K Series is a range of structural bearings that are proven by their design and operation for the last 25 years. The standard range comprises multi-axis rotation bearings in fixed, constrained (or guided) and free configurations to support loads up to 6,744 Kips. Current design practice has demonstrated the need for a range of bearings with higher horizontal load capacity.
Ekspan has a range of bearings to meet the full requirements for European (EN 1337) and American (AASHTO LRFD) standards for mechanical pot bearings.
K series bearings are available in three types:
Fixing holes are provided in the top and base members of the bearings. This enables a variety of fixing methods to be used. Standard fixtures are designed to ensure the bearings can be removed as simply as possible.
Support and Installation:
Important - See pages 21 - 23 of the brochure for Installation and Maintenance. If the bearings are to be installed on a steel spreader plate Ekspan must be notified. The overall height will be reduced by 3mm in these cases.
Where suitable reinforcement of the concrete has been provided the allowable concrete stress is dependent on the relative dimensions of the bearing/structure interface, the total support area and the characteristic strength of the concrete.The stress on the structure should, therefore, be checked to ensure that it is acceptable. At the nominal rating capacity tabulated, the mean stress approaches 2900 psi.
The designation of loadings varies depending on the design code employed. The tabulated load capacities list nominal rating, at which load the base concrete stress is 2900 psi maximum. The working stress/serviceability limit state maximum loads are determined by the allowable PTFE stresses. The ultimate limit state maximum load characteristics are determined by the strength characteristics of the bearing and incorporate the material and partial safety factors m and f3. The practice of stating working loads, or nominal loads, is inappropriate for limit state designs. The SLS and ULS capacities represent design load effects, i.e. nominal loads to which ALL the appropriate factors have been applied. Factored loads must be provided to ensure correct bearing selection.
All the bearings can rotate at least 0.01 radians around any horizontal axis. The maximum for each bearing is shown in the tables.
The dimensions for the 21K & 31K (Constrained) and 22K (Free) bearings are shown in the tables for the following movements -
21 & 31K 100mm total
22K 100mm total
21 & 31K NIL (see pages 14 & 16)
22K 20mm total
Movements in increments of 50mm total can be supplied. The top plate dimensions and the top plate fixing centers should be increased accordingly.
N.B. 21 & 31K bearings should not be used where movement is required at right angles to the constraints. The required movements should be specified in the part number as described below. The clearance between the constraints must not be used to accommodate any structural movement.
Bearing design loads:
Bearings should be selected to suit the appropriate design code. The maximum vertical and horizontal loads shown in the tables may be taken in combination.
The 20K fixed bearing will resist a horizontal force acting in any direction. In order for the bearing to support the maximum horizontal loads stated in the tables, a minimum concurrent vertical load of 0.33 x the nominal vertical rating must be present. At ULS, the actual load combination may permit the use of a vertical load higher than that shown in the table. Where higher horizontal load capacities are required, the 30K series or a special bearing may be more appropriate. We are pleased to advise.
Where suitable reinforcement of the concrete has been provided the allowable concrete stress is dependent on the relative dimensions of the bearing/structure interface, the total support area, and the characteristic strength of the concrete.The stress on the structure should, therefore, be checked to ensure that it is acceptable. At the nominal rating capacity tabulated, the mean stress approaches 2900 psi.
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