A full line represents a positive yield line caused by a sagging (yield moment,so that the concrete cracks in tension in the bottom face of the slab A broken line represents a negative yield line caused by a hogging (yield moment so that tensile cracking occurs in the top face. Negative yield line Simple support 77777777772 Simple support• A full line represents a positive yield line caused by a sagging（下沉） yield moment, so that the concrete cracks in tension in the bottom face of the slab • A broken line represents a negative yield line caused by a hogging（翘曲） yield moment so that tensile cracking occurs in the top face