Islamic University of Lebanonrighttop00Faculty of EngineeringDepartment of Civil Fourth Year TERM PAPERSTitle :Prestress and Precast ConcreteRepresent to: DR.Mahmoud FakihRepresent by: Zainab Ali Kain Zahraa Ahmad AounMohammed Ali BerroDana Mohammed Houmany June 2018 Prestressing Foundations Civil Engineering DepartmentIslamic University of LebanonAbstractPrestressing use has been take the majority of crafted by chunks and shafts those days however establishments have just seldom been prestressed. The point of this report is to demonstrate the accessible methods and criteria for understanding and outlining Posttensioned Foundations. Indeed, with legitimate application, the notable preferences of prestressing can likewise be abused in establishment building.
Introduction310055940245810039714371560244Figure 1: Effect of prestressing on soil pressure distribution: (a) Prestressed continuous beam on elastic00Figure 1: Effect of prestressing on soil pressure distribution: (a) Prestressed continuous beam on elasticThe primary motivation behind establishment security is to exchange connected powers and horizontal powers from the structure to the dirt with no twisting in establishment or the structure and without expanding of soil bearing limit. Numerous individuals ask their selves: Why prestressing the establishment? In meaning of prestressing, it offers the likelihood of presenting a positive arrangement of dynamic powers following up on the solid, dock powers, deviation powers and grating powers. The transverse segments of the jetty powers and the deviation powers, permit a heap adjusting, causing a dirt weight appropriation and an expanded shear obstruction. Fig. 1 represents the impact of prestressing on the dirt weight circulation.
The prestressing power, P, is picked to adjust either half or 100% of F. Figures 1b, 1c and 1d demonstrate the dirt powers because of F, P and the joined activity of F and P individually. As Fig. 1d illustrates, a more uniform soil constrain conveyance with a comparing lessening of the most extreme soil power can be accomplished by prestressing. In addition, the ligament profile can be chosen so that for a specific stacking case.
Notwithstanding that, there’s impact of prestressing ligaments on the punching opposition of an establishment piece. The punching obstruction is expanded by the entirety of the part. 93139842325200Figure 2: Effect of prestressing on punching resistance2.BackgroundPost-Tensioned concrete was developed by Eugene Freyssinet.
He notice that the strength increase when the concrete is under compression.3.Subject•Amount of Prestressing: Keeping in mind the end goal to enhance the splitting conduct, a specific least measure of non-prestressed support is ordinarily put at the surfaces of prestressed establishments.
Certain base fortification proportions are in the request of 0.1 %. The benefits of prestressing are most articulated for successful prestress esteems in the range from 0.
25 to 2.0 N/mm2. For most applications, prestress qualities will go between the nearer furthest reaches of 0.75 and 1.5 N/mm2.
•Design Criteria: Here we will demonstrate a little piece of the plan,,, The outline of a prestressed establishment needs to think about the impacts of both connected loads and forced misshapenings. Volumetric changes because of shrinkage, temperature, prestressing and crawl of the solid are controlled both by subgrade grating and by limiting components underneath or more the establishment, for example, heaps. Notwithstanding that, the establishment applies limiting impacts on the structure. Accordingly the originator by and large faces an extremely troublesome issue of common controlling activities.
Among different variables, it relies upon the presentation conditions and the thicknesses of the distinctive individuals. Then again, an establishment of a building will encounter just little temperature varieties after the development time frame. Moreover, soil dampness or ground water will lessen shrinkage of the solid.
The strain circulation through the thickness of an establishment chunk is non-direct when all is said in done. General non-straight strain profiles can be part up into a consistent, a direct and a non-straight segment. Besides, there’s impact of subgrade rubbing on the successful prestress in an establishment piece. Mulling over activities because of other volumetric changes can be likewise treated. The chunk strip is prestressed from the two closures with the jacking power P j. As we complete from the plan, the planner goes to check at move in which outline quality of the solid isn’t yet come to while the gravity loads from the superstructure don’t yet adjust the deviation powers of the ligaments.
The relating variety of the aggregate minutes is given in Fig. 31065481center0021539207620Figure 3: Flexural effects of prestressing in continuous foundation: (a) System and notation; (b)00Figure 3: Flexural effects of prestressing in continuous foundation: (a) System and notation; (b)In the second stage, planner swings to check at Service Conditions as it incorporates examinations of processed worries in the solid and in the support with reasonable cutoff points indicated in codes. Be that as it may, this check can’t cover the impacts of splitting so it’s smarter to play out a Ultimate Check instead of checks under administration conditions if the structure is relied upon to break.
right64579500At last, check at Ultimate Stage in which the plan of the establishment doesn’t confront any extraordinary troubles. So the plan construct absolutely in light of the impact of burdens or any pressure state may the balance be formed to.4. ConclusionsAll in all, consequently, the outline will have two targets. Initially, it will endeavor to give the structure adequate malleability to make it obtuse to forced distortions. Second, the auxiliary measurements and subtle elements will be resolved based on a harmony examination to oppose the connected burdens.5.References1.
https://www.vsl.net/sites/default/files/vsl/datasheet/PT_Foundations.pdf
