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Bridge scour monitoring using fixed instrumentation is a good way for the owner to be warned of imminent failure and to take appropriate action before exposing the public to undue risk. This paper demonstrates two cases of bridge scour monitoring systems developed for two bridges in Texas. The lessons learned from the two systems lead the authors to the conclusion that Tethered Buried Switches for early warning and tilt sensors for warning system should be preferred. Acceleration and frequency-based behavior tracked by motion sensors show promise but could only be demonstrated in laboratory experiments, with insufficient field data.

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3-D modeling of aerial wireless coverage is an important requirement for many an applications of UAVs. Typically such model is used in communication-aware path planning of the vehicle. When the surveillance area is vast, such as that of long linear utility infrastructures e.g. power grids, oil and gas pipelines, railway corridors etc., signal coverage is quite sparse due to lack of transmitters in rural/forested terrain. On the other hand, maximal connectivity so as to robustly transmit huge volumes of sensed data in downlink is highly required. However, coverage models for vast areas, especially in remote rural surroundings having complex terrain, are not publicly known, thus inhibiting mission planning for an important class of UAV applications. In this paper, we have tried to address this requirement by establishing such a coverage model. The model is based on a 3-D mesh of sampling locations, over which a sparse set of signal strength measurements are available using pilot flights. From the sparse set, we use heuristics of distance-weighted averaging to closely approximate and predict signal strength measurements at other grid points. We propose a novel metric of representative distance, which leads to approximation error become as less as 5%. The solution holds the promise of being scalable to big grid sizes, as is demonstrated by the simulation results. We believe that this model will form an important stepping stone towards evolution of more robust models, which in turn are needed to enable many an important civilian applications of UAV as a sensing platform.

With the increasing population and the demand associated with it, the infrastructure and transportation facilities have increased rapidly over the years. The progress has been accompanied by an increasing number of vehicle collisions with structures. This type of collision might lead to the damage and sometimes collapse of the structures. In reinforced concrete (RC) structures, columns are usually the most vulnerable members exposed to collisions. However, the existing design guidelines and provisions for protection of these members against collision of vehicles are not adequate. In particular, the desired behavior and the associated performance levels of a structure during a vehicle collision are not defined. Therefore, there is a need to assess the vulnerability of structures against such collisions. This article develops performance-based probabilistic models for the dynamic shear force capacity of RC columns in bridges and buildings. A framework is also developed to estimate the fragility of the RC columns subject to vehicle collision. The developed probabilistic dynamic shear force capacity models can be used for a performance-based design of structures such as buildings and bridges. The developed framework can be used to estimate the adequacy of * To whom correspondence should be addressed. E-mail: gardoni @illinois.edu. a structure to sustain a collision event and make recommendations for repair and retrofit. Proposed approach can be applied to study similar cases of collision such as ship collision to bridge piers, projectile collision into concrete walls and develop adequate models. C 2015 Computer-Aided Civil and Infrastructure Engineering.

Bridges with low clearance are vulnerable to collision with overheight vehicles. Collisions of overheight vehicles can cause fatalities and injuries to the drivers and passengers of the overheight vehicles, and damage to bridge girders. The repair of the damaged bridges can be costly and time consuming. This article investigates the feasibility of developing a bridge bumper that minimizes the physical injuries and the likelihood of fatalities and protects the structural elements of bridges by absorbing the impact energy. The article presents the results of small-scale impact experiments using the proposed bridge bumper with several options of energy-absorbing materials to protect a reinforced concrete beam. Finite element analyses are carried out to simulate the small-scale impact experiments. Optimization of the finite element model is conducted for the response quantities of interest with respect to the geometrical parameters and the material properties of the proposed bridge bumper. Such analysis can guide the design of an optimal bridge bumper that maximizes the energy dissipation and minimizes the damage to the bridge girder and the likelihood of fatalities and injuries. A possible full-scale implementation of the proposed bridge bumper is also described.