Behavior of High-Strength Concrete Members Subjected to Combined Flexure and Axial Compression Loadings

Abstract

The use of high-strength concrete (HSC) in structures and bridges has become a common practice worldwide. In bridges, HSC could lead to a reduction in number and depth of the girders as well as an increase in the span length. These features reduce the complexity of a project with reduced number of piers, construction time and cost. Furthermore, the enhanced durability of HSC could result in reduction of the maintenance costs and increase the service life of the structure. In buildings, the sizes of the members could be significantly reduced which could help in the design and construction of higher structures with larger spans. However, due to lack of research data, most of the design codes worldwide limit the applicability of HSC.

A total of 21 plain concrete specimens were tested under combined flexure and axial compression to evaluate the stress-strain distribution of HSC in the compression zone of flexural members. The variables considered in this investigation were mainly the strength of concrete and the age of the specimen. The measured stress-strain curves and stress block parameters, including the influence of the concrete strength, were compiled with the data in the literature to evaluate the fundamental characteristics of high-strength concrete in the compression zone of flexural members. A total of 42 cylindrical specimens and 18 prism specimens were used to evaluate the creep and shrinkage properties of HSC. The variables considered in this investigation were the concrete compressive strength, specimen size, curing type, age of concrete at loading and loading stress level. The creep coefficients and shrinkage strains were obtained for the range of concrete compressive strength, evaluated and compiled with the current predictions according to the design codes.

Using the test results of this research and other researches in literature, revisions to the LRFD Bridge Design Specifications (2004) are recommended to extend the applicability of its compressive and combined compressive and flexural design provisions to concrete compressive strengths up to 18 ksi.