دانلود مقالات لاتین گرایش سازه

PREVENTION OF UNDESIRABLE STRUCTURAL ELEMENTS IN THREE DIMENSIONAL TOPOLOGY OPTIMIZATION

HASSANI B.,TAVAKOLI M.

In this paper, the topological optimization of three-dimensional structures based on optimality criteria and artificial material model is briefly reviewed and prevention of undesirable structural elements is discussed. Prevention of formation of checkerboard patterns and the finite element mesh dependency, which are the two well-known instabilities in the process of structural topology optimization, is also considered. The idea of employing the noise cleaning techniques borrowed from image processing techniques, suggested by Sigmund for plane problems [1], is here extended to three-dimensional structures. To demonstrate the efficiency and practicality of the method, especially, when employed together with the continuation method [2] and nonconforming finite elements, some illustrative examples are presented.

Keyword: topology optimization, noise cleaning, non-conforming elements
ASIAN JOURNAL OF CIVIL ENGINEERING (BUILDING AND HOUSING) January 2003; 4(1):11-21.

http://sid.ir/en/VEWSSID/J_pdf/103820030106.pdf

PREVENTION OF UNDESIRABLE STRUCTURAL ELEMENTS IN THREE DIMENSIONAL TOPOLOGY OPTIMIZATION

HASSANI B.,TAVAKOLI M.

In this paper, the topological optimization of three-dimensional structures based on optimality criteria and artificial material model is briefly reviewed and prevention of undesirable structural elements is discussed. Prevention of formation of checkerboard patterns and the finite element mesh dependency, which are the two well-known instabilities in the process of structural topology optimization, is also considered. The idea of employing the noise cleaning techniques borrowed from image processing techniques, suggested by Sigmund for plane problems [1], is here extended to three-dimensional structures. To demonstrate the efficiency and practicality of the method, especially, when employed together with the continuation method [2] and nonconforming finite elements, some illustrative examples are presented.

Keyword: topology optimization, noise cleaning, non-conforming elements
ASIAN JOURNAL OF CIVIL ENGINEERING (BUILDING AND HOUSING) January 2003; 4(1):11-21.

http://sid.ir/en/VEWSSID/J_pdf/103820030106.pdf

PUNCHING SHEAR RESISTANCE OF HIGH-STRENGTH CONCRETE SLABS
FAGHANI NOBARI H.,EJLALI R.

The use of high-strength concrete in reinforced concrete slabs is becoming popular in Australia and other countries. Current design provisions of AS3600 and other major codes throughout the world are based on empirical relationships developed from tests on low-strength concrete. In this paper, the experimental results from four research studies are used to review the existing recommendations in design codes for punching shear failure of slabs. Design codes referred in this study are AS3600 and CEB-FIP MC 90. In AS3600 the punching shear strength is expressed as proportional to fc1/2. However in CEB-FIP MC 90 punching shear strength is fc1/3 .It is shown that the present provisions assumed to be proportional to in AS3600 are applicable up to 100 MPa.

Keyword: punching shear, slabs, high-strength concrete, CEB-FIP model code, design standards
ASIAN JOURNAL OF CIVIL ENGINEERING (BUILDING AND HOUSING) January 2003; 4(1):55-63.

http://sid.ir/en/VEWSSID/J_pdf/103820030103.pdf

A STUDY OF ELASTIC BUCKLING OF MASONRY COLUMNS
BHANDARI P.K.,BENIPAL G.S.,AHMED M.*

* PBA DIVISION, SB GROUP, POST BOX –9887, JEDDAH-21423, KINGDOM OF SAUDI ARABIA

In this paper, the behavior of masonry columns under working load has been studied. The effect of cracking on compression area of column or variation of moment of inertia of column along its height has been considered. The analytical solution for the critical load and deflection of the column is presented. A numerical example is presented to illustrate the method. The proposed approach has provided more realistic behavior of the masonry columns and proved to give an optimized critical load. The implications of the proposed study on the Indian code have also been presented.

Keyword: BUCKLING, CRACKED MASONRY, ECCENTRICITY, SLENDERNESS RATIO, CRITICAL LOAD
http://sid.ir/en/VEWSSID/J_pdf/103820080501.pdf

MECHANICAL PROPERTIES AND STRESS- STRAIN BEHAVIOUR OF SELF COMPACTING CONCRETE WITH AND WITHOUT GLASS FIBRES

SURESH BABU T.*,SESHAGIRI RAO M.V.,RAMA SESHU D.

* DEPARTMENT OF CIVIL ENGINEERING, DMS SVH COLLEGE OF ENGINEERING, MACHILIPATNAM, INDIA

The development of Self Compacting Concrete marks an important milestone in improving the product quality and efficiency of the building industry. Self Compacting Concrete is a recently developed concept in which the ingredients of the concrete mix are proportioned in such a way that it can flow under its own weight to completely fill the formwork and passes through the congested reinforcement without segregation and self consolidate without any mechanical vibration. Several studies in the past have revealed the usefulness of fibres to improve the structural properties of concrete like ductility, post crack resistance, energy absorption capacity etc. Fiber reinforced self compacting concreting combines the benefits of self compacting concrete in fresh state and shows an improved performance in the hardened state due to the addition of fibers. In this investigation Cem-FIL anti-crack high dispersion glass fibres were added to self compacting concrete and Glass Fibre Reinforced Self Compacting Concrete was developed. An attempt has been made to study mechanical properties and stress-strain behaviour of self compacting concrete and glass fibre reinforced self compacting concrete. A strength based mix proportion of self compacting concrete was arrived based on Nan-Su method of mix design and the proportion was fine tuned by using Okamura’s guidelines. Five self compacting concrete mixes with different mineral admixtures like fly ash, ground granulated blast furnace slag and rice husk ash were taken for investigation with and without incorporating glass fibres. A marginal improvement in the ultimate strength was observed due to the addition of glass fibres to the self compacting concrete mix. Also incorporation of glass fibres had enhanced the ductility of self compacting concrete. Complete Stress-Strain behaviour has been presented and an empirical equation is proposed to predict the behaviour of such concrete under compression.

Keyword: SELF COMPACTING CONCRETE, FIBRE, GLASS FIBRE, FIBER REINFORCED SCC, ADMIXTURES, STRESS-STRAIN BEHAVIOR

ASIAN JOURNAL OF CIVIL ENGINEERING (BUILDING AND HOUSING) 2008; 9(5):457-472.
http://sid.ir/en/VEWSSID/J_pdf/103820080504.pdf

SENSITIVITY OF THE OPTIMUM DESIGN OF REINFORCED CONCRETE FLAT SLAB BUILDINGS TO THE UNIT COST COMPONENTS AND CHARACTERISTIC MATERIAL STRENGTHS

SAHAB M.G.*

* DEPARTMENT OF CIVIL AND ENVIRONMENTAL ENGINEERING, TAFRESH UNIVERSITY, TAFRESH. IRAN

In this paper the influence of the unit cost of steel, concrete and formwork and the characteristic strengths of steel and concrete on the optimum design of reinforced concrete flat slab buildings is investigated. Size optimization of flat slab buildings according to the British Code of Practice is carried out. The objective function is the total cost of the building including the cost of floors, columns and foundations. The total cost of the building includes the cost of material and labour for concrete, reinforcement and formwork. Excavation cost is also considered in the cost of foundations the optimization process is handled in two levels.
In the first level the optimum cross-sectional dimensions of reinforced concrete elements is determined using a hybrid algorithm based on genetic algorithm . In the second level an exhaustive search is applied to seek the optimum size and number of steel bars for each individual type of structural elements. A practical example is given to demonstrate the achieved cost saving and sensitivity of the optimum design to unit cost items and the characteristic strengths of steel and concrete.

Keyword: STRUCTURAL OPTIMIZATION, GENETIC ALGORITHM, HYBRID OPTIMIZATION ALGORITHM, FLAT SLAB BUILDINGS, SENSITIVITY OF THE OPTIMUM DESIGN
ASIAN JOURNAL OF CIVIL ENGINEERING (BUILDING AND HOUSING) 2008; 9(5):487-503.

http://sid.ir/en/VEWSSID/J_pdf/103820080508.pdf

STUDIES ON ACID RESISTANCE OF TERNARY BLENDED CONCRETE
MURTHI P.*,SIVAKUMAR V.

* KONGU ENGINEERING COLLEGE, PERUNDURAI, ERODE-638052, INDIA

This paper presents a detailed experimental investigation on the acid resistance of ternary blended concrete immersed up to 32 weeks in sulfuric acid (H2SO4) and hydrochloric acid (HCl) solutions. The results are compared with those of the control and binary blended concrete. ASTM class F fly ash was considered to develop the binary blended concrete at the replacement level of cement as 20% by weight. Then silica fume was considered to develop the ternary blended concrete and the replacement of cement in the ternary system by silica fume was suggested as 8% of total powder content by weight. The variable factors considered in this study were concrete grades (M20, M30 and M40) and curing periods (28 days and 90 days) of the concrete specimens. The parameter investigated was the time in days taken to cause 10% mass loss and strength deterioration factor of fully immersed concrete specimen in a 5% H2SO4 and 5% HCl solutions. The investigation indicated that the ternary blended concrete prepared by 20% fly ash and 8% silica fume performed better acid resistance than the ordinary plain concrete and binary blended concrete.

Keyword: BINARY BLENDED CONCRETE, TERNARY BLENDED CONCRETE, ACID RESISTANCE, MASS LOSS

ASIAN JOURNAL OF CIVIL ENGINEERING (BUILDING AND HOUSING) 2008; 9(5):473-486.

http://sid.ir/en/VEWSSID/J_pdf/103820080507.pdf

NONLINEAR PROPERTIES OF REINFORCED CONCRETE STRUCTURES
Iftekhar Anam (1) & Zebun Nessa (2)

لینک دانلود مقاله : http://persiandrive.net/568686

حجم فایل : 86 کیلو بایت در فرمت pdf

Abstract:

The importance of various nonliearities involved in the static and dynamic analyses of Reinforced Concrete structures is investigated in this paper. The nonlinearities studied here are geometric (caused by large deformations and consequent effect on the elastic properties of the structure) as well as material (due to the nonlinear stress-strain relationship of concrete and steel). In the first part of the paper, the nonlinear moment-curvature relationship of arbitrary Reinforced Concrete cross-sections is developed numerically using nonlinear stress-strain relationships for concrete and steel. The relative importance of geometric and material nonlinearity is studied for a simple 2-storied frame under static vertical load. Although the effect of material nonlinearity is more important in most of the cases studied here, the geometric nonlinearity becomes significant at higher loads. The effect of axial load on the momentcurvature relationship is studied, and the effect of typical axial loads on the flexural behavior of column is found to be significant. The shear strength of the beams and columns (obtained from empirical equations suggested in the ACI Code) prove to be very important here. Using the nonlinear sectional properties thus obtained, the nonlinear structural dynamic analyses of the building are performed subjecting the structure to seismic vibrations using nonlinear structural dynamics. Recorded ground motion data from two major earthquakes of the past; e.g., the El Centro earthquake in USA (1940) and the Kobe earthquake in Japan (1995) are used in the dynamic analyses. The results show the difference between the linear and the nonlinear structural response.

1-Assistant Professor, Department of Civil and Environmental Engineering, The University of Asia Pacific.
2- Former Student, Department of Civil and Environmental Engineering, The University of Asia Pacific.

Post by :www.ircivil.ir

منبع: http://omran84.blogfa.com/post-405.aspx

Coupled damage and plasticity modelling in transient dynamic analysis of concrete

لینک دانلود مقاله: http://persiandrive.net/397299

حجم فایل : ۵۵۲ کیلو بایت درفرمت pdf

SUMMARY

In a concrete structure subjected to an explosion, for example a concrete slab, the material is subjected to various states of stress which lead to many modes of rupture. Closer to the explosive, a state of strong hydrostatic compression is observed. This state of stress produces an irreversible compaction of the material.Away from the zone of explosion, con"nement decreases and the material undergoes compression with a state of stress, which is slightly triaxial. Finally, the compression wave can be re#ected on a free surface and becomes a tensile wave, which by interaction with the compression wave, produces scabbing. We present, in this paper, a model aimed at describing these three failure modes. It is based on visco-plasticity and rate dependent damage in which a homogenization method is used in order to include the variation of the material porosity due to compaction. The model predictions are compared with several experiments performed on the same concrete. Computations of split Hopkinson tests on con"ned concrete, a tensile test with scabbing, and an explosion on a concrete slab are presented.

KEY WORDS:
concrete; dynamics; compaction; damage; plasticity

Post by :www.ircivil.ir

منبع: http://omran84.blogfa.com/post-406.aspx