Aseminar on

MASONARY WALL : STATE OF THE ART

Submitted by-BHAWNESH KULDEEP(2010PST120)M.Tech 3rd Sem.

Guided by:-Dr . Ravindra Nagar (Prof.)Department of Structural Engg.MNIT Jaipur

Guided by:-Dr . Sandeep Chaudhary(Associate Prof.)Department of Structural Engg.MNIT Jaipur

CONTENT

MASONARY WALL ADVANTAGES OF MASONARY WALL TYPES OF MASONARY WALLS FAILURE OF MASONARY WALLS FINITE ELEMENT METHOD ADVANTAGE RESEARCH PAPER REFERENCES

INTRODUCTION The masonry walls is built of individual

blocks of materials such as stone, brick, concrete, hollow blocks, cellular concrete etc., usually in horizontal courses cemented together with some form of mortar.

REFERENCE FROM BINDRA &ARORA BOOK

ADVANTAGES OF MASONARY WALL•The use of materials such as brick and stone can increase the thermal mass of a building.•Brick typically will not require painting and so can provide a structure with reduced life-cycle costs.•Masonry is very heat resistant & thus provides good fire protection.•Masonry walls are more resistant to projectiles.•Masonry structures built in compression preferably with lime mortar can have a useful life of more than 500 years as compared to 30 to 100 for structures of steel or reinforced concrete.

•The use of materials such as brick and stone can increase the thermal mass of a building.•Brick typically will not require painting and so can provide a structure with reduced life-cycle costs.•Masonry is very heat resistant & thus provides good fire protection.•Masonry walls are more resistant to projectiles.•Masonry structures built in compression preferably with lime mortar can have a useful life of more than 500 years as compared to 30 to 100 for structures of steel or reinforced concrete.

•Stone masonary•Brick masonary•Hollow block concrete masonary•Reinforced masonary•Composite masonary

TYPES

REFERENCE FROM BINDRA &ARORA BOOK

STONE MASONARY WALL

http://www.staff.city.ac.uk/earthquakes/MasonryStone/images/StoneMasonryWallDetail.png

BRICK MASONARY WALL

http://buildipedia.com/images/masterformat/div04/20/images/042113_brickmasonry/040000_masonry-wall-07.jpg

HOLLOW BLOCK CONCRETE MASONARY WALL

http://content.answcdn.com/main/content/img/McGrawHill/atchitecture/f0184-03.png

REINFORCED MASONARY WALL

http://www.world-housing.net/uploads/101068_074_18.jpg

COMPOSITE MASONARY WALL

http://www.maconline.org/50.gif

MASONARY FAILURE There are three ways in which a masonry

building wall may collapse. The wall may fall straight out in a monolithic piece at a 90 degree angle, in a manner similar to a falling tree; the wall may crumble straight down in a so-called "curtain" fall collapse; or the wall may collapse in an inward / outward fashion, with the top falling inward and the bottom outward.

This is the most common type of masonry wall failure which occurs at fires. The wall falls straight out and the top of the collapsing wall strikes the ground, a distance equal to the height of the failing section measured from the base of the wall. A fifty-foot section of wall collapsing in a 90-degreeangle fall will cover at least fifty feet of ground with brick. Bricks and steel linters may bounce or roll out even farther.

The wall begins to lean outward at the top, separating from the other enclosing walls, and falls straight out at a 90-degree angle.

90-Degree-Angle

In this type of collapse, the exterior masonry wall drops like a falling curtain cut loose at the top. The wall crumbles and falls straight down, with bricks and mortar forming a pile on the ground near the base of the wall. The collapse of the brick veneer, brick cavity, or masonry-backed stonewall often occurs in a curtain-fall manner

Curtain-Fall Collapse

When a masonry wall becomes unstable and begins to lean inward, it does not always mean that the wall will fall inward. Firefighters operating ground streams must still maintain a safe distance between themselves and the unstable wall, for when a section of the broken wall falls inward, the lower portion of the wall may kick outward, or the upper portion may initially fall inward but then slide down and outward into the street, bottom first. Known as an inward/outward collapse.

Inward/Outward Collapse

FINITE ELEMENT METHOD

INTRODUCTION - FEM: Method for numerical solution of field

problems. FEM cuts a structure into several elements (pieces of the structure).

Then reconnects elements at “nodes” as if nodes were pins or drops of glue that hold elements together.

This process results in a set of simultaneous algebraic equations.

Number of degrees-of-freedom (DOF) Continuum: Infinite FEM: Finite (This is the origin of the name, Finite Element Method)

Non linear problems easily solved. Easy formulations allow many different types

of problems to be solved. The most attractive feature of the FEM is its

ability to handle complicated geometries (and boundaries) with relative ease

There are reasons to consider the mathematical foundation of the finite element approximation more sound, for instance, because the quality of the approximation between grid points is very good.

WHY FEM ????

Mohammed S. Mohammed(2010) carried out Finite Element Analysis of Unreinforced Masonry Walls

TYPE OF WALL-Unreinforced masonary wall

AIM-to provide efficient tools for better understanding of their complex behaviour

DISCUSSION NO. : 1

There were two main approaches that developed for the constitutive description of masonry,are following:

macro-modeling micro-modeling

APPROACHES

In macro-modeling masonry, no distinction between the individual units and joints is made, and masonry is considered as a homogeneous, isotropic, or anisotropic continum. As macro-modeling of masonry is advantageous when the global behavior of the structure is important. The influence of the mortar joints acting as planes of weakness cannot be addressed

MACRO-MODELING MASONRY

The alternative micro-modeling approach, expanded units are modeled with continuum elements, while the behavior of the mortar joints and unit-mortar interface is lumped as discontinuous line interface elements . In this research micro-modeling has been adopted in preference to the macro-model.

MICRO-MODELING APPROACH

In the finite element analysis, masonry is treated with micro-model, in which the units of brick and joints are modeled individually with different type of elements. The masonry units are modeled with smeared crack elements, which account for both tensile and compressive fracture of the units, while the mortar joints are modeled with interface element to account for the inherent planes of weakness to include all the basic types of failure mechanisms that characterize masonry.

FINITE ELEMENT MODEL APPROACH

FAILURE MECHANISM

This study presents an efficient finite element analysis technique which shows a great versatility in analysis complex discontinuities in the analysis of masonry walls structures by use of interface elements with a constitutive model entirely established on the basis of the incremental theory of plasticity to simulate the actual behavior at the interface between contacting materials. It was shown that the finite element method model was able to predict effectively the behavior of masonry structures, with both confined and unconfined masonry wall, as well as sufficiently accurate collapse load values.

CONCLUSION

Jahangir Bakhteri et al (2004) carried out finite element modelling of structural clay brick masonry subjected to axial compression

DISCUSSION NO.:2

AIM: To prove that for a normal case, where

elastic modulus of mortar, Ej, is less than elastic modulus of brick, Eb,

Increase in mortar thickness results in reduction of elastic modulus of the masonry,

And increase of elastic modulus of mortar, which leads to an increase in the elastic modulus of masonry

DIMENSIONS:- The models were assumed to be

constructed from five local clay bricks having dimensions of 212 mm × 92 mm × 66 mm (length × width × height), and each model with unique mortar joint thickness. There were five sets of models having different mortar joint thicknesses, which were 7.5, 10, 12.5, 15, and 20.0 mm.

TYPICAL MODEL SHOWING THE APPLIED LOAD AND BOUNDARY CONDITIONS

DEFORMED SHAPE OF THE MODEL WITH 7.5 MM MORTAR JOINT THICKNESS

GRAPH

Stress-strain curve for model with 7.5 mm mortar joint thickness

CONCLUSION

By increasing the mortar joint thickness, the strength of the masonry will decrease

The maximum compressive strength of models was obtained when the thickness of the mortar joint was 7.5 mm.

DISCUSSION NO.:3

Kirk Martini carried out finite element studies in the two-way out-of-plane failure of unreinforced masonry

Type of wall:- unreinforced masonry wall Dimensions:-length = 12.2 m (40 ft);

height = 6.1 m (20 ft) thickness = 0.51 m (20 in); E = 0.62 GPa (90 ksi); weight density = 15.7kN/m3 (100 pcf).

Organization of the finite element mesh for the block-interface model

Mesh Configuration and Behaviour

The panel was tested with a variety of mesh configurations to assess the fineness of the mesh required to achieve satisfactory results. load-displacement curves for three different mesh configurations; each mesh uses 10 courses composed of either 10 full blocks or 9 full blocks and two half blocks at the ends, each with four laminations.

Load-displacement curves for three different mesh configurations of the study panel

CONCLUSION Comparing the finite element results with the

yield line analysis reveals important aspects of both. First, the yield line method predicts a failure load of 1.5 kPa, somewhat lower than the finite element analyses which predict in the range of 1.6 to 1.7 kPa

This knowledge will help in interpreting patterns of damage in ancient and modern masonry structures, and in developing renovation strategies that account for the strengthening effect of two-way spanning action.

REFERENCES Mohammed S. Mohammed(2010) ,Finite Element

Analysis of Unreinforced Masonry Walls

Jahangir Bakhteri et al (2004) finite element modelling of structural clay brick masonry subjected to axial compression

Kirk Martini finite element studies in the two-way out-of-plane failure of unreinforced masonry

Bindra and arora book

Wikipedia and google images

THANK YOU…