Behavior of high-strength concrete under biaxial stresses

Four different types of high-strength concrete plate specimens (150 s 150 x 40 mm) were tested under different biaxial load combinations. The specimens were subjected to biaxial combinations covering the three regions of compression-compression, compression-tension, and tension-tension. The principal deformations in the specimens were recorded and the track patterns and failure modes were examined. Based on the strength data, the failure envelopes were developed for each type of concrete. The test results revealed that the failure envelopes of concrete depend on the concrete strength and on the type of aggregates. The biaxial compression-tension region reflected a significant difference in the behavior between high-strength and normal strength concrete The compression capacity was radically reduced for high-strength concrete when a small tension is introduced in the other direction. A second pronounced difference was found between the high-strength lightweight and the high-strength normalweight concrete. High-strength lightweight concrete indicated higher strength gain under biaxial load at all stress ratios compared to normal and high-strength concrete The deformation characteristics indicated that high-strength concrete shows a linear behavior up to a higher stress than normal strength concrete. It also has higher discontinuity limits. The observed failure modes showed that there is no fundamental difference in the crack patterns and failure modes due to the increase in the compressive strength of the concrete or due to the use of lightweight aggregates under different biaxial loading combinations.