Akihiko FUNATO

Mechanism of Reduction of Crack Width Appeared in RC Members with Fiber Reinforcing Materials

SupervisorFTakumi SHIMOMURA

In this study, RC members (that have constant crack spacing) with fiber reinforcing materials are loaded in axial tension. Average steel strain, and Average concrete strain are measured to discuss the effect of fiber reinforcing materials on crack width.

It's observed that RC member with aramid fiber mesh (FMRC Fiber Mesh Reinforced Concrete) reduced crack width, while RC member with short aramid fiber (SFRC, Short Fiber Reinforced Concrete) didn't reduce crack width in axial tension test. Average steel strain of FMRC member and that of SFRC member are same with referential test specimen's under the constant steel stress. From this test result, it can be said that effect of reduction in crack width didn't be caused by reduction of steel strain under the constant steel stress. Average concrete strain of FMRC and SFRC were larger than referential specimen.Therefore, Mechanism of reduction in crack width in FMRC would be caused by increasing of concrete strain that arises from minute cracks, because existence of minute cracks are observed from concrete strain profile.

According to deformational compatibility condition, under the condition that both crack spacing and average steel strain were constant, crack width is inversely related to concrete strain. If so, SFRC should have small crack width than reference, but test result was different. After investigation regarding the relationship between average steel strain and average member strain, it's revealed that there are some amount of slip at the end parts in referential member. while there is no slip in SFRC member. Therefore, in case of SFRC members, the effect of concrete strain is canceled out by the increasing of average member strain. This mechanism would lead to non-effectiveness of crack width in SFRC members.