Mohamed Mady

Experimental modal analysis (EMA) has grown steadily in popularity since the advent of the digital FFT spectrum analyzer in the early 1970’s. Today, EMA has become widespread as a fast and economical technique for studying the dynamical behavior of real full-scale civil structures in order to find the modes of vibration that are inherent properties of these structures. During the last decade, finite element analysis has been integrated in the design and evaluation processes since it is an easy method in spite of the material properties and boundary conditions that are often not well known.
In this research work, modal testing approach had been utilized to evaluate the FE results in order to complete the modelling update that will lead to have a full-scale simulation between the mathematical model and the actual structure. Four studied cases had been selected and examined by an accelerogragh and the natural frequencies and corresponding mode shapes were extracted. In addition, 3D FE model for each case was created, and its results were compared with the previous extracted data by taking into consideration two affecting factors of the material used in these structures (concrete strength and brick Young's modulus). The process of modelling update was suggested for each case, and a comparison between the actual measured data and the Egyptian code formula results for the fundamental period was established.
Finally, the study presents a number of conclusions and recommendations regarding the EMA. It has been shown that the EMA process can be used to insure the accuracy of the mathematical model generally assumed by the designer in order to use it in any further investigation especially the evaluation of existing buildings.

Reinforced concrete beam-column joints (BCJs) are commonly used in structures such as parking garages, multi-storey industrial buildings and road overpasses, which might be exposed to extreme weathering conditions and the application of de-icing salts. The use of the non-corrodible fiber-reinforced polymer (FRP) reinforcing bars in such structures is beneficial to overcome the steel-corrosion problems. However, FRP materials exhibit linear-elastic stress-strain characteristics up to failure, which raises concerns on their performance in BCJs where energy dissipation, through plastic behaviour, is required. The objective of this research project is to assess the seismic behaviour of concrete BCJs reinforced with FRP bars and stirrups. An experimental program was conducted at the University of Manitoba to participate in achieving this objective. Eight full-scale exterior T-shaped BCJs prototypes were constructed and tested under simulated seismic load conditions. The longitudinal and transversal reinforcement types and ratios for the beam and the columns were the main investigated parameters. The experimental results showed that the GFRP reinforced joints can successfully sustain a 4.0% drift ratio without any significant residual deformation. This indicates the feasibility of using GFRP bars and stirrups as reinforcement in the BCJs subjected to seismic-type loading. It was also concluded that, increasing the beam reinforcement ratio, while satisfying the strong column-weak beam concept, can enhance the ability of the joint to dissipate seismic energy. An analytical investigation was conducted through constructing a finite element model using ANSYS-software. The model was verified against the experimental results in this research. Then, a parametric study was performed on number of different parameters known to affect such joints including column axial load, concrete compressive strength, flexural strength ratio and joint transverse reinforcement. It was concluded that 70% of the column axial load capacity can be recommended as an upper limit to the applied axial loads on the column to avoid damage occurrence within the joint. It was also concluded that a minimum flexural strength ratio of 1.50 is recommended to ensure the strong-column weak-beam mechanism. In addition, a minimum joint transverse reinforcement ratio of 0.60% is recommended to insure that the failure will not occur in the joint zone.