Abstract:The strength and deformation experiments of plain and high-strength high-performance concrete (HSHPC) and normal strength concrete(NSC) with various stress ratios under uniaxial,biaxial and triaxial compressions are completed,using the large static-dynamic true-triaxial machine. The multiaxial compression tests are performed on 100 mm×100 mm×100 mm concrete specimens with friction-reducing pads(three layers of butter and three layers of plastic membrane) placed between platens and specimens under monotone proportional loading. Failure modes and failure mechanism of specimens are described. The multiaxial strengths,strains under peak stress and stress-strain curves are measured;and the influence law of the stress ratios and the difference of multiaxial mechanical property between HSHPC and NSC are also analyzed. The experimental results show that ultimate strength s3f and principal strain e3p of HSHPC and NSC under multiaxial compression are greater than uniaxial compressive strength ¦c and strain ecp under all stress ratios respectively,especially under triaxial compression. Moreover,the increasing multiple ratios of s3f and e3p relatively to ¦c and ecp depend on brittleness-stiffness of concrete,stress state and stress ratios. The formula of Kupfer-Gerstle and Ottosen¢s failure criterion for plain HSHPC and NSC under biaxial compression and multiaxial stress states is proposed,which provide experimental and theoretical foundation for strength analysis of HSHPC and NSC structures such as bridge and tunnel engineering,underground engineering,and building engineering,etc..