It would take a square bar of regular old 250MPa structural steel about 32x32cm to hold the space shuttle, at full throttle, and it's solid rocket boosters down.
Or 38 square bars about 5x5cm.
And 250MPa is just it's yield strength, that type of steel work hardens and has an ultimate tensile strength usually in excess of 350MPa.
There are, of course, much stronger varieties of steel.
Steel is strong
Got example, 4140 is a 1% chromium - molybdenum medium hardenability general purpose high tensile steel - generally supplied hardened and tempered in the tensile range of 850 - 1000 Mpa.
Three to four times greater tensile strength, so two 127mm (5") diameter rods would do it at 1000 MPa.
- "The in-plane loads are carried from the covers to the cylinder by 96 INCONEL® 718 draw bars with a yield strength of 1 GPa." [0]
- "The wedged conductors are CD107 copper, bonded to flat Inconel 718 plates, with a 4:1 copper/reinforcement ratio over the central column area. The yield strength of the copper is 310 MPa, up to 100 °C, while the yield strength of the Inconel plates is 1130-1300 MPa. The peak Tresca stress on the Inconel at the inside radius is calculated to be 580 MPa, while that in the copper is 310 MPa." [1]
[0] https://www-internal.psfc.mit.edu/research/alcator/data/fst_...
[1] https://dspace.mit.edu/bitstream/handle/1721.1/94967/87ja040...