Structural Steel Erection

Steel Structure Erection

Introduction to Steel Structure Erection

Steel structure erection is one of the core activities of the ironworker (generalist) trade. This task involves assembling, on the job site, the prefabricated structural steel elements — beams, columns, joists, bracing, and decking — to form the load-bearing structure of a building or civil engineering project. The Red Seal exam requires a complete mastery of the procedures, calculations, and standards that govern this activity.

This chapter covers the fundamental principles, lifting methods, bolted and welded connections, tolerances, load calculations, and Canadian regulatory requirements. You must be able to apply this knowledge in practical situations and answer typical exam questions.

Applicable Standards and Codes

CSA S16 — Design of Steel Structures

CSA S16 (Canadian Standards Association) is the primary reference for the design and calculation of steel structures in Canada. It defines the requirements for materials, connections, tolerances, and assembly methods. Although the ironworker does not design the structure, you must understand the principles of this standard to interpret plans and specifications.

Key points of CSA S16 that you need to know:

CSA W59 — Welded Steel Construction

CSA W59 (Welding — Steel Structure Welding Rules) specifies the requirements for welding steel structures. It covers processes, welder qualifications, joint types, electrodes, and quality control. The ironworker must know welding symbols and inspection requirements.

CSA S16.1 — Tolerances

CSA S16.1 defines the allowable tolerances for the fabrication and erection of steel structures. These tolerances are essential for ensuring the alignment and stability of the structure. The main tolerances to remember:

Site Preparation

Reading Plans and Shop Drawings

Before any work begins, the ironworker must read and interpret the erection plans and shop drawings. These documents indicate:

Erection plans use standardized symbols. You must know the meaning of the following symbols:

Verifying Foundations and Anchor Bolts

Before starting erection, the ironworker must verify:

Receiving and Storing Materials

Steel elements are delivered to the site by truck. The ironworker must:

Lifting and Rigging Equipment

Cranes — Types and Capacities

The choice of crane depends on reach, height, weight of elements, and site conditions. The main types of cranes used:

Calculating Lifting Capacity

The ironworker must verify that the crane can safely lift each element. The basic calculation is:

Crane capacity ≥ (Weight of element + Weight of rigging) × Safety factor

The safety factor is generally 1.25 for lifting operations. The weight of rigging (slings, hooks, shackles) must be included in the calculation.

Example : A beam weighs 4,500 kg. The slings weigh 150 kg. The minimum required capacity is:

(4,500 + 150) × 1.25 = 5,812 kg = 5.8 tons

The crane must have a capacity of at least 5.8 tons at the required reach and height.

Slings and Lifting Accessories

Slings are essential elements for lifting. Common types:

The sling angle is a critical factor. The tighter the angle, the greater the tension in each sling. The formula for calculating tension in each sling:

T = (P / n) × (1 / sin θ)

Where:

Example : A 2,000 kg load is lifted by 2 slings at a 60° angle.

T = (2,000 / 2) × (1 / sin 60°) = 1,000 × 1.155 = 1,155 kg per sling

At 30°, the tension would be: (2,000 / 2) × (1 / sin 30°) = 1,000 × 2 = 2,000 kg — double. The minimum recommended angle is 60°.

Erection Procedures

Erecting Columns

Columns are the first elements to erect. The typical procedure:

Columns are generally bolted to base plates using anchor bolts. Tightening must be done using the turn-of-nut method or to the specified torque.

Erecting Beams

Beams are lifted after columns. The procedure:

Important rule : never release the load until the beam is secured with at least two bolts per connection.

Bracing

Bracing provides lateral stability to the structure. It is installed as soon as possible after erecting columns and beams. Types of bracing:

Bracing is generally bolted to gusset plates welded onto columns and beams.

Decking

Decking (or metal floor deck) is installed after the main structure. It serves as a working surface and horizontal diaphragm. Decking is attached to beams using self-drilling screws or pins. Requirements:

Bolted Connections

Types of Bolts

Bolts used in steel structures are standardized according to ASTM A325 or ASTM A490. A325 bolts are carbon steel, while A490 bolts are high-strength alloy steel.

Bolt Tightening

Bolt tightening is critical to connection performance. Three tightening methods are recognized:

The tightening torque is calculated using the formula:

T = K × D × P

Where:

Example : A 19 mm (0.019 m) A325 bolt must be tensioned to 125 kN (125,000 N).

T = 0.2 × 0.019 × 125,000 = 475 N·m

Washers and Nuts

Washers are used to distribute the load and protect the surface. Requirements:

Inspection of Bolted Connections

Inspection of bolted connections includes:

Welded Connections

Welding Processes

Welding processes used for steel structures:

Types of Welds

The most common types of welds:

The size of a fillet weld is measured by the length of its leg. Strength is calculated based on the throat of the weld (distance between the root and the face).

Welding Symbols

The ironworker must be able to read welding symbols according to AWS A2.4. Elements of the symbol:

Welder Qualification

Welders must be qualified according to CSA W47.1 (Certification of Welding Companies). Qualification includes:

Tolerances and Quality Control

Erection Tolerances

Erection tolerances are defined in CSA S16.1. The main tolerances:

Quality Control

Quality control includes:

Site Safety

Fundamental Safety Rules

Safety is paramount in steel structure erection. Fundamental rules:

Construction Site Regulations

The Canada Occupational Health and Safety Regulations apply to construction sites. Key points:

Lifting and Rigging

Safe lifting rules:

Practical Calculations for the Ironworker

Load Calculations

The ironworker must be able to calculate loads on elements. Typical loads:

The total load on a beam is:

Q_total = Q_dead + Q_live

Deflection Calculation

The deflection of a beam is calculated using the formula:

Δ = (5 × w × L⁴) / (384 × E × I)

Where:

Example : A 6 m (6,000 mm) beam supports a load of 10 kN/m (10 N/mm). The moment of inertia is 50 × 10⁶ mm⁴.

Δ = (5 × 10 × 6,000⁴) / (384 × 200,000 × 50 × 10⁶)

Δ = (5 × 10 × 1.296 × 10¹⁵) / (3.84 × 10¹³)

Δ = 6.48 × 10¹⁶ / 3.84 × 10¹³

Δ = 1,687 mm

This deflection is excessive. The allowable deflection is L/360 = 6,000/360 = 16.7 mm. A stiffer beam is required.

Stability Calculation

Column stability is verified by calculating the slenderness ratio:

λ = KL / r

Where:

The maximum allowable slenderness ratio is 200 for main columns.

Common Pitfalls to Avoid

Here are the most common mistakes made by Red Seal exam candidates:

Summary

Steel structure erection is a complex activity that requires in-depth knowledge of standards, procedures, and calculations. Key points to remember:

The ironworker must be able to apply these principles in real situations and answer exam questions accurately. Practicing calculations and knowing the standards are essential for success.

Review Questions

These questions represent the type of problems you will encounter on the exam. Practice solving these calculations quickly and accurately.