Project Summary
ASR provided full mechanical and structural engineering design and analysis support for Harmony of Rivers, a large kinetic sculpture commissioned for permanent public installation in Avondale, Texas. Designed by artist Ann Moeller of Ann Moeller Studios, the sculpture features a tall vertical support structure and a large ring assembly intended to rotate freely in the wind, making environmental loading, public safety, and long-term durability primary drivers of the engineering design.
ASR served as the primary engineering partner, working directly with the artist to translate creative intent into a structurally sound, buildable, and publicly safe installation. ASR developed the complete engineering design and analysis package and coordinated with a local Professional Engineer, who reviewed and sealed the drawings and calculations for permitting and construction.
The final sculpture was clad by the artist using sculpted foam to define the exterior form and sealed with a waterproofing system to protect the internal structure and ensure long-term durability in an outdoor environment.
Engineering Scope & Key Constraints
The engineering scope focused on ensuring structural integrity, public safety, and environmental durability for a kinetic sculpture intentionally designed to interact with the wind and remain accessible to the public. Key constraints included:
- A tall, slender structure with a large exposed rotating element
- Public accessibility requiring conservative safety margins
- Wind loading as the governing structural load case
- Structural performance under combined dead weight and extreme wind events
- Torsional demands induced by wind acting on the rotating ring and shaft
- Bearing and shaft sizing for reliable long-term operation
- Corrosion resistance and environmental exposure in a harsh outdoor setting
- Foundation and anchorage design to resist overturning moments
- Fabrication, installation, and cost constraints
To ensure safety, wind loading was conservatively evaluated assuming the sculpture would not rotate, resulting in bounding load cases consistent with ASCE 7 requirements.
ASR’s Approach
Structural and Wind Load Analysis
ASR established governing design loads using ASCE 7-16, identifying site-specific wind speeds and combining them with geometric characteristics provided by the artist. Conservative assumptions were applied to account for the concave and textured nature of the sculpted surfaces.
Detailed finite element models were developed using ANSYS Mechanical (2023 R1) to evaluate structural response under combined wind and self-weight loading. Early analysis identified ring flexibility and bending stresses as key design drivers, particularly near the lower portions of the ring where bending moments were highest.
FEA results informed the overall structural architecture and guided subsequent design optimization.
Design Optimization and Connection Engineering
To efficiently manage stresses while minimizing material usage, ASR optimized the ring’s thickness profile around its circumference, increasing stiffness only where structurally required. Wind-induced torsional loading further informed the sizing of the ring width, shaft diameter, and shaft length.
The artist’s initial concept included modular ring segments. ASR introduced lapped joints to enable modular assembly and evaluated fastener demands using a hybrid approach combining simplified FEA techniques and traditional hand calculations. Fasteners were represented using bonded contact assumptions, allowing accurate force extraction while maintaining computational efficiency.
This balanced modeling approach enabled rapid iteration and clear decision-making while supporting both structural performance and constructability.
Material Selection, Fabrication Strategy, and Environmental Durability
As the sculptural concept evolved, the design transitioned from a modular fastened configuration to a welded ring supported by non-structural expansion foam. This change simplified fabrication and reduced cost while preserving the artist’s intended form.
Material selection was driven by corrosion resistance, environmental exposure, and cost. Although stainless steel was initially considered, the design transitioned to aluminum to improve affordability. Existing FEA models were rapidly updated with new material properties to verify strength and stiffness requirements. Weld demands were verified using hand calculations informed by FEA-derived load paths.
The sculpted foam cladding allowed the artist to define the exterior geometry while keeping the internal structure lightweight and efficient. A waterproof sealing system was applied to protect the internal components from moisture and environmental exposure, supporting long-term durability.
Foundation and Installation Engineering
ASR designed the shaft, bearing system, and support structure to ensure reliable operation under maximum wind loading. Bearing sizing was validated using reaction forces and moments extracted from the structural model.
To improve construction quality and reduce on-site risk, ASR developed a prefabricated concrete column and bearing housing assembly. Weldable reinforcing steel transferred wind-induced moments from the concrete column into a steel base plate and foundation anchorage system, eliminating the need for on-site concrete placement beyond the footing.
The foundation was designed as a large-diameter spread footing, with overturning moment governing reinforcement requirements. Both top and bottom reinforcement were incorporated to resist uplift and bending under extreme wind events.
Collaboration and Verification
ASR led the engineering design and analysis effort and produced the complete drawing and calculation package for the project. A local Professional Engineer reviewed ASR’s work and provided signed and sealed deliverables for permitting and construction.
Throughout the project, ASR collaborated closely with Ann Moeller Studios, fabricators, and installation teams to ensure engineering intent was preserved while accommodating artistic refinement and constructability considerations.
Outcome
ASR delivered a safe, durable, and cost-effective engineering solution that preserved the artist’s creative vision while meeting the demands of a permanent, publicly accessible installation. The final design safely withstands extreme wind events, provides robust foundations and connections, and supports long-term outdoor exposure.
Harmony of Rivers demonstrates ASR’s ability to partner directly with artists and architects to deliver full-scope engineering services for kinetic sculptures and public art installations—from early concept development through analysis, detailing, permitting support, and construction readiness.