A new empirical model to estimate the joint shear strength of both exterior and interior beam–column connections is proposed. In the model, four parameters that have the most influence on joint shear strength are considered. Among these four, a new parameter is introduced to consider the bond condition and the possibility of beam bars transferring joint shear force into the columns. Consideration of this parameter in the model significantly improves the accuracy of the predicted joint shear strength. To calibrate the model, a large database of 98 reinforced concrete (RC) exterior and 73 RC interior beam–column connections displaying joint failure mode was compiled from the literature. A parametric study was also carried out to evaluate the dependence of the predicted to tested joint shear strength ratio on the four influence parameters using the database. The proposed model showed superior performance over existing models. Moreover, comparisons of the predicted joint shear strength with experimental results and with four existing models showed the accuracy of the proposed model.
5 Abstract: This study investigates three methods of strengthening existing reinforced square concrete columns under different loading 6 conditions. Four groups of sixteen reinforced concrete square columns were made from normal-strength concrete. Reinforcement was kept 7 at minimum ratio, simulating columns that need retrofitting. Columns of the first group were reference columns (Group N), while the corners 8 of the second group columns (Group RF) were rounded and wrapped with three layers of carbon-fiber-reinforced polymers (CFRPs). The 9 sides of the columns of the third group (Group CF) were bonded with four pieces of concrete with a segmental circular shape, thus changing 10 the cross section of the column from a square to a circle before each column was wrapped with three layers of CFRP. The columns of the 11 last group (Group CS) were modified as the 2 third group to result in a circular cross section, but were confined with steel straps. Results 12 from the study showed that all confinement methods increased the capacity and ductility of columns. In particular, segmental circular con13 crete covers dramatically reduced the stress concentration at the corners and increased confinement efficacy. The interaction (P–M) 14 diagrams of experimental results and theoretical analysis all confirmed high performance of groups RF and CF. DOI: 10.1061/(ASCE) 15 CC.1943-5614.0000335. © 2013 American Society of Civil Engineers. 16 CE Database subject headings: Fiber reinforced polymer; Eccentric loads; Reinforced concrete; Concrete columns; Experimentation. 17 Author keywords: Square columns; Steel straps; P–M interaction diagram.
This study conducts an experimental and numerical investigation on the failure and impact resistance of plain and fiber-reinforced polymer-confined concrete. The impact resistance of concrete cylinders wrapped with different types of fibers including carbon fiber and glass fiber is examined. Drop-weight tests are utilized to conduct the impact tests while the numerical simulation is conducted using LS-DYNA. The experimental and numerical results have proved that fiber-reinforced polymer can be efficiently used to improve the impact resistance of concrete cylinders. In general, fiber-reinforced polymer ruptures at a lower strain than those in static tests and the rupture strain of glass fiber is much higher than that of carbon fiber. The findings in the experimental tests are confirmed by the numerical results. Glass fiber, therefore, exhibits a much better performance than carbon fiber. It is recommended to use glass fiber to enhance the impact resistance of concrete structures strengthened with fiber-reinforced polymer. In addition, the stress evolution of the specimens is analyzed to investigate the failure mechanism.
