PHILADELPHIA, SEPT. 17 -- With floats and flags, bells and balloons, the city that is the birthplace of the Constitution today paid a fanfare-filled tribute to the signing of the document that has guided the nation for 200 years.

At 4 p.m., the moment in 1787 when the delegates had finished affixing their names to the four-page blueprint for self-government, former chief justice Warren E. Burger rang a replica of the Liberty Bell, setting off a round of simultaneous bell-ringings throughout Philadelphia, in the capitals of the 50 states, and at U.S. diplomatic missions and military installations around the world.

Burger, who was joined at the ceremony by 39 descendants of the original signers, said the framers "had the idea of three branches of government -- the separation of powers -- so government could pull the people and not push. That's the difference between the government created here and all other governments before 200 years ago."

Hours earlier, President Reagan, framed by a shield of bullet-proof glass and a statue of George Washington, described the Constitution as having been "born in crisis" when the fledgling nation was beset by a high wartime debt, secessionist sentiment and quarreling among the 13 disparate states.

But, he said, "the vision of democratic government" that had been with the Declaration of Independence 11 years before enabled the delegates at the Constitutional Convention "to rise above politics and self-interest," forever forging the states into one nation.

"In a very real sense, it was then, in 1787, that the revolution truly began," he said before a crowd of 2,200 dignitaries and guests at Independence Hall, where both the Declaration of Independence and the Constitution were signed.

In his speech, Reagan did not refer directly to the confirmation hearings on Supreme Court nominee Robert H. Bork, who has argued that judges must follow the intent of the framers of the Constitution when deciding cases.

But Reagan observed, "Checks and balances, limited government -- the genius of our constitutional system is its recognition that no one branch of government alone could be relied on to preserve our freedoms . . . . And that is why the judiciary must be independent. And that is why it also must exercise restraint."Parade and Protests

Morning thunderstorms made an uninvited appearance at the parade that marked the beginning of Constitution Day, dampening the flags, tricorn hats and banners of an estimated 20,000 partcipants, but not the spirit of some 250,000 spectators, a more modest turnout than organizers had predicted.

Hundreds of protesters exercised their First Amendment rights by both joining the official parade and demonstrating on the sidelines. Although five people were arrested by U.S. Park Police for trespassing while attempting to give Reagan a list naming persons killed in Central America, there were no crowd disturbances, police said.

The $3.5 million parade wound through a two-mile route of downtown Philadelphia in three parts. "The Grand Federal Procession" that was held in 1788 to celebrate the Constitution's ratification by the first 10 states got under way at 9 a.m. while a fife and drum corps played "Yankee Doodle Dandy" and the Mormon Tabernacle Choir sang the "Star-Spangled Banner."

Floats depicting such colonial-era occupations as carpentry, blacksmithing and shipbuilding traveled in horse-drawn carriages, while bakers distributed biscuits wrapped in wax paper to the cheering crowds.

The second parade segment was a stunning, visual representation of the Constitution's preamble. Five state Miss America winners and cowboys on horseback accompanied the "In Order to Form a More Perfect Union" section, while athletes, construction workers and entertainers riding floats demonstrated "Promote the General Welfare."

The crowd's enthusiasm was not reserved for the spectacular. The hundreds of soldiers and military officers who marched through the streets celebrating "Provide for the Common Defense" drew the most applause from the flag-waving onlookers.

In between, college bands from around the country, including the University of Maryland, high-stepped down the rain-slick parade route.

"I've been to a lot of parades but this one was special. It had so much meaning," said Milly Faust, a retired nurse from Philadelphia. "I became very emotional when the Vietnam veterans and the Medal of Honor winners went by."

The final segment was "The Parade of America's People," which afforded participants the opportunity to express both their appreciation for and their quarrels with the way the Constitution has been applied. There were banner-carrying representatives of ethnic groups and outspoken members of such organizations as the Sierra Club, who called for an end to the use of nuclear power, and the Pledge of Resistance, which advocates an end to U.S. intervention in Central America.

Organizers said that the nationally broadcast extravaganza went off as planned, except for one notable exception.

The bell that was placed in the tower of Independence Hall during the nation's Centennial pealed three times during the president's speech. Park rangers, signaled by the release of hundreds of doves, were set to ring the bells at the moment Reagan concluded his remarks. But dozens of the birds escaped five minutes too soon, putting the park rangers in the tower into action.

The president continued speaking while the bell rang, and after the doves were released on cue there was a slight pause, prompting Reagan to remark, "Maybe that's all they were going to ring it."

The parade also caused several logistical problems for many local residents, who had been told in advance that several main streets would be closed. A nurse at Pennsylvania Hospital tried to push her way through the crowd to get to work, but police would not let her cross Chestnut Street. Minutes later, however, they allowed retired Philadelphia 76ers basketball star Julius Erving to pass.

Tourists who had filled area hotels within a 30-mile radius also ran into delays. Rosemarie Kling, an office assistant from Falls Church visiting her family here, said, "The public transportation fouled us up. Our trolley car never came, then we couldn't find a place to put the car and had to walk."

Following the parade, about 150,000 people took the celebration to the Delaware River for a giant picnic at Penn's Landing. There, the crowd munched on hoagies and hot dogs while Pennsylvania Gov. Robert Casey, foreign diplomats and Willard G. Rouse III, chairman of the nonprofit organization that had arranged the festivities, dined on a luxury cruise ship that sailed in for the event.

Constitution Day was the culmination of a year-long bicentennial celebration that city leaders say they hope will allow Philadelphia to improve its image in the wake of last year's July 4 strike by garbage collectors and the 1985 firebombing of the headquarters for the radical group known as MOVE, which resulted in the deaths of 11 people.

The city spent $100,000 to spruce up its convention center, where such show business figures as Barry Manilow, Patti LaBelle, Rich Little and Cicely Tyson this evening filmed a "Constitutional Gala" that was broadcast nationwide tonight.

Many downtown office buildings were dressed in red, white and blue bunting today in honor of the occasion, and the Benjamin Franklin Bridge, which links the city to Camden, N.J., was lit permanently tonight using funds raised from local businesses. A Forum for Mayor Goode

The hoopla also provided a visible forum for Mayor W. Wilson Goode, who is embroiled in a hard-fought reelection campaign with former mayor Frank L. Rizzo. Although both candidates had been asked by the parade's organizers to keep their campaigning away from the festivities, Rizzo was among those who marched in the parade,

Members of the Pledge of Resistance, part of a national network opposing U.S. intervention in Central America, staged a protest rally opposing aid to the Nicaraguan contras at the Constitution Pavilion following Burger's appearance.

The festivities ended tonight with the bridge lighting, a tall ship flotilla and an 18-minute fireworks display over the Delaware River. About 250,000 spectators carried portable radios blaring "America the Beautiful" and "God Bless America" while the rockets, launched from river barges, exploded.

"I'm sure if the Founding Fathers had planned to party, this would have been it," said Rick Gimello, a Philadelphia native.

Afterwards, the noisy celebrants poured into the narrow streets of Philadelphia's historic district, pausing to cheer and whistle at passing cars.

"I feel very lucky to be an American," said Robert Lendy, 29, an actor from Philadelphia. "I think despite all our troubles, it's the best place you can live with all the freedoms we have."

Elaine Furniss, a first-grade teacher from Magnolia, N.J., who was dressed in red, white and blue, said, "The thought occurred to me: 200 years ago how brilliant they were, really, to come up with something that has lasted for 200 years, will last and has made us what we are today." Staff writers Howard Kurtz and Marianne Yen contributed to this report.