At the end of year 2005, new AISC Specification was released that contained formulas for both Allowable Stress Design and Load and Resistance Factor Design in non-dimensional format to be used for both the FPS and SI units. In year 2010, this specification for steel structures design and the seismic provisions were updated. This specification was further revised in 2016. This book is prepared in the light of the new Specifications. AASHTO LRFD Specifications are used to present the concepts of bridge loading and the design procedure. As in the first edition, in place of explaining the various aspects of design such as checking various strength capacities, stability requirements and serviceability limits in separate chapters, complete design including all the major steps of design are presented in individual units for various types of members. It is expected that this procedure gives true picture of design process to the beginners and the practicing engineers. This book is more useful if it is used along with another publication “LRFD Steel Design Aids”, termed as Design Aids in this book. The flow charts given in different sections of this book may easily be computerized to get custom-made computer programs for personal use. International system of units (SI) is used throughout the book. Suggestions for further improvement of the presentation will be highly appreciated and will be incorporated in the future editions.