Can I use the work in my journal/conference publications as chapters in my dissertation?
Supplementing the answer from abatkai:
The rules likely vary by field also. In chemistry, converting previously published papers into a Sandwich Thesis is generally accepted and commonplace. My thesis contained a chapter that was prefaced &quot;Portions of this chapter were previously published as (citation), and have been reproduced with permission. Copyright is held by (publisher of the journal).&quot; This was followed by further copyright information and the statement required by the publisher. My institution also required that I submit paperwork in support of my use of published and copyrighted material.
In addition to consulting your adviser and your institution, you should consult the journals in which you publish. Many have policies in place for this. For example, from the American Chemical Society's copyright faq:

The current ACS Journal Publishing Agreement covers several permitted uses by authors... Permitted uses of all versions include:

Use in theses and collections of your own work