Section 27-560. Stage areas using scenery or scenic elements

Scenery battens
  and suspension systems shall be designed for a load of thirty pounds per
  linear  foot  of batten length. Loft block and head block beams shall be
  designed to support vertical and horizontal  loads  corresponding  to  a
  four  inch  spacing  of  battens  for  the entire depth of the gridiron.
  Direction and magnitude of total forces shall  be  determined  from  the
  geometry  of  the rigging system including load concentrations from spot
  line rigging. Locking rails shall be designed for a  uniform  uplift  of
  five  hundred psf with a one thousand pound concentration. Impact factor
  for batten design shall be seventy-five per cent and for loft  and  head
  block  beams  shall be twenty-five per cent. A plan drawn to a scale not
  less than one-quarter inch equals one foot shall  be  displayed  in  the
  stage  area  indicating  the  framing  plan  of the rigging loft and the
  design loads for  all  members  used  to  support  scenery  or  rigging.
  Gridirons   over  stages  shall  be  designed  to  support  a  uniformly
  distributed live load of fifty psf in  addition  to  the  rigging  loads
  indicated.