Analytical Modeling of the Force-Displacement Behavior of Reinforced Autoclaved Aerated Concrete Lintels and Validation Using Experimental Methods

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By: Elizabeth Hungerford Faculty Advisor: Dr. Jennifer Tanner Supporting programs: EPSCoR & Honors

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

What is AAC?

• Lightweight, cellular

• Made of cement, sand, lime, water, and

expansive agents

• Steam cured

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

High-quality building material

• Fire resistance

• Low-density

• High thermal efficiency

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 Lintels horizontally span wall openings (such as doors

and windows)

 Carry load from the wall above and distribute it across

the opening

 Standard grouted U-block construction with

longitudinal steel Grout Core Reinforcing Steel AAC U-Block Lintel

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

Nathan Stroud

• Strength testing of AAC lintels

• Evaluated strength contribution

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Additional construction

• 1, 6ft beam • 1, 8ft beam 

Testing

• Four-point bending 

Predict behavior

• Displacement • Design

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

Construction of lintels

• Thin-set mortar • Grout mixing • AAC U-block preparation • Curing

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

Four point bending

• Force applied and displacement measured

Hydraulic Actuator Neoprene Pad

Spherical Seat

Loading Rods and Plate

CMU Support

Coupled Steel Rod and Plate AAC Lintel

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

Basic concrete beam behavior

• Initial cracking

• Loss of grout

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

Grout Prisms

• Replicate water absorption

• Tested for compressive

strength



Reinforcing Steel

• Strain gauges

• Tested for tensile

strength • Grade 50 and 60 AAC blocks Grout prism 0 10 20 30 40 50 60 70 80 90 100 0 0.02 0.04 0.06 0.08 Stress (ksi ) Strain (in/in)

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Force displacement data

0 500 1000 1500 2000 2500 3000 0 1 2 3 4 5 6 7 8 9 For ce, lb Displacement, in Beam 1 Beam 2

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

Reinforcing steel yields

0 500 1000 1500 2000 2500 3000 0 1 2 3 4 5 For ce, lb Displacement, in Linear elastic Yield plateau Strain hardening

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

Moment curvature analysis



Predict displacement

• Yield and Ultimate

• Grade 50 and 60 steel

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Assumptions

• Reinforcing steel yields

• Plastic hinge length

𝜟 =

𝑷𝑳𝟑

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0 500 1000 1500 2000 2500 3000 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 For ce, lb Displacement, in

Force-Displacement Behavior and Predictions

P 10-6 Gr. 50 Y Gr. 50 U Gr. 60 Y Gr. 60 U 𝜟 = 𝑷𝑳𝟑 𝟑𝑬𝑰𝒄𝒓 + (𝜱𝒖𝒍𝒕−𝜱𝒚)𝒍𝒑L

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0 500 1000 1500 2000 2500 3000 0 1 2 3 4 5 For ce, lb Displacement, in P 10-4 P 10-4 Gr. 50 Y Gr. 50 U Gr. 60 Y Gr. 60 U 𝜟 = 𝑷𝑳𝟑 𝟑𝑬𝑰𝒄𝒓 + (𝜱𝒖𝒍𝒕−𝜱𝒚)𝒍𝒑L

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0 500 1000 1500 2000 2500 3000 0 2 4 6 8 10 12 For ce, lb Displacement, in P 10-8 P 10-8 Gr. 50 Y Gr. 50 U Gr. 60 Y Gr. 60 U 𝜟 = 𝑷𝑳𝟑 𝟑𝑬𝑰𝒄𝒓 + (𝜱𝒖𝒍𝒕−𝜱𝒚)𝒍𝒑L

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

Plastic Hinge Length

• Varied between 10% and 20%



Reinforcing Steel

• Grade 60



Actual Capacity vs Predicted Capacity

• Greater actual capacity

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 NSF EPSCoR

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