Seismic Behavior of Existing Reinforced Concrete Columns with Non-Seismic Details under Low Axial Loads

Abstract

Reinforced concrete (RC) columns of old existing buildings are vulnerable to earthquakes because the hoops comprising their transverse reinforcement are widely spaced and anchored using 90° hooks. This study extensively evaluated the seismic behavior of RC columns with such non-seismic details. Experiments were conducted by applying lateral cyclic loads to five full-scale column specimens with various transverse reinforcement details subjected to low axial loads. The experimental results demonstrated that the internal transverse crosstie had a significant confinement effect in the non-seismic detailed columns with 90° hoop anchor hooks. In addition, the lateral load–drift relationships, ductilities, and energy dissipation capabilities of the columns were not significantly affected by the hoop spacing or anchor hook angle when a low axial load was applied up to a drift ratio of 3.5% before failure. The evaluation model based on ASCE/SEI 41-17 was then shown to approximate the initial stiffness, maximum strength, and post-peak strength reduction behavior of the non-seismically reinforced column. This study was based on the experimental behavior of single column members, and it needs to be extended to research on frame structures in which columns are connected to beams and slabs.

Ultimate Shear Force of an Any Anchor Group Post-Installed into Concrete

“…The strength of the vast majority of the tested specimens reported in the literature was dictated by premature failure modes [ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 ]. In fact, the mechanisms that occurred in most of the experimental tests were concrete pry-out failure, concrete splitting, concrete breakout, concrete edge failure, or anchor failure.…”

“…Moreover, the phenomena that have been investigated for cast-in and post-installed shear anchors are premature failure modes, i.e., concrete edge failure, concrete splitting, anchor failure, concrete breakout, concrete pry-out failure, cyclic load failure, collapse due to prying actions [ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 ]. Conversely, strength dictated by the concrete that surrounds the anchors by a pure shear mechanism has not been investigated, although this failure mode is the one that provides the greatest strength, so it should be the aim of anchor design as long as the geometric conditions allow it.…”

Effects of Coal Gangue Coarse Aggregate on Seismic Behavior of Columns under Cyclic Loading

“…The vertical jack is connected with the reaction girder through the directional support. Due to the small friction coefficient of the roller, it can ensure that the jack moves horizontally with the specimen without relative displacement [29]. When loading, the axial load is first applied, and then the horizontal cyclic load is applied [30].…”