Exploring Transition Buildings and Construction
Transition buildings’ was a term coined by post-transition historians that described the period when steel began to be utilized.
By Jeffrey S. Barnes, and Craig E. Barnes, P.E., S.E.
The term “transition building” was coined by post-transition historians. It derives from builders of that period utilizing steel to create greater building heights and floor spans. The word “skyscraper” had its origin in either New York or Chicago, but who holds bragging rights for the oldest skyscraper? Research suggests the oldest skyscraper is the 150-foot-tall Temple Court Building located in Manhattan and completed in 1883, while others declare Chicago had the first skyscraper—the Home Insurance Building, at 138 feet high, completed in 1885. Regardless of whether it is New York or Chicago for the home of the earliest skyscraper, one thing is certain—skyscrapers addressed a country that started booming socioeconomically and provided the need for more space.
Buildings transitioned from low-rise to high-rise seemingly overnight, and the technology had to keep up with the demand. Low-rise masonry structures grew to high-rise masonry structures that were load-bearing and could only be erected as quickly as the floors were constructed. In other words, the pace of building construction was, at times, directly linked to the pace of wall and floor construction. Thus, in colder climates such as Chicago, New York, and Boston, a high-rise could take 2 to 3 years to complete due to winter conditions. This was a costly and time-consuming process. Imagine being the owner of a 10-story masonry building and watching it take shape laboriously over a period of 2 to 3 years, maybe close to 4 years, before you can realize any return on investment.
But it was not just labor costs and time costs that drove technological advances: logistics also became a factor—material production (casting iron, firing bricks), fabrication (cutting steel to length, punching rivet holes), shipping, hauling (materials from railroad terminal to site) and placement (steel erection and bricklaying). In Boston, cement had to be brought in by train, which would add to the cost. Brick and stone required a large amount of space to fire and store prior to being used. As a result, that high-rise with a small footprint might have required 10 times its footprint of laydown space to be able to erect that high-rise, which added to the cost.
As demand for more space increased, the demand for the high-rise also increased, meaning more loads were introduced to the structure. As a result, masonry walls could no longer bear any more loads past a certain height. This is another reason why the steel frame came into play.
By the 1890s, three types of building technologies were available: bearing walls, cage frames (see sidebar), and skeleton frames. The bearing-wall building has thicker walls at the bottom and thinner walls at the higher sections of the building. This framing required interior masonry walls to support the floors above. The cage-framed building was a hybrid where the masonry walls provided lateral resistance to wind, and the steel frame directed gravity loads to the ground. The masonry walls in cage-framed buildings were slightly thinner than in bearing-wall buildings. Some interior masonry walls required for cage framing were replaced with cast iron columns. The skeleton-framed building had connecting steel beams and columns that supported the gravity and lateral loads; the masonry walls did not contribute much structurally and remained at a constant thickness from top to bottom. This concept is the precursor to today’s high-rise buildings.
Donald Friedman, president of Old Structures Engineering and a structural consultant in historic and old buildings, created a model to illustrate typical costs of the three types of building technologies available in the late 1890s. The models are 13 stories and do not include interior finishes, stairs, windows, or elevators; they are just the basic structure. Based on data for construction at that time, a 71 bearing-wall building may contain 4,900 tons of brick and 180 tons of steel for a bare structural cost of $122,000. A cage-framed building may require 2,600 tons of brick, 82 tons of cast iron, and 250 tons of steel for a bare structural cost of $80,000. A skeleton-framed building may need 1,800 tons of brick and 520 tons of steel for a bare structural cost of $74,000. As a building owner, opting for the more cost-efficient technology is a no-brainer and allows for a building with greater capacity than a bearing wall structure.
As the economy transitioned and began to grow, high-rise structures did, as well. These thinner buildings with smaller footprints allowed for a great number to be erected in a shorter amount of time and to greater heights as the country underwent rapid expansion, doubling the total cost of construction from $31.5 million in 1860 to $76.0 million in 1890. Builders were also transitioning in different ways as the building industry began to understand the benefits of rolled steel wide-flange sections, with a greater variety of shapes being provided.
Metals Used in Construction
Often confused but often not the same are wrought iron, cast iron, and steel. Wrought iron, with less than 0.1% carbon (mild steel) and less than 0.36% carbon (hard steel), is a commercial form of iron that is tough, malleable, and relatively soft for easy tooling. This form of wrought iron is often used in non-structural items such as tables and chairs. Cast iron, with a chemical content ranging between 2% -4% carbon and 1% -3% silica, is iron that has been melted, poured into a mold, and allowed to solidify. Cast iron, partially because of its poor tensile strength, is found more often in transitional structures as structural columns and cast as pintles. Pintles are frequently found in heavy timber construction, where they are used to transfer timber column loads at floor/ column joints. In addition, cast iron is very brittle, which makes it hard to shape or machine. Structural steel is an alloy or a combination of iron and other alloys such as carbon, manganese, nickel, copper, etc. To make the desired grade of steel, typically less than 2% carbon is added to iron, and the rest is made up of many other elements. When onsite, if you have any doubts about which material is present, strike the metals with a grinder, and the change in spark quantity will be the giveaway—the more spark, the higher the carbon content.
All iron ore-based products are produced through the process of smelting. The smelting process requires iron ore (of which there are different grades found in nature), coke, and limestone heated to melt the metal out of the ore. Young engineers should become familiar with the process. A familiar product that results from the smelting process is slag. Although largely a waste product, slag, which contains metal oxides and silicon, is improving its image as it is being used in a variety of highway products, including additives to concrete. Production smelting that engineers are familiar with originated in two- or more-story high vertical blast smelters that were shaped like an open-topped milk bottle and lined with refractory material (that resists high heat). The more efficient Bessemer converter superseded the vertical blast furnace, a larger, more rounded metal container lined with refractory material. This was replaced by the more efficient electric arc furnace, first utilized in France in 1907.
In the late 1800s and early 1900s, there were many small steel fabricators producing structural steel sections. These fabricators produced their own catalogs of available structural sections (Figure 1). Examples of these early fabricator catalogs are Wrought Iron & Steel 1884, Pencoyd Iron Works 1891, Carnegie, Phipps & Co.-1892, Bethlehem Steel pamphlet 1907, and the Bethlehem Steel blue book 1911. Another interesting tidbit is that steel at that time could have a 50 kips per square inch (ksi) ultimate tension strength and an Elastic Modulus of 30 ksi. Uniform safety factors were not universally accepted. One of the catalogs recommended railroad bridge members be designed to 1/5 of the ultimate steel value, highway bridges to 1/4 of the ultimate strength value, and roof trusses to 1/2 of the ultimate steel value.
In conclusion, this article barely scratches the surface of what transition buildings are and hopefully has interested the reader to continue their discovery.
Jeffrey S. Barnes is the Principal of Barnes Consulting Group LLC and may be contacted at
email@example.com. Craig E. Barnes, P.E., S.E., is also a Principal of Barnes Consulting Group LLC. (firstname.lastname@example.org)