Arema manual chapter 28

Forest means a tract of land thick with trees and underbrush. Apple means Apple Inc. Management Company means the firm overseeing the operation and management of the Participating Property; and shall mean the Grantee in any event wherein the Management Company is required to perform any obligations under this Agreement. ATC means a measure of the transfer capability remaining in the physical transmission network for further commercial activity over and above already committed uses.

Management Group means the group consisting of the directors, executive officers and other management personnel of the Borrower, Holdings or any Parent Entity, as the case may be, on the Closing Date together with a any new directors whose election by such boards of directors or whose nomination for election by the shareholders of the Borrower, Holdings or any Parent Entity, as the case may be, was approved by a vote of a majority of the directors of the Borrower, Holdings or any Parent Entity, as the case may be, then still in office who were either directors on the Closing Date or whose election or nomination was previously so approved and b executive officers and other management personnel of the Borrower, Holdings or any Parent Entity, as the case may be, hired at a time when the directors on the Closing Date together with the directors so approved constituted a majority of the directors of the Borrower or Holdings, as the case may be.

The use of precast elements, as shown in Figure Bridge The existing bridge, shown in Figure The plate-girder was to remain in place and the timber trestle portion of the bridge was to be replaced. Substructure construction was to be performed without interference or downtime to the railroad.

A precast, prestressed concrete superstructure system was selected based on economics, speed of erection and the ability to meet the construction constraints associated with the need for minimal disruption to train operations. Based on a field survey of the timber bent locations, new bent locations were selected to minimize interference with existing timber pile bents and optimize beam spans.

A span length of 44 ft was selected for the new superstructure. For this span length, in. The bents consisted of ft long, 4-ft diameter drilled shafts, 4-ft diameter cast-in-place reinforced concrete column extensions and cap beams. The sequence of construction was as follows: The existing bridge footwalk and handrail were removed as required to facilitate drilled shaft installation.

The drilled shafts were spaced at ft centers perpendicular to the track to allow installation of the drilled shafts without interference to railroad operations. Continuous train operations were maintained throughout the entire construction of the substructure.

Due to foundation conditions, steel pipe casing was necessary for drilled shaft installation. The pipe casing was installed using a vibratory hammer. Reinforcing steel cages were set and the holes were filled with 4, psi compressive strength concrete. Drilled shaft column extensions, bent cap beams and the abutment were constructed under the existing timber superstructure. Due to the depth of the new concrete beams, the bent and abutment construction were completed without interfering with the existing timber superstructure, as shown in Figure In a continuous, well-planned procedure, the ballast, ties and rail were placed and train operations were resumed.

The use of precast concrete allowed the Union Pacific Railroad to replace a timber trestle with a stronger, more durable structural system with minimal disruption to railroad service. The completed bridge is shown in Figure Solid slab beams are used for spans up to 20 ft, especially when superstructure depth has to be minimized. Prestressed concrete double-cell box beams are used for spans up to 50 ft in length. Prestressed concrete single-cell box beams are more economical for spans longer than 40 ft and are used for span lengths up to 80 ft.

When span lengths exceed 80 ft, prestressed concrete I-beams with a composite deck become more feasible from a design, economic and construction point of view. This example illustrates the design of a non-composite, prestressed concrete, double-cell box beam.

Therefore, the beam has to carry all the dead loads, superimposed dead loads and live load. The beams are assumed to be fully prestressed under service load conditions. The dead load consists of the self-weight of the beam including diaphragms. The superimposed dead loads consist of ballast, ties, rails, concrete curbs and handrails, as shown in Figures The beams in this example are checked for both serviceability and strength requirements.

Clear Handrail post Typ. Precast curb and walkway 30" Prestressed concrete box beam 8" Min. Depending on available computation resources and designer preferences, other levels of precision may be used. Note that the depth varies from 30 in. Reinforcement in curbs and walkway not shown for clarity A distribution factor DF equal to 0. Shear Force at 1. Bending Moment at Midspan, ft-kips Allowable tensile stress in prestressing tendons immediately after prestress transfer is the larger of 0.

Total No. Taken as 0. For this design example, stresses will be checked at midspan and at the ends, which will govern straight strand designs without debonding. However, in this design example, a standard beam design is being checked. Therefore it is conservative to check the stresses at the very end of the member, assuming the full prestress force is effective at that location.

Since the strands are straight and all strands are bonded for the full length of the beam, the concrete stresses at the end are simply the stresses at midspan without the stress due to dead load moment. The prestress force is at its maximum value at release and service loads do not affect stresses at the end of the beam. Therefore, stresses at release will govern at the end of the beam, so there is no need to check stresses at the end at service loads.

This is because, at the flexural strength, the strands located higher in the cross-section will not reach a strain and stress as high as the bottom strands.

However, for this standard beam design, the strands at midheight have been included as shown above. A strain compatibility analysis described in Sections 8. Such an analysis for this beam indicates that the strands at midheight would reach a stress of approximately ksi, which is reasonable when compared with the stress, fps, computed below.

The same analysis indicates that the strands in the bottom row would reach a stress of nearly ksi. Therefore, in this case, incorporating the strands at midheight has provided a reasonable result. If the strands at midheight are neglected, the strength of the section at midspan would prove to be inadequate. Therefore, rectangular section assumption is appropriate. The calculation not shown here but similar to the calculation in Section 9.

Final strand locations are shown in Figure In this design example, the critical section for shear is calculated from the centerline of the bearings since the pads are not rigid and have the potential to rotate. Vu d According to this method, Vc is the lesser of Vci or Vcw. Calculations for the top slab flexural reinforcement are not provided in this example. Use 4 stirrups 4 legs at 4-in. Buy Downloadable PDF.

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