سلوك الأعتاب الفولاذيه المقوسة المحتوية على فتحات ومقواه بصفائح فولاذيه

Behavior of Arch Steel Beams with Openings and Strengthened with Steel Stiffeners

This research aims to investigate the structural behavior of arched steel beams with and without web circular openings, strengthened and non-strengthened using steel stiffeners. For this purpose, experimental and numerical work was implemented. The experimental work included testing seven simply supported arched I-shape compact steel section beams under two concentrated and symmetrical loading. The beams were categorized into two groups, in addition to an additional beam without openings as a control beam. The first group consisted of three arched beams with different numbers of non-strengthened circular openings in various locations. On the other hand, the second group consisted of another three arched beams with circular openings strengthened by steel stiffeners. The studied parameters were: the existence of circular opening, location of the opening, number of openings and strengthening effect using steel stiffeners.
The experimental results for the first group revealed that creating openings at the mid-span decrease the ultimate load capacity by (12.5%) while edge openings had minimal effect on ultimate strength, nearly 9%, if compared with reference beam without opening. Furthermore, decreases in the horizontal displacement of the specimens were observed by about (9 to 33%), and (19 to 32%) in vertical mid span deflection, when compared with the control beam. In contrast, the reductions in the ultimate loads for the second group were nearly (8 to 11%), while the decreases in the horizontal displacement were (9 to 29 %) and (12 to 29%) for vertical mid span deflection when compared with the reference beam. Moreover, strengthening the openings’ region by steel stiffeners slightly increased the ultimate strength by nearly (1% to 3%) if compared with the non-strengthened beams.
Non-linear finite element analysis was performed using ABAQUS program to compare with experimental work and studying the effect of new parameter: opening diameter, openings number, opening shape, steel yielding stress, adding stiffeners, arched beam radius, support type and effect of strengthening using steel stiffeners around the opening. There was a reasonable convergence between the experimental and numerical results in terms of the ultimate load, maximum deformations, load-deformation curves, and mode of failure. The average difference in the ultimate load, the maximum horizontal displacement and the maximum vertical midspan deflection found to be equaled to 1.97%, 5.13% and 22.66% respectively.
Furthermore, the results obtained from the numerical analysis of the arched beams revealed that the ultimate failure loads decreased by nearly (2 to 21%) as the opening diameter at the middle web increases from (50 to 125mm) respectively. On the other hand, the ultimate failure load of the arched beams with openings near the supports decreased by about 26% when the diameter increased to 125mm in comparison with the control beam. Besides, the results revealed that the increase in the steel yielding stress increased the ultimate load capacity for all types of beams, in which the ultimate strengths of the arched beam without opening and arched beam with middle opening reached to (153.36, 142.2KN), respectively at experimental yielding stress (333 Mpa for the web and 340 Mpa for the flange) and decreased by about 24% at 248 MPa and increased by about (10% and 36%) at (360 Mpa and 450 MPa) respectively . Furthermore, increasing the radius of the arched beams (i.e. using 537.3, 797.5 and ∞ mm radii) caused a decrease in their ultimate load capacity and the stiffness. In addition, adding steel stiffeners at the maximum bending moment and maximum shear zones increased the ultimate failure load of the arched beams by (0.75%, 1.8%, 2.29%, 7.60%) when using 2, 4, 6 and 9 stiffeners, respectively at both sides of the beam if compared with the arched beam without added stiffeners.