HBM Experience – AA Hanger

Preliminary Investigation for the Adequacy of Supporting SprintEquipment at American Airlines Hangar#1O’Hare AirportChicago, IL 60666

The scope of services for this project includedthe preliminary investigation for the adequacy of the existing trusses, columns and pile foundations to support the new four prefabricated units and their supporting system at American Airlines Hangar #1 inO’Hare Airport.Included in the scope of work for this project werethe field inspection and evaluation, alternativestudies, and recommendations.The following three alternatives were investigated:

Alternative 1: Supporting four Sprint prefabricated units on the Roof of the existing

American Airlines Hangar #1

  • Preliminary analysis of the new four prefabricated units supporting system to be installed on the roof
  • Preliminary analysis of the existing trusses, columns, beams and pile foundations under existing and new loads

Alternative 2: Supporting the new Sprint equipment on the 3rdFloor

  • Preliminary analysis of the existing trusses, columns, beams and pile foundations under existing and new loads

Alternative 3: Supporting the new Sprint equipment on the 2ndFloor

  • Preliminary analysis of the existing trusses, columns, beams and pile foundations under existing and new loads

The structures(bridges and walls)are on a 13 mile stretch along the Regan Memorial Tollway Mile Post 126.9 (Washington Street) to Mile Post 139.1 (York Road). HBM preformed bridge inspections and preparation of the bridge condition report with rehabilitation design plans were completed.

The columns at Gridlines K and O are W36x260 and encased in concrete. Each column is supported on a pile group consisting of (16)-40 ton capacity concrete piles.

A Finite Element Analysis (FEA) was performed using SAP 2000. Finite element models were developed to reflect the true geometry, stiffness and loads on the structure. A 3-dimensional model was generated for the hangar with the addition of a supporting platform for the Sprint prefabricated units under existing and new loading conditions. The results for the supporting floor members of the 2ndand 3rdfloors were utilized in investigating the adequacy of the existing floors in supporting the Sprint equipment on either the 2ndor 3rdfloors.

As a result of the investigations, all three alternatives wereconsidered viable. The additional construction cost for the supporting platform and prefabricated units (materials, labor and handling) of Alternative 1wasjustified as it would result in no loss of storage space and transfer of loads from the platform directly to the columns and piles. Alternatives 2 and 3 werealso viable. Under Alternatives 2 and 3, the equipment wouldbe installed on a new structural support system spanning between the floor beams to carry the proposed load. The disadvantage of these alternatives wasthe loss of storage space

Analysis of the variations of each design alternative was performed. The resulting axial load-bending moment (P-M) interaction ratio for the columns, truss members and core area membersof both models wereall less than 1.00 under existing and proposed loads. The total governing applied load on the pile group was1247 kips which wasless than 1280 kips (the total foundation capacity). The applied load representedapproximately 97% of the total capacity.

Year Studied: 2007
Prime Consultant:
TRUSSNETUSA, INC
Subconsultant:
HBM Engineering Group, LLC