Thermal Expansion and Structural Engineering
Published on February 24, 2021 Chris Nicholson, P.E. Project Director at Ensight Haynes Whaley, LLC
Considering the recent cold weather that hit the area, it important to understand that all construction materials will undergo a certain amount of thermal expansion and contraction during the lifespan of the member. This is particularly important during the construction and erection process of the structure as during this time, many structural elements are often left exposed to the elements for multiple months until the building can be dried in and conditioned. During an extreme weather event and wild temperature swings, the members can see drastic thermal changes, leading to potential warping and/or structural failures. In theory, an individual 50’-0” long steel member can see approximately 3/8 of an inch of expansion or contraction over its length during a 75-degree temperature difference depending on if the temperature increases or decreases. Under the same conditions, a 300-foot building section that has been rigidly attached with steel beams and metal deck may see approximately 2 inches of thermal expansion or contraction.
Here in the southern regions, these types of temperature swings do not occur very often but are sometimes unavoidable. Within a weeks’ time, the Houston area underwent an approximate 60-degree temperature swing between the daily high and low temperatures. On Tuesday, January 9th, the Houston area saw an approximate high temperature between 75 and 80 degrees. One week later, Winter Storm Uri brought in freezing cold temperatures dropping the temperature in the Houston area to temperatures below 15 degrees. If construction materials were installed over this period, the individual end connections of the members may have undergone damaging tension and/or compression forces that the connection may not have been designed to resist. These forces get transferred to the overall building system, which may result in several inches of thermal movement in the entire system. What a difference a week can make!