Panel Weight, Center of Gravity, and Material Quantities — Tilt-Up Panels¶

Panel weight and center of gravity are among the most important computed values in a tilt-up workflow. They affect crane selection, lifting insert design, rigging geometry, temporary bracing, slab casting logistics, and panel book accuracy. This document captures the standard formulas and documentation conventions for those values.

1. Why These Values Matter¶

Three computed quantities appear repeatedly in tilt-up workflows:

Net concrete volume
Panel weight
Center of gravity (CG)

Without them, a panel cannot be reliably:

Lifted
Rigged
Braced
Scheduled for casting sequence
Compared against crane capacity and insert capacity

2. Concrete Unit Weight¶

For normal-weight reinforced concrete, the standard planning value is:

$$ \gamma_c = 150 \text{ pcf} $$

Where:

$\gamma_c$ = concrete unit weight in pounds per cubic foot

This is the conventional default used in panel books unless the project specifically uses lightweight concrete or a mix design with a different validated unit weight.

2.1 When to Deviate¶

Use a different value only when the engineer or batch data establishes it. Examples:

Lightweight structural concrete
Sandwich / insulated panel configurations with multiple wythes
Architecturally specialized mixes with confirmed density differences

For standard ConstructiVision output, 150 pcf should remain the default.

3. Gross and Net Volume¶

3.1 Gross Volume¶

For a rectangular single-thickness panel:

$$ V_{gross} = W \times H \times T $$

Where:

$W$ = panel width
$H$ = panel height
$T$ = panel thickness

If dimensions are in inches, the resulting volume is in cubic inches.

3.2 Net Volume¶

Openings and through-blockouts must be subtracted:

$$ V_{net} = V_{gross} - \sum V_{openings} - \sum V_{blockouts} $$

If the openings pass fully through the panel, each opening volume is:

$$ V_{opening} = W_o \times H_o \times T $$

3.3 Conversions¶

$$ 1 \text{ ft}^3 = 1728 \text{ in}^3 $$

$$ 1 \text{ yd}^3 = 27 \text{ ft}^3 $$

So:

$$ V_{ft^3} = \frac{V_{in^3}}{1728} $$

$$ V_{yd^3} = \frac{V_{ft^3}}{27} $$

4. Panel Weight Formula¶

For a normal-weight concrete panel:

$$ W_{panel} = V_{net,ft^3} \times 150 \text{ pcf} $$

This yields weight in pounds.

4.1 Example¶

Panel dimensions:

Width = 24 ft
Height = 30 ft
Thickness = 7-1/4 in.
One opening = 10 ft × 12 ft through panel

Convert thickness:

$$ 7.25 \text{ in.} = 0.6042 \text{ ft} $$

Gross volume:

$$ V_{gross} = 24 \times 30 \times 0.6042 = 435.0 \text{ ft}^3 $$

Opening volume:

$$ V_{opening} = 10 \times 12 \times 0.6042 = 72.5 \text{ ft}^3 $$

Net volume:

$$ V_{net} = 435.0 - 72.5 = 362.5 \text{ ft}^3 $$

Panel weight:

$$ W_{panel} = 362.5 \times 150 = 54,375 \text{ lb} $$

That is approximately:

$$ 54,375 \div 2000 = 27.2 \text{ tons} $$

5. Material Quantities¶

5.1 Concrete Quantity¶

Concrete is often reported in cubic yards for estimating and scheduling:

$$ V_{yd^3} = \frac{V_{net,ft^3}}{27} $$

Using the example above:

$$ 362.5 \div 27 = 13.43 \text{ yd}^3 $$

5.2 Form Area¶

For a simple slab-cast panel, the planning-level form face area is the gross panel face area minus openings if tracking face treatments, or gross only if tracking casting footprint.

$$ A_{gross} = W \times H $$

Use face-area metrics for:

Bond breaker coverage
Surface treatments
Finish-area estimating

5.3 Chamfer and Reveal Quantities¶

Chamfer strip and reveal strip quantities should be reported in lineal feet. See chamfers-and-edge-profiles.md.

6. Center of Gravity¶

The center of gravity is the geometric balance point of the panel’s net area or volume. In practical tilt-up workflows, it is usually tracked as:

Horizontal CG position (X)
Vertical CG position (Y)

6.1 Why CG Matters¶

CG drives:

Pick point layout
Rigging symmetry
Rotation during lift
Temporary brace load distribution
Whether strongbacks may be needed

If openings are large or asymmetrical, the CG can move noticeably away from the geometric center of the panel outline.

6.2 Conceptual Formula¶

For panel-face geometry, the centroid can be computed by subtracting the moments of openings from the gross panel moment:

$$ x_{cg} = \frac{A_g x_g - \sum (A_o x_o)}{A_g - \sum A_o} $$

$$ y_{cg} = \frac{A_g y_g - \sum (A_o y_o)}{A_g - \sum A_o} $$

Where:

$A_g$ = gross panel area
$x_g, y_g$ = gross panel centroid coordinates
$A_o$ = opening area
$x_o, y_o$ = opening centroid coordinates

For uniform-thickness panels, area centroid and volume centroid coincide.

7. Practical Documentation Rules¶

The following values should normally appear in a panel schedule or panel drawing package:

Panel weight in pounds
Panel weight in tons where useful for crane planning
Concrete quantity in cubic yards
CG location in X and Y
Lift insert count

These values are not optional niceties. They are core production data.

7.1 Standard Panel Schedule Fields¶

Field	Recommended
Panel mark	Required
Height	Required
Width	Required
Thickness	Required
Weight	Required
Concrete volume	Recommended
CG X / CG Y	Recommended
Lift insert count	Required

This aligns with the entity inventory documented in docs-developer/panel-entities.md, where panel weight, concrete volume, and CG are identified as core computed properties.

8. Allowances and Limits¶

Planning calculations should note that actual lift engineering may add or adjust for:

Hardware self-weight
Rigging hardware and spreader systems
Nonuniform thickness or recessed features
Blockouts or reveals not reflected in a simplified gross-minus-openings model
Concrete density variations from actual batch tickets

Where these effects are minor, panel-book calculations usually keep the standard 150 pcf net-volume method. Where they are significant, the engineer or lift consultant may publish a refined weight.

9. Common Mistakes¶

Frequent quantity and weight errors include:

Forgetting to subtract openings
Using gross area instead of net area for CG
Mixing inch-based and foot-based units in the same formula
Omitting deep reveals or blockouts from weight calculations when they materially change the section
Reporting panel weight without clarifying whether it is gross or net

These mistakes directly affect safety when lift hardware is selected.

10. ConstructiVision Defaults¶

Suggested defaults for generated documentation:

Parameter	Default
Concrete unit weight	150 pcf
Primary weight unit	pounds
Secondary weight unit	tons
Concrete quantity unit	cubic yards
CG output	X and Y from panel datum

10.1 Suggested General Note¶

PANEL WEIGHTS SHOWN ARE CALCULATED USING NET CONCRETE VOLUME AT 150 PCF U.N.O. FINAL LIFT DESIGN SHALL VERIFY PICK LOADS, INSERT CAPACITY, AND RIGGING CONFIGURATION.

11. Confidence and Source Quality¶

This page is based on:

High confidence: standard normal-weight concrete unit weight; net volume and centroid formulas; conventional panel-book scheduling practice
Moderate confidence: when simplified panel-book calculations are sufficient versus when refined lift-engineering adjustments become necessary

Sources: ACI 318-19 Section 26 material property conventions; ACI 551.1R Chapters 4 and 6; Dayton Superior Tilt-Werks design workflow references; panel measurement inventory in docs-developer/panel-entities.md; common tilt-up shop-drawing practice.