PERFORATING THE MASONRY WALLS IN REHABILITATION OF MASONRY BUILDINGS USING CENTER CORE METHOD

Center core method is advanced method for rehabilitation of masonry buildings. First, vertical holes with given intervals are perforated on the walls to the footing and then reinforcing steel bars are embedded in the holes and cement grout will be injected finally to create bond strength between wall and bars. This is a nondestructive method which could be achieved without evacuation of the buildings. In Iran there are many unreinforced masonry and historical buildings which need to be retrofitted against seismic hazard, therefore this method could be utilized widely. Since the beginning of building rehabilitation in Iran, consulting engineers have sometimes offered this method but in spite of economical benefits it has never been used because of feasibility uncertainties and the difference between masonry walls in Iran and other countries. The main contribution of this study is to investigate drilling techniques and equipments and design of drilling bit used in this method without deterioration and cracking of the wall. To achieve this aim four holes (7m high) were perforated in an unreinforced masonry building by 10 different drilling bits and 2 different drilling, then the method effective and nondestructive technique and equipment were adopted by observing and controlling the cracks and drilling bit penetration along the wall. It was found that the combination of coring and noncoring drilling bit caused no cracks on the finishing and the least deviation along the boreholes and the most effective drilling was obtained by minimizing the bit pressure, balancing its rotation velocity and minimizing air pressure for removing cuttings. The hydraulic drilling machine was selected due to its lightness compared to other machines.

Keywords:

Center Core , Masonry Building , Historical Building , Rehabilitation