Rivet Failure Leading to Fall and Personal Injury
Posted by John Sedgewick - 05/06/10 at 05:06 pmRivets are metal fasteners used to hold things, often other metal parts, together. Generally, rivets have a head and a shaft. The shaft is passed through pre-drilled holes in the parts to be connected until the underside of the head stops against one of the parts to be connected. The shaft is then “upset” or flattened against the farthest surface of the other part to be connected. The upsetting or flattening of the shaft has the effect of creating a second head and shortening the shaft. As the shaft is shortened, the second head moves toward the original head, squeezing the parts together. The idea behind the rivet as a fastener is that the rivet material is stronger than the forces tending to pull the connected items apart, so everything stays tightly connected.
Common uses of the rivet have included connecting the steel girders of skyscrapers, the steel plates of ship hulls, and the aluminum skin of airplanes.
Rivets may fail because they are made from material that is weaker than specified, because the shafts are not fully upset and shortened, because the overall joint design is flawed, or for a combination of these reasons.
As noted above, the theory of riveting is that the ability of the rivet material to withstand stretching forces is greater than the forces trying to tear the connected joint apart. An example of poor joint design would be a circumstance where an engineer miscalculates the stretch resistance of the rivet material. If that is overestimated, the stretching forces produced by the connected parts while they are in use may be greater than the rivet can bear, leading to joint failure. Poor quality material might cause the same problem.
Failure to properly shorten the shaft of the rivet during installation causes a slightly different problem. If the rivet is not shortened enough, the joint between the connected parts will not be tight. If the joint is not tight, it is likely that the forces on the rivet will not be limited to a either a “straight pull” or stretching force or a perpendicular or shearing force as anticipated by the design engineer. In a loose joint, the forces on the rivet probably include a diagonal or bending force as the connected parts move in response to the various forces they encounter. In a skyscraper, the forces could come from wind or earthquake. In a ship, the forces could come from wind, waves, or cargo loads. Once the forces on a joint deviate from a “straight pull” or a shear, the stretch resistance or shear strength of the rivet material are no longer the critical strength issues. With bending forces on the joint, the engineering analysis of the strength of the rivet material must be entirely different. It is not possible to use a rivet to reliably overcome bending forces because there are too many unknown factors that can lead to joint failure.
Riveted joints are designed to hold together on the assumption that the components that they connect will remain close and firmly held to each other.
Rivet failure has been known to cause personal injury in many circumstances, and can be the basis for a successful product liability case. One example from a real case involves a handle which broke off of a delivery truck door. The driver was assuming that the handle would remain firmly attached as he pulled down on the door to get it closed. When it suddenly came off in his hand, he lost his balance and fell from the back of the truck onto pavement and suffered broken bones and nerve injury.
Whenever there is a rivet failure leading to personal injury, it is helpful, and maybe necessary to proving the case, to recover the broken parts. Analysis of those parts can reveal whether the failure resulted from defective rivet material, bending, stretching or other factors. Understanding the cause of the failure is critical to proving a product defect. Was it the raw material of the rivet, the design of the joint, the construction of the riveted joint, or perhaps a failure of maintenance that lead to the injury?
If the broken parts are not available, prompt inspection of the remaining parts may help prove the case. For example, in the case of the handle that broke free from the delivery truck door, the door was a sandwich of materials (an inner and outer aluminum skin covering an strong but weather-pervious core material) which was held together by similar rivets. Inspection of the door revealed a pattern of rivet failure, leading to discovery of similar problems in other doors, and helping to prove that the basic door design was defective and its construction technique was negligent. The rivets were not strong enough for the purpose for either holding the basic door together or keeping the handle in place, and they were poorly installed. There was a history of other similar incidents, and the seller of the door failed to warn customers that a string of similar doors had failed.
If you or someone you know is injured by the failure of a rivet or other fastener, whether it be a screw, a bolt, or a nail, contact a lawyer with experience in similar cases. Getting the right lawyer and engineering expert involved early in the case may be critical to a successful outcome.
