Connection Options for Wood-Frame and Heavy Timber Buildings

Strategies for achieving energy objectives with wood-frame structures
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Design Guidance for Effective Connections

Connections obviously need to provide the structural strength necessary to transfer loads. As discussed above, well-designed connections also mitigate potential adverse effects of moisture ingress. Finally, well-designed connections minimize the potential for excessive tension perpendicular to grain stresses—under design conditions as well as those related to unusual loading conditions. Chapter 10 of the ASD/LRFD Manual provides details for a variety of design configurations (e.g., beam-to-concrete or masonry wall connections and beam-to-beam connections). Many begin with a brief discussion of the pertinent design challenges. For example: Beam-to-Concrete or Masonry Wall Connections Design concept: Concrete is porous and “wicks” moisture. Good detailing never permits wood to be in direct contact with concrete.

Five Stories and Higher

With the exception of height, the outward appearance of mid-rise wood-frame buildings has not changed a lot over the years; however, the quality and precision of design and construction has increased considerably. Connection-related design aspects that are more critical in a five- or six-story wood-frame building include accommodating greater dead, live, wind and seismic loads, which increase with the additional height.

Going from four to six floors, for example, increases the gravity loads by 50% but lateral forces due to wind or seismic forces may actually double.

While the size and capacity of connections might change and designers may use more specialized, high-capacity connectors, the connectors themselves are largely the same as they are for any light wood-frame building—nails, bolts and lag screws used with and without proprietary connectors.

Continuous tiedown systems are often used in multi-story wood shear wall construction for resisting wind or seismic overturning loads.

Beam on shelf in wall. The bearing plate distributes the load and keeps the beam from direct contact with the concrete. Steel angles provide uplift resistance and can also provide some lateral resistance. The end of the beam should not be in direct contact with the concrete wall.

Source: American Wood Council

Beam on shelf in wall. The bearing plate distributes the load and keeps the beam from direct contact with the concrete. Steel angles provide uplift resistance and can also provide some lateral resistance. The end of the beam should not be in direct contact with the concrete wall.

Similar to detail A with a steel bearing plate only under the beam.

Source: American Wood Council

Similar to detail A with a steel bearing plate only under the beam.

Similar to detail A with slotted holes to accommodate slight lateral movement of the beam under load. This detail is more commonly used when the beam is sloped as opposed to flat.

Source: American Wood Council

Similar to detail A with slotted holes to accommodate slight lateral movement of the beam under load. This detail is more commonly used when the beam is sloped as opposed to flat.

 

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Originally published in Engineering News-Record.

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