Bolted connections are also commonly used, but they need to be designed with sufficient pre - tension to prevent loosening during seismic events. In areas with a high risk of seismic activity, the requirements for cable tray installations are often very strict. For over 60 years, the mechanical, electrical, and fire protection trades have relied on TOLCO seismic bracing solutions. Threshold rules, longitudinal vs transverse bracing, MSS SP-58/SP-127 and SMACNA guidance, and the hospital-specific I_p = 1. At a minimum, the cable tray designer should confirm: These inputs affect tray selection, brace layout, splice design, anchor demand, and. In this blog post, we will explore the key factors that need to be taken into account when designing cable trays for seismic resistance. These forces can cause ground shaking, which in turn can lead to the.