Abstract: An access structure such as a petroleum products loading platform which includes a vertically moving work platform having guides restrained with a plurality of vertical support members to vertically guide the platform along the support members. A plurality of lifting elements are respectively connected to each of the support members and to the platform to vertically move the platform along each of the support members. A common actuatable power arrangement is connected to each of the lifting elements to cause the lifting elements to vertically move the platform a prescribed distance along each of the support members responsive to each actuation of the power arrangement. Each of the lifting elements may be a hoisting drum and cable arrangement which is vertically moveable responsive to rotation of the hoisting drum to reel in or pay out the cable.