An investigation of end-anchorage and performance of SR-4 strain gages on a prestressed concrete beam

In recent years there has been brought to the attention of engineers and architects a new medium of construction---prestressed concrete. Reinforced concrete has long been recognized as a satisfactory material for use in the construction of buildings, bridges, highways, tanks and other structures. However, most concrete designers will concede that this material has many drawbacks. For instance, in a simple beam of rectangular cross-section, roughly only one half or the concrete is relied on to resist compressive forces. The tensile strength of the concrete is considered to be zero, and steel bars or rods must be inserted to carry the tensile stresses. This assumption necessarily increases the dead loads which must be considered in design. Prestressed concrete refers to members in which the concrete is subjected to stress before it receives any live loads. This stress ls usually in the form of a compressive force which acts on the whole cross-sectional area of the member. In this way the entire area of the member can be used to resist the applied loads. As in any new field of endeavor, many problems are encountered which must be investigated. In this field of prestressed concrete probably the largest stumbling block is the method of anchoring the high tensile strength wires which are used to induce the compressive stresses in the concrete. It is the purpose of this paper to investigate one method of end-anchorage and also to investigate the performance of SR-4 strain gages applied to both the prestressing wires and the concrete --Introduction, pages 1-2