Rivets and Riveted Joint Design: The Bridge That Refused to Fall

The Bridge That Refused to Fall

It was 1997 when structural engineer the practitioner the practitioner first noticed the hairline cracks spreading across the steel beams of the Carrington River Bridge.

The bridge had been built in 1952—entirely riveted. No high-strength bolts. No welding. Just rows upon rows of hot-driven steel rivets holding 4,200 tons of structural steel together across a 380-meter span.

The cracks were in the beams. Not in the riveted joints.

After a six-month forensic analysis, the practitioner's team concluded something that stunned the regional transport authority: the riveted connections were the strongest surviving elements of the entire structure. Forty-five years of thermal cycling, dynamic traffic loads, and corrosive river spray—and the rivets had held.

The beams had fatigued. The concrete deck had spalled. The paint system had failed. But the rivets? Still clamping. Still carrying load. Still doing exactly what they were designed to do nearly half a century earlier.

the practitioner's report included a single line that became legendary in her firm: "The rivets outlasted everything around them. If only we'd designed the rest of the bridge as carefully as we'd designed the joints."

That observation holds a lesson for every engineer, fabricator, and designer who works with permanent fastening: understanding rivets—their dimensions, their failure modes, their joint designs, and their standards—isn't optional knowledge. It's foundational.

This guide gives you everything you need. Every standard. Every formula. Every table. Every failure mode. The complete technical reference, organized for both the shop floor and the design office.

What You'll Master in This Guide

• Classes and types of riveted joints (lap, butt, single, double, triple)
• Failure modes — how rivets and plates actually break under load
• Design assumptions and allowable stresses from AISC and ASME codes
• Complete joint strength analysis with worked examples
• Rivet lengths for forming round and countersunk heads (AISC tables)
• ANSI Large Rivet dimensions — Button, High Button, Cone, Pan, Countersunk, and Swell Neck
• ANSI Small Solid Rivet dimensions — Flat, Flat Countersunk, Button, Pan, Truss, Coopers, Tinners, and Belt rivets
• British Standard rivet dimensions — BS 275, BS 641, and BS 4620
• Metric rivet dimensions — Hot forged and cold forged per BS 4620
• Tentative length ranges for metric rivets
• Hold-on (Dolly Bar) and Rivet Set impressions per ANSI standards
• Complete resistance formulas for every standard joint configuration

Classes and Types of Riveted Joints

Riveted joints fall into three application categories:

• Pressure vessel joints (boilers, tanks — governed by the ASME Boiler Code)
• Structural joints (bridges, buildings, trusses)
• Machine-member joints (frames, brackets, mechanical assemblies)

Note: Pressure vessel riveting follows strict ASME Boiler Code specifications and is not covered in this guide. The focus here is on structural and machine-member riveted joints—the types you'll encounter in fabrication shops, maintenance operations, and mechanical design.

The Two Fundamental Joint Types

Every riveted connection is a variation of one of two basic configurations:

1. Lap Joint The plates overlap each other and are held together by one or more rows of rivets passing through both plates.

2. Butt Joint The plates being joined sit in the same plane. A cover plate (also called a butt strap) bridges the gap and is riveted to both plates by one or more rows of rivets.

Riveting Terminology

Design Principle: For structural and machine-member joints, the proper pitch is determined by making the tensile strength of the plate over the length of the repeating section equal to the total shear strength of the rivets in the repeating section.

General Considerations of a Riveted Joint

Six critical factors must be addressed in the design or specification of any riveted joint:

• Type of joint (lap or butt, single or multiple riveted)
• Spacing of rivets (pitch, back pitch, diagonal pitch, margin)
• Type and size of rivet (head style, diameter, material)
• Type and size of hole (punched, punched and reamed, or drilled)
• Rivet material (steel, wrought iron, aluminum alloy, copper, Monel, Inconel)
• Allowable stresses (set by applicable codes and specifications)

Size and Type of Rivets

The rivet diameter $d$ commonly falls between:

$$d = 1.2\sqrt{t} \quad \text{to} \quad d = 1.4\sqrt{t}$$

Where $t$ is the thickness of the plate being joined.

Practical Note: Countersunk heads are not as strong as other head types. If maximum joint strength is required, use button head, cone head, or pan head rivets wherever clearance permits.

Size and Type of Hole

Rivet holes are usually made 1/16 inch larger in diameter than the nominal rivet diameter. In automatic machine riveting (cold driven), holes are reamed to provide minimum clearance so the rivet fills the hole completely.

Critical Detail: When holes are punched in heavy steel plate, considerable strength loss can occur unless holes are reamed to remove the damaged metal. Annealing after punching tends to restore plate strength near the holes.

Rivet Material

How Riveted Joints Fail

This is the section that separates engineers who understand rivets from those who merely install them. Every riveted joint can fail in exactly seven ways. Understanding these failure modes is the foundation of all joint design.

Rivet Failures

• Single shear — The rivet shears through one cross-section
• Double shear — The rivet shears through two cross-sections (in butt joints with cover plates)
• Crushing — The rivet is crushed by bearing stress against the plate

Plate Failures

• Edge shear (parallel) — Plate shears along two parallel lines from opposite sides of the rivet hole to the edge
• Edge tear (single line) — Plate tears from the middle of the rivet hole to the plate edge
• Crushing — Plate material is crushed by bearing pressure from the rivet
• Tensile failure — Plate tears between adjacent rivets in the same row or between adjacent rows

Preventing Edge Failures

Types 4 and 5 failures (edge shear and edge tear) are caused by rivets being placed too close to the plate edge. The prevention rule is simple and absolute:

Minimum Edge Distance: Place the center of the rivet at a minimum of 1.5 × rivet diameter away from the edge of the plate.

Preventing Diagonal Tearing

Failure due to tearing on a diagonal between rivets in adjacent rows (when pitch is four times the rivet diameter or less) is avoided by:

Minimum Transverse Pitch: Make the transverse pitch at least 1.75 × rivet diameter.

┌─────────────────────────────────────────────────┐
│          TYPES OF RIVET AND PLATE FAILURE        │
├─────────────────────────────────────────────────┤
│                                                  │
│  ═══╤═══╤═══╤═══    SINGLE SHEAR               │
│     │ ↕ │              Rivet shears on           │
│  ═══╧═══╧═══╧═══    one plane                   │
│                                                  │
│  ═══╤═══╤═══╤═══                                │
│  ═══│ ↕ │═══│═══    DOUBLE SHEAR                │
│  ═══╧═══╧═══╧═══    Rivet shears on two planes  │
│                                                  │
│  ───○───○───○───    TENSILE FAILURE              │
│     ↔   ↔   ↔       Plate tears between rivets  │
│  ───○───○───○───                                │
│                                                  │
│  ──→○←──            CRUSHING                     │
│     ██               Bearing stress exceeds      │
│  ──→○←──            material capacity            │
│                                                  │
│  ╔═══════╗                                       │
│  ║   ○───╫─→        EDGE TEAR                   │
│  ║       ║          Rivet too close to edge      │
│  ╚═══════╝          Min. margin = 1.5d           │
│                                                  │
└─────────────────────────────────────────────────┘

Theoretical vs. Actual Joint Failure

Here's where textbook engineering meets reality—and the gap matters.

What the Textbooks Assume

In simplified design analysis, these six assumptions are standard:

1. The load is carried equally by all rivets
2. No combined stresses act on a rivet to cause failure
3. Shearing stress is uniform across the rivet cross-section
4. The load that causes failure in single shear would need to be doubled for double shear
5. Bearing stress is distributed equally over the projected area of the rivet
6. Tensile stress is uniform in the section of metal between the rivets

What Actually Happens

Reality is considerably more complex:

• Rivets in lap joints do not undergo pure shear. They experience a combination of tensile and shearing stresses, failing due to combined stress—not a single stress.
• Shearing stress is NOT evenly distributed across the cross-section, despite the common assumption.
• Hot-driven rivets contract on cooling. This contraction:
  • In length: Draws the plates together, creating a clamping stress in the rivet estimated to be equal to the yield point of the rivet steel
  • In diameter: Creates slight clearance between the rivet and the hole
• The clamping force creates significant friction between the plates. A sizeable frictional force must be overcome before the plates slip and subject the rivets to shearing.

Engineering Insight: European practice traditionally designs joints for resistance to slipping (friction-based design). American and English practice uses strength-basis design. Research has shown that the resulting joint designs from both approaches are not very different from each other.

Allowable Stresses for Riveted Joints

Design stresses are set by codes, practices, or specifications. The two most referenced sources are:

AISC Specifications (Structural Steel for Buildings)

ASME Boiler Code

Practice Note: In machine design work, values close to the ASME design stresses or somewhat lower are commonly used.

Joint Efficiency

The efficiency of a riveted joint tells you how much strength you've lost by putting holes in the plate:

$$\eta = \frac{\text{Strength of the Joint}}{\text{Strength of the Unriveted Plate}} \times 100\%$$

This is the single most important metric for evaluating any riveted connection. A joint with 75% efficiency means you've retained 75% of the plate's original tensile strength.

Resistance Formulas for Standard Joint Configurations

These are the formulas you need to analyze or design any standard riveted joint. In all formulas:

Single-Riveted Lap Joint

    ┌──────────────────────────┐
    │  ○     ○     ○     ○     │  ← Plate 1
    └──┬─────┬─────┬─────┬────┘
       │     │     │     │
    ┌──┴─────┴─────┴─────┴────┐
    │  ○     ○     ○     ○     │  ← Plate 2
    └──────────────────────────┘
         Single Row of Rivets

Double-Riveted Lap Joint

    ┌──────────────────────────┐
    │  ○  ○  ○  ○  ○  ○  ○  ○ │  ← Plate 1
    │   ○  ○  ○  ○  ○  ○  ○   │
    └──┬──┬──┬──┬──┬──┬──┬──┬─┘
       │  │  │  │  │  │  │  │
    ┌──┴──┴──┴──┴──┴──┴──┴──┴─┐
    │  ○  ○  ○  ○  ○  ○  ○  ○ │  ← Plate 2
    │   ○  ○  ○  ○  ○  ○  ○   │
    └──────────────────────────┘
           Two Rows of Rivets

Single-Riveted Lap Joint with Inside Cover Plate

Double-Riveted Lap Joint with Inside Cover Plate

Double-Riveted Butt Joint

Triple-Riveted Butt Joint

Worked Example 1: Single-Riveted Lap Joint

Problem: Analyze a 12-inch section of a single-riveted lap joint made up with plates of 1/4-inch thickness and six rivets, 5/8-inch in diameter. Rivet holes are 1/16 inch larger than the rivets.

Design Stresses Assigned:

• Shear: 8,500 psi
• Bearing: 20,000 psi
• Tension: 10,000 psi

Step A — Safe Load Based on Single Shear of Rivets

$$L = n \times A_r \times S_s = 6 \times \frac{\pi}{4}(0.625)^2 \times 8{,}500$$

$$\boxed{L = 15{,}647 \text{ pounds}}$$

Step B — Safe Load Based on Bearing Stress

$$L = n \times A_b \times S_c = 6 \times (0.625 \times 0.25) \times 20{,}000$$

$$\boxed{L = 18{,}750 \text{ pounds}}$$

Step C — Safe Load Based on Tensile Stress

$$L = A_p \times S_t = 0.25[12 - 6(0.625 + 0.0625)] \times 10{,}000$$

$$\boxed{L = 19{,}688 \text{ pounds}}$$

Result

The safe tensile load is the least of the three computed loads:

$$L_{\text{safe}} = 15{,}647 \text{ pounds (governed by rivet shear)}$$

Joint Efficiency:

$$\eta = \frac{15{,}647}{12 \times 0.25 \times 10{,}000} \times 100 = \boxed{52.2\%}$$

Interpretation: This joint retains only 52.2% of the unriveted plate strength. The controlling failure mode is rivet shear — meaning the rivets are undersized relative to the plate, or more rivets are needed.

Worked Example 2: Double-Riveted Butt Joint

Problem: A 12-inch section of double-riveted butt joint with main plates 1/2-inch thick and two cover plates each 5/16-inch thick. Three rivets in the inner row, two in the outer row. Rivet diameter: 7/8 inch. Hole diameter: 1/16 inch larger than rivets.

Same design stresses: 8,500 / 20,000 / 10,000 psi.

Step A — Safe Load Based on Double Shear

$$L = n \times 2 \times A_r \times S_s = 5 \times 2 \times \frac{\pi}{4}(0.875)^2 \times 8{,}500$$

$$\boxed{L = 51{,}112 \text{ pounds}}$$

Note: Cover plates combined thickness (5/8 inch) exceeds the main plate thickness (1/2 inch), so double shear governs.

Step B — Safe Load Based on Bearing Stress

$$L = n \times A_b \times S_c = 5 \times (0.875 \times 0.5) \times 20{,}000$$

$$\boxed{L = 43{,}750 \text{ pounds}}$$

Step C — Safe Load Based on Tensile Stress (Outer Row)

$$L = A_p \times S_t = 0.5[12 - 2(0.875 + 0.0625)] \times 10{,}000$$

$$\boxed{L = 50{,}625 \text{ pounds}}$$

Step D — Combined Analysis (Inner + Outer Row)

If the joint fails, it must fail at both sections simultaneously:

Bearing strength of two rivets (outer row): $$L_1 = 2 \times (0.875 \times 0.5) \times 20{,}000 = 17{,}500 \text{ pounds}$$

Tensile strength of plate at three-hole section (inner row): $$L_2 = 0.5[12 - 3(0.875 + 0.0625)] \times 10{,}000 = 45{,}938 \text{ pounds}$$

Total combined safe load: $$L_{\text{combined}} = 17{,}500 + 45{,}938 = 63{,}438 \text{ pounds}$$

This exceeds any of the individual failure loads.

Result

$$L_{\text{safe}} = 43{,}750 \text{ pounds (governed by bearing)}$$

Joint Efficiency:

$$\eta = \frac{43{,}750}{0.5 \times 12 \times 10{,}000} \times 100 = \boxed{72.9\%}$$

Interpretation: This butt joint retains 72.9% efficiency — a significant improvement over the single-riveted lap joint. The controlling mode is bearing failure, suggesting that harder rivet or plate material, or larger rivet diameters, would improve the joint.

Rivet Lengths for Forming Heads

The following table gives rivet lengths required for forming round heads and countersunk heads as specified by the American Institute of Steel Construction. These are critical for shop planning — ordering the wrong length rivet means wasted material and rework.

Important: Values may vary from the standard practice of individual fabricators and should be checked against the fabricator's own standards.

Rivet Lengths to Form Round Heads (inches)

Rivet Lengths to Form Countersunk Heads (inches)

ANSI Large Rivets — ANSI B18.1.2-1972 (R1995)

These are the workhorses of structural riveting — 1/2-inch diameter and up. All dimensions in inches.

Head Proportion Formulas

These formulas give the basic (manufactured) dimensions for each head type, where $D$ is the nominal body diameter:

Length Measurement: Length $L$ is measured parallel to the rivet axis from the extreme end to the bearing surface plane (flat heads) or to the intersection of the head top surface with the head diameter (countersunk heads).

Body Diameter Tolerances

Length Tolerances

Note: All standard large rivets have fillets under the head not exceeding a 0.062-inch radius.

Button Head and High Button Head Dimensions (inches)

Note 1: "Mfd." = Basic dimensions of head as manufactured. Note 2: "Driven" = Dimensions of manufactured head after driving and also of driven head.

Cone Head and Pan Head Dimensions (inches)

Flat Countersunk and Oval Countersunk Head Dimensions (inches)

Formulas: $A = 1.810D$; $H = 1.192(\text{Max }A - D)/2$; included angle $Q = 78°$.

Swell Neck Dimensions (inches)

The swell neck is applicable to all standard large rivets except the flat countersunk and oval countersunk head types. Formula: $E = D + 0.063$; $K = 0.500D$.

ANSI Hold-On (Dolly Bar) and Rivet Set Impressions

Per ANSI B18.1.2-1972 (R1995). These dimensions determine minimum pitch and diagonal pitch by governing clearance requirements. All dimensions in inches.

Button Head and High Button Head Impressions