Koerner R.M.,Drexel University |
Hsuan Y.G.,Drexel University |
Koerner G.R.,Geosynthetic Institute |
Gryger D.,Gannett Fleming Inc.
Geotextiles and Geomembranes
The need for a geotextile to be used for protection against geomembrane puncture by stones and gravel has been recognized for many years. There are presently several methods available for selecting such geotextiles. This paper, however, focuses on the " GRI-Method" , which was originally based on short-term tests and was extended empirically for long-term performance. The reduction factor for creep behavior (RFCR) is of particular interest since its impact on the resulting geotextile design is the greatest.The paper presents results of a 10-year long creep puncture study which is configured exactly the same as was the original short-term testing program. The results indicate that the six ≈38. mm high puncturing cones result in yield of the geomembrane at pressures of 34 and 52. kPa and one even had a small break. The six 12. mm high cones at pressures of 430 and 580 kPa also resulted in geomembrane yield but only by a nominal amount and there were no breaks.As a consequence of these creep test results, the original table for creep reduction factors (RFCR) has been revised into more conservative values. In this regard, the originally published RFCR table should be replaced accordingly. © 2010 Elsevier Ltd. Source
Salhotra A.M.,Gannett Fleming Inc.
Progress in Molecular Biology and Translational Science
Contaminated sites, particularly Superfund sites, not only require remediation but also require health risk analysis of the unremediated site. In this chapter, the term risk refers to the probability and the magnitude of adverse human health effects due to the unintended exposure to chemicals at sites that are contaminated or perceived to be contaminated. The quantitative estimation of this risk, the application to define how clean is clean, and the techniques available to mitigate and manage the risk are discussed:Estimation of exposure or dose and the uncertainties inherent in the calculationsQuantitative chemical-specific measures of human toxicity of chemicals used in the RA processThe metrics used to estimate the carcinogenic and noncarcinogenic riskRisk management and the concepts of acceptable riskRisk assessment and risk management of contaminated sites © 2012 Elsevier Inc. All rights reserved. Source
Li Y.,Gannett Fleming Inc.
For most structural engineers, the design of an eccentrically loaded single angle without lateral restraint along its length was considered to be a formidable task prior to the publication of the 2005 AISC Specification for Structural Steel Buildings. According to Section E5 of the 2005 Specification, the effects of eccentricity on single-angle members are permitted to be neglected by using the effective slenderness ratio as specified, provided that members are loaded at the ends in compression through the same leg; members are attached by welding or by a minimum of two-bolt connections; there are no intermediate transverse loads; the leg length ratio is less than 1.7, if angles are connected through the shorter leg; and the modified KL/r is less than or equal to 200. Table 4-12 of the 13th edition AISC Steel Construction Manual provided the available strengths in axial compression of eccentrically loaded single angles, with the assumption that the compressive force is applied at the geometric y-y axis at a distance of 0.75t from the back of the connected leg, where t is the angle thickness. Table 4-12 has been revised in the 14th edition AISC Steel Construction Manual. The new table corrects some numerical errors in the calculations and moves the compressive force to the midpoint of the connected leg. The values of the axial compressive design strength in Table 4-12 are developed on the basis of bending about the principal axes w-w and z-z. Source
Niedzielski J.C.,Gannett Fleming Inc.
Geotechnical and Structural Engineering Congress 2016 - Proceedings of the Joint Geotechnical and Structural Engineering Congress 2016
The PHX Sky Train project is a key linkage in the City of Phoenix, Arizona, Department of Aviation's multimodal facility which integrates Phoenix Sky Harbor Airport with the City's eastern transit (Valley Metro) hub. This local project consists of a series of different bridge types, built to support the operation of the airport's new transit system, as it stretches from the multi-modal center and 44th St.To the Phoenix Sky Harbor Airport Terminals 3 and 4. These include: (1) steel girder superstructures, (2) cast-in-place post-Tensioned, (3) a precast, pre-stressed post-Tensioned, pedestrian bridge along with (4) a signature cast-in-place structure spanning an airport taxiway. Along with these differing bridge types, came complex geotechnical requirements and in-situ conditions. The design of the large diameter drilled shafts supporting the elevated guideway was complicated by space constraints, due to the elevated guideway alignment being situated adjacent to existing buildings, retaining walls, a baggage cart tunnel, and between an existing retaining wall and an existing high-pressure jet fuel line, all of which had to remain in service during construction. The foundation system supports relatively high axial loads, lateral loads and moments due to the height of the guideway above the ground surface, where it needs to pass over existing concourse walkways, bridges, a taxiway and buildings. The extreme design requirements, together with difficult ground conditions at the site, resulted in several challenges in the design of the deep foundation system. Built under the construction manager-At-risk (CMAR) contract structure, the project was built in multiple phases to accommodate the schedule of the METRO opening in winter 2008. Its design was a puzzle of a series of separate contracts that required tight coordination between multiple designers and stakeholders. Multiple system and design coordination meetings were held by the designers in conjunction with the client (City of Phoenix, Department of Aviation) and the selected contractor. Attendees will take away both technical and managerial lessons-learned from this complex transportation project. Complex environmental demands required a series of innovative design solutions. Moreover, the tight, multi-phase schedule and CM@R design paradigm presented many management challenges which will be discussed. © ASCE. Source
Jacobson K.S.,University of Wisconsin - Milwaukee |
Drew D.M.,Gannett Fleming Inc. |
He Z.,University of Wisconsin - Milwaukee
Environmental Science and Technology
Bioelectrochemical desalination is potentially advantageous because of bioenergy production and integrated wastewater treatment and desalination. In this work, the performance and energy benefits of a liter-scale upflow microbial desalination cell (UMDC) were evaluated. The UMDC desalinated both salt solution (NaCl) and artificial seawater, and the removal rate of total dissolved solid (TDS) increased with an increased hydraulic retention time, although TDS reduction in artificial seawater was lower than that in salt solution. Our analysis suggested that electricity generation was a predominant factor in removing TDS (more than 70%), and that other factors, like water osmosis and unknown processes, also contributed to TDS reduction. It was more favorable given the high energy efficiency, when treating salt solution, to operate the UMDC under the condition of high power output compared with that of high current generation because of the amount of energy production; while high current generation was more desired with seawater desalination because of lower salinity in the effluent. Under the condition of the high power output and the assumption of the UMDC as a predesalination in connection with a reversal osmosis (RO) system, the UMDC could produce electrical energy that might potentially account for 58.1% (salt solution) and 16.5% (artificial seawater) of the energy required by the downstream RO system. Our results demonstrated the great potential of bioelectrochemical desalination. © 2011 American Chemical Society. Source