Principles of Structural Design

This document covers various topics related to the principles of structural design, including safety regulations, factors of safety, deflection in beams, method of supports, and axial load carrying capacity. It also includes two design solutions for a concrete beam and a steel beam. The content is relevant for students studying civil engineering or related courses.

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Principles of Structural
Design
Table of Contents

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Task 1:.............................................................................................................................................2
Task 2:...........................................................................................................................................12
Task 3:...........................................................................................................................................15
Bibliography..................................................................................................................................17
Task 1:
(A)
(a)SF at A=75 KN
Change on SF from a to c1=0

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SFa to c1=75KN
SFa to c2=150-75= -75KN
Change to SF from c2 to B=0
SFB= -75 KN
Bending moment
Max=Area of diagram= =525 KN
(b)ℇRA=0
RBX8-65X2=0
RB=16.25KN

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RA=48.75KN
SF at A=48.75KN
SF at c1=48.75KN
SF at c2=48.75-65= -16.25KN
Change from c2 to B=0
SF at B= -16.25KN
Bending moment Max=Area of diagram= = 130KN
(c)
RA+RB=SXF

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RA+RB=625KN
RA= 312.5KN
RB=312.25 KN
SF at A=312.25KN
SF at B= -312.25 KN
BM=Area of diagram= = 1953.125 KN/m
(d)

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RA+RB= = 215KN
SF at A=215KN
RA= 215 KN
RB=215KN
Change in SF from A to c= 215-140=75KN
SFc2= -75KN
Change in SF from c2 to B= -15-140= -215 KN
BM=Area of diagram=75x7+ = 1015KN

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(e)
RA+RB= 625+50=675 KN
RA1=312 KN
RB1=312 KN
RBX20-15X50=7

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RA= 20KN
RB= 30 KN
RA+RB= 625+50=675 KN
RA1=312.5 KN
RB1=312.5 KN
RBX25-15X50=15
RA= 20KN
RB= 30 KN
RA=332.5 KN
RB=342.5 KN
SF from A to c1
332.5-25x15= -42.5 KN
SF from c1 to c2
-42.5-50= -92.5 KN
SF from c2 to B
-92.5-25X10= -342.5 KN
BMc1 == 2211.125
15-13.3= 1.7 m
= 36.12

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BMc2= 2211.125-36.12=2175
(B)
CDM2007 SAFETY REGULATION
Statutory requirements to ensure safety in structural designs
Safety in structural design is a key consideration to ensure when designing. All the
codes and regulations are designed to ensure safety regulations take a key point.
The major statutory requirement to ensure safety in designs are anchored on the
maintaining of the stability of the structure against either turning, sliding of
buckling. BS, Euro Code and code of conduct offers the key procedures of
ensuring safety measures are attained during design1. The statutory requirement
also requires the design to be able to meet the minimum strength to resist the safely
imposed stresses which are created by the loads. Lastly, the regulations also
require that the serviceability of the designed members is met. This ensures that
satisfactory performance is well achieved. The design of the stiffness and enough
reinforcement to contain the deflects and cracking is covered under this section.
(C)
BRITISH CODE
Explore, explain and produce valid factors of safety for live loads, dead loads and
imposed loads
Factors of safety are meant to ensure that the designs are able to meet the safety
factors. The British code is able to apply a factor of safety of 1.4 for the dead load
and 1.6 for both imposed and live loads. These factors ensure that the safety of the
1 Buchanan, Andrew Hamilton, and Anthony k Abu. Structural design for fire safety. (Chichester: John Wiley 2017).

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designs are covered well. The factor of safety is applied to get the design load for
the different cases.
EURO CODE
On the other hand, Euro Code also has different factors of safety for the different
loading cases. The Code has two different scenarios which can be used to provide
the design loads. Section 6.10 of the code applies 1.35 for the dead load and 1.5 for
the live and imposed loads. Additionally, section 6.10a and 6.10b uses factoring
factors of 1.35 for dead and 1.05 for live and imposed and 1.25 for dead and 1.50
for live and imposed loads respectively. The section giving the higher value is
usually adopted. This is because the higher factored loads will mean increased
safety. Most of the designers are able to prefer the use of section 6.10b
UDL=Mmax=wl2 /8
Point load Mmax=Wl/4
Ultimate load=1.4Xdl+1.6x IL
=1.4X5+1.6X5=15KN/m
UDL=w
Point load=W=1.6X30= 48KN
Mmax=wl2/8 + Wl/4=15x102/8 +48x10/4=307.5 KN/m
Plastic modules Sx >
M-max moment
Py- strength of steel
Grades of steel 275N/mm2 ;355N/mm2 ;460 N/mm2

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Sx > > 1.12x106 mm3
Sx > 1112 cm3
We choose 356x171x67
SX= 1210 cm3
Mc=PyxSx=275x1210x103=327 KN/m > 307.5 KN/m
Shear capacity
Pv=0.6xPyxtxD= 0.6x 275x 9.1x 3.64= 5.46x 103 N
t- thickness of the beam= 9.1
D- depth of the beam= 3.64
Pv =546KN > Actual SF
SF= = 99 KN in both ends
Pv= 546 KN 99 KN
(D)
M MAX DET THE STEEL SIZE
The bending moment of the beam is the first area which is used
during the design. First the selection of the lightest wide flange

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steel section is done. the shear and maximum bending moments
are then determined. The design bending moment should be
greater than the calculated maximum bending moment times the
factor of safety. This moment is usually a product of the applied
force times the Ix. The Ix is a major determinant of the beam
selection in any case. The bending moment also affect the
deflects which will be experienced. The shapes of the beam are
selected according to the deflection experienced. The shape of
the beam member should be able to resist the deflection from the
loading.
TASK 2:
(A)(a)
=Ỽ = = 5.81
Table 8 BS5950:
= 38.88
I-second moment of area
I= 914x 419x388=719000
E-module of elasticity =205 KN/mm2 for steel
(c)

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=Ỽ
Allowable: =69.44
=Ỽ =2.27
For 406x178x74
Ixx=27300
(d)
=Ỽ + = + =36.83
Allowable :
=Ỽ = 70
For 762x267x197
Ixx=246000
(B)
EXPLAIN DEFLECTION IN BEAM AFFECTS STRCURAL STABILITY

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Deflection is the measure of degree at which the beams displace when a load is
applied. Deflections in beams can occur to an angle or distance displacement.
When displacement occurs in beam, the fracture point is critical since it defines the
maximum structural stability of the beam member. Any deflection beyond the
fracture point causes failure of the beam. High deflections causes cracks on beam
members and therefore weakening the members2. This leads to structural failure of
the members especially when the reinforcements are exposed due to atmospheric
exposure. Also, when deflection on beam occur, the slab supported by the beam
also deflect. This may lead to structural instability to other members.
(C)
Method of supports of structures
Supports in the construction industry plays an important role in maintaining the
safety and ease of construction process, reduction of unnecessary costs and thus
increasing the economics, as well as enhancing safety and environmental factors.
Different methods have been applied when it comes of supports and each has its
own benefits as well as flaws. Scaffolding is one of the most effective support
method which has been used in construction3. This method is applicable in both the
reinforced concrete works as well as steel works as a support mechanism.
Assembling the scaffolds is easy and saves time. This brings about some key
economic benefits. Scaffolds can be reused over and over again and this helps to
increase the environmental friendliness of the mechanism. The scaffolds are strong
and this ensures that the safety standards are well maintained. In a construction of a
residential building, the scaffolds are used in the support of the slabs and also the
steel roof sections.
TASK 3:
(a)
Axial load carrying capacity: N=0.4x Fc x0.8x Fy
2 Hibbeler, Russell C. Structural Analysis in SI Units. (Harlow, United Kingdom: Pearson Education Limited 2019).
http://public.eblib.com/choice/PublicFullRecord.aspx?p=5755993.
3 Majid, Taksiah A., Choong Kok Keong, and Mustafasanie M. Yussof. Theory of Structures. (Pulau Pinang: Penerbit
USM 2012). http://public.eblib.com/choice/publicfullrecord.aspx?p=4306248.

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N=0.4 x Ac x fcu x 0.8 x fy x Asc
Ac= 350x 350= 122.500 mm2
Fcu- compressive strength of concrete
Fcu= 40N/mm2
Asc=2950 mm2
Fy= 460 N/mm2
N=0.4x fc x Ac+ 0.8 x fy x Asc
N= 0.4 x 40((350x 350)- Asc)+ 0.8x 460 x Asc
N=16(122500-2950)+ 368x 2950
N= 2998 KN
(b) (b)N= 2998 KN
Choose 203x203xuc 46
Le=3.75x0.8=3 m
λ= = =58.708
ry=5.11 cm=511mm
Pc=Agx Pc
58;60 -59—for steel 275 we have 224 and 221
We take 222.5=Pc

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Ag=58.8 cm2=5880 mm2
Pc=222.5x5880=1308300 N=1308 KN < 2998 KN
(A)
DESCRIBE CONCEPT OF SLENDERNESS
Slenderness ration is the tendency of a member of buckle when compressed. The
ration is usually the ratio between the effective length and the radius of gyration (λ
= kL/r)4. This formula applied for unbraced heights in both end conditions. The
effective length is the final length which is achieved after the members are
subjected to compression. It is defined as the distance between the contraflexure
points of a member. The end conditions and loading conditions play a critical role
of the effective length of the members. Different end conditions give different
lengths for equivalent half-sine wave. Effective length factors are applied
according to the different end conditions to find the effective length of the
members. The failure mode between the concrete structures and the steel structures
plays a critical role in the differences on the slenderness ration and the effective
lengths of the members5. In case the maximum deflection is more than the deflect
of the design loads, the section are deemed to fail. Another section is usually
selected.
(B)
Axial load carrying capacity
Pc=pc x Ag
Choose 305x 305x 198ͬ>
=8.02=802 mm
4 Smith, Paul. Structural design of buildings. (2016). http://public.eblib.com/choice/publicfullrecord.aspx?
p=4454999.
5 Mott, Robert L., and Joseph A. Untener. Applied strength of materials. (Boca Raton : CRC Press, Taylor & Francis
Group 2017)

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Ag=252
L=3.75
Le=0.7x 3.75= 2.625
λ= = = 32.73
Table 23 BS 5950 Table 24(c)
30-246
35-238
~242
Pc=242x 252x 102= 6098400 N=6098.4 KN> 2625 KN Ok
Task 4:
(A)
Develop 2 design solution)
Concrete beam
Taking a dimension of 200mmx 500mm
Self weight = 0.2*0.5*24 = 2.4KN/m
Loading = 55KN/m
total loading = 2.4 + 55 = 57.4KN/m
V = 57.4*8/2 = 229.6KN
Moment = 57.4*8*8/8 = 459.2 KNm
Reinforcement design

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D = 500-35-8-20/2 = 447mm
D’ = 35+8+20/2 = 53mm
K= M/bd*d*fck
= 130*106/ (200*447*447*30)
= 0.108 which is less than 0.167
z = d[ 0.5 + (0.25 –K/1.134) 1/2]
= 0.89 d = 0.89 x 447
= 398 mm
Area of tension steel
As = M/0.87fykz
= 130 x106/(0.87 x 500 x 398)
= 751 mm2
Provide 4T20
(B)
Produce drawing and specification

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(C)
Evaluate the use of alternative materials for construction
Different materials are able to provide different designs due to the self weight
loading. Lighter materials are economical in designs and provide less economic
designs. Nevertheless, the durability of the materials is a key factor which must be
considered during the design6. It is also good to consider the fractural strength of
the alternative material. In most cases, reinforced materials might be lighter and
with high structural strength. Use of composites is gaining a lot of popularity as
part of the alternative materials in construction7. These materials are designed to
provide specific design values such as enhanced structural strength. Additionally,
the materials are cheap and thus able to meet the economic factor.
6 Kamal, Mohammad Arif. Materials and technologies for green construction. (2015).
http://public.eblib.com/choice/publicfullrecord.aspx?p=1911024.
7 Froes, F. H. High Performance Metallic Materials for Cost-Sensitive Applications. (Wiley 2013).
http://public.eblib.com/choice/publicfullrecord.aspx?p=1656367.

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(D)
Building information modeling (BIM) is a new technology of process which helps
to support various tools in generation and management of digital presentations.
Different people have embraced the use of BMIs to plan, design, construction and
operating physical infrastructures8. The use of BIMs is much appreciated because it
is usually applicable even after the design and planning stages where it is applied
in the cost management, construction management, projects management and
operation of facilities. BMI is the production of the digital models and files which
enhance the construction. Production of 3D models has been achieved by
embracing the BMI. In addition, the technology has been able to in cooperate other
factors such as time to width, height and depth to produce 4D, 5D by addition cost
factor and also 6D by involving as-built operations. The different Ds of the models
is able to enhance the understanding of the drawings9. Coordination and
collaboration of different drawings has turned to be easy due to the use of BIMs. In
addition, drafting is much easier and this helps to produce high quality drawings at
minimal costs. In addition, when using BMI, it is easy to customize and flexible on
ideas of drawings. This helps to save time and cost for the projects.
8 Tardif, Michael. Building Information Modeling. (Wiley 2012)
http://www.123library.org/book_details/?id=52833 Accessed on 23/07/2019
9 Eastman, Charles M., Paul M. Teicholz, Rafael Sacks, and Ghang Lee. BIM
handbook: a guide to building information modeling for owners, managers,
designers, engineers and contractors. (2018).
http://search.ebscohost.com/login.aspx?
direct=true&scope=site&db=nlebk&db=nlabk&AN=1844137 Accessed on
23/07/2019.

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Bibliography
Arif, K, M. Materials and technologies for green construction. (2015).
http://public.eblib.com/choice/publicfullrecord.aspx?p=1911024.
Charles, E, M., Teicholz, P, M. Sacks, R. and Lee G. BIM handbook: a guide to
building information modeling for owners, managers, designers, engineers and
contractors. (2018). http://search.ebscohost.com/login.aspx?
direct=true&scope=site&db=nlebk&db=nlabk&AN=1844137 Accessed on
23/07/2019.
Froes, F. H. High Performance Metallic Materials for Cost-Sensitive Applications.
(Wiley 2013). http://public.eblib.com/choice/publicfullrecord.aspx?p=1656367.
Hamilton, B, A, and Anthony k Abu. Structural design for fire safety. (Chichester:
John Wiley 2017).
Michael T,. Building Information Modeling. (Wiley 2012)
http://www.123library.org/book_details/?id=52833 Accessed on 23/07/2019
Paul, S, Structural design of buildings. (2016).
http://public.eblib.com/choice/publicfullrecord.aspx?p=4454999.
Robert, M, L., and Untener J., A. Applied strength of materials. (Boca Raton :
Taksiah, M, A., Kok Keong. C., and Yussof M. M. Theory of Structures. (Pulau
Pinang: Penerbit USM 2012). http://public.eblib.com/choice/publicfullrecord.aspx?
p=4306248.CRC Press, Taylor & Francis Group 2017)
Russell, H, C. Structural Analysis in SI Units. (Harlow, United Kingdom: Pearson
Education Limited 2019). http://public.eblib.com/choice/PublicFullRecord.aspx?
p=5755993.