Unclaimed urns containing ashes of the dead are piling up by the thousands across Japan, creating storage headaches and reflecting fraying family ties and economic pressures in a rapidly aging nation.The identities of the dead, cremated at public expense, are usually known. But in most cases, relatives either refuse or don’t respond to requests to collect their remains. Burials can be costly and time-consuming, a burden on family members who may hardly know the deceased relative.The abandoned remains highlight social, economic and demographic changes in Japan, where more elderly live on welfare and families are more scattered, weakening traditional family bonds and obligations.It is a problem that is likely to grow, experts say; deaths in Japan are projected to rise from 1.33 million a year to 1.67 million by 2040, even as the overall population drops.