Clearly Weathered

Several coats of marine varnish?

I always use this stuff, use two coats, allowing to dry in between each coat, wait for 1 month repeat process, and then do it again...at least six coats...then annually one coat...

http://www.thompsonswaterseal.com/waterproofing-products/waterproofers/

Both prior suggestions are good.

No matter what finish you choose, it's the regular re-application of the finish that will save the wood.

There's no paint-it-and-forget-it solution.

BJs' Paint is Tumwater's Home of Superdeck, Flood, Gaco ...

You may want to check out the official website for Valspar, as they produce many types of clear exterior wood sealers, from latex to acrylic-based. You can purchase their products at Lowe's Home Centers....I'm not so sure about Home Depot carrying that line.

If the Glu-lams are discolored due to environmental exposure make sure you do a thorough surface preparation such as high pressure water washing, bleaching w/ TSP & water, and light sanding if necessary. A word of warning about pressure washing: use a low pressure setting and wide application nozzle, otherwise you can damage the wood surface by "gouging". So try it first in an inconspicuous location first that no one will notice in case you damage the wood. Also, while you're at it, inspect the wood for insect infestation, delamination of the wood at the glue joints, mold of any type, and wet-rot as well as dry-rot.

How old are these glu-lam beams (and columns?)? What type of exposure are we talking about here? Photos of them available for posting?

I'm assuming that these glu-lam beams are exterior and exposed to the weather