In recent years, prestressed concrete bridges have dominated the bridge type selection processes in Colorado. This can be attributed to a lack of steel mills combined with a strong presence of precast fabricators in the region. In addition, a lack of readily available economical and innovative procedures to design and construct steel bridges has hindered the industry in certain areas such as Colorado. During this research it was identified that designing steel girders as simply supported for the non composite dead loads and continuous for composite dead loads and live loads would provide economy. A preliminary girder selection software was created using this design procedure. The software takes user inputted data, such as span length, width, number of girders along with various other design inputs, and displays the lightest wide flange beam size that would support the loads using AASHTO LRFD Design Specifications. Using the girder selection software, design charts and tables were created to outline structural steel weight to span length and number of girders. The design charts will aid the bridge type selection process by giving designers an accurate measurement of minimum steel requirements for numerous one, two, and three span steel bridges.
This study applies contract bid tabulations and element-level condition records to develop element-level actions, costs for actions, transition probabilities for models of deterioration of bridge elements, and transition probabilities for improvements to elements due to actions. The study uses transition probabilities for element deterioration to compute the number of years to possible loss of safety in bridges, and to compute the number of years for inspection intervals. It examines variations in costs of actions and deterioration of elements among CDOT regions.
This report documents two efforts to support CDOT in the area of Safety Performance Function (SPF) development. The first involved the data collection and development of SPFs for five categories of ramp terminals at diamond interchanges. The second effort involved estimating the overdispersion parameters for a number of existing SPFs already in use by CDOT for various roadway segment categories.
Historic Residential Subdivisions of Metropolitan Denver, 1940-1965, documents the development of mid-century suburbs in CDOT Region 6. The report follows the National Register of Historic Places format for multiple property documentation, and is intended as a tool for researchers who need to determine the National Register eligibility for neighborhoods with the potential to be impacted by transportation projects.
This report presents a case study on the evaluation of bridge decks using various non-destructive test methods. The primary interest lies in quantifying delaminated areas in deck concrete covered with asphalt overlays. Analytical and computational models are formulated to decompose the intensity of GPR scales into two categories: i) initiation and progression of corrosion and ii) delamination of deck concrete, which show good agreement with repaired areas. Parametric investigations emphasize the significance of rebar spacing and concrete cover in determining the extent of deck delamination.
This report summarizes the analytical studies on the seismic performance of typical Colorado concrete bridges, particularly those with curved and skewed configurations. A set of bridge models with different geometric configurations derived from. a prototype bridge selected in Denver area were studied. Some discussions about the connection modeling are carried out in terms of the interior bent support. For the displacement-based and force-based designs, due to the lack of design details that without detailed analyses of all possible detailing options. Therefore, some general observations of these two design concepts are ummarized in the end of the report. In the appendices, the design examples of 2-span and 3-span bridges are listed to help the engineers to conduct bridge seismic analysis in Colorado.
Mount Evans Highway (SH 5) has been severely damaged by permafrost degradation and freeze-thaw processes. We assessed the effects of the current roadway configuration on the permafrost, hydrologic processes, vegetation, and soils of the Summit Lake Park wetland complex. We also reviewed and synthesized available literature to develop design recommendations for mitigating permafrost degradation, thaw-induced subsidence and frost damage, and hydrologic alterations to alpine wetlands. The existing roadway has profoundly altered permafrost conditions, hydrological processes, and wetland plant communities.
Infiltration-induced landslides are common hazards to roads in Colorado. A new methodology that uses recent advances in unsaturated soil mechanics and hydrology was developed and tested. The approach consists of using soil suction and moisture content field information in the prediction of the likelihood of landslide movement. The testing ground was an active landslide on I-70 west of the Eisenhower/Johnson Memorial Tunnels. Results indicate that the unique hydrology of the site is a key component in its stability and considering the whole water basin and not just the failure area is important.
This report presents the development of ultra-high performance concrete (UHPC) using locally available materials that reduce construction costs compared with commercial products. With the aim of achieving a specified compressive strength of 20 ksi, a UHPC mixture is formulated. The implications of various constituent types are examined with an emphasis on silica compounds (silica fume, silica powder, silica sand, finer silica sand, pyrogenic silica, and precipitated silica), including steel and polypropylene fibers. Bond tests are conducted to evaluate the development length of the UHPC. Cost analysis shows that the prototype UHPC is up to 74% less expensive than commercial products.
CDOT has prioritized the research of select methods to evaluate the performance of the I-25 Gap work zone and future CDOT construction projects. Work zone performance measures provide comparative metrics that quantify the level of impact a work zone has on travelers, residents, businesses and workers. CDOT has identified the need to research and apply performance measures to the I-25 Gap construction project; establishing a foundation to improve the decisions that are made during planning, design and construction for the remainder of the I-25 Gap project and for future CDOT highway construction projects.
