Unreinforced elastomeric washers N15 and N20

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Product description

for supporting girders, beams, binding joists, ceilings, etc.

Are used for heavy loads up to 15 N/mm2 (N 15) or up to 20 N/mm2 (N 20)

Unreinforced elastomeric washers ensure that the load is transferred to the support in a controlled manner, and they ensure free rotation on the support and reduce the impact related to the horizontal displacement of the supported element. They prevent excessive load eccentricities and stress concentrations at the edge of the support, while compensating for unevenness and deviations of adjacent surfaces.

1. Technical and assembly instructions.

N 15 and N 20 unreinforced elastomeric washers are produced in thicknesses of 5 mm, 10 mm, 15 mm and 20 mm. The shorter side should be at least five times the thickness of the washer. The washer should be placed in the area of the static reinforcement of the support and the supported element.

2. Unreinforced elastomeric washers should be used mainly when static loads are present. For dynamic loads, reinforced elastomeric washers should be used.

Unreinforced elastomeric washers included in bearing class 2 can only be used if the long-term load share is 75% or more. In other cases where overloading or damaging the washer may lead to the loss of stability of the structure, we recommend using steel-reinforced elastomeric washers.

3. The load perpendicular to the spacer surface (surface load)

According to the currently binding inspection criteria of the Building Research Institute (Instytut Techniki Budowlanej), unreinforced elastomeric washers under certain load conditions may compress by 30% with respect to their initial thickness. In the following design tables, the maximum linear flattening has been limited to approximately 20% to provide additional safety in the event of possible assembly inaccuracies.

4. Design guidelines

The load perpendicular to the spacer surface (surface load)

The load parallel to the bearing plane (shear deformation), protection against displacement

The maximum allowable deformation angle and the displacement are calculated as follows:

tan γ - the deformation angle [-],
t - the washer thickness [mm],
w - he characteristic displacement [mm].

Permanent loads parallel to the bearing plane are not allowed. For short-term loads, it is recommended to fulfil the condition of protection against the displacement:

H1 = the characteristic external horizontal load [N],
H2 = the characteristic internal force resulting from the deformation [N],
tan γ = the deformation angle [-],
G = the shear modulus (1,5 N/mm²),
F = the characteristic surface load [N],
a,b = the length of washer sides [mm].

In the case of short-term external horizontal loads, the maximum permissible deformation angle should not be exceeded.

Rotation angle

The permissible rotation angle resulting from elastic and plastic deformation of the supported element and partly from unevenness and bevel of the surface is calculated as follows:

α = the characteristic torsion angle

When dimensioning the structure elements, the possibility of the load eccentricity caused by the washer deformation should be taken into account.

e = the eccentricity

Transverse tensile forces due to linear deformation of the washer

Transverse tensile forces due to linear deformation of the washer

Zq = the transverse tensile force [N]
F = the surface load [N]
t = the washer thickness [mm]
a = the shorter side of the washer [mm]

In order for the support to absorb the transverse tensile force, additional reinforcement must be made in the support element.

Stiffness

If at least two washers of different sizes are placed in one line under one component, the following proportion must not be exceeded:

Specification: t x b x l mm RUBA N 15 or N 20 type

5. Specification: t x b x l mm RUBA N 15 or N 20 type

the total thickness of 5 mm: the load in kN

N15										N20
[mm]	50	75	100	125	150	175	200	250	300	[mm]	50	75	100	125	150	175	200	250	300
50	38	56	75	94	113	131	150	188	225	50	47	75	100	125	150	175	200	250	300
75	56	84	113	141	169	197	225	281	338	75	75	113	150	188	225	263	300	375	450
100	75	113	150	188	225	263	300	375	450	100	100	150	200	250	300	350	400	500	600
125	94	141	188	234	281	328	375	469	563	125	125	188	250	313	375	438	500	625	750
150	113	169	225	281	338	394	450	563	675	150	150	225	300	375	450	525	600	750	900
175	131	197	263	328	394	459	525	656	788	175	175	263	350	438	525	613	700	875	1050
200	150	225	300	375	450	525	600	750	900	200	200	300	400	500	600	700	800	1000	1200

The shortest length of the side is 50 mm.

the total thickness of 10 mm: the load in kN

N15										N20
[mm]	50	75	100	125	150	175	200	250	300	[mm]	50	75	100	125	150	175	200	250	300
50	12	25	42	52	63	73	83	104	125	50	12	25	42	52	63	73	83	104	125
75	25	59	103	141	169	197	225	281	338	75	25	59	103	154	211	246	281	352	422
100	42	103	150	188	225	263	300	375	450	100	42	103	188	250	300	350	400	500	600
125	52	141	188	234	281	328	375	469	563	125	52	154	250	313	375	438	500	625	750
150	63	169	225	281	338	394	450	563	675	150	63	211	300	375	450	525	600	750	900
175	73	197	262	315	378	459	525	659	788	175	73	246	350	438	525	613	700	875	1050
200	83	225	300	375	450	525	600	750	900	200	83	281	400	500	600	700	800	1000	1200

The shortest length of the side is 50 mm.

the total thickness of 15 mm: the load in kN

N15										N20
[mm]	75	100	125	150	175	200	250	300	350	[mm]	75	100	125	150	175	200	250	300	350
75	26	46	69	94	109	125	156	188	219	75	26	46	69	94	109	125	156	188	219
100	46	83	129	180	236	269	370	444	519	100	46	83	129	180	236	296	370	444	519
125	69	129	203	281	328	375	469	563	656	125	69	129	203	291	388	493	625	750	875
150	94	180	281	338	394	450	563	675	788	150	94	180	291	422	525	600	750	900	1050
175	109	236	328	394	459	525	656	788	919	175	109	236	388	525	613	700	875	1050	1225
200	125	296	375	450	525	600	750	900	1050	200	125	269	493	600	700	800	1000	1200	1400
250	156	370	469	563	656	750	938	1125	1313	250	156	370	625	750	875	1000	1250	1500	1750

The shortest length of the side is 75 mm.

the total thickness of 20 mm: the load in kN

N15										N20
[mm]	100	125	150	175	200	250	300	350	400	[mm]	100	125	150	175	200	250	300	350	400
100	47	72	101	133	167	208	250	292	333	100	47	72	101	133	167	208	250	292	333
125	72	114	163	218	277	407	488	570	651	125	72	114	163	218	277	407	488	570	651
150	101	163	237	321	413	563	675	788	900	150	101	163	237	321	413	618	844	984	1125
175	133	218	321	440	525	656	788	919	1050	175	133	218	321	440	572	869	1050	1225	1400
200	167	277	413	525	600	750	900	1050	1200	200	167	277	413	572	750	1000