WASHINGTON – Housing and Urban Development Secretary Ben Carson proposed far-reaching changes to federal housing subsidies Wednesday, tripling rent for the poorest households and making it easier for housing authorities to impose work requirements. Carson’s proposals, and other initiatives aimed at low-income Americans receiving federal assistance, amount to a comprehensive effort by the Trump administration and Republicans in Congress to restrict access to the safety net and reduce the levels of assistance for those who do qualify. The ambitious effort to shrink federal assistance has been dubbed “Welfare Reform 2.0,” after Bill Clinton’s overhaul of the welfare system in 1996.