Robustetea structurilor metalice

7/23/2019 Robustetea structurilor metalice

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1.Structure characteristics

Structure 6 stories (P+5E)

Span 7.5 m

Level height: 4 m

Bay 7.5 m

Location: Timsoara

The columns are are made from europrofiles, having a Maltese cross cross-section. Profiles

used-HE650BBeams- principal beams are IPE 550

-secondary beams IPE 400

Structura cladirii

Vedere in plan Sectiune transversala Sectiune longitudinala


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Cadrele din transversal si longitudinale sunt cadre cu noduri rigide(MRF).Planseul structurii este realizat dinbeton armat si reazema pe grinzile secundare.

2. Design of the structure

2.1 Loads

Permanent load- 5 kN/sqm

Live load -4 kN/sqm

Loads by tributary area for intermediary beams

Permanent load: 5 kN/sqm x 1.875 =9.375 kN/m

Live load : 4 kN/sqm x1.875=4.68 kN/m

Loads by tributary area for end beams

Permanent load: 5 kN/sqm x 0.9475 =4.68 kN/m

Live load : 4 kN/sqm x0.9475=4.68 kN/m


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Permanent load

Live load


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2.2 Calculation of masses

M1=36 t

M2=18 t

M3=9 t

M1

M2

M3


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2.3 Seismic action

Location Timisoara

Ag=0.20g

TB=0.14 s TC=0.7 s TD=3.00 s

Behaviour factor for moment resisting frame is q=6.5

Design response spectrum obtained and introduce in Sap200

2.4 Load combinations

2.4.1 Ultimate limit states combination

1.35 P + 1.5 L

2.4.2 Serviceability limit states combinations

1 P + 1L2.4.3 Seismic combination

1 P + 0.4 L + Aed

For the design of the columns the following combination was introduced

1 P + 0.4 L + Aedwhere is the overstrength factor equal to 3


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2.5 Structures modes of vibration

Mode 1 T=1.03 s

Mode 2 T=1.00 s


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Mode 3 T=0.88 s

Sum of effective modal mass must be higher then 90% of the total mass of the structure

2.6 Checking of displacements

2.6.1 Checking of displacements at SLS

The displacements at SLS were checked form the following combination

1.0 P + 0.3 L + vqAED where v=0.5 and q=6.5

TABLE: Modal Participating Mass Ratios

OutputCase StepType StepNum Period UX UY UZ SumUX SumUY SumUZ RX RY RZ SumRX SumRY Sum

Text Text Unit less Sec Unit less Unit less Unitless Unit less Unit less Unit less Unit less Unit less Unit less Unit less Unit less Unit

MODAL Mode 1 1.033347 0.78969 0 0 0.78969 0 0 0 0.95156 0 0 0.95156

MODAL Mode 2 1.005628 0 0.79128 0 0.78969 0.79128 0 0.92829 0 0 0.92829 0.95156

MODAL Mode 3 0.888876 0 0 0 0.78969 0.79128 0 0 0 0.79088 0.92829 0.95156 0.7

MODAL Mode 4 0.308018 0.11453 0 0 0.90422 0.79128 0 0 0.00026 0 0.92829 0.95182 0.7

MODAL Mode 5 0.300869 0 0.11367 0 0.90422 0.90495 0 0.00031 0 0 0.9286 0.95182 0.7

MODAL Mode 6 0.265633 0 0 0 0.90422 0.90495 0 0 0 0.11365 0.9286 0.95182 0.9

MODA L Mode 7 0.155558 0.05032 0 2. 995E- 19 0 .95454 0 .90495 3.003E-19 5.511E- 19 0.00305 0 0.9286 0 .95487 0 .9

MODA L Mode 8 0.152792 0 0.04989 6. 911E- 19 0.95454 0.95484 9.915E-19 0. 00292 1.8E- 19 0 0.93152 0.95487 0.9

MODAL Mode 9 0. 134677 0 0 8. 786E- 20 0.95454 0.95484 1. 079E- 18 1. 579E- 20 1. 111E- 20 0.05012 0.93152 0.95487 0.9

MODAL Mode 10 0. 094599 0. 0272 0 7. 798E- 19 0. 98175 0. 95484 1. 859E- 18 1. 667E- 16 0. 00015 0 0. 93152 0. 95501 0. 9

MODAL Mode 11 0.093327 1.192E-20 0.02697 3.841E-17 0.98175 0.98181 4.027E-17 0.00015 3.444E-17 0 0.93167 0.95501 0.9

MODAL Mode 12 0. 082097 0 0 1. 858E- 17 0.98175 0.98181 5. 885E- 17 3. 109E- 18 1. 78E- 18 0.02711 0.93167 0.95501 0.9


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Displacements on X direction

Nivel Dr,SLS [mm] Dr,a SLS1 5.2

26.252 9.75

3 10.07

4 8.775 6.82

6 4.55

Displacements on Y direction


26.252 9.423 9.42

4 7.15

5 6.176 4.22

2.6.2 Checking of displacements at ULS

The displacements at SLS were checked form the following combination

1.0 P + 0.3 L + cqAED and q=6.5 and c=1

Displacements on X direction


87.52 19.5

3 20.144 17.54

5 13.64

6 9.1

Displacements on Y direction

Nivel Dr,SLS [mm] Dr,a SLS

1 9.7487.52 18.84

3 18.844 14.3

5 12.346 8.44


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2.7 Checking for the stability of the structure under gravity loads.

Second order effects P-

The verification was done under the following case of loading

1.35 p + 1.5 L

In Sap2000 a new load case was create,type buckling.

After the analysis, the coefficient of critical loading crit was obtained as being 33.

Because if this the second order effects can be neglected and the structure is classified as

being a structure with fixed joints crit.>10

2.8 Checking the resistance of the beams

The most demanding combination is

1.35 P +1.5 L +Imperfections.


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2.9 Checking the resistance of the columns

For the column verification a new combination was introduced tacking into account the

overstrength of the columns

1.0 P +0.3 L + AED

Where is an overstrength factor equal to 3.

=1.1 ovMpl,RD/MED


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Tying method

Ties have to be placed: Around the perimeter at each level and; Internally in two perpendicular directions for the tying of the columns and the walls


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Key element method

Exceptional event: impact of a vehicle

2 facades are considered with the 2 shown columns.

Loads are considered for the impact with a vehicle:

-on X direction a force of 500 kN

-on Y direction a force of 250 kN.

-the forces are not considered in the same time.

Three situations are taken into account

1. Column 1 under force of 500 kN at 1.5 m height- X direction2. Column 1 under force of 250 kN at 1.5 m height- Y direction

3. Column 2 under force of 500 kN at 1.5 m height- X direction

Column 1

Column 2


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Checking of the column

Situation 2:Column under force of 250 kN-Y direction


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Bending moment diagram from the concentrated force

Checking of the column


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Alternate path load method

Study the load redistribution within the structure following an extreme loading

A supporting member (column) is removed one at a time, to ensure that the building remains

stable and the admissible local damage is not exceeded.

After the removal of the member the structure must remain steady as a whole.

For this method, 4 simplified scenarios are taken into account. Each scenario considers the

removal of a different column form the ground floor.

First scenario: marginal column

Second scenario: corner column

Third scenario: internal column

Fourth scenario: Corner and marginal column

First scenario: Removal of a marginal column

Loads assessment

For the analysis the following combination of loads is considered

1.0 P + 0.5 L

This combination will be denoted as the Accidental combination


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Step 1

From the accidental combination, the axial force in the column to be removed is obtained.

NED=1420 kN.

Step 2

The column is removed, and the axial force from the column is introduced as a concentrated

force

Step 3

Defining the ramp functions.2 ramp functions are defined.1 function for the loads from the

accidental combination and the other function for the load for the axial force in the column.

Function 1-for the loads from the accidental combination


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At time equal to 0 - value of loading is 0

At time equal to 1value of loading is 1

At time equal to 4 - value of loading is 1

Function 2for the axial load in the column

The removal of the column should be made instantaneously.\


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Step 5

A time history load case will be created, where the 2 types of loading will be introduced-the

gravity loads form the accidental combination and the loads form the removal of the column.

Step 6

Assignment of plastic hinges

At the end of each beam, plastic hinges will be assigned

Results


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It can be observed that the maximum displacement of the joint, above the removed column is

32.8 mm

Rotation: 0.0017 rad

The elements remain the elastic zone, no plastic hinges are formed.

Alternate path load methodScenario II

Removal of a corner column

The same steps are to be followed.


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Results


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Maximum displacement of the joint 30.1 mm

Rotation 0.0021 rad.

No plastic hinges are formed.

Alternate path load methodScenario III

Removal of a central column

Same steps are to be followed


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Results

Maximum displacement of the joint is 41.9 mm.

Rotation is 0.0001 rad.

No plastic hinges are formed


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Alternate path load methodScenario III

Removal of a corner and a marginal column.

The columns will be consider inefficient in the same time.

Results

Displacements at the corner joint


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Max displacement is at the corner joint-62.1 mm

Rotation 0.00259 rad

No plastic hinges are formed

Displacements at the marginal joint


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Displacement of the joint 52.9 mm.

Rotation 0.00217 rad.

No plastic hinges are formed.

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Robustetea structurilor metalice