What is an effective way to structure the conclusion?
repeat all of the topic sentences
reference the introduction strategy
introduce the thesis statement
develop the argument

I would say that structuring the conclusion in an essay would require one to reference the introduction since in the introduction the goal of the article should be presented and the main ideas should also be set forth, to be examined in the body of the article. The conclusion structure, then, should follow the structure or order in the introduction and draw conclusions according to the logical sequence of the main ideas.