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Integrated Civil EngineeringDesign Project

(Building Structure Design)

CIVL 395

HKUST

By : Ir. K.S. Kwan

Date: 3/07



Content

1. Building Control in Hong Kong

2. Design Criteria

3. Structural Form (Residential Building)

4. Hong Kong Wind Loading

5. Computer Modeling6. Design Example



BUILDING CONTROL

IN HONG KONG



1. Building Control in Hong Kong

Building Department (BD) – to control the building development in

private sectors. All development plans should be submitted to BD forapproval and seek consent for construction. BD will approval/reject theplans based on the statuary requirements such as development area,building height, strength and stability of building etc…

Under Building (Construction) Regulation), the following plans should besubmitted by Authorised Person (AP), Registered Structural Engineer(RSE) or Registered Geotechnical Engineer (RGE).

Building Plan (architectural design on site and building layout) Structural Plan (structural framing and detail)

Foundation Plan (foundation design of building e.g. piling layout)

Site Formation Plan (civil and geotechnical engineering work)

Demolition Plan (structural engineering work)



Site Layout PlanTo show the major

development of the site e.g.

site location, relationship

with surrounding buildings,

slopes , no of blocks,

external works , etc.

In particular to the site

closed to some scheduled

area such as Marble Area,

MTRC…, The development

should make provision on

the design such as reduced

stress in foundation design

in Marble Area and no

foundation work within 3m

from the MTRC structure



Building Floor Plan (Architectural Plan)

Part plan at 37F- 40/F`

Flat roof

at 37F

It is prepared by the AP to show

the block layout including

development area, height of

building, building shape, floor

plans, lift location, fire escape

route, prescribe window…

Other than the tower typical

floor plan, the layout of podium,car park, roof, water tank, pump

room, transformer room et. are

included.

Based on this plan, the RSEshould prepare corresponding

structural layout including the

structural details to BD for

approval.



Structural Framing Plan This is the skeleton of building.

All members shown on this plans

are called structural elements. Any change/removal should be

verified by RSE.

The drawing should

show all membersizes (i.e. wall,

column, slab and

beam), concrete

grade and any special

issue such as transferor cantilever structure

The contractor can

use this drawing for

formwork construction



Structural detail drawing To show the

reinforcement detail for

construction All bar length, size,

spacing should be shown

The contractor can use

this drawing for steelfixing

Slab reinforcement

detail



Foundation PlanTo show all the foundation

layout including footing,

pilecap and piles.

Pile layout

Pilecap

layout



Building Design Standard

Building (Construction) Regulation (The law used to control buildingdevelopment including the precedure to submit building plan, material used for construction,foundation requirement at building design…)

Local Code of Practice – Wind, Concrete, Steel, Fire (They

provide most technical standard for designer. A new set of CoP have been issued between 2004and 2005. The coming CoP will include “Loading” and seismic design…. Wind CoP is speciallyspecified for local wind climate. Concrete CoP is similar to BS8110 other than the materialproperties. Steel CoP is similar to BS5950))

Practice Note for Authority Person/Register Structural

Engineer (PNAP) (up to 301 notes to provide some requirements on design and

construction other than above two such the identification of scheduled area, use of code ofpractice etc..)



PNAP



Structural Engineer

Structural engineer is to develop theskeletal framework and the foundationand other soil/structural interfacing works

for bridges, buildings and other structuralforms, which are to withstand against the

natural forces due to gravitational wind,

soil, water, earthquake and/or other

environmental effects.



Factors to be consideredfor Building Development

Buildability(Easy for construction,

Safety….)

Quality(material control,Workmanship….)

Environmental(Energy saving, formwork

Saving, ….)

Cost-effective(To reduce the

construction cost whichIs about HK$4,000

to 8,000/m2)

Functional(Residential, commercial,

factory, school…)



Building Development ProcessFeasibili ty Design

Preliminary Design

(Scheme Design)

Detailed Design Stage

Construction Stage

To test the development by different design

parameters (population, number of flat, no. of

blocks, location etc. ) for development cost

estimation. In some case, the foundation is

extremely high and it is a factor to be considered

when disposition of blocks)

Based on experience, designer provides

professional input (wall layout, element size…) inaccordance with preliminary architectural layout

and estimate the construction cost for comparison.

Build up simple computer model to test the

structural form if required.

After confirming the scheme, prepare detaildesign and submission to BD for approval and

tender documents

AP, RSE and RGE to supervise the construction

work on site and report to BD on completion



DESIGN CRITERIA



2. Design Criteria(Most details are specified in above “Building Design Standard”

The structural criteria are:

Adequate strength against failure (Ultimate limit state) e.g.stability of building, strength of element…

Adequate lateral stiffness (Serviceability limit state) e.g.deflection of building, comfortable requirement

An efficient performance during the service life of the building(Serviceability limit state) e.g. cracks, durability, fire protection..



Loading Gravity Load

Dead Load (self weight of member or imposed dead load such as finishes, fixed

partition..)

Live Load (as requirement specified in B(C)R) e.g. the loading requirement for domestic

floor or for classroom is different)

Wind Load (as HK CoP of Wind 2004)

Seismic Load (Being studied by the Government)



Gravity Load Dead Load

Self Weight (24KN/m3)

Finishes (thickness x 24/m3 =?/m2)

Fixed partition (thickness x height x 24/m3 = ?/m)

Imposed Load As HK Building (Construction) Regulations (BCR)

Domestic area = 2.5 KN/m2

Common area = 3.0 KN/m2

Partition Load (non-fixed) = thickness x height x 24 /3

= ?/m2

Live load reduction factor (as BCR)



Imposed Live Load Requirement as B(C) R



Strength and Stability

The structure must have adequatestrength to resist, and to remain stableunder, the probable worst load actions

Any additional stresses caused byrestrained differential movements due to

creep, shrinkage or temperature must beconsidered.



Stability Checking

Checking Overturning



Stabili ty Check on

underground structure

Uplift Checking



Beneficial case : 1.0D +1.4 Water uplift pressure to check the bottom slab



Excess Response to Wind Loads(Ref: CoP Cl. 7.3.2)

Excessive accelerations under wind loads that may

cause discomfort or alarm to occupants should beavoided in particular some high aspect ration building(Height /Width i.e. H/B >5)

A static or dynamic analysis could be employed intoaccount the pertinent features of the structure and itssurroundings. Limited deflection at the top of a buildingto H/500 when considering a static characteristic windload should result in an acceptable environment for

occupants in normal buildings.

Partitions cladding and finished., etc. need to bespecifically detailed to allow for the anticipated relative

lateral deflection in any one storey under thecharacteristic wind load.



Deflection (CoP Cl. 5.2)

The deflections or deformations from all load types shouldnot impair the strength or effective functioning of a structure,supporting elements or its components, nor cause damageto the finishes. For typical structures, the deflection limitsare:

H

Δ



Excess Response to Wind LoadsWhen a dynamic analysis is undertaken, themaximum peak acceleration of building should beassessed for wind speeds based on a 1-in-10-yearreturn period of 10 minutes duration with thefollowing limits:

The use of dampers on tall and slender buildingsshould be supported with dynamic analysis andspecialist literature should be consulted.

0.25m/s2Office or Hotel

0.15m/s2Residential

Peak AccelerationFunction



Detailing -Ductility RequirementHK CoP 2004 : Clause 9.9



STRUCTURAL FORM



Common Form of Residential

Building in Hong Kong

Tower(Shear wall structure)

Podium(Transfer plate

structure)

Foundation

structure(Pilecap + Pile)

Carpark

(Frame +Shear wall

structure)



High-Rise Behaviour A high-rise structure is essentially a vertical cantilever

Behaviour of tall building subjected to shear, moment andtorsion

The resistance of the structure to the external moment isprovided by flexure of the vertical components, and by theiraxial action acting as the chords of a vertical truss.

The floor slabs, which act as a rigid diaphragm, play animportant role in distributing horizontal shear and torsion tothe vertical components



Cantilever Deflections



OverturningResistance

Moment

Axial force

Shear

Force



Horizontal Force Flow

Rigid diaphragmWind Load



Building under Wind

Plan Plan

P l an

Unbalanced force at long

building to create torsion

force on building

Deflection of

building



Building Horizontal StructureCommon beam and slab system at residential building

Beams are arranged to support

the slab, stair, partition..

Some beams (called lintel) to

link wall together to form the

wind resistance structure

Slab is designed as one way or

two way slab depending on the

span and the normal thicknessis arranged from 100mm to

400mm



Scheme A: 3 nos. 2.7m x 8mone way slab + 8m span beam

Scheme B: 2 nos. 4m x 8m

one way slab + 8m span beam

Ex. 1 -To select the economical structural form for a slab

between four sides of wall

Finishes thickness = 25mm, Partition load = 2.0KN/m2



Cost of Construction

Concrete = HK$ 700/m3

Steel= HK$ 8,000 /T

Formwork = HK$ 500/m2



Detail of cost breakdown on slab design(Scheme B)

Concrete

Volume of Concrete slab (160mm thick) : 0.16x8x8=10.24m3

Volume of Beam (0.5x 0.75mm deep) = 0.5x(0.75-0.16)x8 =2.36 m3

Cost of Concrete = (10.24+2.36) x 700 = 8820

Formwork

Area of Formwork = 8x8 + (0.75-0.16)x8x2 =73.44 m2

Cost of Formwork = 73.44 x 500 = 36720

SteelTotal weight of Steel = 1953 Kg

Cost of Formwork = 1953 x8000/1000 = 15624

Total Cost = Concrete + Formwork + Steel = HK $ 61,164



Symmetrical

Building

Unsymmetrical

Building with

Additional

Twisting

force



Frame Structure

Economical for buildingbelow 20 storey

Wind resistance structure is

formed by the rigid joined

beam and column structure



Shear WallEconomical for building

between 20 to 50 storeyWind resistance structure is

formed by the cantilever

behavior of wall or the axial

force of wall when linking

together

Common structural form of

residential, hotel building with

more partition walls



Tube Structure Economical for buildingbetween 50 to 70 storey

Wind resistance structure

is formed by the axial force

of internal and exterior

tube



Outrigger

Used for building over 70

storey to reduce thedeflection of building.



Shear Wall Building Behaviour

Wind load transmitted to individualshear wall (without linkage) by the floordiaphragm

Shear wall acts as cantilever to resistwind load



Shear Wall Building Behaviour -Coupled Shear Wall

For single shear wall, the reaction at

base in moment (M) only.

If two walls are linked together by beam

(lintel), the couple action will change the

reaction at base from moment force to

axial force which is more economical



Relative properties of various wall geometries

R l ti d fl ti f l d ll



Relative deflection of coupled walls



To enhance thestiffness of building by

increasing the moment of

inertia of each wall

section (for rectangular

section I = bd3/12)

With same area,

moment of inertia (I) canbe obtained by flange

section better than

rectangular section

sacred



lintel



Ex. 2 -To identify the structural wall layout which can



provide the block to be built up to 50 storey

Preliminary Architectural Plan



Q&

A

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