No abstract

No abstract

The fire resistance of concrete members reinforced or strengthened with fiber reinforced polymer (FRP) materials is an extremely crucial area that needs to be investigated prior to implementing FRP composites in buildings and other structures vulnerable to fire. A review on the fire performance of fiber-reinforced polymer (FRP) materials and FRP-strengthened / reinforced concrete members is presented. The review includes the mechanical properties of various types of FRP materials at elevated temperatures (based on experimental results). The behavior of bond adhesive epoxies and the bond of FRP reinforcement are investigated under elevated temperature effects. Experimental (fire test) results and numerical studies for unprotected concrete members strengthened or reinforced with FRPs (beams, columns, slabs) including failure patterns, as well as respective results for insulated concrete members, together with the type of insulation materials are also presented. The measured evolution of temperature at distinct locations within the cross-section of the tested element and the role of insulation are discussed. Factors that significantly influence the fire resistance of FRP strengthened or FRP reinforced systems are discussed and preliminary guidelines for the efficient design of such systems in a fire environment are provided.

Structural optimisation is a topic which gathers the interest of many research teams and engineers. Its purpose is to minimise an objective function, such as the weight of a structure, subjected to certain constraints (e.g. compliance of structural members with code requirements). In this paper, optimal design (in terms of shape and sizing) of through-truss steel bridges is performed. Several cases of simply supported bridges with different spans (40m, 50m and 60m) and varying width, corresponding to one or two traffic lanes, were examined. For the aforementioned bridges, the effect of three deck types (reinforced concrete deck, fiber reinforced polymer deck and steel deck) on the weight of the truss and the total weight was investigated. Least-weight shape and sizing optimal design was executed, with the height of the truss and the cross-section areas of its members constituting the design variables of the problem. The structural analysis and design were conducted in accordance with the specifications of the Eurocodes. The influence of both the height-to-span ratio and the deck type on the weight of the truss, the total weight and the cost is discussed based on the results obtained from the optimisation procedure.

The safe operation of steel oil storage tanks is vital for the petroleum industry. Such tanks are typically thin-walled, cylindrical, with large diameters and are not mechanically anchored to the foundation. Until recently, code provisions were oriented towards the design of tanks operating at high levels of the contained liquid and emphasis was given on preventing failure modes associated with yielding of the shell (plastic limit state). Based on this concept, the majority of the existing tanks were constructed with variable shell thickness, because tensile stresses (which result majorly from hydrostatic pressure) reduce towards the top of the tank. To account for structural stability issues of the very thin upper shell courses, stiffening rings were commonly placed on their circumference. However, the stiffening arrangements of existing tanks might not be sufficient to prevent buckling of the shell when these operate at low liquid levels. Therefore, the safety of such structures has to be reevaluated. In this paper, retrofit scenarios for two representative, large-scale oil storage tanks (with diameters of approximately 88m and 47m) operating at low liquid level are proposed in order for the provisions of the Eurocodes to be satisfied. For the larger tank, which is open-top, two additional ring stiffeners were necessary to increase (by reduction of the buckling length) the circumferential buckling resistance of the higher tiers, which was critical in meeting the requirements set by the Eurocodes. The retrofit proposal for the other tank (which supports a conical roof) included the attachment of vertical stiffeners to account for the high meridional stresses developed in the thinner courses. Moreover, the attachment of three stiffening rings was suggested to further reduce the effect of comprehensive hoop stresses on shell buckling. Cost data regarding the proposed retrofit scenarios are presented. Helpful conclusions regarding the strengthening of such structures and the efficiency of the Eurocodes are drawn.