sif 2014 - structures in fire 2014 shangai
DESCRIPTION
OPTIMIZATION OF THE TALL BUILDINGS STRUCTURAL SYSTEM AGAINST PROGRESSIVE COLLAPSE. Vertical bracing systems and outriggers play a decisive role on the progressive collapse susceptibility. In relation to a steel tall building. Evaluation of structural performances of steel tall building is performed thought full non-linear analyses on finite element models. Performances of initial and optimized configuration are compared.TRANSCRIPT
Institute for Sustainability and OPTIMIZATION OF Institute for Sustainability and
Innovation in Structural Engineering
Filippo Gentili Franco Bontempi
OPTIMIZATION OF THE TALL BUILDINGS STRUCTURAL SYSTEM
AGAINST PROGRESSIVE [email protected] [email protected]
� INTRODUCTION
AGAINST PROGRESSIVE COLLAPSE
Vertical bracing systems and outriggers play a Fire Scenario 1
[email protected] [email protected]
Vertical bracing systems and outriggers play a decisive role on the progressive collapse susceptibility.
Scala A Ascensore
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Fire Scenario 1
Scala A Ascensore
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Scala A Ascensore
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In relation to a steel tall building (Figure 1). Evaluation of structural performances of steel tall building is performed thought full non-linear analyses on finite element models
Ascensore Scala A
Scala B
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160 m
Frame BAscensore Scala A
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35 mAscensore Scala A
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analyses on finite element models
Performances of initial (Figure 2) and optimized (Figure 3) configuration are compared.
Figure 1 – Case Study: Three-dimensional view and Fire Scenarios
Figure 2 – Initial Configuration:In blue vertical bracing systems
Figure 3 – Optimized Configuration:in red the added vertical bracing systems
in light blue the outrigger at 29th floor
Fire Scenario 2Frame A35 m
� OPTIMIZATION PROCEDURE
in light blue the outrigger at 29 floor
Heated Fire Steel Fire Several configurations (Figure 4) have been A1 A2 A3 A4 A5Heated Columns
Fire Resistance
No. Cases Avg Min Max
1 8 180 180 180
2 7 180 180 180
Conf.SteelMass[ton]
Fire Resistance
[min]
A1 799 75
A2 857 75
Several configurations (Figure 4) have beenassessed. The displacement on the top floor (1 meter) has been considered as indicator of theglobal colapse.
A1 A2 A3 A4 A5
2 7 180 180 180
3 6 143.6 80 180
4 5 88.4 78 103
5 4 67.5 66 69
A2 857 75
A3 877 180
A4 877 180
A5 877 180
The collapse can be avoided with outriggers (Table 1). The position has been varied in order to minimize lateral displacement. Table 1 – Mass and Fire Table 2 – Fire Resistance of to minimize lateral displacement.
Spatial extension of fire has been increased in the best configurations (Table 2).
Figure 4 – Sectional Configurations considered for Frame ATable 1 – Mass and Fire Resistance of Frame A
Table 2 – Fire Resistance of Frame A5 increasing fire extension
� FIRE STRUCTURAL PERFORMANCES ANALSYS
the best configurations (Table 2).
Three–dimensional spatial models have been48 49 50 51 52 53
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I
Time[min]
Collapsed Floor Area [m2]
Collapsed Floor Area Percentage [%]
Original Optimized Original Optimized
Three–dimensional spatial models have beenused.
An explicit dynamic solver allowed to trace
Scala A Ascensore
Ascensore Scala A
Scala B
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Scala A Ascensore
Ascensore Scala A
Scala B
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Scala A Ascensore
Ascensore Scala A
Scala B
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INITIA
[min]Original Optimized Original Optimized
60 130.26 0.00 11.21 0.00
75 208.71 76.71 17.97 6.60
90 325.21 76.71 28.01 6.60
An explicit dynamic solver allowed to trace down the propagation of failures.
Reduction in displacements of Initial and
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AL
OP120 350.21 230.31 30.16 19.83
150 No Con. 397.22 No Con. 34.21
Reduction in displacements of Initial andOptimized (Figure 5 top and bottomrespectively) Configuration is considerable.
Table 3 – Comparison of collapsed floor area between Original and Optimized Configuration for Fire Scenario 1
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Scala A Ascensore
Ascensore Scala A
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Scala A Ascensore
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PTMIZ
Also the portion of building, involved in thecollapse, changes substantially (Table 3).
Figure 5 – Displacement of the top floor over 1m of Initial (Figure 5 top) and Optimized (Figure 5 bottom) Configuration for Fire Scenario 1
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1 2 3 4 5 6 7
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Non-linear push-over analyses are conducted. A triangular lateral load has
(Figure 5 bottom) Configuration for Fire Scenario 1
(Eq. 1)
� ROBUSTNESS AND EFFICIENCY INDICES
(Eq. 3)conducted. A triangular lateral load has been applied at ambient temperature and after 30, 60 and 90 min fire exposure.
(Eq. 1)
(Eq. 2)
(Eq. 3)
(Eq. 4)
1.11
1.401.19
1.5
21.00
0.72 0.710.75
1A robustness index at ambient (Eq. 1) and elevated (Eq. 2) temperature,function of stiffness K, strength R and
1.06 1.11 1.19
0.5
1IE [-]0.50
0.12
0.270.25
0.5IR [-]
function of stiffness K, strength R and ductility μ is proposed (Figure 6).
A quantitative evaluation (Figure 7) of the performance improvement due to 0
No Fire 30 min 60 min 90 min
Fire Scenario 1
0.120.00
0No Fire 30 min 60 min 90 min
Initial Optimized
the performance improvement due to structural measures is achieved through the definition of an efficiency index (Eq. 3 and Eq. 4). Figure 7 – Evolution of Efficiency IndexFigure 6 – Evolution of Robustness Index3 and Eq. 4). Figure 7 – Evolution of Efficiency Index
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Figure 6 – Evolution of Robustness Index
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