Transcript advantages of masonary wall
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
Submitted by BHAWNESH KULDEEP
(2010PST120) M.Tech 3 rd Sem.
MASONARY WALL ADVANTAGES OF MASONARY WALL TYPES OF MASONARY WALLS FAILURE OF MASONARY WALLS FINITE ELEMENT METHOD ADVANTAGE RESEARCH PAPER REFERENCES
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
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
TYPES
• Stone masonary • Brick masonary • Hollow block concrete masonary • Reinforced masonary • Composite masonary REFERENCE FROM BINDRA &ARORA BOOK
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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.
90-Degree-Angle
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.
Curtain-Fall Collapse
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
Inward/Outward 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.
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)
WHY FEM ????
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.
DISCUSSION NO. : 1
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
APPROACHES
There were two main approaches that developed for the constitutive description of masonry,are following: macro-modeling micro-modeling
MACRO-MODELING MASONRY
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
MICRO-MODELING APPROACH
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.
FINITE ELEMENT MODEL 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 .
FAILURE MECHANISM
CONCLUSION
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.
DISCUSSION NO.:2
Jahangir Bakhteri et al (2004) carried out finite element modelling of structural clay brick masonry subjected to axial compression
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
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
Stress-strain curve for model with 7.5 mm mortar joint thickness
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.
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
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
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.
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