پایگاه تخصصی عمران ایران

192- مقاطع ایرانی و اروپایی etabs

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شماره فایل : 192

نرم افزار تبدیل آحاد و واحد های مهندسی

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شماره فایل : 189

نرم افزار Section Property

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191- نرم افزار طرح اختلاط ویرایش دوم

 منبع : ایران سازه

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شماره فایل: 191

مقاله السیور- FINITE ELEMENT ANALYSIS OF CONFINED CONCRETE COLUMNS

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شماره فایل : 117

FINITE ELEMENT ANALYSIS OF CONFINED CONCRETE COLUMNS

ABSTRACT

Finite element analyses of confined columns are presented. Based on a confinement dependent uniaxial concrete model, the importance of the yield strengths of the stirrups and the longitudinal reinforcement bars, the spacing of the stirrups, and the configuration of the cross-section, in combination with different load eccentricities are evaluated. It was found

that the spacing of the stirrups and the reinforcement configuration are of the greatest importance for the post-peak behavior. To achieve ductile structural behavior of highstrength

concrete columns, a higher value of the volumetric stirrup ratio is required. However, it was found that, even for concretes currently accepted by the code, a higher ratio than that corresponding to the required maximum spacing of 15f is needed to obtain the same ductility as a concrete of grade K40.

Key words:

 Confined columns, Finite element analysis, Highstrength concrete

 مقاله السیور- NONLINEAR MODELING OF RC AND SRC STRUCTURAL WALLS

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شماره فایل : 118

NONLINEAR MODELING OF RC AND SRC STRUCTURAL WALLS

ABSTRACT

Prediction of the inelastic response of RC and SRC walls and wall systems requires a reliable modeling approach that includes important material and response parameters (e.g.,confinement, slip, nonlinear shear behavior, neutral axis migration).

Although various macroscopic models have been proposed to evaluate the response of RC walls, the models are not available in commonly used analysis programs. A research project was undertaken at UCLA to investigate and to improve on an effective modeling approach for the reliable prediction of the inelastic response of RC and SRC walls that incorporates refined constitutive laws and various response parameters. The Multi-Component-in-Parallel Model is being calibrated and updated using extensive experimental data on RC and SRC walls, and will be implemented into a widely available analytical platform. The objective of this paper is to summarize the ongoing analytical project and to discuss the effectiveness and reliability of the model for RC walls. Model calibration with experimental data and investigation of model sensitivity to modeling parameters are emphasized.

 مقاله السیور- Modeling of Stress-Strain Relationships for Concrete

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شماره فایل : 119

Modeling of Stress-Strain Relationships for Concrete Damaged by Freezing and Thawing Cycles

Introduction

The irreversible tensile deformation and crack during FTC affect the mechanical properties of concrete, namely strength, stiffness, and deformation capacity of concrete [1,2]. Ideally the changes in the material properties resulting from FTC damage should therefore be considered in the stress analysis of reinforced concrete structures that have been affected by FTC. As a result development of pertinent constitutive models that recognize the effect of FTC damage is necessary. In this study, stress-strain models for FTC damaged concrete in compression and tension are presented. It is intended for both simple calculation of sectional member strength

and finite element analysis.Concrete in real structures is subjected to combined actions of FTC and mechanical loadings. As the first

stage, developing the models in the simplified condition in which the concrete is first subjected to FTC then mechanical loading were considered. This is because the most of concrete in the real structures is subjected to rather small tensile and compressive stresses in comparison with its strengths. The model for more general cases of combined actions will be studied in the next stage.

مقاله السیور- buckling of slender prismatic columns with asingle edge cr

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شماره فایل : 116

Buckling of Slender Prismatic Columns with a Single Edge Crack under Concentric Vertical Loads

Abstract:

The investigation of the stability behavior of slender columns with cracks is an important problem and _nds applications in structural, mechanical and aerospace engineering. This study investigates the buckling of slender prismatic columns with a single nonpropagating edge crack subjected to concentrated vertical loads. The transfer matrix method and fundamental solutions of intact columns (columns without any cracks) are combined for determining the buckling loads of cracked columns. The cracked section is ,modeled by a massless rotational spring whose flexibility depends on the local flexibility induced by the crack. Eigenvalue equations are obtained explicitly for columns with various end conditions, from second order determinants. Numerical examples show that the e_ects of a crack on the buckling load of a column depend on the depth and the location of the crack. As expected, buckling load decreases conspicuously as the crack depth increases. For a constant crack depth, a crack located in the section of the maximum bending moment causes the largest decrease in the buckling load. On the other hand, if the crack is located just in the inflexion point at the corresponding intact column, it has no e_ect on the buckling load. The study showed that the transfer matrix method is a simple and e_cient method with which to analyze cracked columns.

Key words:

Buckling, Stability, Slender prismatic columns, Crack.

 مقاله السیور- web buckling in the webbed castellated beams

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شماره فایل : 115

مقاله السیور- simplified concrete modeling with mat concrete damege rel

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شماره فایل : 114

مقاله السیور- Comparative Evaluation of Seismic Assessment Methodolo

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شمار ه فایل : 113

Comparative Evaluation of Seismic Assessment Methodologies Applied to a 32-Story Reinforced Concrete Office Building

ABSTRACT:

 Results of seismic damage evaluation of a tall reinforced concrete building are presented. Plastic hinge formation patterns obtained by using DRAIN-2D and IDARC computer programs for dynamic analysis

are compared. Damage indices given by IDARC are interpreted and their implications compared with those of drift ratios. Results of static push-over analysis are compared with those of inelastic dynamic time history analysis. Moreover, the result of collapse mechanism approach is compared with that of static push-over analysis. It is shown that simple collapse mechanism approach can predict the failure mode given by static push-over analysis for this building. It is concluded that drift limits in codes do not necessarily predict the degree of damage that this type of construction can sustain in severe earthquakes.

Keywords:

Damage analysis; Nonlinear analysis; Push-over analysis

مقاله السیور- IMPACT ANALYSIS OF A CONCRETE STORAGE CONTAINER

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شماره فایل : 111

IMPACT ANALYSIS OF A CONCRETE STORAGE CONTAINER

ABSTRACT:

A concrete container with impact limiters is analyzed for a 9m free drop to a rigid ground. The complete finite element model is built using MSC/PATRAN. Analysis is then carried out using DYNA3D. Results are again completely processed using MSC/PATRAN in terms of time history plots of energy, momentum and contact force; deformation of the container during impact; and stress/strain distribution in the container at different times.

مقاله السیور- DAMAGE TO FOUNDATIONS FROM EXPANSIVE SOILS

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شماره فایل : 112

 DAMAGE TO FOUNDATIONS FROM EXPANSIVE SOILS

 Expansive soils in many parts of the United States pose a significant hazard to foundations for light buildings. Swelling clays derived from residual soils can exert uplift pressures of as much as 5,500 PSF, which can do considerable damage to lightly-loaded wood-frame structures. Insurance companies pay out millions of dollars yearly to repair homes distressed by expansive soils.Expansive soils owe their characteristics to the presence of swelling clay minerals. As they get wet, the clay minerals absorb water molecules and expand; conversely, as they dry they shrink, leaving large voids in the soil. Swelling clays can control the behavior of virtually any type of soil if the percentage of clay is more than about 5 percent by weight. Soils with smectite clay minerals, such as montmorillonite, exhibit the most profound swelling properties.

Potentially expansive soils can typically be recognized in the lab by their plastic properties. Inorganic clays of high plasticity, generally those with liquid limits exceeding 50 percent and plasticity index over 30, usually have high inherent swelling capacity. Expansion of soils can also be measured in the lab directly, by immersing a remolded soil sample and measuring its volume change.

In the field, expansive clay soils can be easily recognized in the dry season by the deep cracks, in roughly polygonal patterns, in the ground surface (see Fig. 1). The zone of seasonal moisture content fluctuation can extend from three to forty feet deep (see Fig. 2). This creates cyclic shrink/swell behavior in the upper portion of the soil column, and cracks can extend to much greater depths than imagined by most engineers.

مقاله انگلیسی- Application of a Confined Concrete Model to

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شماره فایل : 109

Application of a Confined Concrete Model to Passively Confined Concrete Columns

Introduction:

Reinforced concrete bridge columns are provided with transverse confinement in the form of hoop or spirals for new structures and steel or carbon fiber composite shells for older existing structures, allowing ductile plastic hinges to form at the column ends in response to moderate to large seismic events. Concrete compressive strength and strain capacity increase with increasing confining stress, with the result that the force-displacement response and displacement ductility of the structure are often directly related to the level of confining stresses provided in the critical plastic hinge regions. In relatively simple moment-curvature analysis, the confinement level is typically calculated, prior to the analysis, based on equilibrium of the yielded transverse reinforcement against the concrete. This is a reasonable approach when the confining steel is expected to yield at an early stage, providing approximately constant pressure throughout the loading. However, if the confining pressure is expected to change significantly throughout the loading, as in the case of a concrete filled carbon fiber shell column, a more advanced methodology is required which depends on the current stress state.

 مقاله انگلیسی- Continuum Damage Mechanics for hysteresis and fatigue

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شماره فایل : 110

Continuum Damage Mechanics for hysteresis and fatigue of quasi-brittle materials and structures

SUMMARY:

For material exhibiting hysteresis such as quasi-brittle materials, it is natural to consider that hysteresis and fatigue are related to each other. One shows in the present work that damage, from the Continuum Damage Mechanics point of view, may be seen as the link between both phenomenon. One attempts hence to set up a unified modeling of hysteresis and damage. Numerical examples are given for concrete and validate the proposed model of internal sliding and friction coupled with damage. The problem of a proper phenomenological modeling of the micro-defects closure effect leading to a dissymetric tension/compression response and to stiffness recovery in compression is also adressed. Cyclic and fatigue applications are in mind but also random fatigue and seismic responses.

key words: damage, fatigue, hysteresis, concrete, unilateral conditions