M.Naghipour - Associate professor, Department of civil engineering, Mazandaran University, Babol, Iran
M.Mehrzadi - Msc. student of civil engineering, Mazandaran University, Babol, Iran

Analytical and experimental investigation into dynamic properties of extra lightweight concrete sandwich beams reinforced with various lay ups of carbon reinforced epoxy polymer composites (CFRP) are discussed. The lightweight concrete used in the core of the sandwich beams was made up of extra lightweight aggregate, Lica. The density of concrete was half of ordinary concrete and it's compressive strength was about 100 Kg/cm2. Two extra lightweight unreinforced (control) beams and six extra lightweight sandwich beams with various lay ups of CFRP were clamped in one end and tested under an impact load. The dimension of the beams without considering any reinforcement were 20cm x 10cm x 1.4m. The dimensions were selected to ensure that the effect of shear during the bending test would be minimized. Three other beams, made up of ordinary concrete reinforced with steel bars, were tested in the same conditions. For measuring the damping capacity of sandwich beams three methods, Logarithmic Decrement Analysis (LDA), Hilbert Transform Analysis (HTA) and Moving Block Analysis (MBA) were applied. The first two methods are in time domain and the last one is in frequency domain. A comparison between the damping capacity of beams obtained from all the methods, shows that the damping capacity of the extra lightweight concrete decreases by adding the composite reinforced layers on the upper and lower sides of the beams and becomes most similar to the damping of the ordinary beams. Also the results show that extra lightweight concrete beams’ stiffness increases by adding the composite reinforced layer on their both sides and becomes similar to the ordinary beams.

Extra lightweight Concrete, CFRP, Damping, Sandwich Beams, Clamped Beams