Shear Performance of FRCC Beam-Column Joints Using Various Polymer Fibers

Brittle shear failure should be avoided in beam-column joint of a reinforced concrete(RC)frame during the earthquake.Fiber-reinforced cementitious composite(FRCC)which presents a remarkable deformability especially under tensile and bending load with a large energy absorption capacity is expected to be used in the crucial part of a RC frame.With the development of polymer material,various synthetic fibers have become the best selection to improve concrete capacity and failure resistance without the corrosion of fibers.The objective of this study is to investigate the influence of fiber bridging effect on the shear capacity of FRCC beam-column joint.The main parameter of the test in the present study is the fiber types:aramid,polypropylene(PP)and polyvinyl alcohol(PVA)fiber.To evaluate shear capacity quantitatively,a new calculation method using FRCC tensile characteristics confirmed by the uniaxial tension test is newly proposed.The difference of below 7%between calculated value and experimental value demonstrates that the calculation method is feasible.

Modeling of Bridging Law for PVA Fiber-Reinforced Cementitious Composite Considering Fiber Orientation

The authors have proposed the calculation method of bridging law,that is expressed by tensile stress–crack width relationship,considering the influence of fiber orientation in FRCC(fiber-reinforced cementitious composite).The objective of this study is to propose a new tri-linear model that expresses the bridging law considering fiber orientation.The parameters that give the characteristic points of the tri-linear model are proposed as functions of orientation intensity.The bending test,in which the specimens are fabricated by three different casting methods,is conducted to verify the adaptability of the proposed model.The results of section analysis using the proposed model can present the difference of bending strength due to the fiber orientation.

Tensile Characteristics Evaluation of Corroded Reinforcing Bars Extracted from Actual Structures

The analysis used simple finite elements is performed to simulate the tensile behavior of corroded reinforcing bars extracted from three actual concrete structures. The cross-sectional area of the elements is set to have the actual distribution measured by 3D laser scanner system. The variable factor in the analysis is the length of the elements. The analysis results show that the length of the elements has a major influence on the deformation capacity after yielding. The calculated stress-strain curves, obtained using the elements with a length that is 2 times the bar diameter, are in good agreement with the tensile test results. The calculated stress-strain curves are modeled using a bi-linear model to facilitate the FEA （finite element analysis） of an overall concrete structure. From the analysis results, both the tensile and yield strengths decrease in proportion to the reduction of the minimum cross-sectional area of corroded bars. The ultimate strain has a remarkable decrement as the reduction of the minimum cross-sectional area. Formulas for determining these values are proposed as a function of the decrement ratio of the minimum cross-sectional area of a corroded bar.