We use crowbars with the rules for destroying Barriers (5E CoreBook, p.197/198). A melee attack with the Exotic Melee Weapon skill [ACC 3, like Sledge Hammer (5E R&G, p.22)] and according to the rules for crowbars with DV (STR x 2)P + Net Hits. For Barriers with weak points like door hinges or gaps a successful attack (DV > Structure) will break open the Barrier without literally destroying one square meter of it. In case of a solid Barrier the Damage is resolved as for any other non-penetrating weapon - a hole of one square meter per increment of Structure value. Additionally, we agreed on substituting Exotic Melee Weapon for crowbars with Clubs skill, but with a dicepool modifier of -4 … Yes, and the Adept Power Enhanced Accuracy (Clubs) of course also applies here

For chainsaws we use pretty much the same rules. Exotic Melee Weapon skill [ACC as listed] (no substitution allowed here) and DV as listed + Net Hits. Instead of destroying one square meter of the barrier with a successfull attack the cut has a length of one meter per increment of Structure and Barriers with weak points will be forced open.
The Mini-welder we rule a bit different. Like the crowbar there is no ACC listed and we decided - or rather I pushed through - that the Mental Limit is used instead and no Combat skill. The "attack" roll is Industrial Mechanics (Welding) [Mental] resolving Damage with 25P + Net Hits. If this skill is not available (and defaulting is not possible either) 25P is still a fair damage even if not buffed with Net Hits. The destruction is handled the same as for chainsaws.
A character with high STR and some Augmentations/Powers or just a Knucks to deal Physical damage (Barriers ignore Stun damage anyway) can destroy weaker Barriers like common doors quite easily, yes. With a Troll and Bone Lacing/Bone Density it could even be possible to punch through Structure 8 or 10 yet, especially when applying the Physical Limit for an attack with the Unarmed Combat skill. But well, that is what Trolls are for … With a crowbar it is even more effective strength-wise, but just think of a crowbar with metahuman customization for Trolls

As already mentioned, Barriers ignore Stun damage. We house rule this a bit and allow attacking Barriers with Stun damage, too. As long as a Character's BOD is equal or higher than the Barrier's Armor an attack has no drawback, but if not a Character suffers (Barrier's Armor)S damage from something way too solid while still being able to destroy it. Furthermore, on p.197 in 5E CoreBook it is said the Struture rating is for one square meter "
of about 10 centimeters thickness". We ignore this and loosely handle it on GM discretion (or extensive internet research

) how thick a Barrier really should be, because 10 centimeters make sense for a brick wall, but even fragile standard glass of such a thickness would be pretty much unbreackable.
And for the time required to make one attack against a Barrier we use (Barrier's Armor) Complex Actions here.
I hope this helps. Maybe not with clarifying rules written or intented, but as an inspiration how things could be handled. If there are some rules for certain mechanics making these house rules redundant, please let me know. Thanks.