Frequently in the engineering design economy is sacrificed because of a lack or knowledge of the behavior of the structure. Because of the lack of information on the restraint values of beam-column connections, the beam is often over designed by failing to take advantage of partial continuity. If the degree of restraint of a beam-column connection can be determined, the optimum beam moment can be derived and then an optimum or economic beam can be designed. This thesis is mainly concerned with the effective analysis and design of a particular type of semi-rigid connection between longspan joists and columns. It is also an attempt to establish a correct technique for testing full size longspan joists and column connections. Although not commonly utilized in industry, in which longspan joists most frequently are used as simple-supported beams, the longspan joists have a degree of negative moment capacity. If this negative moment capacity can be utilized, a more efficient and economical building frame can be obtained. This thesis is also an attempt to analyze and determine the magnitude of the desired negative moment capacity of four representative longspan joists. A proposed semi-rigid connection based on this negative moment capacity is designed. Then the full size representative longspan joists are assembled by the semi-rigid connections to the full size representative columns. The four test sections were fabricated and tested by the author in the Engineering Mechanic Laboratory at the Virginia Polytechnic Institute. The tests indicated that the proposed connections vere quite satisfactory. / Master of Science