Numerical and Experimental Analysis of Fire Resistance for Steel Structures of Ships and Offshore Platforms

The requirements for the fire resistance of steel structures of oil and gas facilities for transportation and production of hydrocarbons are considered (structures of tankers and offshore platforms). It is found that the requirements for the values of fire resistance of structures under hydrocarbon rather than standard fire conditions are given only for offshore stationary platforms. Experimental studies on the loss of integrity (E) and thermal insulating capacity (I) of steel bulkheads and deck with mineral wool under standard and hydrocarbon fire regimes are presented. Simulation of structure heating was performed, which showed a good correlation with the experimental results (convective heat transfer coefficients for bulkheads of class H: 50 W/m2·K; for bulkheads of class A: 25 W/m2·K). The consumption of mineral slabs and endothermic mat for the H-0 bulkhead is predicted. It is calculated that under a standard fire regime, mineral wool with a density of 80–100 kg/m2 and a thickness of 40 to 85 mm should be used; under a hydrocarbon fire regime, mineral wool with a density above 100 kg/m2 and a thickness of 60–150 mm is required. It is shown that to protect the structures of decks and bulkheads in a hydrocarbon fire regime, it is necessary to use 30–40% more thermal insulation and apply the highest density of fire-retardant material compared to the standard fire regime. Parameters of thermal conductivity and heat capacity of the applied flame retardant in the temperature range from 0 to 1000 °C were clarified.

Mechanical Property of Beam-to-Column Connection of Steel Structures With All-Steel Buckling-Restrained Braces

To avoid brittle fracture and plastic yielding of steel beam-to-column connections under earthquakes, a new beam-to-column connection of steel structures with all-steel buckling restrained braces (BRBs) is proposed. The all-steel BRB is connected to the steel beam and column members through pins to form a new connection system. Taking the T-shaped beam-to-column connection steel structure as the research object, two structural types with an all-steel BRB installed on one side (S-type) and two sides (D-type) are considered. Theoretical equations of the connection system’s initial stiffness and yield load are derived through the mechanical models. The yield load, main strain distribution, energy dissipation, and stiffness of the connection system are investigated through quasi-static tests to verify the connection system’s seismic performance. The tests revealed that the proposed new connection system is capable of achieving a stable hysteresis behavior. At the end of loading, the beam and column members are not damaged, and the plastic deformation is concentrated in the plastic energy dissipating replaceable BRB, and the beam and column basically remain elastic. The proposed equations approximately estimated the load response of the proposed connection system. The results show that the damage mode of this new connection system under seismic loading is BRB yielding, with an elastic response from the beam-column members.