Analysis and Comparative Study of Unbonded Post-tensioned Cast-In-Place Parking Floor on the Effects of Tendon Layout using Safe
Abstract
In recent years post-tensioned floors are commonly used for parking purposes in residential and commercial high rise buildings. This paper includes result on a study of un-bonded post tensioned cast-in-place parking floor subjected to various arrangements of tendon layout based on FEM analysis. Modelling and analysis of post-tensioned flat plate is done by using SAFE software. Equivalent loads based on cable profiles are applied to the flat plate according to the tendon layout. Design moments, service moments, hyper-static moments, short term deflection, long term deflection, and punching shear are compared for the various tendon layouts at service and ultimate limit state.
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Introduction
In recent days post-tensioned parking floor is common in residential and commercial high rise buildings. Usage of post tensioned floors provide beneficial advantages over reinforced concrete floors in terms of reduction in thickness of slab, construction speed, rapid fixing services and also offers superior structural performance and other advantages. Here we used load balancing techniques for the design of PT flat plate, and this method is mainly dependent on tendon arrangements. This paper shows the comparative study and behavior of PT flat plate by the effects of tendon layout at service and ultimate limit state.
Conclusion
Moment distributions across the slab panels may vary significantly between different tendon layouts, resulting in different signs at critical sections at service limit states.
Moment distributions across the slab panels are almost similar between different tendon layouts, at ultimate limit states.
Load carrying capacity of a case 1 FEM model is more than compare to case 2 and case 3 at service limit state.
Load carrying capacity of a case 2 FEM model is more than compare to case 1 and case 3 at ultimate limit state.
Load carrying capacity of a case 2 FEM model is more than compare to case 1 and case 3 to withstand hyper -static moments (secondary moments).
Total deflection including effect of temperature, creep and shrinkage, the deflection values are within the permissible limit for all the 3 cases. But, case 1 gives fewer values than compare to case 2 and case 3.
The punching shear capacity ratio values in case 3 are better than compare to case 1 and case 2, at some points it is exceeding than permissible limit at that point shear reinforcement is required.
Overall by seeing the results obtained from analysis, case 2 (distributed and distributed tendons) behaving good at ultimate limit state than case 2 and case 3. Here strength and serviceability considerably increased; hence I am concluding case 1 is better option for constructing un-bonded post-tensioned parking floor slabs.