Ali Bakhshi[1], Mohammad Ali Ghannad[2], Mohammad Yekrangnia[3], Hamid Masaeli[4]

Evaluation of Seismic Performance of Adobe Dome-roof Structures Retrofitted by Steel Rods and Mesh Using Shaking Table Facility

In this article, the seismic performance of a typical adobe building (2:3 scale) is investigated initially through shaking table tests. The selected excitation is Zarand Earthquake (2005), Chatrood station. Since the scaling of the models was performed according to Gravity Forces Neglected procedure, the acceleration and velocity in the model were amplified and decreased 1.5 times, respectively. Also the records were intensified in the time domain and the velocity amplitude was remained intact. Based on the recommendation of Iranian Code of Practice for Seismic Resistant Design of Buildings for regions with very high seismicity, the PGA of the record was scaled to 0.35g. The unretrofitted model was excited at the levels of 25%, 70%, 100% and 125% and was destroyed in the last stage due to detachment of perpendicular walls followed by roof collapse. The performance of the model and shaking table were recorded by 13 accelerometer and 5 displacement transducers. Also 13 high speed and high resolution cameras recorded the response of the model (including the graded papers to capture maximum deformation of walls on top of the dome).

Considering the performance of the unretrofitted model, the retrofitting plan was directed toward two targets: maintaining the integrity and box-like behavior of the structure and preventing the in-plane tensile and shear cracks from widening. The implemented system was made up of: 8 horizontal steel rods which tied the parallel walls and welded steel mesh on one side on the walls which covered only the upper half of them without any shotcrete. The retrofitted model was excited at levels of 25%, 100%, 125%, 150% and 175% and withstood acceptably without undergoing any serious damages. The experienced damages were from higher behavioral modes, i.e. the step-diagonal cracks in some wall originated from torsion. Several strain gages were installed on steel rods in order to monitoring their effective contribution during excitation