Figure 4. Repaired model and strengthened minaret after phase 1 testing.

Figure 5. Collapse of the upper part of the minaret.

Figure 4. Repaired model and strengthened minaret after phase 1 testing.

placed on four sides along the length of the minaret in vertical direction for the purpose of its stiffening.

To confine the structure, strips with a width of 10 cm were placed at four levels along the height of the minaret in horizontal direction, while a strip with a width of 20 cm was placed at its base.

2.3 Phase 2 - Testing of repaired model and strengthened minaret

Before the seismic tests, the dominant frequencies of the model were checked by random excitation.

For the minaret dominant frequency was 4.7 Hz, while for the mosque two frequencies were dominating: f = 7.4 Hz and f = 9.6 Hz.

During this testing phase, 11 tests were performed with input acceleration between 0.2 g to 1.5 g. The first cracks on the minaret occurred under input intensity of 0.34 g, which indicated that the applied strengthening enabled stiffening of the minaret and increasing of its bending resistance. The initial cracks in the mosque appeared under input intensity 0.42 g.

During the next tests, the cracks developed and at input level of 0.49 g, the upper part of the minaret totally collapsed (Fig. 5).

After reaching the max input acceleration of 1.5 g, the mosque model was heavily damaged and the testing was stopped.

There were cracks in the walls and also in the dome

Figure 6. Damaged model after phase 2 testing.

The characteristic response parameters during the seismic tests are given in Table 1, while the representative time histories for the final test with an input intensity of 1.5g are given in Figure 7.

2.4 Strengthening of the model

After the final test of the model in phase 2 the minaret was removed and the mosque rebuild on damaged parts. Then the model was strengthened. The main adopted principle in strengthening of the model was that the methodology to be applied be reversible and invisible. Hence, the cracks in the damaged model were not repaired by injection, but a concept was adopted that the model be strengthened to the conditions after the preceding tests.

Table 1. Performed seismic tests, phase 2.

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