Reading Structural Steel Drawings — Integrated Practice

Objective. Students will read a multi-sheet structural steel fabrication drawing package and produce a complete weld plan listing every joint, its welding symbol interpretation, required process, and fit-up dimensions.

Reading Structural Steel Drawings — Integrated Practice

By the time a fabricated steel member reaches the shop floor, every weld it will ever carry has already been decided — by an engineer, recorded on a drawing, and translated into welding symbols governed by AWS A2.4. Your job as a welder is to read that record accurately and execute it without guessing. This lab puts that skill to work on a realistic four-sheet drawing package for a structural steel connection.

What a Multi-Sheet Drawing Package Contains

Structural steel fabrication drawing packages are organized so that each sheet serves a purpose. A typical package for a column base plate and beam-to-column moment connection includes:

General notes sheet — material specifications (ASTM grade), electrode requirements, preheat requirements, applicable code (usually AWS D1.1 for structural steel), and inspection class.
Plan and elevation sheets — overall geometry, member sizes, and location of connections.
Connection detail sheets — large-scale views of each joint, with all welding symbols, dimensions, and fit-up tolerances shown in full.
Section cuts — slices through the connection at labeled cut lines, revealing weld access holes, backing bars, and layering sequences that cannot be seen in the elevation.

Read all four sheets before touching a form. Notes on the general sheet apply to every weld on every subsequent sheet.

Orienting Yourself on a Structural Detail

Start with the title block: confirm the scale, revision number, and drawing number. Use your engineer's scale to verify that a dimension you read numerically matches the drawn distance — if it does not, the printed number always governs. Next, trace each cut-line symbol (a circle with letters and a reference arrow) from the elevation to its matching section view. Structural details almost always show the same joint from at least two directions; compare both views before logging a joint.

Decoding a Welding Symbol on a Structural Drawing

Every welding symbol follows the layout defined in AWS A2.4:

1. Reference line — the horizontal backbone of the symbol.

2. Arrow — points to the joint; the arrow side of the joint is the side shown below the reference line.

3. Weld type — groove, fillet, plug, slot, or combination; shown as a graphic on the appropriate side of the reference line.

4. Dimensions — for a fillet weld, the leg size appears to the left of the symbol; for a groove weld, the depth of preparation appears in parentheses and the effective throat follows, or a CJP (complete joint penetration) designation is used instead of explicit dimensions.

5. Supplementary symbols — backing bar (rectangle behind the groove symbol), melt-through, weld-all-around circle, field weld flag.

6. Tail — the forked end opposite the arrow; contains the welding process abbreviation (SMAW, FCAW, GMAW, SAW) and may reference a WPS number.

On D1.1 structural work you will frequently encounter CJP groove welds on moment connections and fillet welds on shear tabs. A CJP symbol carries no explicit throat dimension because the throat equals the full base metal thickness — the joint design table in D1.1 specifies the required groove geometry for the process and position.

Building Your Joint List

Work systematically: number each weld in pencil directly on your personal copy of the drawing (or on the overlay sheet provided), then transfer that number to your weld plan form. For each joint record:

Joint number and location (e.g., "W-1, east flange of W14 column, elevation detail 3/S3")
Joint type (butt, T-, corner, lap)
Base metal (ASTM designation, thickness)
Weld type and size (e.g., 5/16 in. fillet, both sides)
Process (from the tail or general notes)
Position (flat, horizontal, vertical, overhead — derived from the orientation shown in the detail)
Preheat requirement (temperature and authority — D1.1 Table or engineer's note)
Inspection requirement (visual, MT, UT, RT — stated in general notes or on the detail)

Leave nothing blank. If a piece of information is not explicitly stated, write "per general notes" or "per D1.1 code" — do not invent values.

The QC Inspector Role

When you present your weld plan to your partner, treat it as a pre-weld inspection meeting. Your partner should challenge every entry with questions such as: "Where on the drawing does it say that is a CJP?" or "How do you know this weld is FCAW?" You must respond by pointing to the specific drawing location — a symbol, a note number, a general note line — that supports your answer. This exercise mirrors the real pre-job WPS review that happens on structural steel projects every day.

Safety in the Blueprint Reading Environment

This lab takes place at drafting tables, not at a welding station, so arc and fume hazards are absent. However:

Eye protection — if a cutting tool (knife, compass point) is used to mark prints, handle it with the same care as any sharp tool; set it down point-away from neighbors.
Housekeeping — drawing packages and reference books create trip hazards when left on the floor; keep aisles clear.
Ergonomics — extended close work at a drawing table causes neck and eye strain; take short posture breaks every 30 minutes.
Material Safety — highlighters and markers are low-hazard but ventilate the space if you are using permanent markers on large prints for extended periods.

When you later carry this weld plan to the shop floor, it becomes a safety document: a missed preheat requirement or a misread joint type can produce an undersized weld that fails in service. Accuracy here is a life-safety matter.

Key terms10

Complete Joint Penetration (CJP)A groove weld in which weld metal extends through the full thickness of the joint; no numeric throat dimension appears on the symbol because the throat equals the base metal thickness.

Partial Joint Penetration (PJP)A groove weld designed to penetrate less than the full thickness; the effective throat dimension is specified explicitly on the welding symbol.

Reference lineThe horizontal line that forms the backbone of every welding symbol, to which all other symbol elements are attached.

Arrow side / other sideThe arrow side is the face of the joint to which the arrow points; weld information placed below the reference line applies to the arrow side, and information above applies to the other side.

TailThe forked element at the end of the welding symbol reference line opposite the arrow; used to specify the welding process, WPS number, or other supplementary information.

Weld-all-around symbolA small circle placed at the junction of the arrow and reference line indicating that the weld continues entirely around the joint perimeter.

Field weld flagA filled triangular flag at the junction of the arrow and reference line indicating the weld is to be made in the field rather than in the fabrication shop.

Section cutA drawing view created by imagining a plane sliced through the structure at a labeled cut line; reveals internal geometry such as backing bars, weld access holes, and stiffener placement.

Weld PlanA document listing every joint in a fabrication package with its joint type, base metal, weld symbol interpretation, required process, preheat, and inspection requirement — used to plan and verify welding before work begins.

Engineer's scaleA ruler graduated in ratios such as 1:10 or 3/8"=1'-0" used to measure distances directly from an architectural or structural drawing without manual conversion.

In class: Students are issued a four-sheet structural steel connection drawing package (column base plate, beam-to-column moment connection) and independently read all views, sections, and notes to prepare a joint list. · Students complete a written weld plan form for each joint identified: joint type, base metal, required weld symbol decoded, weld process indicated, preheat note if present, and any quality or inspection requirement noted on the drawing. · Students present their weld plan to a partner who acts as a QC inspector, asking clarifying questions; the presenting student defends each entry by pointing to the specific drawing location that supports it.
Materials: Four-sheet structural steel fabrication drawing package, weld plan forms, AWS D1.1 (reference for joint design tables), AWS A2.4, engineer's scale, highlighters
Check: Weld plan accounts for all joints on the drawing and decodes each welding symbol correctly; instructor scores at 80% accuracy minimum using a completed answer key.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.