UC Professor Awarded Second Fellow in Months

By: Liz Daubenmire

Bahram Shahrooz, PhD is named an American Society of Civil Engineering (ASCE) Fellow for keeping our bridges safe.

Being named a Fellow is among the highest of honors.  For Professor Bahram Shahrooz in the Department of Civil and Architectural Engineering and Construction Management (CAECM) at the University of Cincinnati, the recognition keeps coming.

In early April, Shahrooz was named the ASCE Structural Engineering Institute (SEI) Fellow for his work with fuses.  Professor Shahrooz did not deal with fuses you might blow by overloading an outlet.  Instead, he developed a fuse system relating to buildings’ structural properties that are designed to “fail” under seismic, or earthquake derived, forces. 

In a previous article, Shahrooz explains, “Being able to shape national building and bridge design codes plus publishing technical papers, which are routinely cited by researchers around the world, were instrumental in my election to become an SEI Fellow. Many countries use US building and bridge codes as the key component of their own codes, or use them verbatim.  Therefore, my research has also benefited engineers in other countries. I’ll continue to push the frontier of structural engineering through my research, and educate future faculty and engineers.”

Just a few months later, Shahrooz became another ASCE Fellow for his research and success in changing bridge code, a task not easily completed in today’s world of civil engineering. 

Composite Bridge Model

Composite Bridge Model

The UC professor worked in collaboration with Arthur Helmicki, PhD, Department of Electrical Engineering and Computing Systems (EECS), Victor Hunt, PhD, EECS, Michael Baseheart, PhD, Prof. Emeritus, CAECM, and Kent Harries, PhD, University of Pittsburgh in completing some revolutionary research related to the applications of fiber-reinforced polymer (FRP) composites in bridges. 

His first research examined composite bridge decks; an example of which is seen in figure 1. As Shahrooz explains, the top layer of the bridge is asphalt or concrete and the supporting hexagons, in this example, are made of a lighter, FRP composite (which is a plastic-like material).  The image featured is a cross section of the bridge, so that you are viewing it from the end, in the same direction as the cars are traveling.

While Professor Shahrooz and his team did not develop this bridge type, Shahrooz and his colleagues discovered some problematic areas through their research.

The first area of concern deals with the heating and cooling of the bridge.  The top pavement layer is exposed to sun, which causes it to heat and expand.  The lower portions of the bridge are shielded from the sun, allowing them to stay cool.  This is not something new and traditional concrete bridge decks go through the same thermal gradient.  However, the integrity of the connections between the various parts that make up an FRP bridge deck can be weakened unless they’re designed properly for thermal effects.  Prior to the research led by Shahrooz, the industry had dealt with smaller FRP bridge decks, and the designers had not fully appreciated temperature effects.  Shahrooz and his team conducted extensive field-testing and long-term monitoring on a bridge in Dayton, which at the time was the longest bridge in the U.S. with FRP composite bridge decks.  The seminal lessons learned from this project have helped the designers and manufacturers deal with composite bridge decks more effectively.

The second area of concern is the combined effect of UV light from the sun, freeze-thaw cycles, and deicing salt on the integrity of FRP composites used in new bridges or for strengthening of existing bridges.  In a pioneering research, Shahrooz and his colleagues performed an in-depth study of the synergistic effects of these factors.

Shahrooz and his colleagues have assembled their findings in a number of publications aimed at helping the engineering community.  The title of one his latest publications is, “Environmental Durability of Externally Bonded FRP Materials Intended for Repair of Concrete Structures”, which was cited “10 or 15 times” shortly after publication, according to Shahrooz.  This high rate of citation in a short amount of time is a testament of the depth and breadth of the practical data generated by Shahrooz and his team.

In addition to the much needed research on composite bridges, Professor Shahrooz also worked to advance reinforcement that is used in concrete structures with Richard Miller, PhD, CAECM, Kent Harries, PhD, University of Pittsburgh, and Henry Russell, PhD, Russell, Inc., Glenview, IL.

Concrete alone is weak in tension but combined with steel reinforcing bars, or rebar, the structure can stand up against large forces of all kinds.  Reinforcing bars are long rods of steel that are placed throughout the concrete, allowing it to bear significant loads. 

In the 50’s and 60’s reinforcing bars were designed to hold up to 50 thousand pounds per square inch, and more recently designers used 60 thousand pounds per square inch.  With advancements in the production of reinforcing bars, they now have the capacity to hold 100 to 120 thousand pounds per square inch.  These higher strengths allow the designer to use less reinforcing bars.   A lot of lower-strength reinforcing bars are often needed in some parts of beams and columns, meaning they have to be placed close together within the concrete.  This leads to congestion within the concrete, almost as if the concrete were fully saturated with little room between each overlaying rebar.

In order to reduce that congestion and spread the bars out, they must be made stronger.  While this solution seems somewhat intuitive, issues surrounding the design codes prevented the engineers from fixing the problem until now. 

Bridge Code Book

Bridge Design Code Book

Shahrooz and his team conducted in-depth research through lab data from the testing of actual-size bridge beams at the University of Cincinnati’s Large Scale Test Facility (UCLSTF) and computer simulations to ensure concrete would hold its integrity with fewer, yet stronger reinforcing bars.  After the data were collected and synthesized, the team was able to distill the information to a point where it could then be translated into code language. 

Once changes to the code are proposed and submitted for adoption, they must pass through a rigorous review process by a number of national committees.  This process is usually lengthy, and the suggested changes could be denied.  For Professor Shahrooz and his partners, the changes were accepted quickly, and in less than 2 years the research was incorporated into the new codes. 

Changing a design code is not that easy, it is said anyone who successfully alters the codes should consider it one of the main highlights, if not the main highlight, of his/her career success. 

Professor Bahram Shahrooz, PhD

Professor Bahram Shahrooz, PhD

Shahrooz expresses, “It feels good to have that impact.”

The bridge design code, seen in figure two, is several inches thick, proving the codes are heavily detailed.  A large portion of the pink pages indicate the changes Professor Shahrooz and his team have made. 

Despite his accomplishments, professor Shahrooz remains humble.  He has taken one of his advisors’ wisdom to heart and passes it on to his students to whom he always encourages to “produce something that people will use.”  He asks, “What’s the use if the community cannot use it?”

In collaboration with Dr. Herbert Bill, PhD, CAECM, professor Shahrooz’s latest research is in an innovative type of continuous transverse reinforcement (CTR) which simply wraps the reinforcing bars like a slinky rather than having them placed individually to secure each group of rebars.  Professor Shahrooz is currently working on incorporating this new system in the concrete building code.  Until then, Shahrooz explains that the code contains an important clause that allows designers and contractors to use technology outside the code as long as there has been a sufficient amount of data to prove its effectiveness.  That data from the University of Cincinnati will allow designers to use CTR, potentially making this research an important game changer in the world of civil engineering. 

Thanks to the work of Professor Shahrooz and his accomplished colleagues, the bridge and building code- referred to by many as the civil engineering “bibles”- will forever include the University of Cincinnati.