There is plenty of material in the Guild's Design Workbook to help with joint design. In fact it is the single best resource currently available. Recommended articles include

Frame Engineering
Joint Engineering I
Joint Engineering II
Engineered Tension Joinery
Joinery Decisions
Pegging Design
Design of Joints in Traditional Timber Frame Buildings
Experimental Evaluation of Traditional Timber Connections
Analysis of Frames with Traditional Timber Connections
Tying Joint Evolution 1690-1790
Variations on the English Tying Joint