Stow SFG10E manual Defined Versus RandomTraffic Patterns, How to Define Surface Regularity

ASSEMBLY INSTRUCTIONS/OPERATIONS

but have different implications for the floor user. Flatness is critical where the user’s main concern is the behavior of wheeled type vehicles. Levelness is critical where the user’s main concern is with fixed structures such as shelving, racks and the placement of machine tools.

Exceptions exist, but for most users, flatness is more important than levelness. The reasoning is that fixed equipment can be shimmed or adjusted to compensate. However, it is not as easy to adapt a wheeled vehicle to a floor that is not flat enough to allow for proper action.

Flatness and levelness also have different implications for the floor contractor. Flatness is determined mainly by finishing methods. Levelness is determined mainly by the side forms.

Defined Versus RandomTraffic Patterns

Floors are subject to two kinds of traffic patterns: defined and random. On a defined traffic floor, vehicle movement is confined to fixed paths. On a random traffic floor, vehicles are free to roam, though inevitably, some traffic patterns are used more than others.

The distinction is important because the two kinds of traffic demand different methods of measuring surface regularity. On a defined traffic floor, a continuous (or nearly continuous) profile in each of the paths can be measured. But where traffic is random, the possible travel paths are infinite in number.What usually results is statistical sampling; selected points or lines are checked and assumed that they represent the whole floor surface.

The highest degree of surface regularity is found among the defined traffic floors. Defined traffic floors allow the designer and contractor to focus on a limited number of critical areas.When a defined traffic floors is out of tolerance, it is relatively easy to identify the defects for correction— usually by employing a grinding process.

How to Define Surface Regularity

Since the middle 1980s, new methods of defining surface regularity have been adopted as national standards. Older methods will continue to be utilized, although they are less effective. The following methods will be discussed:

1)The F number system for random traffic floors

2)The TR 34 system for defined traffic floors

Both methods are not of equal value. For random traffic floors, F numbers provide the most complete and consistent system. For defined traffic floors, the TR34 system is superior.

The F number system utilizes a pair of numbers to define surface regularity. The flatness number, Ff, is based upon the curvature over a horizontal distance of 24 inches. The levelness number, Fl, is based upon the floor slope over a horizontal distance of 10 feet. The standard test for F numbers is specified in ASTM E1155 and/or most recent version.

With both Ff and Fl, higher numbers mean greater surface regularity. Though the scale ranges from zero to infinity, almost all floors have F numbers between 10 and 100 for both flatness and levelness. Since the scale is linear, an Ff50 floor is exactly twice as flat as an Ff25 floor.

Most F number specifications are written in a two tier format. The overall F numbers apply to the floor taken as a whole. The local F numbers apply to each individual slab and are usually only one half to two thirds the overall values.

The overall F numbers are not just simple averages. ASTM E1155 covers how to combine F numbers.

The two tier format encourages contractors to achieve good surface regularity while allowing for minor defects. The attempt is to pour the entire floor to the specified overall F numbers. If, for instance, the construction crew has a bad day and fails to meet the specified overall numbers for the slab, the slab can still be accepted provided it meets the specified local numbers.

Such an occurrence serves as a warning to the crew that it must strive for a better performance on later slabs, so as to bring the overall F numbers up to the specified values. If a slab fails to meet even the specified local numbers, it must be repaired or replaced, but such failures seldom occur if all parties understand what is expected from the start.

Designers are not obligated to use this two tier format. Some designers specify a single F number pair (Ff and Fl) which applies to each individual slab. But this also raises the risk that slabs will be rejected.

FIGURE 40 depicts the overall and minimum F numbers for various floor classes. The floor classification is from the American Concrete Institute. Although the F number system is only a few years old, it offers these advantages:

a)The system controls both flatness and levelness.

b)There is a standard test method.

c)The system recognizes the statistical nature of profile testing on random traffic floors.

d)The system is infinitely variable.

SFG10E ELECTRIC SURFACE GRINDER — OPERATION AND PARTS MANUAL — REV. #1 (07/16/07) — PAGE 29