Six “S” Elements for Success in Structural Engineering

Essential Structural Engineering derives its name from playful similarity to the sound of “Six S’s.” Our founder has realized that every successful structure incorporates the 6-S’s. The 6-S’s are: Stability, Strength, Stiffness, Serviceability, $ustainability and Schedule. The seventh S is the Satisfaction that client and engineer experience from a successfully executed project.

The following six elements are essential to the success of of all structures:


Every successful structure must be conceived in a stable configuration that includes sufficient bracing. All structural loads must have complete load paths to transfer the loads to the ground. Structural engineers apply a special case of Newton’s 2nd Law of Mechanics: rather than equalling mass times acceleration, the summation of all forces equal zero. Before determining any loads, calculating any forces, or designing any beams or columns, the structural engineer must define a structure geometrically with a framework to withstand what will be imposed on it by humans and nature. Per Henry Petroski’s To Engineer is Human, “each building or bridge may be considered to be a hypothesis” whose success may never be proven, but without a stable configuration, a structure would have no chance of success.


Every successful structure must be designed with components that possess adequate strength to resist the loads imposed on it. Based on the loads and geometric layout of structure, the engineering team will determine the basic structural materials that are best suited for the application. Structures usually have a predominant material (steel, concrete, masonry or wood), but there may be hybrids of multiple materials. Structures may include less common materials, such as stainless steel, aluminum or plastics.


Every successful structure must be proportioned such that it responds to its applied loads without excessive deflections or movements. While being relatively small and undetectable, structural deflections are unavoidable, but they can be minimized. New structures are designed to limit deflections within accepted industry standards. Excessive deflections could cause doors and windows to stick, could cause walls and ceilings to crack, could cause annoying contours or movements within floors, and could be responsible for uncomfortable or frightening vibrations.


For the successful structure to perform in the intended way, its design must incorporate the applicable details and specifications. Properly positioned expansion joints allow appropriate movement within a structure and prevent excessive stress due to temperature variations within buildings. The structural engineer specifies materials and details so they do not deteriorate at an unacceptably rapid rate. If required by the usage of the facility, floors must meet stringent criteria for flatness and levelness for proper performance of equipment. Concrete slabs must have expansion and contraction joints to prevent unsightly cracks that would otherwise form randomly.


There are many methods of measuring the cost of a building structure, but the most sustainable structures are those that minimize the full life-cycle costs. For the most part, structural systems have recognized sustainability properties in that most construction materials are recycled or recyclable. For instance, steel has high contents of recycled metal and concrete can be made with slag and fly ash as partial replacements for Portland cement. Adaptive reuse of existing building stock capitalizes on the internal energy already in the facility. Roofs can be designed or reinforced to support the weights of green roofs, cisterns and solar energy arrays. Cost-effectiveness of a structure should consider the totality of a project, wherein a more expensive structural system may be more beneficial to the project because it offsets other costs. Estimating the cost of a project solely on the basis of tonnage of structural steel or cubic yards of concrete may not reveal the full lifetime cost of a project. Utilizing repetition rather than optimizing the weight of every beam could cost less to build because of ease of detailing, fabricating and erecting a structure.


Every successful structure has an associated time schedule. There are many time-dependent factors to a project, such as the time to design and coordinate a project, the time to procure and fabricate the materials and the time to construct and deliver the project. With timely advice from the builder, the structural engineer can design a project with preferred materials and details. For instance, a steel contractor may prefer single-sided shear-tab connections over conventional double angles; or a foundation contractor may prefer masonry foundation walls over concrete ones.


Every successful structure satisfies the above 6-S elements for success in Structural Engineering. By satisfying the 6-S elements for success in Structural Engineering, the structural engineer gains professional satisfaction; the owner is satisfied by the results of the project; and hopefully, the structural engineer is invited to participate in future endeavors of the project team.