Sistema de reforço à punção de lajes lisas de concreto armado com polímeros reforçados com fibra de carbono (PRFC)

Abstract

This research evaluates the behavior of slab-column connections in a reinforced concrete flat slab system and subjected to symmetrical loading, strengthened to the shear with carbon fiber reinforced polymer (CFRP). The strengthening method consists in applying CFRP sheets as shear resistant element, by bonding it through perpendicular holes to the plane of the slab. As the current standards do not deal with strengthening to shear with CFRP reinforcement, it was assessed the application of the code's required from by ACI 318 (2011) Abstract Resumo IntroductionUncertainties regarding structural safety -like suspicions of project and execution error, doubts about the stability due to apparently pathological demonstrations and changes of service loads -are situations that justify an intervention with the strengthening of a structure. For the case of punching in a slab-column connection, some constructive systems which make possible this strengthening with improvement. However, these systems are invasive and, usually, imposes changes of the structure geometry. The use of carbon fiber reinforced polymer sheets (CFRP) as an alternative for the increase of the load bearing capacity of flat slabs is a simple and fast intervention, which efficiency has been proved by experimental research in the last years. The main idea of strengthening method is to install CFRP as a member resistant to shearing. The application occurs by bonding the CFRP sheets through perpendicular holes to the plane of the slab. It is necessary to pay attention to the requirements of the sheet anchorage and for the later filling of the holes with resistance grout and elasticity modulus compatible with the ones from the substratum. There are not regulations specifically dealing with the use of CFRP as slab punching reinforcement. Then, the objective of this research is to evaluate the safety, economy and the accuracy of the application of some of the main project regulations in the slab punching resistance in reinforced concrete strengthened to punching with CFRP. (2002) [1] will be adopted so that these regulations can be used in the case studied, with CFRP reinforcement, in which the deformation limits of ACI 440.2R is considered. This last code deals only with the strengthening of reinforced concrete structures using fiber-reinforced polymers. From the calculation results, will be evaluated the dispersion and the conservatism level of each case. JustificationThe study of strengthening to flat slab punching is justified by the progressive use of this structural system, combined with the dangerous awareness of a ruin by shear. The common strengthening to punching techniques, basically, consist in the use of capitals (made of concrete or metal) in the strengthening of a flexure reinforcement or in the posterior introduction of a shear reinforcement composed by steel bolts. The additional resistance provided by the posterior fastening of steel bolts in the critical shear area is an alternative that rules out the possibility of part geometry change. Ho...

A Utilização do Concreto Estrutural com Adição de Fibras não Metálicas na Construção Civil, uma Prospecção Tecnológica

“…Também foram encontrados estudos sobre a utilização de concreto com adição de fibras em obras industriais (LUNA et al, 2014); trabalhos que estudam a substituição das barras de aço por barras feitas de polímeros de fibras de vidro (FERNANDES; PALIGA; PALIGA, 2021); e estudos dobre a utilização de fibras em blocos de concretos utilizados em paredes de alvenaria estrutural (BERNARDES et al, 2013). Outros trabalhos analisaram as propriedades do concreto reforçado com fibras quando exposto a temperaturas elevadas, avaliando a condutividade e a dilatação térmica (AMARAL; MORAVIA, 2020; HEO et al, 2010) e até estudos avaliando modelos de reforço utilizando fibras para combater o esforço de punção em lajes (SANTOS et al, 2014).…”