Study on Seismic Responses of Masonry Brick Infill … on Seismic Responses of Masonry Brick Infill...

IJSRD - International Journal for Scientific Research & Development| Vol. 2, Issue 09, 2014 | ISSN (online): 2321-0613

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Study on Seismic Responses of Masonry Brick Infill Walls in Slender

Structures Geo.Davis

Department of Civil Engineering

KMEA Engg College, Aluva, ErnakulamAbstract— RC framed buildings are generally designed

without considering the structural action of masonry infill

walls present. These walls are widely used as partitions and

considered as non-structural elements. But they affect both

the structural and non-structural performance of the RC

buildings during earthquakes. In this present study, the

seismic responses of brick masonry infill wall in slender

structure were studied. The assumed slender structure

havingG+10storey. There are two models are created for the

analysis such as bare frame and RC frame with masonry

infill wall. The structures modeled and analyzed by ETAB

software. Static analysis, Modal analysis and Time history

analysis are done and the results were compared. From the

results has been established that masonry brick infill walls

influence the response of RC framed structures.

Key words: Brick masonry, Brick strut, Infill frame, bare

frame, Seismic analysis

I. INTRODUCTION

In the analysis of earthquake frames without masonry brick

infill wall is considered in most of the study. The purpose of

present study is to evaluate the seismic influence of masonry

brick infill walls on the RC framed structures.

While building collapse is the primary cause of loss

of life in most earthquakes, other contributors to earthquake

loss include equipment and contents damage, business

interruption, and damage to lifelines, such as water, power,

gas, communications, and transportation.

To limit these losses to acceptable levels,

earthquake engineering involves a process of

Seismic hazard identification,

Structural analysis, design, and retrofitting to

prevent structural collapse,

Reduce property damage, and

Review of equipment and operations to prevent

disruption due to earthquakes that is, an integrated,

comprehensive program of facility seismic review,

analysis, retrofit, emergency planning, and risk

transfer, involving the expertise of mechanical

engineers, operations specialists, emergency

planners, and insurers, in addition to geoscientists

and structural engineers.

In fact the presence of infill wall changes the

behavior of truss action, thus changing the lateral load

transfer mechanism. The frame with unreinforced masonry

walls can be modeled as equivalent braced frames, braced

frame with infill walls replaced by equivalent diagonal strut.

A. Effect of Infill Wall in RC Frame

A great majority of reinforced concrete (RC) structures were

severely damaged or collapsed during ground motions.

Thousands of people died after recent earthquakes. The

main reasons of these losses originate from the fact that the

average of the structures is not well engineered and also

some of them are constructed illegally.

Besides the mentioned cases, existing structures

still have similar deficiencies for future hazardous

earthquake loads. Reliable strengthening methodologies and

rehabilitation procedures should be established as quickly as

possible to minimize the expected loss in the future.

Different strengthening methods (addition of shear

walls, pre-cast panels, steel bracing, concrete jacketing of

frames, etc.) have been used. Among these techniques,

addition of RC shear (infill) walls was found practical and

economical. RC infill frame increases the lateral load

capacity of the RC frame and reduces the lateral

displacement (drift) at ultimate load.

However, the construction work for these

applications lengthens the retrofit time and occupants of the

rehabilitated buildings have to be relocated. Reconstruction

may disturb the ongoing building facilities and new

structural elements may affect the architectural aesthetics of

the structures. These restorations may add considerable

mass and cause high seismic (lateral) loads during an

earthquake. And also, altering the dimension of the RC

frame leads to take more loads of the RC frame members. In

order to overcome these deficiencies, new alternative retrofit

strategies are needed. Infill walls are commonly used in low

and mid-rise constructions. They are generally used as

interior partitions or exterior walls in buildings.

Partition walls are usually treated as non-structural

elements and often ignored in design. Recent studies have

shown that infill RC frames can be superior to a bare RC

frame in terms of stiffness, ductility and energy dissipation.

By recent improvements in polymer composite

technology; the infill walls can be strengthened and

retrofitted with fiber reinforced polymers (FRP). FRP brings

logical solutions because of their small thickness, ease of

application and advantage of high strength. Moreover, the

strength and stiffness of a structure can be increased with

little mass. Nevertheless, use of fiber reinforced polymers is

limited due to economic factors, lack of standards and some

doubts of serviceability life.

As a matter of fact, it is known that most of the

people live in inadequate economic conditions. Thus, the

usage of fiber reinforced polymers (FRP), as being a reliable

strengthening method, may not be an option to most of the

home owners, simply because of its high cost. Assessment

of strengthening the large number of infill walls could be

economical and would be superior to other techniques. If

confinement location and detailing are standard this system

has performed excellently under very intense earthquakes.

But severe damage was observed when confinement

detailing was substandard. For such cases, wall jacketing is

one rehabilitation technique suitable for improving its lateral

strength and stiffness. Jacketed specimens showed uniform

distribution of cracks and increased strength was seen

compared to the bare frames.

To achieve any benefit from wall jacketing, careful

and detailed installation of fasteners should be applied. Steel

Study on Seismic Responses of Masonry Brick Infill Walls in Slender Structures

(IJSRD/Vol. 2/Issue 09/2014/197)


nails were used to fasten the steel wire mesh. Fasteners were

placed at the grid intersections of the wire mesh. They were

placed by hammering them into the wall. The nail head was

bent at the wire intersection to secure the mesh in position.

Spacers metal washers used between the wall and the mesh

according to fastening technique Infill-frames have been

used in many parts of the world over a long time. In these

structures, exterior masonry walls and interior partitions,

usually regarded as nonstructural architectural elements, are

built as an infill between the frame members.

However, the usual practice in the structural design

of infill-frames is to ignore the structural interaction

between the frame and infill. This implies that the infill has

no influence on the structural behaviour of the building

except for its mass. This would be appropriate if the frame

and infill panel were separated by providing a sufficient gap

between them. However, gaps are not usually specified and

the actual behaviour of infill frames observed during past

earthquakes shows that their response is sometimes wrongly

predicted.

Infill-frames have often demonstrated good

earthquake-resistant behaviour, at least for serviceability

level earthquakes in which the masonry infill can provide

enhanced stiffness and strength. It is expected that this

structural system will continue to be used in many countries

because the masonry infill panels are often cost-effective

and suitable for temperature and sound insulation purposes.

Hence, further investigation of the actual behaviour of these

frames is warranted, with a goal towards developing a

displacement-based approach to their design.

Different local materials are used to produce

masonry units with different shapes; they might be solid or

hollow units with different hole-sizes and whole

arrangements. The structural behaviour of an infill-frame

can be divided into two parts, in-plane and out-of-plane. The

simultaneous effect of in-plane and out-of-plane loading has

usually been ignored in the research conducted to date,

although in actual earthquakes this effect will usually be

present.

Predominant Truss Action in Infill Frame

Frame Action in Bare Frame

Fig. 1: Effect of Infill Wall in RC Frame

B. Objectives

To rusticated the effect of masonry brick infill walls in RC

framed structures of seismic response

To familiarization of software ETABS

To compare the response of bare frame and

masonry brick in filled structures

C. Methodology

Methodology employed is FEM analysis. Modeling of the

G+10 storey reinforced concrete frame and frame with

masonry brick infill walls done using ETABS and Modal

analysis, Static analysis and Time history analysis carried

out and results are compared.

D. Finite Element Analysis

The Finite Element Analysis (FEA) is a numerical method

for solving problems of engineering and mathematical.

Useful for problems with complicated geometries, loadings,

and material properties where analytical solutions cannot be

obtained. In this method model body divided in to smaller

elements and analyzed.

E. Details of Structure

F. Calculation of Strut

II. MODELLING

The structure is modeled by using ETAB software. Two

models are created bare frame and RC frame with masonry

brick in filled walls




Fig. 2: Plan View

Fig. 3: Bare Frame

Fig. 4: RC frame with brick masonry infill wall

III. ANALYSIS ANS RESULTS

The modeled structures are modeled and analyzed. Static

analysis, Modal analysis and Time history analysis was done

by using ETABS

A. Static Analysis

The Static Analysis was performed for the two models. The

comparative results of storey displacement, storey drift and

storey shear are tabulated as follows.

1) Maximum Storey Displacement

Bare Frame Brick infilled frame

Fig. 5: Storey Displacements

STOREY

LEVEL

BARE

FRAME

BRICK

INFILLED

Storey 11 17.4 7.2

Storey 10 16.7 6.8

Storey 9 15.8 6.4

Storey 8 14.6 6.0

Storey 7 13.2 5.5

Storey 6 11.7 5.0

Storey 5 10.1 4.5

Storey 4 8.5 4.0

Storey 3 6.8 3.6

Storey 2 5.1 3.2

Storey 1 3.1 2.6

Base 0 0

Table 1: Maximum storey displacement

Fig. 6: Comparison of values in graph




2) Storey Drift

Bare Frame Brick Infilled Frame

Fig. 7: Storey Drift

STOREY

LEVEL

BARE

FRAME

BRICK

INFILLED

Storey 11 0.16 0.1

Storey 10 0.21 0.12

Storey 9 0.33 0.12

Storey 8 0.42 0.14

Storey 7 0.53 0.15

Storey 6 0.62 0.15

Storey 5 0.70 0.18

Storey 4 0.78 0.18

Storey 3 0.80 0.18

Storey 2 0.95 0.25

Storey 1 1.8 4.1

Base 0 0

Table 2: Storey drift


3) Storey Shear


Fig. 9: Storey Shears-Masonry

STOREY

LEVEL

BARE

FRAME

BRICK

IFILLED

Storey 11 110 200

Storey 10 220 400

Storey 9 325 630

Storey 8 420 870

Storey 7 515 1100

Storey 6 610 1300

Storey 5 680 1500

Storey 4 750 1700

Storey 3 800 1900

Storey 2 855 2100

Storey 1 875 2250

Base 0 0

Table 3: Storey shear





B. Modal Analysis

The Modal analysis was performed to two models and we

getting the periods of the structure

Fig. 11: Modal-5Bare Frame, Modal-5 Brick infilled Frame

Period-0.425 Period-0.937

C. Dynamic Analysis (Time History Analysis)

The time history analysis technique represents the most

sophisticated method of dynamic analysis for buildings. I

this method the mathematical model of the building is

subjected to accelerations from earthquake records. This

method consists of a step by step direct integration over a

time interval; the equations of motion are solved with the

displacements, velocities and accelerations.

1) Acceleration


Fig. 12: Acceleration

TIME BARE

FRAME

BRICK

INFILLED

1 30.0 15.5

2 29.0 10.0

3 19.0 5.9

4 11.0 3.0

5 6.5 3.0

6 6.0 2.8

7 3.0 2.0

8 3.0 1.0

9 3.0 1.0

10 3.1 1.0

Table 4:.Acceleration


2) Velocity


Fig. 14: Velocity

TIME BARE

FRAME

BRICK

INFILLED

1 8 2.1

2 5.5 1.25

3 3.2 0.68




4 1.9 0.49

5 1.7 0.45

6 1.0 0.40

7 0.8 0.22

8 0.8 0.20

9 0.8 0.20

10 0.9 0.20

Table 5: Velocity


3) Displacement


Fig. 16: Displacement

TIME BARE

FRAME

BRICK

INFILLED

1 1.4 0.20

2 1.1 0.14

3 0.6 0.08

4 0.3 0.07

5 0.2 0.06

6 0.1 0.05

7 0.2 0.03

8 0.2 0.02

9 0.2 0.02

10 0.3 0.02

Table 6:.Displacement


IV. SUMMARY AND CONCLUSION

1) Investigated the effect of Masonry Brick Infill

Walls in seismic response of structure

2) Familiarized the software

3) Compared the results and find out Masonry Brick

Infill Frames having good response to earthquake

4) From Modal analysis Period of masonry brick infill

wall frame greater than bare frame

5) It can be concluded that brick infill walls is to be

included and carrying out seismic analysis of

multistoried frames

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