WORCESTER — One of the most expensive public construction projects in the state’s history, set to open Thursday, looks in some ways like a sprawling deluxe residential complex. Bedroom windows face landscaped greenery, modern light fixtures illuminate wide corridors, and recreation rooms feature new treadmills and pool tables.

Yet within this $302 million structure, there is clearly a sober­ness of purpose. The ceiling light fixtures lack any parts that could be used to help residents hang themselves. The lights’ on-off switches are partly covered to avoid deliberate electrocution. The walls are made of a high-impact material to ­absorb fist-pounding and kicking.