The through plate connection is a type of moment connection. The connection consist of passing two plates through the HSS column member whilst it is connection to the top and bottom flanges of the children members. It also uses shear connections to provide extra shear strength to the overall connection, the shear connection used is normally single plate connections.
The through plate connection provides additional stability and rigidity in the actual connection joint allowing it to take more moment and shear load than other connections but it does have a relatively complex method of erection which would mean it can become a rather costly connection.
Shown in the picture, the moment connection greatly increases in complexity when compared to shear connections. Normally only one type of moment connections exist in one structural space. This connection also then comes with increase calculations to ensure the connection itself is stable.