Research On The Mechanical Behavior Of Fully Grouted Block Masonry Wallettes And Reinforced Concrete Block Masonry

The reinforced concrete block masonry structure is a structural system composed by the material of masonry block,steel rebar and concrete.It not only has well mechanical performance and construction efficiency,but also shows typical green building features such as conservation of energy,land,water,materials and environmental protection.It has a broad development prospect all around the world,ranging from middle-rise buildings to high-rise buildings.On the other hand,the reinforced concrete block masonry structure is the future direction of masonry structure,which could meet the market of urban construction in China and conform to the strategy of national earthquake disaster reduction.At present,the current national standard,“Code of Masonry Structure” presents the basic mechanical properties of concrete block masonry based on unreinforced masonry structures.In this context,the proposed parameters could not perfectly meet the requirements of reinforced concrete masonry without consideration of stress versus strain curves under uniaxial compression and direct shear.Furthermore,the research and application of reinforced concrete block masonry structure is severely restricted due to the lackness of specified finite element method and the model for the reinforced concrete masonry.Thus,the present study focus on the basic mechanical properties of concrete block masonry and shear performance of reinforced concrete masonry shear wall,the main contents are summarized as follows:Firstly,in order to investigate the compressive performance of block masonry,36 pieces of fully grouted concrete block masonry wallettes are designed and prepared considering five different schemes of strength matching.The failure modes of hollow masonry specimens and grouted masonry specimens are summarized.The effects of block strength,concrete strength and loading pattern on compressive strength of block masonry are analyzed.The accuracy of the existing formula in predicting elastic modulus of masonry is verified according to the statistical data.Then,the stress-strain curves of the masonry under uniaxial compression are obtained,and the stress-strain relationship of the masonry is established using the nonlinear fitting.In addition,the formula of plastic strain evolution is obtained by numerical fitting.Furthermore,the results by proposed model are in good agreement with the experimental results which are better than other models.Secondly,the finite element model is established in simulating the compressive behavior of concrete block masonry.And the compressive strength of grouted block masonry is also trained by adopting the artificial neutral network method.The artificial neural network(ANN)model is established based on the collection of 566 experiment data considering grouted ratio,block strength,mortar strength and concrete strength in input layer.The simplified formula is also proposed,and the prediction results are better than these results by existing strength formula.Then,the deterministic finite element model is established in ABAQUS,with respect to the spatial variability of the material,the Monte Carlo stochastic finite element model is also proposed.The results show that the stochastic finite element model are better than the corresponding deterministic finite element model in the prediction of masonry strength and stress-strain curves.Thirdly,in order to analyse the shear performance of the block masonry and the shear strength of the reinforced masonry shear wall,35 grouted masonry prisms are tested under direct shear stress,the failure modes of hollow specimens and grouted specimens are summarized and the influence of the material strength variation on the shear strength of the specimens is analyzed.The accuracy of the existing strength calculation model is evaluated based on the 177 shear strength test results.According to the experimental data,the proposed load displacement curve equation under direct shear is consistent with the test results.With respect to shear strength of reinforced concrete masonry shear wall,the ANN model and the adaptive network-based fuzzy inference system(ANFIS)with 11 input parameters are established.The results show that,the artificial intelligence method is effective on prediction of shear strength within the data space of the collected results.Finally,a modified MVLEM with the consideration of the bending-shear coupling element of the block masonry is established based on the Open Sees software.The constitutive model of the grouted masonry is introduced and the simplified shear-slip relationship is brought into the platform.Six reinforced concrete masonry shear walls with the thickness of 290 mm are selected and simulated.Compared with the finite element model of using beam-column element and bending-shear uncoupling beam-column element,the results indicate that the bending-shear coupling MVLEM can well predict the peak bearing capacity,peak deformation,skeleton curve,stiffness degradation and pinching effect in hysteresis curve of the specimen.Overall,the MVLEM model is suitable for simulating the shear behavior of reinforced concrete masonry shear walls.