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Fiber Reinforced Polymers (FRPs) have advantages such as lightness, high strength, and suppressing corrosion risk. There is a vast amount of research on the FRP strengthening of reinforced concrete elements. However, the behavior of FRP bonded Autoclaved Aerated Concrete (AAC) beams has not been extensively investigated in the past. In this study, several experiments were conducted to explore the performance of FRP bonded AAC beams. In this scope, unidirectional single layer carbon and glass fiber laminates with half or full of the beam width were bonded to the AAC. Test results were mainly evaluated by comparing the stiffness, strength, ductility, energy absorption capacity, and the cost of materials. Additionally, a numerical study (based on section analysis and finite element simulation) was conducted to estimate the load-deformation response of the specimens. Based on the analysis results, effective FRP strains were evaluated and compared with the recommendations given in the ACI 440.2R design guidelines for FRPs bonded to reinforced concrete. According to the limited test data, a 60% reduction appears to be appropriate while computing the effective FRP strains for FRP bonded AAC beams. (C) 2021 Elsevier Ltd. All rights reserved.

Autoclaved aerated concrete (AAC) walls are commonly used as infill walls in reinforced concrete frames. Thermal properties of infill walls in cold regions can be improved by bonding additional insulation panels. In this study, eight half-scale, one-bay, one-story reinforced concrete frames with insulated AAC infill walls were tested under cyclic increasing in-plane (IP) displacement excursions to simulate earthquake demands. Two different methods of insulation arrangements were studied by using mineral-based cementitious materials. In addition to in-plane loading, out-of-plane (OOP) and combined in-plane and out-of-plane (IP + OOP) tests were conducted under constant axial load and increasing cyclic displacement excursions. It was observed that insulated AAC infill walls had limited deformation capacity with premature failure of the insulation plates. The observed damage limits of the insulated AAC infills were compared with the codes' drift ratio limits. It was concluded that such walls should be classified as fragile components with limited drift capacity.

The diagonal application of Carbon Fiber-Reinforced Polymer fabrics on hollow clay tile infill walls has been qualified as an efficient rehabilitation method for deficient reinforced concrete frames. However, majority of the experimental studies were conducted on 1/3-scaled RC frames and the effect of specimen scaling has not been questioned. In the current study, the results of an experimental campaign on 1/2-scaled RC frames are presented. Test specimens are grouped in two series having two different aspect ratios. In each series, there are two RC frames having hollow clay tile infill walls with/without CFRP reinforcement. The results of 1/2-scaled specimens are compared with the experimental results obtained from 1/3-scaled frames. In addition, the numerical model which were developed by the authors for 1/3scaled frames are employed for modeling 1/2-scaled specimens and the results were assessed by comparing with the test results. BAP

In this study, seismic retrofitting of undamaged and moderately damaged RC columns with CFRP was investigated. The experimental program was conducted on five RC columns with inadequate tie spacing, 90-degree hooks at tie ends, and plain (undeformed) reinforcing bars. Columns were tested under a constant axial load of 27% of axial capacity and under reversed lateral cyclic loading. The primary objective of this study was to investigate the influence of sustained axial load during repairing, damage, and corner-rounding radius of CFRP wraps on the seismic performance of RC columns. Improved performance in terms of ductility, dissipated energy, and secant-stiffness degradation was observed for the CFRP strengthened columns. Reducing the corner-rounding radius deteriorated the seismic behavior of the columns, while the stiffness degradation response remained unaffected. The sustained axial load during repairing had only minor effect on column behavior. After CFRP repairing, the increase in yield drift ratio and curvature was observed to be in proportion with the corresponding consumed ductility values during damage cycles. A drift-based design equation for FRP repaired columns was proposed that considers the damage amount and axial load level as the major parameters as consistent with the experimental results.

The behavior of high strength concrete tied columns was investigated. A total of 11 columns were tested under monotonic loading having two different eccentricities. The main variables investigated were: (1) the mechanical ratio, (2) the spacing, and (3) the configuration of transverse reinforcement. Test results indicate that, under monotonically increasing axial load, the cross ties with a 135 degrees hook at one end and 90 degrees bent at the other end provide ductility comparable to ties supporting the intermediate longitudinal bars. Also the use of four different equivalent rectangular stress blocks (ERSBs) in predicting the ultimate strength of members made of high strength concrete was evaluated. It is concluded that calculations made using the ACI 318-02 stress block always gives an upper bound, whereas a lower bound is obtained by the CSA A23.3-94 approach. Capacities calculated using the ERSB proposed by Bae and Bayrak, and Ozbakkaloglu and Saatcioglu also agree quite well with the test results.

In the last decade, a new strengthening methodology has been developed for reinforced concrete (RC) frames with hollow clay tile (HCT) infill walls by means of diagonally applied carbon fiber–reinforced polymer (CFRP) fabrics. In the experimental part of a study conducted by the authors, this user-friendly methodology was experimentally investigated considering different aspect (height/width) ratios of the infill walls. In this study, first a numerical model of the FRP strengthened infill walls strengthened with the proposed methodology is developed. Afterwards, the numerical simulation results are validated by use of experimental response curves and finally, a parametric study, which further investigates the effect of aspect ratio of HCT infill walls is presented.

To provide increased insight regarding the bond behavior of fiber-reinforced polymer (FRP) bars, 41 glass FRP, carbon FRP, and steel reinforced concrete beams with unconfined tension lap splices were tested. The test results are analyzed to evaluate the influence of splice length, surface deformation, modulus of elasticity, axial rigidity, and bar casting position on bond strength. Furthermore, the test results are compared with the current design expression recommended by ACI Committee 440 to evaluate its applicability. This comparison clearly indicates that the current design expression is inadequate, and that a new design equation is needed. More importantly, however, this research sheds light on the importance of the axial rigidity of the reinforcement on bond strength. Test results demonstrate that bond strength is linearly related to the axial rigidity of the reinforcement. This finding has future implications regarding the development of improved design expressions and allowing for an improved understanding of bond strength.

The use of mesh reinforcement with mortar on existing brick infill walls of reinforced concrete (RC) frames is a recommended seismic strengthening procedure in the Turkish Seismic Code (2007). The premise of the method lies in its ease of application and success in eliminating the out-of-plane failure of existing infill walls. The performance of the mesh reinforced mortar (MRM) application was investigated by pseudo-dynamic (PsD) and cyclic testing. A three-story-three-bay 1:2 scale RC frame with hollow clay tile (HCT) infills in the middle bay was first tested using a continuous pseudo-dynamic test method for three synthetic ground motions compatible with the Duzce city center response spectrum. The test specimen was code complaint. No significant structural damage besides some cracking in the boundary columns was observed but the infill walls almost collapsed. After removing the infill walls of the central bay, a new HCT wall strengthened with MRM was built and the rehabilitated frame was retested under a second series of PsD and reversed cyclic loading schemes. This Chapter reports the findings of the experimental study by placing special emphasis on the seismic response of the code compliant test frame.

Bilir, Turhan/0000-0003-0317-026X; Canbay, Erdem/0000-0001-6798-0144; Baran, Mehmet/0000-0001-6674-7308 WOS: 000285893300060 The objective of this research was to develop an economical, structurally effective, and practically applicable steel fiber reinforced mortar (SFRM) which could be applied onto the hollow brick infills of a reinforced concrete (RC) structure. Masonry walls were almost converted into strong and rigid infills with the application of SFRM. Two different mix proportions were produced with the composition of Portland cement, fine aggregate, water, and plasticizer or bonding agent as the chemical admixture. Tests were carried out to determine the optimum steel fiber content (1%, 2%, or 4% by volume) and to clarify the use of plasticizer or bonding agent in the mortar in the context of sticking ability, flexural, compressive, and adhesion strengths. As a result, mortar with plasticizer and 2% steel fiber (by volume) came out to be the optimum mortar mixture as strengthening material. The performance of RC frame strengthened with SFRM containing plasticizer and 2% steel fiber by volume was compared to those of the hollow brick infilled RC frame without strengthened mortar and the hollow brick infilled RC frame with reference mortar. It was observed that the specimen strengthened with the optimum mortar mix satisfied the target objectives of this study. (C) 2010 Elsevier Ltd. All rights reserved.

While the estimation accuracy of the strength of lap splices has been improving, the complexity of design for reinforcement development has progressively increased. This research study investigates the development of a simple and reliable design expression. Equations on development and splices of reinforcement in ACI 318-05 along with other design proposals are critically assessed in light of 203 unconfined and 278 confined beam tests where the splice region was subjected to constant moment. A simple design provision is developed that is based on a physical model of tension cracking of concrete in the lap spliced region. This new expression is shown to be consistent with current design practice, applicable to existing test results, and simple in application.

The performance of reinforced concrete structures depends on adequate bond strength between concrete and reinforcing steel. This article reports on a study of the bond strength of lap-spliced bars. The authors note that calculation methods to evaluate the strength of tension lap splices are based primarily on nonlinear regression analysis of test results. However, the results from these analyses may not be generalizable to situations beyond the domain of the data. In this study, the authors developed an expression for the calculation of bond strength based on a physical model of tension cracking of concrete in the lap-spliced region. Two different types of failure modes are considered: horizontal splitting that develops at the level of the bars (side-splitting failure), and vertical splitting that develops along the bar on the face cover (face-splitting failure). The developed expression was verified using results from 203 unconfined and 278 confined beam tests where the splice region was subjected to constant moment. Results showed that the relation between splice strength and splice length is not linear. The use of the fourth root of the concrete strength provides an improved estimate regarding the behavior of lapped splices as compared with the square root. In addition, the effect of the thickness of the concrete cover surrounding the bar is not linear.