Unions representing 45,000 Verizon workers announced tentative new contracts on Wednesday that call for an 8 percent pay raise over four years while requiring workers to pay more for health coverage. The contracts, covering workers from Maine to Virginia in Verizon's landlines division, come after 16 months of tense negotiations that included a two-week strike a year ago to protest the company's demands for concessions. A ratification vote is expected in the next month. At a time when many unions are facing demands for pay and pension freezes, Verizon's main unions — the Communications Workers of America and the International Brotherhood of Electrical Workers — were able to preserve the current pension plan for existing workers. But the unions did agree that future hires covered by the contracts would no longer receive traditional pensions and would instead have 401(k) accounts with a substantial company match.