International Journal of Scientific & Engineering Research, Volume 3, Issue 9, September-2012
ISSN 2229-5518
Excel Interface Utilization in Automation of Design Process of Ergonomic Classroom Furniture for Primary School Pupils in Nigeria
N.A. Adewole, B. Isedowo
Index Terms – Anthropometry, Ergonomic, Mismatch, Design, Furniture, Classroom, Automation
1.0 INTRODUCTION
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Evidences abound that developing countries of the
world were yet to be paying attention to offering ergonomically suitable chairs and desk to students for learning (Parcel et al, 1999; Haviarova et al, 2001; Joanne et al, 2007; Adewole and Olorunnisola, 2010; Ignacio et al,
2010). The use of non-functional and ergonomically unsuitable classroom furniture in Secondary School in Nigeria had been attested to by Adewole and Olorunnisola (2010). It appears Nigeria like many developing countries is yet to associate relevance to mitigating poor performance of school children through the use of ergonomic chairs and desks in their learning environment.
Recent report by the Nigerian Ministry of
Education shows that school children performance has dropped greatly particularly in science related subjects. Effective learning in classroom, especially science subjects required student concentration while learning. However, the use of ergonomically unsuitable furniture for learning will demand frequent adjustment of user’s posture at short interval of time. The frequent adjustment of learner’s posture while under learning will almost certainly affect the concentration to learning process. The consequence may be greater for primary pupils who are expected to be at the foundation stage of learning. It is for this reason that a study like this will help to drum more support for the use of ergonomic furniture in Nigerian classroom.
Adewole and Olorunnisola (2010) noted that
current method of classroom furniture production in Nigeria could be described as one size fit all. Although adjustable school chairs and desks would be efficient from an ergonomic viewpoint, in many African countries and particularly Nigeria, cost and material of construction are the limiting factors to adopting the use of adjustable approach in such furniture design. Another option would have been to have several sets of chairs cum desks from sizes from which school children are to choose the appropriate. The bane of this is the rigor of having to go through repeated design stages to evolve design templates for the several sizes that are expected to accommodate varying students’ anthropometry. However, the constraint of the latter option can be circumvented by automating the design process using collected data of the targeted students’ population.
There are inherent advantages in automating the
design processes viz enabling elimination of human error associated with manually repeated design processes, avoid material and time wastage. Also the body dimension of newly admitted set of students can be easily accommodated by program modification. Since wood is still largely used for the construction of classroom chairs and desks in Nigeria (Adewole and Olorunnisola (2010), creating opportunity for students to choose the appropriate
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International Journal of Scientific & Engineering Research, Volume 3, Issue 9, September-2012
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furniture remain the viable option of solving ergonomic problem of classroom furniture. Hence, the effort by this study to develop an automated design tool for eliminating
.
2.0 MATERIALS AND METHODS
The study was conducted in three phases: data collection and determination of mismatch; design of chair cum desk model manually using results of structural analysis and averages of anthropometric data mainly for structural rigidity, and; design process automation to enable flexibility of using varying anthropometry data to adjust sections of the chair cum desk for ergonomic reason. The study was conducted in the University of Ibadan Staff School and 72 pupils whose ages ranges from 5–12 years were randomly selected from primary one to six. A total of
12 pupils comprising of equal number of male and female
pupils were selected from each class. Information on the existing classroom furniture items currently offered to pupils in the schools was documented. Selected pupils anthropometry relating to the chair and desk dimensions (Chaffin and Anderson, 1991; Parcells et al., 1999; Ignacio et al, 2010) was collected alongside with the detail dimensions of the furniture used by the pupils for use in mismatch determination and furniture re-design. Mismatch in the pupils’ body anthropometry and furniture dimensions were established using rules recommended by Chaffin and Anderson (1991) and Parcells et al. (1999). The maximum load, forces and bending moment expected on the chair and desk sections were evaluated by modifying the procedures used by Adewole (2010) for similar classroom chairs and desks used by Secondary School Students also in Ibadan. The results of the structural parameters were combined with averages of the pupils’ anthropometry to evolve a
rigors involved in manual design will represent a significant contribution to mitigating ergonomic problem of classroom furniture in primary school in Nigeria
design template that were automated using IF Statement on Microsoft Excel. The variable parameters for the IF Statement are Hip-Width (HW), Popliteal-Height (PH), Buttocks-Popliteal-Length (BPL) and Shoulder-Height (SH). The IF Statements used for the Seat-Height (SH), Seat- Width (SW), Seat-Depth (SD), Desk-Height (DH) and Desk clearance are as follow:
Seat Height
=IF(B5=K2,30.3,IF(B5=K3,33.3,IF(B5=K4,36.1,IF(B5=K5,39,IF(
B5=K6,41.8,IF(B5=K7,44.7,IF(B5=K8,47.5,IF(B5=K9,50.4)))))))) Where: B5 is the PH range chosen while K2 – K9 are the
PH ranges available.
Seat Width
=IF(B3=H2,17,IF(B3=H3,20,IF(B3=H4,23,IF(B3=H5,26,IF(B3=
H6,29,IF(B3=H7,32,IF(B3=H8,35,IF(B3=H9,38))))))))
Where: B3 is the HW range chosen while H2 – H9 are the
HW ranges available.
Seat Depth
=IF(B6=J2,29.5,IF(B6=J3,32.3,IF(B6=J4,35.2,IF(B6=J5,38,IF(B6=
J6,40.9,IF(B6=J7,43.7,IF(B6=J8,46.55)))))))
Where: B6 is the BPL range chosen while J2 – J8 are the BPL
ranges available.
Desk Height =B9+13+2+7
Desk Clearance =B9+13+2 Where: B9 is SH
3.0 RESULTS AND DISCUSSION
3.1 Characteristics of Chairs and Desks in the
The University of Ibadan Staff School pupils are using wooden chairs and desks exclusively. This further confirmed the finding by Adewole and Olorunnisola (2010) that wooden furniture remains the dominant form of classroom chairs and desks used in Schools in Ibadan, Oyo State, Nigeria. The reason for the preference for wood in the construction of classroom furniture had been observed by Khanam et al (2006) to be due to students’ disposition to using wooden chairs and desk over other forms of chairs and desks. In accordance with the categorization by
Adewole and Olorunnisola (2010), the chair and desk design in use at this school are Single-user (SU) chair combined with Multiple-user (MU) desk (Plate 1). Although the ergonomic suitability of this classroom chair cum desk model is given more priority by this study, preliminary investigation of their functional performance indicated that these furniture items were prone to high rate of failure. The high rate of failure of chairs and desks may be traceable to jettisoning of engineering principle in their design, poor workmanship during construction, wrong usage and adoption of one-size-fit-all approach in their manufacturing processes (Haviarova et al, 2001; Adewole and Olorunnisola, 2010).
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findings agree with research by Parcells et al (1999), Lin and Kang (2005), indicating slight variations in the anthropometries of male and female, establishing the fact that sex is one of many parameters that influence human anthropometry. The variation was however insignificant as sex alone would not necessarily dictates the need for different chair and desk combinations in primary schools. Tables 2 summarized the measurement of wooden chairs and desk used by the pupils whose anthropometric were collected.
Table1 presents the summary of the anthropometry of the
pupils involved in the study. The summaries for the male pupils were presented first followed by female pupils result before summarizing for both male and female pupils. The female pupils appeared to be heavier than their male counterparts, with average body weight of 26.9Kg and
26Kg respectively. The average hip width of male pupils was 26.46cm compared to 27.76cm for the female pupils, while the average buttocks- popliteal length for male and female pupils was 37.08cm and 38.25cm respectively. These
BOYS N = 36 | |||||||||
Age (yrs) | BW(Kg) | SB(cm) | HW(cm) | SH(cm) | EHS(cm) | TT (cm) | BPL(cm) | PH (cm) | |
Average | 8.36 | 26.00 | 34.88 | 26.46 | 39.31 | 13.36 | 12.33 | 37.08 | 45.52 |
Maximum | 12.00 | 35.00 | 39.00 | 32.00 | 48.5 | 17.50 | 14.50 | 47.00 | 52.00 |
Minimum | 5.00 | 17.00 | 30.5 | 24.00 | 14.00 | 9.50 | 10.00 | 32.00 | 39.50 |
SD | 1.73 | 5.24 | 2.23 | 1.72 | 6.54 | 2.21 | 1.18 | 3.90 | 3.56 |
GIRLS N = 36 | |||||||||
Age (yrs) | BW(Kg) | SB(cm) | HW(cm) | SH(cm) | EHS(cm) | TT (cm) | BPL(cm) | PH (cm) | |
Average | 8.31 | 26.90 | 34.71 | 27.76 | 40.58 | 13.34 | 12.96 | 38.25 | 45.01 |
Maximum | 11.00 | 55.30 | 41.50 | 34.00 | 53.00 | 19.00 | 19.00 | 50.00 | 54.00 |
Minimum | 5.00 | 14.00 | 28.50 | 13.50 | 34.00 | 9.40 | 10.00 | 31.00 | 32.00 |
SD | 1.80 | 9.30 | 3.20 | 3.50 | 4.80 | 2.60 | 2.30 | 4.10 | 4.80 |
POOLED ANTHROPOMETRY FOR MALE AND FEMALE N = 72 | |||||||||
Age (yrs) | BW(Kg) | SB(cm) | HW(cm) | ShH(cm) | EHS(cm) | TT (cm) | BPL(cm) | PH (cm) | |
Average | 8.30 | 26.50 | 34.80 | 28.10 | 40.00 | 13.40 | 12.70 | 37.70 | 45.30 |
Maximum | 12.00 | 55.30 | 41.50 | 34.00 | 53.00 | 19.00 | 19.00 | 50.00 | 54.00 |
Minimum | 5,00 | 14.00 | 28.50 | 13.50 | 14.00 | 9.50 | 10.00 | 31.00 | 32.00 |
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S/N | Dimension (cm) | Average | Maximum | Minimum |
CHAIR FEATURES | ||||
1 | Seat Height | 42.30 | 47.00 | 36.50 |
2 | Seat Depth | 39.20 | 41.00 | 37.00 |
3 | Seat Width | 32.70 | 34.00 | 31.00 |
4 | Backrest Height | 41.20 | 49.00 | 35.00 |
5 | Chair leg Depth | 4.47 | 5.84 | 4.00 |
6 | Chair leg Breadth | 3.73 | 4.00 | 3.00 |
7 | Chair Side Rail Depth | 5.97 | 6.00 | 5.80 |
8 | Chair Side Rail Breadth | 2.20 | 2.20 | 2.20 |
DESK FEATURES | ||||
1 | Desk Height | 67.80 | 76.00 | 56.00 |
2 | Desk Clearance | 55.70 | 63.00 | 45.00 |
3 | Desk Leg Depth | 5.97 | 6.00 | 5.80 |
4 | Desk Leg Breadth | 3.00 | 3.00 | 3.00 |
JOINT: TENON FEATURES | ||||
1 | Depth | 1.67 | 2.00 | 1.60 |
2 | Breadth | 0.80 | 0.80 | 0.80 |
To establish possible mismatch between the students’ anthropometry and their furniture, the following rules from a related study by (Parcells et al., 1999; Chaffin and Anderson, 1991) was adopted.
when the seat depth is greater than 95% or less
than 80% of the popliteal length.
mismatch is established when the desk-kneel clearance is less than 2cm. There must be
minimum of 2cm difference between the kneel height and the distance from the base of the desk.
The seat height for the single user wooden chair surveyed for the pupils was 42.3cm while the corresponding 95th and
88th percentiles of the male popliteal height was 50.63cm and 49.4cm respectively, and 53.13cm and 50.9cm for the females respectively. Applying the rule in (1) above, it follows that the seat height is not fit for both males and female students. The seat depth of the existing chairs was discovered to be 39.2cm while the corresponding 95th and
80th percentiles of the male buttocks popliteal length was
44.13cm and 40cm respectively, and 44.13cm and 41cm for the females respectively. Adopting the rule in (2) above affirm that the seat depth of the existing chair is not fit for both gender in the school. These may be confirmed from the table below.
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Table 3. Mismatch Information on the SU chair Surveyed
Chair Anthropometry Sex Dimension Mean(cm) variable 95% 88% 80% REMARK | |
Male | Seat height 42.3 Popliteal Height 50.63 49.4 49 Not Fit Buttock Popliteal Seat depth 39.2 Length 44.13 41 40 Not Fit Seat height 42.3 Popliteal Height 53.13 50.9 48.5 Not Fit Buttock Popliteal Seat depth 39.2 Length 44.13 43 41 Not Fit |
Female | Seat height 42.3 Popliteal Height 50.63 49.4 49 Not Fit Buttock Popliteal Seat depth 39.2 Length 44.13 41 40 Not Fit Seat height 42.3 Popliteal Height 53.13 50.9 48.5 Not Fit Buttock Popliteal Seat depth 39.2 Length 44.13 43 41 Not Fit |
There is therefore a need to re-design the seat depth and
seat height of the SU chair to fit the users.
Here, maximum load, forces and bending moment expected on SU chair and MU desk as well as their legs was evaluated and used to re- design the chair seat chair legs, seat rail and joint as well as the joint, legs and rail of the MU desk to correct the earlier established mismatch and also to improve the furniture performance, details of which can be found in the appendix. Using the maximum parameters to design the chair:
Weight = 55.3Kg (553N); HW = 34cm (340mm); PH = 54cm (540mm); SH = 53cm (530mm); BPH = 50cm (500mm). The summary of the design result of the SU chair, MU desk and the joints is given below.
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S/N Existing Dimensions Re – Designed Dimensions |
Chair Sections |
1 Seat rail thickness = 22mm Seat rail thickness = 25.4mm 2 Seat rail depth = 60mm Seat rail depth = 94mm 3 Back Post thickness = 22mm Back Post thickness = 25.4mm 4 Back Post depth = 58mm Back Post depth = 58mm 5 Seat thickness = 15mm Seat thickness = 25mm Chair Tenon Sections 6 Thickness = 8mm Thickness = 10mm 7 Depth = 20mm Depth = 44.9mm 8 Length = 5mm Length = 15mm |
Desk and Its Tenon Sections Desk leg thickness = 30mm Desk leg thickness = 34mm Desk leg depth = 60mm Desk leg depth = 94.5mm Tenon depth = 20mm Tenon depth = 76.2mm Tenon width = 8mm Tenon width = 17.4mm |
The design process of an ergonomic chair and desk is rigorous and thus, the need to automate the design process to eliminate errors and design rigors involved in providing more than one design/size for students’ use is inevitable. Microsoft Excel interface was designed for this purpose, using insert function tool, IF statement tool and data validation tool. The interface include a drop down menu
for inserting independent design parameters i.e. body weight, hip width, sitting height, popliteal length and buttock – popliteal length which in turn generate a design output values i.e. seat height, seat width, seat depth, seat thickness, chair height, chair and desk structural components thickness and width as well as the desk height, desk leg clearance and tenor joints thickness and width. Fig
1.0 shows the appearance of the Microsoft Excel interface.
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International Journal of Scientific & Engineering Research, Volume 3, Issue 9, September-2012
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Fig 1.0 The Microsoft Excel interface
Table 6 below shows the SU chair and MU Desk design chart as produce with the Microsoft excel interface for the
use of the school furniture manufacturer. Different 8 design
and sizes are generated which can be use to accommodate different sizes of primary school pupils.
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Table 6. SU chair and MU Desk design chart
DESIGN INPUTS (ANTHROPOMETRY) | DESIGN OUTPUTS (FURNITURE DIMENSION) | |||||||||
BW Range 14 - 56 | HW Range 13 - 15 16 - 18 19 - 21 22 - 24 25 - 27 28 - 30 31 - 33 34 - 36 | SH Range 14 – 19 20 – 25 26 – 31 32 – 37 38 – 43 44 – 49 50 – 55 56 – 57 | BPL Range 31 – 33 34 – 36 37 – 39 40 – 42 43 – 45 46 – 48 49 – 51 | PH Range 32 - 34 35 - 37 38 - 40 41 - 43 44 - 46 47 - 49 50 - 52 53 - 53 | SH 30.3 33.3 36.1 39 41.8 44.7 47.5 50.4 | SW 17 20 23 26 29 32 35 38 | SD 29.5 32.3 35.2 38 40.9 43.7 46.6 46.6 | CH 47.3 56.3 65.1 74 82.8 91.7 100.5 106.4 | DH 52.3 55.3 58.1 61 63.8 66.7 69.5 72.4 | DC 45 48.3 51.1 54 56.8 59.7 62.5 65.4 |
Legend: HW Range = Hip Width Range (cm), SH = Seat Height (cm), SH Range = Sitting Height Range (cm), SW = Seat Width (cm), BPL Range = Buttock-Popliteal Length (cm), SD = Seat Depth (cm), PH Range = Popliteal Height (cm), CH = Chair Height (cm), BW Range = Body Weight Range (kg), DH = Desk Height (cm), DC = Desk Clearance (cm)
All other structural components dimension are the same for
the eight ranges of body sizes, as it was designed with the maximum weight of 56kg. Other design outputs generated by the excel interface which is the same for all the anthropometry categories are:
SU Chair Seat Rail: Thickness (w) = 25.4mm; Depth (d) =
94mm
SU Chair Back post /Legs :Thickness (w) = 25.4mm, Depth
(d) = 58mm
SU Chair Seat : Seat thickness (w) = 25mm
SU Chair Joint :Thickness (w) = 10mm; Depth (d) = 44.9mm
MU Desk Leg :Thickness (w) = 34mm; Depth (d) = 94.5mm
Desk Joint : Tenor depth = 76.2mm; Tenor width = 17.4mm
This study has been able to establish that Wooden Single – User (SU) Chair and Multiple- User (MU) Desk are exclusively in use in Staff School, University of Ibadan. There is a clear mismatch between students’ anthropometry and the furniture being offered to them in the Staff School, University of Ibadan, indicating that the existing furniture
in the school is ergonomically inadequate. The legs and
joints of the furniture in use by the students are poorly
designed which leads to frequent repair of legs and joints of the furniture
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International Journal of Scientific & Engineering Research, Volume 3, Issue 9, September-2012
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N.A Adewole is currently a lecturer in the Department of Agricultural and Environmental Engineering, University of Ibadan, Nigeria. He has B.Sc, M.Sc, Ph.D (Wood Products Engineeering). E-mail: an.adewole@mail.ui.edu.ng and dabukyo@yahoo.com
B. Isedowo graduated with B.Sc (Wood Products Engineering) from the
Department of Agricultural and Environmental Engineering, University of
Ibadan, Nigeria. E-mail: isedowo_tunde4u@yahoo.com@yahoo.com
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