Designing Weldments. Группа авторов

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      Preface

      The idea of writing about the specifics of weld design has been in my mind for nearly all through my career. The concept of the Designing Weldments was inspired, and motivated by my experience with engineers that were often responsible for designing major structures for offshore platforms, PLEMS, risers, roads and bridges, and buildings etc.

      Most of the time very excellent design concepts got bogged down due the limited knowledge the of the impact welding does on materials’ behavior, and how a welded structure is different from other materials say, an extruded structural member.

      The subject is also complicated by the fact that different types, and grades of material have different metallurgical response to the fabrication processes, including welding which is a major component of such complex fabricated structural members. The details of metallurgical aspects of material is discussed in another book Applied Welding Engineering (ISBN 978-0-12-821348-3) published by the Elsevier publication. Interested readers are encouraged to read and reference this book.

      While the basic engineering principles related to loading, and stresses remain same, as for the design of any other structural member, the presence of weld changes the stress locations, stress direction, and develops stress concentration points. This significant change, demands different approach to the calculations, and providing for those specific conditions. A structure with weld is no longer a straight forward member. The presence of weld in a structural member is not all that bad news, welds are complex part of any structure, with good understanding of them, welds can be designed to be useful and contributing part of any structure. Welds can, and are also used to strengthen and stiffen any structure. The knowledge of all these attributes helps improve the design of welded structures.

      This book discusses properties of materials, as structure sensitive and insensitive properties, and how these properties affect the integrity of the structure, and how to evaluate these sensitive properties of material and use them to the advantage in design evaluation.

      The book further discusses the design load conditions with various joint configurations, and placement of welds, and with the consideration of how they have been made, and inspected.

      Weld types are discussed in details, and how the load is distributed through these welds. Where in the structure is the primary stress? What type of primary stress working on the weld? What is the stress category? These are all discussed and graphically shown for easy understanding.

The chapters also discusses the nomenclature of welds, especially that of fillet welds. The use of complex joint designs, and their application in tubular connections. And factors that affect such complex designs. Structures are not only made of steel, and iron, other materials are also used for structures, aluminum is other most common material used for construction. The properties and grades of aluminum is explained in the chapter. The unique properties of aluminum brings in other design challenges that needs engineers and designer’s attention.

      A weldment cannot be without welding, a basic introduction to most common cutting and joining process is introduced in the book. For more detailed information of arc welding process, readers are direct to another book Arc Welding Process (ISBN 978-1-119-81905-9), published by Scrivener Publishing.

      The knowledge of these welding specific structural challenges are often missing, or at least available in limited form, to the engineering and design groups. This deficiency is often filled by an experienced welding engineer. If no such help is available at the design stage, then those deficiencies are identified at the fabrication shop, and then corrective action, and reverse engineering ensues, causing costly repairs and delays. In the extreme cases if those design deficiencies are not caught intime and corrected, they lead to the structural failures. Often such failures occur several years in the service of the structure, and at that point very little can be attributed to the design failure. Phrases like “weld failed” and “weld became hard” are often used to pass of the cause of failures, pinning responsibility on welders, rather than finding if the weld was designed correctly.

      There are number of construction codes that address these issues, some of them are mandated as national standards, AWS D1.1 and W59 in Canada are the examples, but there are several segments of fabrication, and construction that do not fall within the construction codes’ scope or jurisdictions. And there are also places where there is no national building codes to get any guidelines. The details of joint configurations, and its impact on the integrity of the designed structure can be determined before any fabrication or construction begins, and suitable modifications can be incorporated in the design, and shown on the construction drawings. That includes, inclusion of welding related instructions, use of universally accepted and understood welding symbols to specify specific types of weld edge preparations, necessary inspections (NDE), and use of specific welding procedure, distortion control, and necessary heat treatment, where it is required.

      Designing Weldments intends to fill that serious gap, or at least bring awareness among engineers and designers to seek help of an experienced welding engineer when planning to design a structure, or replacing a cast, forged, or wrought component to a welded component.

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