Nurses at Washington Hospital Center have voted to ratify a new contract that raises most nurses’ hourly base wages but eventually cuts shift pay for many who work evenings, nights and weekends, union and hospital officials said Monday.

The agreement, which covers 1,650 registered nurses at the Washington region’s largest hospital, was reached last week and ratified Friday and Saturday. It also gives nurses more of a voice in staffing and patient care by establishing a new committee and includes a return to work for eight nurses fired during the back-to-back snowstorms in February 2010.

The new pact raises most nurses’ hourly base rate wages between 6 and 9 percent over 31 / 2 years. The contract calls for yearly step increases between 1.5 and 2.25 percent and a 1.5 percent across-the-board increase in the third year.

The wage increases for the nurses come at a time when public sector employee unions have been struggling. In Montgomery County, County Executive Isiah Leggett (D) has recommended a budget that cuts benefits and blocks pay raises for police officers as part of a broader dispute over the way the county and its public employee unions engage in future bargaining over salaries and benefits.

In the public sector, the common trend is for no wage increase or wage or pension cuts to protect against layoffs, said Gary Chaison, an expert on collective bargaining at Clark University in Worcester, Mass., who has also studied nurses unions.

In the private sector, nurses have an advantage because “they can strike effectively” and the public is generally on their side, he said.

Several hundred nurses at Washington Hospital Center took part in a one-day strike March 4 after the two sides were unable to reach a settlement. The nurses’ contract expired about a year ago. The new one took effect Sunday.

The hospital center nurses are represented by National Nurses United, the country’s largest nurses union — an organization that is growing in numbers and has not been afraid to walk picket lines.

On one of the biggest sticking points, the two sides agreed to restore the extra pay that nurses receive for working evenings, nights and weekends to pre-March 2011 levels for 30 months of the 42-month agreement. The differential pay was a key issue for many nurses who took part in the strike.

Unlike several area hospitals that pay a flat hourly rate, the hospital center had used a percentage of base pay to calculate how much extra nurses receive for those shifts. Moving to a flat rate would cut $2,000 to $20,000 per nurse a year, depending on seniority, officials have said.

Under the new contract, nurses would be paid at a flat hourly rate for the remaining 12 months.

The hospital says that entry-level nurses make about $57,000 a year and that experienced nurses earn about $98,000. The union says average pay is about $37 an hour, so a typical 36-hour workweek would bring in about $70,000 a year.