Experimental study and calculation of confinement relationships for prestressed steel tube-confined compressed concrete stub columns

The current paper aims to present the results of an experimental investigation into the compressive strength of pre-stressed steel tube-confined compressed concrete (PSTC) stub columns. Here, to prestress the confined concrete, an innovative technique is utilized, in which the fresh concrete is subjected to compression while the steel tube is simultaneously preten-sioned laterally by applying external pressure to the fresh concrete. A total of 135 confined specimens were tested under axial compressive loading to determine the confinement strength of the specimens. Moreover, new confinement relationships for the load-carrying capacity of the PSTC columns were proposed in terms of the prestressing ratio ( r P ), reference concrete strength ( c f), and tube outer diameter to wall thickness ratio ( / Dt ). Finally, a parametric study was conducted to evaluate the effect that the parameters r P, c f , and / Dt have on the compressive strength of the prestressed confined concrete. The results indi-cate that the confined concrete prestressed by the present technique demonstrates significantly enhanced load-carrying capacity; however, increasing the prestressing level slightly affects it

The effect of foeniculum vulgare essence on production performance, egg quality and reproductive parameters of laying hens

An experiment was conducted to evaluate the effect of fennel essence on performance, egg quality and ovarian morphology of commercial laying eggs for ten weeks. In this experiment, one hundred and forty 30-wk-old commercial egg laying type Hy-Line (W36) were randomly assigned into 4 treatments with 5 replicates and 8 birds per each. Treatments were a control (0.0% essence) and diets containing 200, 400 and 600 ppm fennel essence. Performance parameters include egg weight and egg production was recorded daily and feed intake, FCR and egg quality parameters were measured weekly. At the end of the experiment, 2 birds of each replicate was randomly selected and slaughtered for analysis of ovarian morphology. Different levels of fennel essence no significant effect on egg production. Different levels of fennel essence no significant effect on egg production. Levels of 200 and 400 ppm of fennel essence showed a significant increase in egg weight. Levels of fennel essence had no significant effect on feed intake and FCR but it caused significant increase in yolk color and had significant effect on the properties of egg shell. Levels of essence had no significant effect on the relative weight of the ovary, oviduct and stroma but 200 ppm of fennel essence had significant effect on weight of large yellow follicles. The results showed that the addition of fennel essence improved egg weight, egg shell and yolk color and had a significant effect on the large yellow follicles