Senate Republicans yesterday asked President Reagan's chief trade official to investigate whether Japan is violating international agreements by refusing to let foreign companies bid for giant public construction projects, including a new $8 billion international airport in Osaka.

The investigation could be the prelude to an unfair trade complaint initiated either by the Reagan administration or by the GOP senators, said Sen. Frank H. Murkowski (R-Alaska), chairman of the 10-member Republican Senate Task Force on International Trade.

The attack on Japan's closed market for major construction projects is the latest assault on that country's barriers to foreign companies.

The Republican senators' letter to U.S. Trade Representative Clayton Yeutter is an attempt to intensify the pressure on Japan to change its policies, not only for the Osaka airport but for future public works projects.

The European Community also has complained that its highly experienced construction and engineering companies have been barred from bidding for contracts to build Kansai International Airport in Osaka.

Yeutter and Commerce Secretary Malcolm Baldrige have filed official complaints with the government of Prime Minister Yasuhiro Nakasone, and the EC is expected to do the same shortly. In addition, U.S. Embassy officials in Tokyo and consulate officials in Osaka have raised the issue.

At a Senate Foreign Relations Committee hearing earlier this month, Commerce Assistant Secretary H. P. Goldfield said that American officials have gotten a runaround from the Japanese. In Osaka they are told it is a matter for the Nakasone government, which says in Tokyo it is being handled by the Osaka airport authorities.

Murkowski quoted Japanese news accounts as saying the reason foreign competitors are barred from the project is that Japanese companies are "not quite competitive" in airport construction.

"Japan has not had the experience the United States has had" in building international airports, particularly tricky ones such as Kansai, which will be contructed on filled land three miles out in Osaka Bay, the senator said.

The official reason given by the Nakasone government for "resisting foreign participation" is that it "would cause confusion," Murkowski said.

He added that the first and last major construction project awarded to a U.S. firm was in 1965. Meanwhile, Japanese construction and engineering companies have been free to work in the United States, gaining $1.8 billion in contracts here last year.