High Performance Fiber Reinforced Cementitious Composites (HPFRCC) develop micro-cracks under bending load. This study clarifies durability against steel corrosion in HPFRCC. Specimens made of HPFRCC or normal mortar with cracks were cured in a chloride or CO2 environment and chloride ingress or carbonation progress was evaluated. The corrosion cell formation pattern and rate were also compared between HPFRCC and normal mortar, and their mechanism was discussed. The multiple cracks in HPFRCC were focused on in particular. It was found that chloride ingress and carbonation progress occur at many spots in HPFRCC, and that the advantage of HPFRCC against corrosion is due not only to the crack width but also the cracking pattern itself, which causes microcells instead of macrocells. From the above results, it was confirmed that the durability of HPFRCC against chloride or carbonation induced corrosion is higher than that of normal mortar.
Slurry infiltrated fiber concrete (SIFCON) have received considerable attention in recent years. The SIFCON is distinguished from the conventional steel fiber reinforced cementitious composite (FRCC) by its high volume ratio of fibers, far beyond that of typical steel FRCC. Although this material has already been used for important structures including power plants and military facilities, very little is known about its behavior under blast loading. We therefore have experimentally investigated the behavior of SIFCON under the contact blast loading for the first time. This paper is intended to report these blast test results, in which varying amounts of gelignite embedded in the specimens were set off. After the blast test, diameter of crater, diameter of inlet of charge hole, and bulge of top surface of SIFCON were measured from the pictures using a commercial stereophotogrammetry program ShapeMetrix3D, and compared them to that of the conventional high strength concrete. The comparison results show the much higher blast resistance of SIFCON over conventional high strength concrete. In addition, the coefficient of resistance of SIFCON is evaluated which helps us to design the SIFCON structure subject to blast loading
This study proposes a new methodology based on nonlinear required strengths for evaluating the seismic performance of low-rise reinforced concrete (RC) buildings composed of members controlled by both shear and flexure. The required strengths, which represent the relationships among the strength of members controlled by shear (Csu) and flexure (Cfy) as well as earthquake levels (α) in terms of ductility demand (μ), are equated using regression analysis to estimate α-levels applied to the structure corresponding to μ, Csu, and Cfy. The residual seismic performance (R, damage state) of RC buildings controlled by both shear and flexure is evaluated based on strength capacity in terms of ductility demand by applying the procedure outlined in the Japanese Standard for Damage Level Classification and the Japanese Standard for Seismic Evaluation. We propose a new methodology for performance-based seismic evaluation of low-rise RC buildings with dual lateral-load resisting systems on the basis of the relationships between the R-index and earthquake level evaluated in terms of the ductility ratio. We applied the proposed method to two existing low-rise RC buildings and compared the results to those of nonlinear dynamic analyses where each member was modeled with its flexure spring and shear spring serially connected. We also evaluated the seismic performance of eight actual buildings that suffered damage in the 1995 Hyogoken Nambu and the 1993 Nanseioki earthquakes to demonstrate the effectiveness of this proposed methodology and estimate the degree of damage. Furthermore, we applied the proposed method for seismic evaluation to ten low-rise RC buildings with seismic protection indices of ES = 0.6, which is the Japanese standard for the critical value required to prevent moderate or greater damage to structures under a rare earthquake with the ground motion acceleration level 0.23g like the 1968 Tokachi-oki EQ and 1978 Miyagiken-oki EQ and to prevent heavy damage under a very rare earthquake with the ground motion acceleration level much higher than 0.23g like 1995 Hyogoken-Nambu EQ. We also compared the relationship between the results of the proposed method and the seismic protection index. The proposed methodology reasonably predicted the earthquake damage sustained by actual buildings, and its results agreed closely with those from detailed nonlinear dynamic analyses and the second-level procedure in the Japanese standard based on ES = 0.6. The proposed seismic evaluation method was efficient; it provided a means to evaluate the seismic performance considering a specific level of desired structural performance for a specific level of earthquake demand. The new methodology presented in this study can thus be effectively used for performance-based seismic evaluation of low-rise RC buildings composed of members controlled by both shear and flexure.
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