Experimental Study On Seismic Performance Of RC Column Strengthened By Steel Jacket And Prestressed Steel Wire Mesh With Polymer Mortar

From the point of view of economy saving and environment protection,it is of great significance to strengthen the following three types of buildings by reinforcement technology:(1)Repairable buildings damaged by earthquake;(2)Old buildings that do not meet the current seismic fortification requirements;(3)The buildings that fail to meet the requirements of the structural design code due to human negligence in survey,design and construction.Therefore,the development of more convenient and effective building structure reinforcement technology to reinforce and reuse these buildings has better social benefits.Combined with the characteristics of the existing reinforcement method of the prestressed steel jacket strengthening method and the prestressed steel wire mesh with polymer mortar strengthening method,the research group optimized and designed a set of reinforcement method for RC column: the steel jacket and prestressed steel wire mesh with polymer mortar reinforcement method.Based on the proposed reinforcement method,seven RC columns were designed in this paper(including two contrast columns and five strengthening columns)with three factors as variables: concrete strength grade,whether polymer mortar is applied during reinforcement,and damage degree.The main work is as follows: specimen making;taking the width of damage crack on the surface of RC column as damage index,pre-damage treatment on two RC columns;strengthening specimen.Finally,seven specimens were tested by pseudo-static loading and their seismic performance indexes were compared and analyzed.The main conclusions are as follows:(1)Compared with contrast specimen,except for the RC column did not wipe the polymer mortar,the strengthened RC columns did not appear maindiagonal cracks through the whole section.The maindiagonal cracksappear on both sides of steel wire mesh intersection area that hasn’t constraint.Under the restraint of steel jacket,no obvious damage occurred to the column root.The cracks on the polymer mortar surface of strengthened RC columns with more serious damage are not fully developed.(2)The hysteretic curves of RC columns with concrete strength grade C25 and C35 are relatively full after reinforcement.Compared with the strengthened RC column without polymer mortar,the hysteresis curve of the strengthened RC column with polymer mortar is fuller than that without polymer mortar.The smaller the damage degree,the fuller the hysteretic curve of strengthened RC column.(3)After reinforcement,the ductility,maximum bearing capacity and energy dissipation capacity of RC columns with concrete strength grade C25 and C35 have been significantly improved.Compared with the contrast column,the initial stiffness of the strengthened column with two kinds of concrete strength is also improved,and the stiffness of the strengthened column with the same displacement is greater than that of the contrast RC column.It is proved that the strengthening technique proposed by the research group is also effective for the seismic strengthening of RC columns with low concrete strength.(4)After the RC column is strengthened by the reinforcement method proposed by the research group,the ductility of the RC column is improved significantly under the two working conditions of applying polymer mortar and not applying polymer mortar,and the displacement ductility of the column is not significantly different under the two working conditions.However,the bearing capacity of RC column coated with polymer mortar is significantly improved,and its energy consumption capacity is also better than that of RC column without polymer mortar.Under the condition of no polymer mortar,the initial stiffness of RC column has no obvious change,and the stiffness degradation process is basically the same as that of the contrast RC column.It is proved that the effect of steel jacket and prestressed steel wire mesh on improving the ductility of the column is significant,while the effect of polymer mortar on the bearing capacity of the column is very significant.(5)When other conditions are the same,the damage degree of RC column has a great influence on the seismic performance of the strengthened RC column.The severity of the pre-damage is greater,the recovery degree of the initial stiffness,ductility,bearing capacity and energy dissipation capacity of the strengthened RC column is smaller.