Virginia Republican Sen.-elect Paul S. Trible today hailed his election as a triumph for Reaganomics and said that he favors reducing future Social Security benefit increases--a position he didn't disclose in his campaign.

At his first news conference since his narrow victory, Trible also pledged to vote against any proposals that deviate from administration economic policies -- even if they are offered by the Senate Republican leadership.

"I believe that in Virginia we see broad support for the initiatives of this administration and this Congress," declared the 35-year-old Tidewater congressman. "I believe we're doing the right kinds of things . . . and I believe those policies will work."

Trible, appearing relaxed and chipper despite what he called his "traditional postelection" head cold, offered his comments to reporters at the John Marshall Hotel here as nearly 100 supporters cheered and loudly applauded his answers. As he outlined his plans to succeed retiring independent Sen. Harry F. Byrd Jr., Trible mostly stuck to the generalities of his campaign speeches, promising "to always do what is right for America and Virginia."

Although Trible had been reluctant to discuss the politically touchy issue of Social Security benefits during the campaign, he said today he would support curtailing of future increases rather than increasing Social Security taxes. "We will have to restrain somewhat the increases in Social Security benefits paid in the out future years," he said. "I'm not saying people will receive less than they are receiving today; people will receive more than they are receiving today. But perhaps those increases will be restrained."

Trible previously had said only that the question of how to shore up the deficit-ridden retirement system required a "bipartisan consensus" that could not be forged until after a national commission issues its report on reforming the system. Trible's statement today calling for a restraint on cost-of-living adjustments was "fresh material," Trible spokesman Neil Cotiaux said.

"He Trible believed that Social Security is not an issue that should be discussed in the political arena," Coutiaux said.

The senator-elect's statement drew an angry retort from one leading Democrat, state Sen. L. Douglas Wilder of Richmond. He called it an example of Trible's "callous misrepresentations" during the campaign. "If he felt that way before, why didn't he say it?" Wilder asked. "But he didn't because he knew he wouldn't have been elected . . . . Unfortunately we're stuck with Paul Trible for six years."

Cotiaux later denied that Trible had withheld his Social Security views to avoid the political fallout. He noted that Trible had said during the campaign that he wanted to await the recommendations of the president's National Commission on Social Security Reform and that the commission this week had released a list of possible options.

What Trible today called "the message of the people of Virginia in 1982" means that he will not support an emergency public works jobs bill that is now being drafted by some Senate Republicans, he said.

That proposal, which could provide up to 200,000 short-term jobs repairing decaying highways and bridges, was devised this week by Senate GOP leaders reportedly worried that the country's 10.4 unemployment rate was chiefly responsible for overall Democratic gains in last week's elections.

"The answer does not lie in creating expensive, short-term wasteful employment," said Trible, categorically rejecting the idea.

Virginia's senator-elect also offered a number of thoughts on his 34,783-vote victory over Democratic Lt. Gov. Richard J. Davis. He attributed his election to the commitment of Virginians to "conservative principles," his strong support in his own normally Democratic 1st Congressional District where he won nearly 60 percent of the vote, and to a strong "grass-roots" Republican organization.

Asked why he received more than $500,000 in political action committee contributions, mostly from defense contractors, oil and gas companies and other large corporate interests, Trible shot back: "Because I'm a free enterprise Republican and I believe in a strong military."

In his only trace of bitterness, Trible also said he ended up benefiting from a hard-hitting series of Davis radio commercials that attacked his six years in the House of Representatives. Trible said the ads "backfired."

"They the voters were offended by the campaign tactics of my opponent," he said. "My opponent lost this election in part because he never gave the people of Virginia a reason to vote for him. Rather he spent all his time and energy and money attempting to tear down my record."