Thursday, May 15, 2014

The importance of Hydraulic Jump

I caught this video  from FB post..........



video


This video shows the importance of the  correctly design HYDRAULIC JUMP at the  spill.

I can remember the effort of my Hydraulic Professor who took great effort to teach us the phenomena during my undergraduate studies.

The hydraulic jump is designed to dissipate the energy of the water flow, so that it flows in safe speeds inthe downstream.





Wednesday, May 7, 2014

Cracks in Prestress concrete Beams


I came across this problem last year. Although the issue has been solved, still I think we can share our views on this.

The problem occurred on 19m long pre tensioned PSC beam.  The cracks, in the range of 0.2 mm – 0.5 mm,  were noticed on the top flanges of the 19 m beams and  near the two lifting positions of the each side ends of the beams as shown in the following figure.


cracks positions of the beam

closed view of the cracks

The crack positions, sizes and the propagation are almost identical in every beams at the site and I had my  uncertainties on the structural integrity of the defected beams.

The cracks have appeared on the places where maximum hogging moment occurs during the lifting of beams. Hence these are considered as flexural cracks ( Not shrinkage or early thermal cracks) and possibly owing to lifting of the beams before the concrete achieve its characteristic strength in Transfer Stage.  

I would highly welcome your opinion on what next to do?