高性能轻骨料混凝土三轴压强度和变形特性研究

Strength and Deformation Properties of High Performance Lightweight Concrete Under True Triaxial Compression

为了给轻骨料混凝土结构的设计和有限元分析提供精确的本构模型,进行了高性能全轻混凝土、高性能次轻混凝土和普通骨料混凝土的真三轴压试验研究,对3种混凝土的多轴强度和变形特征进行了比较.试验应力比选取低应力比σ_(1)/σ_(3)=0.1和高应力比σ_(1)/σ_(3)=0.25两组,每组变换中间主应力σ_(2).通过比较发现,单轴压条件下轻骨料混凝土横向变形要远大于普通骨料混凝土,在有侧向约束情形下,轻骨料混凝土强度和延性会得到很大程度的改善.在较小侧压应力水平下,高性能全轻混凝土和次轻混凝土三轴抗压强度提高倍数要低于普通骨料混凝土,变形以脆性特征为主;在较高侧压应力水平下,高性能轻骨料混凝土强度提高程度接近于普通骨料混凝土,破坏特征变化为假塑性破坏,表现出良好的延性行为,吸能能力也大大增加.真三轴尤其是高应力比条件下,中间主应力对三轴峰值强度有显著的影响.在三维Haigh-Westergard应力空间建立基于轻骨料混凝土密度等级和品质性能等级的统一多轴强度准则,为不同类型结构轻骨料混凝土结构按多轴强度理论进行设计提供空间破坏曲面的数学表达式.

In order to facilitate the lightweight concrete structural design and finite element(FE)modeling based on the accurate constitutive model,the strength and deformation of high performance all lightweight concrete(HPALWC),high performance semi-lightweight concrete(HPSLWC)and normal weight concrete(NWC)subjected to truely triaxial compression was experimentally studied and compared.The lower and higher lateral compression stress ratio,i.e.σ_(1)/σ_(3)=0.1 and σ_(1)/σ_(3)=0.25,with various middle stress σ_(2) was adopted.The results show that the lateral expansion of HPLWC under uniaxial compression is far greater than the NWC,while an increase in confining pressure leads to an increase in both the strength and deformation of HPLWC.Under the lower confine stress states,the increase of triaxial compressve strength of HPLWC is lower than NWC,and the failure modes show great brittleness.Under the higher confine stress states,the increase of peak stress for HPLWC is almost the same with that of NWC,and the failure modes show obvious pseudoplasticity and a more ductile behaviour with higher energy absorption capacity.The intermediate principal stress affects ultimate strength under true triaxial compression,especially under higher confining pressures.A new unified failure criterion used in three dimensional Haigh-Westergard stress space has been proposed.The model takes into account through two parameter,i.e.the concrete performance grading factor and the density of concrete.The predictive capabilities of the proposed failure criterion formulation have been tested against experimental results on HPLWC specimens considering variable in strength grading and density both.