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CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Semester 2 Examinations 2011/
Module Title: Introduction to Structural Design
Module Code: CIVL
School: Building and Civil Engineering
Programme Title: Bachelor of Engineering in Civil Engineering – Year 2 Higher Certificate in Engineering in Civil Engineering – Year 2
Programme Code: CCIVL_7_Y CCIVE_6_Y
External Examiner(s): Ms. M. Kyne, Mr. J. Murphy Internal Examiner(s): Mr. T. McKenna
Instructions: Answer ALL questions from each section Use separate answer books for each section
Duration: 2 Hours
Sitting: Summer 2012
Requirements for this examination: Candidates may refer to
1. PP1990:2007 – ‘Structural Eurocodes’ Extract from Structural Eurocodes for students of structural design 2. ‘Approved Design Aids’ – (CIT Booklet)
Note to Candidates: Please check the Programme Title and the Module Title to ensure that you have received the correct examination paper. If in doubt please contact an Invigilator.
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Section A – Reinforced Concrete
QA. 1 Reinforced Concrete (50 marks) Details of the first floor slab, beam and column layout of a reinforced concrete structure are shown in Figure Q.A1. Design and prepare detailing sketches for the simply supported rectangular beam along gridline 3 in accordance with Eurocode 2. Beam dimensions are as follows: b=300mm; h=600mm. (a) Actions & Effects on Member (10 marks) Determine the Ultimate Limit State (ULS) shear force (VEd) and bending moment (MEd ) applied to the reinforced concrete beam. (b) Member Design (35 marks) Determine a suitable size and number of reinforcing bars to resist the maximum sagging bending moment at mid-span. Determine a suitable size and number of reinforcing bars to resist the hogging bending moment at the supports as required by EC2. Determine suitable size and spacing for the shear links to resist the design shear forces along the beam length. Verify the deflection of the beam. (c) Detailing Sketches (5 marks) Provide suitable sketches to illustrate the above design outcomes in preparation for detailed reinforcement drawing. Also complete the notes on the drawing. Use the attached General Arrangement drawing to complete the sketches and include with your Answer Book. Design Information: Actions on the Structure: Permanent Actions: Specific weight of reinforced concrete = 25 kN/m^3 Weight of suspended ceiling & services = 0.8 kN/m^2 Blockwork wall (2.8m height on all beams) = 5 kN/m^2 of wall area Variable Actions: Occupancy: Specific Use is ‘Self Contained Residential’ = 2.0 kN/m^2 Weight of removable partitions/fittings = 1.2 kN/m^2 Materials: Maximum aggregate size: dg = 20mm Grade of Concrete: C30/ Characteristic yield strength of steel reinforcement: fyk = 500 MPa Cover: Nominal Cover: cnom = 25 mm
Figure Q.A
ADDITIONAL INFORMATION FOR REINFORCED CONCRETE DESIGN
Design for Shear:
Maximum Compression Strut Resistance:
VRd,max =
αcw bw z ν 1 fcd Exp. 6. (Cot θ + Tan θ)
αCW is 1.0 for non-prestressed concrete bw = b for rectangular beam θ is the angle between the compressive strut and the beam axis; the angle of θ is limited in the national annex to 1 ≤ cot θ ≤ 2.5 (i.e. θ must be between 21.8° and 45°) fcd Design concrete compressive strength = fck/1. z lever arm as calculated, but for shear reinforcement the following may be used: z = 0.9d ν 1 is the strength reduction factor for concrete cracked in shear.
1 0.^61 ck
f
v
Minimum Shear Reinforcement:
yk f
bw fck s
Asw
- 08 sin
Note for vertical links: α = 90° (sin α = 1)
For rectangular beam: bw = b
Design Shear Reinforcement:
zf ywd cot
VEd s
Asw (^)
For shear: z = 0.9d fywd is the design strength of the shear reinforcement = fyk/1.
Resistance of Shear Reinforcement:
VRd, s cot
ywd
zf
s
Asw Exp.6.
Deflection Verification:
Basic allowable span to depth ratio:
Where a beam is singly reinforced Exp. 7.16a and Exp. 7.16b may be expressed as follows:
(^32) 11 1. 5 0 3. 2 0 1
d K fck^ fck
l if ρ ≤ ρ 0 (Exp 7.16a)
or
d K f^ ck
l
if ρ >ρ 0 (Exp 7.16b)
l/d = Basic allowable span to effective depth ratio K = factor to take into account different structural systems = 1.0 for simply supported beams ρ 0 = reference reinforcement ratio = (√fck)/ ρ = required tension reinforcement ratio = As,req/bd
Modification factor:
sprov
sreq s yk A A f ,
,
(^310) 500
SECTION B
QB. 1 Structural Steel (50 marks)
Figure Q. 3 shows the layout plan of the first floor of a building. A dancehall will be located on this floor. The floor construction will consist of a 75mm screed on 200mm deep precast concrete slabs spanning onto steel beams as indicated in Figure Q. 3.
Actions on the Structure: Permanent Actions: Allowance for self weight of beam & casing = 1kN/m Specific weight of reinforced concrete = 25 kN/m^3 Weight of Precast Concrete Slabs (200mm thick) = 298 kg/m^2 Weight of suspended ceiling & services = 25 kg/m^2
Variable Actions: Occupancy: Specific Use is ‘Dancehall’ = 5 kN/m^2
Task: It is proposed that Beam B 4 be a 406x178x67 UB section of Grade S275 steel. Verify adequacy of the proposed beam in accordance with Eurocode 3-1-1. Include verifications for section classification, shear, moment and deflection. Assume the beam is fully laterally restrained.
Figure Q.B
