MBTA Park Street Station

Park Street Station is the oldest subway station in the United States.  As part of a system-wide upgrade of light rail transit stations for improved accessibility, the Massachusetts Bay Transportation Authority (MBTA) needed to make structural modifications, which included removing columns that were too close to the edges of platforms.  SGH assisted the contractor by reviewing the proposed shoring requirements and suggesting alternate means and methods that allowed them to successfully accomplish the work.

Scope | Solutions

The contract design called for temporarily shoring large areas of the roof while new footings, columns, and roof framing were installed.  The structure consisted of an unreinforced concrete jack arch roof supported by steel beams, girders, and columns.  The roof supports up to 3 ft of fill.  The columns are supported on stone and concrete spread footing foundations.  Highlights of SGH’s work include the following:

  • Provided an evaluation of the contract plan design and implementation
  • Identified risks and technical problems with the contract plan design
  • Proposed an alternate design that eliminated the need for temporary shoring and multiple load transfers
  • Designed strengthening for existing columns and foundations to support column loads that would increase by 50 to 100 percent once the intermediate columns were removed and remaining columns were loaded
  • Prepared an instrumentation plan to monitor structural strains and displacements during jacking and column cutting operations
  • Monitored vibrating wire strain gauges and displacement dial gauges to confirm satisfactory preloading of the new girders and to verify that roof movements did not exceed 0.125 in. from the position at the start of work

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