In this paper a new method for NONLINEAR ANALYSIS of three dimensional REINFORCED CONCRETE FRAMES (3D-RCF) under cyclic and monotonic loading is proposed. Each REINFORCED CONCRETE frame is divided into two types of joint and beam-column elements. The effect of bond-slip has been considered in the formulation of beam-column element. The effect of biaxial flexure and axial load on the cross section is assumed for NONLINEAR behavior while the effect of tensional behavior of beam-column element is assumed linear. The pull-out effect of reinforcing bar is considered in the formulation of joint elements. Formulation and relevant equations are displacement based upon which a computer program is developed. The reliability of the method has been assessed through the comparison of numerical and an experimental result by achieving of excellent agreement. Also the effect of bond-slip and bar pull-out occurring at joint on the response of RC FRAMES is evaluated by utilizing various analyses.

In this article, a numerical model based on the layer approach is introduced for NONLINEAR cyclic ANALYSIS of two-dimensional REINFORCED CONCRETE FRAMES. The advantage of the proposed analytical procedure is that it takes the bond-slip, shear-slip and pull-out effects and, also, shears deformation in the joints into account. Bar and CONCRETE stress-strain relations, the bond stress-slip relation and the shear stress-strain relation and, also, their cyclic behaviors are adopted as known specifications. In the modeling, each frame is divided into two types of joint element and beam-column element. The effect of bond-slip has been considered in the formulation of a beam-column element by replacing the perfect bond assumption from the fiber ANALYSIS method. Joint elements are formulated upon major behaviors including the pull-out of embedded longitudinal bars, shear and flexural deformation of joint panels and shear slip in interface sections between joints and neighboring elements. The reliability of the method has been assessed through a comparison of numerical and experimental results for a variety of specimens tested under cyclic loading. A good agreement between experimental and analytical results is obtained for both cases of strength and stiffness during the ANALYSIS.

This paper presents a force (flexibility) based formulation for NONLINEAR static ANALYSIS of REINFORCED CONCRETE plane FRAMES. NONLINEAR behavior of CONCRETE and steel fibers based on a simple one-dimensional constitutive law is considered. Navier- Bernoulli theory is accepted in different sections and the effect of bond-slip is, thus, neglected. The section flexibility and stiffness matrices are extracted by direct integration of tangential modulus of materials all over the sections. Flexibility, stiffness and residual force vector of elements are estimated, using principle of virtual work and based on a force (flexibility) formulation. An iterative algorithm used to satisfy the proposed convergence criterion. Presented samples show accuracy and efficiency of the proposed method in contrast to other existing numerical and experimental results.    

In the conventional design and ANALYSIS methods affecting parameters (loads, materials' strength, etc) are not set as probable variables. Safety factors in the current Codes and Standards are usually obtained on the basis of judgment and experience, which may be improper or uneconomical. In technical literature, a method based on NONLINEAR static ANALYSIS is suggested to set Reliability Index on strength of structural systems. In this paper, a method based on NONLINEAR Dynamic ANALYSIS with rising acceleration (or Incremental Dynamic ANALYSIS) is introduced, the results of which are compared with those of the previous (Static Pushover ANALYSIS) method and two concepts namely Redundancy Strength and Redundancy Variations are proposed as an index to these impacts. The Redundancy Variation Factor and Redundancy Strength Factor indices for REINFORCED CONCRETE FRAMES with varying number of bays and stories and different ductility potentials are computed and ultimately, Reliability Index is determined using these two indices.

In this research about 450 cases of 3D shear walls are considered with different shapes and heights. L, T and H-shape walls are studied. They are NONLINEARly analyzed in Abaqus using a micro-model, i. e. the finite element modeling and ANALYSIS. A meso-modeling approach using fiber elements is also examined in Opensees. It is shown that the meso-model is both accurate enough and much faster than the micro modeling approach. To go further, a macro-model is developed in bending in which the NONLINEAR behavior is assumed to be concentrated at the base of the wall using a rotational spring. The axial force, shape of the cross section, percentage of the longitudinal reinforcement and the aspect ratio of the wall are recognized to be the main parameters defining characteristics of the rotational spring. Using regression, semi-analytical formulas are suggested for rapid determination of the momentrotation curve of the rotational spring. Comparison with micro-model and available experimental results confirm the good accuracy of the developed macro-model.

Due to several uncertainties which affect structural responses of REINFORCED CONCRETE (RC) FRAMES, it is sensibly required to apply a vulnerability ANALYSIS tool such as fragility curve. To construct an analytical fragility curve, the incremental dynamic ANALYSIS (IDA) method has been extensively used as an applicable seismic ANALYSIS tool. To employ the IDA method for constructing fragility curves of RC FRAMES, it is important to know how many records will be adequate to assess seismic risk ANALYSIS properly? Another issue is to know how many IDA steps are required for developing an accurate fitted fragility function? For this purpose, two 3D RC FRAMES called 3STRCF and 5STRCF have been NONLINEARly modeled and 200 2-componets actual records have been considered for the IDA. The results reveal that at least 15 IDA steps are required to reduce fragility function error to less than 5% and 10 IDA steps are required to yield less than 10% error. In addition, it is revealed that a selection of 100 records is completely adequate to be certain to have an accurate fragility curve. It is concluded that at least 25 records are required to decrease fragility curve error to less than 5% and 15 records to have less than 10%. The closeness of fragility curve error variation for two models and in all limit states show that these results can be generalized to other RC FRAMES.

Plastic hinge properties play a crucial role in predicting the NONLINEAR response of structural elements. The plastic hinge region of REINFORCED CONCRETE normal beams has been previously studied experimentally and analytically. The main objective of this research is to evaluate the behavior of the plastic hinge region of REINFORCED CONCRETE deep beams and its comparison with normal beams through finite element simulation. To do so, ten beams contain six deep beams, and four normal beams, under concentrated and uniformly distributed loading, are investigated. Lengths in the plastic hinge region involving curvature localization, rebar yielding, and CONCRETE crushing zones are studied. The results indicate that the curvature localization zone is not suitable for the prediction of plastic hinge length in REINFORCED CONCRETE deep beams. Based on the results it can be stated that in simply supported normal beams the CONCRETE crushing zone is focused on the middle span, but in simply supported deep beams by creating a compression strut between loading place and support, the CONCRETE crushing zone spreads along the compression trajectory. The rebar yielding zone of simply supported beams increases as the loading type is changed from the concentrated load at the middle to the uniformly distributed load.

The paper discusses a NONLINEAR ANALYSIS of 2-D REINFORCED CONCRETE FRAMES using the Macroscopic Finite Element Model (Mac.FEM). In the elastic ANALYSIS, the reference axis for calculation of the flexural rigidity (EI) is the centroid of the cross section. This axis cannot be used for the NONLINEAR ANALYSIS because of variation of the modulus of elasticity over the depth of the cross section. The paper proposes a rational reference axis for the flexural rigidity (i.e., rigidity center) using the equilibrium equation and finite element theories. The proposed reference axis is used in the NONLINEAR ANALYSIS to predict the structural behavior of REINFORCED CONCRETE FRAMES. In the ANALYSIS, a NONLINEAR stress versus strain relationship for the confined CONCRETE in compression is used to account for the effect of transverse reinforcement on the strength and ductility of structural FRAMES. Comparison of the test results with the proposed ANALYSIS shows that the Mac. FEM can accurately predict the strength and behavior of REINFORCED CONCRETE FRAMES if the confining effect of transverse reinforcement and the rigidity center are taken into account.