Design Value Comparison: USA, Canada & Europe

Many products developed in Europe are available to the mass timber market in North America. Consequently, some designers may attempt to use design values from European Technical Approvals (ETA) for new connection systems that have yet to acquire ICC or CCMC approval in North America. Design values for European, American, and Canadian building standards, however, cannot be directly translated from one to the other.

The following examples, while not exhaustive, outline a few of the broad differences between the American, Canadian, and European design codes:Design Values Comparison V3

The Eurocode design equations reference a characteristic 5th percentile wood density with a 12% moisture content, while the NDS and CSA O86 reference a unitless specific gravity or relative density for a given wood species based on mean oven dry volume and mass measurements.

European mass timber hardware suppliers often provide design guides based on “characteristic design values” or sometimes “ultimate resistance values (Fu)” for the North American market. Characteristic design values are tailored to the EC5 design methodology and, unless adjusted properly, not suitable for design in North America. Using characteristic design values in standard connection resistance equations within North American design standards may lead to non conservative design or leads to overestimating connection capacity. In some cases, characteristic design values yield up to 100% higher capacities when compared to properly applied North American design values. For some specific scenarios in US design following the NDS methods up to 200% of difference can be found.

Ultimate resistance values should not be used in any design equation without the proper knowledge of how to deal with ultimate values and knowing how the ultimate values were derived from testing. However, mechanical models developed in Europe, such as those found in the annex of ETA-11/0190 may be used with North American design values, since they are based on basic mechanical principles that may be applied to specific material properties.

MTC Solutions provides reliable and tested design values that are available for North American design standards. All design values listed in MTC Solutions design guides are appropriately presented to meet design requirements of North American design standards. All presented design values are derived from respective testing in compliance with local standards.

 

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