"Negative influences of HSC and their solutions in reinforced concrete structures"

  For the study of shear behavior, we bring it into focus to study whether the change of material properties due to higher strength has an adverse effect on the shear behavior of skeleton members.  The study constitutes of a member test, an analytical study on mechanical models considering effect of aggregate interlocking, and comparison of various expectations with test result in the literature.  We can explain what happens on the shear of high strength concrete beams  by test and analytical study.  And we can judge which specification and proposal of shear strength expectation is valid for high strength concrete beams for design by the comparison to test results in the literature.  As a result, it can be concluded that the effect of high strength on shear strength is not direct, and we can apply some of the specifications and proposals also for the high strength concrete beams.   However, our design specifications of shear, for both shear reinforced beams and not , show poor agreement with test results.  We proposed the modified design formula, which fits better with test results while it keeps basic forms of our specifications.  One of the important adverse effect of high strength concrete on shear is that of minimum shear reinforcement.  We show that our design provisions of minimum reinforcement on shear is unsafe for higher strength concrete beams and lower depth beams.  It is recommended to use ACI or MC90 provisions which consider strength effects on minimum shear reinforcement.  

"Development of Biaxial Tension-Compression Field Theory for Establishing a Unified Design Approach in Reinforced Concrete Members subjected In-plane Forces"