Numerical investigation and dynamic analysis of CFRP sheets in the connection of concrete girders in near-fault and far-fault earthquakes

Renovation and improvement in recent years have used new methods and new materials that have not been seen in the long history of construction. Among these innovations, FRP fibers have a special place. As far as some experts think, FRP should be called the building material of the third millennium. Before the ۱۹۹۰s, there were two conventional methods for reinforcing reinforced concrete beams and columns. First, is the implementation of an additionally reinforced concrete sheath around the existing beam or column, and the second is the use of a steel sheath with grout injection. Of course, both mentioned methods require a lot of labor and are often difficult to perform in the workshop. Also, the steel sheath has little resistance to weather conditions. In recent years, the application of reinforced concrete beams and columns using FRP materials instead of steel sheaths has been widely developed. To investigate this issue in this article, after validating a model of a reinforced concrete beam in two reinforced and unreinforced states using the finite element method, three different types of corners, side and middle columns, each with two, three, and four beams are connected, were considered and simulated based on validated models. Then, in the outer part of the connection, CFRP plates with different dimensions were installed on the connection in such a way that it was applicable and the existence of the roof did not cause any problem with the implementation of CFRP. The considered values for each dimension of length, width, and thickness of CFRP were five different values, which required fifteen different modes for each connection. The results showed that by increasing the number of beams connected to the connection area, due to the increase of the surfaces involved in the connection, more capacity of the column is used. Also, the increase in the connection’s shear capacity depends on the CFRP width. After that, the thickness and finally the length of the reinforcement sheet will be effective in increasing the capacity of the system. Also, the average behavior coefficient for this structural system against far and near-fault earthquakes was calculated as ۶.۲۴.

Keywords:

dynamic analysis , polymer fibers , strengthening , CFRP , concrete beam , and column connection