Thanks guys -- :)
To me though, it just looks like a natural climbing frame for any would-be attacker to climb up on top of the vehicle --
They shouldn't be getting that close if the accompanying infantry are doing their job (and the argument should be they shouldn't be necessary, if the infantry are doing their job, as well). The reason why they've gone for a bar design is because they need to not only defeat hollow-charge warheads but also EFP (Explosively Formed Penetrators) which are a variation on the hollow-charge principle. Hollow-charge warheads work on turning the metal (usually copper) liner which covers the face of the hollow-charge warhead into a liquid which is projected forward at high speed and high temperatures, to literally burn it's way through the armour plate, like a knife through butter.
In the 1970s, some smart fellows in the US worked out they could use this to project a thicker plate which instead of being liquified forms a semi-plastic penetrator, which works like the dart of a long-rod APFSDS round to force it's way through the armour at incredibly high speed. Whereas, as has been pointed out, merely making the warhead go off, beyond it's optimum distance from the target's armour was sufficient to degrade it's penetrative ability significantly and so protect the vehicle, with an EFP you need to basically not only make it explode away from the armour but you also need to degrade it's penetration by forcing it to go through some serious metal work. So, while anti-HEAT protection could be made of, as has been noted bed springs and mesh or thin plate steel (WWII Schutzenplatte), you need something more substantial against an EFP and the bars are made of hardened steel (usually nearly as tough as the armour plate itself).
This is a good diagram of how an EFP works:
This is a good picture showing an EFP disk and a penetrator: