Civil Engineering Department award a PhD

Civil Engineering Department at UOT awarded a PhD degree in discipline of structural engineering to the student (Mohamed Ahmed Hadi) on 12/15/2021 for his thesis tagged:

Behavior of Recycled Aggregate Reinforced Concrete Box Girder 

The research dealt with work on the behavior of the reinforced concrete box joists subjected to bending and shearing and the container for recycled aggregates, steel fibers and internal reinforcement barriers.

    The practice part consisted of casting and checking twenty-two reinforced box joists under double-loading point check to failure. All box joists were of the same cross section. Considered variables include: RA of (50, 75, and 100%) as a substitute for natural aggregate (NA), steel fibers (Vf, 0.5, 1.0, 2.0%) (By volume), number of baffles Internal reinforcement (two and three). In practice, it was found that the shear tributaries are affected by the ratio of the replacement of the (RA) more than the flexion tributaries. It was also found that to recover the capacity of the box girders (as in the control girders (and when using 100% RA, it is better to use 1.0% steel fibers. From the test results; for box girders, the best case is to use) 50% RA with 1.0 Vf). Whereas, for shear girders, the best case is to use (100% RA with % 2.0 Vf). It was also found that when (two and three) internal stiffeners were used in the middle third of the box joist, the flexural joist was more affected than the joist. Shear. Finally, finite element analysis, using ABAQUS software, was used to model the behavior of box joists formed from concrete containing recycled aggregates. The theoretical (analytical) results showed an acceptable agreement with the experimental results, including the first crack, maximum load and cracking pattern.

A theoretical study was also conducted using digital models to find out the effect of using different opening shapes (circular and rectangular) and sizes (Max, 30% and 20%) of the internal bulkhead area. The results showed that: Flexion tributaries are affected more by the internal stiffener opening (sizes and shapes) than Shear joists. A circular opening with a size of 20% of the area of ​​​​the inner gusset can be used instead of the steel gusset for flexural and shear joists, in case service requirements are needed. Also, to see the effect of replacing the rectangular cross-section of the box joist with a trapezoid on the first crack load and maximum load and Precipitation for reinforced concrete box joists Theoretical (analytical) results showed that: Rectangular joists have a higher maximum capacity than trapezoidal box joists.

The discussion committee consisted of: -

• Dr. Muhammad Jaafar Hammoud / the head.
• Dr. Maan Salman Hassan / member.
• Prof. Dr. Walid Awad / member.
• Prof. Dr. Ahmed Abdullah Mansour / member.
• Prof. Dr. Qais Abdul Majeed Hassan / member.
• Prof. Dr. Ayad Kadhim Saihoud / supervisor.
• Prof. Dr. Ali Sadiq / supervisor.