逆打工法における柱打継ぎ部の力学性状に関する実験的研究

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The top down construction method presents several specific technical problems, such as c the joint treatment of top down concreting, (2) the influence of heaving, due to excavation, on the concrete structure, and (3) the temporary supporting method of the weight of upper floors during underground work; this weight must be supported by steel columns in cast-in-place concrete piles. In particular, the construction joint of concrete has been a matter of concern since the introduction of the method. Joints created by top down concreting produce a layer of laitance. Also setting of the lower concrete causes detachment of the joints, weakening the structure and reducing watertightness. In Japan three types of joint treatment method have been adopted: (1) Direct method (D) I Concrete of normal mixture or that containing a non-bleeding or expansive additive is used for the lower part. (2) Injection method (I) : Cement paste or epoxy resin is injected into the clearance produced by the setting of the concrete. (3) Filling method (F) : Non-shrinking mortar is used to fill the clearance (about 300 mm) between upper and lower concrete. In this report the mechanical properties of three types of joint treatment and the efficiency of the shape of construction joints on the axial strength of columns are described. The results obtained in this study are summarized as follows. 1) From the viewpoint of axial strength, the angle of construction joints must be under 45°. 2) Under complex stress conditions, the strength of the cement paste injection method (3mm clearance) is equal to the strength of the filling method and the epoxy resin injection method. 3) If the clearance is larger than 3〜5 mm, the strength of the cement paste injection method is smaller.
社団法人日本建築学会の論文
1988-11-30

逆打工法における柱打継ぎ部の力学性状に関する実験的研究

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