Hiroyuki Iwase

Failure Behavior and Structural Design of Concrete Members Reinforced with Continuous Fiber Reinforcing Materials

Continuous fiber reinforcing materials (CFRM), which are made of continuous fibers such as aramid, carbon, etc., bound with resin, are expected to be substituted for steel bars in reinforced and prestressed concrete structures. CFRM are free from corrosion but brittle and the Young’s modulus is low as compared with steel bars. In this paper, the features of CFRM are outlined, and then the ductile and/or brittle failure behavior are investigated using 3-element “parallel” and “series” systems. The favorable failure modes are discussed with relation to the members with CFRM.

FAILURE BEHAVIOR AND DESIGN METHOD OF REINFORCED AND PRESTRESSED CONCRETE BEAMS HAVING HIGH STRENGTH AND HIGH TOUGHNESS

ABSTRACT The purposes of this study are to establish the structural toughness design procedure of reinforced concrete (RC) and prestressed concrete (PC) beams through an energy method and to develop high performance RC and PC beams having high ultimate strength and high toughness. RC and PC beams with different amount of reinforcing and prestressing bars were loaded up to the complete failure. Plain concrete and steel fiber reinforced concrete were adopted. The degree of the ductile failure behavior of RC and PC beams could be roughly controlled by the proposed ductility index λ, which is defined by the sectional constants and the material properties.

Toughness Evaluation and Its Application to Concrete Structural Design

The evaluation, improvement and application of concrete toughness are discussed. It is shown that the differential signal between factored load and displacement is effective to control unstable failure of concrete specimens at loading tests. The relations among impact load, displacement, kinetic energies and duration of concrete beams subjected to impact are presented. Concrete having both high toughness and high strength can be produced by adding steel fibers at high percentage into high strength cement concrete or polyester resin concrete. The analytical relation between the compressive toughness of concrete and the toughess of RC (reinforced concrete) beams in bending is derived. The ductility index is proposed and its validity is proved by experiments of PC (prestressed concrete) beams.