Bondi R.,Michael Baker Jr. Inc.
Modern Techniques in Bridge Engineering | Year: 2011
A Concrete Filled Tubular Flange Girder (CFTFG) is an I-shaped girder that uses a concrete filled hollow structural section (HSS) as the top flange. A key advantage of the CFTFG is the increased torsional stability that reduces the need to brace the girders under construction loading conditions. Time and cost savings in fabricating and erecting the bridge girder system can be realized by a reduced number of diaphragms along with the locating the field splices over the piers. Combined with span-by-span construction, CFTFGs provide a robust steel structure that can erected much more efficiently than conventional I-girder bridges. A first of its kind bridge in the world, using of Concrete Filled Tubular Flange Girders (CFTFGs), has been designed and constructed in 2010. This demonstration project is a two span structure over Tionesta Creek, located in western Pennsylvania. This demonstration project marks the culmination of research funded by FHWA and PennDOT from concept, to laboratory prototype, to implementation.
Leshchinsky D.,University of Delaware |
Imamoglu B.,University of Delaware |
Imamoglu B.,Michael Baker Jr. Inc. |
Meehan C.L.,University of Delaware
Journal of Geotechnical and Geoenvironmental Engineering | Year: 2010
An instrumented geogrid-reinforced wall constructed on a highly compressible foundation was deconstructed 16 months after its completion, providing a unique opportunity to exhume and examine the instrumented geogrids that were used to construct the wall. The objectives of this post mortem study were: (1) to inspect the condition of the strain gauges that were attached to the geogrid layers before construction and to verify the reliability of their output; (2) to develop a procedure in which the residual (plastic) strains along exhumed geogrid panels could be determined; and (3) to assess the in situ strain and force distribution along geogrid panels based on the measured residual strains from the exhumed geogrids. After exhumation, it was observed that many of the attached strain gauges failed due to full or partial debonding from the geogrid, thus rendering outputs which potentially underestimated the actual strain. Combining aperture measurements of virgin and exhumed geogrids, all from the same manufacturing lots, enabled the assessment of residual strains following stress relaxation. Laboratory simulation of loading and unloading, including creep and relaxation, yielded a relationship between the measured residual strains and the in situ strain and force distribution; i.e., the residual strain fingerprint provided insight into the behavior of the geogrids within the wall prior to its deconstruction. The mobilized maximum tensile strains in the geogrid panels along the height of the wall were roughly uniform, in the range 4±1%. These findings imply that if the same type of reinforcement had been used throughout the height of the wall, the mobilized force along the height would have been relatively uniform. The back-calculated maximum force in the geogrids indicated that the factor of safety on the long-term strengths of the geogrids ranged from about 1.4 on the stronger/stiffer geogrid to about 1.8 on the weaker/softer geogrid. © 2010 ASCE.
Russo S.A.,Hazen and Sawyer |
Hunn J.,Michael Baker Jr. Inc. |
Characklis G.W.,University of North Carolina at Chapel Hill
Journal of Environmental Engineering | Year: 2011
The development of a total maximum daily load (TMDL) for water bodies impaired by elevated microbial levels (the second leading cause of impairment nationally) requires an understanding of microbial transport processes at the watershed scale. Continuous monitoring of impaired water bodies can be expensive, and models are typically employed, but most current models represent bacteria as single discrete (free phase) organisms with near-neutral buoyancy, subject to first-order decay resulting primarily from predation or die-off. Studies indicate, however, that a significant fraction of microbes are associated with sediment particles, both in the water column and bed-sediments, associations that can impact microbial transport behavior and survival rates. This work incorporates considerations of microbial partitioning and its impact on survival into microbial fate and transport modeling using a well-characterized watershed. Agreement between observed and modeled instream microbial concentrations is comparable to, or better than, that seen in similar studies. Nonetheless, differences in instream concentration between model runs that consider microbe-sediment association (with attendant survival differences) and those that assume all microbes exist in the free phase are relatively small. A sensitivity analysis of relevant model inputs further indicates the minor effects of incorporating these considerations. The low settling velocities of small particles with which microbes typically associate and the dominance of other inputs related to wet weather microbial loadings, when compared with resuspension, result in the reduced significance of microbial partitioning as a factor in water quality modeling. © 2011 American Society of Civil Engineers.
Schock B.A.,TranSystems Corporation |
Caleb Hing C.L.,Michael Baker Jr. Inc.
Earth and Space 2014: Engineering for Extreme Environments - Proceedings of the 14th Biennial International Conference on Engineering, Science, Construction, and Operations in Challenging Environments | Year: 2014
A discussion of the concepts that civil engineers and planners can bring to the table in the development of a Mars built environment, this paper focuses on the civil engineering challenges and differences of Mars and presents recommendations for the planning and engineering of a Mars colony. The basics of terrestrial civil engineering for undeveloped areas are discussed from an American perspective. A contrast is shown between the anticipated conditions on Mars and those on Earth. Attention is drawn to the assumptions of modern infrastructure development, based on millennia of human history and Earth conditions and which could or should be modified for Martian environmental challenges. A concept is discussed for mimicking the development and civilization of terrestrial life for a Martian settlement, taking into account these environmental challenges, differences in basic design assumptions and correction of existing development patterns which are inefficient and unnecessary on Mars.
Johnson J.,Michael Baker Jr. Inc. |
Ozbek M.,Colorado State University
Transportation Research Record | Year: 2013
Because of limited funds, a greater demand for use, and continuous deterioration, it is crucial that transportation agencies have effective decision-making processes and tools, such as bridge management systems, to manage agency bridge networks. Given the shortcomings of the current bridge management practices as repeatedly highlighted in the literature, it is evident that a decision process that only involves a single rating or index, such as the sufficiency rating or the bridge health index, is inadequate for bridge management. Therefore, there is a clear need to pursue and develop supplemental bridge management practices. The primary contribution of this research is to provide engineers, managers, and decision makers with effective bridge management components that have well-defined goals and related items. Additionally, these components clearly identify and distinguish differences in bridge attributes that may go unnoticed when a single criterion is used. Transportation agencies may use these bridge management components in a variety of ways to complement current bridge management practices; this usage may better illustrate the performance of the agencies' bridges. The specific objectives of this research are (a) to identify the appropriate items that make up each of the aforementioned components and (b) to determine the relative importance of those items, as represented by weighting factors. To achieve these objectives, this research was conducted in two parts, and input was sought from key bridge management personnel, industry professionals, and academics. The first part consisted of a survey; the second part utilized a mathematical method entitled the analytic hierarchy process.