Seismic Restraints in Building Services: Ensuring Safety and Compliance

Seismic restraints are an essential component of building services in areas prone to earthquakes. They are designed to limit the damage and potential harm caused by seismic activity by securing the building services in place. In Australia, AS 1170.4 provides guidelines on the design and installation of seismic restraints in building services. In this article, we will discuss the importance of seismic restraints in HVAC, the steps involved in their installation, and how they work.

Establish Importance Level

The first step in installing seismic restraints is to determine the importance level of the building services. AS 1170.4 provides a table of importance levels that range from Level 1, which includes non-essential services, to Level 4, which includes essential services such as fire protection, emergency lighting, and communication systems. The importance level will determine the level of seismic restraint required for each component.

Review Services Design

The next step is to review the services design to establish which services require seismic restraints. Some components may not need seismic restraints, such as electrical conduits that are supported by the building structure. On the other hand, HVAC equipment such as air handling units, fans, and ductwork require seismic restraints due to their weight and the potential damage they could cause if they were to become dislodged during an earthquake.

Review Appropriate Clearances

The appropriate clearances between services must also be reviewed to determine if they need to be braced. For example, if there is a gap between HVAC ductwork and a fire sprinkler pipe, the ductwork must be braced to prevent it from dislodging and damaging the fire sprinkler pipe. Clearances are important in determining the location of the bracing and the type of restraint required.

Determining Location of Bracing

The location of the bracing is determined by considering the layout of the building services and the appropriate clearances between them. Bracing can be installed on the building structure or on adjacent services. For example, if an air handling unit requires bracing, it can be attached to adjacent ductwork or structural steel. The location of the bracing must be considered in relation to the weight of the component, the direction of seismic activity, and the anticipated forces on the component.

Determining Design Forces

The next step is to determine the design forces for the component. The design forces are calculated using the simple method outlined in AS 1170.4. The simple method provides a conservative estimate of the design forces based on the weight of the component and the anticipated seismic activity. The design forces are used to determine the size and strength of the restraint required to secure the component in place.

AS 1170.4 8.3 Simple Method

The simple method outlined in AS 1170.4 8.3 provides a step-by-step approach to calculating the design forces for seismic restraints. The method takes into account the weight of the component, the importance level, the seismic hazard level, and the design coefficient. The design coefficient is a factor that varies depending on the type of component and the direction of seismic activity.'

Below is a nominal example for a 2,000 kg piece of mechanical plant, on a Rock or Shallow Soil base.

In conclusion, seismic restraints are an essential component of building services in areas prone to earthquakes. They ensure the safety of building occupants and limit the potential damage caused by seismic activity. Following the steps outlined in AS 1170.4 is crucial to ensuring that building services are safe and compliant. By establishing the importance level, reviewing the services design, reviewing the appropriate clearances, determining the location of the bracing, and determining the design forces, building owners and operators can ensure that their building services are properly secured and compliant with seismic restraint guidelines.