Question

What is problem in traditional marine piling system of steel tubular pile with concrete infill and what are key possible remedial measures?

Answer

In designing of marine piles of steel tubular piles with concrete infill, loads from pier deck are occupied up by steel tubular piles before occurrence of corrosion of steel piles above seabed. It is assumed that steel piles above seabed level will all be corroded after a sure year. Load transfer mechanism after complete corrosion of steel pile over seabed is as follows-

Loads from pier deck are taken up by concrete infill above seabed level. Below seabed level, loads would be transferred to steel piles through frictional forces between concrete infill and steel casings.

Yet, substantial radial shrinkage and contraction arises after concreting of concrete infill and this would hinder load transfer from the concrete infill to steel piles because bond might be ruptured by radial shrinkage. It is in hesitation if frictional forces be able to be correctly developed in this situation. To solve this problem, shear keys can be installed at normal spacing inside steel piles to ensure their rigid connection with concrete infill. Alternatively, expanding agents could be adopted in concrete mixes to make sure that there is no shrinkage after concreting process.