Thanks for your replies mates
So here is the Q/A:
Q1: When a titan is equipped with a Close Combat Weapon that can destroy buildings, when is this attack resolved ?
A1: depend on Titan Order
- during first fire segment if titan has a First Fire order
- during close combat segment if titan has a Charge order
- during advance segment if titan has an Advance order
Q2: If this attack is not considered as a Close Combat attack, does the Eldar Power Fist (or any titan weapon that can be used to shoot or for close combat) could perform both a ranged attack and a free building attack ?
A2: this attack is not a close combat attack and Eldar Power Fist (or other equivalent weapons for others faction titans) can be used to shoot (if titan is on First Fire or Advance) and perform the free building attack
Q3: When a titan is equipped with 2 close combat weapons and each has the ability "Destroy Buildings", does the titan get 2 attacks Vs 1 building (resolved separately) or should we consider it only uses 1 weapon so 1 attack ?
A3: Titan can attack twice this building and building must save 2 times or be destroyed
Q4: When titan is in base contact with 2 (or more) buildings (rare case), does it get 1 attack against each building or can it only attack a number of building equal to the number of equipped weapons that can destroy buildings
A4: Titans can attack a number of buildings equal to the number of weapons with free building attack ability. So a titan in base contact with 2 buildings equipped with 2 weapon can perform 2 attacks Vs 1 building or 1 attack against each building
Q5: Are those free destroy buildings attacks limited by the weapon fire arc (ie: 180° side for an arm gargant weapon, 180° front for an imperial titan) ?
A5: Yes