Abstract: The invention provides a chassis for a truck trailer which can be manufactured for less cost, and can be lighter, for the same strength, as a conventional twin I-beam trailer as used in fifth wheel logging truck applications. The chassis of the invention has an elongated beam member having a generally horizontal top wall, a pair of laterally spaced apart side wall portions with upper margin portions which are inclined inwardly and upwardly to merge continuously with the top wall portion. Lower margin portions of the side wall portions have flanges which have inner edges spaced apart to accommodate service conduits, and other components. A plurality of transversely extending bunk means are spaced apart longitudinally along the beam member at respective stations. The inwards inclination of the upper margin portions reduces chances of a loading grapple fouling with edges of the beam member when loading and unloading logs from the trailer.