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Buckling resistance combining bending and axial force
Cmy=¿ 0.6+ 0.4× (−0.5 )=0.4¿
CmLT=¿ 0.6+0.4 × (−0.5 )=0.4 ¿
k yy=Cmy (1+( λ y−0.2 )N Ed
x y NRk / γ M1)=0.424
k zy¿Cmy(1−0.1 λz
(CmLT−0.25)NEd
x z N Rk /γ M 1)=0.837
NEd
x y N Rk /γ M 1
+k yy
M y , Ed
X¿ M y , Rk /γ M 1
=0.383<1
NEd
x y N Rk /γ M 1
+k zy
M y , Ed
X¿ M y , Rk /γ M 1
=0.5<1
Therefore, buckling resistance in bending and axial compression satisfied.
3.4 Truss
Roof truss (Fink truss)
The truss to be designed is to support a roof which is only accessible for routine maintenance. The truss is 9m span with 24° pitch. The dimensions of the truss are shown in the figure below. The truss uses hollow sections for its tension chords,
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rafters and internal members. The truss is fully welded. Truss analysis is carried out by placing concentrated loads at the joints of the truss. All of the joints are assumed to be pinned in the analysis and therefore only axial forces are carried by members.
Figure3.2 Front elevation of fink roof
Characteristic actions
Permanent actions
Self-weight of roof construction 0.75kN/m2
Self-weight of services 0.15kN/m2
Total permanent actions 0.90kN/m2
Variable actions
Imposed roof actions 1.0kN/m2
Total imposed actions 1.0kN/m2
Ultimate Limit State (ULS)
Partial factor for permanent actions
Partial factor for variable actions
Reduction factor
Design value of combined actions
Design value of combined actions on purlins supported by truss
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For distance of 2.25m between purlins center to center
Thus all internal members will be selected as SHS, in S355 steel.
Serviceability Limit State (SLS)
Partial factor for permanent actions
Partial factor for variable actions
Design value of combined actions
Design value of combined actions on truss
Deflection:
The maximum allowable deflection is assumed to be span/300
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The maximum deflection of the truss is obtained for the SLS value of combined actions (i.e. Fd=37.4kN). The deflection at the apex was found to 13.8mm when all of the joints are assumed to be pinned. Deflection is therefore satisfactory.
4. Detailing
4.1 The connection for ASB to ASB
The connection for the ASB to ASB is determined depending on the British standard
and the end plate connection was recommended to be used.
The end plate may be taken as a standard width of 200mm for all ASB sections,
which allows connections to 203 UKC and larger columns. The vertical distance
between the bolts is 75mm for 3-bolt rows and it also recommended that for the span
<6m, the end plate thickness for moment resistant connections should be 12mm. The
table below also advertised to use M20 Grade 8.8 Bolt for the connection.
There are also some detailing rules for end plate connection to ASBS. The data is
shown as follow.
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Figure4.1 Recommended bolt sizes and plate thickness for ASB connection
CIV 6271 Design Project Group1
From the data provide from the slimdek manual, all the data for the ASBS
connection can be obtained as below.
Bolt: Grade 8.8 M20
Plate thickness: 12mm
The spacing of the bolts: 75mm
Dimension for B in the figure above
The moment resistant is 192KN.M
The web panel share force is 781KN.M
4.2 Beam to column connection
Med=211KN.m, Ved=106.5KN.m
Connection structural elements
Cantilever under balcony: UKB 457x191x82
Column: UKC 356x368x129
Design grade 43 M20 8.8 Bolts 200x20 END PLATE
A mini haunch 150mm deep will develop a moment of 351KN
Table3 Moment calculation
Row No Beam
side
Column
side
Minimum Lever
arm
Moment
capacity
Cumulative
moment
capacity
1 274 266 266 0.542 144.172
2 228 266 228 0.452 103.056 247.228
3 182 230 182 0.362 65.884 313.112
4 136 211 136 0.272 36.992 350.104
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Figure4.2 Detailing rules for end plate connections to ASBs
CIV 6271 Design Project Group1
Total 812 350.104
The moment capacity for 2 rows will suffice check compression.
Compressive force or column is 812KN for 4 rows bolts efficient is 812KN for 2
rows of bolts. Compressive force on column is 494KN, adequate, hence using 2 rows
bolts. Vertical shear check; Applied shear is 106.5KN.m
Bottom row dedicated to share provides 2x91.9=183.8KN
Each tension row connection resistance=331KN > 106.5KN.m Hence ok!
Web panel share check
The unstiffened web panel shear resistance is 605KN
The applied web panel shear by two rows of bolts is 494KN. Hence ok!
Wels to end check
The unstiffened web panel shear resistance is 605KN
The applied web panel shear by two rows bolts is 494KN
Wels to end plate.
Provide: Tension flange: 12Fw, Web 8Fw, Compression Flange: 8Fw
Haunch:
Angle of flange is taken of 60 degrees.
Fillet weld with a length equal to the flange thickness.
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4.3 Roof to column connection
Flexible end plate – Beam to UC column
Figure4.3 Front elevation of connection of bottom chord to UC column
Figure4.4 Plan view of connection of bottom chord to UC column
Design information:
Bolts: M16 8.8
End Plates: 200x90x10
Welds: 6mm fillet
Material: All S355 steel
Tie force=126kN< 215kN
The beam side of the connection is adequate.23
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4.4 Column to foundation connection
Column to foundation connection
Connected structural elements Figure4.5 Actions on column footing
Column level1 UKC 366x368x202 taken from dead loading
Primary sizing:
650x450x50 base plate with four M24, Class 8.8 bolts each side.
The foundation is to be in C30 concrete.
Check whether there is no tension in the bolts.
Distance to edge of compressive stress block.
Compression , OK.
And there is no tension in the bolts.
and .
T shape stress block
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Required design stress
586kN, 157kN﹒m combine.
Check whether there is no tension in the bolts.
Distance to edge of compressive stresses block
Compression
No tension in bolts.
Base plate thickness
The required plate thickness is the larger value resulting from (a) or (b) below:
(a) Compression side bending
(b) Tension side bending
where T=0, hence
Therefore,
Use 45mm plate.
Holding down bolts and anchorage
Use two M24, Class 8.8 bolts, but no tension in the bolts. (Bolt spacing=300mm)
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The overall embedment depth in the concrete (Excluding the grout beneath the base
plate) is 450mm (min requirement)
Shear Transfer to concrete
Check if the horizontal shear is transferred by friction.
Available shear resistance , OK.
Welds: 10mm fillet weld both sides of the web.
5. FoundationThe site is located at the city centre and the site condition is shown as below
Table4 Site conditions
Description Depths Soil data
Sand and Clay Ground level - 16.0 m C = 40 kN/m2
Rock Below 16.0 m Allowable bearing
pressure =
2500 kN/m2
The max load which transferred for the column to the foundation is 2400KN for the
corner column of the building and if the pile designed as friction pile the allowable
pile bearing load is not enough to bearing the column load. In terms of this situation,
the end bearing pile with a diameter of 600mm and depth of 16m should be used
under this building. In this case, allowable pile bearing load is 2600KN, so it
designed as single pile for each column is enough to carry the load from upper
structure. Addition to that, the building is constructed nearby an existing highway
and over an existing 5.0m wide x 2.0m deep canal. So during the construction of the
foundation, the 1.0m thick impermeable clay lining must not be damaged during
construction of the foundation and this process also should not influence use of the
existing highway. In consideration of that, bored and cast-in-place pile can be used in
this case in order to minimise the impact to nearby cannel and highway. Besides
that, the pile which located along the canal should be eccentric and make sure there
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no adverse effect on the waterproof layer during the building’s construction and
using.
The figure above demonstrated the main construction process of the cast-in-place
pile. It is clear that during the construction process, the pile hole is achieved by
drilling in to the soil rather than hammering into the soil, therefore it makes little
vibration and compaction effect during the construction process and protect the
waterproof layer and highway from damaging.
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Figure5.1 Construction process of cast-in-place pile
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6. Method statement
Generally, it will take 80 to 100 days from the beginning of excavate and construct
of the foundation to the end of the clear site. The typical progress schedule (in days)
is shown as above. After the construction of the foundation finished, several works
would be undertook in parallel and significant on-site time could be saved. Besides
that, by manufacturing the frame in the factory can also reduce the risk of delay
caused by bad weather or insufficient or inadequate construction resources in the
locality of the site.
6.1 Slimdek
Some typical for the installation method of the decking should be noticed and the
graph below shows that the connection of the decking and the ASBS.
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Figure6.1 The progress schedule of the construction work
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The diaphragms are fixed to the edges of the lower flanges of the beams on both
sides (except for edge beam situations) using two fixings at pre-marked positions for
each length. The 1800 length equates to three sections of ComFlor 225 decking. Each
length should be positioned and abutted accurately so that the 600mm pitch of
decking sections is located as shown on the layout drawings.
After the decking is placed, props should be positioned and it also should not be
removed until the concrete has achieved 75% of its specified strength (normally 7
days).
A temporary bridge should be built on the cannel during the construction in order to
make the construction work convenience and easy to convey materials across the
canal.
6.2 Method for the safety during the construction
1. A protection shutter should be laying 1m away aside the cannel to protect the
canal and the waterproof layer from damaging during the construction process.
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Figure6.2 fixing of end diaphragms at ASB
Figure6.3 Propping during the construction
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2. Protection net also should be provided along the edge of each floor to minimise
the risk of the falling materials from the upper floors.
3. Scaffold cannot be removed until the construction process all completed and it
should also provide enough stability for works to stand and walk. The construction
workers should educated about the adequate construction method before they start
their work and some safety criterion should be observed by the worker and engineer.
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7. Letter to ClientDear Customer,
Having considered experimental equipment will be accommodated in the laboratories
of the building, in the initial stage of slab design, the structure is designed to has high
frequency floors (freq.≥10 Hz). (in accordance with Appendix G of Vibration
serviceability of post-tensioned concrete floors provided by University of Sheffield)
Generally speaking, equipment could be installed in the laboratories and it is
suggested to set this equipment in the area near lift shaft core which has a relative
high stiffness which means the effects of vibration could be minimised. Also, lateral
embrace of the whole structure is provided by the lift shaft core.
Further vibration investigation could be carried out by using finite element method
and modal shape of the slab is expected to be analysed. For each nodal points of n th
mode, the equipments are advised to be set on as the deflection and acceleration
would be the minimum, which indicates the impacts on equipments are relative
smaller. Normally, the critical nodal point of 1st mode of the slab is on the midpoint
of span.
Sincerely yours,
Group 1
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Reference
BCSA SCI. (2009). Joints in Steel Construction - Simple Connections.