Studies of Box Beams for Railway Bridges

Abstract

It is no longer necessary to preface a paper on prestressed concrete by describing what it is or how it is used. This is now common knowledge among bridge engineers and certainly railroad bridge engineers are no exception. Now that this is accepted as a basic material the question is—How can it be used most effectively? This paper will describe the concepts behind the acceptance of box beams as a standard railway bridge element, research on single box beams and the use of double box beams in a concrete trestle. Many concrete trestles that are built now are a replacement of an existing timber trestle. This does not imply that all timber trestles are being replaced with concrete. The timber trestle is still a convenient and economical method of construction on the railroads and I am sure will continue to be; however, the prestressed concrete trestle by virtue of the increasing number of installations may be more economical in certain locations. The timber trestle is commonly built with pile bents 14 ft. on center. This varies on different railroads— some may be 12 ft. 6 in, and others