Structural Analysis: A Comprehensive Guide

Welcome to the fascinating world of structural analysis, a crucial engineering discipline shaping our built environment. This field is vital in predicting and interpreting how structures respond to varying forces to ensure stability, strength, and rigidity. From towering skyscrapers to intricate tunnels and daily-use vehicles, every structure relies on these analyses for safety and reliability. Dive in with us as we explore this indispensable field’s techniques, innovations, and real-world applications.

What is Structural Analysis?

At its core, structural analysis is a scientific method employed by engineers to predict the behavior of structures under different types of loads, such as compression, tension, and shear. It is a subset of applied mechanics that allows engineers to ensure a structure’s stability, strength, and rigidity.

The overarching goal of structural analysis is to determine safety margins. It helps engineers to identify the thresholds of stress a structure can withstand before it fails. The structural analysis allows designers or engineers to ensure that a structure, or a piece of equipment, is safe for use under the estimated loads the structure is expected to withstand. Structural analysis is performed before the design stage, providing the internal forces and stresses engineers will evaluate during design and code checking. The process will typically account for the materials used, applied loads, and geometry of the structure or object.

What are the Different Types of Structural Analysis?

The world of structural analysis is as diverse as it is intricate. Multiple techniques and methodologies are at engineers’ disposal, each designed to analyze different aspects of structures.

Structural Analysis with Hand Calculations

The hand calculation technique represents one of the most basic forms of structural analysis. It involves rudimentary calculations that estimate the load-bearing capacity of a structure. Although limited in scope, this method is handy for making preliminary assessments or understanding simple structures.

Simple hand calculations provide a speedy and straightforward option to evaluate the different effects of simple forces on simple structures. A possible scenario would be calculating the bending moment forces on a horizontal beam.

These simple calculations are a standard practice often seen in the civil engineering sector. It is suitable for engineers who prefer not to spend an extended period designing but would like to still determine the rough forces that a beam will be exposed to due to applied loads.

Structural Analysis with Finite Element Analysis (FEA)

Moving beyond traditional hand calculations, we encounter Finite Element Analysis (FEA) — a groundbreaking methodology that has significantly enriched the field of structural analysis.

Finite Element Analysis is an intricate numerical method that can help engineers to solve complex problems with various variable inputs like applied loads, boundary conditions, and support types. Finite Element Analysis may be more complicated than hand calculations, but it is much more accurate. Conceptually, FEA dissects a complex structure into a finite number of small, simple “elements”. Since the small elements are simple (e.g. cubes, tetrahedrals, pyramids, etc.), their behaviors can be easily predicted mathematically. Combining millions of these small elements allows the complete complex structure to be recreated, and their combined behavior gives a comprehensive picture of the entire structure’s performance.

Within FEA, there are two crucial subdivisions:

Linear Analysis

In FEA, the most common type of analysis is linear analysis. This method applies to structures that only undergo small deformations and function within their elastic limit.

In practice, this applies to structural problems where stresses remain in the linear elastic range of the used material. In a linear analysis, the model’s stiffness matrix is constant, and the solving process is relatively short compared to a nonlinear analysis of the same model. Therefore, linear analysis is often used for a first estimate before performing a fully nonlinear analysis.

Nonlinear Analysis

In contrast, nonlinear analysis caters to complex scenarios where large deformations occur, materials exhibit nonlinear behavior, or intricate boundary conditions are involved. This method captures a more accurate reflection of real-world structures.

Nonlinear effects can originate from geometrical nonlinearities (i.e. large deformations), material nonlinearities (i.e. elastoplastic material), and contact. These effects result in a stiffness matrix which is not constant during the load application. As a result, a different mathematical strategy is required for the nonlinear analysis and, therefore, a different solver.

Enhancing FEA: The Advent of Reduced-Basis Finite Element Analysis (RB-FEA)

As our quest for efficiency continues, engineers have innovated a derivative of FEA called Reduced-Basis Finite Element Analysis (RB-FEA). While FEA has its strengths, it also has its weaknesses. One of those limitations is the intense computational requirement needed to analyze large and complex systems.

This is where Reduced Basis-Finite Element Analysis comes in (RB-FEA), which uses a reduced order modelling (ROM) approach. This delivers a condensed mathematical representation of the system being analysed while also ensuring accurate results based on physics-based accuracy indicators.

The computational efficiency of RB-FEA is especially beneficial for complex structures or scenarios where multiple computations are necessary, opening new avenues for real-time or parametric studies. This cutting-edge methodology has become a critical tool for advanced engineering tasks, enhancing productivity without compromising accuracy.

How is Structural Analysis Applied in Practice?

Structural Health Monitoring Systems

Structural health monitoring (SHM) systems represent a prime structural analysis application. SHM uses damage detection and characterization techniques for critical structures like bridges, wind turbines, and tunnels. It is a non-destructive in-situ structural evaluation method that employs several types of sensors embedded or attached to the structure.

The structural health monitoring process includes installing sensors, data acquisition, data transfer, and diagnostics through monitoring the structure’s safety, strength, integrity, and performance. Proper correction measures are suggested if overloading or any other defects are observed.

One way that structural health monitoring systems can give engineers a complete picture of the structural health of their asset is through RB-FEA, which, when paired with live sensor data from an asset, can be used to create a complete digital twin model complete with the different loads and forces that are acting upon the structure. For example, Akselos has built an entire digital twin workflow for the Shell Bonga Floating Production Storage and Offloading (FPSO) vessel.

Structural Optimization

Another primary application of structural analysis is structural optimization. Here, the objective is to design efficient, cost-effective, and resilient structures.

One of the main types of structural optimization is size optimization, which focuses on determining the optimal dimensions of structural components to minimize weight, cost, or other design objectives while maintaining performance requirements.

Free-size optimization is the most specialized of these methods. It is often applied to optimise machined structures and parts stamped from tailor-welded blanks. It is most widely used in designing complex laminate composite components, helping engineers find the optimal thickness, ply shapes, and stacking sequence for laminate composites. Engineers can set manufacturing constraints – such as the number of fibre orientations, the maximum thickness of each orientation, and the total laminate thickness – and then quickly generate an ideal concept design.

Free-size optimization uses the concept of super-plies to define a continuous distribution of thickness for each fibre orientation that meets the part performance requirements. Then, engineers can fine-tune the designs using ply-bundle sizing optimization. Each bundle represents multiple plies of the same orientation and shape while considering detailed behavior constraints, including ply failure. Finally, a ply stacking sequence optimization arranges every laminate to satisfy all manufacturing constraints while delivering optimal performance.

Structural Optimization in Action: Reducing 30% of Material Cost and Weight with Lamprell

Lamprell and Akselos partnered to demonstrate that engineering simulation software can optimize offshore wind assets’ design, delivery, maintenance and life. As part of the project, Akselos modelled Lamprell’s offshore wind jacket foundations to identify specific hotspots for optimization.

The modelling results showed that the software could reduce the steel weight of offshore wind jacket foundations by up to 30%, bringing several benefits to Lamprell, including a CAPEX reduction, improved operation and maintenance by eliminating unnecessary intervention, and asset life extension.

Start your Structural Analysis Journey

In conclusion, structural analysis is much more than a theoretical concept. It’s an engineering cornerstone that ensures the safety, functionality, and durability of structures around us. Each method has unique applications and benefits, from the simplicity of hand calculations to the sophistication of reduced-basis finite element analysis. And with innovative applications like structural health monitoring systems and structural optimization, structural analysis continues to shape our built environment in remarkable ways.

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