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Omaha, NE, United States

Wehbe N.,South Dakota State University | Bahmani P.,Colorado State University | Wehbe A.,Kiewit Engineering Co.
International Journal of Concrete Structures and Materials

The use of light-gauge steel framing in low-rise commercial and industrial building construction has experienced a significant increase in recent years. In such construction, the wall framing is an assembly of cold-formed steel (CFS) studs held between top and bottom CFS tracks. Current construction methods utilize heavy hot-rolled steel sections, such as steel angles or hollow structural section tubes, to transfer the load from the end seats of the floor joist and/or from the load-bearing wall studs of the stories above to the supporting load-bearing wall below. The use of hot rolled steel elements results in significant increase in construction cost and time. Such heavy steel elements would be unnecessary if the concrete slab thickening on top of the CFS wall can be made to act compositely with the CFS track. Composite action can be achieved by attaching stand-off screws to the track and encapsulating the screw shank in the deck concrete. A series of experimental studies were performed on full-scale test specimens representing concrete/CFS flexural elements under gravity loads. The studies were designed to investigate the structural performance of concrete/CFS simple beams and concrete/CFS continuous headers. The results indicate that concrete/CFS composite flexural elements are feasible and their structural behavior can be modeled with reasonable accuracy. © 2013 The Author(s). Source

Walberg F.,URS Corporation | Saye S.,Kiewit Engineering Co. | Bird G.R.,URS Corporation | Linnan B.,URS Corporation | Boeckmann A.,University of Missouri
Geotechnical Special Publication

Eppley Airfield in Omaha, Nebraska is sited along the west bank of the Missouri River with existing infrastructure and assets valued at a historical cost of more than $470 million and with an estimated annual economic impact of $750 million. Flood protection is provided by a federal levee system with sponsorship by the City of Omaha. The 2011 Missouri River Flood threatened the airfield, so the Omaha Airport Authority (OAA) assembled a team of engineers and contractors to fight the flood. Actions implemented by the project team included modification of pump stations, construction of outlet structures, berms, and graded filters, rehabilitation/pumping of existing relief wells, and installation/pumping of 70 new deep dewatering wells. The response actions were successful and the airfield operated continuously during the flood with no disruption in services or loss of critical facilities. The total cost of efforts to protect the airfield was about $24 million. Numerical seepage models were developed and calibrated during the flood to predict distress at higher river levels. © 2013 American Society of Civil Engineers. Source

Harris D.K.,Michigan Technological University | Lutch R.H.,Kiewit Engineering Co. | Ahlborn T.M.,Michigan Technological University | Duong P.,L.B. Foster CXT Inc.
Journal of Transportation Engineering

In response to rising energy costs, there is increased demand for efficient and sustainable transportation of people and goods. One source of such transportation is the railroad. To accommodate the increased demand, railroads are constructing new track and upgrading existing track. This update to the track system will increase its capacity and make it a more reliable means of transportation compared to other alternatives. In addition to increasing the track system capacity, railroads are considering an increase in the size of the typical freight rail car to allow larger tonnage. An increase in rail car loads will, in turn, require the design of track components to accommodate these loads. This design change is especially pertinent to crossties that support the rail and serve to transmit loads down to the substructure. Today, the use of concrete ties is on the rise in North America as they become an economical alternative, competitive with the historical wood ties used in industry, providing performance that surpasses its competition in terms of durability and capacity. Because of the increased loads heavy-haul railroads are considering applying to their tracks, current designs of prestressed concrete railroad ties for heavy-haul applications may be undersized. In an effort to maximize tie capacity while maintaining tie geometry, fastening systems, and installation equipment, a parametric study to optimize the existing designs was completed. The optimization focused on maximizing the capacity of an existing tie geometry through an investigation of prestressing quantity, configuration, stress levels, and other material properties. The results of the parametric optimization indicate that the capacity of an existing tie can be increased most efficiently by increasing the diameter of the prestressing and concrete strength. Findings of the study demonstrate that additional research is needed to evaluate the true capacity of concrete ties because of the impacts of deep beam effects and inadequate development length in the rail seat region. © 2011 American Society of Civil Engineers. Source

Saye S.R.,Kiewit Engineering Co. | Brown D.A.,Dan Brown and Associates LLC | Lutenegger A.J.,University of Massachusetts Amherst
Journal of Geotechnical and Geoenvironmental Engineering

This paper presents a method to estimate the side resistance of a driven displacement-pipe pile in clay using the stress history and normalized soil engineering parameter (SHANSEP) concept. The side resistance is treated as an adhesion, and this adhesion is normalized to the effective overburden stress. This normalized adhesion is then related to the soil overconsolidation ratio using an adaptation of the SHANSEP concept to separate the normally consolidated behavior from the overconsolidated behavior. This approach provides a rational means of screening representative measurements of undrained shear strength from measurements that may have been affected by sample disturbance. Assessments of the soil overconsolidation ratio are developed with laboratory odometer test data and an empirical approach using laboratory undrained strength data. A database of pile load tests screened for the effects of incomplete set-up and soil-property data screened for the effects of sample disturbance is used to evaluate the normalized side resistance and the relationship of normalized side resistance to overconsolidation ratio. © 2013 American Society of Civil Engineers. Source

Zhang Y.,Iowa State University | Johnson A.E.,Kiewit Engineering Co. | White D.J.,Iowa State University
Cold Regions Science and Technology

Freeze-thaw cycles in pavement foundation layers can cause rapid accumulation of pavement damage. To reduce the effects of freeze-thaw cycles, there is a need to characterize and design low frost susceptible foundation layers. This paper focuses on the laboratory frost-heave and thaw-weakening performance of pavement foundation materials that were stabilized with combinations of self-cementing class C fly ash, Portland cement, and polymer fibers. Additions of fly ash (15% by weight), cement, and cement + fibers presented improvement on frost susceptibility of soils. Grain size distribution and curing time and compaction delay of chemical stabilization influenced soil freeze-thaw performance. The heave rate has to be controlled to less than 4 mm/day to achieve very low thaw-weakening susceptibility per ASTM D5918. A proposed classification for chemically stabilized soils identifies thaw-susceptibility as negligible for post-test CBR values ≥ 100. © 2015 Elsevier B.V.. Source

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