| The study on masonry structure durability is a significant research work towards ancient building preservation and evaluation of the anti-seismic property of existing masonry buildings, which however has been overlooked for long time. Now, a large quantity of the existing masonry buildings in our country is suffering the freeze-thaw damage in varying degrees, and this damage will continue to be one of the principal influential factors to masonry structure durability. This paper will give an insight to the research of the mechanical property of recycled concrete brick masonry subjected to the freeze-thaw circulation; specific studies are as follow:Cement mortar, lime mortar and fly-ash mortar are chosen as research objects on behalf of the modern, ancient and contemporary typical building mortars respectively, aimed at studying on their durability behaviors under freezing and thawing, meanwhile the effect of water-binder ratio, lime content and fly-ash content on anti-frost property is analyzed. The changing patterns of mass loss, relative dynamic modulus of elasticity and compressive strength of mortars under freeze-thaw are revealed. Dynamic elastic modulus prediction model considering water-binder ratio, plaster content and fly-ash content and a compressive strength attenuation model are put forward.The effect of freeze-thaw cycle on the recycled concrete masonry shear-resistance are studied by fabricating 96 testing specimen, the damage pattern and sheering strength of different cementing materials specimens are analyzed comparatively, the effect of thaw-freeze cycle on the masonry shear-resistance are revealed and the relative factors are indicated. Meanwhile the effective rule on the recycled concrete brick masonry’s shear-resistance behavior subjected to freeze-thaw damage are revealed, the effect of mortar pores on the masonry anti-shear capacity are studied from a micro perspective, the influential factors of shear-resistance property recycled concrete masonry under freeze-thaw are studied. A freeze-thaw damage attenuation model of recycled concrete masonry shear-resistance is obtained which can provide date and theoretical supports to the evaluation of existing masonry structure durability.Fracture development and damage pattern of RCB compression specimen are described by the axial compression-resistance test of 72 specimens. Stress mechanism of RCB compression specimen under freeze-thaw are analyzed, the effect of freeze-thaw on the performance index of RCB compression specimen(axial compression strength, elastic modulus, poisson radio and stress-strain curve) are studied, then the axial compression strength model and elastic modulus model considering freeze-thaw damage are put forward. The constitute model of RCB masonry under freeze-thaw cycle is obtained by the form of power function.Based on damage mechanism theory and strain equivalence principle, the total damage of axial compression masonry under freeze-thaw cycle is considered the nonlinear coupling of freeze-thaw damage and axial compression damage, the damage degradation process and damage evolution approach are analyzed, meanwhile total damage evolution formulation is deduced. The axial compression constitute model considering freeze-thaw damage is put forward, which is verified by test data.8 RCB composite wall model 1:4 scale are fabricated then placed in the freeze-thaw circumstance. The damage pattern of 8 RCB composite wall model under lower cycling loads are analyzed. The mechanic index(strength, stiffness and hysteretic energy) of RCB composite wall under freeze-thaw cycles are studied.Based on material damage theory, hysteretic model with three lines considering freeze-thaw damage are put forward and the calculate method for the characteristic points is illustrated. This model is verified based on the test data. Meanwhile the damage attenuation index calculated based on the test data is induced to freeze-thaw damage hysteretic model. |
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