Rigidity evaluation of pre‐stressed rubber bearings of long‐span roofs

When The Great East Japan Earthquake of 2011 occurred, long‐span structures such as gymnasium with long‐span steel ceiling supported by RC columns was damaged as the bearings, which connected the steel roof column and the RC columns, were damaged. In this study, two effective improvements to prevent the pull‐out of anchor bolts and crushing of base mortar are proposed. The first improvement is to add disk springs between the base plate and anchor bolt nuts, which prevents the pull‐out of anchor bolts. In the second improvement, an elastic rubber plate is inserted between the base plate and mortar to avoid mortar crushing. Based on test results, an evaluation method for rotational stiffness is proposed, which can be calculated from the stiffness corresponding to the pre‐stressed force, disk spring, anchor bolts, and rotational spring constant of the rubber. This manuscript reports constant vertical and cyclic horizontal test of pre‐stressed rubber bearings.