A structural analysis engineer is the person you will need to design a structure which must maintain loads exerted by its own weight, natural forces such as winds and earthquakes, and the loads or weights and movements of its occupants, such as people and their belongings in a building, and cars and trucks over a bridge.

Bridges Designed by Structural Analysis Engineers

A structure is a connected series of elements, such as beams, cables, pins, concrete blocks, columns, etc. The design of a structure is done in such a way that the whole is greater than the sum of its parts. That is, a comparatively light and inexpensive group of connected small elements can bear an extremely large load, or span an extremely large distance. For example, the Golden Gate Bridge spanning between Marin County and San Francisco replaced a fleet of ferries, and restored the growth of San Francisco as a great city. It spans a total distance of 1.7 miles, and when it was finished in 1937, it was the longest suspension bridge in the world. It held that record until the Verazzano Narrows Bridge was completed in 1964, which has a total roadway distance of over 2 miles. Both of them light up the night sky, and provide almost instantaneous access to travelers and commuters which formerly took hours. The value of this service can be measured in the original toll for the Golden Gate, which was $0.50, or $18 in today’s dollars.

The entire design of these two bridges, like an uncountable number of other buildings, bridges, cell towers, roadways, and even homes, was done by engineers using structural analysis. They were entirely designed on paper in order to confirm proposals and prices, and then the projects themselves took years to make a reality, after the structural analysis was checked and re-checked for safety, durability, endurance under all the many loads presented by nature and by human use.

Structural Analysis Process 

The structural analysis required by engineers to make these dreams and investments into realities is not limited to the final designs. Every stage of the construction of a suspension bridge must be analyzed by structural engineers to confirm that they are stable under the forces exerted at that time. The towers must be built before the main cables are strung, but the towers themselves are usually constructed using pressurized caissons, which are tanks open at the bottoms, and lowered to the bottom of the bay or river,  pressurized enough to equalize the surrounding water pressure. Every day the workers in these caissons must undergo slow pressurization and de-pressurization like deep-sea divers to prevent “the bends” when they emerge, which can kill them if this is not carefully done. The caissons themselves, which are not a part of the final design, and do not remain in the water permanently, are products of structural design engineering.

Even one crane mounted on the deck to lower sections of the trusses supporting the roadway into place must be checked for forces like overturn, which could throw the crane and its occupants into the freezing waters below if the load it picks up creates a moment which displaces the center of gravity of the machine outside of its own footprint.

Structural analysis engineers are seldom recognized or thanked, but if there are errors in their calculations and plans, hundreds or thousands of lives and livelihoods are suddenly threatened. When the Verrazzano Narrows Bridge was built, three men fell to their deaths without any safety net under the bridge to catch them. After the third builder was killed, workers went on strike until a safety net was installed. After that, there were no more deaths. A bridge over a deep river gorge in Tennessee failed during construction because the main I-beams were extremely deep with narrow steel webs. They were stabilized with struts at the final end of construction, but before these struts were installed, the I-beams failed in “Lateral Torsional Buckling,” or “LTB, ”during a windstorm.

According to the authors of a Science Direct article, over 30 bridge accidents have occurred in China in “Recent Years,” but few if any have been officially investigated. (Analysis for Yangmingtan Bridge collapse – ScienceDirect) The failure of the Yangmingtan bridge caused 3 deaths, 5 injuries, and 4 falling vehicles. The authors stated that the failure was predictable using Structural Analysis Engineering principles and disciplines, like frame node analysis. Jobs using Structural Analysis Engineering principles are demanding, but experts are in high demand because of the challenging connection between high levels of mathematical analysis and practical administration of details.

Areté Provides Structural Analysis Engineering Services

Do you have questions about structural analysis engineering? Areté Engineering does structural engineering design of homes and commercial buildings, and bridges, and Areté Structures designs and builds Fiberglass Reinforced Polymer pedestrian bridges. Areté Infrastructure division designs and inspects major and minor bridges throughout the Southeast. Come visit us at: Home – Areté Engineers