What do Structural Engineers do?
When the preliminary design work is completed, the size and shape of the building is set and the finishes are selected, the structural engineer can begin their work. They tabulate the vertical loads from building materials, occupants and contents and select the appropriate sizes and strengths of supporting members. They establish and design to limits which prevent the wall finishes and ceilings from cracking. They work with geotechnical engineers to limit the settlement of buildings. They check for floor vibrations ("bounce") so pedestrians feel comfortable walking on them. Wood, Concrete, Masonry, Steel, Aluminum, Epoxies, Light-Gage Metals, and Composites are a few of the materials that structural engineers use in their practice.
While vertical loads are important, "lateral" loads from high winds, earthquakes or retained soil are where structural engineers earn their keep. Using the applicable building code, they match forces with resisting elements from the roof to the footings. Walls are checked to assure they support the load from floors and the gusts from severe storm winds. Structures are bolted to their foundations to resist the lateral sliding forces of earthquakes. Basement walls are designed to span between floor levels to resist the pressure of the soil.
The structural engineer is responsible for translating his or her calculations into construction drawings for the contractor to use. Plan views of the individual building levels are developed. Details of the various connections are created and described on these plans. Specifications for the structural materials and required inspections are added. If the mechanical engineer places a large air conditioning unit on the roof, they plan for its support. If the architect would like skylights, they provide the openings. No condition that affects the performance of the building escapes the structural engineer.
In the field, structural engineers assist the contractor by accommodating preferred construction methods. Although engineers endeavor to select the most efficient methods during design, field conditions and economic factors influence every project. Proposed alternates are reviewed against job requirements, calculations and codes; then approved or rejected on that basis. When problems or errors in assembly arise, the structural engineer reviews the on-site conditions then makes recommendations for corrections. Should a test from a material sample not come up to specifications, they decide if portions of the building should be reinforced or removed and replaced.
At the end of the job, the structural engineer has very little to look at. The design they created is now covered with finishes. Should it perform to expectations, their name will rarely be remembered. The satisfaction of transforming a concept into a tangible object which serves and shelters its occupants is their reward.