This book addresses the steel structures design according to procedures and provisions set in the Spanish Building Technical Code (CTE DB-SE-A). A large collection of worked examples develop in a practical way the principles and requirements that will provide safety and serviceability to most of the steel structures for buildings. Members under tension, compression and bending are studied in order of increasing complexity, including flexural buckling and lateral-torsional buckling phenomena. Finally, step by step procedures for the design of bolted and welded connections are given, including column bases design. All tables and mathematical expressions needed to follow every step of each worked example are provided in this manual. Additionally, a final chapter containing some past papers has been included in order to prove useful as a textbook in schools of architecture or structural engineering.