Officials now know why part of a parking ramp under construction fell a few inches Monday in Davenport. Project manager Jay Perry works for the general contractor. He says crews from Raiders Precast of West Burlington had welded the base of a vertical panel to some horizontal panels on the third floor. But he says they failed to put grout and shims in the joint to even the load. That caused a section in the middle of the ramp to fall a few inches, forcing evacuation of nearby businesses for fear the entire ramp would collapse. Some disassembly is needed to fix the problem, and it will delay the project five days. But city officials say taxpayers won’t have to pay for the mistake.