Discussion on Papers 10 and 11

Paper 10

MR H. LIGTERINGEN

It should be emphasized that progress has been made in the area of concrete strength since Breakwaters f83. At that time the conclusions drawn from investigations of damaged breakwaters were as follows:

(a) stresses due to settlement and rocking were neglected or underestimated

(b) temperature stresses during curing may introduce microcracks

(c) the effective tensile strength is reduced by stresses due to curing shrinkage and settlement

(d) breakage of units leads to progressive damage of the armour layer.

Various research projects have been carried out to quantify these effects and are mentioned in the paper. In our opinion, in parallel with this ongoing research attention should be given to design procedures and guide-lines, in accordance with the requirements of the designer and the contractor. The development of such guide-lines may even help to structure research effectively.