The success of steel structures partly depends on the steel design and fabrication process. In structural terms, designing refers to the technical drawings that depict the overall look of structure. Designing goes hand in hand with fabrication, the process of converting raw parts to structures that can be used in the assembly process. Assembling is the series of operations through which the fabricated steel is added in sequence until the final product is obtained.
Steel Design Considerations
Designers must have good knowledge of the design specifications before they come up with a final design. It is essential to think of how everything fits together, whether it is through rotation, twisting, deflection, and so on. Steel designers should as well provide enough allowance for welding, bolting, and painting. For the integrity of structures to be maintained, designers should prevent the accumulation of debris or water on girders.
Weathering or non-weathering steel may be used depending on the application at hand. Weathering steel is a bit more expensive but the price is justifiable since it requires less maintenance and no painting. However, weathering steel should not be used in atmospheres with corrosive materials or salt-water sprays. Areas with high rainfall also affect weathered steel through the constant moisture.
Span configuration is also an important aspect of steel design and fabrication. For bridge applications, it is common to use two- and three-span structures. Designers should desist from use of four spans as this may destabilize the structure. Using too long end spans relative to interior spans also disproportionate the amount of steel used in end spans. Other factors to consider in design include flange thickness, flange width, web depth, and web-splice locations.
Steel Fabrication
Once the design is ready, steel fabrication ensues. This can be done on the site or in a fabrication shop. The first step involves cleaning the surfaces then cutting to the required sizes. Flame cutting, cold sowing, shearing, punching, and plasma arc cutting are common cutting practices. Rolling and straightening may follow if the pieces are distorted after the above preparation processes. Finally, finishing is done through milling sawing, smoothing, and surface treatment.
In addition to specification fulfillment, safety is an integral part of steel design. Poor structure designs have been the source of numerous workplace injuries and fatalities. Designers should reduce the possibility of falls, tripping or heat and cold stress. Designers can avoid injuries by establishing occupational safety and health goals as well as substituting hazardous processes. Control measures should also be included in the detailed design. All materials and processes used should be subjected to checks and tests to ensure conformity with operating standards.
