Design of Nonstructural Systems and Components

Abstract

For the majority of buildings, the nonstructural components represent a high percentage of the total capital investment. Failure of these components in an earthquake can disrupt the function of a building as surely as structural damage, and can pose a significant safety risk to building occupants as well. Past earthquakes have dramatically illustrated the vulnerabilities of the nonstructural components. Apart from the falling hazard posed by the light fixtures, non-structural failures can create debris that can block egress from the building, and hamper rescue efforts. In this Chapter, we deal chiefly with those components and systems that are installed in the structure during construction or remodel, for which design details are provided on the construction documents. We will touch briefly on the contents and equipment items that the owner or occupants may place in the building. The failure of these items may pose a significant risk to the occupants of the structure. However, these items are diverse, and the designer should address their anchorage and bracing on a case-by-case basis. Nonstructural elements can generally be divided into architectural, mechanical, and electrical systems and components. Architectural components include items such as exterior curtain walls and cladding, non-load bearing partitions, ceiling systems, and ornaments such as marquees and signs. Mechanical components and systems include boilers, fans, air conditioning equipment, elevators and escalators, tanks and pumps, as well as distributed systems such as HVAC (Heating, Ventilation, and Air Conditioning) ductwork and piping systems. Electrical components include transformers, panels, switchgear, conduit, and cable tray systems. Components may be mounted at grade (on the ground floor or basement of a building) or installed on the upper levels or roof of the structure. Our focus is on “nonstructural components” as opposed to “nonbuilding structures”. Nonstructural components consist of equipment and systems that are supported vertically and laterally by a structural framework independent of the component itself — a piece of equipment supported by a building frame, for example. In addition, we will consider the anchorage and bracing of moderately sized components at or below grade, such as chillers, pumps, and fans.