Schock B.A.,Transystems Inc |
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.
Sun X.,Michigan Technological University |
Zhang B.,Michael Baker Jr. Inc. |
Dai Q.,Michigan Technological University |
Yu X.,Case Western Reserve University
Construction and Building Materials | Year: 2015
This study investigates the internal curing effects on the microstructure and permeability of interface transition zones (ITZ) in cement mortar samples with SEM imaging, transport simulation, and hydration modeling techniques. Two types of mortar samples were prepared with saturated lightweight aggregates (with internal curing) and regular sands (without internal curing). The scanning electron microscope (SEM) techniques were applied to characterize the ITZ microstructure of both mortar samples. The internal curing introduced by lightweight aggregates (LWA) is found to have significant impacts on ITZ microstructure development in mortar/concrete samples. 3D image reconstruction techniques were used to generate the 3D microstructure images for transport property analysis. The permeability solver code (developed in National Institute of Standards and Technology) was used to calculate the total porosity, percolated porosity, and permeability of the 3D digital samples. The characterization and simulation results indicate that the permeability of ITZ section in samples with internal curing were smaller due to less percolated porosity and smaller characteristic pore sizes, compared to the samples without internal curing. To further understand the dynamic process of ITZ formation, a meso scale chemo-thermo-hydraulic model is developed to simulate the development of ITZ zone, including processes such as migration of water, production of heat, and growth of CSH, that are involved in cement hydration. Results indicate that the interactions of cement and aggregate, which is responsible for the development of ITZ zone, can be described from computational simulations. The combination of advanced imaging (which captures the microstructure of ITZ at a certain time) and holistic simulations (which describes the time evolution of ITZ in the meso scale) provides a promising way to understand the influence of internal curing on the behaviors and evolution of ITZ. © 2014 Elsevier Ltd. All rights reserved.
Vanevenhoven L.M.,Michael Baker Jr. Inc. |
Vanevenhoven L.M.,University of Wisconsin - Madison |
Shield C.K.,University of Minnesota |
Bank L.C.,University of Wisconsin - Madison
Journal of Structural Engineering | Year: 2010
Fiber-reinforced polymer (FRP) pultruded profiles are produced by a number of manufacturers worldwide in similar, but nonstandard, wide-flange, I, angle, and tubular profiles. At present there is no American National Standards Institute approved design code in the United States for structural design with pultruded FRP profiles. Manufacturers of pultruded profiles each provide their own design equations, design methods, material properties, and safety factors for their pultruded products. There is a need for standardization of production and design of pultruded profiles to enable mainstream use of these profiles in structural engineering practice. The purpose of this paper is twofold: (1) to provide appropriate resistance factors (φ factors) for wide-flange pultruded columns that are compatible with ASCE 7 load factors and (2) to provide a unified analytical equation for local and global buckling of concentrically loaded axial members, which may be appropriate for a future design code. The resistance factors are provided for different target levels of structural reliability, Β, and for different nominal design properties of the pultruded materials. The resistance factors were determined using Monte Carlo simulation based on the results of 75 tests of full-scale pultruded columns that have been reported in the literature. In addition, resistance factors and structural reliabilities were calculated for the design equations provided by the manufactures in their design codes. The paper demonstrates that a unified design equation for pultruded columns can be developed for LRFD with reliability indices that are similar to those used for conventional materials. The paper also shows that markedly different reliability indices are obtained for the different manufacturer-provided equations even though identical allowable stress design safety factors are recommended by all manufacturers. © 2010 ASCE.
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.
Pantelides C.P.,University of Utah |
Fitzsimmons G.,Michael Baker Jr. Inc.
Journal of Bridge Engineering | Year: 2012
The paper presents a case study for comparing the seismic rehabilitation of four reinforced concrete multicolumn bridge bents typical of older bridges not designed for current seismic code criteria. The types of intervention included connecting the piles to the pile caps with high-strength prestressing steel bars, widening of an existing strut beam connecting the pile caps, construction of a new reinforced concrete grade beam overlay to connect the pile caps, and carbon fiber reinforced polymer composite jackets for strengthening the columns and cap-beam-column joints. The paper includes the hysteresis curves from in situ experiments in which a lateral quasi-static cyclic load was applied at the cap-beam and comparisons to analytical pushover curves. A comparison of the capacity of the four bents to the demand of several earthquake records including historical and NEHRP design earthquakes is developed. The cost of seismic rehabilitation of the four bridge bents is presented along with the peak maximum lateral load and maximum displacement achieved in the experiments. The cost of the seismic rehabilitation is related to the performance of each bridge bent. The bridge bent with the lowest level of intervention had the lowest cost and met the displacement and base shear demands for the 10% in 50:years NEHRP design earthquake; the bridge bent with the highest level of intervention had the highest cost and met the displacement and base shear demands for the 2% in 50:years NEHRP design earthquake. © 2012 American Society of Civil Engineers.
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.
Yager G.C.,Michael Baker Jr. Inc. |
Ravens T.M.,University of Alaska Anchorage
ISCORD 2013: Planning for Sustainable Cold Regions - Proceedings of the 10th International Symposium on Cold Regions Development | Year: 2013
Solid-filled causeways have been used along the Beaufort Sea coastline to support oil and gas drilling operations and have provided maritime access on a shallow coast. The Endicott causeway, located in the Sagavanirktok River delta on Alaska's North Slope, has altered the coastal hydrodynamics that transport sediments across the delta. Sedimentation has been observed in the lagoon, shoreward of the Endicott causeway. Past studies have raised concern that infilling of the lagoon may eventually alter fish migration. The main objectives of this research were to determine if the lagoon has continued to infill and if the pattern of infilling is related to the hydrodynamic alterations imposed by the causeway. The results indicated that fine-grained sediment has continued to deposit in the lagoon, and the deposition is related to the placement of the causeway. Further, modeling and analysis indicate that the rate of deposition is currently decreasing. © 2013 American Society of Civil Engineers.
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.
Kueper D.,Michael Baker Jr. Inc.
ITE Journal (Institute of Transportation Engineers) | Year: 2010
Context sensitive design (CSD) has influenced how state departments of transportation have planned and designed roadway projects, but the impact of CSD will be limited unless states amend standards in their design manuals to encourage flexible design practices. This paper summarizes design practices in all 50 states to determine whether CSD is currently being promoted.
Porco J.W.,Michael Baker Jr. Inc.
Journal / American Water Works Association | Year: 2010
The US Department of Homeland Security (USDHS), Science and Technology Directorate, along with the cooperating partner the US Environmental Protection Agency (USEPA), commissioned a study of municipal water systems (MWS), to determine potential threats and protective mitigation measures. The results of the study were reported in two volumes, 'Municipal water distribution system security study: Recommendations for science and technology investments'. An assessment was made of potential threats from chemical, biological, and radiological (CBR) terrorist attacks and related potential threat that could be brought from a trusted insider to the distribution component of the country's MWSs. The study also examined the state of the art in security monitoring and decontamination technologies and processes. The study then identified technological and operational research and development (R&D) gaps that should be addressed respond to threats and protect citizens.