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"EXCEPTION: Unless otherwise required by the building official, buildings or portions thereof which are constructed in accordance with the conventional framing requirements specified in Chapter 25 of this code shall be deemed to meet the requirements of this section. "(b) Rationality. Any system or method of construction to be used shall admit of a rational analysis in accordance with well-establlshed principles of mechanics." These sections specify two concepts for the design of wood construction. A. The general case requires calculated systems using 2303(b) to resist loads references in Sec. 2303(a). B. Section 2303(a) Exception, permits deviation from the general rule and allows the building official to authorize construction with minimum calculations using conventional framing requirements as specified in wood, Chapter 25. C. A third alternative found in Section 107 allows the building official to test prototypes. If the prototype sustains the loads required by the code, others built to the same plan and specifications can be authorized. Much construction is designed to "B" above. Truss designs are not specified in the conventional f~amlng requirements and so must be designed using either "A" or "C". Conventional framing uses "rule of thumb" principles. Larger members are substituted with large factors of safety in lieu of detailed analysis and understanding of the way the building carries load. In contrast, the general case requires rigorous analysis and understanding of the way the building carries load. The amount of ~aterlal is reduced and the safety factors are smaller. Trusses fall in the design category. Materials are used sparingly and more sophisti- cated principles of physics and mechanics are used to carry the loads with special attention to connections. Answer.tO Question 3: There are no specification truss designs in the Structural Specialty Code. Trusses are designed using engineering design principles and the allowable unit stresses for the materials. For wood these are specified in Tables in Chapter 25 (see Sec. 2504 SSC). Connectors are specified in Section 2510. ~ach type of connector references one of the standards in uniform Building Code standards. UBC Standards is a companion document to the Uniform Building Code which is adopted at the same time as the uniform Building Code and is part of the Oregon Structural Specialty Code. Standards, a building official cannot effectively regulate truss const~uctioq., ............... (. ,)