Introduction

The global transition to renewable energy demands infrastructure that is both durable and cost-effective. Wind turbines, solar arrays, and marine energy devices operate in harsh environments, facing dynamic wind loads, seismic events, thermal cycling, and potential ice accumulation. Structural engineers must verify that these systems remain safe for decades of service. RISA (Rapid Interactive Structural Analysis) provides a comprehensive software suite to meet these challenges. By enabling detailed modeling, multi‑load analysis, and automated code checking, RISA helps engineers design renewable energy structures that are robust, compliant, and optimized for material efficiency.

This article explores how RISA is applied to renewable energy projects, from tall wind turbine towers to ground‑mounted solar panel supports. We will cover the core features of RISA, a step‑by‑step analysis workflow, and the practical benefits that make it a trusted tool in the industry.

What Is RISA?

RISA is a suite of structural engineering programs developed by RISA Technologies. It began as a 2D frame analysis tool and has evolved into an integrated platform covering 3D modeling, finite element analysis, design optimization, and code‑based member design. The flagship product, RISA‑3D, allows engineers to create detailed 3D models, apply a variety of static and dynamic loads, and perform linear, nonlinear, P‑Delta, and buckling analyses. Specialized modules such as RISAFoundation (for concrete footing and mat design), RISAFloor (for concrete and steel floor systems), and RISAConnection (for steel connection design) extend its capabilities.

What sets RISA apart is its combination of intuitive graphical input and robust analytical engines. Engineers can quickly define geometry, assign boundary conditions, and run sophisticated analyses without writing code. The software also supports international design codes, making it applicable to projects worldwide. For renewable energy infrastructure—where structures are often tall, flexible, and subjected to repetitive loads—RISA’s ability to handle dynamic analysis and fatigue checks is especially valuable.

Applications in Renewable Energy

Wind Turbine Support Structures

Wind turbines are among the tallest and most dynamically sensitive structures in the built environment. A typical utility‑scale turbine tower may reach 100 m (330 ft) or more, supporting a heavy nacelle and rotating blades. The tower, foundation, and transition piece must resist extreme wind gusts, cyclic fatigue from rotor rotation, and seismic shaking. RISA is used to analyze the entire support system: the steel or concrete tower, the base ring, and the foundation.

Engineers model the tower as a tapered tube or lattice, dividing it into segments with varying wall thickness. They then apply wind loads per standards such as ASCE 7 (Minimum Design Loads for Buildings and Other Structures) or the specific IEC 61400‑1 for wind turbines. RISA’s dynamic analysis module can compute natural frequencies to ensure the tower does not resonate with the rotor’s 1P (once per revolution), 2P, or 3P harmonics. If resonance is found, engineers adjust stiffness or add damping. Foundation designs are checked using RISAFoundation to verify overturning resistance, bearing pressure, and sliding under combined loads.

Solar Panel Mounting Systems

Photovoltaic (PV) arrays are installed on rooftops, ground‑mounted racks, and even floating platforms. Each system must withstand wind uplift, snow loads, and seismic forces while keeping panels at the optimal tilt angle. RISA is used to analyze the aluminum or steel racking frames, the purlins that support the modules, and the ballast or anchor system.

A typical ground‑mount system consists of posts (piles or concrete footings), horizontal beams, and inclined rafters. Engineers model the frame in RISA‑3D, assigning member sizes and material properties. Wind loads are calculated using ASCE 7’s Chapter 30 (Components and Cladding) or a wind tunnel study. For large utility‑scale solar farms, the analysis may also include thermal expansion and contraction of long rows. RISA’s nonlinear analysis can account for the slackening of guy wires or the uplift of shallow foundations. The software then checks each member for strength, stability, and deflection, ensuring compliance with the applicable building code.

Marine Energy Devices

Wave and tidal energy converters operate in aggressive saltwater environments and are subject to wave slamming, currents, and biofouling. Although less common than wind and solar, these devices require robust structural analysis to survive deployment and maintenance cycles. RISA can be used to model the steel or concrete substructures, the mooring systems, and the supporting piles or gravity bases.

Engineers define the wave forces using directional spectra and apply them as time‑history loads or equivalent static pressures. Because marine energy structures often experience large deformations and nonlinear mooring line behavior, RISA’s nonlinear solver becomes essential. The software also helps evaluate fatigue at welded connections, where wave‑induced stresses can lead to crack propagation. By integrating RISA with CFD or hydrodynamic analysis results, engineers can iterate on the design to minimize stress concentrations and extend service life.

Detailed Structural Analysis Workflow with RISA

Creating the 3D Model

Every RISA project begins with the creation of a three‑dimensional structural model. Engineers can start from scratch using the graphical workspace or import geometry from CAD software (such as AutoCAD or Revit) via DXF or BIM links. The model is built by defining nodes, members (beams, columns, braces), and plates. For renewable energy structures, special attention is paid to member orientations, releases (e.g., hinges), and boundary conditions that represent foundation supports or connection details.

In wind turbine towers, the model often includes the tower as a series of tapered tube sections. The nacelle weight and rotor thrust are applied as point loads at the tower top. For solar racks, the model includes the major frame members, purlins, and diagonal bracing. Engineers also define the panel weight as a uniform load on the purlins. Material properties—steel grade, concrete strength, aluminum yield—are assigned from a built‑in library or customized by the user.

Defining Loads and Load Combinations

After the model is complete, load definitions are applied. RISA supports dead loads, live loads, wind loads, seismic loads (using response spectrum or equivalent lateral force), snow loads, and thermal loads. For renewable energy structures, the most critical loads are often:

  • Wind loads: Calculated per ASCE 7 or IEC 61400 for wind turbines. For solar arrays, wind uplift and lateral forces are calculated considering exposure category, topography, and array tilt.
  • Seismic loads: Determined by the site’s spectral response acceleration values. For tall wind towers, higher‑mode effects may be significant.
  • Ice loads: Relevant for cold‑climate wind turbines or solar panels. Ice accumulation adds mass and changes aerodynamic properties.
  • Fatigue loads: Repetitive cycles from wind gusts, rotor rotation, or wave action. RISA can perform a fatigue analysis using stress‑range histograms.

Load combinations are automatically generated based on the chosen design code (e.g., AISC 360 or ACI 318). Engineers can modify combination factors and add serviceability checks (deflection limits) with a few clicks.

Performing the Analysis

Once loads are applied, the engineer selects the analysis type. RISA offers several options:

  • Linear static analysis: Used for conventional structures where deformations are small and material remains elastic. Suitable for solar racking under normal wind.
  • Nonlinear analysis (including P‑Delta): Essential for tall, slender wind turbine towers where second‑order effects (P‑Δ and P‑δ) are significant. RISA’s nonlinear solver handles large displacements and material nonlinearities.
  • Dynamic analysis: Includes modal analysis to find natural frequencies and mode shapes. For wind turbines, this verifies that the tower’s natural frequency avoids the rotor’s exciting frequencies. Response spectrum analysis is used for seismic evaluation; time‑history analysis can be applied for extreme events.
  • Buckling analysis: Identifies the critical load factor and buckling mode shape. Important for thin‑walled tower sections and slender rack members under compression.
  • Fatigue analysis: RISA can compute stress ranges from multiple load cases and compare them against allowable endurance limits (e.g., from AISC or Eurocode).

The analysis results are displayed graphically—deflected shapes, moment diagrams, stress contours—and in tabular form. Engineers quickly identify overstressed members, excessive displacements, or instability issues.

Code Compliance and Design Optimization

After reviewing the analysis results, engineers use RISA’s design modules to check each member against applicable codes. For steel members, RISA checks interaction equations for combined axial and bending stresses per AISC 360 (US) or Eurocode 3 (European projects). Concrete foundations are sized and reinforced using RISAFoundation, verifying punching shear, flexure, and soil bearing.

An iterative optimization process begins: engineers adjust member sizes, change connections, or add stiffeners until all checks pass with acceptable utilization ratios. RISA’s “Auto Design” feature can automatically suggest the lightest section that satisfies strength and deflection criteria, saving substantial design time. The final design is then documented in a detailed report that includes load diagrams, design summaries, and code references—essential for permitting and construction.

Key Benefits of Using RISA for Renewable Projects

Enhanced Accuracy and Reliability

RISA employs validated finite element solvers and up‑to‑date code checks. For renewable energy structures, where failure can be catastrophic and costly, this accuracy is paramount. The software’s ability to handle nonlinear behavior, dynamic resonance, and fatigue ensures that real‑world conditions are captured. Engineers can trust that a RISA‑designed tower or rack will meet safety standards under extreme events.

Time and Cost Efficiency

Manual calculations for complex structures like wind turbine towers can take weeks. RISA automates most of the process: model creation, load application, analysis, and design iteration. A single engineer can model and analyze multiple design alternatives in a day. This speed reduces engineering labor costs and shortens project schedules. Moreover, by optimizing member sizes, RISA helps minimize material waste—steel tonnage for a solar farm can be reduced by 5–10% without sacrificing safety, directly impacting the project’s bottom line.

Integration with Other Tools and BIM

RISA supports the modern engineering workflow by allowing data exchange with Revit, Tekla, and other BIM platforms. A wind turbine tower model created in Revit can be exported to RISA for detailed analysis, and the results can be pushed back to update the BIM model. This integration ensures that structural design stays aligned with architectural and MEP systems. Additionally, RISA can import loads from specialized wind or wave simulation software, enabling a seamless multi‑discipline design process.

Real‑World Examples

Though specific project details are often proprietary, several published case studies illustrate RISA’s effectiveness. For instance, a large wind farm in the Midwest used RISA to design 80‑meter tubular steel towers for a Class III wind regime. The analysis revealed that standard wall thicknesses could be reduced in the upper sections, saving over 15 tons of steel per tower while still satisfying buckling and fatigue limits. In another example, a utility‑scale solar plant in California used RISA to design single‑axis tracker support frames. The software’s nonlinear capabilities were essential for accounting for the tracker’s movement and the resultant load redistribution during wind events.

Conclusion

Renewable energy infrastructure must be safe, durable, and cost‑effective. RISA provides engineers with the analytical power to meet these demands across wind, solar, and marine applications. From initial 3D modeling through dynamic analysis and code‑based design, RISA streamlines the workflow and delivers reliable results. By adopting RISA, engineering firms can reduce project risk, minimize material use, and accelerate the deployment of clean energy. As the renewable energy sector continues to grow, tools like RISA will become even more essential to building a sustainable and resilient power grid.