Seismic Bracing Design for Seismic Protection

An earthquake is a natural disaster. One cannot prevent it but can prepare for it. In many cases, the structure of the building is under protection by means of proper design.

But the non-structural components of the building are as important as the building’s structure itself. These are MEP (mechanical, electrical, plumbing) and HVAC (heating, ventilation, air-conditioning) systems.

This field is Acrefine’s greatest expertise. We have decades of experience in this field, and we are ready to help you with your design needs according to local building codes. For example NFPA 13 require seismic protection for fire sprinkler systems. ASCE 7 seismic design requirements cover mechanical and electrical components.

Seismic bracing design for these components is primarily concerned with two main aspects:

  1. First, limiting lateral and longitudinal movement of components to predefined limits.
  2. Second, transferring seismic forces safely to the main structure of the building.

Seismic cable bracing for nonstructural components such as MEP piping systems

The fundamental nature of the earthquakes causes large movements which effects buildings. Based on the characteristics of the seismic event, each structure has its own unique response. The roof of a skyscraper will have the largest movements reaching couple of meters in each direction.

Any component subject to movement require proper attachment to the structure. Seismic cables are an easy way of achieving this goal. They allow isolation of components subject to vibration. Rigid braces do not have such a feature.

The length of steel ridgid brace is also a concern. Because it is subject to compression which can cause buckling. Therefore ridgid braces have specific requirements of calculations. This means more time and money for design and installation.

Rod stiffeners used in conjunction with braces prevent buckling of long threaded rods.

Restraint system seismic load calculations

Earthquakes generate forces that result in high G levels. Non-structural components at the minimum should be able to withstand these loads without failure. These forces can act in any direction whether lateral or longitudinal. Therefore, choosing the correct restraint type and anchors involves worst case scenario.

Lateral means perpendicular to the run, and longitudinal means parallel to the run. That mean, seismic motion in two directions must be able to withstand forces. A four-way bracing consist both of them at the same point.

The force at the centre of gravity results in tension and shear loads at anchor points. These outputs determine the proper products, which safely transfer the forces to the building structure.

Expected Outcome from Seismic Protection

☺︎ Component restrained and kept in place ➡ YES

☺︎ Loads transferred to structural elements ➡ YES

☹︎ Integrity of the component ➡ NO *

☹︎ Functionality of the component ➡ NO *

* For the last two, please refer to Seismic Calculations for Equipment section.

Acrefine offers life safety against earthquake damage

Seismic protection of buildings is unique to each project which is influenced by the location, building size and type. Hence each project, regardless of its size, requires its own design. Acrefine here can help you with followings and much more:

  • Overturning Calculations for Floor Mounted Equipment
  • Bracing Calculations for Suspended Equipment and Services
  • Avoiding The Need for Bracing (based on code ✪)
  • Detailed Drawings for Equipment Installation
  • Layout and Typical Detailed Drawings for Bracing

The basis for these calculations are well-established international codes and standards:

✪ Avoiding The Need for Seismic Bracing Design

Trapeze installations with steel sections (rather than threaded rods) may not require additional sway bracing. But there is a need for seismic calculations to check if these steel sections can withstand the seismic loads.

In some cases, single runs with short threaded rod hangers can withstand the forces. Thus do not require any bracing. Acrefine can help you determine the need for sway bracing in your project. We can help you save your money and time by doing the right design.