cse404 - week 2 guidance

8/9/2019 CSE404 - Week 2 Guidance

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The Hong Kong Polytechnic UniversityDepartment of Civil & Environmental Engineering

CSE404 Design Project Session 2014-2015

Week No. 2 – 20th January 2015 (Consultation)


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2

Q&A Summary of the Previous Lecture

1. Available space between basement footprint

& site boundary?

CSE404 Design Project – Week No. 2 – 20th January 2015 (Consultation)

2. Design Ground Water Table?

- Basement footprintat 1.5m from site

boundary

- Hoarding outsidesite boundary

permitted

- D.G.W.T at +3.5mPD (i.e. 1.5m below ground)

- Typical features of a site on reclaimed land

Basement

footprint

Site

Boundary


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3

Progress Report by Group Project Managers (Task E)

• Concise summary of team’s work within TWO slides for

presentation within THREE minutes• Submit by e-mail by Monday 12:00

• Late submission is NOT ENTERTAINED!!

• To be consolidated in lecture slides (for marking & record)

• Welcome drawings / sketches / diagrams.

• Avoid leeeeeeeeeengthy text.

• Starting next week (26th Jan submission for 27th Jan Workshop)



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Scheme Design Guidance

Superstructure


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BUILDING EXAMPLE

Design ‘Triangle’

ideas

scheme

Full design


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Lets take a quick look at a building

• Check stability

• Use span-depth ratios

• Estimate vertical forces

• Use N/A , M/Z

• Learn some ‘checking stresses’

• Use design aids – charts and tables


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Brief

• Hospital block

• 7.2 - 8m column grid

• ~Plan area 75m x 50m

• 5 storeys high


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Stability •Hospital block •8m column grid

•Plan area 70m x 50m

•5 storeys high• Core aspect ratio - 1:7 – 1:12

We may consider to provide movement joints at 70m spacing

Each side of movement joint needs a stability system


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Stability

MJ


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Loading?

Live Load? General usage 3.0kN/m2

Partitions 1.0kN/m2

Services & finishes 0.6kN/m2


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Floor system?

Suitable systems?

Depth?

Self weight?

RC flat slab

RC ribbed floor

Steel/concrete composite floor

Steel/precast composite floor

300 – 680mm

3.5 - 7.2


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Span/Depth Ratios

• RC flat slab 24

• RC ribbed slab 18

• Steel/concrete composite slab 18

•

Steel beams 15

• Precast slab (inc topping) 33


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So lets have a quick look at the columns

What are the loads?

Live load

Dead load + Superimposed

Dead Load

4.0kN/m2

17.0 kN/m2


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Load Take-Down

ELEMENT DEAD LIVE AREA DEAD LIVE

Roof 17 2 52 884 104General floor 17 4 52 884 208

General floor 17 4 52 884 208



4420 936

Approximate LOAD TAKE DOWN:


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Concrete Columns

‘Danish Method’

•

Factor axial force to take account of moments from the beams of the floorabove

• Internal columns: Factor 1

• Edge columns : Factor 1.25

• Corner columns : Factor 1.5

• So our basic internal column load is

1.4x4420 +1.6x936 = 7685kN ~ 8000kN

• Edge Column supports half the area, but has to take the effect of frame:

= 8000/2 x 1.25 = 5000kN

• Remember penultimate columns actually support 1.2 x typical internal columnload


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Learn ‘Checking Stresses’

• ‘Design Checking stresses’:

e.g. 23N/mm2 = Design checking stress for C45

concrete columns with 2%

• e.g.~ f cu/2 for f cu


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Scheming: Summary

•

We just had a quick look at scheming. The principles applyto other systems

• STABILITY

• PROPORTIONS

• ESTIMATE FORCES IN KEY ELEMENTS

• APPROXIMATE STRESS CHECKS

• DESIGN AIDS AND TABLES


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Span/Depth Ratios

• Steel beams 15-20

20-24

12-15

20-30

20-25

18-22

• Steel girders

• Space frames

• Composite

• Concrete floors

• Timber joisted floors

So knowing this can we estimate span:depth ratios for:

•Single span RC bridge?

•Continuous span, prestressed concrete bridge?

18:1

25:1

30 - 40• Post tensioned slab


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Foundation Design


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Foundation Design – Key Issues

• Loading

- Gravity- Water (Buoyancy, Flood)

- Wind

- Soil



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Foundation Design – Selection



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Foundation Design - Classifications



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Foundation Design – Common Pile types



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Foundation Design – Typical Pile Capacity



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Foundation Design – Basics


• Presumed end-bearing capacities / rock friction of bedrock

- Foundation CoP 2004, BD

• Strength of steel / concrete section

- Concrete CoP 2013, BD

- Steel CoP 2011, BD

• Individual Piles vs Pile Group (reduction factor for friction piles)- GEO Publication No. 1/2006

• Lateral Load Resistance

- Subgrade vs. raking piles

- Pile group vs. individual piles- GEO Publication No. 1/2006

• Testing Method (Dynamic test, proof loading test, proof drilling test)

- GEO Publication No. 1/2006


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Excavation and Lateral Support Design


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ELS Design – Design Consideration


• Technical Considerations

- Location / Ground Condition / Ground Water Condition- Development History --> Obstructions?

- Adjacent structures / utilities --> risks

- Ground movement criteria

• Other Considerations

- Constructability

- Time and Cost

- Flexibility for Basement / Superstructure Design

- Matching with foundation type


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ELS Design – Design Consideration



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ELS Design – Building / Ground Movement Control



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ELS Design – Common Wall Types


• Steel – Usually Temporary

- Channel Planking- Sheet Pile Wall

- Pipe Pile Wall

- Soldier Pile Wall

•

RC – may be permanent- Secant pile wall

- Bored pile wall

- Diaphragm wall

• Water cut-off

- Grout Curtain

- Temporary Wall

- Pumping Test


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ELS Design – Common Wall Types



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ELS Design – Systems


• Bottom-up construction

- Cantilevered wall- Braced (cross-lot shoring / raking struts)

- Tie-back

- Hoop action

• Top-down construction

- Permanent Slab

• Hybrid construction method

- Semi Top-down construction


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ELS Design – Top-Down / Semi Top-Down



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ELS Design – Difference in Approach



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Recommending a Scheme to the Client


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Scheme Design – Making a Recommendation


Distinct and Viable

Options!!!


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• Features / Flexibility Allowed

- Benefits to the Client

• Load Transfer Path

- Performance of product

• Ease of Construction

- Sophisticated temporary works?- Available working Space?

• Availability of Materials / Skilled Labour

• Cost & Time

• Associated Risk (and their resolution!!!)


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CSE404 D i P j t W k N 2 20th J 2015 (C lt ti )

Tools: A sketch is more powerful

than a thousand words

Tools: Traffic Lights

cse404 - week 2 guidance

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