How tall is the Anqing Bridge which opened prior to 2011?
CREATE TABLE "completed" (
  "name" text,
  "height_of_bridge_structure" text,
  "longest_span" text,
  "type" text,
  "opened" real,
  "location" text
);
SELECT "height_of_bridge_structure" FROM "completed" WHERE "opened"<2011 AND "name"='anqing bridge';