The performance of composite prestressed concrete beam topped with reinforced concrete flange structures in fire depends upon several factors, including the change in properties of the two different materials due to fire exposure and temperature distribution within the composition of the composite members of the structure. The present experimental work included casting of 12 identical simply supported prestressed concrete beams grouped into 3 categories, depending on the strength of the top reinforced concrete deck slab (20, 30, and 40 MPa). They were connected together by using shear connector reinforcements. To simulate the real practical fire disasters, 3 composite prestressed concrete beams from each group were exposed to high temperature flame of 300, 500, and 700°C, and the remaining beams were left without burning as reference specimens. Then, the burned beams were cooled gradually by leaving them at an ambient lab condition, after which the specimens were loaded until failure to study the effect of temperature on the residual beams serviceability, to determine the ultimate load-carrying capacity of each specimen in comparison with unburned reference beam, and to find the limit of the temperature for a full composite section to remain composite. It was found that the exposure to fire temperature increased the camber of composite beam at all periods of the burning and cooling cycle as well as the residual camber, along with reduction in beam stiffness and the modulus of elasticity of concrete in addition to decrease in the load-carrying capacity.
The present work presents a new experimental study of the enhancement of turbulent
convection heat transfer inside tubes for combined thermal and hydrodynamic entry length of one
popular “turbulator” (twisted tape with width slightly less than internal tube diameter) inserted for
fire tube boilers. Cylindrical combustion chamber was used to burn (1.6 to 7kg/h) fuel oil #2 to
deliver hot gases with ranges of Reynolds number (10500 to 21700), and (11400 to 24150) for both
empty and inserted tube respectively.A uniform wall temperature technique was used by keeping
approximately constant water temperature difference (25ºC) between inlet and exit cooling water in
parallel flow shell and tube heat exchanger. The test
Background: This in vitro study evaluated the fracture resistance of weakened endodontically treated premolars with class II MOD cavities restored with different composite restorations (Low-shrinkage Filtek P90, nanohybrid Filtek Z250 XT and SDR bulk fill). The type and mode of fracture were also assessed for all the experimental groups. Materials and Method: Fifty human adult maxillary premolar teeth were selected for this study. Standardized extensive class II MOD cavities with endodontic treatment were prepared for all teeth, except those that were saved as intact control. The teeth were divided into five groups of ten teeth each (n=10): (Group 1) intact control group, (Group 2) unrestored teeth with endodontic treatment, (Group 3) resto
... Show MoreIn this study, geopolymer mortar was designed in various experimental combinations employing 1% micro steel fibers and was subjected to different temperatures, according to the prior works of other researchers. The geopolymer mortar was developed using a variety of sustainable material proportions (fly ash and slag) to examine the influence of fibers on its strength. The fly ash weight percentage was 50%, 60%, and 70% by slag weight to study its effect on the geopolymer mortar's properties. The optimal ratio produced the most significant results when mixed at a 50:50 ratio of fly ash and slag with 1% micro steel fibers at curing temperature 240oC for 4 hours through two days. The compressive strength of the geopolymer mortar increas
... Show MoreExplanation of article events , or discribing it establish to anderstanding an phenomenon which its effects still clear in the art , surching like this may be very usful in the analysis of new art , which considering one of the most important turns in the history of art . and if we look to human body in the art as existenc in the art , from it’s begening to the modern age . so we can understand the meaning of this existence and it’s directins which cover all the worid and the lead us to thiories and suggestion’s help in understand to this direction and the effects between our arts and the external directions.
For the time being, the cold-formed sections are widely used due to their simple manufacturing and construction processes. To be feasible, the strength of cold-formed columns should be determined based on their post-buckling behavior. Post-buckling relations are cumbersome and need design aids similar to those of American Iron and Steel Institute (AISI) to be applicable. These design aids have been developed to sections and materials other than those available in the local market. Therefore, this paper tries to develop a general finite element model to simulate the postbuckling behavior of cold-formed steel columns. Shell element has been used to discretize the web, flanges, and lips of the column. A linear bucking analy
... Show MoreThe prostheses sockets use normally composite materials which means that their applications may be related with the human body. Therefore, it was very necessary to improve the mechanical properties of these materials. The prosthetic sockets are subjected to varying stresses in gait cycle scenario which may cause a fatigue damage. Therefore, it is necessary or this work to modify the fatigue behavior of the materials used for manufacturing the prostheses sockets. In this work, different Nano particle materials are used to modify the mechanical properties of the composite materials, and increase the fatigue strength. By using an experimental technique, the effect of using different volu
Renal transplantation is a principal treatment option for end-stage kidney failure. Bone loss and fracture are serious complication of kidney transplantation, associated with morbidity and mortality. The pathogenesis of post transplantation bone loss is multifactorial and complex
This study focuses on the slab-beam interaction in one-way systems. In the context of this study, slab-beam interaction means how beam deflection can affect moment distribution in one-way slabs. This interaction is usually neglected in the traditional approximate analysis that is adopted in engineering practice and design codes. Slab positive moments have been considered as indicators on the accuracy of approximate methods, as they overestimate negative moments while underestimating positive moments.
After proposing of effecting parameters in slab-beam interaction including of panel length and width, beam dimensions, and slab thickness, Buckingham’s theorem has been adopted to transform the dimensional-mo
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