This report describes repair methods applied to the bridge piers (Nos. P7&P8) damaged due to chloride induced corrosion together with seismic strengthening applied in 2001-2002,It is required that economical concrete mixes and construction methods,which are applicable to the concrete structures damaged due to chloride induced corrosion under any climatic environmentwill be developed. (selection of section recovery material,deal with change of concrete,) Key Words chioride induced corrosion, bridge pier, investigation, section recovery, Corrosion of redar,polymer cememt concrete

Naha immersed tunnel will cross under the port entrance of the Naha wharf, Okinawa, where large liner ships are in service. Fluid power caused by the large vessel was expected to influence strongly against the stability of the tunnel element during construction. In this report, the stability of the element is investigated through threedimensional numerical simulation, in which speed of the large vessel is assumed to be constant. It is confirmed from the simulation that a large up-lift force is generated by the large vessel when it passes above the element, and that increase of navigation speed reduces the stability of the element against sliding.

Two routes of north Yamatoguchi and southern Touguchi are fixed in the Naha harbor. However, aYamatoguchi route has narrow Entry-into-port part to the weather and billow conditions, and is difficult to navigate-etc.-since there is a problem on use, most of large vessels use Touguchi. On the other hand, it is expected by the deployment to the north Urasoe head area that the importance of a Yamatoguchi route will increase increasingly from now on. Then, it is necessary to regard a Yamatoguchi route as the main route of the Naha harbor, and to fixas a route which a large vessel tends to use. This examination reports what carried out the navigation simulation in order to verify the form of a route, and the safety of the navigation about arrangement of a breakwater, when a vessel uses a Yamatoguchi route.