My Ph.D. research topic is focused on “Performance and Strength of of Conventional and Fiber Reinforced Two-way Post-tensioned Flat Plate or Slab”. Specifically we are looking at how to improve the performance of a post-tensioned flat plate with fiber and the performance of a banded-banded tendon arrangement system.
Post-tensioning is the process of producing prestressed concrete by applying internal forces in concrete after the concrete has been placed to counteract the effect of the self-weight and reduce flexural cracking when the structure is put to use. With the increasing need for commercial, high rise and residential building developments, post-tensioned flat plate has been the preferred choice for the floor systems because of its numerous advantages such as better efficiency, reduced slab self-weight, as well as crack and deflection control compared to a conventional reinforced concrete slab.
The objective of this research is to perform tests to gather data to provide justification for similar provisions in the ACI code which would allow designers/engineers to take advantage of steel fibers in the design of two-way post-tensioned flat plates. The key provisions which will be the focus of this research are as follows:
- In the current ACI Code, two-way flat plates must be designed as Class U prestressed concrete, with a maximum allowable tensile stress of . It is possible that with the inclusion of steel fibers this maximum could be increased to or higher.
- Currently minimum bonded reinforcing is required in positive moment regions of two-way flat plates if the maximum tensile stress in the slab exceeds . It is also possible that this limit can be increased for slabs with steel fibers.
- Minimum bonded reinforcement is also required in negative moment regions, where the required minimum is 0.00075 times the cross-sectional area of the beam-slab strip along the column line. This requirement might also be relaxed with the addition of steel fibers.
A secondary objective is to perform tests to investigate the strength and behavior of two-way flat plates with steel fiber reinforced concrete and a banded-banded tendon arrangement.
Construct and Test 4 one-third scale model of a prototype:
T2 – Banded-Uniform tendon arrangement with steel fibers ==========⇒
T3 – Banded-Banded tendon arrangement with conventional reinforcement
T4 – Banded-Banded tendon arrangement with steel fibers
All specimen will be loaded with a tension whiffle tree, this loading system applies 16 point load on each bay, this simulates a uniformly distributed load.
schematics of whiffle tree loading system Test Slab and whiffle tree with dead load compensation blocks
Typical Testing Day
Experimental vs Analytical (Ram Concept)
I am also some finite element analysis in Ram Concept to compare experimental data to analytical data.
Application of 2-way PT Floor System (Economical and Efficient)