Broad Art Museum
East Lansing, MI
Structural Design and Field Testing
The Broad Art Museum is located on the campus of Michigan State University, East Lansing, Michigan. The design architect was Zaha Hadid Architects, London, UK, the project architect was Integrated Design Solution, LLC, and the engineer was Structural Design Inc. The building is made of reinforced concrete. The museum houses two monumental stairs. One connects the basement to the first floor, and the other between the first and second floor. Both stairs have steel structures. The stringers are made of 12 in. Hollow Structural Sections with a total depth (end to end) of 37 in. The upper stair has a total unsupported length of 59 ft. – 4 in. measured along the outer stringer.
The flexibility of the structure as designed for static loads was of concern to the architect and structural engineer. VTL personnel conducted computer analysis of the structure and found that the stairs, as designed for static loads, were susceptible to large vibrations. The first mode natural frequency of the upper stair was 6.8 Hz. A number of modifications to the stairs' design were made, raising the natural frequency to 9.2 Hz.
Vibration testing of the stairs immediately after their installation was conducted. The measured natural frequency of the upper stair was 9.8 Hz.
Final vibration tests were conducted after construction. The measured first mode natural frequency of the upper stair was 8.6 Hz. A number of tests with a groups of people ascending/descending the stair were conducted. The measured stair vibrations were all within the acceptable limits.