# cameroon gce A level 2022 building construction applied mechanics 3

### cameroon gce A level 2022 building construction applied mechanics 3

cameroon gce A level 2022 building construction applied mechanics 3

GRAND STAND PROJECT
The drawings on pages 4 and 5 represent a cross section and roof Plan View of the Grand Stand of a football field.
The roof covering is made of corrugated iron sheets resting on glued-laminatcd timber purlins. The main structure
(rafter) of the roof covering is made of glued laminated timber beams place 5.00m axis to axis. Each rafter is
centrally articulated on an 80 x 80 cm reinforced concrete pillar and is equilibrated by a steel cable AB which is
anchored in a reinforced concrete mass embedded into the bearing soil.
The concrete pillars are placed 5.00 m centre to centre.
Technical Information
Corrugated iron sheets
Laminated timber purlins
Laminated beams (rafter)
Exploitation of the roof.
Security coefficients for wooden elements:
300N/m2
,300N/ml
. 1 OOON/ml
400N/m2
1
1.2
PART ONE: STRENGTH OF MATERIALS. / 50marks
a) Study of a purlin
Assuming that each purlin is on 2 simple supports;
Calculate
9
i. The load per linear meter P of an intermediate purlin.
ii. The maximum bending moment (Mmai) in the span of the above purlin. P= l000N/ml
(5 marks)
(2.5 marks)
iii. The height of the cross section of a purlin if the width is 4 cm and the practical resistance of laminated
wood is 25N/mm2 and Mmas = 3500Nm . (5 marks)
b) Study of the equilibrium of an intermediate rafter beam
Assume that:
Each beam is straight, horizontal, articulated on a reinforced concrete pillar with cross section of 10 x \45
cm2;
The tie bar is articulated at its ends;
The load transmitted to the beam by the roofing sheets and the purlins is uniformly distributed;
Here below is the mechanical line diagram of the beam;