A new type of symmetric slip-friction connector

• Slip friction (slotted bolt) connectors' elasto-plastic behaviour improved.
• Shims not required
• Abrasion resistant steel on mild steel provides stable symmetric sliding.
• Results equal to or superior to current connectors with brass shims
• Proposed connector will save on fabrication costs, and avoid galvanic corrosion.

In recent decades, there has been increasing interest in the use of slip-friction connectors (or slotted-bolt connectors) to dissipate energy in earthquake resistant structures. These devices, which rely on the friction controlled sliding of steel plates, have already seen implementation in buildings with steel moment resisting frames, with the intention that non-linear behaviour is concentrated at the connectors themselves, thereby protecting the structure from damage. The sliding mechanism of slip-friction connectors can be either symmetric or asymmetric. In the case of symmetric connectors, brass shims have, up until now, been required to ensure stable elasto-plastic behaviour. However brass can be expensive, and sometimes difficult to procure. A new type of symmetric connector that entirely eliminates the need for shims of any kind is proposed. The centre-plate of the connector consists of abrasion resistant steel that is in direct contact with the mild steel plates between which it slides. From experimental testing, the performance of the proposed connector is found to be equal, if not superior, to that of traditional symmetric connectors with brass shims. The proposed connector maintains strength and stiffness over a large number of cycles of loading, and although minor pre-conditioning of the sliding surfaces may be required in order to improve behaviour, is nevertheless simpler, and likely to be cheaper, than its current equivalent with brass shims. The potential for galvanic corrosion is also avoided.