The author explained 1) the fact that the behaviours of concrete member, especially the load and deflection relationships are closely connected with the degree of applied pre-stressing force and 2) the various classes of the prestressed concrete in order to arrive at a continous gradation of structural concrete according to the degree of prestress from conventional reinforced concrete to fully prestressed concrete. The adaptability of each class to a specific structure is also explained. 3) Many research results on the characteristics of the class III prestressed concrete, such as the estimation of crack width, the effects of sustained or repeated loading on the crack width and also the effects of constraining force of the added reinforcements on the stress losses, were presented. 4) The author proposed an approximate method to find the loss of prestress due to the deffered deformation of concrete in the class X prestressed concrete and also a calculation method to give the stresses of compressed concrete, additional reinforcements and prestressing ten-dons in order to verify the limit state for crack width.

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Very severe problems are generally observed in the construction of cast in place prestressed concrete viaducts in the urban area.
Large saving of manpower and construction period was achieved allowing free trafic underneath in Takashimadaira Viaduct of Metropolitan Expressway route No. 5, using SSM movable scaffold carrier.
Results of Takashimadaira Viaduct construction were as successful as planned, minimizing construction period and manpower to 1/3 and 1/2 respectively.
This highly mechanized movable scaffold carrier also enables works in the same condition as in shops, bringing about superb quality and procedure control decreasing skilled labour.

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During the construction work of reinforced concrete structure, lots of joints are needed, involving construction joints, where the reinforcing bar extended from the concrete surface are exposed to corrosion and sometimes the bar might be corroded seriously. Therefore, before placing the next concrete, it is often obliged to take off the rust of the surface of the bar.
The authors tried to coat the exposed surface of the bar by cement paste and studied how it prevented the steel corrosion, how it affected on the bonding performance and the cracking behavior etc.
As the results of the study, they made clear that the method can be used practically and is very effective against steel corrosion.

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