Fire Design Main Report

Individual Project: Fire Engineering Appraisal Of A Proposed Commercial Building

CE5604 Structural Design For Fire

LECTURER MARKING: DR ZHAOHUI HUANG

April 1, 2015

Authored by: Yama Habibi, 0916193

Fire Engineering Appraisal Of A Proposed Commercial Building: By Yama Habibi 0916193 Page 1

Content Page

Overview……………………………………………………………………………………………………………………………….. Page 2 Aim And Objective…………………………………………………………………………………………………………………. Page 2 Introduction………………………………………………………………………………………………………………………….. Page 2 Calculation……………………………………………………………………………………………………………………………. Page 3 Actions………………………………………………………………………………………………………………………………….. Page 3 Types Of Sprinkler For Design Appraisals One & Two ……………………………………………………………. Page 4 Design Appraisal One…………………………………………………………………………………………………………….. Page 4

Internal Beam Fire Design Calculation…………………………………………………………. Page 5 Edge Beam Fire Design Calculation………………………………………………………………. Page 11 Internal Column Design Calculation……………………………………………………………… Page 12 Edge Column Design Calculation………………………………………………………………….. Page 14

Design Appraisal One Review………………………………………………………………………………………………… Page 15 Design Appraisal Two…………………………………………………………………………………………………………… Page 18

Calculations: Composite Slab……………………………………………………………………….. Page 20 Calculations: Parallel Beams…………………………………………………………………………. Page 21 Calculations: Edge & Internal Primary Beam………………………………………………… Page 22 Calculations Column…………………………………………………………………………………….. Page 23

Design Appraisal Two Review………………………………………………………………………………………………… Page 24 Conclusion ……………………………………………………………………………………………………………………………. Page 28 Reference …………………………………………………………………………………………………………………………….. Page 29 Appendixes Page 30


Overview:

Project Name: Brunel Commercial Building

Location: Kingston Lane, Uxbridge, Middlesex UB8 3PH

Client: Brunel University, London

Aim and Objective:

To provide an appraisal of multiple structural fire engineering design approaches, to Brunel

Commercial Building: a steel frame building. The client is anxious to minimise construction

time, in order to start using the building as soon possible. This requirement has eliminated

concrete framing systems from consideration. The building needs to have fire resistance of

90 minutes with use of sprinklers system.

Introduction:

Fire represents one of the most severe environmental hazards to which buildings and built-

infrastructure are subjected, therefore fires account for significant personal, capital and production

loss in most countries of the world, each year. This makes the provision of appropriate measures

for protecting life and property are the prime objectives of fire safety design in buildings. These fire

safety objectives can be achieved through different strategies. During the design process, and in

the initial stages of a fire, the first aim is to confine the fire inside the compartment, so that it does

not spread to other parts of the building. However, if the fire becomes large despite of preventive

measures, the aim of the design is to ensure that the building remains structurally stable for a

period of time enough to evacuate the occupants and for the firefighters to contain the fire. It is the

job of the designer to ensure the effectiveness of the chosen measures in preventing the fires from

spreading and destroying the building (Purkiss, 1996).

The current fire protection strategy for a building often incorporates a combination of active and

passive fire protection measures. Active measures, such as fire alarm and detection systems or

sprinklers, require either human intervention or automatic activation. These measures help control

fire spread and its effect, as needed at the time of the fire. Passive fire protection measures are

built into the structural system by:

1. Choice of building materials

2. Dimensions of building components

3. Compartmentation, and

4. Fire protection materials

These measures control fire spread and its effect by providing sufficient fire resistance to prevent

loss of structural stability within a prescribed period, this time frame is, based on the building’s

occupancy and fire safety objectives. Materials and construction assemblies that provide fire


resistance, measured in terms of fire endurance time, are commonly referred to as fire resistance-

rated-construction or fire-resistive materials and construction in the two current model-building

codes: Eurocode 3 and 4 parts 2 and approved document B (Purkiss, 1996).

Calculation:

The calculation showed in this report follows temperature–time relationships, based on Eurocode 1 Part 2

approaches to model the thermal action produced by a fire on a structure. All structural members’ designs

are according to the standard curve (sometimes called the standard ISO 834 curve, given in prEN13501-2).

θg = 20 + 345log10(8t + 1)

This curve is used as a model for representing a fully developed fire in a compartment. In this equation,

θg is the gas temperature in the compartment or near the steel member in ◦C, and t is the time in minutes.

This standard fire curve is illustrated in this Figure 1:

Figure 1: temperature–time : Sources

Actions:

Variable load:

Imposed load: 3.5 KN/m2

Office partition = 1 KN/m2

Office finishing (ceiling and raised floor) = 0.7 KN/m2

Total variable load = 5.2 KN/m2

Permeant Load:

Dead loads were calculated, including the weight of all structural components (columns, main

beams, floor beams, and floor system), and cladding system.


Types of Sprinkler for Design Appraisals One & Two

Hazard classification

Buildings, and their contents are defined by a number of categories; or hazard classification. The Brunel Commercial Building is classed as Ordinary Hazard type 1 (OH1). According to approved document, B the use of a wet pipe sprinkler system is recommended for OH1 type buildings (Bafsa.org.uk, 2015).

Wet pipe

These are the most common automatic sprinkler systems. They are used in buildings where there

is no risk of freezing. Wet pipes are quick to react because water is always present in the pipes

above the sprinkler heads. Wet sprinkler systems are required for multi-storey or high-rise

buildings and essential for life safety. The main elements of a typical wet pipe installation are

shown in Figure 2 (Bafsa.org.uk, 2015) .

The sprinklers operate at predetermined temperatures to discharge water over the affected part of

the area below. The flow of water through the alarm valve initiates a fire alarm. The operating

temperature is generally selected to suit ambient temperature conditions (Bafsa.org.uk, 2015) .

Only sprinklers in the vicinity of the fire, i.e. those which become sufficiently heated, operate.

Design Appraisal One:

Precast Concrete Flooring System:

The advantages of precast a multiple. These include clear and faster erection time, superior

quality of result, and lifetime energy efficiencies from the thermal mass of the concrete. Non-

combustible precast concrete designs can better provide lasting and effective passive structural

fire protection. The following are benefits of precast concrete flooring system (Hanson Plc., 2015):

Figure 2


• It will never burn. • It isolates the fire.

• It requires no fire-resistance additives.

• It helps control sound and vibration.

• It does not produce toxins. • Its architectural design options are unlimited.

• It minimizes fire development. • It does not rot or support mold or termites.

• It absorbs heat. • It produces an economical system.

• It offers structural integrity. • It comes from a single-source provider.

The precast concrete chosen for Design Option One is A200 wide Hollow Core from Hanson PLC. Details are as follows (Hanson Plc., 2015):

200 mm depth and up to 1200mm width.

Support up to 7 KN/m2 of variable load.

Clear Span of 7.5m.

Self-weight of 3.42 KN/m2.

Uncropped construction is possible for spans up to 5.00m, for spans greater than these, temporary propping will enhance load/span characteristics.

Figure 3: Continuity over steelwork: (source: Hanson Plc.)

Structure Frame system for Design Option One:

Primary structures are those structural members essential to the overall integrity of the structure. These, structural members are of prime importance to the fire safety of the structure. Therefore, all primary structural frame members require fire-resistive protection. Therefore, selection of their steel grade is very important. These are includes

a) All the primary beams are S355 grade steel I-beam. b) All the internal columns are S335 grade steel Circular Hallow section. c) All the perimeter columns are S335 grade steel Universal column.

Secondary structures are structural members whose contribution to the integrity of the structure as a whole is not significant. Therefore, they do not require fire protection.

a) All the secondary Beams are S275 steel I-beam.


Beam Fire Design Calculation

Brunel University, London Subject : Internal Beam Fire Design Calculation Yama Habibi

Design code: EuroCode 3 Sheet no: 1

Unless stated otherwise all references are to BS EN 1993-1-2:2005. Refer to structural arrangeme-nt and loading BS EN 1990 NA.2.23.2 Table NA.2(B) BS EN 1990 Eq. (6.10a)

Simply supported Fully Restrained Beam

This calculation demonstrate the design of a fully restrained non-composite

beam grid line H1-H2, Appendix A.

Structural Layout and Action :

Characteristics Action:

a) Permanent action

o Assume Beam Self Weight = 1.0 kN/m2

o Precast Concrete Self Weight = 3.42 KN/m2

Total Permanent load = 1.0 + 3.42 = 4.42 kN/m2

b) Variable Action

o Imposed floor load for offices ( category B1 ) 3.5 kN/m2

o Office partition = 1 KN/m2

o Office finishing (ceiling and raised floor) = 0.7 KN/m2

Total variable load = 5.2 KN/m2

gk= 4.42 kN/m2 & qk = 5.2 kN/m

2

7.5m

Beam span = 7.5 m Bay width = 7.50 m

Ultimate limit state ( ULS ) design at Ambient Temperature

o Partial factor for permanent actions γG = 1.35

o Partial Factor for variable actions γQ = 1.5

Note for this beam calculation, the combination factor (ᴪ0) is not required as the

only variable action is the imposed floor load. The wind has no impact on the

design of this member.

Design valve of combined action = γG gk + γQ qk

= ( 1.35 x 4.42 ) + ( 1.5 x 5.2 ) = 13.78 kN/m2

UDL per meter length of beam accounting for bay width of 7.5m

Fd = 13.78 x 7.5 = 103.35 kN/m

gk = 4.42 KN/m

2 qk = 5.2 kN/m

2

ULS design Fd = 103.35 kN/m




6.1(1) NA 2.15 NA 2.4 BS10025-2 Table 7 Tata Steel Blue book

Design Moment and Shear Force:

Maximum design moment, My,Ed, occurs at mid-span, and for bending about the

major (y-y) axis is:

My,Ed = Fd x L2 / 8 = (103.35 x 7.5

2 )/ 8 = 727 kNm

Maximum design shear force, VEd, occurs at the end supports, and

is: VEd = Fd x L / 2 = (103.35 x 7.5 )/ 2 = 388 kNm

Partial Factors For Resistance

γmo = 1.0

Trial Section:

An advanced UK beam (UKB) S355 is to be used. Assuming no material is less than

40 mm thick the nominal valve of yield strength, fy should be taken to be 355 N/mm2

The required section needs to have a plastic modulus about the

major-axis (y-y) that is greater than:

WpL,y = (My,Ed x γmo ) / fy = (727x 103 x 1.0 ) / 355 = 2047 cm

3

From the tables of section

properties try section:

457x191x98 UKB, S355,

which has Wpl,y = 2232 cm3

Section 457 x 191 x 98 UKB

has the following

dimensions and

properties:

Modulus of elasticity E =

210000 N/mm2

Depth of cross-section H = 463.4 mm Width of cross-section b = 192.8 mm Depth between fillets d = 407.6 mm Web thickness tw = 11.4 mm Flange thickness tf = 19.6 mm Radius of root fillet r = 1.2 mm Cross-sectional area A = 125 cm

2

Second moment of area (y-y) Iy = 45730 cm4

Second moment of area (z-z) Iz = 243 cm4

Elastic section modulus (y-y) Wel,y = 1957 cm3

Plastic section modulus (y-y) Wpl,y = 2232 cm3

My,Ed = 727 kNm VEd = 388 kNm fy = 355 N/mm2

UKB 457x191x98




BS EN 1990 NA 2.2.6 BS EN 1993-1-1 NA2.23 UK NA to EN 1991-1-2 NA 2.7 to UK NA 1990 Table NA.A1.1

Classification of Cross-Section:

For section classification the coefficient ε is:

ε = (235/fu)0.5

= 0.814

Outstand flange: flange under uniform compression

cf / tf = 4.92

The limiting value for Class 1 is cf / tf ≤ 9 ε = 9x0.814 = 7.43

4.92< 7.43, therefore, the flange outstand in compression is Class 1.

Internal compression part: web under pure bending

cw / tw = 35.8

The limiting value for Class 1 is cw / tw ≤ 72 ε = 72x0.814 = 58.58

35.8< 58.58 therefore, the web in pure bending is Class 1.

Therefore the section is Class 1 under pure bending.

Moment Resistance: Plastic modulus, Wpl = 2232 cm

3

The design requirement is :

Mc,Rd = 792.4 kNm ( for Class 1 Section )

My,Ed / Mc,Rd = 727/792.4 = 0.92 < 1

Therefore, the design bending resistance of the section is adequate.

Shear Resistance: Applied shear, Vsd = 387.2 kN Shear area, Av = 5565.5 mm2 η.hw.tw= 4879.2 mm

2

Shear capacity, Vpl, Rd = 1140.7 kN [ > Vsd, OK ]

Serviceability Limit State (SLS)

The characteristic load combination at SLS is :

∑Gk+Qk

Vertical deflection of beam

The vertical deflection at the mid-span is determined as :

W = (5L4W) / (384EIy) = 0.6 mm

vertical deflection limit for this beam is

span/250 = 7500/250 = 30 mm

Therefore, the vertical deflection of the section is satisfactory

Design Loading in Fire:

Design moment at the fire limit state

Mfi,d = 𝜂fi.MEd

the reduction factor for design load level in the fire situation is given by :

𝜂fi = (Gk+ѱfiQk,1)/(ƴGGk+ƴQ,1Qk,1) ѱfi is to be taken as ѱ1.1 according to the UK NA to EN 1991-1-2. The valve of ѱ1.1 is taken from UK NA to EN 1990, for ( in this instance ), office area: ѱfi = ѱ1.1 = 0.5

𝜂fi = 0.510

Mfi,d = 370.2 kNm

The section is Class 1 Mc,Rd = 792.4 kNm Bending resistance is adequate Shear resistance is adequate vertical deflection is acceptable Mfi,d = 370.2 kNm




EN 1993-1-2 4.2.4 & 4.24(2) EN 1993-1-2 4.2.3.3 (7) & (8) Fire Excel software

Design Resistance Of Unprotected Beam In Fire : For simplicity, the resistance of a structural section may be verified in the temperature domain. Except when deformation criteria or when stability phenomena steel may be calculated as:

And µo = 𝑀𝑓𝑖,𝑑

𝑀𝑓𝑖,𝑡,𝑅𝑑

Design resistance at 20°C, using fire safety factors: For a Class 1 beam with uniform temperature distribution, Resistance moment at temperature θ is Mfi, θ,Rd = ky, θ (ƴM,1/ƴM,fi) MRd Strength reduction factor for 20°C: ky,20 = 1,0 ƴM,1 = [1,0] and ƴM,fi = [1,0] Resistance moment for strength at 20°C is MRd = 792.4 kNm Mfi,20,Rd = 1,0x([1,0] / [1,0])x 792.4 = 792.4 kNm

For a beam supporting a concrete slab on top flange:

Design moment resistance in fire = Mfi,t,Rd

= Mfi,θ,Rd

/k1k

2

Adaption factor, k1 = [0,7]

Adaption factor, k2 = 1,0

Mfi,t,Rd

= 792.4 /([0,7]x1,0) = 1131.9 kNm > Mfi,sd = 370.2 kNm OK

Degree of utilisation µ0 = 370.2 /1131.9 = 0.327

Critical temperature of beam θcr = 650.7 °C

Calculation of the unprotected steel temperature shows that the beam reaches its critical temperature of 650.7oC after 10 minutes. Because the critical temperature is reached at 10 minutes of fire resistance, an unprotected solution is unsatisfactory. Figure 4 shows the variation of the temperature of gas and steel temperature with time, showing when the critical temperature is reached:

Mfi,20,Rd = 792.4 kNm Unprotect beam θ

cr =

650.7 °C

Unprotected beam θcr

Figure 4: temperature of gas and unprotected steel temperature with time




EN 1993-1-2 4.2.3.3 (7) & (8)

Design Resistance Of Protected Beam In Fire: To protect the beam, then encasing with 15 sprayed protections and the manufacture provided the following data

Thickness, dp = 15 mm

Density, ρp = 430 kg/m3

Specific Heat, cp = 1200 J/kg°K

Thermal Conductivity, λp = 0.17 W/m°K

EN 1993-1-2 4.2.3 (7) and 8 recommend Adaption factor, k1 = [0,85] used for

protected beam, therefore M

fi,t,Rd = 990.5 kNm > Mfi,sd = 370.2 kNm OK

Degree of utilisation µ0 = = 0.374

Critical temperature of beam θcr = 630.4 °C

For 90 minutes, the steel temperature, θa = 673 °C

Figure 5 illustrates that the selected solution is satisfactory for a fire resistance period of 90 minutes, as the steel temperature is 673 °C, less than the critical temperature.

15mm thick spray Protected Beam @ 90 min the θa = 673 °C > θcr= 630.4 °C Adopt UKB 457x191x98 in S355 steel

Protected

Beam@ 90 min

θa = 673 °C >

θcr

= 630.4 °C

Figure 5 Standard curve of protected beam temperature with time


Brunel University, London Subject : Edge Beam Fire Design Calculation Yama Habibi


BS EN 1993-1-1 BS1993-1-2 Fire Excel

This calculation demonstrates the design of a fully restrained non-

composite edge beam grid line G-H, Appendix A.


gk= 4.42 kN/m2 & qk = 5.2 kN/m

2

7.5m

Beam span = 7.5 m Bay width = 3.75 m

Use Advance UKB 457x191x98 of steel grade S335

Classification of cross-section is Class 1 Moment Resistance, Deflection and Shear Resistance are

adequate at Ultimate Limit State Design at Ambient Temperature Design resistance of unprotected beam in fire:

Design moment in fire, Mfi,sd =185.1 kNm Design moment resistance in fire, Mfi,20,Rd = 1131.9 kNm > Mfi,sd OK Critical temperature, θcr =755.3 oC and edge beam reached the critical at 20 minutes; therefore, an unprotected solution is unsatisfactory as show in figure x. Design resistance of protected beam in fire:

To protect the beam, then encasing with 10mm sprayed protections and Figure 6 illustrates that the selected solution is satisfactory for a fire resistance period of 90 minutes, as the steel temperature is 740°C, less than the critical temperature 755.3°C.

gk= 4.42

kN/m2 qk =

5.2 kN/m2

Section is Class 1 Moment Resistance, Deflection and Shear Resistance are adequate Critical temperature, θcr =755.3 oC 10mm thick Spray Protection Protected Beam Temperature at 90 min = 740°C Adopt UKB 457x191x98 in S355 steel

Protected

Beam

Figure 6 : Standard fire curve for edge beam


Brunel University, London Subject : Internal Column Design Calculation Yama Habibi


BS EN 1993-1-12005 BS EN 1990 6.4.3.2 EN 1993-1-2 2.4.2.(2) Expression 2.5 EN 1993-1-2 2.4.3.2 EN 1993-1-2 4.2.5.1

Column in Simple Construction:

Internal column at ground level – Gridline H2, Appendix A

Column height = 5.00m

Advance UKC of 305x305x240 and steel grade of S335

Actions

a) Total factored permanent load from upper floors and roof ( includes beam

and column self-weight ) Gk= 1740.38 kN

b) Total factored variable load from upper floors and roof ( includes all finishing )

Qk = 1918.13

Ultimate Limit State Design at Ambient Temperature:

Overall cross-section is Class 1

Total design axial compression, Nsd = 6055.1 kN

Buckling resistance, Nb,Rd = 7044.62 kN [ > Nsd, (OK) ]

Design at Fire Situation:

Combination factor, Ψ1.1 = 0.5

Qk,1 / Gk = 1.2

Reduction factor, ηfi = 0.510

Design loading in fire, Nfi,sd= 3087.6 kN

Design resistance of unprotected column in fire :

Figure 7: Design resistance of unprotected column in fire

Critical temperature of column θ

cr = 654 °C

Calculation showed (figure7 ) that unprotect column fail and reach the critical

temperature at 44 minutes which less that required 90min fire protection and at

the Critical temperature less than fire load design therefore column must be

protect with fire protection materials.

Section is Class 1 Nsd = 6055.1 kN Nb,Rd = 7044.62 kN

654


Brunel University, London Subject : Column Design Calculation Group No1


P363

Design resistance of protected column in fire :

Protection material = British Gypsum Plaster Broad Thickness, dp = 10 mm Density, ρp = 800 kg/m3 Specific Heat, cp = 1700 J/kg°K Thermal Conductivity, λp = 0.20 W/m°K

Critical temperature of column θ

cr = 654 °C

Protected column temperature at 90 minutes is 605 oC less the critical temperature as showed in figure 8.

Figure 8: Standard fire curve for column.

654


Brunel University, London Subject : Edge Column Design Calculation Group No1


Edge column at ground level – Gridline H1, Appendix A

Column height = 5.00m

Advance UKC of 305x305x137 and steel grade of S335

Ultimate Limit State Design at Ambient Temperature

The Edge column fully stable at Ultimate Limit State and Overall cross-

section is Class 1

Total design axial compression, Nsd = 3054.6 kN

Buckling resistance, Nb,Rd = 3820.84 kN [ > Nsd, (OK) ]

Design loading in fire, Nfi,sd= 1557.6 kN < Nb,Rd OK

Critical temperature of Edge column θcr = 665 °C takes 34 minutes for the column to reach the critical temperature. Load at the critical temperature is 826.9kN less than fire design load. Therefore, corner column requires fire protection. Protection material = British Gypsum Plaster Broad Thickness, dp = 10 mm Density, ρp = 800 kg/m3 Specific Heat, cp = 1700 J/kg°K Thermal Conductivity, λp = 0.20 W/m°K Buckling resistance at critical temperature with uniform θa, Nb,fi,t,Rd =4042 kN [ > Nfi,d = 1557.56 kN, OK ]

Column steel temperature at 90 minutes in ISO fire curve reached to 610°C which is less than the critical temperature. Column size of UKC 305x305x137 with 10mm Gypsum board fulfiled the fire design requirement.

Class 1

Nsd = 3054.6

kN

Nb,Rd =

3820.84 kN

Nfi,sd= 1557.6

kN

θcr = 665 °C

10mm Gypsum Plaster Broad θa, Nb,fi,t,Rd

=4042kN @ 90 min = ϴ 610 Use UKC 305x305x137


Design Appraisal One Review:

The design plan of the structure provided (Appendix A) the structural bay size as 7.5m by

7.5m with a centre atrium of 30m by 15m. Hollowcore Precast floor systems were

selected. These provide a rapidly constructed solution to multi-story buildings, that is

economical, high quality, 2 hours fire-resistant (without need extra of fire protection

material), and has excellent deflection and vibration characteristics. Precast concrete do

not burn or give off lethal fumes in even the hottest of fires. It maintains its structural

integrity longer, giving occupants more time to evacuate safely and extinguish the fire.

Concrete and its mineral constituents enjoy the highest fire resistance classification (class

A1) under EN 13501-1. The precast slab thickness selected was 200 mm and provided a

clear span size of 7.5m unpropped, thus eliminating the use of secondary beams up to

7.5m of bay width. The precast concrete slab sat on top of the top flange of the steel

beam. Continuity was achieved by using a joint steel bar connecting the two slab cores at

a width of 1200mm and then infilling with concrete as illustrated in figure 3.

The building steel frame was designed as a braced frame. The beams were designed as

simply supported. The columns carried axial loads and (generally) minimal moments. The

beam to column connections were designed as nominally pinned, and hence did not

attract any moment; sufficient rotation capacity should be be provided. The cross braced

frame system was used to provide lateral stability to the building, as illustrated in figure 9.

The bracing system required 2 hours fire resistance, so it was important to maintain its

stability for duration longer than fire resistance of the substructure (which is 90 minutes for

beams and columns). This could be achieved by applying 15mm thick spray over all the

bracing members (Lennon, 2011).

All internal primaries beam were designed from advance universal steel of Hot-rolled I

sections, and strength grade of S355. The span of the beam was 7.5m and supporting

Figure 9: Example of bracing system


bay widths were 7.5m. the beam size UKB 457 x 191 x 98 from Tata steel was chosen.

Using a short span primary beam was primarily responsible for various advantages. This

includes eliminating the use of secondary beam, providing lower floor zone, short

defection, wide availability of hot rolled steel sections. As well as providing a strong rigid

moment frame, ideal for open plan office buildings.

Edge beams hot rolled I section, beam span was of 7.5m and the design was from S335

steel grade. The size of the beams was UKB 457x191x98.

All beams ( internal and edge ) beams were fire protect for 90 minutes by fire sprayed

protection material which could be applied on site after installation.

Fire protection layout, reducing fire protection to all primary members (beams and

columns) 90 minutes. Fire protection spray was applied directly to the contour of primed 'I'

and 'H' section columns and beams, and hollow sections, providing fire protection for up

to 120 minutes. In a fire, a chemical reaction takes place, causing the product to expand

and form an insulating layer, preventing the temperature of steel from rising to a critical

level.

The clear space between all columns was 7.5m. The internal column size was UKC

305x305x240 in steel grade of S335 and all the edge and Conner column size were UKC

305x305x137 steel grade of S335. The column height was 5m. All columns were fire

protected for 90 minutes by 10mm and 15 mm British gypsum plasterboard.

British gypsum board. is a fire protection system capable of providing up to 180 minutes

fire resistance to structural steel columns and beams. Its Installation was quick and easy

due to the use of simple clip fixings to secure the framing sections.

All services duct in the building were attached under the beams and fire protected for a 2 hour fire.

This was done by using encapsulated blanket product as the basis of a range of systems for up to

2 hour fire protection of ductwork. The blanket was simply attached to the duct using steel banding

straps as showed in figure 10. These are its key features (Franssen, Kodur and Zaharia, 2009) :

Non-combustible product.

Tested to meet ISO 6944, ASTM E2336, BS 476 part 24 and EN 1366-1 standards for fire

protection of ductwork

UL listed.

Flexible wrap - ideal for circular ducts minimising cutting and fixing .

Clean, quick and simple installation - encapsulated product.


Complete encapsulation resists contamination by leaking duct contents.

Zero clearance to combustibles.

Provides combined fire, acoustic and thermal insulation.

Figure 10: encapsulated blanket

Short span layout of the building governed by lower floor zone of 1.2m. Their dimension

illustrated in figure x:

Figure 11: floor zone of design one

1. Raised floor 2. Fan-coil unit 3. Ducting and

insulation 4. Lighting and

ceiling

100 mm

200 mm

463 mm 1.2 m

350mm

90 mm


Cost:

Size Unit cost Protection cost Total

Beam of 7.5m UKB 457x191x98 @ 98.3 Kg/m.

£1283 per ton = £958.43 per beam

£8 per m2 £1,026.06 per beam including protection £1026.06 x 102 (each floor ) x 8 ( whole building ) = £83648.96

Column of 5m UKC @ 282.9 kN

£1308 per tone £10 per m2 1414.05 ( each column ) * 60 *8 = £678744

Precast £50 per m square Total precast for entire building cost £900,000

Estimate total cost of the building steel and precast floor( excluding VAT) = £1,662,392

Approximation Construction Times:

Structural From Overall construction time (weeks)

Frame construction time (weeks)

Steel Beams & columns with precast concrete – hallow core units

44 9

Design Appraisal Two:

Floor system: for appraisal two, a

composite floor system has been chosen

and span of 4.5m Unpropped from Tata

Steel UK and type of slab is ComFlor®

100, V3. Composite floors consist of a

concrete topping cast onto metal decking.

Composite floor slabs use metal decking,

which spans between secondary steel

beams usually spaced at between 2.5 and

5m centres. Concrete, lightweight is then

poured onto the decking, usually by pumping, to make up the composite system. Lightweight

concrete is a better insulator and thus loses strength less rapidly in fire than normal weight

concrete. Hence lightweight concrete floors tend to be thinner than normal weight alternatives.

Metal decking acts both as permanent formwork for the concrete, eliminating the need to provide

props, and as tensile reinforcement for the slab. Steel bars are included in the slab to prevent

Figure 12 composite Slab: sources (Tata steel Europe, 2015).


cracking and to provide reinforcement in the event of degradation of the decking in a fire as shown

in figure x. Steel decking acts as a permanent shuttering which can eliminate the need for slab

reinforcement and propping of the construction while the concrete develops strength. This leads to

simple, rapid construction (Tata steel Europe, 2015).

Composite action reduces the overall depth of structure. It provides up to 2 hours fire

resistance without additional fire protection and 4 hours with added thickness or extra

surface protection.

Reduce the volume of concrete used, with resultant savings in structural and foundation

cost.

Composite slab system is fast, minimise temporary props, is structurally optimised and

save cladding costs. The system also reduces building height or enables extra floors to be

built.

Structural Frame: structure steel frame consist of parallel beams system and secondary beams,

which transfer the gravity load to steel column then to the foundation. All parallel steel beams are

grade of S335, and the secondary beams are grade of S275.

Load path: gravity load from the composite slab, were support by secondary beams ( ribs ) then its

transfer to parallel beams and from parallel beams all loads transfer to edge and corner columns.

This illustrated in figure


Design Appraisal Two Calculations:

Job Title:

SHEET 1 OF 1

CODE REF.

CALCULATIONS: COMPOSITE SLAB OUTPUT

BS EN

1194-1-2

Assumption: Analysis of composite slab for a fire resistance in parallel beams

system cannot possible to perform with beams as one frame (fire.xls 12.2

cannot use) so therefore composite slab analysis separately using fire.xls 11.

Type: ComFlor 100 V3

Span : 3.75m , Depth = 180 mm , Concrete C25 , Mesh A252 or Rebar 16mm ,

cover = 30mm

Load = Permanent gk = 2.56 KN/m2 , Variable qk = 5.2 KN/m2

The above calculation showed the Slab is adequate

UseFire.XLS 11

D= 180mm

gk =2.56 KN/m2

qk = 5.2 KN/m2


Job Title:

SHEET 1 OF 1

CODE REF.

CALCULATIONS: PARALLEL BEAMS OUTPUT

This calculation demonstrate the design of a fully restrained non-

composite parallel beams grid line H1-H3, Appendix B


gk= 4.42 kN/m2 & qk = 4.56 kN/m

2

15m

Beam span = 15 m, Bay width = 7.5 m

Use Advance UKB 2x (610x305x238) of steel grade S335

Classification of cross-section is Class 1

Moment Resistance, Deflection and Shear Resistance are adequate

at Ultimate Limit State Design at Ambient Temperature

Design resistance of unprotected beam in fire:

Design moment in fire, Mfi,sd =755.2 kNm

Design moment resistance in fire, Mfi,20,Rd = 3796 kNm > Mfi,sd OK

Critical temperature, θcr =725.8 oC and the beam reached the critical at

17 minutes; therefore an unprotected solution is unsatisfactory as show

in figure x.

Design resistance of protected beam in fire:

To protect the beam, then encasing with 10mm sprayed protections and

Figure x illustrates that the selected solution is satisfactory for a fire

resistances period of 90 minutes, as the steel temperature is 662°C, less

than the critical temperature 725.8°C.

Beam size of UKB 2x (610x305x238) with 10mm fire sprayed protection

fulfilment the fire design requirement for 90 minutes.

gk= 4.42 kN/m2

qk = 4.56kN/m2

L = 15m

section is Class

1

Design at

Ambient

Temperature

OK

θcr =725.8 oC

Use Two UKB

610x305x238 as

parallel beam

@ 90 mins

Protected Beam

θ = 725 oC

Figure 13


Job Title:

SHEET 1 OF 1

CODE REF.

CALCULATIONS: Edge & Internal Primary Beam OUTPUT

This calculation demonstrate the design of a fully restrained non-

composite parallel beams grid line G1-H2, Appendix B


gk= 4.42 kN/m2 & qk = 4.56 kN/m

2

7.5m

Beam span = 7 m, Bay width = 3.75 m

Use Advance UKB 457x191x98 of steel grade S335

Classification of cross-section is Class 1

Moment Resistance, Deflection and Shear Resistance are

adequate at Ultimate Limit State Design at Ambient

Temperature

Design resistance of unprotected beam in fire:

Design moment in fire, Mfi,sd =188.8 kNm

Design moment resistance in fire, Mfi,20,Rd = 1131.9 kNm > Mfi,sd OK

Critical temperature, θcr =752.3 oC and the beam reached the critical at 17 minutes; therefore an unprotected solution is unsatisfactory as show in figure Design resistance of protected beam in fire:

To protect the beam, then encasing with 10mm sprayed

protections and Figure x illustrates that the selected solution is

satisfactory for a fire resistances period of 90 minutes, as the steel

temperature is 675°C, less than the critical temperature 752.3°C.

Figure 14 :

Espouse UKB 457x191x98 as primary beams

UKB

457x191x98

Class 1

Design at

ULS all O.K

Use UKB

457x191x98

ϴa= 675 oC at 90

mins

Unprotect failure point


Job Title:

SHEET 1 OF 1

CODE REF.

CALCULATIONS Coloumn OUTPUT

Internal column( most heavy loaded ) at ground level – Gridline H3 . Appendix B Column height = 5.00m Advance UKC of 356x406x393 and steel grade of S335 Actions: a) Total factored load from upper floors and roof = 10602 kN Ultimate Limit State Design at Ambient Temperare Overall cross-section is Class 1 Total design axial compression, Nsd = 12172.3 kN Buckling resistance, Nb,Rd = 1313504 kN [ > Nsd, (OK) ] Design at fire situation Combination factor, Ψ1.1 = 0.5 Qk,1 / Gk = 1.1 Reduction factor, ηfi = 0.513 Design loading in fire, Nfi,sd= 6244.9 kN Critical temperature of corner column θcr = 603 °C and it’s take 47 minutes to column

to reached the critical temperature and load at the critical temperature is 5742.9 kN

less than fire design load, Nfi,sd . Therefore, column is required fire protection.

Protection material = 10mm British Gypsum Plaster Broad

Column steel temperature at 90 minutes in ISO fire curvy reached to 610°C which

less than critical temperature as illustrate in figure x:

Column size of UKC 356x406x393 with 10mm Gypsum board fulfilment the fire

design requirement.

Ned =

10602 kN

Design at

ULS & SLS

satisfactory

Nb,Rd > Nsd

& Ned OK

θcr = 603

°C

10mm

Plaster

Broad

Required

Buckling

resistance

θa, Nb,fi,t,Rd =

13090.4kN

in 90 min

fire

ϴa at 90min

= 533oC

UKC

356x406x3

93

Acceptable

UKC ϴa at

90min = 533oC


Design Appraisal Two review

There are a number of floor slab types that can be used in association to a steel frame for

a building. These slabs can be either continuous or simply supported and can be designed

to act compositely with the supporting beams if adequate shear connection is provided.

With use of Hollowcore precast flooring system for design one, design two consisted with

use of Composite floor system with 4.5m Unpropped from Tata Steel UK as its span and

ComFlor® 100, V3 as slab.

Composite flooring systems have been popular in use for multi storey buildings. Steel

decking in the composite construction acts as permanent shuttering, eliminating the need

for reinforcement while the concrete develops its strength. Composite flooring system were

considered lighter in weight than precast concrete floors, minimising time in overall

construction, also known as “rapid construction”. Composite actions can reduce the overall

depth of the structure while providing up to 2 hours of fire protection without any cover and

up to 4 hours of fire protection with added thickness or extra surface protection. The

overall weight of this system is low, particularly if the use of lightweight concrete is

considered. This reduces the overall cost of the project.

There are multiple benefits involved with in use of long span flooring system, the principal

benefit being additional free space. The use of long span floor eliminates the use of

columns, giving interior a larger space and the ease with which interiors can be changed,

giving building a longer life. There are also other secondary benefits involved; with long

span flooring system fewer pieces are to be used when compared to short span schemes.

This means fewer connections, and so fabrication and erection times are reduced. Longer

span beams also have favourable section factors making them more cost effective in

terms of fire protestation.

A complete design floor plan for Design two is provided in Appendix B. As seen from the

design, the elimination in use of columns provides the client with a larger free of space

increasing the life of the structure and ease of change for interior. The design encourages

in use of composite slab with span of 3.5m. For improvement in stability, columns are

added throughout the perimeter of the building and the atrium. Columns are also added in

the central section of the building for division of services provided.

This design also introduces the use of parallel beam system. Parallel beam system

consists the use of two main beams with the secondary beam running over the top main


beam. Both of these main beams are connected to either side of the column, helping in

reduction of construction depth and thus avoiding the use of beam-to-column connections

The parallel beams designed (UKB) are of section designation of UKB 610x305x238 fire

protected and promotes the use of steel grade S335 and edge beams are UKB 457x191x98

protected. Section designation for secondary beam are UKB 457x191x98 and unprotected.

Edge columns designed (UKC356x406x393) are for section designation of with steel grade

of S335.

This design also promotes the use of ComFlor® 100 slab with depth of 150mm, a very

strong profile shape offering the capability to span up to 4.5m, being able to carry wet

concrete and other construction loads without the need for temporary propping. Depending

on slabs, ComFlor ® 100 can provide a clear working space, minimising the hire of prop

and further savings of labour.

The services are located parallel to and in the same zone as rib (secondary ) beams, while

in the other way they are located parallel to and in the same zone as the spies. With this

arrangement, the structural depth is available for service runs, avoiding the situation of

services clashing. This is beneficial in terms of fire resistance as the services are now

within the part of secondary beams making them stable and avoiding extra layer of fire

protection, also reducing the cost. Figure 15 shows this in detail.

Figure 15: parallel grillage system showing service zones ( Source: SCI Publication 074)

Services Duct


The use of connections are covered via use of bolts and welds. It is considered that the

net-section failure at fastener holes need not be considered, providing that there is a

fastener in each hole, the steel temperature is usually lower at connectinos due to

presence of additional materials. The verification of this is based on the strength as

determined at room temperature multiplied by the reduction factor for strength of bolts and

welds given in table below.

Floor Zone:

100 mm

150 mm

1010 mm

100 mm

136

0 m

m

1. Raised floor

2. Ducting and insulation

3. Lighting and Ceiling


Estimate Construction Time:

Size Unit cost Protection cost Total

Beam span of 15m UKB 610x305x238 @ 238.1 Kg/m.

£1283 per ton = £4582 per beam

£8 per m2 £4772 per beam included protection £4772 x 102 (each floor ) x 8 (entire building ) = £114528

Edge Beam span of 7.5m UKB 457x191x98 @ 98.3 Kg/m.

£1283 per ton = £1892 per beam

£8 per m2 £1892 x 83 x 8 = £1256288 for entire building and protection cost only for edge beam = £135 per beam x 41 beam needed = £5535

Column of 5m height UKC 356x406x393 @ 393 kg

£1308 per tone £10 per m2 £2632 included the fire protection ( each column ) * 46 *8 = £968576

Composite Floor £75 per m square Total precast for whole building cost £1350000

Estimate total cost of the entire building steel and composite floor( excluding VAT) = £2,438639

Construction Times:

Structural From Overall construction time (weeks)

Frame construction time (weeks)

Parallel Beams & composite slab

63 9


Conclusion

With use of Eurocodes, British regulations and fire engineering programmes provided by Brunel University,

two designs were successfully calculated for as per client’s requirements. The design of company

headquarters for Prestige offices included client’s specification to have 1.5 hours of minimum fire

resistance, with sprinklers. Construction time, cost and fire resistance along with sustainability were the

biggest considerations for this project. Research conducted showed the variety in materials available

(ComFlor and precast flooring system) minimising in need for further calculations, especially precast

flooring system. The need to design this system for fire had been eliminated due to it being “precast”

where manufacture would provide the resistance in-built, thereby reducing cost and overall construction

time.

Both design shown in this project had its own advantages and disadvantages. With them both meeting the

set minimum standards of 90 mins of fire resistance below the critical temperature. This was checked on

the given spreadsheet and by hand calculations (calculations were conducted on critical members of the

design to study and demonstrate on how these would react under fire load). Design one on one hand had

the advantages of it making use of precast concrete manufactured off-site minimising overall construction

time to 44 weeks and its overall cost calculated to be £1.6 million. This type of design method is most

common for office construction.

Design two on the other hand made use of composite system involving the use of advance technology such

as ComFlor, minimising the use of columns and overall depth of the structure. This promoted the client in

use of 900 m2 of open area. The overall construction time and cost for this design is calculated to be 63

weeks and £2.4 million, respectively.

A detailed floor plan is provided in Appendix A and B for short span (design 1) and long span (design 2),

respectively. Use of active fire protection is recommended by building regulations and fire technicians for

further safety and a longer life expectancy of the building.


References:

Purkiss, J. (1996). Fire safety engineering design of structures. Oxford: Butterworth-

Heinemann.

Lennon, T. (2011). Structural fire engineering. London: ICE Publishing.

Hanson Plc., (2015). Hanson Building Product. Hollowcore Flooring. [online]

London: Hanson Plc,. Available at:

<http://www.hansonbuildingproducts.co.uk/plugins/downloads/files/Hollowcore_Floo

ring_Brochure.pdf> [Accessed 2 Apr. 2015].

Franssen, J., Kodur, V. and Zaharia, R. (2009). Designing steel structures for fire

safety. Boca Raton: CRC Press.

BS EN 1993-1-2: 2005: Eurocode 3: Design of steel structures. General rules.

Structural fire design. London: BSI, 2005

BS EN 1994-1-2: 2005: Eurocode 4: Design of composite steel and concrete

structures. General rules. Structural fire design. London: BSI, 2006

Bailey, C.G., Newman, G.M., and Simms, W.I. The design of steel framed buildings

without applied fire protection. Ascot: Steel Construction Institute, 1999 (SCI

Publication 186)

Lataille, J. (2003). Fire protection engineering in building design. Amsterdam:

Butterworth-Heinemann.

Jumppanen, U. and Paavola, J. (1987). Thermal behaviour of steel columns with

steel sheet-mineral wool fire protection. Espoo: Technical Research Centre of

Finland.

Dr Huang. Z (2015) Fire Engineering Design of Steel Members to EC3 Part 1-2,

from Structural Design for Fire. Brunel University, Available from Blackboard

[Accessed 15/04/2015].

Dr Huang. Z (2015) Fire Engineering Design of Steel Members to EC3 Part 1-2,

from Structural Design for Fire. Brunel University, Available from Blackboard

[Accessed 15/04/2015].

Dr Huang. Z (2015) Fire Engineering Design of Composite Members to EC4 Part 1-

2, from Structural Design for Fire. Brunel University, Available from Blackboard

[Accessed 15/04/2015].

http://www.hansonbuildingproducts.co.uk/plugins/downloads/files/Hollowcore_Flooring_Brochure.pdf

http://www.hansonbuildingproducts.co.uk/plugins/downloads/files/Hollowcore_Flooring_Brochure.pdf

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Fire Design Main Report