Overview
The Unisphere, an iconic NYC landmark unveiled at the 1964 New York World’s Fair, continues to stand as a symbol of global unity. At the request of the New York City Department of Parks and Recreation, LiRo-Hill led the first major structural evaluation and condition assessment of the 120 ft stainless steel globe. The scope included documenting existing structural defects and conducting a full code compliance review of the superstructure. LiRo-Hill integrated conventional engineering techniques with advanced technologies, combining rigorous field inspections, aerial drone imaging, and in-office structural analysis. This approach enabled us to develop sustainable repair recommendations, accompanied by an estimate of costs.
About the Project
- Prime Consultant: LiRo-Hill performed all structural engineering, inspections, cost estimating, LiDAR scanning, and boom operations in-house to ensure full project control and efficiency. We also managed the work of subcontractors including material testing, ground penetrating radar, aerial drone inspections and equipment rentals.
- Boom Lift Inspections: Primary inspections conducted using a fully articulating, 30-ton, 150’ boom lift, selected for its extended vertical and horizontal reach to navigate the Unisphere’s complex frame, cables, and landmasses.
- Aerial Drone Imaging & Data Management: Aerial drone flights performed across the Unisphere’s exterior and interior to capture high-elevation defects inaccessible by lift; real-time inspection data was organized and tracked through cloud-based field management software for streamlined coordination and reporting.
- LiDAR: High-resolution scanning was used to capture the structure and fountain, generating a detailed 3D model that accurately reflects the unique shape and layout of its components.
- 3D Analysis Model: An advanced structural analysis model was developed by leveraging the geometric data obtained from the LiDAR scan. Python scripting enabled rapid generation and iterative adjustments to the model, allowing the team to efficiently account for unknowns in the original design and incorporate deficiencies identified during field inspections. This streamlined approach also facilitated the simulation of various loading scenarios.
Project Challenges & Solutions
The Unisphere’s scale, age, and structural complexity posed several distinct challenges. With limited original drawings available, LiRo-Hill reverse-engineered the globe’s physical properties using LiDAR scanning, drone imaging, and detailed field investigations.
Due to the globe’s unconventional geometry, tapered welded box members, radial cables, and tilted axes, a custom analytical approach was required to assess its structural integrity. LiRo-Hill created a custom 3D model using advanced design software, allowing quick adjustments based on field measurements. Cloud-based tools streamlined data collection and coordination, ensuring a comprehensive evaluation with minimal site disruption.
Outcome
LiRo-Hill delivered a comprehensive structural assessment report that identified critical structural members and evaluated the Unisphere’s compliance with current building codes. The report also included structural repair recommendations, supported by wind speed probability analysis, safety factors, additional technical evaluations, and an approximate cost estimate. These findings helped NYC Parks secure additional funding for future restoration, ensuring the long-term preservation and resiliency of this iconic landmark.
