Hanger System Research Articles

Reduction of seismic loads in cable tray hangers

A study has been conducted to partially assess the feasibility of using flexible rather than rigid support systems for carrying electrical and control cables in nuclear power plants. Using analytical and experimental studies, it was found that a flexible hanger design with appropriate stiffness and damping characteristics could be used to isolate trays from hanger vibration and significantly reduce hanger loads during seismic events if the connectors could be adequately tuned to account for system variables. Finite element techniques were used to select a flexible connector for a specified base hanger system. Tests were conducted on one-third-scale models to establish values for some of the parameters and to partially verify the analytical methods. For the hanger systems considered, introduction of the flexible connector allowed support-hanger loads and hanger displacements to be reduced greatly while satisfying tray displacement constraints. It appears that a flexible-connector system can provide better dynamic response than the conventional type system using rigid connectors. This conclusion is valid for all variations in system parameters studied. Although the flexible-connector concept looks very promising based on this study, substantial work, including full-scale testing, must be completed before this concept can be validated for actual plant designs.

Probabilistic Evaluation of Construction Deficiencies

A probabilistic procedure is formulated to evaluate construction deficiencies involving hundreds of identical structural elements in which uniformity of quality is desirable. These include welds in truss systems, pipe hanger systems, and shear studs in reinforced concrete structures to develop composite strength. A deterministic solution to this type of problem may be inadequate, as may a simple binomial distribution. The use of the hyperbinomial distribution is most appropriate since the success rate parameter is a random variable. The distribution also shows how added information could help make a better decision. The procedure is discussed using shear studs in reinforce concrete structures as an example. Some repair procedures are also suggested. This method may be a safe and economical way to deal with some construction deficiency problems.