What this module covers
D1.5 is the bridge welding code that AASHTO and AWS publish together. Part C on D1.5 is open book: 50 scorable items in 120 minutes, with the 2020 edition on screen as a PDF and word search off. The code is the answer key. Your job is to know which section holds the answer and how bridge rules differ from the building rules in D1.1.
This module carries two content areas. Materials and Design has a 5% minimum. Fabrication has a 25% minimum, and most of this module is about it.
By the end you will be able to:
- name the D1.5 section for a topic by title, without search,
- say where D1.5 is stricter than D1.1 and why,
- check workmanship, preheat and repairs against the code,
- explain what a fracture control plan adds for a fracture-critical member.
We name sections by title only. Keep your own copy of D1.5:2020 open while you read.
Finding your way around D1.5
The section map
D1.5 is built on the same skeleton as older editions of D1.1, which is useful and also a trap: the order looks familiar, but the content is bridge content.
| Section (by title) | What you look for there | Ask yourself |
|---|---|---|
| General provisions | Scope, the parties and their duties, definitions of the Engineer and Contractor | "Who has to do this?" |
| Design of welded connections | Weld sizes and effective areas, joint details, fatigue rules for bridge members | "Is this detail allowed on a bridge?" |
| Workmanship | Base metal preparation, fit-up, weld profiles, corrections | "Was the part made right?" |
| Technique | Filler metal control, preheat and interpass, heat input, process rules | "Was it welded right?" |
| Qualification | WPS qualification, welder, operator and tack welder tests | "What test, what range?" |
| Inspection | Contractor quality control, verification, visual and NDT acceptance, NDT procedures | "Is it acceptable, and who checks?" |
| Stud welding | Shear connectors, start to finish | "Is it a stud?" |
| Fracture control plan | Added rules for fracture-critical members | "Is the member fracture critical?" |
| Annexes | Forms, guidance and supplementary methods | "Is there a form or method for this?" |
Navigating without search
With search off, the table of contents and bookmarks are your index, and AWS warns that some navigation may be disabled. Practice this loop in your own copy until it is automatic: question topic, section title, the part inside it, the paragraph. Before you read the options, name the section in your head.
Read a provision in three passes
- Scope. What does this part apply to? Bridge codes often split rules by member type, by tension or compression, and by whether the member is fracture critical.
- The rule. Find the paragraph that answers the question.
- The exceptions. Look for "unless the Engineer", "when specified in the contract documents" and table notes. On D1.5 the Engineer's say comes up again and again.
Trap. Answering from D1.1 memory. A question that looks like a D1.1 question often has a different answer in D1.5 because the bridge rule is stricter or because the Engineer must accept something first.
Design, base metal and filler metal
Design rules an inspector reads
The design section covers effective weld areas, permitted joint details and fatigue considerations for bridge members. You will not design anything, but you check that the drawings and the welds match what the code permits. Bridge members carry cyclic traffic loading, so fatigue sensitive details matter more than on most buildings. When a stem mentions a tension flange, a cover plate end or an attachment on a girder, think fatigue and look in the design section.
Base metals
Bridge steels are ordered to bridge material specifications, commonly AASHTO M 270, which corresponds to ASTM A709. The code groups the steels it covers and ties preheat, filler metal and toughness requirements to the grade. A steel outside the code's list is not simply forbidden, but it needs the Engineer's acceptance and qualification by test.
Filler metals
D1.5 controls filler metal more tightly than D1.1. Expect requirements on matching strength, on diffusible hydrogen, on toughness of the deposited weld metal, and on storage, drying and exposure of low-hydrogen consumables. Read the technique section for consumable control, and read the qualification section for how a filler change affects a WPS.
Worked navigation (invented example). A drawing calls for a bridge steel of grade "G50" (invented label) joined to grade "G70" (invented). The question asks which filler strength applies. Path: technique or materials provisions for the matching rules; find both grades; read the note on joining different strength levels; check whether the Engineer must accept the choice. Do not answer from the D1.1 matching table.
Workmanship, technique and repairs
Workmanship
Workmanship covers base metal preparation (cutting, edge quality, laminations found at edges), fit-up (root openings, alignment, gaps in fillet joints) and finished weld profiles. When a measured fit-up value is outside the tolerance, the question is usually what the Contractor must do next: correct the fit-up, build up the joint under rules, or ask the Engineer.
Worked example (invented values). A butt joint in a flange has a measured root opening 3 mm wider than the WPS shows, and the WPS tolerance (invented for this example) allows 2 mm. Steps:
- Compare the measurement with the WPS and the workmanship tolerance, not with your shop habit.
- It is outside, so welding stops on that joint.
- Find the workmanship provision on correcting excess root openings, and read whether the correction needs the Engineer's acceptance.
- Record the measurement and the corrective action.
Technique: preheat, interpass and heat input
D1.5 links preheat to hydrogen control: the steel, the thickness and the hydrogen level of the consumable decide the minimum. Interpass temperature has a minimum and, for some steels, a maximum. Heat input may be limited so the heat affected zone keeps its toughness.
Measure preheat at the distance the code states from the joint, before the arc starts, and keep it through the weld. A heater that warms only one side of a thick joint is a common failure.
Trap. "Preheat was right when we started." D1.5 cares about the temperature during welding, including after an interruption.
Repairs and corrections
Repairs follow a path: find the defect, remove it, confirm removal, reweld with a qualified WPS, and inspect again by the same method that found it. D1.5 adds the Engineer at points D1.1 often leaves to the Contractor, such as repairs of cracks in members, repairs in base metal, and repeated repairs at one location. Read the repair provisions in the workmanship section for which repairs need the Engineer's acceptance first.
Fracture-critical members
What fracture critical means
A fracture-critical member is a tension member, or a tension part of a member, whose failure would be expected to bring down the bridge or part of it. Contract documents identify these members. The welding inspector does not decide which members are fracture critical; they check that the drawings flag them and that the added rules are followed.
What a fracture control plan does
In our own words, a fracture control plan tightens every step that could start a brittle fracture:
| Area | What the plan tightens |
|---|---|
| Materials | Toughness requirements for base metal and weld metal |
| Consumables | Hydrogen control, storage and exposure limits |
| Technique | Preheat, interpass and heat input |
| Qualification | Added tests for WPSs used on these members |
| Repairs | Engineer's acceptance and closer control of repair welds |
| Inspection | More inspection and testing, with records kept |
How to answer these questions
First decide whether the member is fracture critical from the stem. If it is, go to the fracture control plan before the general sections, because its rules add to or replace the general ones. If it is not, the general sections govern.
Trap. Applying fracture control rules to every bridge weld, or ignoring them because the general section allows something.
Check yourself
The three questions below cover finding the right section without search, consumable control on bridge work, and what changes for a fracture-critical member.
Where to look in your own books
- AASHTO/AWS D1.5M/D1.5:2020, table of contents: the section titles above
- D1.5:2020, design of welded connections: details, effective areas, fatigue
- D1.5:2020, workmanship: preparation, fit-up, profiles, repairs
- D1.5:2020, technique: consumables, preheat, interpass, heat input
- D1.5:2020, the fracture control plan for fracture-critical members
- AWS D1.5 Endorsement Description (Rev. 11.05.2026): exam format and code reference policy