FALL 2018

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.

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P E R S P E C T I V E 10 | ASPIRE Fall 2018 Benefits of the FHWA-NHI Strut-and-Tie Modeling Workshop An Attendee's Perspective To meet the current and future needs of our ever-changing society, engineers must keep their skills and knowledge up to date. Such discipline is required of new graduates and more-experienced engineers alike. Even if you are fully qualified, it is essential that you keep abreast of changes in the engineering profession. Continuing education courses can strengthen and broaden your knowledge base, and they will help you master needed skills at any stage of your career. Continuing education is also a requirement of licensure in most states. We can, of course, take webinars and online courses to learn about new bridge construction practices a n d i m p r o v e o u r b r i d g e d e s i g n skills. However, when I participated i n t h e " F H WA - N H I S t r u t - a n d - T i e Modeling (STM) Workshop" at the 2018 PCI Convention and National Bridge Conference in Denver, Colo., I was reminded of the unique value o f c o l l a b o r a t i v e a n d i n t e r a c t i v e education—there is nothing quite like being in the room with industry authorities and informed colleagues. STM has long been established as the preferred analysis method for deep beams and disturbed regions in concrete structures. STM is appropriate for analysis and design of bridge elements such as beam ends, diaphragms, corbels, beam ledges, deep beams, and pile caps. D e s p i t e t h e i m p o r t a n c e o f S T M , introductory concrete design courses typically do not cover the topic, and many design engineers do not feel confident about their understanding and use of the method, especially if they have been using a traditional sectional analysis requiring a two-step design process—one for flexure and one for shear. With the American Association of State Highway and Transportation Officials' (AASHTO's) recent adoption of new STM provisions in Section 5 of the AASHTO LRFD Bridge Design Specifications, 1 engineers must clearly understand and be able to apply the concepts and details of STM. T h e S T M w o r k s h o p I a t t e n d e d was run by the Federal Highway Administration (FHWA) and National Highway Institute (NHI) and geared toward bridge engineers at all levels of STM experience, from beginner to advanced. When I attended it, I was not a novice in STM. I was first introduced to the method as a PhD student at the University of Minnesota nearly 30 years ago, thanks to Professor Cathy French and her progressive technical course content, and I have since included a few lectures and homework to introduce STM to my own students in a graduate-level bridge design course. Therefore, for me, the workshop offered an excellent opportunity to sharpen my STM skills and gain some practical experience. The workshop was also well suited for introducing students to STM, especially when curriculum requirements and other course content limit the classroom time available for some technical topics. In the workshop, industry experts presented an in-depth introduction to STM fundamentals and then guided attendees through simple to advanced STM scenarios commonly seen in bridge engineering. Attendees actively participated, defining truss systems and evaluating designs. The following are critical points from the workshop to keep in mind when working with STM: by Dr. Tess Ahlborn, Michigan Technological University An example of efficient and inefficient strut-and-tie models. All Figures: Federal Highway Administration.

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