The present study, the effect of changes that developed in concrete structures with time is presented. Two way slab investigated experimentally by [1]was analyzed using finite element method by ANSYS commercial program. Many parameters studied such as length to thickness ratio, reinforcement ratio and ultimate load ratio. The slab with dimension (2360*2360*63) mm and reinforced with different types of materials such as steel bars ,GFRP and CFRP (fiber reinforced polymer) bars . The results show that the strain increase gradually with time after apply the load. It can see that the strain in steel model increase with ratio of 19.98% when the load increase from 75% to 90%,and decrease with ratio 50% when the load decrease from 75% to 50% .That is, the change by increasing the strain is less and slower than the change by decreasing the strain, since the strain when dropping the load is less than the strain when lifting the load, because the structure has not undergone and its stiffness is still high and it is trying to recover its original shape. It increases significantly at the beginning, and then the difference decreases or stabilizes approximately after 330 days.
The structural behavior of composite steel concrete beams with long term deflection was investigated, taking in considerations several variables including degree of shear connectors 50%, 75%, 100%, and type of connectors including headed and hooked studs smooth or deformed. Five composite steel-concrete beams were tested each consist of steel section W12x35 and 300x100 concrete slabs. The composite beams were tested under uniformly distributed loads for different time interval up to 180 days. The results showed that the degree of interaction have significant influence on the long- term behavior of the composite steel concrete beam . When the degree of interaction decreased from 100% to 75% then to 50% the maximum long-term mid span deflection increased about 35.1% and 65.9% respectively at 180 days after loading. Also, the end slip increased about 67.5% and 112.4% respectively at 180 days after loading. The results showed that the type of the used shear connectors has slight influence on the long-term behavior of the composite steel concrete beams. For certain degree of interaction (75%)with using headed and hooked studs smooth or deformed the maximum long-term mid span deflection decreased about 7.1% and 11.7%at 180 days after loading, and the end slip decreased about 4.8% and 12.5% at 180 days after loading.
A BSTRACT: Leaching effects on permeability and compressibility characteristics of undisturbed sandy gypseous soil were investigated in this study. Time, stress level, strain, leachate condition and flow velocity were considered. The loading, leaching and permeability measurements were carried out utilizing the constant head pereameter with special modifications. Test results show that salt leaching and thereby leaching strain is a time dependent process. Also as leaching strain continued coefficient of permeability decreases.