Cracks on a bridge deck should be ideally detected at an early stage in order to prevent further damage. To ensure safety, it is necessary to inspect the quality of concrete decks at regular intervals. Conventional methods usually include manual inspection of concrete surfaces to determine defects. Though very e↵ective, these methods are time-ine cient. This paper presents the use of computer-v...

In 3-D analyses of rock slopes there’re can be numerous sliding paths a long a coplanar nonpersistent discontinuity with a known strike. This paper describes an approach for the determination of a most probable sliding path. For this particular study, several blocks of gypsum with the dimensions of 15×15×15 cm containing coplanar non-persistent open joints were fabricated. The models have vario...

FHWA has completed a multiyear study of systems and techniques to identify and characterize cracks in steel bridge structures. The study was conducted by FHWA’s Nondestructive Evaluation (NDE) Laboratory at the Turner-Fairbank Highway Research Center in McLean, VA. The study, called the Steel Bridge Testing Program, was authorized under the 2005 Safe, Accountable, Flexible, Efficient Transporta...

The design of a pneumatic pulse-width modulated pressure control via trajectory optimized fast-switching electromagnetic valves is presented. Two fast-switching valves are used in a half bridge configuration for pressure control in a pneumatic volume. The valves are operated using a feedforward control, which guarantees soft landing and time optimality. The control performance and achievable no...

The objective of this research program is to develop microwave scattering techniques for obtaining quantitative information about the characteristic dimensions of surface cracks in metals. Work carried out during the past year has emphasized experimental techniques. The use of an IF bridge and a nearfield dielectric probe to improve the sensitivity of our 100-GHz eddy-current measurement system...

The 20-year activities of a medical supervisory panel appointed under the terms of a settlement agreement of the Bowling v. Pfizer class action suit involving the Björk-Shiley convexo-concave (BSCC) heart valve are detailed. Of approximately 86,000 valves implanted, catastrophic failure of the valve was reported in 663 patients from 1978 to 2012. In 1994, a 7-member medical panel consisting of ...

A concrete bridge over Interstate 70 east of Denver, Colorado was impacted by a fork lift being transported by a truck moving at a speed of approximately 75 mph. The forklift impacted the east face of the prestressed concrete I-beam bridge girder, resulting in severe cracking and concrete spalling on both sides of the eastmost girder. Polymer-modified repair mortar was used to repair spalled ar...

We used optical experiments and high-speed photography to interpret the origins of tensile fractures that form during dynamic shear rupture in laboratory experiments. Sub-Rayleigh (slower than the Rayleigh wave speed, cR) shear ruptures in Homalite-100 produce damage zones consisting of an array of tensile cracks. These cracks nucleate and grow within cohesive zones behind the tips of shear rup...