naveed anwar, phd progression of structural...

Naveed Anwar, AIT Solutions

Progression of Structural Design ApproachesNaveed Anwar, PhD


Colombo 2015

Kathmandu 2016

Bangkok 2016

Singapore 2016

Manila 2016

Oman 2017

Dubai 2017

Dhaka 2014

Yangon 2015

Islamabad2017

Naveed Anwar, AIT Solutions 3

Why this Seminar?

And why are these topics important

Demand and Complexity is Increasing for the Built Environment


Population Growth is in Developing World

6

Source: www.prb.org, volume no. 66, July, 2011.

Less Developed Countries will need more Housing and infrastructure for nearly

2 Billon more people

http://www.prb.org/


(www.un.org)


•

•

•

•

•

•

8

Naveed Anwar, AIT Solutions9

Marshall Strabala

Tall Buildings

• Need less space• Need less infrastructure• Need less commutes• Need less façade• Consume less material• Are overall economical• Environmentally

sustainable


Japan, 4000m Sky Mile Tower, 1700 m JapanDubai City Tower, 2400 m One Dubai Tower, 1008 m


The Twisting Turning Towers Trend

Source: CTBU Report, 2015


97%

13

Very Tall

(1189)

Super Tall

(115)

Mega Tall(3)

Low Tall

Low Rise

>600 m>300 m>200 m>100 m<50 m

Tall(3852)

>150m



•

•

•

•

•

•

•

•

•

•


Relatively Tall. Both for public and the professions who design and construct

ProportionSlenderness, in plan and in elevations

Systems and TechnologiesUses something “different” than ordinary buildings


•

•

•

•

•

•

•

•

•

• Minimize floor depth

• Minimize column size

• Minimize structural cost

• Inclined columns

• Free form

• Unusual requests


Needs Innovations in Structural Design Approaches

Naveed Anwar, AIT Solutions22

Is my Structure safe?

(What level of Richter earthquake my structure sustain? Or what tornado level can it withstand,

or is it safe for explosions orHow long can it withstand the fire?

….. )


How long do we have

before the building will

collapse in this fire?

- Asks the Fire Chief from the structural

engineer

1974


https://www.youtube.com/watch?v=FagbC09BO2o


The Intent of Structural Design is to ensure public safety, minimize damage to built environment, help preserve continuity of life activities…


Intuitive Design

-

-

-

-


Ancient masterpieces were built before the modern approaches

Master builders had freedom to dream and to realize them


Should design be based on

“Engineering Judgment” and

intuition,

Or

controlled by explicit

computations and, restrictive

limits and rational approaches


It is by logic we prove, but by

intuition we discover


Félix Candela


What a Structural Engineer said !

Hardy Cross, 1885-1959


Intuitive Design

Code Based Design

-

-

-


Main Challenges !(specially for Tall Buildings)

33

Win

d

Earthquake

Self Weight

Occupancy

and


Stability

01

Strength

02

Deformation

03

Drift

04

Ductility

05

Energy Dissipation

06

Motion Perception

07

34


•

•

•

•

Spirit of the code isto help ensure Public Safety and provide formal/legal basis for design decisions

Compliance to letter of the code is indented to meet the spirit


“Rebuilding of London

Act” after the “Great Fire of

London” in 1666 AD.

In 1680 AD, “The Laws of

the Indies” Spani

sh Crown

London Building Act of

1844.

In USA, the City

of Baltimorefirst building code in 1859.

In 1904, a Handbook of the Baltimore

City

In 1908 , a formal

building code was

drafted and adopted.

The International

Building Code (IBC) by (ICC).

European Union,

the Eurocodes.


UBC, IBC

ACI, PCI, CRSI, ASCE, AISI,

AASHTO

British, CP and BS

Euro-codesChina, USSR,

Japan


• Traditional codes govern design of general, normal buildings

Over 95% buildings are covered, which are less than about 50 m

• Not specifically developed for tall buildings > 50 m tall

• Prescriptive in nature, no explicit check on outcome

• Permit a limited number of structural systems

• Do not include framing systems appropriate for high-rise

• Based on elastic methods of analysis

• Enforce uniform detailing rules on all members

• Enforce unreasonable demand distribution rules

• Do not take advantage of recent computing tools


Traditional

Design

approach for

Wind and

Earthquake is

different and is

often

in-consistent

and opposing


Seismic LoadWind Load

Depend on •focus of earthquake

•Shaking intesity

•ground conditions

•Mass and stiffness

distribution

Depend on•Wind speed

• terrain

• topography of the location

• Force increases with height

•Geometry and exposed area

m

ügv

A

Excitation is an applied displacement

at the base

force will be distributed along interior

and exterior lateral load resisting

elements

Excitation is an applied pressure or

force on the facade

force will act mainly on exterior

frames then transferred to floor

diaphragms


For most buildings, dynamic wind response may

be neglected

Gust factor approach predict dynamic

response of buildings with reasonable accuracy

Structures are designed to respond elastically

under factored loads

Structures are designed to respond inelastically

under factored loads

it is not economically feasible to design structures

to respond elastically to earthquake ground

motion

Design for Seismic EffectsDesign for Wind Load


•

•

•

•

42


•

•

•

•

•

43


Intuitive Design

Code Based Design

Performance Based Design

-

-

Earthquake

Wind


• Lack of explicit performance in design codes is

primary motivation for performance based

design

• Performance based methods require the

designer to assess how a building is likely

perform extreme events and their correct

application will help to identify unsafe designs.

• Enables arbitrary restrictions to be lifted and

provides scope for the development of

innovative, safer and more cost-effective

solutions


Based on FEMA 451 B


Structural Displacement

Lo

adin

g S

ever

ity

Resta

urant

Resta

urant

Resta

uran

t

Ha

zard

Vulnerability

Consequences


Performance based design investigates at least two performance objectives explicitly

Service-level Assessment

Negligible damage with frequent hazards

(Earthquake having a return period of about 50)

Collapse-level Assessment

Collapse prevention under extreme hazards

(the largest earthquake with a return period of 2500 years)

Code’s arbitrary “Design Level”


Intuitive Design

Code Based Design


-

Wind

Earthquake


Earthquake and Wind PBD are Compatible!

50

Site specific Seismic Hazard Study

Site specific Climate Analysis

Various Earthquake levelsSLE, DBE, MCE etc

Various Wind Return period and Velocities

Hazard Response Spectrum

Wind Force in Frequency Domain

Ground Motion Time History

Wind Tunnel Pressure in Time Domain

Earthquake Wind


Intuitive Design

Code Based Design


-

Wind

Earthquake

Is this acceptable?Even though it satisfies CBD and may even satisfy PBD

Questions still un-answered

• What if the chance that performance level is not achieved?

• What is the risk ?

• What are the consequences?

• What if the performance levels are not sufficient?

Code based was implicit, with not confirmation of response

PBD is explicit, can help to confirm the response and

performance level

Why do we need to go Beyond PBD

• For public and society, the performance criteria still does reduce the effects of the events, but it can reduce the risk level

• The non structural damage is not acceptable in modern buildings

• The disruption and loss goes much beyond the building

• Insurance companies want to have greater reliability of assessment of risk and damages

Design Approaches

Intuitive Design

Code Based Design


Consequence and Risk Based Design

-

Wind

Earthquake

Consequence Based Engineering

• It is not enough to say “Cracking and non-structural damage is acceptable, as long as structure does not collapse”

• A natural extension of the performance-based design approach

• Structural consequences > DDD (dollars, deaths and downtime) (Porter, 2003).

56

The trigger of an event is not important, the consequences of an event are

Risk Based Design Process

Safety Studies (Probability and

Consequence Analysis)

Risk Quantification and modeling

Safety Critical Element

Design Accidental

Loads

Structure Design

Verification

Extreme Events

should be handled

Consistently

58

Earthquakes, Wind, Blast, Progressive Collapse, Impact

What Next: What is still missing?


•

•

•

60

Design Approaches

Intuitive Design

Code Based Design


Consequence and Risk Based Design

Resilience Based Design


Green Buildings Resilient Buildings

62

Main authors : ArupSupported by USRC and many others


RESILIENCE

Economic

Social

Organizational

Technical

Resourcefulness

Redundancy

Rapiditty

Robustness

Lower

Consequences

Faster

Recovery

More Reliability

4 Dimensions of

Resilience

4 Properties of

Resilience

3 Results of Resilience

63


•

•

64

Economic Loses

Loss of Community and Culture

Loss of Quality of

Life

Go Beyond Life Safety


Restaurant Restaurant

Resta

uran

t

Operational (O) Immediate Occupancy (IO) Life Safety (LS) Collapse Prevention (CP)

0 % Damage or Loss 99 %

Ref: FEMA 451 B

CasualtiesLowest Highest

Rehab Cost to Restore after eventLowest Highest

Retrofit Cost to Minimize ConsequencesHighest Lowest

Downtime for RehabLowest Highest

Impact on Sustainability of CommunityLowest Highest


ARUP

About Related work at AIT

Related work at


68

Asian

Institute of

Technology

(AIT)

• Established in Bangkok in 1959

• Leading regional postgraduate

institution

•Actively working with public and

private sector in the region

•Collaborating with some of the top

universities in the world


69

Professional Education Integrated Solutions

ResearchAcademics


What is being done at AIT

70

Structural LabShake table, Cyclic

Actuator, strong floor

Teaching, Research Tall Buildings, Wind

and Earthquake Engineering

Practical Experience of over 100 PBD

Projects

Wind Tunnel Lab

Development and application of Integrated PBD and RSBD for Wind and Earthquake

CSiSoftware Developer

PartnersStructural Engineers


“Building upon AIT schools,

labs, research centers and

alumni resources to advance

technological development

in the region”

Mission

71

Tools: How to design efficiently?


•

•

•

•

•

•

•


• Initially, computers were used to

program the procedure we had

• Now, we develop procedures that

are suited for computing


Integrated 3D Bridge Design Software

Integrated Software for Structural Analysis and Design

Integrated Analysis, Design and Drafting of Building Systems

Integrated Design of Flat Slabs, Foundation Mats and Spread Footings

Nonlinear Analysis and Performance Assessment for 3D Structures

Design of Simple and Complex Reinforced Concrete Columns


•

•

•

•

•

•

•

•

77


Should design be based on

“Engineering Judgment” and

intuition,

Or

controlled by explicit

computations and, restrictive

limits and rational approaches


Architectural Design

Preliminary Sizing

Structural Modeling

Structural Analysis

Code Based Design



Heuristic Approach to Quick Design and Response Prediction of Tall Buildings


•

•

•

•

•

•

81


More explicit way to define and measure performance

Obtain consistency between EQ and Wind design and performance

Economy and cost effective design for both wind and EQ

Enhanced overall performance and reliability of buildings

Accelerate innovations in the structural design process

Advance the state of the art to integrated resilience based design

84

Thank you

naveed anwar, phd progression of structural...

Documents