Reliability-based design of mechanically connected built-up wood columns

Abstract

Built-up wood structural components and systems have been in use in the building industry for decades. Though easy to construct, they are rather complex to analyze because of numerous factors affecting their strength and behaviour. This paper explains the development of a reliability-based design formulation in limit states for built-up columns, using a rational mathematical model for the analysis and design. Also, a brief discussion is given on a set of simplified design rules for layered columns which have been incorporated into the Canadian Standards Association Standard CAN3-086.1-M89 "Code for engineering design in wood (limit states design)." The rational model as well as the simplified rules are subjected to reliability analysis.The Canadian specifications for the design of wood structures in limit states format have been available since December 1984. These specifications are essentially a soft conversion of the previous working stress design code. The 1989 edition of the code is mostly based on the principles of reliability-based design. Some portions of the code are still not fully based on reliability approach, as additional information is needed for the establishment of a reliable data base upon which the "uncertainty factors" could be redefined in a more rational and logical manner. This paper provides that type of information and the details of reliability analysis as applied to mechanically connected built-up timber columns. The reliability analyses are performed based on first-order second-moment methods, using a data base of column strengths. The data base consists of experimental as well as simulated results. Two reliability analysis programs, BUCREL (built-up column reliability analysis) and POINT (reliability analysis using design point algorithm), are developed. Design recommendations are derived in a reliability-based design format. Key words: buckling, columns, design specifications, efficiency, joints, layered columns, rational model, reliability, resistance factor, slip, spaced columns, timber, wood.

Resistance Factor Spectra for the Ultimate Limit State of the National Building Code of Canada

“…The next version of the code, CSA-086.1-M89, "Code for engineering design in wood-limit states design," was largely reliability-based. In 1991, Malhotra and Sukumar [10] developed reliability-based design formulation in limit states for mechanically connected built-up timber columns. The authors used experimental data and simulations to perform reliability analyses that were based on first-order, second-moment methods.…”