Structural Connections

Structural Connections: What PE Architectural Engineering Candidates Need to Know

Structural connections are the unsung heroes of engineering design. While much attention is given to beams, columns, slabs, and frames, none of these structural elements function as intended without the connections that tie them together. For those preparing for the Architectural Engineering (AE) PE Exam, a solid grasp of structural connections—how they work, how they’re analyzed, and how they’re detailed—is essential for success both on the test and in practice.

1. What Are Structural Connections?

Structural connections are the joints that hold individual structural members together, transferring forces such as shear, axial loads, and moments from one member to another. Whether they are bolted, welded, or mechanically fastened, connections are designed to ensure structural integrity under expected loading conditions.

In buildings, connections appear in steel frames, concrete frames, timber structures, and hybrid systems. Their design must meet strength, serviceability, constructability, and cost criteria. For the AE PE exam, candidates should be familiar with both the theory and practical application of connections in these various materials.

2. Types of Connections by Material

Steel Connections

• Shear Connections: Designed primarily to transfer shear force. Examples include single-plate (shear tab), double-angle, and seated connections. These are considered flexible or simple connections, as they allow for some rotation.
• Moment Connections: Designed to transfer bending moments in addition to shear. These are rigid connections and include welded flange plates, bolted end plates with stiffeners, and flange-welded beam-column joints.
• Axial Connections: Designed to transfer axial loads, such as in truss members. These are often gusset plate connections using bolts or welds.

The AISC Steel Manual is the key reference for steel connection design and is often cited in the exam.

Concrete Connections

• Monolithic Cast-in-Place: Joints created by continuous concrete pours, providing full continuity.
• Precast Connections: Require mechanical connectors, grouted sleeves, or post-tensioning. These must ensure force transfer and durability.
• Reinforced Joints: Proper anchorage of rebar across joints is essential. Load transfer is achieved through bar development, confinement, and sometimes dowels.

Wood Connections

• Mechanical Fasteners: Include nails, screws, and bolts. Their capacity depends on embedment strength and connection geometry.
• Metal Connectors: Like joist hangers, truss plates, and proprietary hardware, these offer greater capacity and speed of assembly.
• Glue-Laminated (Glulam) Connections: Often require concealed steel plates and bolts, accounting for load paths and aesthetics.

The NDS (National Design Specification for Wood Construction) is the governing standard referenced in the AE PE Exam for timber connections.

3. Connection Behavior

Understanding the mechanical behavior of connections is vital:

• Ductility: Ductile connections can deform under load without sudden failure—important for seismic design.
• Stiffness: Determines how much a connection resists rotation. Classifications include:
  • Rigid: Full moment transfer, minimal rotation.
  • Semi-Rigid: Partial moment transfer.
  • Flexible: No moment transfer, allows rotation (used in simple framing systems).
• Redundancy: Well-designed connections provide alternate load paths if one part fails.
• Constructability: Connections must be feasible in the field. Bolted connections are often preferred in steel due to ease of assembly; welds require skilled labor and inspection.

4. Design Considerations for the PE Exam

When designing or analyzing structural connections on the AE PE Exam, candidates should consider:

Load Paths

Determine how loads move through the structure and into the foundation. For example, in a moment-resisting frame, horizontal loads are resisted by beam-column connections that must handle significant moment and shear forces.

Connection Limit States

Check for both strength and serviceability:

• Strength Limit States: Yielding, fracture, bolt shear, bearing failure, weld rupture.
• Serviceability Limit States: Excessive rotation, slip, or deformation.

Code References

Familiarize yourself with these standards, which are often provided in exam references:

• AISC 360 (Steel)
• ACI 318 (Concrete)
• NDS for Wood
• ASCE 7 (Loading criteria)
• IBC (General code compliance)

5. Examples of Common Exam Topics

• Example 1: Bolted Shear Connection
  A W-beam is connected to a column using a single plate (shear tab) and ASTM A325 bolts. You may be asked to calculate the number of bolts needed based on the shear demand, bolt strength, and spacing requirements.
• Example 2: Moment Connection Detailing
  Given a beam-column intersection, you may need to determine if a bolted end-plate connection meets moment demand using flange bolt capacities and weld checks.
• Example 3: Concrete Beam-Column Joint
  You could be asked to evaluate a joint for adequate anchorage and rebar development, referencing ACI minimum bar extensions and transverse reinforcement requirements.
• Example 4: Wood Beam Connection
  You may be given a scenario involving bolts through a glulam beam and asked to calculate shear capacity based on bolt diameter, spacing, and load duration factors.

6. Tips for Exam Preparation

• Know Your References: Become fluent in navigating the AISC, ACI, and NDS documents. Tabs, bookmarks, and a well-practiced indexing system will save you time during the exam.
• Practice Connection Design Problems: Don’t just study flexural and axial member design. Work through problems involving bolt shear, weld design, rebar anchorage, and dowel connections.
• Understand Detailing Requirements: Know how to interpret and sketch standard connection details. Questions may test your ability to spot flaws in a provided connection detail.
• Be Efficient with Units and Conversions: Connections often require juggling kip, inch, and psi units—be vigilant.

Conclusion

Structural connections are foundational to safe, efficient, and code-compliant building design. On the AE PE Exam, they are likely to show up in both conceptual questions and quantitative design problems. Mastery of this topic not only boosts your exam score but also strengthens your professional engineering judgment.

As you prepare, prioritize understanding how different materials behave at their joints, how loads are transferred through connections, and how code provisions are applied in design scenarios. With focused study and practice, you’ll be ready to tackle structural connections with confidence on exam day.