With the widespread use of high strength deformed bars with larger diameters, a great interest in the mechanism of bond failures has been renewed. Bond failures of deformed bars are characterized by splitting due to the wedging action of transverse ribs. Recent researches indicate that bar cover and spacing are critical factors to determine the bond Strength and that transverse reinforcement is effective for improvement of bond resistance. The purpose of this paper is to describe the noticable results of recent researches on this subject, and to provide engineer with information necessary for avoiding splitting bond failures.

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This report presents a summary of results of the author's studies so far conducted in respect of large deflective damage to reinforced concrete floor slabs, a structural breakage setting associated with their peripheral cracking and sustained growth often developing in prolonged years to detrimental midpanel subsidence accompanied by perceptible vibration.
Based mainly on the facts obtained from field studies, this work is intended to clarify the actual conditions of those structures which undergo such type of damage and to find suitable measures preventive against it in their structural devices
To that effect, the investigation, mostly implemented in Hokkaido, on the existing r. c. slabs subjected to the damage as above, in the total number of 1122 slabs of 72 separate constructions, was systematically examined. As a result, some groups with frequently encountered damage patterns were obtained, accompanied by clear errors in each construction. Then these data are further analyzed and the result is reorganized by inferring virtually by way of induction supported by statical theorization, and a tenable limit of slab dimensions in restraint of detriments of large deflection. In effect, it is suggested that optimal slab dimensions are obtained when used as design criteria and that the maximum extreme fiber stress in a slab is kept within tensile strength of concrete subject to the net load.

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This report describes the results of experiments on the mix proportion of fiber reinforced concrete with about 6 percent air content. Discussing about influences of sand percentage, fiber content and water content on air content, slump and strength of concrete, the approximate required values of air entraining agent to get the required air content, and of sand ratio to get preferable concrete with designated fiber content, and of water content to get the required slump are found out.

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This is a report on concrete work of inclined roofs of a pyramidical museum building. The construction of the complicated roofs with large projecting inclined beams, inclined slabs, horizontal slabs and parapets were executed through various devices and repeated try-and-error. Methods of formwork supports and their installation, concrete mixing and methods of concrete placement are especially described in detail.

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[in Japanese]

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