Post-tensioned Steel Research Articles

Prestressing force increment of two-span steel girder

The economic advantages and the advanced technology of prestressed steel bridges has opened new opportunities in bridge engineering. The girder bridges prestressed by cables have been recognized as a technique for the design of new bridges as well as the rehabilitation and increasing the load-bearing capacity of the existing bridges. However, the prestressing of steel girders introduces new problems which require special attention and studies. The objective of this paper is to analyze the influence of the prestressing force increment and the induced negative bending moment in two-span steel girder bridges prestressed by external tendons (cables of high strength steel). The proposed analysis is based on the flexibility method. The deformations are calculated by the virtual work method. The analysis is limited to elastic stage only. The equations for calculating the prestressing force increment and the bending moment at the middle support are derived. Numerical examples are solved and the results are compared with those of similar non-prestressed girders. The influence lines are prepared and evaluated for a continuous girder of two equal spans of 60 m in length each. Key words: bridges, post-tensioned steel, force increment, analysis, influence line.

A non-linear analysis of the rotational stiffness of a nuclear steam generator foundation

A non-linear analysis of the moment-rotation relationships of a circular foundation for equipment of a nuclear steam supply system is presented. Equations are derived and numerical results given for 1) normal mild steel anchor bolts and circular base plate arrangement and 2) post-tensioned high-strength steel anchor bolts and circular base plate arrangement. An axisymmetric finite element computer program was applied for finding the stiffness of concrete in compression. The inelastic behavior of steel bolts is accounted for by an iterative procedure.