Previous studies using pullout-type tests comprising monotonic, unidirectional cyclic, and reversed cyclic loads have shown that bond between reinforcing bars/prestressing strands and concrete can be significantly enhanced by replacing the conventional concrete with high-performance fiber-reinforced cement composites (HPFRCCs). This is attributed to the fact that, compared to plain concrete and conventional fiber-reinforced concrete (FRC), HPFRCCs exhibit a strain-hardening response under tension up to large strains, thereby preventing the concrete from deterioration under bond action. Pullout test results provide the bond stress versus slip relationship that can be considered the constitutive property of the steel-to-HPFRCC interface. Since the post-cracking tensile stress and strain of fiber-reinforced cement composites are the fundamental characteristics that distinguish them from conventional concrete, the HPFRC tensile stress-strain response obtained from direct tensile tests was used to derive the local bond stress-slip models presented in this paper. It is shown that the proposed models are more concise than previous models suggested for FRC and give good agreement with test results.

This paper presents a simple direct method to determine the external tendon configuration required for a desired increase in load-carrying capacity of continuous beams. The tendon layout is selected based on the concept of equivalent loads, but need not be concordant. By considering the collapse mechanism of the beam, the increase in load-carrying capacity can be related directly to the tendon force. It is shown that the increase in load-carrying capacity is partly due to an increase in the force in the compression zone arising from the horizontal component of the prestressing force, and partly due to the upward components of the prestressing force. The method was verified with a test program on six two-span continuous beams, in which the tendon profile and loading pattern were varied. Comparison of the test results and those available in the literature showed that the proposed method gives a reasonably conservative design. A simplified method based on the direct balancing of increased loads is also proposed.

Short-fiber reinforcement is commonly added to cement-based materials to improve various aspects of their durability and life-cycle performance. Effective designs of Fiber Reinforced Cement Composites (FRCC) depend not only on material composition, but also on their methods of processing. In particular, the distribution of fibers within a structural component can significantly affect its resistance to cracking and, therefore, its durability when exposed to severe environments. Probability-based analyses can be used to accommodate such factors in life-cycle performance evaluation, in which the relevant performance measures are described by probability distributions and their evolution over time. This paper concerns the simulation of FRCC materials using lattice models, in which the individual fibers are explicitly modeled within the material domain. This approach facilitates the study of non-uniform fiber dispersions and their potential effects on structural performance.

Prestressed (PS)concrete technology is being used all over the world in the construction of a wide range of structures, particularly bridges. However, many PS bridges have been deteriorating even before the end of their design service-life due to corrosion and other environmental effects. In view of this, a number of innovative technologies have been developed in Japan to increase not only the structural performance of PS bridges, but also their long-term durability. These include the development of novel structural systems and the advancement in construction materials. This paper presents an overview of such innovative technologies on PS bridges including a brief discussion of their development and applications in actual construction projects. Some noteworthy structures, which represent the state-of-the-art technologies in the construction of PS bridges in Japan, are also presented.

This paper summarizes a series of tests performed on strain hardening High-Performance Fiber-Reinforced Concrete (HPFRC) coupling beams with span length-to-depth ratios (ln/h) of 1.75 and 2.75. These tests show that incorporating HPFRC simplifies the detailing required to ensure a stable response of coupling beams subjected to earthquake induced displacement reversals. Results from five tests of precast coupling beams, three with ln/h = 1.75 and two with ln/h = 2.75, are reported herein. Strategies for embedding the precast HPFRC coupling beams into the structural walls without interfering with boundary element reinforcement were explored. Test results confirm that HPFRC can reliably confine diagonal reinforcement and ensure stable hysteresis behavior. HPFRC was also found to significantly increase shear strength, thereby forcing a flexurally dominated failure mode with modest stiffness degradation and excellent energy dissipation. A revised coupling beam design philosophy is outlined in order to ensure ductile flexural behavior.