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Hydraulic steel gates are commonly used for their superior characteristics in carrying both tensile and compressive stresses. Corrosion, operation, and maintenance costs make it essential to search for suitable alternatives. In this research, Glass Fiber Reinforced Polymers (GFRP) were investigated as a promising choice that can be used to resist flexure stresses as in case of hydraulic gates. Firstly, typical mechanical tests were conducted on nine specimens made of pure steel beams, four ribbed steel beams, twenty-four specimens of pure GFRP beams, along with four combined specimens from both materials. GFRP beams were also used in cooperation with polyester cemented sand to form a sandwich like beam. It was concluded that beams from GFRP achieved similar flexural capacity of steel beams of slimmer thickness. Combinations of steel and GFRP show satisfactory results while maintaining member ductility. The load capacity of the strengthened steel beams increased by 80% to 97% compared to specimens made from steel only. Failure modes for all specimens were introduced and compared. Moreover, numerical investigation was conducted using ABAQUS nonlinear module. Finite element models for three small gates of dimensions (1.0 x 1.0 m). A steel gate of thickness 14mm, Pure GFRP gates of thicknesses 29mm and 45mm were simulated. The 29mm GFRP gate was able to bear almost the same loads of the steel gate with equivalent deflection. Finally, it can be concluded that for small-scale hydraulic gates, GFRP can effectively be used as a suitable alternative for steel gates after setting limitations for failure strains.

In the Framework of identifying defects in structures, Damage Index Method (DIM) is considered one of the trustable tools used intensively. In the present research, DIM – modal displacement based - was applied on experimental data to detect damage for masonry piers. Damage index (DI) was obtained by comparing modal displacement functions for damaged and sound conditions. Firstly, two scaled down piers were prepared experimentally for examination. The piers were of same unit area while the thicknesses were 170, and 260 mm, respectively. The physical models were subjected to different artificial crack patterns. The cracks were created for each pier on three steps representing different intensity of damage. The piers were then examined under free vibration mode at sound condition and after each degradation. The collected records were processed, and DIM was applied. Furthermore, parametric numerical analysis was used to study the effect of crack dimensions, location, shape, and repetition among the simulated piers. The results showed that the selected DI was effective in detecting cracks in masonry structures for all examined cases. Moreover, the investigation showed that as the severity of cracks increased, the identification of damage became easier and was reflected in an increase in DI value. DIM was also able to detect expected route of cracks. On the other hand, DIM can’t be used to obtain degradation level directly but for comparison between severity of cracks in different stages of damage.