A theoretical study was carried out to investigate the effects of increasing concrete strength on the depth of rectangular beams. Two series of beams were investigated. The first series comprised reinforced concrete beams with spans from 6 to 15 m, and the second comprised prestressed concrete beams with spans from 12 to 30 m. The concrete strength ranged from 20 to 120 MPa and from 30 to 120 MPa for the reinforced and prestressed concrete beams, respectively. The results show that for rectangular concrete beams, an increase in concrete strength results in a rather significant reduction in the beam depth, whereas for rectangular prestressed concrete beams no significant reduction in the beam depth is gained from increasing the concrete strength because the deflection governs the design.

The increase in the number of high-rise reinforced concrete buildings has accelerated the research on the manufacturing and development of high strength materials. Ministry of Construction, Japanese Government, organized a national research project from 1988 to 1993 for “the Development of Advanced Reinforced Concrete Buildings using High-strength Concrete and Reinforcement.” This paper introduces the earthquake resistant design guidelines developed as a part of this technical project. The scope is limited to the building height of 200 m, the concrete strength of 60 MPa, and the steel strength of 700 MPa.

The use of high strength concrete has been increasing in the construction of high-rise earthquake resistant buildings in Japan. However, design guidelines have not been fully developed for reinforced concrete buildings with concrete compressive strengths higher than 35.3 MPa. Therefore the Japanese Building Research Institute initiated “New RC Project” aimed at establishing design guidelines for buildings constructed using high strength concrete. The project started in 1988 and extensive research has been conducted at several research institutes and universities. Shear tests on beams and columns with high strength concrete were also conducted as part of program to establish the shear design method for them. This paper summarizes findings from the New RC tests and others on shear strength of reinforced concrete beams and columns with high strength concrete and high strength shear reinforcement. The accuracy of currently available shear strength equations are then examined. The shear design method proposed by the Shear Working Group of the New RC project is also introduced in this paper.

This paper presents an overview of the provisions for anchorage and development of reinforcement in concrete for New Zealand concrete design code : NZS 3101: 1995 (1). These provisions take into account the nature of high strength concrete (compressive strength f’c > 55 MPa (8000 psi)) and the expected performance under seismic loading. The criteria for development lengths for straight reinforcement (with specific surface deformations) and those for bars terminated with hooks are largely based on recent studies of Sozen and Moehle and ACI 318: 1989. Simple, conservative equations are presented along with less conservative equations of more complexity.

The first purpose of this report is to introduce experiments on 91 square confined concrete specimens and 59 circular ones with high strength materials subjected to monotonic and concentric axial loading conducted in Japan recently. The concrete strength of specimens ranged from-27 MPa to 132 MPa and the strength of transverse reinforcement ranged from 173 Mpa to 1360 MPa. Small size specimens with section dimension of about 200 mm have been conducted mainly but it is notable that four quasi-real size specimens with 470 mm square section were tested through the New RC Projects. The second purpose of this report is to introduce the recent research works on models, examining their feasi-bility. Conclusions included the following: (1)Regarding the maximum strength of the square confined specimens, the predictions with the models proposed by Sakino et al. and Watanabe et al. were accurate enough especially for quasi-real size specimens. However, the accuracy of the prediction for the axial strain became much worse compared with that for maximum strength in each model. (2)Regarding the stress-strain curves, the relations of the model by Sakino were quite similar to the observed curves until the end of the loading of quasi-real size specimens. (3)Regarding the effects of the material strengths, assuming that the model by Sakino was true, it was concluded that the stress increase was indc-pendent of the concrete strength and proportional to the strength of transverse reinforcement as far as it reached 6X7 MPa. On the other hand, the strain increase depended on the concrete strength: it decreased with the increasing value of the concrete strength.