Bridge Project
This project focused on the design, analysis, and fabrication of a 3D-printed truss bridge, completed during a sophomore-level engineering design course. The bridge was required to conform to strict dimensional constraints while being constructed as a true truss rather than a solid frame. After assembly, each bridge was tested by applying a central downward load until failure, with performance evaluated by maximum supported load relative to the structure’s mass. The project combined hands-on fabrication with advanced computational analysis, emphasizing both structural mechanics and design optimization. The final bridge achieved a load capacity of 200 pounds while weighing only 126 grams, ranking as the strongest bridge in the class by strength-to-weight ratio.
Development
The development process involved four design iterations, including three prototypes and a final structure. Each iteration followed a cycle of CAD modeling, static analysis, 3D printing, physical testing, and redesign. Early prototypes provided critical data on failure modes, deformation patterns, and assembly challenges. Testing was performed on an Instron machine, which quantified both deflection and failure loads, enabling data-driven refinement of the design. Throughout this process, SolidWorks was used for virtual modeling and assembly, while hands-on fabrication provided insight into material behavior and print reliability. This iterative development approach emphasized design validation, rapid prototyping, and continuous improvement—skills that reflect real-world engineering workflows.
Calculations
Analytical work formed the foundation of the design process. Hand calculations were conducted using classical statics methods, such as the method of joints and method of sections, to estimate internal forces in each truss member. Excel and MATLAB were used to build automated solvers that expanded these calculations across multiple load cases. Virtual analyses were then performed in SolidWorks Simulation and ANSYS to visualize stress distributions and confirm load paths. Material strength calculations were applied to PLA truss members to predict failure conditions, ensuring that high-stress components were adequately reinforced. This combination of analytical, computational, and experimental techniques enabled reliable performance predictions and informed design optimization.
Redesign
Redesign was guided by direct observation of failure points in earlier prototypes. Broken members, excessive deformation, and joint weaknesses were systematically addressed in subsequent iterations. For example, premature failures near pin joints prompted changes in geometry and assembly methods, while excessive midspan deflection informed truss pattern adjustments. The video included here illustrates the controlled testing of a prototype, providing a clear example of failure analysis in practice. Each redesign iteration embodied the principles of root-cause analysis and continuous refinement.
Fabrication
Creating deadlines for final design, part ordering, and fabrication milestones. This kept the project on schedule, ensuring the vehicle would be ready for race weekend.
Key Design Attributes
Several innovations distinguished the final bridge design.
Recessed trusses: End trusses were recessed into the anchor blocks, distributing torsional forces more effectively and reducing joint failures. This feature ensured that even if pins fractured, the compression transfer into the block allowed the member to continue carrying load. Optimized member layout: The top chord was fabricated as a continuous member, allowing stress to be shared across its full length and minimizing stress concentrations. Material optimization: Bridge members incorporated weight-reduction cutouts while maintaining load-bearing capacity, a key factor in achieving a high strength-to-weight ratio. 3D printing strategies: Iterative experiments with infill density, wall thickness, orientation, and print temperature identified the strongest configurations for each type of member. These controlled variations in print parameters improved durability and reduced premature failures Together, these attributes resulted in a structurally efficient and reliable design that outperformed competing bridges under testing.
Final Product
The completed bridge was assembled from individually printed truss components and successfully tested under central loading. The structure held 200 pounds before failure while weighing only 126 grams, representing the highest strength-to-weight performance in the class. The final design validated the effectiveness of the recessed truss strategy, optimized geometry, and print parameter adjustments. A video of the bridge during testing is included on this page, illustrating both its capacity and failure mode under extreme loading.
Presentation
The project concluded with the development of a professional conference-style poster, summarizing the design process, analyses, and results. The poster distilled complex calculations and multiple design iterations into a concise, visually effective presentation. This exercise emphasized the importance of technical communication, requiring the selection of key results and insights most relevant to an external audience. The ability to balance technical depth with clarity and accessibility reflected professional standards of engineering reporting and reinforced the value of effective documentation in collaborative projects.
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Skills Learned
This project provided significant experience in applying theoretical structural mechanics to a practical design challenge. The use of hand calculations, Excel and MATLAB solvers, and finite element analysis software such as SolidWorks Simulation and ANSYS reinforced the importance of combining multiple methods to evaluate forces and predict structural performance. Beyond calculation, failure prediction and material analysis became central to the process, as strength-of-materials principles were applied to anticipate fracture modes and validate results against physical testing. The iterative design process, modeling, prototyping, testing, and redesign, developed a systematic approach to continuous improvement and emphasized the value of data-driven decision making. The fabrication of prototypes also highlighted the role of manufacturing optimization in engineering. Adjustments to 3D printing parameters, such as infill density, wall thickness, orientation, and temperature, provided valuable lessons in how material behavior can be tailored to improve strength, reduce weight, and enhance reliability. In parallel, the project reinforced professional skills such as project execution, task coordination, and time management, all of which were essential for meeting deadlines and achieving performance goals. Finally, the creation of a professional poster emphasized the importance of technical communication, requiring the ability to distill complex calculations and design iterations into a concise, clear, and accessible format for both technical and non-technical audiences. Collectively, these experiences underscored the integration of theory, analysis, prototyping, and communication that defines real-world engineering practice.