Resistance and durability indices

More in this section

• Hybrid grass
• Innovation
• Performance and safety
• Resistance and durability
• Ecology and savings
• A forward-looking choice
• Types of Playing Fields
• Resistance and durability indices
• Precautions
• FAQ 01 Key Features
• FAQ 02 Application Areas
• FAQ 03 Comparing Savings
• FAQ 04 Market Demand
• FAQ 05 Duration Comparison
• FAQ 06 Comparing maintenance processes
• FAQ 07 Multidisciplinary Fields
• FAQ 08 Water Consumption
• FAQ 09 Frost and Heat Resilience
• FAQ 10 Innovative Value

A recurring doubt for football field managers is the following question: "Can the POWERgrass field be the best solution for our case?"

Although everyone agrees that playing on a hybrid field brings more benefits and safety of play compared to a natural or synthetic field, and despite cost/benefit analysis, also shows that the economic, environmental, and hydrogeological advantages are favorable throughout the life cycle of the system, the doubt that the natural grass may deteriorate tends to scare inexperienced operators. To this end, in order to understand if the hybrid field is the right choice, you need to refer to 1) the weekly use index, 2) the annual usability index, and 3) the total duration index to guide the choice, based on the actual usage data.

1) Weekly Use Index - WUI (Weekly Usage Index)

Although POWERgrass, in its "Heavy Duty" version, has a high number of very resistant fibers that allow you to play without the aerial part of the grass, the aim of a hybrid field is to play on natural grass, so you need to check the weekly use index (WUI) of your own field.

The WUI calculates the maximum weekly game load exerted by players on a specific surface and is calculated with the following formula:

WUI = U_w x P_m ÷ A

where:

• U_w : the number of hours the field is used per week
• P_m : the average number of players on the field
• A : the surface area of the playing area

For example, an 11-a-side field with a playing area of 100x60 meters that is used for about 30 hours a week by about 22 players would have a WUI of 30x22÷6000 = 0.11. The following table performs a calculation for some types of fields.

1) Weekly Utilization Index - WUI
Description	Hours	Players	Area	WUI
PRO Soccer	30	22	7140	0.09
Amateur Soccer	30	22	6000	0.11
Rugby	30	30	7000	0.13
Amer. Football	30	22	4500	0.15
Five-a-side-Football	30	18	2400	0.23
Seven-a-side Football	30	14	1500	0.28
Five-a-side Football	30	10	800	0.38
Calculation of WUI peak at Regent's Park, London
POWERgrass	50	22	6000	0.18

The goal of the index is to objectify the ability to maintain good coverage of natural grass over at least 75% of the playing surface during the sports season, while accepting a substantial reduction during the winter months.

In general, a POWERgrass hybrid field is recommended as long as the WUI reaches a peak of 0.18, as recorded at Regent's Park, London, although there are reports from Grosseto of higher usage.

2) Annual Fruition Index - AFI

This index calculates the total annual hours in which the field is occupied for matches or training by the number of players on the field using the following formula:

 

AFI = U_w x P_m x W_y

where:

• U_w : the number of hours the field is used per week
• P_m : the average number of players on the field
• W_y : the number of weeks of annual use

To estimate the annual feasibility index, also considering climate changes during the season, a good rule is to set a limit of 40 weekly playing hours during the growing period from mid-March to mid-June and September to November while in winter months (December, January and February and up to mid-March) possibly reduce to 20 weekly hours (26 weeks at 40 hours + 13 weeks at 20 hours = 1300 annual hours) then multiply the hours in which the field is feasible by the number of players present on the field. In our example calculating 22 players present on the field we can estimate an annual feasibility index of 28.600 hours of presence (1300 annual hours per 22 players) which meets the requirements of an artificial grass field with a high frequency of use. The following table performs a calculation in a football field in a competitive season.

2) Annual Usability Index - AFI
Description	Hours	Player.	Weeks	AFI
Spring - Fall	40	22	26	22 880
Winter	20	22	13	5 720
Average Weekly Game	33		39
Average in 52 weeks	25		52
Annual Usability Index - AFI				28 600
Calculation of the AFI at Regent's Park, London
POWERgrass	23.9	22	52	27 342

This index provides an estimate of the annual attendance hours on the field and can also be a basis for the average cost for stipulating subscriptions with individual players.

The annual use index can be measured through the installation of a attendance meter and managed through a dedicated application. Furthermore, it is advisable to highlight the average age of the athletes to collect useful data related to the average weight of the athletes.

3) Index of guaranteed duration (the number of annual usability per the number of guaranteed years)

The duration guarantee index derives from the multiplication of the annual usability index for the years of granted warranty and a test that the system producer places in the product but subject to certain conditions of use and maintenance and is calculated with the following formula:

LWI = AFI x Y_w

where:

• AFI = Annual Usability Index
• Y_w = warranty years of the system

For example, if the field is guaranteed for 5 years for 20,000 hours of attendance, this means that the warranty operates for one of the

3) Indice di durata garantito - LWI
Description	AFI	Anni	LWI
POWERgrass	20 000	5	100 000

The guaranteed duration index of the system is an index that investors take into consideration in the amortization plan of the field because its useful life or total usability depends on it, a bit like the total mileage of a car or the total hours the use of a work vehicle.