Say, I took 4 years of calculus, including differential equations, partial differential equations, theory of elasticity, theory of plates and shells, etc. In those latter 2 courses, the prof used to write partial differential equations that filled up 3 blackboards end to end. One such problem invoved calculating the stress concentration factor at a hole in the center of a plate; after 3 blackboards filled of equations, the answer for that factor was K = 3. So I memorized it. Now in 40 years worth of civil/structural engineering, I have used calculus and diffy Q maybe one or 2 times in my career. The bottom line is that while it is very important to take these calculus courses to get an understanding of what is going on, don't feel like you'll be using them day to day in the Civil Engineering field. Just get the basics down.