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

مقاله انگلیسی- DAMAGE AND PLASTICITY FOR CONCRETE BEHAVIOR

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شماره فایل : 108

 مقاله انگلیسی- DYNAMIC RESPONSE CHARACTERISTIC OF REINFORCED

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شماره فایل : 106

DYNAMIC RESPONSE CHARACTERISTIC OF REINFORCED CONCRETE COLUMN SUBJECTED TO BILATERAL EARTHQUAKE GROUND MOTIONS

SUMMARY

This paper presents the dynamic response characteristics of a reinforcement concrete column subjected to bilateral earthquake ground motions. A Series of shaking table tests and fiber model analyses were conducted for 3 cross-sectional types of columns. The experimental results showed that the effect of bilateral excitation of the column was found to be significant on the non-linear response behavior of the column. Furthermore, it was found that the fiber element model analysis could simulate the experimental results well before the deterioration of the strength of the columns caused by the buckling of longitudinal reinforcement and the peeling of cover concrete.

مقاله انگلیسی- Building Damage in May 26, 2003 Miyagi-Offshore Earthquak

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Building Damage in May 26, 2003 Miyagi-Offshore Earthquake

ABSTRACT

This paper reports the damage survey on building structures at the Miyagi-Offshore

Earthquake occurred on May 26, 2003. The maximum ground acceleration recorded at the

K-net strong motion observation stations was large and its response spectrum in the shorter

period exceeds the requirement of the Seismic Building Standard, but the structural damage to buildings was observed not so severe. The reason of the phenomena was discussed.

KEYWORDS: Miyagi-Offshore Earthquake, damage survey to buildings, strong motion records, response

مقاله انگلیسی- Deformation Behavior of Fiber-Reinforced Polymer Reinf

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Deformation Behavior of Fiber-Reinforced Polymer Reinforced Engineered Cementitious Composite (ECC) Flexural Members under Reversed Cyclic Loading Conditions

This study investigates the response of fiber-reinforced polymer (FRP) reinforced engineered cementitious composite (ECC) members with a focus on their flexural load-deformation behavior, residual deflection, damage evolution, and failure mode. Critical aspects of conventional FRP-reinforced concrete members—such as interfacial bond strength, flexural crack formation, composite deformation behavior, and brittle failure mode—are briefly reviewed and compared to FRP reinforced ECC. The interaction of linear elastic FRP reinforcement and ECC matrix with ductile stress-strain behavior in tension results in nonlinear elastic flexural response characteristics with stable hysteretic behavior, small residual deflection, and ultimately gradual compression failure. Compatible deformations of reinforcement and matrix lead to low interfacial bond stress and prevent composite disintegration by bond splitting and cover spalling. Furthermore, flexural stiffness and strength as well as crack formation and widths in FRP-reinforced ECC members are found effectively independent of interfacial bond properties due to the tensile deformation characteristics of the cementitious matrix. A model for the load-deflection envelope based on a nonlinear moment-curvature relationship is suggested.

Keywords: bond; composite; deformation; reinforcement; tolerance.

104- مقاله انگلیسی- ELASTIC-PLASTIC ANALYSIS OF RC SHEAR WALL USING

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ELASTIC-PLASTIC ANALYSIS OF RC SHEAR WALL USING DISCRETE ELEMENT METHOD

Abstract:

 An analytic method of RC structure using discrete element method is introduced in this paper. The RC structures are meshed with concrete discrete elements and re-bar elements. The discrete elements are connected with “point to point” contact elements and spring elements. The damage of concrete is assumed that it only happens on the interfaces of different discrete elements. Hence, the contact estimation of traditional discrete element method is simplified and the stability and speed of calculation process is improved. The influence of crack surfaces also can be obtained in this method, which is difficult for normal finite element method. A two-limb shear wall model is analyzed using this method. The results show this method is rational and effective.

Key Words: Discrete Element, Shear Wall, Elastic-plastic Analysis

103- مقاله انگلیسی- A new approach to the confinement of RC columns

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A new approach to the confinement of R/C columns

Abstract

A new constitutive law is presented, valid for confined concrete. The transversal stresses induced by a hoop, either of square or of circular shape, in the cross section of r.c. members (columns or beams) axially loaded, are evaluated through Airy's functions relevant to plain strain states. The results, valid for square or circular hoops, are then extended to hoops of polygonal shape, with or without bindings, and to a combination of hoops of different shapes. The formulation, valid for the cross section containing the hoop, is finally extended to the overall volume of the member through the interaction among hoops and longitudinal reinforcements. The results suggested by the proposed model for members of circular and square cross section are compared with experimental data and with the results of other researchers. The proposed model, in comparison with other models, shows a better agreement with experimental results.

KEYWORDS

Reinforced concrete, confinement, ductility

101- مقاله انگلیسی-APPLICATION OF PUSHOVER ANALYSIS ON REINFORCED CONCRETE B

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APPLICATION OF PUSHOVER ANALYSIS ON REINFORCED

CONCRETE BRIDGE MODEL

Abstract

This report describes a non-linear static (pushover) analysis method for prestressed reinforced concrete structures that predicts behavior at all stages of loading, from the initial application of loads up to and beyond the collapse condition. A look insight into pushover methodology described in EC8, FEMA-273/356 and ATC-40 documents also is presented. The nonlinear static (pushover) analysis method (NSP), developed here use “line elements” approach, and are based on the degree of refinement in representing the plastic yielding effects. The elasto-plastic behavior is modeled in two types: (1) distributed plasticity model, when it is modeled accounting for spread-of-plasticity effects in sections and along the beam-column element and (2) plastic hinge, when inelastic behavior is concentrated at plastic hinge locations. Both local (P-δ) and global (P-Δ) nonlinear geometrical effects are taken into account in analysis. The method has been developed for the purpose of investigating the collapse behavior of a three span prestressed reinforced concrete bridge of 115 meters in total length that is to be built in the northeastern of Portugal over Alva River. Performance of this bridge using the nonlinear static method presented here in conjunction with iterative capacity spectrum method specified in the EC8 guidelines will be evaluated

102- مقاله انگلیسی- COUPLED GURSON PLASTICITY AND DAMAGE MODEL FOR

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COUPLED GURSON PLASTICITY AND DAMAGE MODEL FOR CONCRETE STRUCTURES IN DYNAMICSAbstract

This study deals with the aspects of the concrete behaviour under dynamic loading such as impacts or explosions. For these kinds of sollicitations concrete experiences compaction (a decrease of porosity),plastic strains in compression and also cracking in tension. It is relevant to be able to represent, at the same time, the phenomena of compaction of material, as well as the rupture by extension. Recently,new dynamic experiments performed on con[1]ned concrete (to obtain compaction), made it possible to highlight a signi[1]cant effect of the strain rate on the spherical behaviour of concrete. Following these experimental observations, a viscoplastic and visco-damage model was developed. This model is based on Perzyna viscoplasticity associates with a modi[1]ed Gurson yield function and on a visco-damage model. This constitutive model for concrete is able to represent the rate effect experimentally observed. The model presented was implemented in the [1]nite element code LS-DYNA3D. Simulations of tests carried out on structures allowed to validate the numerical implementation, as well as the model for fast dynamic loading.

Keywords: dynamics, concrete, plasticity, damage

نقشه ارومیه فایل کد و پی دی اف

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شماره فایل : 149

 نشریه 164 سازمان مدیریت- دستورالعمل هدایت هیدرولیکی خاک به روش پیزومتری

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شماره فایل : ۱۴۳

 مقاله السیور- ANALYTICAL AND EXPERIMENTAL STUDIES ON BUCKLING RESTRAINE

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شماره فایل : 99

ANALYTICAL AND EXPERIMENTAL STUDIES ON BUCKLING RESTRAINED BRACED COMPOSITE FRAMES

SUMMARY

Analytical and experimental studies on the seismic behavior of buckling restrained braced frames(BRBFs) with concrete filled steel tubular (CFT) columns are being conducted at the ATLSSCenter, Lehigh University. The objectives of these studies are to investigate the seismicperformance of this type of frame, to evaluate existing design criteria, and to calibrate analytical models. The project is sponsored by the National Science Foundation in conjunction with the U.S.-Japan Cooperative Research Program on Composite and Hybrid Structures. A 4-story prototype building was designed with buckling restrained braced frames (BRBFs) as the lateral load resisting system. The columns in this frame are CFT members and the beams are structural steel sections. Design criteria were taken from the IBC 2000 and the AISC/SEAOC Recommended Design Provisions for BRBFs. A 1-bay prototype BRBF, representing one-quarter of the lateral load resisting system in one direction, was extracted from the prototype building for analysis. The analysis program DRAIN-2DX was used to model the prototype frame including material and geometric nonlinearities. The force-deformation relationship used in the buckling restrained brace model incorporates both isotropic and kinematic hardening. Nonlinear time history analyses were conducted using an ensemble of ground motions consisting of natural earthquake records and one artificial earthquake record. The earthquake records were scaled to two different seismic input levels: Design Basis Earthquake (DBE) and Maximum Considered Earthquake (MCE). A statistical summary of the analysis results was developed at both seismic input levels. Performance objectives were defined and used to evaluate the analysis results. The life safety (LS) performance level was the target level for the DBE and the collapse prevention (CP) performance level was the target level for the MCE. Acceptable BRBF behavior was observed at both seismic input levels. A large-scale BRBF experimental investigation is planned. This paper presents the results of the analytical study and briefly summarizes the upcoming experimental program.

Keywords: Ductile design; Seismic force reduction; Hysteretic behaviour

مقاله السیور- application of the equvalent column method for fleural buc

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شماره فایل : 100

APPLICATION OF THE EQUIVALENT COLUMN METHOD FOR FLEXURAL BUCKLING ACCORDING TO THE NEW EC3-RULES

Abstract

The rules in EN 1993-1-1 provide an approach for the stability check of members and frames under axial compression and bending with the “equivalent column method”. This method is based on the use of the specific buckling length of the structure and of first order internal forces. In addition, a second approach is provided where individual members are considered like “cut-out members” of the system with end-moments including the second order sway effects. For the check of equivalent members or cut-out members the appropriate moment diagram to be used in the design formula has not been defined in the code yet. The present paper – after explaining the conceptual background of the methods – deals with the application on individual members with different boundary conditions as well as on frame systems of sway type. Comparisons of the results of the code-formulae with numerical calculations were made to illustrate the efficiency of the different methods.

KEYWORDS

Eurocode3-Part 1, flexural buckling, equivalent member, effective length method, amplified sway method, member buckling, frame analysis

98- مقاله السیور- Seismic performance of RC frames designed for three differ

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Seismic performance of RC frames designed for three different ductility levels

Abstract

The concept of “making structures ductile” has prevailed in modern earthquake-resistant building design. In this context, questions remain regarding the selection of adequate ductility levels and the corresponding seismic force reduction factor q for a specific class of structures, whereas the detailing requirements to ensure the desired ductility continue to be refined. In the current investigation, three simple frames were designed for different ductility levels according to EC8 [Eurocode 8: Design provisions for earthquake resistance of structures. CEN (European Commission for Standardisation)/TC250/SC8, 1994] and their actual performance when subjected to earthquake simulation tests are observed and compared. Results indicate that under the “ductility for seismic force reduction” trade-off scheme, the frame designed for high ductility (thus large q factor) tends to attract more extensive damage due to large yield excursion, resulting in certain performance reduction. Insufficient confinement could lead to degrade hysteretic behaviour in a rather sensitive manner. Satisfactory performance was observed in the frame designed for medium ductility where both the seismic force reduction factor and the overall ductility were in the order of 3–4. In general, the overall and local ductility demands and the q-factors were observed to correlate in a rather predictable manner.

Keywords: Ductile design; Seismic force reduction; Hysteretic behaviour

مقاله السیور- Refined force reduction factors for seismic design

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شماره فایل :97

Refined force reduction factors for seismic design

Abstract

Whereas seismic design based on deformations is a concept that is gaining ground, existing codes are fundamentally force-based, with a final check on deformations. A central feature of force-based seismic design is the response modification factor (R or q).Many studies have attempted to quantify the potential of structural systems to delimit the level of force imposed by virtue of their ductility and energy absorption capacity. This paper employs a well controlled and evenly distributed earthquake data-set (in magnitude, distance and site characterization spaces) to derive values for force reduction factors needed for the structure to reach, and not exceed, a pre-determined level of ductility. It is observed that the force modification factors are only slightly influenced by the shape of the hysteretic model used in their derivation and even less sensitive to strong motion characteristics. A linear representation is recommended for use in a benchmark for ‘demand’ considerations and given in an easy-to-use parametric form.

Keywords: Force reduction factors; Seismic design; Ductility; Design spectrum

مقاله السیور- Probabilistic evaluation of behaviour factors in EC8-d

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شماره فایل : 96

Probabilistic evaluation of behaviour factors in EC8-designed R/C Frames

A methodology for the probabilistic assessment of reinforced concrete (R/C) frames which takes into account material variability,confinement model uncertainty and the uncertainty in local and global failure criteria is applied for the derivation of vulnerabilitycurves for the serviceability and ultimate limit states of a multi-storey frame designed to Eurocode 8. By combining the uncertaintiesaffecting structural vulnerability and seismic hazard, the seismic reliability is quantified in terms of the probability of failure forany given design life period. It is found that, while adequate safety margins exist for the ULS, the reliability against the SLS strongly depends on the structural criterion adopted for the definition of this state. The variability in the actual behaviour factor of this frame is also estimated, and the appropriateness of the EC8 specified value is assessed

Keywords: Probabilistic methods; Seismic design; R/C frames; Behaviour factors; Eurocodes