Builders had a lot to chew on in the Construction Dive news feed this week, but worries about a multifamily bubble and some insights about traditional building materials finding new life in green projects earned the most attention.

If you need to catch up on what's been going on over the last few days, we recommend checking these five items that generated the week's most attention. Have a look, and go into the week a little more informed:

• $1M earthquake simulation study may lead to changes in building code: Scientists and engineers are studying the effects of seismic activity on steel structures.
• Guest Post: Why One WTC is the world's most expensive skyscraper: Here's what went into the Freedom Tower’s security apparatus, and why New York City spared no expense.
• Some commercial investors fear multifamily is ripe for a bubble: This survey says commercial real estate executives worry that apartments may be getting inflated.
• Green building breathes new life into old materials: A new report sees straw and bamboo making a comeback in the next decade.
• A tale from the rails: How 'buy American' killed a project: A proposal to construct a high-speed rail link between Las Vegas and Los Angeles lost any chance of federal funding because of a rule saying it had to buy what doesn't exist.

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