THE CONCRETE BRIDGE MAGAZINE

WINTER 2016

ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.

Issue link: http://www.aspiremagazinebyengineers.com/i/622975

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A PROFESSOR'S PERSPECTIVE EMBRACING CHANGE Innovate or live in the past? by Dr. Oguzhan Bayrak, University of Texas at Austin As human beings, certainly as structural engineers, most of us are change averse. We may have all said “if it ain’t broke, don’t fix it” or “this appears to be a solution in search of a problem” at some point in time in our structural engineering careers. Even if we may not have said it, we certainly heard others say it in our workplace, committee meetings, conferences, construction sites, and fabrication plants. Yet, there have been signi ficant innovations in designing and constructing concrete bridges over the years. The decision of what change to embrace is a complex process, and one that can be emotional rather than rational. In this article, I will share some of my thoughts on embracing change. Like most things in life, embracing change becomes easier if it can be put into its full context. That is to say, it is always important to understand the technical, financial, fabrication, and construction benefits of a solution as we work on a problem. Often, the involvement of the appropriate representives from industry, design, construction, and fabrication professionals may help define the problem, and the potential benefits of any generated solutions. To illustrate this process, I will use two research projects1-4 in which the University of Texas researchers studied the feasibility of increasing the allowable compressive stresses at prestress transfer. This value has remained unchanged since prestressed concrete was introduced in the American Association of State Highway Officials (AASHO) Standard Specifications for Highway Bridges in 1961. Before getting into technical details, it is important to note that the research projects that are used as an example benefited from the participation of engineers from the Texas Department of Transportation’s (TxDOT’s) bridge and construction divisions, as well as the precast concrete fabrication plants in Texas. This participation helped provide context to the problem. Let’s take a look at that context. From the beam fabrication standpoint, an increase in allowable compressive stresses from 0.60fci’ can reduce the cementitious material content in the concrete, the cycle time in precast concrete fabrication plants, and external curing costs. From the structural design perspective, an increase in this limit can increase the span capability of a given prestressed concrete section by allowing the use of a larger number of strands. Finally, an increase in this compressive stress limit may result in a reduction of the number of debonded or harped strands, and therefore may simplify design and fabrication of a prestressed concrete beam. The interplay between the fabrication and design benefits can be complex and it is not possible to invoke all of the aforementioned benefits simultaneously. Having understood all of the aforementioned benefits, the University of Texas researchers considered the downside of increasing the allowable compressive stress at prestress transfer.

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