Hoping to better compete with arch-rival Costco Wholesale (COST, +1.12%) and Amazon.com, Sam’s Club said on Wednesday that it’s now offering free shipping for many items to its premium members as part of a restructuring to its membership programs. The bulk retailer, a unit of Walmart Inc (WMT, +0.35%), says that the bulk of items it sells online will qualify and that there will be no minimum order size for customers who have a “Plus” membership, which costs $100 annually. Exceptions will include merchandise that is only available for curbside pickup such as fresh and frozen food (groceries account for...