The owners of the 100 Pearl St. office tower and the building’s signature tenant, Hartford HealthCare, are partnering on the upgrades that will include the installation of a glass “cube” patterned after Apple’s on Fifth Avenue in New York, intended to signal Hartford HealthCare’s commitment to innovation. The improvements are part of a larger, up to $24 million renovation planned for the two-towered office building joined by an atrium. The costs are being split by Hartford HealthCare, the parent of Hartford Hospital and six others in Connecticut and building landlord, Shelbourne Global Solutions LLC, of Brooklyn, New York. The upgrades for the plaza include the removal of concrete planters that will be replaced by a landscaped plaza enclosing a new seating area with posts that will provide illumination at night. The clock tower will be repaired so it will once again show the time. It also is possible there will be an LED video wall displaying health-related messages from Hartford HealthCare.