Tetsushi Kanda

Repair and retrofit with engineered cementitious composites

Abstract This article presents the novel use of a super ductile fiber reinforced cementitious composite for repair and retrofit of concrete structures. Research in repair and retrofit demands immediate attention because of rapidly deteriorating and heightened safety requirements of civil infrastructures worldwide. The strain-hardening Engineered Cementitious Composites have been developed with the aid of fracture mechanics and micromechanics. It is emphasized that material ductility, and not just strength, can translate into strong and ductile structural performance. This article is extended from an original version presented as a Principal Lecture at the FRAMCOS-3 Conference at Gifu, Japan in October, 1998.

Influence of Fiber/Matrix Interface Properties on Complementary Energy and Composite Damage Tolerance

This paper reviews recent research on cement based composites design for damage tolerance. Specific focus is placed on the influence of fiber and interface properties on the complementary energy of the composite crack bridging behavior, which in turn governs the mechanics of composite fracture. The theoretical concepts are illustrated with examples of highly damage tolerant cement based composites containing fiber types with and without chemical interfacial bonds. The composite fracture and damage tolerant behaviors are rationalized with the mechanics of steady state cracking in fiber composites.

Full Scale Processing Investigation for ECC Pre-cast Structural Element

Abstract ECC is a pseudo-strain-hardening, highly ductile cementitious composite. However, the major studies on this material have been limited to laboratory scale without experience in full-scale plants. Thus, practical applications of ECC have not been previously investigated. In the current study, full-scale processing experiments were executed, and mechanical and fresh properties were tested, where emphasis was placed on two types of tensile test. It was thus proven that ECC can provide excellent fresh and mechanical properties in full scale production, and a statistical basis for determining tensile property specifications was provided. Furthermore, it was found that flexural tests can be utilized for inspecting tensile properties in daily production. These experimental data were reflected in an actual building construction project that was designed to utilize ECC structural elements. As a result, ECC element production was successfully achieved with the required quality in this project.

Application of SHCC

Utilizing concept for SHCC as a new material, SHCC material evaluation for application, and actual application examples are presented in this chapter. SHCC has been applied to newly constructed structures, making use of its excellent mechanical performance. It has also been used for surface repair of existing concrete structures making use of its finely distributed cracking behavior. Appropriate use of the tensile performance can work out a structural component excellent in both durability and mechanical performance.

SHEAR AND FLEXURAL PERFORMANCE OF REINFORCED BEAM USING DUCTILE FIBER CEMENT COMPOSITE

A structural experiment and analysis were conducted to study the shear and flexural performance of beams strengthened with high performance fiber-reinforced cement composite (HPFRCC). Beams with HPFRCC showed higher shear strength, ultimate flexural moment, and ductility after flexural yielding than reinforced concrete beams. Estimation methods, which considered the tensile characteristics of HPFRCC, reasonably reproduced experimental results.

Experimental and Numerical Studies on Shear Behavior of Deep Prestressed Concrete Hollow Core Slabs

This paper presents experimental and numerical studies on shear behavior of deep prestressed concrete hollow core (PCHC) slabs. For the experimental investigation, two deep PCHC slabs, namely, HC1.320 and HC2.500, were tested at ambient temperature resulting in two distinct failure modes. While Slab HC1.320 failed in a combination of flexure and shear, Slab HC2.500 failed due to diagonal tensile cracking in the webs. The experimental data was compared with the estimated shear capacity from ACI 318-14 and EN 1168:2005+A3:2011. The comparison basically shows that in some instances, deep PCHC slabs can fail at applied loads smaller than those predicted by both codes. In addition, shear-span-to-depth ratio is a decisive factor on shear performance of PCHC slabs. For the numerical assessment, the concrete damage plasticity model in ABAQUS was employed to develop a nonlinear finite element model which can simulate shear behavior of deep PCHC slabs. Results from numerical analyses correlated well with the test data in terms of modes of failure, displacements at failure and failure loads. The validation shows that the proposed numerical model is capable of simulating shear behavior of deep PCHC slabs.

Study on Effect of Heat Elimination by Pipe Cooling System in Beam Using High Strength Engineered Cementitious Composites

In the field of construction, the innovative technique using the coupling beam making use of characteristics of the Engineered Cementitious Composites (ECC) has been proposed, for instance the energy absorption by concentrating the seismic force in the core wall is implemented in high-rise R/C structures (Kanda 2006). Moreover, study with the aim of high strengthening of the coupling beam has been carried out. However, in the high strengthening coupling beam, possible temperature increase in a relatively massive element section exceeding 100 °C due to the heat of cement hydration has been concerned. When temperature in the member exceeds 100 °C due to the heat of cement hydration, the performance of organic fibers (the high-strength polyethylene fibers) is significantly reduced. Hence, in order to control the excessive temperature rise due to the heat of cement hydration, the analytical study was carried out for a pipe cooling system adopted as a countermeasure. On the basis of results of temperature measurement for the ECC coupling beam, design of the pipe layout to control the maximum temperature in the member lower than 90 °C was carried out and thermal properties were also identified. In this report, the experiments for evaluating the effectiveness of pipe cooling were described and the results were discussed.

Structural Behavior and Design of R/SHCC Elements

Structural behavior of steel reinforced SHCC (R/SHCC) elements are discussed in this chapter. Based on the discussion, design approaches for R/SHCC are also investigated. First, in flexure, R/SHCC appears to show similar behavior to regular R/C and its design can be achieved in extension of R/C design by considering short fiber contribution against flexural tensile stress. Second, the shear behavior of SHCC clarified by Finite Element analysis is reviewed. Then the state of the art in shear design approach is summarized. Finally, structural ductility under seismic loading and seismic design concept for beams and columns are discussed.