No, there is no way to repair a broken kiln shelf. However, you can still use the shelf pieces. Several ideas:
1) Use a tile saw to slice the shelf into horizontal sections. Use these to hold glass frit in making thick
2) Place broken shelf pieces under pottery that is decorated with runny glazes or pieces that have too much glaze. Crystalline glazes often run.
3) If the bottom of your kiln is uneven, place the broken shelf pieces in the bottom of your kiln to support posts.
4) Use the shelf pieces as smaller shelves to place around tall pieces.
5) Silver clay and enameling: Place hot pieces onto the broken shelf. It is a good fireproof surface.
6) Lay the broken shelf across two half-shelves for even support of a piece with a large base.