Höfðatorg multi-storey office building

The project's objective

Höfðatorg, is a multi-storey office building (14,000 m²) in downtown Reykjavik, that houses Reykjavík City Service Centre and 450 employees. The building consists of many large open-plan (landscape) offices, conference rooms and halls, a canteen and a large reception hall on the first floor.

Acoustics

EFLA Consulting Engineers (formerly Linuhonnun Consulting Engineers) oversaw the acoustical design of Höfðatorg. A Swedish building standard (SS 02 52 68) was used for the acoustical design of the open-plan offices, where a design criteria of reverberation time should be less than 0.4 s. The standard was also used in the acoustical design of the canteen and the meeting rooms. An additional requirement of the reverberation time in the reception hall was concluded to be less than 0.5 s.

With high quality absorbers on the walls and absorbing screens, in addition to the absorptive ceiling, the design goals were reached for every designed space, according to calculations.

After the construction was fully completed, measurements were made on the reverberation time in the open-plan offices and demonstrated that the design specifications had been achieved.

Fire safety and fire system design straties for the car park

The work comprised of development of a fire safety strategy and fire system design strategy for the underground car park and the connection to the buildings above.

The establishment of design fires and detailed modelling of fire growth and spread with extensive CFD calculations were used to determine the smoke extract design and the safety of people and the building structure. Evacuation calculations were carried out to ensure the safety of people, that resulted in increased distances between the emergency exits.

A probabilistic risk analysis was conducted. Fault trees and event trees were used to calculate the probability of a fire in the structure together with the risk of spread between cars as well as the probability of a probable worst case scenario.

With extensive fire safety calculation and a holistic risk approach, the fire safety measures could be optimized regarding safety of people and building cost.

Risk analysis and fire design

The project consisted of a quantitative risk analysis (QRA) for the new 19-floor building, Höfðatorg. To do this, QRA software was used to simulate the uncertainties of the variables, the probability of different events and the consequences in the case of fire.

Current Icelandic building regulations do not account for buildings higher than eight floors, and cannot be applied to a 19-floor building without modifications. To make sure that the level of safety is as high in Höfðatorg as in lower buildings built according to the regulations; the fire safety was analysed from a risk perspective where it is compared to an eight-floor building, built according to the regulations' specifications.

In addition to theoretical risk analysis, practical tests were done to investigate the travel time for fire fighters. The findings of the fire risk analysis and the tests were afterwards used in a scientific article presented at the SFPE?s 7th international conference on performance-based codes and fire safety design methods.

A performance-based fire design was applied to the two-floor parking structure, each floor consisting of 8000 m² floor area. With a total of 800 parking places makes the it one of Iceland's largest underground parking structures. The parking has a complicated layout with large open areas. Seven buildings, with the height of seven to 19 floors, are planned to connect to the underground parking structure.

EFLA's role

• Risk analysis
• Fire design
• Acoustical design