minecraft-assets/data/minecraft/worldgen/structure_set/strongholds.json

{
  "placement": {
    "type": "minecraft:concentric_rings",
    "count": 128,
    "distance": 32,
    "preferred_biomes": "#minecraft:stronghold_biased_to",
    "salt": 0,
    "spread": 3
  },
  "structures": [
    {
      "structure": "minecraft:stronghold",
      "weight": 1
    }
  ]
}