Design of Fastenings for Dynamic Actions Teheran

Seismic design for anchors 1www.hilti.com

Design of Fastenings for Dynamic Actions (Seismic Loads)

Seminar Teheran

November , 2006


Jenö Varga

1976 - 1981: Civil Engineering Diploma, Technical University of Budapest, Hungary

1981 - 1982: Structural Designer, “Olajterv” – Budapest, Hungary

1882 - 1983: Engineer, Hungarian Army, Hungary

1983 - 1991: Research Officer, Technical University of Budapest, Hungary 1984 - 1987: Post-graduate Research, The University of Adelaide, Australia

1991 - 1993: Senior Lecturer, The University of Witsvatersrand, Johannesburg, South Africa 1991 – 1993 Post-Doctoral Research

1993 - 1998: Research Officer, IWB, The University of Stuttgart, Germany approval and development tests of various pre-cast and post-installed

fasteners, contribution into CEB Fastening Design 1995 – 1997: Teacher Diploma, The University of Budapest

1998 - 2000: Teacher, International School of Stuttgart, Germany

Mathematics, Physics, Computing – IB course Higher lever

2000 - : Engineer, Hilti AG, Fastening Technologies (application support for non-code cases – fastenings, training Hilti staff,

calculation control, Profis Anchor - project manager, HAT-175 developer)


Basics

induced accelerations activate forces of inertia and dampingDifferences to static design, classification, characteristics:

Classification Fatigue Seismic Shock

Number of

load cycles

Rate of strain

Examples

104 < n < 108 101 < n < 104 1 < n < 20

10-6 < < 10-3 10-5 < < 10-2 10-3 < < 10-1

•Traffic loads•Machines, cranes•Ventilators•Wind, Waves

•Earthquakes•Artificial earthquakes

•Explosions•Abrupt Structure failure•Crash Barriers

Ratio FR,dyn/FR,stat 30 (!) - 100% 80 - 130% 100 - 200%


Examples EarthquakeTypical Fastening Problems (structural and non structural)

Suspended Ceilings

San Francisco Airport

Loma Prieta earthquake

1989

Toppled and damaged

furniture,City Hall Kobe, 1995

Falling wall panels

Public Building, Kobe, 1995

Damages in a Switchyard

Managua, 1972

Destroyed column fixing

San Francisco, 1989


Earthquake Relevance


Video from Hyogo-Ken Nanbu EarthquakeKobe, JapanJanuary 17, 1995 5:46 am

moment magnitude: 7.2 (JMA)loss of life: 5,200injured: > 26,000homeless: > 300,000estimated total loss: $100 billion

Kobe2.mpg


Examples Shock

Typical Fastening Problems (structural)

Crash barrier fixing on concrete

(e.g. on bridges, etc.)

Explosions

(e.g. installations in civil shelters)

Emergency Installations

(e.g. emergency stop

fixings in elevators)


Examples Fatigue

Machine fixing

(e.g. pumps, ventilators,

punching machines, etc.)

Robot fixing

(e.g. in automobile

industry, etc.) Fixing of cranes,

hydro-jacks, etc.)


Suitability of Different Anchor Types

++ very suitable + suitable – not suitable

Anchor Type

Base Material

Displacem

ent controlled

Bonded

Bonded E

xpansion

Concrete screw

Torque controlled bolt

Torque controlled

sleeve

Undercut

Un-cracked concrete + ++ ++ ++ ++ ++ ++Cracked concrete Small cracks w<0,5mm

- + ++ ++ ++ ++ ++

Cracked concrete Medium cracks 0.5mm<w<1.0mm

- - + + + ++ ++

Cracked concrete Large cracks w>1,0mm

- - - - - + ++


General Rules for Seismic Safe Design

• EQ-proof position and fastening

• EQ-proof design of the fixing

• Limitation or allowance of displacements

• Additional Fixings as constructive measure

Design Constructive

measures

Examples • design of anchors

• design of cross-

sections, etc.

• screws, clamping etc. to limit displacements

• struts to take horizontal loads

• free space to allow differential displacements


Design for Earthquakes

Main difficulties for a proper earthquake design

1. Predictability of Seismic activities and loads Ground acceleration

time

time

Floor acceleration

Equipment acceleration

time

2. Cracks 3. Ductility


Design for Earthquakes

FP static horizontal loadZ factor for seismic zone (from code)I factor for accelerationCP factor for stiffness of structureWP mass of element / equipment

ppp WCIZF

Example: Uniform Building Code (USA)

•estimation of horizontal load (static)

•resistance: safety factor 4

“fasteners shall be designed for four times the forces determined“


3 main design possibilities

Stiff fixture: ”equivalent force process” Based on the building floor acceleration and the mass of the fixture.

Elastic fixture: “response spectra process” low natural frequency, the load on the fas-tening is governed by the fixture's response to dynamic incitation. Acceleration of the fixture is relevant when using this process.

Ductile fixture: “plastic design” fastening design is based on the maximum load that can be applied to the anchor when plastic deformation takes place.

stiff fixing

elastic fixing

ductile fixing


Example: Equivalent Force Processafloor = 0.75 g ≈ 7.5 m/s2 (e.g. from codes)F=m . afloor

F=500 . 7.5 = 3,750 N = 3.75 kN Vd=F / 4Vd=3.75 / 4 = 0.94 kNNd= F . hCG / (2 . b)Nd= 3.75 . 100 / (2 . 60) = 3.13 kN

Sd Vd2

Nd2

kN3.273.130.94S 22d

Case Study Seismic Design


Example: Response Spectra Process

Ventilation unit mounted on springs (forinsulation reasons): f0<15Hzafloor = 0.75 g ≈ 7.5 m/s2

Increasing factor due to low natural frequency: factor Aequip = 2.0 (out of literatureor manufact. informations)-> aequip = Aequip*afloor ≈ 15 m/s2 F = m*aequip

F = 600*15 = 9,000N = 9.0kNVd = F/4Vd = 9.0/4 = 2.25 kNNd = F*hCG / (2*b)Nd = 9 . 80 / (2*175) = 2.06 kNFadm,eq = Rd,crack > Sd



Example: Design with Plastic Moment

Installation channels used as columns for ventilation fixing:W=3’000mm3,fy=235N/mm2

Mplast = fy . WMplast = 235*3’000 = 705’000 NmmMplast is generated Fplast, acting at a height, hp:Fplast = Mplast/hp

Fplast = 705’000 / 500 = 1,410 N = 1.41 kN



Seismic Design with Hilti PROFIS Anchor program


DIBt Guideline for the use of anchors in Nuclear Power Plants (NPP)

Impact categories:

A) probability of 1 occurrence during service life (design earthquake, plane crash, explosions...)

B) probability of 10 occurrences during service life

C) service loads (static) and incidents with a probability of 10 occurrences during service life

For safety relevant fixings in NPP, DIBt asks for additional tests beside thestatical DIBt or ETA-approval.

DIBt: Deutsches Institut für Bautechnik (German Institute for construction technology)

Special Applications: Nuclear Power Plants - Impact


Design according to concrete-capacity-method, with special load and

material safety factors

Load safety factors:

G=Q= 1.0 for category A

1.2 for category B

1.4 for category C

Material safety factors:

concreteMc=Mp= 1.7 for category A

1.9 for category B

2.1 for category C

steel: according to ETAG, Annex C

(Ms=1.4 for tensile loads and Ms=1.25 for shear loads)

Special Applications: Nuclear Power Plants - Design

DIBt Guideline for the use of anchors in Nuclear Power Plants (NPP)


• all anchors are set in closed hairline cracks

crack width at test load criteria - displacement at 0.5 Fu,m

1 1.5 mm - variation of Fu,m

- value of Fu,mt

N

- no failure

2 1.5 mm - develop. of displacement in time

N

t

- no failure

3 - develop. of displacement in time

w

t

1.5mm

1.0mmt

N

t

N

tV

- variation of displ. at Fu,m

4 1.0 mm - variation of Fu,m

- no failure

5 1.0 mm - final ultimate shear load

Special Applications: Nuclear Power Plants - TestsDIBt Guideline for the use of anchors in Nuclear Power Plants (NPP)


Many different test procedures according to national regulations

Excerpt from ICC ES Acceptance Criteria (seismic method 6.2.7.2):

• Tension: pulsating sinusoidal seismic cycle• shear: alternating sinusoidal seismic cycle• frequency 0.1 to 0.2 Hertz• at least 5 anchors• shallowest and deepest embedment depth

Earthquakes: Testing of Anchors


• Maximum load Ns: 1.5tension value for which recognition is desired

• The minimum load value shall not be smaller than 5% of Fu

• Uncracked concrete

Ns Ns: maximum tension test load

Ni Ni: a load midway between Ns and Nm

Nm

Nm: 1/4 of the average ultimate tension load Tref

Earthquakes: Testing of Anchors - Tension

10 30 100

load

cycles


• Maximum load Vs: 1.5shear value for which recognition is desired

• The value for which recognition is desired shall not be larger than 133.33 percent of the allowable static loads under the same conditions

• Uncracked concreteVs

Vs: maximum shear test load

Vi

Vi: a load midway between Vs and Vm

Vm

Vm: 1/4 of the average ultimate tension load Tref

-Vs

-Vi

-Vm

Earthquakes: Testing of Anchors - Shear

10 30 100

load

cycles


not suitable for EQ limited suitable for EQ

General Improvement of Fixings to Steel Beams

Standard Fixings



Improvement with

Hilti MF-CS



Securing of

channels with

End- Stoppers



Securing of

channels with

End- Stoppers

Securing of

channels with

DX


Installations: Pipes

The distance between the supports, the size and mass of the pipe and the horizontal acceleration are decisive whether or not struts are necessary.


Installations: EQ Proof Channels

multiple fixing Load Direction

lateral longitudinalType

direct

hanger

console

no additional measures for EQ necessary

stiff U-Joch constructions or struts necessary

no additional struts

additional struts

necessary

ceili

ngw

all

Documents

Design of Fastenings for Dynamic Actions Teheran