The AC 156 standard is the go-to method for testing nonstructural components for seismic performance. Nonstructural elements—such as equipment, ceilings, and mechanical systems—are critical for maintaining operational functionality during and after seismic events. The ability to accurately replicate seismic forces through shake table testing ensures that these components perform as intended under real-world earthquake conditions.
The AC 156 standard is widely adopted for evaluating the seismic performance of nonstructural components, such as HVAC systems, lighting fixtures, ceilings, and mechanical equipment. These elements, while not part of the structural frame, are essential for operational continuity during and after seismic events. Accurately replicating seismic forces through shake table testing ensures these components can perform as intended under real-world earthquake conditions.
This blog provides a detailed roadmap covering seismic data access, response spectrum generation, shake table setup, and post-test analysis. The goal is to help professionals meet AC 156 compliance effectively, whether for U.S. or international projects.
1. Importance of SD Values for Nonstructural Testing
SD values represent the short-period design acceleration, evaluated at 0.2 seconds spectral period, and are critical for defining the seismic forces applied to nonstructural components. Accurate SD values ensure the testing reflects site-specific seismic hazards, aligning with AC 156 requirements.
2. Tools for Accessing SD Values in the United States
- ASCE Hazard Tool: Generate seismic design parameters such as SD for specific U.S. locations by entering project coordinates.
- Seismic Design Maps: A USGS-powered tool offering detailed seismic hazard information for compliance with building codes.
These tools streamline seismic design, ensuring compliance with AC 156 standards for U.S.-based projects.
3. Finding SD Values for International Projects
Each region has unique seismic hazard models, making it challenging to obtain accurate SD values internationally. Below are useful resources for global projects:
- Global Seismic Hazard Map: Provides hazard data for various countries worldwide.
Additionally, QuakeLogic offers custom seismic hazard data for regions such as:
- Turkey
- North Africa
- Central Asia
- Europe
For tailored seismic data, contact us directly. We can provide SD values, scaled ground motions, and site-specific data.
4. Ground Motion Selection and Filtering for AC 156 Testing
Ground motion selection is a critical step to ensure the seismic conditions simulated on the shake table accurately reflect site-specific hazards.
- NGA West 2 Database: Access a wide range of unscaled ground motion records. Use filtering tools to select appropriate records based on parameters such as magnitude and fault type.
According to AC 156, both horizontal and vertical seismic forces must be tested separately or simultaneously. The selected motions should meet the Required Response Spectrum (RRS) derived from the building’s location.
5. Ground Motion Scaling and Spectral Matching
Scaling and matching ground motion to the Test Response Spectrum (TRS) is essential for AC 156 compliance. Key techniques include:
- Time-Domain Matching: Adjusts time history to align with the target spectrum.
- Frequency-Domain Matching: Alters frequency content to match the RRS.
The process ensures the test simulates real seismic forces and meets performance standards required by ASCE 7-22.
6. Generating a 5% Damped Response Spectrum Using Python
A 5% damped response spectrum is the standard reference for seismic design and testing. We offer a free Python code that generates this spectrum, along with an example for easy implementation. This tool will aid in compliance with AC 156 by ensuring the selected ground motions meet the required spectrum. Please reach us at support@quakelogic.net
7. Shake Table Setup and Instrumentation Overview
AC 156 requires rigorous shake table testing to certify nonstructural components. Below are key elements for setup:
Shake Tables:
- Electromechanical Tables: For small components.
- Servo-Hydraulic Tables: For larger equipment.
- Portable Bi-Axial Tables: For field applications or lab testing.
Sensors and Instrumentation:
- Accelerometers measure acceleration during shaking.
- Displacement Sensors track movement.
- Strain Gauges monitor internal stress.
The Test Response Spectrum (TRS) measures the actual response of components under seismic forces. TRS must envelop the RRS to ensure the test simulates seismic events accurately.
8. Post-Test Analysis and Certification
After testing, post-test inspections verify the operational and physical integrity of components. The component must maintain:
- Structural Integrity: Limited yielding allowed, but no significant damage.
- Operational Integrity: Critical components (Ip = 1.5) must function post-test.
- Anchorage Compliance: All mounting systems must remain intact during testing.
Detailed reports documenting setup, results, and performance are essential for certification. Compliance with ASCE 7-22 and FEMA 461 ensures regulatory approval and safety in high-risk seismic zones.
9. Industry Applications of AC 156
AC 156 is essential for sectors where nonstructural components must remain operational during seismic events, including:
- Healthcare: Hospitals require seismic compliance for life-sustaining equipment.
- Telecommunications: Ensures data centers remain operational post-earthquake.
- Energy and Utilities: Critical systems must withstand seismic forces for safety.
- Nuclear Power: Adheres to IEEE Standard 344 for seismic qualification.
Shake table testing provides confidence that nonstructural components will perform reliably under seismic conditions, minimizing downtime and enhancing safety.
10. Selecting the Right Shake Table for Your Project
At QuakeLogic, we offer a variety of shake tables designed to meet AC 156 standards:
- Small-scale tables: Ideal for compact nonstructural components.
- Large-scale tables: Capable of simulating higher forces for industrial applications.
Please share your shake table specifications, and we will prepare a custom offer. Reach us at sales@quakelogic.net
Conclusion
Shake table testing under AC 156 is critical for certifying the seismic performance of nonstructural components. By selecting appropriate ground motions, scaling them accurately, and using advanced instrumentation, you can ensure compliance and operational integrity.
With tools like the ASCE Hazard Tool, Global Seismic Hazard Map, and NGA West 2 Database, we help you meet AC 156 requirements effectively for both domestic and international projects.
As always, “Seeing is Believing”—reach out to us for shake table demonstrations or solutions tailored to your needs.
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