Reinforced Concrete Frames Strengthened by Tension-Tie Elements Under Cyclic Loading: A Computational Approach

Abstract

Abstract. An efficient numerical simulation of the seismic response of single-story single-span Reinforced Concrete (RC) frames strengthened using diagonal tension-tie elements is presented. The developed analysis is based, calibrated and verified on test results of bare and X-braced RC frames subjected to cyclic imposed lateral deformations described in a companion paper. The dimensional and the reinforcement configurations of the frames represent earlier RC frame structures that have been designed using old Code provisions without consideration of seismic design criteria and. The columns of the RC frames have shear-critical character due to the inadequate amount of stirrups provided and their low height-to-depth ratio (short columns). Therefore, an easy-to-apply strengthening technique using a pair of two steel crossed tensionties (X-type bracing) is applied and examined. For the numerical simulation, the unilateral behavior of the cable elements that undertake only tension stresses is strictly taken into account.Comparisons between the analytical curves derived from the numerical simulation and the experimental ones from the cyclic tests showed a very good agreement.

Reinforced Concrete Frames Strengthened by Tension-Tie Elements Under Cyclic Loading: Experimental Investigation

“…The herein obtained experimental results are used in a companion paper [24] for the calibration of a numerical approach concerning the hysteretic response of RC frame structures strengthened by tension-tie elements.…”

“…Several studies demonstrated that through the use of steel braces enhances the seismic performance of the strengthened frame improving strength, stiffness and energy dissipation capacity. A specific category in the brace strengthening technique of existing RC frames concerns the use of X-type cable elements [17][18][19][20].…”

Existing RC structures strengthened by ties under seismic sequences considering uncertainty

“…After the seismic assessment [1][2][3][4][5][6]12] of RC frame F0, the need for seismic upgrading has been resulted. Thus, the X-cable bracing system F6, as shown in Figure 3, has been proposed in order the frame F0 to be seismically strengthened.…”

“…The sequence of events E 1 and E 2 is denoted as Event (E 1 + E 2 ). In column [3] the mean value and in column [4] the coefficient of variation (COV) of the Global Damage Indices (DI G ) are given. Similarly, in columns [5] and [6], the mean value and COV of the absolutely maximum horizontal top roof displacement (u top ) are given.…”

“…These cable members (ties) can undertake tension, but under a sufficiently large compression force they buckle and become slack and structurally ineffective. Thus, the governing conditions take equality as well as an inequality form and the problem becomes a highly nonlinear one .…”