Banca de DEFESA: Nataniel Wontoon Barbosa Lima
Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.STUDENT : Nataniel Wontoon Barbosa Lima
DATE: 15/04/2024
TIME: 14:00
LOCAL: UNIVERSIDADE DE BRASÍLIA
TITLE:
KEY WORDS:
Concrete cone strength, headed bars, flexural reinforcement, edge and group effects, supplementary reinforcement.
PAGES: 157
BIG AREA: Engenharias
AREA: Engenharia Civil
SUBÁREA: Estruturas
SPECIALTY: Estruturas de Concreto
SUMMARY:
This study presents the results of 38 pull-out tests on headed bars pre-installed in the tension zone of slender reinforced concrete elements. Among these tests, 12 investigated the influence of longitudinal reinforcement on the ultimate tensile strength of headed bars when subjected to edge effects or to the combined action of edge and group effects. These specimens were designed to fail by concrete cone failure, and the rate of longitudinal reinforcement was determined to control the level of concrete cracking, maintaining crack widths close to zero before failure. The remaining 24 tests primarily aimed to investigate the influence of supplementary reinforcement and the concrete's compressive strength on the concrete cone strength of headed bars subjected to edge and group effects. The main variables included the effective anchorage length, the spacing between headed bars, and the distance from these bars to the edges of the reinforced concrete elements. Furthermore, 16 tests conducted by Costa (2016) were used as references to extend the above-mentioned analyses. The experimental strengths were compared to those estimated using calculation methods presented in ACI 318 (2019) and EN 1992 - 4 (2018) standards, and proposed by Regan (2000), Sharma et al. (2017), and EOTA/ETAG Annex C (2012), which are analyzed and discussed. The results indicated that longitudinal reinforcement effectively controlled crack openings, maintaining the strength levels of headed bars in tension zones, similar to those in uncracked concrete. The anchorage length was the variable that had the most significant influence on the concrete cone strength of the headed bars, as expected, and the group effect tended to reduce this strength in specimens without supplementary reinforcement. The presence of supplementary reinforcement, in turn, increased the connector strength by up to 56% and made the failure more ductile, in addition to increasing the conservatism of the theoretical models analyzed. Among the analyzed calculation methods, the one proposed by Regan (2000) provided estimates that best matched the experimental strengths for specimens without supplementary reinforcement. In those where the influence of this reinforcement was observed, the calculation method proposed by Sharma et al. (2017) provided closer estimates to the experimental strengths, although under-strength values were obtained for specimens with the lowest concrete compressive strength.
COMMITTEE MEMBERS:
Presidente - 1847391 - MARCOS HONORATO DE OLIVEIRA
Interno - 1122599 - GUILHERME SALES SOARES DE AZEVEDO MELO
Externo à Instituição - HELDER PONTES GOMES - IFPI
Externa à Instituição - MONICA REGINA GARCEZ - UFRGS