Research

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.

OBJECTIVES

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:

  1. 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.
  2. 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.
  3. 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.

Testing Program

Construct and Test 4 one-third  scale model of a prototype:

T1 – Banded-Uniform tendon arrangement with conventional reinforcement

T2 – Banded-Uniform tendon arrangement with steel fibers                                                     ==========⇒

T3 – Banded-Banded tendon arrangement with conventional reinforcement

T4 – Banded-Banded tendon arrangement with steel fibers

Loading System

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)

A two-way post-tensioned flat plate is generally and typically  used as the floor system in high-rise, residential and office space building