| Stone structure buildings with regional characteristics widely exist in the coastal areas of Fu Jian province in China.As the main force component of the stone structure building,stone walls result in poor seismic performance because of the low strength,the uneven thickness of ash joints and other factors.Consequently,the seismic reinforcement of the existed stone masonry wall is in urgent demand.Ultra-high performance concrete(UHPC),as a structural reinforcement material,has the characteristics of high compressive strength,compaction and good homogeneity,possessing its unique advantages.In this study,a kind of organic fiber(POM)rather than steel fiber is involved to form the UHPC.Initially,the composition optimization and performance regulation of UHPC are implemented to prepare UHPC with excellent performance in civil engineering.Furthermore,experiments are conducted on the fluidity and mechanical properties of UHPC,shrinkage properties,and inter-facial bonding properties with stone.Ultimately,the seismic performance test studies and numerical simulation are carried out for the whole reinforced masonry wall with inlaid UHPC.The main work and results are summarized as follows:(1)The dissertation studies the effect of water glue ratio,limestone powder dosage,POM fiber volume and water reducing agent on working performance and mechanical properties of POM-UHPC.The results show that the mobility of UHPC increases with the increase of water glue ratio,the increase of limestone powder does not significantly improve the mobility of UHPC;with the increase of POM fiber volume,the mobility of UHPC basically remains changed slightly;with the increase of water reducing agent,the mobility increases greatly.The above shows that the water glue ratio and water reducing agent have a great influence on UHPC flow,and the amount of water reducing agent has the most significant effect.Among four parameters,the water-cement ratio and water-reducing agent have a significant effect on the setting time of UHPC.However,the amount of limestone powder and the volume of POM fiber have basically no effect on the setting time of UHPC.With the increase of water-cement ratio,limestone powder and water reducing agent,UHPC mechanical properties(compressive,tensile and bending strength)increase first and then decrease;with the increase of POM fiber volume,the bending strength and tensile strength increase,while the compressive strength increases first and then decreases.After comprehensive comparison,the dissertation gives the selection range of each mix ratio under the optimal performance of POM-UHPC,the water glue ratio is 0.15～0.20,the amount of limestone powder between 40% and 45%,and the volume of POM fiber between 1.0% and2.5%(2)The dissertation studies the influence of water-cement ratio,limestone powder mixture,POM fiber volume dosage and water reducing agent on the free shrinkage of UHPC.The influence of reinforcement layer thickness and existing stone surface roughness on constraint shrinkage was studied,and the shrinkage performance was improved by adjusting various parameters.The results show that : With the increase of the cement ratio,limestone powder and POM fiber,the effect of the UHPC ratio was most significant.The UHPC constraint shrinkage value decreases as the reinforcement layer thickness increases.Under the same reinforcement layer thickness,the UHPC constraint shrinkage decreases with the increase of the stone surface roughness.Therefore,in the reinforcement of the stone wall,appropriately increasing the roughness of the stone interface is helpful to reduce the development of UHPC shrinkage crack,which can improve the crack resistance of UHPC.(3)The dissertation probes into the bonding force between UHPC and stone of inter-facial zone which caused by interface roughness,moisture and interface agent through UHPC and stone specimens and ABAQUS software.The results show that the bond strength of POM-UHPC and stone specimens is positively correlated with the roughness,and the relationship between the bond strength is as follows: 30mm> 20mm> 10mm> groove>natural surface> smooth interface;under the same interface roughness,the bond strength of wet group is significantly reduced compared with the drying group;the interface bond strength of three interface agents: UHPC> cement net slurry> red clay mixed mortar.Finally,the constitutive model of POM-UHPC and stone double-sided shear interface is proposed,and the formula of oblique shear resistance and double-sided shear strength is obtained,which solves the calculation formula of the existing that is not suitable for predicting the interface bond bearing capacity between POM-UHPC and stone.(4)The dissertation studies the shear resistance of UHPC on the whole rubble masonry wall,4 stone masonry walls were made,of which 2 were not reinforced and 2 stone walls were reinforced with UHPC joints.The quasi static test study was carried out respectively and finite element analysis was conducted.The results show that the shear strength of the wall and the shear strength of the UHPC wall is proposed,which considers the compressive stress,mortar strength,aspect ratio,mortar fullness and uneven shear stress,and the calculation results agree with the test data.The proposed calculation formula of shear strength of UHPC reinforced stone wall and the test data are only within ±10%,which can be used for future reference in the design of stone masonry wall reinforcement. |
PDF Full Text Request