Except as provided in Section 22-232 the Board of Trustees shall have the right and power, in their sole discretion, to provide that the principal of invested funds shall be held intact and that each beneficiary of the benefit, pensions and payments provided in this Division shall receive only such equal percentage of such monthly benefits, pensions and payments as the income from the invested funds and the moneys received in accordance with Section 22-215 of this Division, shall be sufficient to provide. Nothing in this Section shall be held to require an increase in any benefit, pension or payment provided for in this Division.