Four different types of high-strength concrete plate specimens (150 s 150 x
40 mm) were tested under different biaxial load combinations. The specimen
s were subjected to biaxial combinations covering the three regions of comp
ression-compression, compression-tension, and tension-tension. The principa
l deformations in the specimens were recorded and the track patterns and fa
ilure modes were examined. Based on the strength data, the failure envelope
s 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 compressio
n-tension region reflected a significant difference in the behavior between
high-strength and normal strength concrete The compression capacity was ra
dically reduced for high-strength concrete when a small tension is introduc
ed 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 bi
axial load at all stress ratios compared to normal and high-strength concre
te The deformation characteristics indicated that high-strength concrete sh
ows 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 m
odes due to the increase in the compressive strength of the concrete or due
to the use of lightweight aggregates under different biaxial loading combi
nations.