4 specifies that for slabs subject to wheel loads or heavy point loads, the structural designer must explicitly compute punching shear capacity around the load patch — common Indian over-loading mistakes include placing furniture / equipment on slabs designed only for UDL.