Purchase of all supplies, materials and equipment for the city shall be made pursuant to specifications through open competitive bidding under such rules, consistent with this charter as the council may establish by ordinance. Formal advertising, bidding and public opening and tabulation of bids shall be governed by the general law of the State of Ohio and as the same may, from time to time, be amended. In cases of public disaster, declared by resolution approved by a unanimous vote of the council present, a quorum being present, purchases may be made in the open market without competition. (Amended 11-6-84.)