IIS in the News

Three from IIS will present at ASCE Structural Engineering Institute’s Structures Congress 2018

Dr. Nathan Dubbs, Dr. Kirk Grimmelsman and Tom Golecki will present technical programs at Structures Congress 2018 being held in Fort Worth, TX from April 19-21, 2018.

Structures Congress is a technical conference put on yearly by the ASCE’s Structural Engineering Institute (SEI).  SEI, established in 1996, is a vibrant community of more than 30,000 structural engineers within the American Society of Civil Engineers (ASCE) that involves all facets of the structural engineering community including practicing engineers, students, research scientists, academics, technologists, material suppliers, contractors, and owners. SEI is committed to advancing and serving the structural engineering profession while influencing change on broader issues that shape the entire civil engineering community. [1]

Presentations from Intelligent Infrastructure Systems’ staff include the following:

  1. Expanding the Case for Structural Health Monitoring: A Focus on its Role in Maintenance & Operations and Asset Management Systems (Dubbs)
  2. Structural Health Monitoring for Real Time Assessment and Reporting of a Long Span Vertical Lift Bridge State of Balance (Dubbs)
  3. Performance Assessment of a Water Tank (Grimmelsman)
  4. Benefits and Challenges of Automating Refined Load Ratings for Girder Bridges (Golecki)

 

Thursday, April 19, 2018 (9:30 – 10:30 AM)
Session: BR5 – Improving Bridge Performance and Longevity Through Bridge Management

Dr. Dubbs will present Expanding the Case for Structural Health Monitoring: A Focus on its Role in Maintenance & Operations and Asset Management Systems.  During this presentation, Dr. Dubbs will discuss how Structural Health Monitoring (SHM) can inform not only traditional structural health metrics but also operations and maintenance metrics.  A case study will be presented to demonstrate how an in-service SHM system has been integrated into a bridge agency’s asset management software platform.

The concept of Structural Health Monitoring has become synonymous with strain gages, displacement transducers, and accelerometers, among other sensors, and the complex and extensive set of data that most think one needs a PhD to understand. The challenge of extracting actionable information from complex structural response data is certainly not trivial and is an ongoing pursuit in the SHM community. Traditional SHM metrics include load distribution, degree of composite action, modal parameters, movement system performance, among many others.

However, this view of ‘structural health’ has been changing recently due primarily to a shift in how the end-users of SHM systems envision how it will provide value to their duty to maintain operable structures. Specifically, bridge managers are looking to SHM to provide value to Operations and Maintenance Managers and to integrate within agency asset management systems. This expansion is representative of cases where new technology is introduced to a field: the technology experts tend to believe they have identified the most important use cases for the end-users while the end-users don’t share that vision and are left wondering how the technology is supposed to integrate within their workflow and provide a return on investment. Over the past few years, it has become clear that bridge managers have seen the value in SHM, however they simply need better information that can provide value on a daily basis – not only when their structure is subjected to an extreme load or hazard.

 

Session 338156 – The Versatility of Structural Monitoring

Dr. Dubbs will present Structural Health Monitoring for Real Time Assessment and Reporting of a Long Span Vertical Lift Bridge State of Balance. This presentation will discuss an application where a Structural Health Monitoring (SHM) system was designed and deployed on an 85-year-old, 540-foot vertical lift span to capture the continuous system balance at all four corners of the truss when the span was seated and provide real time assessment of the state of balance of the bridge, and its distribution, to key personnel. A framework will also be presented for determining the state of balance for movable structures in general, as well as a discussion on lessons learned and critical challenges faced.

 

Friday, April 20, 2018 (11:00 – 12:30 PM)
Session 340652 – Advancing Smart Cities through Structural Monitoring & Identification

Dr. Grimmelsman’s presentation – Performance Assessment of a Water Tank summarizes the application of the structural identification framework to an elevated water tank structure to evaluate its performance. Structural identification is a robust, six-step framework that is often used to quantitatively characterize in-service constructed systems. The characterization of the structure is achieved through reconciliation of experimental testing results with physics-based, analytical model predictions. The resulting characterization can serve many different objectives, but a common use is to evaluate performance problems. The structure in question was retrofitted with cellular antennas and had experienced fatigue cracking, and the owner wished to identify the likely cause of the performance problem. The water tank was instrumented with accelerometers and a weather station and monitored at different wind speeds and for various controlled and uncontrolled operating conditions. The effective lateral stiffness of the structure was extracted using the measurement results and a simple physics-based analysis and used with other known structural characteristics to evaluate potential causes for the fatigue-inducing lateral displacements of the water tank. Wind pressure loading, vortex excitation, sloshing and second order effects (P-Delta) were all evaluated as potential causes. Structural identification revealed that second order effects were the most likely cause of the fatigue inducing lateral displacements.

Those attending this presentation will learn how to apply the structural identification framework to elevated water tanks, how the results of structural identification can be used to evaluate and assess specific performance problems, and practical monitoring system design considerations, possible improvements to the monitoring approach that was employed, and other potential applications for the implemented approach.

 

Friday, April 20, 2018 (11:00 – 12:30 PM)
Session 340652 – Advancing Smart Cities through Structural Monitoring & Identification

Mr. Golecki will present Benefits and Challenges of Automating Refined Load Ratings for Girder Bridges. Mr. Golecki will discuss how current industry trends in bridge load ratings acknowledge both the benefits of refined ratings and the added expense. Refined ratings are used sparingly in part because of the added level of resources needed produce and evaluate analytical models. This additional effort consists of critical broad engineering decisions such as modeling approach and a substantial amount of tedious and error prone tasks of manipulating a finite element analysis (FEA) program via a Graphical User Interface (GUI) to build and analyze a model. By separating the broad engineering decisions and passing them as input into a series of automated algorithms that carry out model building, analysis and results extraction, the refined rating process can be made much more efficient and consistent.

The biggest challenge of automating this process is balancing the flexibility and robustness of the process with the amount of engineering overhead required to develop the necessary input. An automated refined load rating needs to accommodate bridge configurations that fall outside the bounds of applicability of distribution factors used in approximate methods. As an example, these distribution factors aren’t applicable to bridges with features such as variable skews or curvature, which present additional challenges in model generation as well. Once established, an automated process enables a load rating engineer to spend their time studying structural behavior and the effect of modeling decisions or rehabilitation strategies rather than manipulating a GUI. Automation also makes a process completely repeatable and more transparent than traditional refined analysis. This paper discusses the refined rating process, as well as the challenges and benefits of automating this process for multi-girder bridges.

More information about Structures Congress 2018 can be found here: http://www.structurescongress.org/