This textbook covers the introduction to this very interesting field of structural mechanics on a bachelor of science level. Theory and application are directly combined by the use of numerous examples. These will clarify all steps involved and this approach is highly appreciated by students. Good knowledge of statics and strength of materials is a prerequisite to the use of this textbook since in the examples both topics are frequently used to strengthen the overall knowledge of students and to use well known situations in combination with new solution techniques such as virtual work, Clapeyron's theorem, Castigliano's theorem and the principle of minimum potential energy. To avoid laborious computations the use of computer algebra systems like MAPLE is used and also stimulated. In this way the work and energy methods become very practical and will enhance student's knowledge with less work to do.Besides 'work and energy methodes' the second major topic of this textbook is about 'influence lines'. This part can be used separately from the first part but of course the topics 'work' and 'influence lines' are closely related. Influence lines for both statically determinate and statically indeterminate structures are treated. The principle of Müller-Breslau is explained for force quantities resulting in a very powerful and fast procedure to find the shape of influence lines. Maxwell's reciprocal theorem is used to explain how to draw influence lines for displacement quantities.Hans Welleman is a civil engineer who teaches structural mechanics at Delft University of Technology. This textbook originates from his Dutch lecture notes and is not only of interest for students at a bachelor level but also for engineers in practice who want to have more mechanical background and clear examples in application.