This pile of 3,200 crabs, “He Xie,” is a new work being shown for the first time. AP Photo/Cathy Carver, Smithsonian's Hirshhorn Museum. By: Brett Zongker, Associated Press

Chinese artist Ai Weiwei, who helped design Beijing's Olympic Stadium and has since drawn tough scrutiny for his political activism, is opening the first North American retrospective exhibition of his work in Washington.

Ai, 55, is barred from leaving China, though, after being detained without explanation for three months last year. In recent weeks, he has been fighting charges of tax evasion, and the government has moved to close his design firm. So he won't be at the opening Sunday at the Smithsonian's Hirshhorn Museum.

Artworks in "Ai Weiwei: According to What?" capture his push for free expression and his relentless questioning of authority, curators said. One 1995 photograph shows him giving the middle finger to the White House. It's also a study on perspective that Ai has repeated at the Eiffel Tower, Tiananmen Square and elsewhere.

"I always admire his questioning attitude. I think it's important for all of us to try to find the truth and where the truth is," said curator Mami Kataoka of Tokyo's Mori Art Museum, who organized the exhibit. "It's very difficult to find the truth, particularly in China."

Planning for the exhibit began years ago, long before Ai was detained for 81 days during a crackdown on dissent. The installation includes sculpture, photography, video and audio works, encompassing most of the museum.

In a statement to the Smithsonian, Ai said the exhibition was a chance to communicate with far away audiences. "It is part of a continual process of self-expression," he said.

The show is on view through February before traveling to Indianapolis, Toronto, Miami and New York City.

It includes new works created since the last major exhibition in Tokyo. One piece involves 3,200 porcelain crabs called "He Xie." The Chinese words for river crab sound like the Chinese word for "harmonious," part of the Communist Party's slogan of "the realization of a harmonious society." The term has become Internet slang for online censorship.

Several works emerged from Ai's response to the devastating Sichuan earthquake in 2008 that killed more than 5,000 children in poorly constructed schools that collapsed. One wall lists all of their names. A snake on the ceiling is made of children's backpacks in their honor. And a sculptural piece, entitled "Straight," was created from 38 tons of twisted steel from collapsed buildings.

Ai was angry that society was "forgetting what happened as if nothing had happened" in the quake's aftermath, Kataoka said.

Visitors will find a photo montage covering the gallery's walls and floors of the "Bird's Nest" Olympic Stadium under construction. There are also photographs from Ai's years living in New York in the 1980s and 1990s where he witnessed protests and government opposition and studied the work of Andy Warhol, Jasper Johns and Marcel Duchamp.

Ai's father, Ai Qing, was a famous Chinese poet. Shortly after the Cultural Revolution and Ai's birth, however, the family was exiled during China's Anti-Rightist Movement. Ai saw his father humiliated, reduced to cleaning public toilets, Kataoka said.

"He was born out of those kind of social conditions," she said. "I think it's only natural for him to question about human rights."

Ai's release from government detention last year was seen as a concession to international pressure and appeals inside the ruling Communist Party, where Ai's father is still widely revered.

Smithsonian leaders celebrated the exhibit's opening in the U.S. political capital near diplomats from more than 200 countries. Hirshhorn Director Richard Koshalek called it one of the museum's most important installations.

"The context in which this exhibition is being presented is extremely, extremely important to him and to us," Koshalek said. "I think what he's saying refers to not just China, but it refers to other places in the world where freedom of expression is threated or doesn't exist."