In 1736, an explosion occurred in the warehouse of the bastion of São Pedro, at the same time that double ravelin was added to the fortress. Between 1737 and 1738, work at the site was directed by the Royal engineer Manuel de Azevedo Fortes, assisted by engineers Pinto de Alpoim and Jacinto Lopes da Costa. Manuel de Azevedo Fortes proposed the construction of: mounted horseman over the bastion of São João de Deus; a kitchen in front of the ravelin dos Amores; "tenalham" in front of the walls between the bastions of São Pedro and Santo António; vaults for defense of the moats, in front of all the walls, except in the rear and gates; a powder magazine alongside the castle; two bomb-proof barracks under the bulwarks of São Francisco and Santa Bárbara; the division of the ravelin de Santo António into two separate corpos per moat and with gate to the east; and openings for posterns in the bastions of São Pedro, São Francisco and walls between the bastions of São João de Deus and Santa Bárbara. A majority of the proposed projects were not executed, and only the gates of São Francisco and some ravelins were begun. Between 1746 and 1747, lands was expropriated for execution of the fortress. On 1 November 1755, the famous Lisbon earthquake caused damage to the walls and destruction of the infantry barracks.