The scope of this study is the investigation of the rehabilitation of structures retrofitted by use of carbon-fb01brereinforced plastics (CFRPs) to achieve a safe, economic and practicable level of seismic damage. This paper investigates analytically the efficiency of the strengthening technique for improving the seismic behavior of damaged structures. 4 beam-column connections are tested under reversed cyclic load. The connections have none-seismic detailing of rebars, i.e., no transverse rebar and seismic stirrups are used in the joint core and beam and column critical end zones. The joints are damaged in different levels and then retrofitted by CFRP sheets. The strengthened joints are tested again to reach the ultimate drift capacity. Then, the tested joints, such as reference joint and retrofitted joints, are analyzed by Opensees nonlinear software. The results of joint analysis are compared with experimental behavior of specimens. The hysteresis curves of the modeled joints had a high level of accuracy in terms of stiness degradation, moment carrying capacity, capacity degradation and energy dissipation. In the following, a multi-story/multibay moment-resisting frame is selected for assessment of seismic response of damaged frames. So, a step-by step pushover analysis is done in order to find the plastic hinge positions and the level of plasticity on the moment resisting frame. The plastic hinges are developed on the beam ends and middle length of the frame beams. As the analysis progresses, the damaged frames are categorized in 7 levels according to performance levels defined by FEMA 356. The damaged Frames are retrofitted by CFRP sheets, considering the level of damage similar to the tested joints mentioned above. At the end, the retrofitted frames are subjected to El-Centro base acceleration. The root mean square parameter of roof displacement is also calculated for nonlinear time history response of frames. The retrofitting of the plastic hinges improved the RMS of the responses and compensated the lost capacity and stiffness. The results show that reparability level of frames retrofitted by CFRP sheets is equal to the level that the hinges on all of the beams are formed in collapse-preventing performance level. This level for specific frame investigated in this study is equal to 1.03% storey drift. Also, the results show that structures could be retro fitted by external bonding of FRP sheets to a limited level. If the damage level of structures is higher than this reparability level, other rehabilitation methods may be useful.

Civil engineers have always been vexed by such numerous problems such as buckling, corrosion, bending, and over-loading in damaged steel structures. The present study is aimed to evaluate the effects of the axial loading, axial displacement, stiffness and deficiency location on the length of the deficient steel SHS columns have been evaluated based on a detailed parametric study. Three specimens were tested to failure under axial compression in the lab and simulated using the Finite Element (FE) numerical approach and a total of 100 samples were analyzed by ABAQUS using the MATLAB software to predict the suitable limit state functions and determine the best R2 value through such soft computing techniques as the Artificial Neural Networks, Adaptive Neuro-Fuzzy Inference System, Response Surface Method, and Gene Expression Programming. Finally, the failure probability and reliability index were obtained by the FORM and Monte Carlo methods on the suggested limit state functions. Results indicated that using CFRP sheets reduced the stress in the damaged location and appropriately prevented or delayed local deformations around the deficient location. So, strengthening steel columns with CFRP can play a significant role in enhancing the rate of the critical load and β , and reducing (Pf ), in deficient columns.

The repair and strengthening of RC structures has become a major problem for civil engineers in the past few decades. To satisfy this problem, a previous method for the repair and strengthening of RC beams included bonding steel plates to the inferior structure. However, bonding steel plates to concrete presents disadvantages, including corrosion of the steel/adhesive joints and the heavy weight of the material. These problems increase installation and maintenance costs. The bonding of Fiber Reinforced Plastics (FRP) to structures provides an attractive alternative to steel plates. This material is corrosion resistant and lightweight, has a high strength-to-weight ratio and possesses nonconductive properties. The use of Fiber Reinforced Plastics (FRP) in repairing and strengthening RC beams has been researched in recent years. In particular, attaching unidirectional FRP to the tension face of RC beams has provided an increase in the stiffness and load capacity of the structure. However, due to the brittle nature of unidirectional FRP, the ductility of the beam decreases. Consequently, the safety of the structure is compromised, due to the reduction in ductility. The purpose of this research is to investigate the behavior of high strength reinforced concrete beams strengthened with FRP sheets. The major test variables included the different layouts of CFRP sheets and the tensile reinforcement ratio. More particularly, change in the strength and ductility of the beams, as the number of FRP layers and tensile reinforcement bar ratios are altered, is investigated. Eight under-reinforced concrete beams were fabricated and tested to failure. With the exception of the control beam, one or four layers of CFRP were applied to the specimens.

In this study, four scaled circular-shaped bridge columns were established, three of which were retrofitted using three different strengthening methods to wrap or confine the columns. Specimens were subjected to a constant axial load and a cyclically reversed horizontal force. Results of the investigation on experimental phenomena and data, showed that the three reinforcement materials served a significant function in confining the core concrete of columns for strength improvement of core concrete, thus resulting in enhanced ductility compared with an unstrengthened column. Among the three strengthening materials, the column is strengthened by Aramid fiber-reinforced polymer (AFRP) exhibited the best performance in seismic events.

Side-channel attacks are considered to be the most important problems of modern digital security systems. Today, Differential Power Attack (DPA) is one of the most powerful tools for attacking hardware encryption algorithms in order to discover the correct key of the system. In this work, a new scheme based on randomizing power consumption of a fixed-operation logic gate is proposed. The goal of this method is enhancing the immunity of AES algorithm against DPA. Having a novel topology to randomize the power consumption of each Exclusive-NOR gate, the proposed circuit causes random changes in the overall power consumption of the steps of the algorithm; thus, the correlation between the instantaneous power consumption and the correct key is decreased and the immunity of the AES implementations which the key is injected into their process through Exclusive-NOR gates is extremely increased. The proposed method can be used as a general hardening method in the majority of cryptographic algorithms. The results of theoretical analysis and simulations in 90-nm technology demonstrate the capability of the proposed circuits to strengthen AES against DPA. The CMOS area and power consumption overhead is less than 1%.

One of the usual method for seismic retrofit of existing reinforced concrete buildings is steel bracing. The use of steel bracing and reinforced concrete shear wall for strengthening of existing reinforced concrete buildings usually leads to very complicated system and the study of this kind of structures is necessary. In this paper, the frame-shear wall and steel bracing interaction is investigated by the analysis of a then-story reinforced concrete building. The analytical results show that with an increase in the section area of steel bracing, the lateral displacement and earthquake shear absorption by the frame decreases. Increasing the section area of steel bracing improve the overall response of the structure, but it has a less significant effect on the results after a certain level. The behavior of steel bracing and frame and the amount of shear absorption by both of them is approximately the same in the lower part of structure. Application of steel bracing decreases the lateral displacement by about 50 percent.    

This paper presents the results of analytical studies concerning the flexural strengthening of reinforced concrete beams by external bonding of high-strength lightweight carbon fiber reinforced plastic (CFRP) plates to tension face of the beam. Three groups of beams were tested analytically and compared with existing experimental results. Results of the numerical analyses showed that, although addition of CFRP plates to the tension face of the beam increases the strength, it decreases the beam ductility. Finite element modeling of fifteen different beams in a parametric study indicates that steel area ratio, CFRP thickness, CFRP ultimate strength and elastic modulus considerably influence the level of strengthening and ductility.

In the present research, carbon fiber reinforce polymer (CFRP) composite with fibers aligned along the column axis was used to strengthen the RC columns. A newly introduced method named as grooving method (GM) was utilized to improve the compressive behavior of longitudinal FRP and postpone the buckling and delamination of longitudinal composite from concrete substrate. Two techniques of GM, i.e. externally bonded reinforcement on grooves (EBROG, to be pronounced as / ebrΛg /) and externally bonded reinforcement in grooves (EBRIG, to be pronounced as / ebrIg /) was used, as well as EBR method, to strengthen the column specimens. For this purpose, 11 RC column specimens with circular section of 150 mm diameter and height of 500 mm were tested under uniaxial compression. Experimental results showed that using the grooving method in strengthening the column specimen, significantly increased the load carrying capacity of specimens; while the conventional EBR method showed inconsiderable effects on the load capacity. The results demonstrated that utilizing EBROG and EBRIG techniques led to respectively 14.1% and 18.5% increase in the column maximum load. However, the column strengthened with EBR method indicated only 2.6% increase in the load carrying capacity.