Steel Buildings in Europe

Part 10: Technical Software Specification for Composite Beams 10 - 32 When the beam is unpropped, this deflection is calculated with no contribution of the concrete slab – the second moment of area of the steel profile is then considered: I eq = I y . Deflection under a distributed load The deflection w at the abscissa x , under a uniformly distributed load denoted Q , is calculated by: w ( x ) =                       4 3 eq 3 2 24 L x L x L x EI QL Deflection under a point load The deflection w of a section located at the abscissa x , under a point load denoted F located at x F , is calculated by (see Figure 4.1): w ( x ) =       L L x x L x x EI L F F 2 2 F 2 eq 6     if x < x f w ( x ) =       F 2 F 2 2 eq 6 L L x x L x x EI L F     if x > x f 6.5.4 Vibrations The natural frequency (in Hz) of the composite beam can be estimated from the following equations: w f 18,07  for a uniformly distributed load w f 15,81  for a concentrated load at mid span where: w is the deflection in millimetres calculated with the short term modular ratio for a combination of actions including only a percentage of the imposed loads. Depending on the National Annex, the combination can be either the characteristic or the frequent one.