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How Much Weight Can Aluminum Extrusion Framing Hold?

Did you know aluminum can pull its weight – literally – vs. steel? And did you know extruded parts are often stronger and lighter than formed-sheet parts?

Aluminum extrusion is a modular, lightweight way to create intricate profiles and seamless systems without having to involve a welder.

Yet, for heavy-duty and structural framing, some engineers remain skeptical – how much weight can aluminum extrusions actually hold?

Hopefully this guide will open eyes to what’s possible with structural aluminum – extruded profiles and brackets!

 

The Basics: How Much Weight Can Aluminum Extrusions Hold?

Let’s start with the indisputable basics of aluminum extrusions, regardless of product or supplier.

“How strong is extruded aluminum?” isn’t a question with a 100% firm answer. A better question is, “How much strength do I want from my extruded aluminum system?”

Aluminum extrusion framing components are capable of supporting high-load applications:

That might sound odd, since aluminum is a soft metal. Indeed, it adds strength by relying on alloying elements such as:

  • Silicon
  • Magnesium
  • Manganese

With the right profiles, an engineer can achieve strength-weight balance that outclasses other processes – even ones that use steel.

The top two numbers engineers use to compare aluminum types are tensile strength and yield strength. 

    • The tensile strength of standard alloys varies from 10,000-70,000 psi.
    • The yield strength often falls between 20,000-35,000 psi.

Material composition and heat treatment are what influence a profile’s initial strength.

Common Strength Values in Popular Aluminum Grades

Grade

Use

Tensile Strength

Yield Strength

1100

Profiles

13,100

4,930

3003

Profiles

16,000

5,950

6005-T5

Profiles

37,700

34,800

6061

Profiles

18,000

8,000

6061-T6

Brackets

45,000

40,000

6063-T6

Profiles

35,000

31,000

7004

Profiles

50,000+

40,000+

7075-T6

Brackets

83,000

73,000

(Some data from MatWeb)

There isn’t much difference in the quality of raw materials from manufacturer to manufacturer. Instead, focus on how you and the manufacturer use the material.

3 Factors That Impact Strength When Building With Aluminum Extrusion

In each unique structural application, aluminum extrusion’s weight capacity depends on:

  1. Engineering & design – the connection
  2. Aluminum grade
  3. Anodizing
  4. End use

Failure to understand #1 can make or literally break your assembly!

1. Engineering & Design

Surprised to see this before grade?

If so, think about the nature of aluminum structural shapes.

A workbench leg could hold 75,000 lbs. of compressive force. That’d mean 300,000 lbs. total across four legs.

You won’t accomplish anywhere near that strength if you use the materials poorly. Design decisions that impact strength include size, shape, wall thickness, and – above all else in structural framing – connection.

  • Size – Overall dimensions greatly affect the strength and stiffness of a profile. A tall, skinny structural member will have high strength and stiffness in one direction, but much less in the other direction.

  • Shape – Bending and twisting (but not axial) load stress can cause more harm to a unique shape than a traditional shape. The more asymmetrical or unbalanced a shape is, the less likely it is to keep its dimensions under stress. Carefully consider component shapes in any structural extrusion project – even simple square and circular cross-sections differ in bend resistance.

  • Wall thickness – High variation in thickness along the components can cause distortion. The golden rule is that a profile’s minimum wall thickness should be at least 50% that of the thickest area. Profiles with varying wall thicknesses may also distort during heat treatment as differently sized areas cool at different rates.

As for connection …

 

Engineering & Design in Structural Framing

In aluminum structural framing, connection has always been the weak point.

T-slot extruded profiles are a common component of modular framing systems. The “T”-shaped track allows pieces to lock together without welding or otherwise adding joints.

However, some T-slots are overdesigned (due to mistrust in aluminum’s structural integrity) and look stronger than they are in practice. Even with a strong initial product, T-slot-based framing systems loosen and become misaligned over time.

Fortunately, for structural aluminum designs, there are emerging alternatives to T-slots. These modernized solutions use self-aligning brackets to keep connections precise, lending impressive support to a weight-bearing structure.

The strength of traditional T-slot profiles bears little relevance, as they’re still limited by their poor connection system. With the more recent alternatives, it’s the opposite situation – profiles are the only limiting factor in an assembly’s strength thanks to a superb connection.

Ask your aluminum extrusion design partner about mechanically locking fasteners that optimize your assembly’s strength. These modular systems eliminate the constant shifting of T-slot joints and are able to tap the full potential of the profile’s strength.

 

2A. Profile Grade

Yes, choice of grade will impact your extruded aluminum’s strength – just not as much as engineering does. Note that the grade your profiles use might not be the one your brackets should use (and vice versa).

Aluminum alloys common in extrusion profiles themselves include:

6063-T6

  • Tensile Strength: 35,000 psi
  • Yield Strength: 31,000 psi

This common magnesium-silicon alloy excels with features normally difficult to extrude, like thin walls and intricate details. Easy to anodize (more on that below), 6063 withstands corrosion better than the average grade.

The 6063-T6 (heat-treated) version is one of the most popular grades for aluminum structural framing systems.

6005-T5

  • Tensile Strength: 37,700 psi
  • Yield Strength: 34,800 psi

This medium-strength alloy is a notch above 6063 in sturdiness and sometimes used interchangeably with 6061. It also offers great corrosion protection.

The T6 tempered variation is popular in designing platforms.

6061

  • Tensile Strength: 18,000 psi
  • Yield Strength:  8,000 psi

This is the ages-old standard for structural components.

The 6061 alloy combines high fatigue strength and fracture toughness into a single profile capable of replacing welded steel.

1100

  • Tensile Strength: 13,100 psi
  • Yield Strength: 4,930 psi

Because it contains fewer additives, this “alloy” (that’s still 99% aluminum) remains quite soft. While you can’t heat treat it, you can extrude 1100 aluminum into complex shapes that surpass bare-minimum strength levels despite their softness.

This grade is one of the best for staving off corrosion for aesthetic-minded jobs.

3003

  • Tensile Strength: 16,000 psi
  • Yield Strength: 5,950 psi

Arguably the most popular aluminum alloys across all applications, 3003 aluminum adds manganese to make it stronger than 1100. This medium-strength material adds decent corrosion resistance, though not as much as 1100.

7004

  • Tensile Strength: 50,000+ psi
  • Yield Strength: 40,000+ psi

If you’re willing to pay a little more than for 6061, this aluminum-zinc alloy may be for you. It’s press-heat-treatable, helping it handle stress better than 6061.

2B. Aluminum Bracket Grades

In extruded structural framing systems, not all the strength has to come from the profile. In fact, the strength of your structure is entirely dictated by bracket strength (the connection) for T-slot systems. Your bracket connection also impacts how much weight your aluminum extrusion profiles can hold.

Common grades for aluminum structural brackets include:

6061-T6

  • Tensile Strength: 45,000 psi
  • Yield Strength: 40,000 psi

This variant of 6061 undergoes tempering to increase yield strength. Called aircraft-grade aluminum, it’s actually stronger than some stainless steels.

7075-T6

  • Tensile Strength: Up to 83,000 psi
  • Yield Strength: Up to 73,000 psi

Only certain components exclusive to the AngleLock line – such as rivets, threaded inserts, and custom screws – use this grade in adjustable framing brackets. It’s reserved for the most demanding components in a modular framing system. 

Because 7075-T6 can’t produce intricate shapes, it’s a poor fit for the frame itself in some applications. But in special-case, high-stress structural assemblies, it deserves more attention.

Don’t forget: You can boast the world’s strongest profile in your framing assembly, but it won’t meet its power potential if the brackets are weak.

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