We have studied the effect of a post-weld heat treatment on plasma arc welds on Zircaloy
4 plates. The samples consist of two 100 mm long, 50 mm wide, and 6.25 mm thick plates, welded
along the rolling (longitudinal) direction. The heat-treatment consisted of a steady increase in
temperature from room temperature to 450oC over a period of 4.5 hours; followed by cooling with
an equivalent cooling rate. Residual strains and stresses along the longitudinal, transverse and
normal directions on an as-welded and a heat-treated specimen were measured by neutron
diffraction on the ENGIN-X beamline at the Isis Facility, Rutherford Laboratory, UK. Peak tensile
stresses of (105±25) MPa were found in the as-welded specimen, which were reduced to (70±20)
MPa after the heat-treatment. Thermal compressive stresses of (-80±20) MPa were found along the
normal direction, which were not affected by the heat treatment. The use of a full-pattern Rietveld
refinement for the determination of bulk strains in Zircaloy specimens is also discussed.
The Carrera Novena viaduct in Bucaramanga is situated over a wooded area of great environmental importance which must be respected. The proposed viaduct with a principal span of 292.4m and two compensation spans 129.2m long. The maximum height over the ravine is 75m and the piers of the viaduct have heights of 52m and 72m; for this reason singles piers have been used, over which the towers have been built which stay the deck in its axis. It is 30m wide because 6 lanes of traffic and 2m wide pedestrian walkways were planned. The structure of the deck is formed of a singlecell box girder with a trapezoidal section and a depth of 2.8m. This girder is extended laterally by slabs. Its width creates significant bending moments which are resisted by interior transverse triangulations and exterior struts every 3.4m. It is situated in a zone of high seismic activity and for that reason a structure has been adopted which is encastred in the piers and free in the abutments. It was constructed using successive compensated cantilevers, and concreted in situ.
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