The Olympic distance (1.5 km swim, 40 km bike, 10 km run) rewards fitness across all three sports and the ability to sustain a strong effort for roughly two to three hours for most age-groupers.
Phase 1 (around 6 weeks): build volume and technique, mostly easy work, strength training twice a week
Phase 2 (around 6 weeks): add threshold sessions in each sport and weekly brick sessions
Phase 3 (around 3 weeks): race-specific efforts, open water practice, transition rehearsal
Taper (about 1 week): reduce volume while keeping some intensity
A sample mid-build week with about 8-9 hours: 3 swims (one technique, one threshold, one endurance), 3 rides (one interval, one tempo, one longer), 3 runs (one interval, one easy, one long), with a short brick run after one of the rides. Strength once or twice.