In this building the wall panels were secured to the purlins with paired strap ties that were attached to the adjacent ledger bolts as shown, and to the purlin with only one through bolt. All of these strap ties were covered up with the silver insulation paper, and only exposed when a moisture problem required the removal of the insulation paper around the perimeter of the building.
Even when installed correctly, these strap ties will not perform well during an earthquake, as their capacity will be limited by the single through bolt in the purlin, and are likely to deform significantly when loaded.
Another perspective of the strap tie shown in the previous photo. Note the use of MI washers at the purlin bolt. In general, it is recommended that A36 plate washers be used instead of MI washers, as MI washers tend to be weak and brittle in comparison to plate washers.
As can be seen, these strap ties were installed at an excessive skew, as well as with significant slack. Due to the significant deformation this connection is expected to undergo when loaded, it will be almost useless during an earthquake.
Another paired strap tie installed with excessive skew. Even though the straps appear to have been installed tight, this connection is still likely to be relatively useless during an earthquake. Note the panel joint to the left of the purlin.
Another paired strap tie installed with excessive skew and slack that will be effectively useless during an earthquake. Such installations will not keep the ledger from being subjected to cross grain bending.
Another perspective of the previous photo. This building was eventually retrofitted, the strap ties abandoned and removed, and the wall panels secured to the purlins with XT46-6's.
A misaligned and poorly installed strap tie projecting down at an excessive vertical skew. Again this wall tie will be relatively useless during an earthquake. We find it interesting how all of the poorly installed strap ties throughout this building were conveniently covered up with the silver insulation paper. Fortunately they were discovered and dealt with before the building was subjected to a major earthquake.