CASE STUDY on FEA Analysis

Addressing Structural Resonance: Impact Testing and FEA-Based Structural Optimization

The Real Issue

In a glass bottle manufacturing plant, raw materials are conveyed through silos installed on a steel support platform. These silos are fitted with vibration exciters to ensure smooth material flow during operation.

Over time, two supporting “I” beams began to experience elevated vibration levels. The intensity of these vibrations increased to a point where the platform became unsafe for personnel access and maintenance work.

Initial assessments pointed toward structural resonance as the primary issue. This phenomenon occurs when a structure’s natural frequency aligns with an external excitation frequency, leading to amplified and potentially hazardous vibrations.

Key Observation:

• The vibration exciters were operating at 24.4 Hz
• Impact testing identified the second natural frequency of the beam at 25.450 Hz
• The close proximity of these values confirmed Mode 2 torsional resonance

Fig. 1 — Impact test showing Mode 2 at 25.450 Hz

Our Approach

Technomax Middle East LLC implemented a structured two-step engineering analysis:

1. Impact Testing

An instrumented hammer test was conducted directly on the installed beam to determine its natural frequencies and mode shapes under real operating boundary conditions.

2. Finite Element Analysis (FEA)

A detailed and validated 3D FEA model of the beam assembly was created to:

• Verify the presence of resonance
• Align simulation results with experimental findings
• Assess possible design modifications prior to physical execution

The FEA findings confirmed the issue:

• Mode 2 frequency (FEA): 24.406 Hz
• This value closely matched the excitation frequency, validating the resonance condition

Before Modification: Mode 2 = 24.406 Hz (Resonance)
After Modification: Mode 2 = 36.411 Hz (Safe range)

Before

After

Fig. 2 — Mode 2 torsional shape from FEA (before and after modification)

The Solution

To resolve the resonance issue, a structural enhancement was introduced:

A 5 mm thick stiffener plate was installed between the top and bottom flanges of the “I” beam and welded along both sides of the web.

This change transformed the open I-section into a closed, box-type structure, significantly improving torsional stiffness.

The proposed modification was evaluated using FEA modal analysis before implementation to ensure effectiveness.

FEA Modal Results (Before vs After):

Results

The second mode frequency increased from 24.406 Hz to 36.411 Hz, representing a shift of approximately +12 Hz. This moved the natural frequency well away from the 24.4 Hz excitation frequency, effectively eliminating the resonance condition.

• Before Modification: Mode 2 = 24.406 Hz (Resonance condition)
• After Modification: Mode 2 = 36.411 Hz (Safe operating condition)

This frequency shift ensured that the structure no longer operates within the resonance range.

Fig. 3 — Isometric view of the modified beam with stiffener plates

Conclusion

By integrating impact testing, validated FEA modeling, and a focused structural redesign, Technomax Middle East LLC successfully resolved a critical resonance issue that was impacting both safety and operational performance.

Key Outcomes:

• Elimination of excessive vibration levels
• Enhanced structural integrity
• Safe access for personnel restored
• Avoidance of expensive structural replacement

Facing Similar Challenges?

If you are dealing with vibration, structural, or reliability concerns, expert analysis supported by simulation and real-world diagnostics can provide effective solutions.

Technomax Middle East LLC combines advanced FEA capabilities with condition monitoring services  expertise to diagnose issues, validate corrective actions, and prevent costly failures.

• Leading FEA consultancy in the UAE
• Proven expertise in structural and vibration analysis
• Comprehensive engineering support

Connect with our certified specialists to discuss your requirements.