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Title: Architectural and Structural Design of a Three Storey Building Office at Burera
District of Rwanda.
Authors: Evode MUNYANEZA BAGENZI and Naon BETABOLE
Corresponding author: Evode MUNYANEZA BAGENZI
Email: [email protected]
ABSTRACT
The main objective of this research was to craft out an Architectural and Structural Design of
a Three Storey Building Office at Burera District of Rwanda because of the inadequate
modern offices that exists in this district. This was a field experimental study design. This is a
creative process of turning abstract ideas into physical representations (products or systems).
The architectural drawings were produced and analyzed by using a pilot study using the
ArchiCAD software, Artlantis; structural design elements were designed basing on British
Standard B.S: 8110 and by using PROKON software. Findings were that a three storey
building of 51.80m *15.56m*12.45m with more than 50 adequate offices, two meeting
rooms, three staircases, one ramp and six wash rooms ready to accommodate all available
services has been architecturally designed while for structural design, the reinforcements in
different structures are as follow: slab short span at bottom Y10@150mm, slab short span at
top Y10@175mm, slab long span at bottom Y10@150mm,slab long span at top
Y10@150mm; internal beam bottom and top 3Y20, External beam bottom 3Y20 and top
3Y16; internal Column 4Y16; external column 4Y12; stair longitudinal Y8@100mm and
Transversal reinforcement Y10@150mm;ramp longitudinal Y14@150 and transversal
Y8@200mm and footing 8Y20@125mm; on the cost of one billion three hundred and fifty
two million eighty nine thousand seven hundred and thirty Rwandan francs
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(1,352,089,730Rwf).It is recommended that before constructing the district office,
geotechnical tests of the soil is required.
Keywords: Slab, Beam, Column, Footing, Stair and Ramp.
1. INTRODUCTION
In modern terms an office usually refers to the location where white-collar workers are
employed. An office is generally a room or other area where administrative work is done, but
may also denote a position within an organization with specific duties attached to it. An
office is an architectural and design phenomenon; whether it is a small office such as
a bench in the corner of a small business of extremely small size, through entire floors of
buildings, up to and including massive buildings dedicated entirely to one company
(Wikipedia, 2018).
The main purpose of an office environment is to support its occupants in performing their
job. Work spaces in an office are typically used for conventional office activities such as
reading, writing and computer work (Wikipedia, 2018).
Due to vision 2020, Rwanda is a developing country in Africa which has speed in growth
development. Rwanda is characterized by low but accelerating urbanization. This has
happened in a rapid and uncoordinated manner, meaning that social services and employment
opportunities are lagging behind. From now until 2010, each town will have regularly
updated urban master plans and specific land management plans. The country will develop
basic infrastructure in urban centers and in other development poles, enabling the
decongestion of agricultural zones (IBPUS, 2003).
BURERA district which is located in Northern Province consist of old buildings with
insufficient number of office required to accommodate all district staffs. In addition to this,
they work in a different buildings some of them are not designed for office (less than 30
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offices). That is why as a master student to be graduated from IST BURKINAFASO in Civil
Engineering, we come up with this proposal of designing ‘A Three Storey Office Building of
Burera District’ by providing enough and comfortable office to accommodate all staff safely
not only in nowadays but also in future with more than 50 adequate offices.
2. METHODS
2.1. Study design
This was as a pilot study design.
2.2 Architectural Drawings
Designing an architectural drawings of this building provided for Burera district office,
ArchiCAD software (version 18) is used to produce neat drawings namely structural plan,
floor plans, elevations, sections and roof plan. In addition to this, Artlantis studio version
(5.1) is used to produce adequate perspectives.
2.3 Structural Design Elements
2.3.1 Slab Design
The basic design procedure of a two-way slab system has five steps.
1. Determine moments at critical sections in each direction, normally the negative
moments at supports and positive moment near mid-span.
2. Distribute moments transverse at critical sections to column and middle-strip and if
beams are used in the column strip, distribute column strip moments between slab and
beam.
3. Determine the area of steel required in the slab at critical sections for column and
middle strips.
4. Select reinforcing bars for the slab and concentrate bars near the column, if necessary
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Slab design inputs are as follows:
h=depth of slab
d= effective depth of slab
α=modification factor
Lx= the length of short span
Ly= the length of long span
A) Classification of slab
Ly/Lx >2: One way slab
Ly/Lx ≤ 2: Two way slab
B) Span-effective depth ratio
𝐿𝑥
𝑑∗α=7 for cantilever slab
𝐿𝑥
𝑑∗α=20 for simply supported slab
𝐿𝑥
𝑑∗α=26 for continuous slab
The value of α are given in table 3.10 from BS 8110
C). Analysis of slab panel
Effective depth of the slab =𝑆𝑝𝑎𝑛(𝐿𝑥)
𝑏𝑎𝑠𝑖𝑐𝑠𝑝𝑎𝑛𝑑𝑒𝑝𝑡ℎ𝑟𝑎𝑡𝑖𝑜∗α
2.3.2 Beam Design
The design of beam for our building began by choosing the most loaded beams in the two
directions of the building. These will be subjected to the maximum moment and maximum
shear. These loadings will be calculated using various methods but for us we are going to use
the computer program.
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A) Continuous Beam Design
Continuous beams are a common element in cast-in-situ construction. A reinforced concrete
floor in a multi-storey building is shown in Fig.6 The floor action to support the loads is as
follows:
1. The one-way slab carried on the edge frame, intermediate T-beams and Centre
frame spans transversely across the building;
2. Intermediate T-beams on line AA span between the transverse end and interior
frames to support the floor slab;
3. Transverse end frames DD and interior frames EE span across the building and
carry loads from intermediate T-beams and longitudinal frames;
4. Longitudinal edge frames CC and interior frame BB support the floor slab.
Figure 1: Continuous beam layout, chapter 3.
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B) Loading on continuous beams
Arrangement of loads to give maximum moments
The loading is to be applied to the continuous beam to give the most adverse conditions at
any section along the beam. To achieve this, the following critical loading arrangements are
set out in BS8110: Part 1, clause 3.2.1.2.2 (Gk is the characteristic dead load and Qk is the
characteristic imposed load):
1. All spans are loaded with the maximum design ultimate load 1.4Gk+ 1.6Qk;
2. Alternate spans are loaded with the maximum design ultimate load 1.4Gk+1.6Qk
And all other spans are loaded with the minimum design ultimate load 1.0Gk.
a. Loading from one-way slabs
Continuous beams supporting slabs designed as spanning one way can be considered to be
uniformly loaded. The slab is assumed to consist of a serious of beams as shown in Fig.7.
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Figure 2: (a) floor plan; (b) beam AA, chapter 3.
b. Loading from two-way slabs
If the beam is designed as spanning two ways, the four edge beams assist in carrying the
loading. The load distribution normally assumed for analyses of the edge beams is shown in
Fig.0 where lines at 45° are drawn from the corners of the slab. This distribution gives
triangular and trapezoidal loads on the edge beams as shown in the figure.
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Figure 3: (a) floor plan; (b) load on beam AA; (c) load on beam BB, chapter 3.
2.3.3 Column Design
The columns in a structure carry the loads from the beams and slabs down to the foundations,
and therefore they are primarily compression members, although they may also have to resist
bending forces due to the continuity of the structure Fig.7
In the analysis, it was necessary to classify the column into one of the following types:
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1. A braced column: where the lateral loads are resisted by walls or some other form
of bracing, and
2. An unbraced column: where the lateral loads are resisted by the bending action of
the columns.
Figure 4: Critical load arrangement for column, chapter 3.
A). Design moments and axial loads on columns
Generally, design moments, axial loads and shear forces on columns are that obtained from
structural analysis. Design axial load may be obtained by the simple tributary area method
with beams considered to be simply supported on the column as represented on Fig.8.
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Figure 5: Diagrammatic illustration of determination of column design moments by
simplified sub-frame analysis, chapter 3.
B). Design for axial load and biaxial bending
The general section design of a column is accountant for the axial loads and biaxial bending
moments acting on the section. Nevertheless, the code has reduced biaxial bending into
uniaxial bending in design. The procedure for determination of the design moment, either
Mx’ or My’ bending about the major or minor axes is as follows:
Determine b’ and h’ as defined by the diagram. In case there are more than one rows of bars,
b’ and h’ can be considered of the group of bars Fig.9.
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Figure 6: column design details, chapter 3.
IF '' b
M
h
M YX USE YXX M
b
hMM
'
''
IF '' b
M
h
M YX USE XYY M
b
hMM
'
''
2.3.4 Design of foundation
The foundations are sub-structures located below the ground which transfer and spread the
load from a structure’s columns and walls into the ground.
For the serviceability limit state the total design load is nk=1.0Gk+1.0Qk
The required area of the footing will be Area required=𝒏𝒌
𝒔𝒐𝒊𝒍𝒃𝒆𝒂𝒓𝒊𝒏𝒈𝒑𝒓𝒆𝒔𝒔𝒖𝒓𝒆
The shear stress Vc at the column face
Vc=𝑵(𝒂𝒙𝒊𝒂𝒍𝒇𝒐𝒓𝒄𝒆𝒂𝒕𝒖𝒍𝒕𝒊𝒎𝒂𝒕𝒆𝒔𝒕𝒂𝒕𝒆)
(𝒄𝒐𝒍𝒖𝒎𝒏𝒑𝒆𝒓𝒊𝒎𝒆𝒕𝒆𝒓∗𝒅)
Critical perimeter=column perimeter+8*1.5d
Area within perimeter=(3d+CS)(3d+CS)
Punching shear force= V=earth pressure x( footing base surface - area within
perimeter)
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Punching shear stress 𝑽 =𝑽
𝒄𝒓𝒊𝒕𝒊𝒄𝒂𝒍𝒑𝒆𝒓𝒊𝒎𝒆𝒕𝒆𝒓∗𝒅
Figure 7: Critical section design for foundation, chapter 3.
Assumptions to be used in the design of pad footings are set out in clause 3.11.2 of the code:
1. When the base is axially loaded the load may be assumed to be uniformly
distributed. The actual pressure distribution depends on the soil type. Refer to soil
mechanics textbooks;
2. When the base is eccentrically loaded, the reactions may be assumed to vary
linearly across the base.
Refer to the axially loaded pad footing shown in Fig.11(b)where the following symbols are
used:
Gk characteristic dead loadfrom the column (kN)
Qk characteristic imposed load from the column (kN)
W weight of the base (kN)
lx, ly base length and breadth (m)
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pb safe bearing pressure (kN/m2
Figure 8: (a) mass concrete foundation; (b) Reinforced concrete foundation, chapter 3.
The area required is found from the characteristic loads including the weight of the
base: area=(Gk+Qk+W)/pb=lxly in m2
2.4 Cost Estimation
Construction professionals are involved in procuring building work on a daily basis. Effective
procurement aims to provide construction clients with projects which achieve good
value for money. Key objectives include ensuring that accurate budgets are prepared before
work commences and that the correct price is eventually paid for the completed work.
Measurement and valuation are essential processes underpinning these activities and together
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they form the central link between design and cost. On commercial projects these tasks are
usually carried out by quantity surveyors.
The quantity “takeoff” is an important part of the cost estimate. It must be as accurate as
possible and should be based on all available engineering and design data. Use of
appropriate automation tools is highly recommended. Accuracy and completeness are crit ical
factors in all cost estimates. An accurate and complete estimate establishes accountability
and credibility of the cost, therefore, providing greater confidence in the cost estimate.
2.4.1 1Introduction to Quantities Taking off
The quantification process involves recording dimensions and is referred to as taking off
because it involves reading or scaling (taking off) dimensions from a drawing and entering
this information in a standard manner on purpose ruled paper called dimension paper or
take off paper.
A). Quantity take off: Why?
Owner perspective:
Initial (preliminary) estimate of the project costs at the different stages of the project.
Preparing the BOQ as a requirement of the contract documents.
Estimating the work done for issuing the contractor payments.
Contractor perspective:
Pricing different work items;
Identifying the needed resources (Labor, Equipment, etc.);
Project schedule and
Preparing invoices for work done.
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2.4.2 Bill of Quantities
The term Bills of Quantities is defined as a list of items giving brief identifying descriptions
and estimated quantities of the works to be performed. The BOQ forms a part of the contract
documents, and is the basis of payment to the Contractor.
The BOQ also is defined as a list of brief descriptions and estimated quantities. The
quantities are defined as estimated because they are subject to admeasurement and are
not expected to be totally accurate due to the unknown factors which occur in civil
engineering work. The objective of preparing the Bill of Quantities is to assist estimators to
produce an accurate tender efficiently and to assist the post contract administration to
be carried out in an efficient and cost effective manner. It should be noted that the
quality of the drawings plays a major part in achieving these aims by enabling the taker-off
to produce an accurate bill and also by allowing the estimator to make sound
engineering judgments on methods of working. Table 4 shows a sample of a bill of
quantities.
A). Preparation of Bills of Quantities
Step1: The term squaring the dimensions refers to the calculation of the numbers, lengths,
areas or volumes and their entry in the third or squaring column on the dimension paper.
Step2: Abstracting is the process whereby the squared dimensions are transferred to an
abstract sheet or other similar computerized formats, where they are written in are cognized
order, ready for billing, under the appropriate section headings, and are subsequently reduced
to the recognized units of measurement in readiness for transfer to the bills.
Step3:Billing is the final stage in the bill preparation process in which the items and their
associated quantities are transferred from the abstract onto the standard billing sheets or other
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similar computerized formats that are in a format that enables the tenderer to price each item
and arrive at a total tender sum.
3. RESULTS and DISCUSSION
3.1 Structural Design
3.1.1 Slab Design
Using the biggest panel among others of 7.2*5.2m, the area of steel reinforcements provided
for Short span (bottom steel) is 524mm2/m, for Short span (top steel) is 449 mm2/m, for
Long span (bottom steel) is 449 mm2/m, for Long span (top steel) is 524 mm2/m, at support
Lx is 565 mm2/m, and at support Ly is 754 mm2/m. According BS Standard, the steel
reinforcements provided for Short span (bottom steel) is Y10@150mm, for Short span (top
steel) is Y10@175mm, for Long span (bottom steel) is Y10@175mm, Long span (top steel)
is Y10@150mm, at support Lx is Y12@200mm, and at support Ly is Y12@150mm.
3.1.2. Beam design
The beam is designed basing on the internal beam and the external beam.
For internal beam, the steel reinforcements provided for Span 1 are 2Y16 (Bottom) and 2Y16
(Top), for Span 2 are 3Y20 (Bottom) and 3Y20 (Top), for Span 3 are 2Y16 (Bottom) and
2Y16 (Top), for Span 4 are 3Y16 (Bottom) and 3Y20 (Top).
The Stirrups provided for Span 1 are R8@150mm, for Span 2 is R8@150mm, for Span 3
R8@150mm and for Span 4 is R8@150mm.
For external beam, the steel reinforcements provided are 3Y16 (Bottom) and 3Y20 (Top).
The Stirrups provided are R8@150mm.
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3.1.3 Column Design
The columns are designed based on the most loaded columns. The designed column cross
section size details are 400×300 mm for the internal column and 300×300 mm for the
external column.
The steel reinforcements provided for internal and external columns from foundation to
ground floor are 4Y16 with stirrups of Y8@150mm, from ground floor to1st floor are 4Y16
with stirrups of Y8@150mm, from 1st floor to 2nd floor are 4Y12 with stirrups of
Y8@150mm, and from 2nd floor to roof are 4Y12 with stirrups of Y8@150mm.
3.1.4 Stair Design
The designed Longitudinal steel reinforcements provided are Y12 with bar spacing of 100
mm and Transversal steel reinforcements provided are Y10 with bar spacing of 150 mm.
3.1.5 Ramp Design
The designed steel reinforcements provided at the top are Y14@200mm and at the bottom are
Y8@200mm.
3.1.6 Footing Design
The designed steel reinforcements provided for Interior and exterior footings are Tension
steel bars of 8T20 with bar spacing of 251.25 mm.
3.2 Cost Estimation
The total cost of building is estimated to be one billion three hundred and fifty-two million
eighty-nine thousands seven hundred and thirty Rwandan francs (1,352,089,730RwF).
3.3 Study limitation
Due to limitation of money, this study limited on the architectural design and structural
design of the district office with architectural drawings such as plans, elevations and sections;
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with additional design of the following elements namely: slab, beam, column, footing,
foundation, stair and ramp. This study did not cover on soil testing because it took the choices
which match with the means of life like a student with insufficient money (financial means).
4. CONCLUSION
The aim of this final year dissertation was to design modern district offices located in
BURERA to increase the good service provided to people and also a comfortable place for
BURERA’s staffs, councils and employees. The objectives were achieved through the
architectural and structural design of this office building. The architectural drawings were
produced and analyzed by using ArchiCAD software, Artlantis, structural design elements
were designed by using PROKON.
From the result, a three storey building of 51.80m *15.56m*12.45m with more than 50
adequate offices, two meeting rooms, three staircases, one ramp and six wash rooms ready to
accommodate all available services has been designed on the cost of one billion three
hundred and fifty two million eighty nine thousands seven hundred and thirty Rwandan
francs (1,352,089,730Rwf)
ACKNOWLEDGEMENT
Firstly, our great thanks go to the almighty God, for his mercy, guidance, and protection that
has been with us during the project. We would like to thank the administration of IST
BURKINAFASO that did every possible, to provide the technical skills needed to complete
this project.
LIST OF ABBREVIATIONS AND SYMBOLS
IST Institut Superieur De Technologies
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ICT Information And Communication Technology
Gk Dead Loads
Gk Imposed Loads
E Modulus Of Elasticity
BS British Standard
CAD Computer Aided Design
Kn Kilonewton
LSD Limit State Design
DL Dead Loads
LL Live Loads
m3 Cubic Meter
m2 Meter Squared
mm2 Millimeter Squared
m Meter
mm Millimeter
WL Wind Loads
W/C Water to Cement Ratio
H Depth of Slab
d Effective Depth of Slab
α Modification Factor
Lx Length of Short Span
Ly The Length of Long Span
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BOQ Bills of Quantities
As Area of Steel Reinforcement
Y Steel Reinforcement
AUTHORS’ CONTRIBUTIONS
EMB conceptualized the idea then EMB and NB drafted and approved the manuscript.
AUTHORS’ AFFILIATION
Institut Supérieur de Technologies, Department of Civil Engineering and Management
Ouagadougou, Burkina Faso.
FUNDING
The author (s) received no financial support for this work.
CONFLICT OF INTERETS
The authors declare no conflict of interest.
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