CALGARY, AB
MacKimmie Block & Tower Redevelopment
The MacKimmie Block and Tower at the University of Calgary aims to reduce and eliminate carbon emissions with a passive design that minimizes energy use.
The block and tower originally served as a library but were repurposed for administrative and classroom spaces, including 500 new study spaces for the faculties of Nursing and Social Work.
Comprising an existing 14-storey concrete frame tower and a five-storey steel framed block connected by a two-storey concrete link building, MacKimmie Block and Tower is the tallest building within the university’s main campus.
The complex is striving for certification with the Canada Green Building Council’s new Zero Carbon Building Standard, aiming to reduce and eliminate carbon emissions by designing passive controls and minimizing energy usage while optimizing interior comfort.
The redevelopment included adding two floors to the existing tower, replacing the existing cladding system with an energy efficient system, and improving the quality of the interior light.
PROJECT HIGHLIGHTS
CLIENT
University of Calgary
ARCHITECT
DIALOG
OUR ROLE(S)
Structural Engineering Consultant
SIZE
16,820 m² (181,000 ft²)
BUDGET
$240 Million
MARKET (OFFICE)
CALGARY
KEY CONSIDERATIONS
Challenge One
An inefficient cladding system led to poor thermal performance.
Solution One
An innovative inner and outer curtain wall system was used to greatly improve thermal performance for this building, with solar PV fully integrated within the curtain wall system as the building strives for net zero.
Challenge Two
Designing an addition of two floors to the existing building.
Solution Two
Entuitive completed an extensive study of the existing tower structure and determined that removing the heavy library loads, utilizing live load reduction allowed by the current code, and removing the heavy precast panels allowed the addition of two levels without any modifications to the robust lateral load resisting system.
Challenge Three
Rebar cages were found to be misaligned in some of the columns in MacKimmie Tower, leading to a reduced concrete cover, potentially exposing the rebar steel to higher temperatures in fire scenarios. Any fire engineering interventions are limited by the boundaries of the existing structure. Ideally, it can be proven that the existing condition is safe in fire without any interventions. Naturally, eliminating the need for repair/upgrading work entirely is the least invasive/easiest solution for the contractor.
Solution Three
A thermal analysis of the column sections with misaligned rebar cages allowed us to determine the impact on material degradation, and hence load-bearing capacity under fire that the reduced concrete cover had. The impact of misaligned rebars was found to not have a significant impact on the residual load-bearing capacity, and no remedial works were necessary.
Challenge Four
To strengthen waffle slab floors after coring these to accommodate mechanical and electrical services, steel plates were attached to the soffit of the floor slabs. Since the steel plates would be exposed to fire from below, it was necessary to determine whether they required fire protection to maintain the load-bearing capacity of the overall floor in case of fire.
Solution Four
Calculation of the residual load-bearing capacity of the existing concrete waffle floor slab, including cores, based on the Canadian concrete design standard CSA A23.3 Annex B and Eurocode 2 Part 1-2, as well as using the load combination for extreme events in NBCC 2015, demonstrated that the floor slab maintained sufficient load-bearing capacity in fire without relying on any contribution from the steel plates. This meant that fire protection of the steel plates was redundant in the event of a fire, and resulted in a significant cost savings relative to the prescriptive guidance, which stated to apply spray-applied fire protection to the exposed steel.
GALLERY
