# ACI F-MIN NUMBER SYSTEM

In America, and areas of American influence, surface profiles are controlled differently on floors that have defined traffic patterns compared to free movement floors.

The most practical way to measure a defined traffic floor is by making continuous Profileograph measurements of each path. Such direct measurement will usually involve point separations other than 300mm or 3000mm. FF and FL cannot be used since they are random measurements across the entire slab. There is a great probability that significant floor defects in the wheel path will be missed; furthermore, if one did measure each individual wheel paths with a random traffic measuring device the results are an average at best and F-min cannot be averaged. Therefore, there is no direct correlation between FF/FL and F-min. The FF/FL and F-min systems are completely different measuring systems and there is no corresponding index for comparison purposes. A single F-number “F-min” is therefore used to define the worst acceptable flatness and levelness conditions in a VNA aisle, and this F-min value is assigned based on the expected lift truck and rack height as in Table 1.1 overleaf.

## Equations

The equations shown translate F-min into specific dimensional restrictions (metric version)

Where:

dL = maximum difference in elevation measured over gauge length L, in mm.

EL max = maximum change in dL for each 300mm of travel across the floor.

L = the horizontal distance over which the measurements are to be made (normally the wheelbase and the load wheel track of the forklift truck), in mm.

F min = the face floor profile number for defined traffic surfaces (dimension-less).

## Checking F min specification

F min specification being checked with a Face Profileograph.

## Transverse Graphs F min

The data can be extrapolated to determine compliance with any F-min number specified. The resultant differential graphs are colour coded, scaled and easy to read.

ACI F min Classifications and Values and Table 1.1

Classification F-min number
Conventional floor 25
Good 38
Flat 50
Very flat 75
Superflat 100

Table 1.1 taken from ACI 360-R10 “ Design of Slabs-On-Ground”

Rack height, ft (m) Longitudinal* F-min Transverse† F-min
0 to 25 (0 to 7.6) 50 60
26 to 30 (7.9 to 9.1) 55 65
31 to 35 (9.4 to 10.7) 60 70
36 to 40 (11 to 12.2) 65 75
41 to 45 (12.5 to 13.7) 70 80
46 to 50 (14 to 15.2) 75 85
51 to 65 (15.5 to 19.8) 90 100
66 to 90 (20.1 to 27.4) 100 125

## ACI F min Tables

The ACI F min table, and Table 1.1 taken from ACI 360R-10, “Guide to Design of Slabs-On-Ground” give the F-min number based on Classification and Height of racking.

dL and EL max limits are calculated for both Transverse and Longitudinal components, by using the equations above and inputting the transverse and longitudinal axle separations of the forklift truck, as well as the Fmin number assigned to the floor.

Defined Traffic Values, table 1.1 shows the recommended F-min values for varying rack heights.

*Longitudinal value between the front and rear axle

† Transverse value between loaded wheel tracks

## TR34 4th Ed Chapter 3

The Concrete Society’s TR34 (4th Ed) Chapter 3

(Current Version)

(2008)

## Flatness Comparisons

Comparison table for Defined Movement Specifications

## TR34 3rd Ed Chapter 4

The Concrete Society’s TR34 Free Movement (3rd Ed) Chapter 4

(Previous Version)*

* The Concrete Society’s TR34 3rd edition was superseded by the 4th edition in August 2013.
† Replaced 2021. New version has no flatness requirement.