Structural Capacity Analysis of Corroded Steel Girder Bridges

More than 9% of the bridges in the United States were labeled structurally deficient according to the 2017 American Society of Civil Engineers’ infrastructure report card. The main causes of bridge deterioration are repeated vehicular loads and adverse environmental exposure. The most dominant deterioration form for steel bridges is corrosion, which is characterized by the loss of metal area resulting in reduction of structural capacity. Corrosion in steel multi-girder bridges is common in cold regions because of the frequent use of deicing chemicals during the winter season as well as leakage caused by bridge joint damage. At times, the rust is serious enough to disconnect the web from the flanges of the girder. This poses significant concerns for load capacity especially at girder ends. The consequences of bridge failure can be disastrous. This research investigates the structural capacity of these corroded steel girders. The mechanical behaviors of deteriorated girders are studied by 3-D finite element models built in ABAQUS and by lab testing. Our analysis is focused on web area loss and web thinning due to corrosion, and their consequences for load capacity reduction.

3-D Soil Structure Interaction

These studies are looking into the effects on soil as well as structural bridge members caused by a disaster. In any disaster, the largest concern is the civil infrastructure. Buildings must stay standing and roads need to be open for emergency personnel or evacuations. Part of the study looks into any bearing failures of loss in stability in the soil during an extreme loading. For a brief look into the task click the image below:

The other part of the study is how the bridge reacts. For a bridge to remain operational it must be able to act in an elastic manner to extreme loading as well as have little permanent displacement. A common foundation used in bridges is the HP piles. First the pile orientation was observed using the ANSYS finite element modeling program. This task is summarized in the image link below:

3-D models looking at single span, multi-span, and curved bridges are being built in the ANSYS program to find combined loads on the HP piles, reactions of the bolts, stress in the plates, and the response under extreme loading. This study will help in the future for more economical designs for bridges.

 

Nano-fiber concrete

This study compared attributes of concrete mixes using single-walled carbon nanotubes (SWNT) multi-walled carbon nanotubes (MWNT) as well as the use of micro-synthetic fibers. Images of the Carbon Nanotubes can be seen here:

In this study, a simple concrete mix was observed by itself, with micro fibers, with MWNT, and a mix of MWNT and fibers. The first factor looked into was the concrete strength in compressive tests. Then using Scanning Electron Microscope (SEM), the concrete microstructures were observed. The SEM is able to produce nanoscopic images for comparison. Examples of these images are shown below:

The study compared the compressive and buckling strength, stiffness, cracking patterns, microstructures and cost. This investigation has applications in bridges, roadways, pipes, precast/prestressed concrete structural members, where strength as well as cracking control is critical.

 

Teaching Innovation

Most civil engineering students consider courses in the structural engineering discipline challenging because these courses usually contain complex mathematics and mechanics. In our classroom practice, new interactive learning materials-screencasts were prepared to supplement the traditional lectures, allowing students to watch at their own pace. The screencasts include detailed solutions to example problems and instructions of how to use a piece of software. With screencasts, students will be able to follow the instructor’s explanation and also read captions broken down each step of the problem in order to understand the problem in greater depth and how the problem relates to the underlying concepts.


Active Learning in Structural Dynamics Using Shake Table

The research objective of this project is to create a new hand-on shake table testing module to improve students’ learning effectiveness and enhance students’ interests in theoretical dynamics topics. Dynamics is a core course in Civil Engineering Technology. The principles of dynamics apply to civil engineering practices in the areas of roadway design, bridge design, structural design and seismic design. Students should have a functional understanding of the materials rather than substitute numbers into equations. The learning outcomes include understanding basic vibrations and dynamics terminology, such as natural frequency, period and damping, and modeling structural systems using single-degree-of-freedom (SDOF) models.