Complex sentence: In a modern pole built office building or other buildings requiring interior walls and subdivisions, interior girts would usually also be added, each a bearing member, sharing and carrying the weight of interior walls and mountings to the posts.
Split into simpler sentences: In a modern pole built office building, or other buildings requiring interior walls and subdivisions, interior girts would usually be added. Each girt is a bearing member, sharing and carrying the weight of interior walls and mountings to the posts.