September 30, 2002 Structural Concepts / Structural Existing Conditions (S-1) Executive Summary: The building utilizes both concrete and steel to form the structural steel system. A concrete strip footing supports the walls, while concrete spread footings transfer the column loads to the ground. The basement walls are a combination of concrete masonry units and reinforced concrete walls. The basement and retail space on the first floor are slabs on grade, while the rest of the building uses steel framing to support the floors. Each floor is almost identical in framing with the exception of a few mechanical opens. The floor system uses simply supported composite beams that run in the east – west direction that frame into girders that run from north to south. The roof of the building is framed the same way as the floors, but does not use composite beams. Spliced columns take the floor loads down to the foundation and span all the way up to the roof. The building is designed for loads that are in compliance with the 1998 Ohio Basic Building Code and was designed using the Allowable Strength Design philosophy. To determine the loads the building was subjected to, I consulted ASCE 7-98. From this document, I got the minimum live loads, as well as the wind, seismic and snow loads. After determining the loads, I was a little surprised that the seismic loads control the design of the braces in the braced frames. After I determined the loads, I was able to spot check a few of the members. I selected a braced frame, floor beam and column below the 5 th floor. After performing some calculations, my designs were very close to those of the original designer even though I used LRFD. The exception to this was the brace. My size was much larger than the original design, because it was governed by the seismic load. After further reviewing the structural notes, I found that the original design used different assumptions in the seismic loads and was able to reduce the load by taking some special precautions and designing the members and connections specifically for seismic loads. After designing the member for wind load, my design was very close to that of the original design. In each case, my design was slightly smaller than the original design. I think that is a reflection on the advantages on using LFRD design vs. ASD. The structural framing system for 250 West Street utilizes a steel superstructure to carry the loads the building is subjected to and a concrete foundation to transfer the loads to the ground. The basement of the building allows for parking and storage and takes up about half of the footprint of the building. It consists of a slab on grade and reinforced concrete walls. The first floor of the building is composite beams in the southern half of the building where it was designed for office space. The northern end of the first floor is a slab on grade. The rest of the floors are almost identical. They have composite beams running in the east –west direction that
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September 30, 2002 Structural Concepts / Structural Existing Conditions (S-1) Executive Summary: The building utilizes both concrete and steel to form the structural steel system. A concrete strip footing supports the walls, while concrete spread footings transfer the column loads to the ground. The basement walls are a combination of concrete masonry units and reinforced concrete walls. The basement and retail space on the first floor are slabs on grade, while the rest of the building uses steel framing to support the floors. Each floor is almost identical in framing with the exception of a few mechanical opens. The floor system uses simply supported composite beams that run in the east – west direction that frame into girders that run from north to south. The roof of the building is framed the same way as the floors, but does not use composite beams. Spliced columns take the floor loads down to the foundation and span all the way up to the roof. The building is designed for loads that are in compliance with the 1998 Ohio Basic Building Code and was designed using the Allowable Strength Design philosophy. To determine the loads the building was subjected to, I consulted ASCE 7-98. From this document, I got the minimum live loads, as well as the wind, seismic and snow loads. After determining the loads, I was a little surprised that the seismic loads control the design of the braces in the braced frames. After I determined the loads, I was able to spot check a few of the members. I selected a braced frame, floor beam and column below the 5th floor. After performing some calculations, my designs were very close to those of the original designer even though I used LRFD. The exception to this was the brace. My size was much larger than the original design, because it was governed by the seismic load. After further reviewing the structural notes, I found that the original design used different assumptions in the seismic loads and was able to reduce the load by taking some special precautions and designing the members and connections specifically for seismic loads. After designing the member for wind load, my design was very close to that of the original design. In each case, my design was slightly smaller than the original design. I think that is a reflection on the advantages on using LFRD design vs. ASD.
The structural framing system for 250 West Street utilizes a steel superstructure to carry
the loads the building is subjected to and a concrete foundation to transfer the loads to the
ground. The basement of the building allows for parking and storage and takes up about half of
the footprint of the building. It consists of a slab on grade and reinforced concrete walls. The
first floor of the building is composite beams in the southern half of the building where it was
designed for office space. The northern end of the first floor is a slab on grade. The rest of the
floors are almost identical. They have composite beams running in the east –west direction that
Kevin A. Sponsler S-1
frame into composite girders. The floor system only carries the gravity loads because of the
presence of braced frames. There are 2 brace frames in each direction of the building that carry
the lateral loads. To complete the design, the roof, upper roof and penthouse roof all use non-
composite steel framing.
The building was designed to be compliant with the 1998 Ohio Basic Building
Code and was designed using Allowable Stress Design procedures for the design of the steel
framing.
In addition, the following codes were also followed:
Concrete
• ACI 301-96 – Specification For Structural Concrete For Buildings
Structural Steel
• AISC Specification For The Design, Fabrication and Erection of Structural Steel For
Buildings
• AISC Code of Standard Practice
• Structural Welding Code, AWS D1.1 of the American Welding Society
• Specification For Structural Joints Using A325 or A490 Bolts
Metal Studs and Joists
• AISI Specification of The Design of Cold-Formed Steel Structural Members
• Structural Welding Code, AWS D1.3 of the American Welding Society
The foundation of 250 West Street consists of concrete strip footings that support the
basement walls, spread footing to support the columns and some grade beams. The strength of
the concrete used in the foundation is 3000 psi, while the reinforcing bars have a yield strength
of 60 ksi. The strip footings range in width from 1’- 4” to 2’- 0” and have a depth of 12”. Each
2
Kevin A. Sponsler S-1
strip footing has 2 #4 reinforcing bars running continuously. Under each column are square
footing that range in size from 6’- 0” square and 18” deep with 6 #6 bars each way to 14’- 6”
square and 40” deep with 12 - #10 bars running each way on the top and bottom. There are also
several grade beams that run from the column footings on the exterior of the west side into
footings approximately 25 feet in from the west side of the building. Each grade beam is
approximately 3’- 0” wide by 4’- 0” deep with 6 #8 bars in the bottom and 17 #10 bars in the top.
The walls of the basement/foundation are for the most part concrete masonry units.
Twelve inch CMU’s are used in the perimeter of the foundation from the top of the footings to
the first floor. The only exception to this is the south, east and west walls of the parking area.
The construction of these walls are 12”, air entrained, reinforced concrete that has a strength of
4000 psi. The floor of the basement is a 4” slab on grade made of 3500 psi concrete.
The rest of the structure is framed with steel. The steel strengths are summarized in table