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How to Safely Select Nail Substitutions for Connectors

A few days ago, I was speaking to a customer about an application using nail substitutions for a joist hanger installation. Her questions come up often, so I thought I would dedicate a blog post to some of the resources available that cover the use of different nails in connectors.

Designers and builders often wish to use different fasteners than the catalog specifies. The application could require short nails that don’t penetrate through the back of a ledger or they want to use screws or sinker nails for easier installation. The Wood Connectors Catalog provides multiple options for alternate nailing for face mount hangers and straight straps on page 27.

The load adjustments for alternate fasteners cover substitutions from a common diameter of 16d to a 10d, or a 10d to an 8d. Multiple different replacement lengths are also covered, with reduction factors ranging from 0.64 to 1.0.

It is important to remember that double shear hangers require 3” minimum joist nails. Short nails installed at an angle in double shear hangers will not have adequate penetration into the header.

Fastener - Double Shear — Fastener – Double Shear

Pneumatic nail guns used for connector installation are commonly referred to as positive placement nail guns. These tools either have a nose piece that locates connector hole, or the nail itself protrudes from the tool so that the installer can line the nail up with the hole. Most positive placement tools do not accept nails longer than 2½”, so framers using these tools will want to use 1½” or 2½” nails. To accommodate installers using pneumatic nails, we have a technical bulletin T-PNUEMATIC. This bulletin provides adjustment factors for many of our most common embedded holdowns, post caps and bases, hangers and twist straps.

The question of nail size also comes up when attaching hangers to rim board, which can range from 1” to 1¾”. The adjustment factors in C-2013 don’t necessarily apply with rim board, since the material may be thinner the length of the nails used. We also have a technical bulletin for that application – T-RIMBDHGR.

Several of the reduction factors are the same as those in the catalog. Testing of hangers with 10dx1½ nails on 1” OSB or 1¼” LVL did not do as well, however. We observed that once the nails withdrew a little bit under load, they quickly lost capacity. For that reason, we recommend full length 10d or 16d nails on those materials.

Understanding that alternate fasteners are available for many connectors can help you pick the right fastener for you application. When you specify a connector, it is important to also specify the fasteners you require to achieve your design load.

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What's Most Important To You As A Structural Engineer?

I am attending the 2012 SEAOC-SEANM Convention in Santa Fe, New Mexico this week. I did not realize that Santa Fe is the oldest state capitol in the U.S., first inhabited by Spanish settlers in 1607, and then settled by Don Pedro de Peralta in 1609-1610. The Palace of the Governors, built in 1610, served as the main government building in Santa Fe for nearly 300 years. The current capitol building, known as the Roundhouse, is the only round state capitol building in the U.S. Our airport shuttle driver used to be a tour guide, so we learned a lot on the drive in.

St. Francis Cathedral, Santa Fe. By Bill Johnson, 2005. Licensed under Creative Commons, some rights reserved.

The first session I attended today was a discussion of recent earthquakes. James Mwangi Ph.D, PE, Associate Professor of Architectural Engineering at Cal Poly, discussed his project to develop sustainable reconstruction practices for masonry and concrete structures in Haiti following the 2010 earthquake. Then Joe Maffei, Ph.D, SE, talked about lessons learned about concrete wall design from the 2010 Chile earthquake.
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What’s Most Important To You As A Structural Engineer?

A Little Fun with Testing

My apologies for being late with my blog post this week. We are having our once a year big sales meeting, so I’ve been traveling to the Midwest to participate. Speaking of traveling, several times each year, we invite our newest employees to our home office in Pleasanton, California for a week-long Sales and Product Orientation class. Although originally envisioned as detailed product knowledge training for our sales people, the class has evolved over the years to include people from all areas of our business such as finance, accounting, IT, purchasing, quality, marketing, and (of course) engineering.

I do one presentaton for the class explaining the importance of a continuous load path in a building, and another covering the history of innovation that led to some of our products. It is a great opportunity for me to meet my new coworkers by spending some time with them before they embark on their careers in different parts of the country (or world!).

My favorite training session I do for the class is about product development and testing, which includes a tour of our test lab in Pleasanton. We go over a lot of testing basics – how we select lumber, get parts made, build setups and run the tests. For a demonstration, I used to run a simple joist hanger test and also a holdown test. Usually I’ll pick a heavy holdown to test, since those make an impressive bang when the steel breaks, and then everyone jumps and gets a good laugh out of it.