The paper introduces the principles of displacement-based plastic design (DBPD) and its applications to the efficient design of parallel chord steel vierendeel girders under normal nodal forces. A simplifying assumption has been made that the mathematical model is composed of imaginary, pin connected modules that fit within the bays of the prototype. The use of this modeling concept in conjunction with the applications of the uniform strength theory leads to the development of an algorithm that is ideally suited for manual, minimum weight design of steel vierendeel girders under any distribution of vertical nodal forces. The resulting solutions are exact and unique and lend themselves well to DBPD and minimum weight treatment. In DBPD which is akin to performance control, member strengths and stiffnesses are assigned rather than tested. Several generic examples have been provided to illustrate the applications of the proposed design procedures. The numerical results of these examples have been verified through long hand and computer methods of analysis. An extensive proof of the proposed method of approach has been provided in the "Appendix".