SEISMIC RESPONSE DIAGNOSIS ON MASONRY HOUSING
USING EXPERIMENTAL MODELS ON AN SCREANING METHOD
Carlos Zavala (1)Patricia Gibu (2)Rafael Salinas (2)Abstract
In the evaluation of the seismic vulnerability on towns and cities, the seismic response
diagnosis of masonry buildings could be reduced approximately on the basis of thegeometry of the structural system obtained during a screening inspection. In this report asimplified method for evaluation is presented, which takes into account an equivalent
one degree of freedom system and uses behavior curves from actual tests performed at
Structural Laboratory on CISMID/FIC/UNI. The curves were reduced to non-linear
models with parameters proposed herein. This model used different seismic demands,
regarding the maximum peak ground acceleration (PGA) and the wall density on thestructure as main variables. As a result a series of seismic response curves weregenerated for its use as a simple tool for screening evaluation.
Introduction
The evaluation of seismic vulnerability on buildings can be developed as a deterministic
problem if we consider the geometric characteristics, material, reinforcement, soil
characteristics and quake demand. However, on the evaluation of seismic vulnerability of
1000, 5000 o 10000 buildings, it means the evaluation of global seismic vulnerability of acity, the application of a deterministic method became time consuming and costly. For
this reason, the called screening evaluation methods based on a fast evaluation or visualevaluation become an alternative for the evaluation of an area with high density ofbuildings. These methods used evaluation checklist, field surveys, database and othertools to produce a diagnosis of the seismic response of big amount of buildings. Anapproximated method for evaluation of the seismic response was presented on the studyof the seismic vulnerability of housing on La Molina district, Lima [1], where the natural
period of the structural system was used as parameter, as a function of the structural
type and height of the building.
In this report a simple method for evaluation of the seismic response of masonrybuildings based on the wall density and seismic demand is presented. The method isbased on non-linear behavior curves obtained in 18 years of wall tests performed at the(1) Associated Professor CISMID/FIC/UNI czavala@uni.edu.pe(2) Auxiliary Professor CISMID/FIC/UNI pgibu@uni.edu.pe, rsalinas@uni.edu.pe

Structural Laboratory of CISMID/FIC/UNI.
Experimental models
In the evaluation of the seismic response of masonry walls, sophisticated models of finite
elements (micro models) and simple models based on strut (macro models) canrepresent the global characteristics of a wall. A comparison of both alternatives waspresented on [2], where it is showed that, for maximum values, the application of a macromodel does not lead to a wrong response of the structural system.
Using the experimental data of wall tests [3], [4], [5] y [6] performed on full scale at theStructural Laboratory on CISMID/FIC/UNI, a database of different types of wall, which
represents diverse variables such as confinement, concrete quality, brick arrangement
and type of joint was generated. From this data, testing walls were classified on 13 types
presented on Table 1.

Table 1: Types of walls considered in the diagnosis
TipoJunta1Endentado
2
Endentado
3
Endentado
4
Endentado
5
Sin Endentar
6
Endentado
7
Endentado
8
Endentado
9
Endentado
10
Endentado
11
Endentado
12
Endentado
13
Endentado

AparejoCabeza
Soga
Soga
Soga
Soga
Soga
Soga
Soga
Soga
Soga
Soga
Soga
Soga

Refuerzo
4 Φ 1/2
4 Φ 1/2
4 Φ 1/2
4 Φ 3/8
4 Φ 3/8
4 Φ 3/8
4 Φ 3/8
4 Φ 3/8
4 Φ 3/8
4 Φ 1/2
4 Φ 3/8
4 Φ 3/8
4 Φ 3/8

Calidad Espesor Longitud Altura Esbeltez
Artesanal
0.20
2.65 2.30
0.87
Artesanal
0.12
2.40 2.30
0.96
Industrial0.13
2.40 2.30
0.96
Industrial
0.12
2.40 2.30
0.96
Industrial
0.12
2.40 2.30
0.96
Industrial
0.12
1.80 2.40
1.33
Industrial
0.12
2.40 2.40
1.00
Industrial
0.12
3.60 2.40
0.67
Industrial
0.12
2.40 2.20
0.92
Industrial
0.12
2.40 2.20
0.92
Industrial
0.12
2.40 2.20
0.92
Industrial
0.12
2.40 2.20
0.92
Industrial
0.12
2.40 2.20
0.92

K1(t/m)
15517.33
7768.40
14707.00
9433.037752.503880.905310.557894.05
3932.404341.964482.205499.00
5017.57

K2(t/m)471.97425.90486.30488.27737.50132.10237.20384.7545.69
0.00
147.89335.2757.65

Vmax (t)
17.74
9.50
19.13
17.40
16.65
11.37
17.40
23.56
22.41
13.86
22.15
22.21
21.07

A bilinear model was generated from each of the behavior curves of the testing walls andtype of wall. Figure 1 presents the generated curve (reference [6]) where the behavior
curve is adjusted as bilinear curve.
MURO DE ALBAÑILERÍA CONFINADA EML-1

CORTANTE (Ton)

30.0
20.0
10.0
0.0
-30.0

-20.0

-10.0

-10.0

0.0

10.0

20.030.0

-20.0
-30.0

DESPLAZAMIENTO (mm)(1) Associated Professor CISMID/FIC/UNI czavala@uni.edu.pe(2) Auxiliary Professor CISMID/FIC/UNI pgibu@uni.edu.pe, rsalinas@uni.edu.pe

Figure 1: Bilinear model from testing wall [6]From these models a value of stiffness and initial diagonal cracking is found. As anexample, on Figure 1 the elastic stiffness of 5017 ton/m, post-initial diagonal cracking
stiffness of 57 ton/m with initial diagonal cracking load level of 21 ton, were found.
Each type of wall has its own elastic stiffness, post-initial diagonal cracking stiffness andshear level for initial diagonal cracking. These values represent the behavior of eachtype of masonry wall.
Diagnosis of the seismic Response
For the diagnosis of the seismic response a representative selection of Peruvian quakes
were used, as Lima 17/10/1966, Huaraz 31/5/1970, Lima 3/10/1974, Nazca 12/11/1996,
Atico 23/6/2001. The characteristics of Peruvian quakes are the high frequency content
on the record.
For the evaluation of the stiffness on masonry building, the area of wall per unit of area,commonly named wall density, was taken as main variable. According with thecharacteristics of walls, the user can choose a wall type, from the experimental database,which represents the walls on the structure.
The number of stories of the building is considered as additional variable for each type ofwall. If first mode is considering as representative of the response of the structure, it ispossible the evaluation of an equivalent system using a one degree of freedom system,
using uncoupled equations of motions and equivalent mass, stiffness and force on thesystem.
Then different allowable software for analysis of one degree of freedom systems as
Nonlin, WaveAna, o Single, can be used for the evaluation of the non-linear seismic
response on the structure.
The demand must be considered incremental, in order to evaluate the drift on the modelfor different demands. Then, a number of seismic responses for structures with different
wall density like 2%, 4%, 6% y 8% with PGA of 100, 200, 300, 400 y 500 gals and each of
the selected quakes were developed.
Figures 2, 3, 4 and 5 present the results of multiple seismic responses on models for 1 to
5 story buildings. As examples, the results on wall type 1 and wall type 3 are presented,
where the parameter material is different. Here type 1 wall represents hand-made brickstructure and type 3 wall represents an industrial-made brick structure.

(1) Associated Professor CISMID/FIC/UNI czavala@uni.edu.pe(2) Auxiliary Professor CISMID/FIC/UNI pgibu@uni.edu.pe, rsalinas@uni.edu.pe

Densidad 2%
Industrial

Densidad 2%
Artesanal

0.007

0.007
0.006

0.006
1 piso0.004

2 pisos

0.003

3 pisos
4 pisos

0.002

DriftMax

DriftMax

0.005

1 piso0.004

2 pisos

0.003

3 pisos
4 pisos

0.002

5 pisos

0.001

0.005

5 pisos

0.001

000100

200

300

400

500

600

0100

200

PGA

300

400

500

600

PGA

Figure 2: Responses for 2% wall density
Densidad 4%
Artesanal

Densidad 4%
Industrial

0.006

0.006
0.005
1 piso0.004

2 pisos
3 pisos

0.003

4 pisos

0.002

DriftMax

DriftMax

0.005

2 pisos

0.004

3 pisos

0.003

4 pisos

0.002

5 pisos

5 pisos
0.001

0.001

000

100

200300400

500

600

0100

200

PGA

300

400

500

600

PGA

Figure 3: Responses for 4% wall density
Densidad 6%
Industrial

Densidad 6%
Artesanal
0.005

0.005

0.004

0.004

2 pisos

3 pisos
4 pisos

0.002

5 pisos

DriftMax

DriftMax2 pisos
0.003

0.003

3 pisos
4 pisos

0.002

5 pisos
0.001

0.001
00

0

100

200

300

400

500

600

0100

200

PGA

300

400

500

600

PGA

Figure 4: Responses for 6% wall density
Densidad 8%
Artesanal

Densidad 8%
Industrial

0.005

0.005

0.004

0.004

3 pisos
4 pisos

0.002

5 pisos0.001

2 pisos
DriftMax

DriftMax2 pisos
0.003

0.003

3 pisos
4 pisos

0.002

5 pisos
0.001

000100200300PGA

400500600

0100200300

400500600

PGAFigure 5: Responses for 8% wall density
From the figures it is possible to observe that the more wall density is, the smaller theseismic response, on structures built both with industrial or handmade brick. However,these responses are bigger on handmade brick structures, because the stiffness and the(1) Associated Professor CISMID/FIC/UNI czavala@uni.edu.pe(2) Auxiliary Professor CISMID/FIC/UNI pgibu@uni.edu.pe, rsalinas@uni.edu.peshear resistance of the handmade structures are smaller than those of the industrial
made structures.
AGREEMENT CISMID/UNI - MUNICIPALITY OF LA MOLINASEISMIC VULNERABILITY OF LA MOLINA DISTRICTLOCATION ......................................................................................................................................
BLOCK.......................... HOUSE:.................................
SKETCHTYPE OF BUILDING:
One family house ( )Multifamily home(Comercial (Public ())

Home & bussiness ()Private ())

CHARACTERISTICS:
Independent ()Passage (Dpt. on building ()Other)

Share ()...........................................................

OWNER:Own ()

Rental ()TIME FROM BUILT.......................... Years

NUMBER OF PERSONS:...............................................

OCCUPATION
Professional ()Technitian (AREA OF THE LAND .................... X .....................
AREA BUILT ...................X ....................

)

Business ()

None

()

= ....................m2= .................... m2

NUMER OF STORIES .............................

UNDERGROUND :YES (NO()

No .............................

)STORY HEIGHT ...........................
HALF UNDERGROUNDTOTAL HEIGHT()............................… mt.

MAIN CONSTRUCTION MATERIAL :Adobe ()

Masonry (ADOBEFOOTING
Stine and mud ()Reinforce Concrete ()Other..............…………..................

MASONRY

Stone and Cement (Other ..........................................
STATE OF CONSERVATIONGood ( )Regular( )Bad( )
No settlements( )With settlements ( )ADOBE
ROOF SYSTEM
Wood()
Cain ())

Mud ()FOOTING
Beam without reinforce ()Other ........................………………........
STATE OF CONSERVATIONGood ( )Regular( )Bad( )
No settlements( )With settlements ( )MASONRY
ROOF SYSTEM
Concrete Slab ()Light slab (REINFORCE CONCRETE
FOOTING
Isolate ( ) Conected ( )) Beam with reinforce ( )Other ..…………...............................
STATE OF CONSERVATIONGood ( )Regular( )Bad( )
No settlements( )With settlements ( )REINFORCE CONCRETE
ROOF SYSTEM
Concrete slab ()Light slab()
Other: ....................................

)

Other: ....................................

Other: ....................................

STATE OF WALLSGOOD()
REGULAR ()BAD()
WITH COVERING()WITHOUR COVERING ()COMENTARY..........................................................

STATE OF WALLSGOOD()REGULAR ()BAD()
WITH COVERING()WITHOUR COVERING ()COMENTARY..........................................................

ELEMENTS :COLUMNS()WITHOUT CRACKS ()WITH CRACKS()COMENTARY....................................

................................................................................

................................................................................

………………………………………..

REINFORCE ON WALLSVERTICAL AND/ OR HORIZONTAL REINFORCE
IN WALLS
YES ()NO ()BEAMS : ........................
WITHOUT CRACKS ()WITH CRACKS()COMENTARY....................................

COMENTARY ......................................................

IF ANSWER IS POSITIVE FILL THE FOLLOWING:CONCRETE WALLS: ...............

..............................................................................

ONLY
COLUMNSWITHOUT CRACKS ()WITH CRACKS()COMENTARY....................................

YES
NO (())(ONLY
BEAMS)()BEAMS AND (COLUMS)

WITH REINFORCE (INSIDE THE BLOCKSCOMENTARY :...................................................

)...................................................................................

Figure 6: Survey evaluation checklist format
How to use these graphs
The graphs can be used for the diagnosis of the seismic response of masonry. Firstly,identify the type of masonry using Table 1. A field survey is required to assess theclassification and state of the building. This format will also record the physical andmaterial characteristics of the structural system, such as number of stories and wall
(1) Associated Professor CISMID/FIC/UNI czavala@uni.edu.pe(2) Auxiliary Professor CISMID/FIC/UNI pgibu@uni.edu.pe, rsalinas@uni.edu.pedensity. Then considering the number of stories, wall density and probable demand on
the location (maximum PGA) the response can be computed. By the consideration ofthese factors, it is possible to evaluate the maximum building drift for the demand quake.
If the diagnostic drift is bigger than the drift threshold of the seismic standards, thestructure will be considered vulnerable. If the diagnostic drift is lower than the seismicstandards threshold, the structure will be considered to resist the quake without
structural problems for the demand quake.
Final CommentaryThis report shows the first steps in the development of a method for evaluation of seismic
response of buildings, both in urban or rural area. We consider our experimental
background to shear the behavior curves and maximum threshold for each type of wall.
However there are many influences we continue studying such as the influence of axial
loads, overturning moments and other external factors. The authors consider thismethodology a diagnosis proposal for screening evaluation. We want to provide in near
future a second version of the method with the consideration of the drift thresholds
proposed on [4] to evaluate the damage by the quake demand.
Acknowledgements
The authors wants to express our gratitude to our students Ms. Jenny Taira, Mr.
Francisco Lima, Mr. Bruno Adriano and Mr. Jorge Salinas, who help us in therecompilation of data and the generation of the data base used for this report.
References[1] C. Zavala, S. Alarcón, F. Ríos, C. Honma , Vulnerabilidad Sísmica de Viviendas delDistrito de la Molina, Reporte CISMID/FIC/UNI Octubre 2004
[2] C. Zavala, R. Torres, J. Gallardo, Aseismic Masonry Building Model, Proceedings of
the Structural Engineering World Conference, San Francisco USA, 1998.
[3] Gibu P. , Serida C., Muros de albañilería confinada sujetos a carga lateral,
Universidad Nacional de Ingeniería, FIC/UNI, 1993.
[4] Zavala C., P.Gibu, C. Honma, R. Salinas, Construction Monitoring And Improvement
Techniques For Masonry Housing / CISMID/FIC/UNI - Research Report CISMID-IDI
Project– June 2003.
[5] Ramirez O., Comportamiento teórico experimental no lineal en muros de albañilería
confinada, Universidad Nacional de Ingeniería, FIC/UNI, 1993.
[6] Delgadillo J., Estudio Experimental y analítico de muros de albañilería confinada
sujetos a cargas estáticas, Universidad Nacional de Ingeniería, FIC/UNI, 1994
(1) Associated Professor CISMID/FIC/UNI czavala@uni.edu.pe(2) Auxiliary Professor CISMID/FIC/UNI pgibu@uni.edu.pe, rsalinas@uni.edu.pe