Marc Maguire

Stress Increase of Unbonded Tendons in Continuous Posttensioned Members

AbstractA database of 253 unbonded tendon-reinforced members was assembled and analyzed with a focus on Δfps. Large scatter was observed and gaps were identified in previous databases due to possibly unsuitable inclusion of certain testing programs. The influence of several geometric and material properties was analyzed using a covariance analysis, and significant differences between simple-span and continuous members were observed, although some prediction methods do not differentiate between the two. The assembled prediction models for Δfps had evaluation statistics ranging from 1.84 < λ < 4.11 and 0.06 < R2 < 0.16 and indicating relatively poor accuracy and precision. Modifications to the scaled plastic hinge length ψ for different subsets (simple span, continuous, internally unbonded, and externally unbonded) were suggested to provide the most accurate and precise prediction when compared with the available methods. The proposed method, a modified version of the bridge design code prediction, provides...

Challenges in bridge inspection using small unmanned aerial systems: Results and lessons learned

Unmanned Aerial Systems (UAS) have gained considerable private and commercial interest for a variety of jobs and entertainment in the past 10 years. This paper presents the applications of UAS in transportation and structural engineering with emphasis on bridge inspection. A brief but thorough review of UAS applications for State Department of Transportation in the United States is provided. Potential advantages of UAS are acknowledged and the major challenges of using them for bridge inspections are determined. The feasibility of UAS in crack detection, real-time and post-processing, is studied through a case study in controlled conditions. In addition, fatigue crack detection in steel bridges is investigated using three platforms with different mounted cameras. The results of these case studies showed the possibility of using UAS for damage detection in concrete and steel bridges with comparable results with human inspections in real-time. At its best, current technology limits UAS use to an assistive tool for the inspector to perform a bridge inspection faster, cheaper, and without traffic closure. The major challenges for UAS are satisfying restrictive FAA regulations, control issues in a GPS denied environment, pilot expenses and availability, time and cost allocated to tuning, maintenance, post-processing time and acceptance of the collected data by bridge owners. Using UAS, with self-navigation abilities and improving image- processing algorithms to provide results near real-time could provide bridge inspectors with a useful tool to reduce costs and improve inspection quality.

Magnetizable concrete composite materials for road-embedded wireless power transfer pads

In this paper, MAGnetizable CONcrete (MagCon) composite materials are introduced and studied thoroughly. MagCon material is obtained by mixing cement with a magnetic material, for example, powdered ferrite or magnetite with different aggregate ratios and sizes, and optionally adding other aggregates to the mixture. Effective relative permeability (μr, eff) of MagCon is evaluated as a function of volumetric ratio of the magnetic material in the mixture. Furthermore, the effect of aggregate size of the magnetic materials is examined and the core losses of MagCon are analyzed. Compressive strength of the new material is also discussed. MagCon can be used in the core structure of road-embedded Wireless Power Transfer (WPT) pads for Electric Vehicle (EV) charging applications. MagCon has the benefit of significant design flexibility and reduced cost. This paper investigates how to take advantage of the characteristics of the new composite material to design new pad structures for WPT systems. 3D finite element analysis (FEA) approach is used to simulate and compare the proposed pad design with a properly selected reference pad. The mutual inductance between the aligned primary and secondary coils is adopted as the figure of merit in order to maximize the power transfer capability of WPT pads. Considering the fact that magnetite is significantly less expensive than the ferrite tiles or bars, MagCon with magnetite could be a very cost-effective solution. On the other hand, using MagCon in the road creates a more durable structure comparing with the junction of ferrite bars or tiles in regular concrete. This is important for road-embedded implementation of WPT coils where the pad is permanently under the mechanical stress due to heavy vehicles passing over it.

Behavior of 48-Year-Old Double-Tee Bridge Girders Made with Lightweight Concrete

AbstractThis paper describes the experimental testing of 48-year-old concrete bridge girders that were fabricated using lightweight concrete. After the bridge was decommissioned, three girders were transported to the Systems, Material, and Structural Health (SMASH) Laboratory at Utah State University (USU). The double-tee girders were tested to quantify the effective prestress, flexural capacity, and deck punching shear strength. The experimental results were compared with calculated values based on recommended procedures in the AASHTO LRFD bridge design specifications. The AASHTO refined method underestimated the loss of prestress of the three girders by an average of 17.6%. The calculated flexural capacities were overestimated by an average of 34.0% when compared with the measured values. This unconservative result is believed to be a result of the deck deterioration. The average calculated punching shear capacity was within 3.0% of the measured values. The experimental results were also compared with a...