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Structural Advance Planning Studies
<br />Development of the Project Study Report Equivalent (PSRE)
<br />will require the preparation of a bridge Advance Planning
<br />Study (APS) for Santa Ana Grade Separation Improvements.
<br />The purpose of Advance Planning Study is to evaluate
<br />feasible structure types, understand City, County, OCTA,
<br />SCRRA, and Caltrans requirements, identify constraints,
<br />and develop associated cost estimate summary for the
<br />structure work involved. Additional APS's will be prepared as
<br />appropriate to consider alternative structure types.
<br />A comprehensive design memo must be prepared to
<br />summarize and document the following key items: 1)
<br />important, or unusual, design assumptions or structure
<br />features, particularly any deviations from standards
<br />to accommodate the site constraints, 2) discussions
<br />with City/ County /OCTA /SCRRA /Caltrans /Stakeholders/
<br />Resource Agencies concerning any key assumptions, 3)
<br />city requirements such as aesthetics, improvements in the
<br />vicinity of the structure, or other obstructions, 4) special
<br />foundation requirements, special excavations such as Type
<br />A, Type D (if ground water is shallow), and /or hazardous
<br />or contaminated material, shoring adjacent to the tracks,
<br />4) special construction requirements, including limited
<br />site accessibility, 5) stage construction, and 6) SCRRA
<br />Requirements (closure windows, flagmen etc.).
<br />The information identified in the APS as listed above
<br />and preliminary structure costs are used as a part of the
<br />evaluation to select the best project structure alternative,
<br />which will be carried into the design phase along with the
<br />preferred roadway alignment alternative.
<br />Two structure alternatives are presented and discussed in
<br />detail in the ensuing sections.
<br />Construct Through Girder Underpass on -site and Roll
<br />into Place for Final
<br />This structure alternative has the distinct advantage of
<br />constructing the bridge in place without long -term disruption
<br />of Metrolink's service operations, thereby eliminating the
<br />need of shoofly tracks and station modifications, and
<br />minimizing the time for the vehicular traffic to be detoured
<br />around the construction site. While the traveling public has
<br />been moved to a detour road, this completed structure can
<br />be rolled into place over a 56 hour weekend work window,
<br />from Friday night to Monday morning, when train service can
<br />then be restored. What will remain will be the construction
<br />of the depressed roadbed for Santa Ana Boulevard, in a "top
<br />down" construction sequence, that is to build the walls first,
<br />and then excavate the roadway in front of the wall to final
<br />grade. Upon completion of roadway construction, traffic can
<br />resume the normal pattern on the new facility. This method
<br />for construction of the bridge has been done successfully,
<br />previously in 1994, for the double track bridge over the Santa
<br />Ana River. Figure 4 shows the general plan sheet of this
<br />proposed structure type, and the construction sequencing
<br />associated with building this structure.
<br />AECOM designed a pre -cast bridge that was rolled into
<br />place on the Nogales Street Grade Separation
<br />The span length required to span the Santa Ana Boulevard
<br />roadbed is approximately 134'. The typical span range for
<br />this type of construction extends to about 150 -ft under
<br />Cooper E -80 loading. Therefore, even though the required
<br />span is nearing the upper limit of the typical structure span
<br />length, this structure type is suitable for construction of new
<br />underpass. The total structure depth for the replacement of
<br />the double track would be approximately 13' -6 ". Provisions
<br />can be made in the bridge design so that is capable of
<br />supporting a future third track, should this become a
<br />requirement of OCTA /SCRRA. To support a possible third
<br />track, the through girder, on the either left or right side of
<br />the underpass, will be required to have a structure depth
<br />approaching 15' in order to support the full weight of a
<br />Cooper E -80 live load.
<br />The abutments will be precast type and will be supported
<br />on drilled shafts (the shafts can be constructed under
<br />normal, single track weekend closures prior to the 56 hour
<br />work window, while the abutments would be placed as one
<br />of the first operations during said window). The through
<br />girder underpass structure can be constructed in the
<br />staging areas near the project site. Once the substructure
<br />work is completed, and the 56 hour work window has been
<br />implemented, the bridge superstructure can be placed on
<br />rollers and moved from the staging area location to the
<br />finished main line alignment.
<br />Special details will be required, including jacking stiffeners
<br />in the through girders where the bridge jacks are to be
<br />placed for raising the bridge off of its bearings, and bearing
<br />stiffeners at the locations where roller bearings are to be
<br />placed in order to support the bridge and roll it from the
<br />staging area to its final installation location on the main line
<br />alignment. In addition, a system must be constructed to
<br />support the dead load of the bridge superstructure on the
<br />roller bearings and guide its movement from the staging area
<br />to its final installation position. The bridge bearings used to
<br />support the bridge at the staging area can be removed and
<br />placed on the finished abutment seats in the final installation
<br />location.
<br />Construct Precast Prestressed Box Girder Underpass
<br />000
<br />®® Proposal for Project Study Report Equivalent and Conceptual Engineering Plans for
<br />Santa Ana Boulevard Grade Separation Project
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