Strengthening of CHS T-joints Subjected to Brace Axial Compression Forces using Through Bolts

Abstract

6.1. Overview This chapter outlines a brief summary of the current research. The main conclusions together with recommendations for future studies are also presented. A comprehensive literature review is done to cover all the aspects of the research that deals with the strengthening of circular hollow sections joints. It was found that strengthening of circular hollow section T-joints subjected to brace axial compression forces using through-bolts needs further studies and experimental investigation of the effectiveness of this strengthening technique as it was studied numerically by Mohamed et al. (2013). Therefore, the main aim of this research was to broaden the study of the effectiveness of strengthening of circular hollow section T-joints subjected to brace axial compression forces using through-bolts experimentally and numerically. An experimental program was conducted to contain six T-joints specimens: one control specimen and five strengthened specimens. The main parameter that was changed in the five strengthened specimens was the pattern of through-bolts (i.e. the number of the through-bolts and the spacing between them). One specimen was strengthened by one through-bolt, two specimens were strengthened by two through-bolts spaced at 50 mm and 100 mm, two specimens were strengthened by three through-bolts spaced at 50 mm and 100 mm. The results of the experimental program were presented and studied in Chapter 3. Finite element model was developed using a finite element package, known commercially as ABAQUS. This model was verified against the experimental program results and showed good conformance, so it was adopted to numerically complete the study. A simplified model was developed and verified against the full model that was previously verified. A comprehensive parametric investigation was conducted numerically using the simplified finite element model. Two main parameters were studied: the chord member wall thickness (i.e. class of section) and the pattern of the through-bolts (i.e. the number of the through-bolts and the spacing between them). The study included 42 FEM models that were divided into three main groups. Group 1 contains 14 models with chord member wall thickness of 2.8 mm (Class 4 section), one control model and 13 models strengthened by different number and spacing of through-bolts: one through-bolt, 2, 3, 4 through-bolts spaced at 40 mm, 80 mm, 120 mm, 160 mm. Group 2 contains 14 models with chord member wall thickness of 3.4 mm (Class 3 section), one control model and 13 strengthened models by different number and spacing of through-bolts: one through-bolt, 2, 3, 4 through-bolts spaced at 40 mm, 80 mm, 120 mm, 160 mm. Group 3 contains 14 models with chord member wall thickness of 4 mm (Class 2 section), one control model and 13 strengthened models by different number and spacing of through-bolts; one through-bolt, 2, 3, 4 through-bolts spaced at 40 mm, 80 mm, 120 mm, 160 mm. A further study was conducted numerically to investigate the effect of using curved washers instead of the ordinary flat washers which were used in the parametric study. The study contained three models just the same as the three models strengthened with one through-bolt with different classes of the section (i.e. with different chord member wall thickness; 2.8 mm, 3.4 mm and 4 mm).