Outdoor free-standing signs are frequently taken for granted. The owners of these lofty structures often forget about them as soon as they are erected, except to change the messages they contain. Just like the rest of your property, however, outdoor sign structures need to be inspected and maintained on a regular basis.
A common cause of structural failure is fatigue stress due to wind. Even if high wind conditions are not present, your sign may suffer from fatigue stress damage. The theory works similarly to when you bend a piece of wire with pliers; if you keep bending it back and forth, eventually it snaps. It might take a while, but in time, your sign can come crashing down, and it may not take a high-stress situation to send it over the edge.
You can prevent fatigue stress damage by making sure your engineer designs the structure for a decreased allowable stress level. If the building code requires design for a certain level of stress, for example, you can design for a lower stress level than the code indicates. Many engineers, because high-wind loads are so sporadic in some areas, do not usually do this due to the increased cost.
Improper design is another cause of signage structure failure. In one example, a landmark sign in front of a major hotel and casino in Las Vegas was inadequately designed, and the original structure collapsed during construction. Especially in such high-wind locations as the Las Vegas metropolitan area, you need to make sure you hire a qualified engineer to design your sign structure.
Now if you are paying good money for a qualified designer, there is no reason to scrimp on the contractor. While most contractors adhere to the designs provided by the engineer, some do not.
With signage, you primarily utilize specialty contractors; once in a while, you run across one that believes they have built enough sign structures that they don't need to follow a set of plans. While contractors are held liable for the quality of the construction for years and are required to carry insurance covering each project, a sign failure is still a hassle you do not need.
Sign installers and inspectors should be aware of the conditions that create problems and lead to failure. Bolts should have appropriate shank lengths so that connecting plates are solidly connected and a rocking motion does not occur. You must also have plug welds on internal splice rings to prevent the constant back and forth motion, and eliminate impact that leads to abrupt material failure.
In addition, welds need to be properly sized. In many instances, the welder puts too much weld in place, thinking that he is improving the connection. In fact, he may be creating a crystallizing heat ring, which actually sabotages the joint.
In addition, all welds need to be properly primed and painted. You should always re-do the primer before you paint your welds, or you will most likely end up with a rust problem.
You need to have a qualified professional make scheduled inspections of your sign structure every few years to check for weakened connections and overstressed members.
The inspector should have the construction documents readily available. With that information, the inspector can determine if the structure has more square footage of sign than the design allowed, and can readily see what the original design was supposed to be.
Lack of maintenance is another reason signage structures do not hold up. As a general rule, owners should have a routine painting schedule using rust-proof paint, paying particular attention to bolts, base plates, and welds. Corrosion due to water, salt and such environmental factors as acid rain can wreak havoc on your signs. Proper maintenance and inspection can help identify these problems before it is too late.
Rusted or broken bolts can be replaced during an inspection, but it is not a good idea to put new welds over broken or corroded welds. A connection retrofit is best in that case, otherwise the cracked metal will lead to cracked welds and the repair will have a brief life span.
If you take care of your signs, they should keep standing for a long time. While it is easy to forget to give them the attention they need, keep in mind that between external forces and improper maintenance, your sign structure may not be as sound as you think.