glu lam beam modificationsuggestion and design calcs

huangyhg

glu lam beam modification/suggestion and design calcs
i am currently building a house and need to modify a glu lam beam.  i have a simple span of 16 feet over a garage opening.  the beam supports only the roof trusses/roof.  the support consists of 2 glu lam beams, each measuring 19 inches deep and about 5 inches wide.  i need to cut the bottom 5 to six inches out of the beam.
i am looking for advice and calculation software or tables  to make sure i can handle the loads.
suggestions?
cp
check out our whitepaper library.
  the butchered beams will have less than 1/3 of the original strength!  this loss can be made up in a variety of solutions.  add a post, replace with steel beams, repair with steel plate at the bottom of the glulams, etc.
i hear what you are saying, but it seams counter intuitive.  i would expect that the beam performance would be comparable to an equivalent lesser beam thickness with some reduction.  do you have a basis or technical paper that addresses cutting abeam?
thanks
cp
i think glulams are more complicated than you think.  if i am not mistaken, the wood layers at the top and bottom are a lot stronger than the middle layers. so cutting 5" out of 19" deep doesnt necessarily mean it has the capacity of 14" glulam.  i would use steel beam if i were you. or design with 14" gl instead of butchering a deeper member.  deeper   
if true glulam, the ply strength is matched to the stress.  they have stronger plies on the outer edges where the stresses are higher.
cutting the outer plies may significantly reduce the strength above just reducing the section modulus.
also modifying the beam may void any warranty. many fabricators specifically caution about modifying their products.
dik
hey guys thanks for the input.  the beams are already installed and the roof in.  the builder set the garage door opening at 7'6" and i would like to take it up to 8'.  so cutting would be the only option.
the beams appears to be well over sized.  i have two 5" by 19 beams, side by side, supporting a 16 span with roof trusses resting on top.
i also may be using the term glu lam incorrectly.  the beam is composed of a series of what appear to be 9 =/- 2x5s stacked horizontally and glued to create the beam section.  the beams were made by weyerhauser. is it correct to refer to this type of beam as a glue lam?  the exterior   
i am think through options here and could i not 1) bolt the beams together there by increasing the section modulus 2)place a steel plate at the cut base to increase/replace lost tensile capacity and there by increasing the section modulus?
  
that is a glulam.  i dont understand why someone would put gl in the wall.  why not just use lvl (cheaper and strong).  i always spec gl only if it is exposed (looks nice).  you are the engineer captain.  do what you think is necessary.
the gls were free so the price was just about perfect.  otherwise, the beam would have been steel. i am an engineer, but the geotech type.  structural design using timber and specifically gl is well outside my comfort zone.  
do you know anyone in the denver area, that by chance, would have gl experience?
cp
i know someone .  see my name?  
i figured.  where are you in denver?  i am out in east parker...