Deformation of the sandwich-structured immersed tunnel element during concrete placing works while afloat is smaller than that of conventional “steel shell tunnels” and it more easily controllable because of the following reasons;
(1) The stiffness of the steel shell body is large even before the concrete is placed because of the double steel hull.
(2) Concrete placing works can be programmed chamber by chamber (about 10m
3 each) and thus the order of concrete casting of chambers can be scheduled as convenient.
A temperature change model was set forth for each member in tunnel element section, deformation during production works was estimated based on beam model on elastic foundation subjected to bending moments caused by self weight and temperature difference. This paper shows the comparison of history of relative deflection with simulation results in actual production works, series studies using above model and points of concern for concrete placing works.
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