To make an interactive I-beam dimensions diagram, draw the section and its dimension marks as inline SVG, provide four labeled HTML buttons, and use JavaScript to keep the selected button, highlighted mark, and explanation in sync. CSS handles responsive sizing and visible states. The example should teach the terms—not imply that its simplified geometry is a verified beam size or engineering design.
What the diagram should teach
A basic I-section diagram can explain four measurements. The letters below are labels, not numeric values for a particular steel section.
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- Overall depth (
d): the full vertical extent of the section. - Flange width (
bf): the horizontal width across a flange. - Web thickness (
tw): the thickness of the vertical web. - Flange thickness (
tf): the thickness of a flange.
For a teaching graphic, use a simple, clearly labeled schematic. If you depict a named section, obtain its dimensions from a verified reference table and identify the database and version. BeamChart says its steel reference data is based on AISC Shapes Database v16.0, but that description is not a replacement for consulting the underlying authoritative data. BeamChart
Choose SVG for the drawing and HTML for the controls
Inline SVG is a practical fit for a small interactive technical illustration: the profile, dimension lines, and labels remain separate elements in the document, so JavaScript or CSS can target a particular mark. A static raster image is just a fixed picture and does not offer the same direct element-level styling and interaction.
Define the drawing in SVG coordinates and give it a viewBox. The viewBox lets the graphic scale to fit a different viewport while retaining its internal coordinate system. Set the displayed SVG width to fit its container, preserve a useful aspect ratio, and check the annotations at narrow sizes; scaling the drawing down can make labels too small to read. See the W3C SVG 2 viewBox guidance and MDN’s SVG in HTML introduction.
Use ordinary labeled HTML buttons to select dimensions, with visible explanatory text beside or below the drawing. Buttons provide a familiar control surface separate from the diagram; users should not have to discover information by hovering over a line.
Keep selection, highlight, and explanation synchronized
Represent each dimension in one JavaScript data object containing its key, display label, explanation, and SVG highlight target. When a user selects a dimension, update the selected key, the active button state, the matching SVG mark, and the heading and explanation together. Keeping those changes in one selection handler prevents the control and diagram from showing different selections.
- Build the structure: add the inline SVG, a set of buttons labeled with the dimension names, and a text area for the selected dimension’s heading and explanation.
- Make the SVG targetable: draw the I-section and each dimension line or annotation as separately identifiable SVG elements.
- Style the layout and states: use CSS for responsive sizing, typography, colors, and the selected state. Make the active state perceptible through more than color, such as a stronger stroke plus a control-state change.
- Wire the interaction: connect each button to the dimension data and update the active control, highlighted mark, and explanatory text whenever selection changes.
- Check the finished behavior: test the page at narrow widths, verify that focus is visible, and confirm that keyboard users can select every dimension and perceive the current selection.
This is a small enough interaction to implement with HTML, CSS, and JavaScript without a graphics framework; that is a practical design choice, not a benchmark claim. The directly on-topic BeamChart article, published September 19, 2026, describes this interaction pattern but includes placeholders for complete code and a live demonstration, so it does not establish a tested, ready-to-run implementation. Read the BeamChart article.
Make the graphic accessible and usable
Give the SVG a concise accessible name, and add a longer description when the drawing needs one. The SVG <title> and <desc> elements can supply those descriptions; aria-labelledby can associate the graphic with visible text. The W3C says authors should provide an accessible name for SVG content essential to comprehension, especially interactive content. See W3C SVG 2 document structure guidance and MDN’s SVG accessibility guidance.
Keep keyboard focus visible and ensure the selected state is communicated through the controls and the diagram, not color alone. The tutorial’s outline does not establish a particular keyboard interaction pattern or tested assistive-technology support; verify both in the completed page. SVG pointer-events matters only if users are meant to interact directly with marks. MDN documents visiblePainted as the default and none as a way to let pointer interaction pass through an element. Do not make pointer hover the only path to an explanation. MDN: SVG pointer-events
Keep a teaching diagram separate from engineering data
A schematic that labels d, bf, tw, and tf explains where those measurements belong; it does not establish their values for a real beam. Do not use an illustrative profile as a source for fabrication, selection, or structural design. For an actual section, use verified dimensions from an authoritative reference and rely on appropriate engineering design information.
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