2 7 ° G N G T S , T r i e s t e , 6 - 8 o t t o b r e 2 0 0 8 A . M a s i , M . V o n a DiSGG, Università della Basilicata, Potenza DiSGG, Università della Basilicata, Potenza 27° Convegno Nazionale GNGTS 27° Convegno Nazionale GNGTS Trieste 6-8 ottobre 2008 Trieste 6-8 ottobre 2008 Angelo MASI Angelo MASI , Marco VONA , Marco VONA VALUTAZIONE NUMERICA E SPERIMENTALE DEL VALUTAZIONE NUMERICA E SPERIMENTALE DEL PERIODO DI VIBRAZIONE DI EDIFICI PERIODO DI VIBRAZIONE DI EDIFICI ESISTENTI IN C.A. ESISTENTI IN C.A.
22
Embed
27° GNGTS, Trieste, 6-8 ottobre 2008 A. Masi, M. Vona DiSGG, Università della Basilicata, Potenza DiSGG, Università della Basilicata, Potenza 27° Convegno.
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
27°
GN
GT
S, T
ries
t e, 6
- 8 o
ttob
re 2
008
A. M
asi,
M. V
ona
DiSGG, Università della Basilicata, PotenzaDiSGG, Università della Basilicata, Potenza
27° Convegno Nazionale GNGTS27° Convegno Nazionale GNGTS
Trieste 6-8 ottobre 2008Trieste 6-8 ottobre 2008
Angelo MASIAngelo MASI, Marco VONA, Marco VONA
VALUTAZIONE NUMERICA E SPERIMENTALE VALUTAZIONE NUMERICA E SPERIMENTALE DEL PERIODO DI VIBRAZIONE DI EDIFICI DEL PERIODO DI VIBRAZIONE DI EDIFICI
ESISTENTI IN C.A.ESISTENTI IN C.A.
27°
GN
GT
S, T
ries
t e, 6
- 8 o
ttob
re 2
008
A. M
asi,
M. V
ona
STATEMENT OF THE PROBLEM
• The effects of seismic actions on buildings can be determined using various methods of analysis.
• Assuming a linear-elastic behaviour of the structure, two methods can be used:- the lateral force method of analysis (LFMA), for “simple” buildings;- the modal response spectrum analysis (MRSA), applicable to all types of buildings.
• Both methods make use of an elastic ground acceleration response spectrum (elastic response spectrum) in the evaluation of the seismic response, where the calculation of the fundamental period T1 (LFMA) or periods (MRSA) of the structure has a main role.
27°
GN
GT
S, T
ries
t e, 6
- 8 o
ttob
re 2
008
A. M
asi,
M. V
ona
STATEMENT OF THE PROBLEM
• For the determination of T1, expressions based on methods of structural dynamics (e.g. Rayleigh method) may be used:
• Alternatively, many design codes provide simple expressions to calculate T1 that depend on: - building material (concrete, steel, masonry, etc.), - building type (frame, shear wall, etc.), - and overall dimensions (height, plan length, etc.).
2/1
11
21 /2
N
i ii
N
i ii uFguWT
where Wi is the weight at i-th floor, and ui are the floor displacement due to static applications of a set of lateral forces Fi at floor level i = 1, 2, …, N in an N-story building. Fi may be any reasonable distribution over the building height.
27°
GN
GT
S, T
ries
t e, 6
- 8 o
ttob
re 2
008
A. M
asi,
M. V
ona
Simplified Period – Height Relationship
The typical form of the simplified relationship is as follows:
T1 = Ct Hα
where Ct and α are coefficients theoretically or experimentally derived.
Code / Author Ct α Comments
ATC 3-06, EC8 0,075 0,75 Ct has been obtained from the measured periods of buildings during the 1971 San Fernando earthquale
NZEES 0,09 0,75
NEHRP, Goel and Chopra (1997)
0,0466 0,9 Periods measured in some US earthquakes (from San Fernando 1971 to Northridge 1994), coefficients obtained by subtracting one standard deviation from the best-fit curve
Hong-2000 0,0294 0,804 Periods measured on 21 Taiwanese buildings as subjected to moderate intensity earthquakes
Chopra and Goel (2000)
0,067 0,9 Same data of Goel-1997 but coefficients obtained by adding one standard deviation from the best-fit curve, expression proposed for displacement base design and assessment (DBD)
Crowley and Pinho (2004)
0,1 1 Expression obtained from numerical simulations and bibliographic data proposed for displacement base design and assessment (DBD) in Europe, effect of cracking on member stiffness is considered
Table 1 – Different values of coefficients of period-height relationship for concrete moment resistant frames
27°
GN
GT
S, T
ries
t e, 6
- 8 o
ttob
re 2
008
A. M
asi,
M. V
ona
Simplified Period – Height Relationship
Simplified Period-Height relationship for Concrete Moment Resistant Frames
0,00
0,50
1,00
1,50
2,00
2,50
0 5 10 15 20 25 30H (m)
T1
(s)
T1 (ATC, EC8)
T1 (NZSEE)
T1 (NEHRP, Goel-1997)
T1 (Hong-2000)
T1 (Chopra-2000), DBD
T1 (Crowley-2004), DBD
Force Based Design
27°
GN
GT
S, T
ries
t e, 6
- 8 o
ttob
re 2
008
A. M
asi,
M. V
ona
NUMERICAL SIMULATIONS
Parametric Analysis
Parameters of numerical simulations• Number of Story: 3 cases
• Dimensions in Plan: 2 cases
• Irregularity in Elevation: 3 cases
• Presence and position of Masonry Infills: 4 cases
• Member Stiffness: 3 + 3 cases
Variation in member stiffness is due to beam dimensions (Rigid Beams or Flexible Beams) and to effect of cracking
A parametric analysis has been carried out on several structural types purposely selected and designed representative of typical European RC buildings designed only to vertical loads
Information Source (from the period of construction )
STRUCTURAL TYPES SELECTION and DESIGN
TYPICAL RC STRUCTURES INVENTORY
STRUCTURAL TYPE SELECTION
Simulated Design of Existing R/C Buildings
27°
GN
GT
S, T
ries
t e, 6
- 8 o
ttob
re 2
008
A. M
asi,
M. V
ona 4 Story
2 Story
8 Story
PARAMETRIC ANALYSIS:NUMBER of STORY
27°
GN
GT
S, T
ries
t e, 6
- 8 o
ttob
re 2
008
A. M
asi,
M. V
ona
Totally Infilled Frames (IF, Infilled Frame)
Partially Infilled Frames (PF, Pilotis Frame)
Without Infill Frames (BF, Bare Frame)
PARAMETRIC ANALYSIS:POSITION of INFILLS and BEAM STIFFNESS
2 story4 story8 story
Beam Stiffness
27°
GN
GT
S, T
ries
t e, 6
- 8 o
ttob
re 2
008
A. M
asi,
M. V
ona
PARAMETRIC ANALYSIS:EFFECT OF CRACKING ON MEMBER STIFFNESS
Eurocode 8: Design of structures for earthquake resistance - Part 1: General rules, seismic actions and rules for buildings
In concrete buildings the stiffness of the load bearing elements should, in general, be evaluated taking into account the effect of cracking.
Unless a more accurate analysis of the cracked elements is performed, the elastic stiffness properties of concrete elements may be taken to be equal to one-half of the corresponding stiffness of the uncracked elements Ie / Igross = 0,5
Experimental results (e.g. Kunnath et al., 1995) show that different values Ie / Igross can be adopted to take into account the different effect of cracking on columns and beams (role of the axial load value).Kunnath, K.S., Hoffmann, G., Reinhorn, A.M., Mander, J.B., , “Gravity load designed reinforced concrete buildings - part I: seismic evaluation of existing construction”, ACI Structural Journal, May – June, 1995
27°
GN
GT
S, T
ries
t e, 6
- 8 o
ttob
re 2
008
A. M
asi,
M. V
ona
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0 10 20 30
Height [m]
Per
iod
[T
]
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0 10 20 30
Height [m]
Per
iod
[T
]
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0 10 20 30
Height [m]
Per
iod
[T
]
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0 10 20 30
Height [m]
Per
iod
[T
]
RESULTS OF NUMERICAL SIMULATIONS
Effects of Cracking and role of Infills (BF and IF types)
Igross
Ie = 0.7 Igross
Igross
Ie = 0.7 Igross
Lower valuesLower scatter
Higher valuesHigher scatter
27°
GN
GT
S, T
ries
t e, 6
- 8 o
ttob
re 2
008
A. M
asi,
M. V
ona
RESULTS OF NUMERICAL SIMULATIONS
Period-Height Relationship for RC Buildings (3-D Models)
0,00
0,50
1,00
1,50
2,00
2,50
3,00
3,50
0 5 10 15 20 25 30
H (m)
T1
(s)
BF_Ig
BF_Ie
IF_Ig
IF_Ie
LF1-BF_Ig
LF1-BF_Ie
LF1-IF_Ig
LF1-IF_Ie
T = C HBF_Ig BF_Ie IF_Ig IF_Ie LF1-BF_Ig LF1-BF_Ie LF1-IF_Ig LF1-IF_Ie
Italian RC Building Stock (Gallipoli et al., 2006)
Microtremor measurements on 50 RC Italian buildings have been performed in Potenza town (Southern Italy) and in Senigallia town (Central Italy)
RC buildings under examination were designed taking into account only gravity loads, and were constructed in the period ’50s - ’70s
The buildings exhibit strongly different characteristics both in plan and in elevation
Simple and reliable methodologies have been used to estimate the fundamental period of buildings
Using a three component data acquisition system, the horizontal and vertical components of microtremors at the base and the top of the buildings are recorded
27°
GN
GT
S, T
ries
t e, 6
- 8 o
ttob
re 2
008
A. M
asi,
M. V
ona
EXPERIMENTAL RESULTS Some examples of Italian RC Buildings
Pilotis Building
Irregular in Elevation Building
27°
GN
GT
S, T
ries
t e, 6
- 8 o
ttob
re 2
008
A. M
asi,
M. V
ona
REGRESSION of EXPERIMENTAL RESULTS
T1 = 0,015 HR = 0,87
0,00
0,10
0,20
0,30
0,40
0,50
0,60
0,70
0,80
0 5 10 15 20 25 30 35 40 45
H (m)
T1
(s)
+ SD
- SD
27°
GN
GT
S, T
ries
t e, 6
- 8 o
ttob
re 2
008
A. M
asi,
M. V
ona
EXPERIMENTAL RESULTS
Spanish RC Buildings (Navarro et al., 2004)
The dynamic behaviour characteristics of 89 RC building structures were investigated using microtremor measurements.The measurements were performed at the top of the buildings and at the centre of plan on the roof floor or at the last story of buildings.The dominant type of construction in Granada City consists in RC frames without earthquake-resistant design, with unidirectional RC tile lintel floors and exterior hollow brick walls. The RC buildings under examination were regular both in plan and elevation.