The Ingalls Building: The World's Enforced Concrete Skyscraper

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INTRODUCTION
The Ingalls Building is the world’s first reinforced concrete skyscraper, and is renowned for its construction methods in the use of reinforced concrete. The Ingalls Building is located in Cincinnati, Ohio, and is named after Melville E. Ingalls. The building was designed to house office spaces and is 16 stories or 210 ft. (64 m) tall (1). Construction on the building began on October 2, 1902 and concluded July 1903. It was designed by architects Alfred O. Elzner and George M. Anderson. Henry N. Hooper, a structural engineer, was the contractor. The Ingalls Building was named a Historical Landmark by the American Society of Civil Engineers (ASCE) in 1973. This report discusses two of the cutting edge techniques
used to reinforce the concrete, why the ASCE recognized the Ingalls Building, and the benefits of using reinforced concrete in the skyscraper. Ransome’s patented twisted steel bars were used to reinforce the monolithic beam and column systems. Two-way reinforcing systems were used on the floor derived from the work of Josef Monier and Gustav Adolf Wayss. Lastly, the benefits of using reinforced concrete and the Ingalls Building lasting impact will be discussed.
THE USE OF RANSOME’S MONOLITHIC BEAM COLUMN CONSTRUCTION
The Ingalls Building used a monolithic beam and column design to support the weight of each floor which allowed for the structure to reach the height of a skyscraper.
The concrete for the slabs, beams, and columns for each floor were all poured at once and Ransome’s twisted steel bars were used in vertical and horizontal reinforcements. The column sizes were different depending on where on each floor a column was located and the load bearing strength it possessed. Between four and ten of these twisted steel bars would be placed inside of the columns. These reinforcing bars helped to resist tensile strains from wind pressures and the stress from the floor loads (2). The strength that the walls and columns were granted due to the reinforcing steel bars allowed for the Ingalls Building to be 210 ft. (64 m) tall. This framing system was used to handle different maximum loads as the floors went up. The first floor could resist a load of 200 pounds per square foot, the second floor could support a load of 80 pounds per square foot and the rest of the floors up to the roof could sustain a load of 60 pounds per square foot (3). The roof load was 40 pounds per square foot. (3). The steel bars hooked together to balance the weight that the concrete frame could support. Ernest Ransome’s twisted steel bar patent from 1884 shows how they were used in construction of the Ingalls Building. The left image shows how the bars were placed within the columns and the right image is of the
twisted steel bars (Figure 1). FIGURE 1 Ransome’s patent.
The tallest concrete building constructed prior to the Ingalls Building was six stories high because it was believed that the concrete would crumble under its’ own weight. Reinforcing the walls and the columns on each floor allowed for the structure to reach new heights.
TWO-WAY REINFORCING SYSTEM
Flooring in the Ingalls Building was created with slabs that had a two-way reinforcing pattern that strengthened the concrete to deal with crushing and shearing forces (3). This technique was borrowed from Josef Monier, who in 1877 patented reinforcing concrete girders with iron rods made into a two-way grid. In the construction of the building the footings that are near to more than one column are reinforced with the two-way grid system. The wind loads that could cause the shearing and bending of the concrete are thwarted by the diaphragm action of the floor, wall supports and their monolithic system. The diaphragm structure transfers the forces that would act on the upper part of the building down to its foundation (3) (4). Using Monier’s system allowed for the Ingalls Building to reach 16 stories high and the structural engineers would not have to worry about the high height and the effect of the wind on the tallest parts of the building. All of these construction methods acting together allowed for the footings and columns of the building to have a maximum bearing capacity double the actual load of the footings. (3). Pictured is the two-way grid that is used to provide reinforcement for the floor. The construction workers are laying the concrete mix over the bars (Figure 2). FIGURE 2 Two-way reinforcing floor slab system with concrete to be poured.
BENEFITS OF REINFORCED CONCRETE AND INGALLS BUILDING LASTING IMPACT
There were many methods of using metal to reinforce the concrete utilized in the Ingalls Building construction to avoid the negative effects of building with concrete. The Ingalls Building is mostly concrete and metal was placed within the concrete to strengthen its load bearing properties. Much of the architecture of the time was heavily made up of steel and would be completely destroyed in fires. Concrete proved to be a more flame resistant material than steel as evidenced by its use in the factories of the time (5). The use of concrete also allowed for the aesthetic appeal of the Ingalls Building to be seen while providing strength and support. The exterior of the Ingalls Building is made up of marble and brick with terra cotta trim. On each floor the outer brick layers are secured by wire anchors coming out of the concrete ledges (2). The way the marble and terra cotta trimmings were laid provided grooves in the back of them that connect with the concrete surface of the building to form a kind of dovetail joint (2). Reinforced concrete had been used in construction before but in buildings that were long not tall. Many people believed that attempting to construct a skyscraper of this height out of concrete would be disastrous because the material was heavy and wouldn’t support its own pressure. As a result it took Melville Ingalls two years to be granted a building permit (1). The Ingalls Building demonstrated that concrete could be used in the construction of high rise buildings despite the fears of the time.
CONCLUSION
The Ingalls Building utilized cutting edge construction methods in a new way and became the first reinforced concrete skyscraper ever erected.
The groundwork laid by Ransome, Monier, Wayss and others was utilized by Henry Hooper to create the building that is still standing today. The Ingalls Building, now known as the Transit Building (3), still stands in Cincinnati today at the corner of 4th Street and Vine Street. The monolithic beam-column construction and the two-way reinforcing system worked together to showcase the benefits of using reinforced concrete in the construction of large scale buildings. The Ingalls Building paved the way for skyscrapers today which use reinforced concrete to achieve great heights. For example, the Petronas Twin Towers in Kuala Lumpur, Malaysia which stands at 1,483 ft. (452 m) high (5). The innovative knowledge gained during the design and construction of the Ingalls Building has been built upon and used in present day construction
projects.
REFERENCES
1. Ingalls Building. http://www.asce.org/project/ingalls-building/. Accessed September 6, 2017.
2. The Ingalls Building—The Largest Concrete Office Building in the World. Scientific American, Vol. XCIV, No. 19, 1906, pp. 394-395.
3. Conduit, C. W. The First Reinforced-Concrete Skyscraper: The Ingalls Building in Cincinnati and Its Place in Structural History. Technology and Culture, Vol. 9, No. 1, 1998, pp. 1-23.
4. Diaphragms and Shear Walls. APA- The Engineered Wood Association, Tacoma, Washington, 2007, pp. 4.
5. Ali, M. M. Evolution of Concrete Skyscrapers: from Ingalls to Jin Mao. Journal of Structural Engineering, Vol. 1, No. 1, 2001.