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In order to investigate the flexural behaviors of RC beams after freeze-thaw cycles, compressive strength test of concrete cubes after 0, 50, 100, 125 freeze-thaw cycles were made, and static flexural experiment of 48 RC beams after 0, 50, 100, 125 freeze-thaw cycles were made. The relationships of relative compressive strength, mass loss rate, relative dynamic elastic modulus and numbers of freeze-thaw cycles were analyzed. The influences of different numbers of freeze-thaw cycles on the flexural behaviors of RC beams with different concrete grades were studied. The results show that concrete cubes’ mass, relative dynamic elastic modulus and compressive strength decrease with the increasing of freeze-thaw cycles, and high-strength grade concrete could slow down the damage caused by freeze-thaw cycles. Experimental values of test beams stiffness under short-term load were smaller than theory value. Some under-reinforced RC beams occurs over-reinforced failure mode after freeze-thaw cycles. Boundary reinforcement ratio of RC beams after certain numbers of freeze-thaw cycles was derived and its correctness was verified by experiment. Current code for design of concrete structures about crack load and ultimate load are still suitable for RC beams after freeze-thaw cycles.

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To study seismic performance of concrete-encased composite columns with T-shaped steel cross-section, twelve half-scale columns were tested under quasi-stastic cyclic loading. The result indicates that concrete-encased composite columns with T-shaped steel section possess good seismic performance. The failure modes include bending failure, shear-bond failure, shear compression failure and shear-composition failure. Unsymmetrical phenomenon of positive and negative hysteresis loop was shown evidently. Span ratio has a great influence on failure mode. The ductility performance decreases with increasing of axial compression level. As stirrup ratio increases, ductility and bearing capacity of columns are improved greatly, and energy dissipation capacity after yielding is enhanced. Cross tie can enhance ultimate bearing capacity, and lower strength attenuation and stiffness degradation on the later loading stage

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In this paper, the scour hole dimensions around submerged and emerged spur dike in a 90o bend along with the mean and turbulent flowfield were investigated experimentally. Two types of re-circulating flow at the downstream of the spur dike and around the spur dike wing were observed. A direct relation between the estimated bed shear stress using TKE and the scour process prevails. More attentions is needed in estimating the bed shear stress using vertical velocity fluctuations. The scour hole dimensions increase by increasing the ratio of radius of channel bend to channel width , the Froude number of the spur dike, ratio of the length of spur dike to channel width and ratio of the approach mean flow velocity to the approach flow velocity at threshold condition. However, vice versa trends were observed by increasing ratio of the spur dike length to the median sediment size, ratio of the wing length of spur dike to the length of spur dike and the submergence ratio. A particular location of the spur dike in the sharp bend was specified beyond which the scour hole dimensions increase. The ratio of the spur dike length to the median sediment size has a secondary effect on the scour hole dimensions. New equations are proposed for prediction of the scour hole dimensions considering the submergence ratio along with other effective parameters.