EXPERIMENTAL STUDY ON IN-PLANE SHEAR BEHAVIOR OF AAC BLOCK MASONRY WALLS WITHOUT OPENINGS (2018)

An Autoclaved aerated concrete (AAC) is an efficient structural material because its light weight reduces seismic inertia forces under earthquake excitations and improves thermal insulation quality for comfortable environments. Since an AAC panel structure can't be designed in Japan, we propose a reinforced and fully grouted AAC block masonry structure. Few experimental studies of bearing wall constructed of non-reinforced AAC blocks are available. In this study, in-plane tests of bearing walls constructed of reinforced AAC blocks with internal bars and the non-reinforced AAC blocks were carried out and the effect of the internal bars is confirmed. Furthermore, the strength and deformation calculated referring to previous studies in concrete block masonry structures were compared with test results. Three types of AAC blocks (ALC50, ALC37 and ALC42) which have different specific gravity and the internal bars or not constitutes the masonry wall. ALC50 and ALC37 have the internal bars and ALC42 doesn't have them. Each AAC block has grooves and vertical holes. Vertical reinforcements are cast in the holes and horizontal re-bars are cast in the grooves. After the blocks are pasted with sealant and built, the grooves and holes were fully grouted in order to achieve a good bonding behavior between the reinforcements and the blocks. Each mechanical property of the materials is shown in Table 2. Compression and shear wallette tests were carried out and those mechanical properties and those failure behaviors were obtained. The test specimens with the internal bars avoided the sharp post-peak drop and enhanced displacement capacity. Therefore, it is considered that the internal bars provide confinement under the compressive force and shear reinforcing effect under the shear force. In-plane tests of masonry bearing walls without openings were carried out. A suite of five specimens which have different block type and wall length (aspect ratio of 0.7 to 3) was tested by using a test setup of cantilever system. In the test results, a bed joint separation, a flexural crack, a shear crack and yielding of vertical bar were confirmed and integrated wall behaviors were observed until peak load. Flexural failure mode or shear failure mode after yielding was observed. The shear failure mode after yielding was observed in the specimen of few horizontal reinforcing bars or low aspect ratio or built with the non-reinforced blocks. Based on the mechanical properties obtained from compression and shear wallette tests, strength and deformation were calculated referring to previous studies in masonry structures. The flexural strength and the flexural deformation were calculated with the equation of simple bending theory. The shear strength was calculated with equation of concrete block masonry structures and the shear deformation was calculated with equation of theory of elasticity. The calculation results of the strength are almost good agreement with the test results. The calculation results of the deformation are a little lower than the test results because an effect of shear crack for shear deformation was not considered In the case of structural design for this AAC masonry structure, we propose to take into more consideration for safety because of a limited number of experimental tests in this study.