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.

A parametric study is performed to assess the influence of the tension reinforcement index, (w=p ¦y/¦́c) , and the bending moment distribution (loading type) on the ultimate deformation characteristics of reinforced concrete (RC) beams. The analytical results for 15 simply supported beams with different amounts of tension reinforcement ratio under three different loading conditions are presented and compared with the predictions of the various formulations and the experimental data, where available. The Plastic Hinge rotation capacity increases as the loading is changed from the concentrated load at the middle to the third-point loading, and it is a maximum for the case of the uniformly distributed load. The effect of the loading type on the Plastic rotation capacity of the heavily reinforced beams is not as significant as that for the lightly reinforced beams. Based on the analytical results obtained using the nonlinear finite element method, new simple equations as a function of the tension reinforcement index, w, and the loading type are proposed. The analytical results indicate that the proposed equations can be used for analysis of ultimate capacity and the associated deformations of RC beams with sufficient accuracy.

Depending upon the severity of the earthquake, regions of inelastic deformation, or Plastic Hinges, may form in the components of reinforced concrete buildings. These components must then be replaced or retrofitted in order to restore the structural integrity of the structure to its originally intended design performance. Due to the high cost of replacement, retro t is often an efficient and viable option. For large earthquakes, the formation of Plastic Hinges in columns can lead to the buckling and rupture of longitudinal steel. Traditionally, once initial buckling occurs, columns are generally replaced, as the cost of replacing portions of bars can be prohibitive. Replacement is deemed necessary since the inelastic strain capacity of reinforcing bars is severely diminished once buckling occurs, making the structure vulnerable to collapse during the next seismic event. Past research on RC member retro t has focused on issues related to deficiencies in shear, lap splices, or confinement. Numerous techniques have been developed for retrofitting, including, steel, concrete or advanced composite jackets. These retro t techniques can also be utilized to repair elements with deficiencies exposed during seismic loading, or to retro t well designed members that have formed mild Plastic Hinges (without any signs of bar buckling). However, once buckled or ruptured bars are observed, it is assumed that repair is no longer feasible. It is the objective of this paper to challenge this assumption via relocation of the Plastic Hinge to a position where the member remained essentially elastic during the initial seismic attack. This is accomplished through the use of a knee brace. In this study, the influence of different parameters of a knee brace on the strengthening of RC frames is investigated, analytically and numerically. Also the effect of knee brace location and cross section is investigated by dynamic and pushover analysis. The results show that the proposed Hinge relocation technique is able to restore the lost strength and displacement capacity of RC members.

Three stiffness reduction functions are used, The formation of Plastic Hinge is considered in limit load. These functions cause the yielded cross section to be subtracted from the member stiffness. In the limit load, in which Plastic Hinges may form at both ends of a beam-column element, the entries of stiffness matrix reduce to zero. To consider the secondary effects, like P-δ and P-Δ, exact stability functions are used. A computer program is prepared for structure analysis. An automatic incremental-iterative procedure and Newton-Raphson iterations are used for nonlinear analysis. Also, redistribution of the forces in structure is predicted by computer program. The numerical results are compared with Plastic-zone methods and actual structural loading tests. This comparison proved that proposed functions are better than similar methods.

This paper presents the results of nonlinear finite element analysis of reinforced concrete (RC) frame structures, including the complete behavior of these systems from zero load to the ultimate load. Presented also are the details and results of a corroborative test program involving a large-scale frame model. The effects of the finite element size and tension-stiffening on the nonlinear responses of three RC frames are investigated. In addition, the program is used to carry out a "Plastic" analysis of the frame to define the mechanism of failure, the Plastic Hinge rotations, and the yielding and the Plastic Hinge lengths. The capability and accuracy of the nonlinear finite element analysis program in predicting the nonlinear response of RC frame structures is verified, along with a comparison between the analytical and the corresponding experimental results. The different behavioral aspects including cracking, yielding and ultimate loads, load-displacement and load-strain characteristics for concrete and reinforcing steel and Plastic Hinge deformations are studied. The analytical and experimental results indicate that the computed response of RC frame structures is strongly influenced by the finite element size. The finer meshes give lower values of the ultimate load and vice versa for the coarser meshes. With an increase in the number of elements, the structure is slightly more flexible than for the case for the coarse mesh idealization, and the frame tends to be less ductile. An empirical equation has been proposed to eliminate this drawback. The calculated Plastic Hinge rotations show good agreement with the experimental results. For example, the maximum deviation between the analytical and the experimental values of the Plastic Hinge rotations is approximately 13%, while the minimum deviation is 4%.

According to significant of bridges as infrastructures, and need for serviceability after earthquakes, it is necessary to design this group of structures adequately. In this way the determination of the location of nonlinear response in these structural systems is an important step to predict the performance of the system under different loading conditions. In reinforced concrete bridge piers, these nonlinear deformations generally occur over a finite Hinge length.A model of hinging behavior in reinforced concrete bridges pier will help guide, detailing and drift estimates for performance-based design. In this paper, by using experimental results that conducted on the reinforced concrete bridges piers and also applying artificial neural networks algorithm, predict the Plastic Hinge length of reinforced concrete bridges pier.The results show that the accuracy of artificial neural networks algorithm for predicting of this parameter in compare with other formulations that were proposed as for calculated error is appropriate.

In a strong earthquake, a standard reinforced concrete column may develop Plastic deformations in regions often termed as Plastic Hinge regions. A Plastic Hinge is basically a damping device that dissipates energy through the Plastic rotation of a rigid column connection, thus triggering the redistribution of bending moments. The formation of a Plastic Hinge in an RC column in the regions that experience inelastic actions depends on the characteristics of the earthquakes as well as the column details. In this paper, 462 inelastic time-history analyses have been performed to predict the nonlinear behavior of RC columns under the ground motions. The effects of axial load, height-to-depth ratio and amount of longitudinal reinforcement, as well as different characteristics of earthquakes are evaluated analytically by finite element methods and the results are compared with the corresponding experimental data. Analytical models for the columns analysed under high axial loads exhibit longer Plastic Hinges than those analysed under low axial loads. Based on the results, a simple expression is proposed to estimate Plastic Hinge length of RC columns subjected to earthquakes.

Appropriate seismic design is based on real understanding of structural behavior. This requires precise perception of structural behavior during earthquakes which will be achieved by considering various codes' criteria. In other words, an ideal seismic design is a method which directly considers non-linear behavior and designs frames in a way that they experience their maximum capacity, it means Plastic Hinges occur in frames. The Plastic Hinge locations should be far from joints between beams and columns. In this way, local instability does not occur. Actually, more accurate recognition of structural behavior during earthquakes is the main issue of this research. For this purpose, regular steel- moment frames with medium ductility and height were designed based on resistance (force), direct displacement, energy and Plastic Hinge methods. All the models were developed in OpenSees computer program, and they were analyzed through non-linear time history. Three records, according to record magnitude, fault distance, and soil type, were used from Pacific Earthquake Engineering Research Center (PEER) (Kobe, Northridge, and Tabas). Ultimately, these records were coordinated based on Iranian Standard No. 2800. Then, frames were evaluated with various codes' criteria in order to represent a new formula for maximum roof allowed displacement (for the purpose of controlling structural behavior after design).This formula is based on maximum displacement that frames have experienced during different earthquake records in non-linear time history analysis. The result indicates that the new formula allows more displacement to structures in comparison to Iranian Standard No. 2800. According to displacement time history of designed frames, at the beginning of the earthquake, the structures experienced severe impact and their nonlinear behavior was started. The transient displacement occurred when the first impact was applied to structure, and it was a displacement which happened along with the first Plastic Hinge occurrence. It makes sudden shock in displacement time history curve. With the passage of time, structures experienced variable displacements, and finally, a permanent displacement remained which is for the sake of nonlinear analyzing. Also, it can be inferred from the results that direct displacement and force methods present maximum and minimum base shears, respectively. In addition, in all frames, Plastic Hinge method provides maximum period value in comparison to other methods. It reveals that those frames which have been designed with Plastic Hinge method are more flexible. According to the results, the difference between direct displacement and energy methods period values is low, and period value of energy method is the minimum, as well.

In reinforced concrete moment frames, the Plastic Hinge regions of concrete beams provide most of the demanded deformations of the structure. That is why there are always strict rules regarding the distance between transverse reinforcements in different seismic design regulations, which makes them difficult to implement in the construction process. In the Plastic Hinge regions of the concrete beams with high heights, the main rebars with low diameter are prone to buckling under the effect of a low number of cyclic loads, which we know as low cycle fatigue. In this study, we introduced a new system to prevent the buckling of longitudinal reinforcements in the Plastic Hinges. Experimental and numerical studies were conducted on full-scale specimens with cyclic loading. The new system employs two bent steel sheets to prevent the buckling of longitudinal reinforcements and to improve the lateral restraint and ductility of the Plastic Hinge by confining the concrete core of the beam. The laboratory samples were two 5-meter specimens. Unlike the first sample, the second one used the anti-buckling system of the perforated sheet. The showed that the steel plate prevented the longitudinal reinforcement from buckling outward in the Plastic Hinges. The numerical models were analyzed using finite element software LS-Dyna, which confirmed the positive performance of this system.

Purpose: To evaluate the effect of corneal flap Hinge position on dry eye after Laser in Situ Keratomileusis (LASIK). Setting: Aban Eye Clinic, Isfahan, Iran.Methods: In a prospective double masked randomized controlled clinical trial, 212 consecutive eyes of 106 myopic patients underwent LASIK; in each patient one eye was randomly assigned for superior Hinge and the other eye for nasal Hinge. Patients were examined preoperatively, 1 week, 1 month, 3 months and 6 months after surgery for: visual acuity, fluorescein tear film break up time, and Schirmer's baseline tear secretion test; Subjective evaluation of dry eye symptoms accomplished through Ocular Surface Disease Index (OSDI®) questionnaire at 1 month, 3 month, and 6 month postoperative visits.Results: Tear-film break up time was not significantly different with nasal or superior Hinge flap techniques at pre-op, 1 week, 1 month, 3 month and 6 month post operative visits. No significant difference between two groups was found for amount of Schirmer's baseline tear secretion test at pre and post-op visits (P>0.05 for all comparisons between two groups, β: 0.2). Subjective evaluation of symptoms also showed no significant difference in 1 month, 3 month and 6 month postoperative visits. Conclusion: Our results show that nasal and superior Hinge flap making methods do not affect signs and symptoms of dry eye after LASIK. We recommend that selecting Hinge position should be done with the surgeons' preference and ease.