This paper describes experimental and analytical study of drying shrinkage crack behavior of steel chip reinforced polymer cement mortar (SCRPCM) and polymer cement mortar (PCM). (1) Drying shrinkage test is conducted with four restrained wall specimens of 2500 mm length and 150×300 mm cross section. The drying shrinkage strains, the number of cracks and the crack patterns of the specimens are observed. (2) (a) flexural creep test, (b) pull-out bond test and (c) bond creep test are carried out to evaluate the bond between the SCRPCM/PCM and the steel bar as well as creep characteristics. The shrinkage strains and creep strains of SCRPCM/PCM, and the bond stress-slip curve and bond creep of steel bars are modelled partially according to CEB-FIP Model Code. These models are incorporated with bond computation between the SCRPCM and the steel bar to predict effective strain. The bond stress distribution is computed using analytical solutions of the differential equation of the bond problem, and crack numbers are predicted. (3) 2D finite element analyses are conducted for the four restrained wall specimens of SCRPCM/PCM subjected to drying shrinkage to practically simulate the crack behaviors. The analyzed crack patterns, number of cracks and crack widths are compared with the result of drying shrinkage test.
Seismic pounding of a 14-story reinforced concrete building, Nuevo León, damaged in the 1985 Mexico Earthquake is investigated by means of dynamic finite element analyses and cyclic loading tests of columns specimens. The building consisted of three adjacent units connected with 100-mm wide expansion joints. It was thought that the poundings caused impact lateral forces and frictions that resulted in serious structural damage. This study attempts quantification of the impact lateral load by the following four steps.
(1) Two kinds of seismic response finite element analyses of a single unit of the building are conducted with /without simplified contact modeling with joint elements to approximately estimate the overall structural behavior.
(2) Cyclic load test of two column specimens that represent a column of the building. One of the specimens is a simple column while the other consists of four pounding units, to which the column contacts during loading. Comparison of the two specimens indicates that the contact induces additional lateral shear force to the column.
(3) Repeated cyclic responses of the two specimens are computed by static finite element analyses. The contact and friction behaviors are classified into normal and shear components to develop a constitutive model to be implemented into the two-node joint element.
(4) A finite element model of two partial building units connected with the two-node joint elements is subjected to seismic response analysis. The analysis result indicates that the pounding causes an impact load equivalent to 0.9% of the total weight of a building unit.
Ultra high performance concrete (UHPC) with steel fibers not only possesses the higher compressive strength can be up to above 100MPa, but also has better tensile strength and ultimate strain because of the addition of steel fibers compared with ordinary concrete. However, the permeability behavior of UHPC is frequently ignored in the durability dsign or repair, especially for that with a mass of cracks after suffering short-lived vibration, shock or explosion. This paper is developed to investigate the permeability behavior of UHPC after suffering tensile and compressive loadings, and the water as well as chloride permeability are determined. The results show applied tensile and compressive loadings increase the water and chloride permeability of UHPC. Particularly for the UHPC after suffering high loading damage, the increase of permeability becomes more obvious. Self-healing treatment is also applied to the UHPC with loading damage, and the permeability resistance of UHPC is improved by the treatment of self-healing, which provides an effective method to repair the UHPC with loading damage. In addition, the relation between permeability behavior and applied loads or cracks development are established in this paper, which can be used to evaluate the permeability behavior of UHPC suffered loading damage.
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