UPDATE 1-LB Foster to buy Portec for $112 million

* LB Foster offers $11.71 a share for Portec

* Offer represents a premium of 4 percent

Feb 17 (Reuters) - L. B. Foster Co (FSTR.O) said it would acquire Portec Rail Products Inc PRPX.O for about $112 million to expand its rail products business.

LB Foster said it will make a cash tender offer to acquire Portec's shares at $11.71 per share, a premium of 4 percent to the stock's Tuesday closing price.

Pittsburgh, Pennsylvania-based LB Foster makes products for the rail, construction, energy, utility and recreation markets.

Portec makes a wide range of rail products including anchors, spikes and friction-management products.

Shares of Portec were trading at $11.70 before the bell. They closed at $11.23 Tuesday on Nasdaq. LB Foster shares closed at $26.55. (Reporting by A.Ananthalakshmi in Bangalore; Editing by Vinu Pilakkott)