Design

Using Durbar®

Durbar is a non-slip raised pattern floor plate of integral manufacture (the pattern is rolled in not welded). The "tear drop" studs are distributed to give maximum slip resistance in a variety of applications whilst ensuring a free draining surface.

The nominal gauge of Durbar is the thickness of the plain plate exclusive of pattern.

Unit Area Density

Thickness on plain Mass
(mm) (kg/m2)
3 26.83
4.5 38.59
6 50.36
8 66.04
10 81.73

12.5

101.34

Capacity Tables

It is usual to consider floor plates as supported on all four edges although stiffeners or joint covers may only support two edges. If the plates are securely bolted or welded to the supporting system, they may be considered as encastré. This increases the load carrying capacity slightly but reduces the deflection considerably.

The thickness given is exclusive of any raised pattern i.e. on plain.
The breadth is the smaller dimension and the length the greater, irrespective of the position of the main support members.
The maximum uniformly distributed load on the plate (w) is given by Pounder's formula and the maximum skin stress is limited to the design strength py

For calculating the maximum deflection (dmax) at serviceability, the uniformly distributed imposed load (wimp) on the plate is derived as follows.

w = gdead wdead + gimp wimp
wimp = (w - gdead wdead)/ gimp

For plates simply supported on all four edges

This formula assumes that there is no resistance to uplift at plate corners.

w = a1 py t2 / k B2 [ 1 + a2(1-k) + a3(1-k)2]
dmax = a4 k wimp B4 [1+a5(1-k) + a6(1-k)2] / E t3

Where resistance to uplift at corners is provided, the above formula will be conservative. Higher values may be obtained by assuming encastré status as outlined below.

For plates encastré on all four edges

The plate must be secured to prevent uplift, which would otherwise occur at the plate corners.

w = a7 py t2 / k B2 [ 1 + a8(1-k) + a9(1-k)2]
dmax = a10 k wimp B4 [1+a11(1-k) + a12(1-k)2] / E t3

Where:

L = length of plate (mm) (L > B)
B = breadth of plate (mm)
t = thickness of the plate on plain (mm)
k = L4/(L4+ B4)
py = design strength of plate ( 275 N/mm2 or 355 N/mm2)
E = Young's modulus (205 x 103 N/mm2)
1/m = Poisson's ratio (m = 3.0)
gdead = load factor for dead load (1.4)
gimp = load factor for imposed load (1.6)
dmax = maximum deflection (mm) at serviceability due to imposed loads only
w = uniformly distributed load on plate (ultimate) (N/mm2)
wdead = uniformly distributed self weight of plate (N/mm2)
wimp = uniformly distributed imposed load on plate (N/mm2)
a1 to a12 are constants as below:

Constant Value
a1 = 4/3
a2 = 14/75
a3 = 20/57
a4 = (5m2 -5)/32m2
a5 = 37/175
a6 = 79/201
a7 = 2
a8 = 11/35
a9 = 79/141
a10 = (m2 -1)/32m2
a11 = 47/210
a12

= 200/517

 

Durbar ultimate load capacity –various sized plates

Fixed on all four sides (encastré)

The ultimate uniformly distributed load for various sizes of Durbar plates fixed on all four sides and stressed to 275N/mm2 can be determined by using the table. The values are based upon equations developed by C.C. Pounder and conform to the construction and fixing requirements in BS 4592-5 : 2006.  The values in the tables are theoretical; in-use performance may vary. This information should not be used without the advice of a qualified structural engineer. Users of this information should satisfy themselves that it is suitable for their purpose.

Ultimate load capacity (kN/m2) for Durbar fixed on all four sides and stressed to 275N/mm2 

Values obtained with plates secured to prevent uplift

Thickness (t)   Ultimate distributed load (kN/m2) for length, L, (mm)
(mm) Breadth, B, (mm) 600 800 1000 1200 1400  1600  1800  2000 
3 600  21.2  16.3  14.9  14.3  14.1  13.9  13.9  13.8
  800    10.7§  8.4§  7.5§  7.1§  6.9§  6.8§  6.7§
  1000      5.6§  4.6§  4.2§  3.9§  3.8§  3.7§
  1200        3.4§  2.9§  2.6§  2.5§  2.4§
  1400          2.3§  2.0§  1.8§  1.7§
4.5 600  47.7 36.8 33.5  32.2  31.6  31.4  31.2  31.1 
  800    26.8 21.5  19.5  18.6  18.1  17.9  17.7 
  1000      17.2 14.2  12.9  12.2  11.8  11.6 
  1200        10.8 § 9.1 § 8.2 § 7.7 § 7.4 §
  1400          7.0 § 6.0 § 5.5 § 5.1 §
6 600  84.8 65.4  59.5  57.3  56.2  55.7  55.5  55.3 
  800    47.7 38.3  34.7  33.1  32.2  31.7  31.5 
  1000      30.5 25.3  22.9  21.7  21.0  20.6 
  1200        21.2 18 16.3  15.4  14.9 
  1400          15.6 13.4  12.3  11.6
8 600  150.8 116.2 105.9 101.8 100 99.1 98.6 98.3 
  800    84.8 68.1  61.7  58.8  57.3  56.4  56.0 
  1000      54.3 44.9  40.7  38.6  37.4  36.7 
  1200        37.7 31.9  29.0  27.4  26.5 
  1400          27.7 23.9  21.8  20.6 
10 600  235.5 181.5  165.4  159.1  156.2  154.8  154.1  153.6 
  800    132.5 106.4  96.4  91.8  89.5  88.2  87.4 
  1000      84.8 70.2  63.7  60.3  58.4  57.3 
  1200        58.9 49.9  45.4  42.9  41.3 
  1400         43.3 37.3  34.1  32.2 
12.5 600  368.0 283.6  258.4  248.6  244.1  241.9  240.7  240.0 
  800    207.0 166.2  150.7  143.5  139.8  137.8  136.6 
  1000      132.5 109.7  99.5  94.2  91.2  89.5 
  1200        92.0 77.9  70.9  67.0  64.6 
  1400          67.6 58.3  53.3  50.3 
†. Stiffeners should be considered for spans in excess of 1100mm to avoid excessive deflections.
§. Loads have been limited so that deflection ≤B/100 at serviceability, where serviceability is due to the imposed load only