Research on retrofitting the compression zones of reinforced concrete elements with fiber polymers (FRP)

Most part of Türkiye is in the 1st degree earthquake zone. In the past, Erzincan (1992), Dinar (1995), Adana-Ceyhan (1998), Kocaeli-İzmit (1999), Bolu-Düzce (November 1999), Bingöl (2003), Elazığ (2010) eartquakes occurred and caused heavy losses to Türkiye. In the recent years Van-Tabanlı (October 2011), Van-Edremit (November 2011) and finally Kahramanmaraş Pazarcık-Elbistan (February 2023) earthquakes occured in our region and once again reveal the reality. These earthquakes caused severe both material and moral damage. Observing these damages and intermittent building stock, construction of earthquake-resistant buildings is important, critical and very urgent issue but also it is understood that retrofitting of existing buildings is an vital issue that needs to be studied. The retrofitting scheme needed in reinforced concrete structures may not be due to the structure being damaged by an earthquake. There are several reasons which are the use of materials that do not comply with standards and regulations, wrong project design, poor workmanship, corrosion, inadequate wrapping, lack of control, change of purpose of use, etc. For various reasons, buildings need to be retrofitted. The effectiveness of the retrofitting methods should be investigated experimentally regarding the application of these methods and how these structures will behave in a possible earthquake. After Kahramanmaraş Pazarcık-Elbistan (February,2023) earthquakes, studies, site investigations and reconnaissance works were carried out. In field studies, show that structures consists shear walls systems were severely damaged during the earthquake, but damaged shear wall prevented collapse of building by eliminating the earthquake damage to other structural elements. If there was a shear wall in a building, the majority of the effects of the earthquake was covered by reinforced concrete shear walls. This once again prove that the loss of lives due to the inclusion of shear walls is greatly reduced. The aim of this study is to restore the reduced ductility of the beam middle regions under the effect of pressure and boundary zones of shear wall, which are under the effect of relatively higher axial forces, by externally wrapping with fiber reinforced polymer (LP/FRP), with details not considered and taken into account in the literature. It is planned to conduct experimental and theoretical research on retrofitting alternatives and the behavior of wall boundary zones before and after retrofitting. Common construction and workmenship mistakes in practice seriously reduce the ductility of reinforced concrete elements. By standart definition and by regulation definition, adequate confinement must be provided in the ductile element so adequate confinement can be provided externally application with FRP. Externally application of FRP to shear wall boundary zones with using additional FRP anchors will increase the confinement effect, and this will effect the ductility level of the structural elements as stipulated by the regulations. In the thesis study, firstly, the effectiveness of strengthening the pressure zones of middle part of dapped-end prefabricated beams by wrapping and anchoring them with externally application of LP with anchoring was investigated. In the second part of experimental study, a simple test specimens developed and proposed to carry out the experimental work. Experimental specimens represent abstract from boundary zone of slender shear wall which is under compression region. Within the scope of this thesis study, model shear wall specimens behaviors were compared with both original and strengthened. Also, the effectiveness of different retrofitting details was investigated. Finally, the retrofitting details were examined by anchoring and externally application of FRP on boundary zone of shear wall. Experimental results showed that anchoring with external wrapping FRP was effective in increasing the confinement and deformation capacity of the samples. In addition, it is thought that the experimental data obtained can be used in developing models for theoretical calculations of the strengthened zones. Keywords: Compression zone, Confinement, Ductility, FRP, Prefabricated Beam, Reinforced Concrete, Retrofitting, Shear Wall