Form-finding of arch structures

In this thesis, the optimal shape of two-pin arches of constant cross-section is found analytically using a novel form-finding technique. To find the purely compressed arches built of masonry and concrete material, the state of static equilibrium is applied. As the main finding, the momentless two-pin arch shape is derived for the arches with any span-to-height ratio subjected to its self-weight (SW) and uniformly distributed load (UDL). The contribution of using momentless arches is shown through comparing their maximum displacements to those of parabolic shape. The first failure of the cross-section of the momentless and parabolic arches was then compared for the same loading. This work is conducted practising the knowledge of arch response to loading as a function of the chosen form. In this regard, a comprehensive study of the behaviour of different arch shapes considering different ratios of uniformly distributed load to self-weight (UDL:SW) is also carried out. The ideal common arch shape is investigated for minimum combined axial and bending stresses using the commercial software GSA. The optimal range of span-to-height ratio of common two-pin arch shapes is also suggested. In general, the best arch performance is exhibited for the parabolic and catenary arch with span-to-height ratios between 2–4 when UDL:SW≥1 and UDL:SW<1 respectively. However, the circular arch demonstrates the least desirable performance with the optimum range of span-to-height ratio between 4–6. Moreover, approximate methods of two-pin arch analysis are evaluated, including the masonry design method and virtual work method suggested by Megson (2006). The effect of the assumptions made by these methods on the result of analysing two-pin arches is investigated through comparing their results to those obtained by the second theorem of Castigliano, including full structural action and the GSA results

Influence of the degree of utilization on the structural behaviour of stainless steel frames subject to fire

Stainless steel is known to have a better behaviour at elevated temperatures than carbon steel. This, combined with its aesthetic appeal and corrosion resistance, makes stainless steel structures an attractive alternative to carbon steel structures. However, EN 1993-1-4 does not establish de-sign rules associated with global analysis of stainless steel frames and EN 1993-1-2, devoted to carbon steel, provides a conservative approach for the fire design of stainless steel structures. Hence, current European codes do not provide efficient design guidelines for stainless steel frames subject to fire and therefore the response of this type of structures should be assessed by means of experimental tests and/or numerical analyses. The main objective of the paper is to assess the nonlinear structural response of stainless steel frames subjected to fire, focusing the investigation on the influence of the degree of utilization. A comprehensive numerical analysis on Class 1 and Class 3 stainless steel frames and Class 1 carbon steel frame subjected to fire is carried out varying the degree of utilization. Calibration of the FE models has been carried out as a part of a study of transient thermo-mechanical models, which are needed to assess the response of stainless steel frames subjected to fire.The authors acknowledge the funding from the MINECO (Spain) un-der Project BIA2016-75678-R, AEI/FEDER, UE “Comportamiento estructural de pórticos de acero inoxidable. Seguridad frente a ac-ciones accidentales de sismo y fuego”.Peer ReviewedPostprint (author's final draft

Elevated temperature performance of restrained stainless steel beams

This paper reports the results of a numerical investigation into the response of axially restrained austenitic stainless steel beams in fire, where in addition to the degradation of strength and stiffness at elevated temperatures, the influence of thermally induced stresses, are also included. The finite element (FE) programme ABAQUS has been used to model austenitic stainless steel welded I-section beams of different axial end restraint stiffness subjected to fire. The FE models are firstly validated against a selection of literature test data, which are shown to accurately capture the effects of restrained thermal deformations with a high degree of accuracy, and then used to perform parametric studies to further explore the structural behaviour in fire. A simplified analytical model for predicting the restraint axial force-temperature response is presented and validated against the numerically obtained results. The numerical models and the simplified analytical model allow the influence of frame continuity to be explicitly considered in design of stainless steel members in fire to quantify the required strength and ductility demands on connections for catenary action to develop. Comparisons with carbon steel beams demonstrate that while austenitic stainless steel beams show similar stages of behaviour in fire, they are capable of withstanding higher temperatures prior to the onset of catenary action, while developing similar levels of maximum tensile catenary force to carbon steel beams, despite the higher thermal expansion of the material

Influence of the degree of utilization on the structural behaviour of stainless steel frames subject to fire

Stainless steel is known to have a better behaviour at elevated temperatures than carbon steel. This, combined with its aesthetic appeal and corrosion resistance, makes stainless steel structures an attractive alternative to carbon steel structures. However, EN 1993-1-4 does not establish design rules associated with global analysis of stainless steel frames and EN 1993-1-2, devoted to carbon steel, provides a conservative approach for the fire design of stainless steel structures. Hence, current European codes do not provide efficient design guidelines for stainless steel frames subject to fire and therefore the response of this type of structures should be assessed by means of experimental tests and/or numerical analyses. The main objective of the paper is to assess the nonlinear structural response of stainless steel frames subjected to fire, focusing the investigation on the influence of the degree of utilization. A comprehensive numerical analysis on Class 1 and Class 3 stainless steel frames and Class 1 carbon steel frame subjected to fire is carried out varying the degree of utilization. Calibration of the FE models has been carried out as a part of a study of transient thermo-mechanical models, which are needed to assess the response of stainless steel frames subjected to fire.<br/