A new $1 billion joint services military hospital at Fort Belvoir in Fairfax County is ready to provide “world-class” medical treatment to service members injured in Iraq and Afghanistan as well as to military families, senior officials said Thursday.

Already, 1,600 medical personnel and hospital staff members are working at the new Fort Belvoir Community Hospital, with more arriving daily. Patients will be arriving starting Aug. 31.

“We’re bringing a new hospital to life,” said Vice Adm. John M. Mateczun, commander, Joint Task Force National Capital Region Medical.

The new hospital has been built as part of the 2005 Base Closure and Realignment plan, known as BRAC, which includes replacing Walter Reed Army Medical Center in Washington and hospitals at Fort Belvoir and Andrews Air Force Base with new, expanded facilities at Fort Belvoir and the National Naval Medical Center in Bethesda.

The 1.3-million-square-foot Fort Belvoir Community Hospital is four times as big as the De­Witt Army Community Hospital down the road and will nearly double the staff, from 1,600 to 3,000. It has 120 beds, three times the number at DeWitt.

The hospital, accessible from Pence Gate off Route 1, includes a six-story main structure flanked by speciality-care outpatient clinics and two parking garages. The energy-efficient building includes abundant windows allowing natural light, healing gardens and acoustically absorbent materials.

“It’s really a paradigm shift from DeWitt,” said Rick Repeta, an emergency-room doctor at DeWitt who is serving as director of integration and transition at the new hospital. “DeWitt’s 57 years old, and it looks it. Folks are very excited to come here.”

The majority of wounded troops returning from Afghanistan and Iraq, including those suffering from serious trauma, will be treated at the new Walter Reed National Military Medical Center Bethesda, which is opening at the end of the month. Others needing certain types of specialty care will be sent to Fort Belvoir.

The new Fort Belvoir hospital includes a psychological health component that will allow service members suffering from post-traumatic stress disorder, substance-abuse issues and chronic pain to have their conditions treated jointly, rather than as unrelated diagnoses.

“We’ll have a much more robust capacity to deal with wounded warriors,” Repeta said.

The new hospital is expected to handle more than 571,000 patient visits each year, including 56 percent active-duty service members and their families, and 44 percent retirees.

About 750 staff members — including many who are now assigned to Walter Reed — took part in a “day in the life” training exercise Thursday, which was “aimed at stressing our system and ensuring that we’re ready to deliver care,” said Army Col. Susan Annicelli, commander of the DeWitt health-care network.

Doctors, nurses and other medical staff practiced treating volunteers and medical dummies for anything from routine appointments to life-threatening conditions.

“Not only is the hospital new, every piece of equipment is brand new,” Maj. Trisa Giuliani, an Army anesthesiologist, said after participating in a practice exploratory laparotomy in which the “patient” expired.

Giuliani said there was some sadness in leaving Walter Reed after eight years.

“Walter Reed was home to me,” she said. “But it’s unbelievable here, with the state-of-the-art equipment. You can feel the excitement in the hallways.”

Giuliani said the rooms at the new hospital will be able to accommodate family members of patients.

“The big difference is the ability to take care of the entire family,” she said. “Walter Reed wasn’t set up to do that.”

Commanders expressed confidence that they will be able to meet the Sept. 15 deadline imposed by BRAC for completing the move from Walter Reed to the new facilities.

“We still have some weeks of heavy lifting left,” said Lt. Gen. Eric B. Schoomaker, commander of the U.S. Army Medical Command.

Last weekend, 46 outpatient soldiers from the Walter Reed Warrior Transition Brigade were taken aboard three buses to their new barracks at Fort Belvoir, escorted by police. More will move to Bethesda this weekend.

On Aug. 31, the last 10 to 15 patients expected to still be in DeWitt will be put in ambulances for the two-minute ride to the new Fort Belvoir hospital.

Up to 150 patients at Walter Reed are to be moved by a parade of ambulances to Bethesda on Aug. 28.