PORTLAND —Portland firefighters say a downtown building that was evacuated after its facade cracked and buckled is not at risk of collapsing.Fire Battalion Chief Andy Ponce said Tuesday that engineers have determined the 10-story Fifth Avenue Building is structurally sound. However, it will remain closed to workers and scaffolding will be placed around the facade to protect pedestrians on nearby sidewalks.The structure in the heart of Portland’s downtown was evacuated before noon Tuesday. Workers reported hearing a loud bang before being told to get out. Emergency crews responded to reports of cracks in the facade and falling debris.The building dates to 1951 and the crack is in its lower half.It houses employees from eBay, FedEx, a fitness center, a day care and offices for Oregon Health & Science University.Trimet and C-Tran operations were disrupted in the area. Both MAX and bus lines were diverted around the evacuation area.