Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Civil Engineering

Committee Chair

Ashraf Z Al-Hamdan

Committee Member

Michael D. Anderson

Committee Member

Hongyu Zhou

Committee Member

Q.H.Ken Zuo

Committee Member

Nasim Uddin


Cement composites., Composite materials., Reinforced concrete.


Rehabilitation of structures has become the main emphasis of many types of research in the past few decades due to the huge cost of the reconstruction. In order to strengthen of the flexural behavior of reinforced concrete beams, typically fiber reinforced polymer (FRP) is bounded to tension sides of structural elements. The external application of polyurea coating system is a new approach which improves the flexural behavior of RC beams rather that environmental protection. This research has been conducted to evaluate fatigue and monotonic behavior of RC beams strengthened with a polyurea coating system. Ease of application and multi-hazard benefits of polyurea has made it useful in retrofit–repair situations. Rather than blast or impact mitigation, polyurea has the capability of flexural and shear reinforcement for structural members. In the first phase of this research, the analytical model was developed based on cyclic dependent properties of concrete to predict the maximum deflection of strengthened beams under cyclic service loads. In order to validate the model, numbers of large size reinforced concrete beams were fabricated and externally strengthened in two levels of polyurea thickness. Beams were tested under four-point monotonic and fatigue loading. The relationship between deflection, coating thickness and the number of cycles was studied and analyzed. Results indicated that application of polyurea improves the flexural capacity as well as ductility of RC beams under both monotonic and cyclic loading. In addition, the elastic–viscoelastic correspondence principle was used to evaluate the stress-strain behavior of polyurea coating system as a time-dependent component. The correspondence principle represented an acceptable model for damage growth and fracture healing of polyurea under complex cyclic loading. Moreover, based on experimental test results, fatigue life models were proposed for both strengthened and unstrengthened beams according to linear regression and Tikhonov-Morozov regularization methods. The results have shown that a regularization method is an effective way to reduce the influence of measurement noise without disturbing the structure of fatigue life distribution.



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