No abstract

No abstract

Past researches showed that the energy dissipation capacity of the wide beam-column joints was not sufficient. So, two full-scale reinforced concrete interior wide beam-column joints were tested under quasi-static cyclic loads and the performance of the specimens was studied experimentally and numerically. Effect of using wide beams in two directions was investigated and it became clear that the longitudinal reinforcement of transverse wide beam had significant effect on the seismic behavior of the joints. Flexural hinging mechanism in the wide beams occurred instead of torsion brittle mode of failure. Effect of eccentric beams on joints is one of the areas needing research in ACI 352R-02. In the numerical study, it was seen that damage of the joints was concentrated to one side of the joints that the beams shifted to. Besides, concrete grade did not have much effect on behavior of the joint.

Limestone has been commonly used in concrete for several decades. Moreover, calcium carbonate was used as a portion of cement content. Therefore cuttlebone powder, which is composed of a naturally occurring crystal form of calcium carbonate named aragonite, was used in concrete as a substitution of a portion of cement content in this research program for the first time. It led to the production of green concrete which is a type of concrete causes less harm to environment. 3, 5 and 7 percent of cement were substituted with cuttlebone powder. For this purpose, 4 concrete mix designs included 36 cubes, 4 cylinders and 4 prisms were casted. Results showed that weight of the specimens with cuttlebone powder was lower than control specimen. Moreover, by adding cuttlebone powder to concrete, slump increased. Although compressive and tensile strengths of the specimens with cuttlebone powder were lower than control specimen, but the specimen with 3% cuttlebone powder had adequate strength. Besides, three-point flexural strength of the concrete with 3% cuttlebone powder was higher than control specimen. It seems that by reducing water content of the specimen with cuttlebone powder to have similar slump to the control specimen, better performance of concrete can be achieved. So, this natural material can be used instead of a portion of cement to produce green concrete.

SUMMARYPerformance of beam-column joints at roof level is one of the areas needing research in ACI 352R-02. Thus, behavior of roof exterior beam-column joints was evaluated by testing two half-scale roof wide and conventional beam-column joints effectively confined on three vertical faces under lateral quasistatic cyclic loading. Both of the specimens had conventional transverse beams. They were designed in accordance with ACI 318-11 and ACI 352R-02 provisions. It became clear by the tests that roof exterior wide beam-column joint was more ductile compared with roof exterior conventional beam-column joint. But there was not considerable difference between strength and energy dissipation capacity of the specimens. Moreover, joint shear strength was sufficient in wide beam-column joint. Therefore, joint shear requirements can be relaxed for roof exterior wide beam-column connection.