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.

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.

The synergy between self-consolidating concrete (SCC) and steel fiber-reinforced concrete (SFRC) technologies may yield, besides the well known and assessed characteristics of each single technology, several interesting peculiar advantages that can be fruitfully exploited by the construction industry, mainly in the field of precast construction. Better controlled fiber dispersion, improved fiber-matrix bond, and enhanced durability due to the higher compactness of the SCC matrix are among the most relevant issues to which the largest part of research efforts were dedicated in the very last decade. The robustness of self-consolidating steel fiber-reinforced concrete (SCSFRC), which relies on sound mix-design methodology and on effective dedicated quality control procedures, has been demonstrated to be crucial in order to achieve the above recalled advantages. This paper summarizes the most significant results of the research activity carried out by the authors in this field, furthermore underlying the outcomes with reference to structural applications.

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.

Parameterized material models for strain softening fiber-reinforced concrete are used to express closed-form solutions of moment-curvature response of rectangular cross sections. By utilizing crack localization rules, one can predict flexural response of a beam. A parametric study of post crack tensile strength in the strain softening model is conducted to demonstrate general behavior of deflection softening and deflection hardening materials. Uniaxial and flexural test results of several polymeric fiber-reinforced concrete mixtures are used to demonstrate the applicability of the algorithm to predict load-deflection responses. The data are compared with the ASTM International test Method C1599, which represents the residual strength of the sample after cracking has taken place. The simulations reveal that uniaxial tensile stress-strain relationship is under-predicted using the flexural response test results.