GENERAL Structures shall be designed to carry the following loads and forces: Dead load. Live load. Impact or dynamic effect of the live load. Wind loads. Other forces@ when they exist@ as follows: Longitudinal forces; centrifugal force; thermal forces; earth pressure; buoyancy; shrinkage stresses; rib shortening; erection stresses; ice and current pressure; and earthquake stresses. Provision shall be made for the transfer of forces between the superstructure and substructure to reflect the effect of friction at expansion bearings or shear resistance at elastomeric bearings. Members shall be proportioned either with reference to service loads and allowable stresses as provided in Service Load Design (Allowable Stress Design) or@ alternatively@ with reference to load factors and factored strength as provided in Strength Design (Load Factor Design). When stress sheets are required@ a diagram or notation of the assumed loads shall be shown and the stresses due to the various loads shall be shown separately. Where required by design conditions@ the concrete placing sequence shall be indicated on the plans or in the special provisions. The loading combinations shall be in accordance with Article 3.22. When a bridge is skewed@ the loads and forces carried by the bridge through the deck system to pin connections and hangers should be resolved into vertical@ lateral@ and longitudinal force components to be considered in the design.