During a typical week last year, 276 Chicago apartments were in buildings that fell into foreclosure, creating upheaval for families who were unsure how long they’d be able to stay in their units. Some faced intimidation and threats from property agents seeking to evict them. The Lawyers’ Committee for Better Housing, in a study scheduled to be released Tuesday, calls for more stringent protections for renters at a time when affordable housing options within the city are shrinking and rents are on the increase. The report comes as a group of Chicago aldermen is expected to propose an ordinance this week that would force owners of repossessed apartment buildings, including those owned by Fannie Mae and Freddie Mac, to continue renting apartments to law-abiding, rent-paying tenants even after the buildings have been repossessed. The proposal calls for the rental relationships to continue, even if there was no written lease, until the building was sold.