Trendfire safety
A number of models were constructed and analysed using ABAQUS Finite Element Modelling (FEM) program. This is capable of including complex, non-linear geometry and realistic, temperature dependent material properties. This level of complex analysis allowed us to determine overall robustness of the proposed structural design, and in doing so highlighted a few fire case specific issues relating to cracking in the slab over certain protected beams and protection to columns. Such behaviours cannot be found by applying prescriptive fire protection only. By understanding the structural performance in fire, we were able to mitigate these issues by provision of additional rebar and additional protection materials, and so increasing the relative robustness of the structure. It also enabled the use of unprotected secondary steel beams, with the associated benefits of efficient material use and impact on programme, and therefore cost savings. By conducting this structural fire analysis early in the design process, it was possible to investigate a number of structural and fire protection options, and return an optimised design where the level of building safety was not compromised. Acceptance of the structural fire analysis was gained in January 2007. It is understood that Heron Tower is the first building in the UK to gain approval based on a multi-storey design fire.
Images: (above and opposite) The Heron Tower, ©Hufton+Crow
rather than attempting to identify underlying reasons why people exhibit these, further current research is also looking at improving our understanding of this.
WHERE WE ARE TODAY The Heron Tower in the City of London is an exemplar of modern fire engineering today. The building consists of 46 storeys above ground and three basement levels. The main floors are split into sets of three storeys called ‘villages’, each of these consisting of three floors with an open atrium. Design elements, such as these local atriums, made the application of standard guidance to the building insufficient, the solution being a full structural fire investigation.
34 Architects Choice July 2014
This aimed to determine a structural design and optimised fire protection strategy that would maintain stability and compartmentation during a reasonable fire worst-case scenario. The structural fire analysis used by Arup on this and other projects consisted of a four-step approach: 1. Develop a reasonable worst case design fire (one existing on multiple floors simultaneously)
2. Calculate the heat transfer from this fire within a representative structural model
3. Quantify the mechanical responses as a result
4. Propose mitigation measures or optimisation measures based on the quantified response
WHAT DOES THE FUTURE HOLD? If the last four decades have taught us one thing, it’s that fire safety is not only linked to building evolution but, by default, to social evolution also. Just as buildings respond to the popular mood in their scale and shape, so do the concerns of the fire engineering industry. If anything, this relationship will become more pronounced over the next decade as our shift into the digital age increases the speed of lifestyle changes. If fire engineers are to stay ahead of the curve, to keep innovating beyond reactive code compliance and conformance to regulation, they need to think about the impact that social changes will have on buildings and their occupants’ reaction to fire. What will be the effect of increasing popular concern with the environmental impact of buildings for example? Insulating buildings helps them retain their heat, reducing their energy demands but the best insulators also tend to be highly combustible. Fire engineers will need to work with architects to choose materials and create new forms of façade detailing, so that the buildings of the future are able to meet high energy standards, whilst performing well in a fire. We also need to consider the impact of an aging population. By 2050 nearly one in five people in developing countries will be over 60. Architects and engineers need to think about creating buildings to house people with reduced mobility,
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52