Architecture is defined as the art and science of designing and successfully executing structures in accordance with aesthetic considerations and the laws of physics, as well as practical and material considerations. Where tubular structures are exposed for dramatic effect, it is often disappointing to see grand concepts fail in execution due to problems in the structural connections of tubes. Such "failures" range from awkward ugly detailing, to learning curve problems during fabrication, to excessive deflections or even collapse. Such failures are unnecessary, as the art and science of welded tubular connections has been codified in the American Welding Society (AWS) Structural Welding Code [1]. The AWS design criteria have also been incorporated into the American Institute of Steel Construction (AISC) Specification for the design of steel hollow structural sections [2].

A well-engineered structure requires that a number of factors be in reasonable balance. Factors to be considered in relation to economics and risk in the design of welded tubular structures and their connections include (1) static strength, (2) fatigue resistance, (3) fracture control, and (4) weldability. Static strength considerations are so important that they often dictate the very architecture and layout of the structure; certainly, they dominate the design process and are the focus of this chapter. Many of the other factors also require early attention in design, and it is of benefit to set up quality control/quality assurance programs during construction; these are discussed further in sections of the Code dealing with materials, welding technique, qualification, and inspection.

The designer of record is responsible for structural connections and should not attempt to abdicate his responsibility by placing a ''Truss Note'' on the drawings such as "All welded truss connections shall develop the full axial capacity of each member at a stress of 0.6Fy.'' The fabricator might simply provide matching weld sizes and let it go at that.

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