Yoshitaka Nakagawa

STUDY ON MEASURES OF REDUCTION OF CONSTRUCTION INJURIES AND PARTNERING

The purpose of this paper is to study how to reduce construction injuries in Japan from the view point of partnering. First the author showed UK had better record compared to Japan by comparison of construction fatal injuries. In order to find out the cause, the author investigated the history of the regulations and measures for safety & health and regenerating construction movement in UK. From the study, the author picked up the risk assessment, certification scheme of capability for safety & health of workers in construction industry and the duty of construction designing engineers for safety & health. Then the author compared two countries about these thee points. From the study, the author showed there were great difference about partnering by supply-chain management and penalty due to breach the regulation. Finally the author suggests measures in order to reduce the construction injuries.

HISTORY OF ROCK EXCAVATION FOR BRIDGE FOUNDATION USING LARGE SCALE GRAB DREDGER

For the foundation of the large bridges connecting Honshu and Shikoku, excavation for the 2P and 3P piers of the Akashi Kaikyo Bridge, following similar work on the Seto Ohashi Bridge, were carried out using a large scale grab dredger. High accuracy was achieved, leading to success of the laying down caisson method.Large scale grab dredger have demonstrated their ability to dredge conventional navigation channels, particularly in excavating bedrock for the navigation channel through the Kanmon Strait. Consequently, the method was adopted for the underwater bedrock excavation of bridge piers for the Kurono Seto Bridge, the Seto Ohashi Bridge and the Akashi Kaikyo Bridge.This report describes the transition of grab dredger and the bedrock excavation of bridge foundations.

THE STUDY OF UNTIWASHOUT UNDERWATER CONCRETE FOR LARGE UNDERWATER STRUCTURES

Antiwashout underwater concrete is recently used due to the demand for speedy marine construction work of large structures.Antiwashout underwater concrete was also used for the construction of foundation for the main towers of the Akashi Kaikyo Bridge and its excellent properties have been verified. The antiwashout underwater concrete, for large-scale pouring, must retain its consistency for long hours, have low heat of hydration and stable placing properties.This study clarifies the effect of aggregate, sand, cement, and admixture on the flowability and setting time of concrete, and a better mixing method was developed to improve the quality of the antiwashout underwater concrete.