S690 High Strength Steel Research Articles

Dependence of mechanical properties of high strength steel S690 on elevated temperatures

The deterioration of mechanical properties is predominant in the design of steel structures under fire condition, as it leads to associated reduction of load bearing capacity. To understand elevated temperature dependence of mechanical properties of high strength steel S690, an experimental investigation has been carried out, using both steady state and transient state methods at temperatures ranged from 20°C to 700°C. Comparison of results with European, American, Australian and British design standards shows no current standard can safely guide fire-resistance design of steel structures with S690. Therefore the mechanical properties of S690 at elevated temperatures obtained herein are of value.

Reliability analysis of net cross-section resistance with accidental eccentricity of holes

The aim of the research was to determine reliability function of net cross-section resistance in relation to accidental eccentricity of nominally centric holes. The response surface method was used by taking into account the relevant Eurocode design provisions and reliability requirements. Within the response surface method, the central composite design method and the least square method were used with the employment of Monte Carlo simulations. The probable distributed variables such as strength fy, breadth b, thickness t, diameter d0 and eccentricity e were determined by the central composite design method. 280 different numerical simulations were set up with varying variables. A log-normal distribution for strength (fy) and a normal distribution for geometrical variables (b, t, d0,e) were employed by taking into account the coefficients of variations: Vfy=0.07, Vb,=0.005, Vl=0.05 and Vd0=0.005. In order to determine the influence of eccentricity on partial safety factor, several normal distributions with different variation factors were applied in the analysis. The influence of the edge distance of the hole e2 over d0 ratio on the partial safety factor was determined by varying mean values of variable b. For comparison, two types of steel were used: structural steel S235 and high strength steel S690. Numerical simulations of the net cross-section resistance Fu were performed with ABAQUS 6.7. The response surface for the net cross-section resistance was determined by introducing a quadratic approximation function and by applying the least square method. The partial safely factor was then (statistically) obtained by means of robust Monte Carlo simulations on the calculated response surface.

Net cross-section design resistance and local ductility of elements made of high strength steel

Extensive experimental research on net cross-section failures of plates with holes (23 tests) and bolted connections (20 tests) made of high strength steel S690 is presented. The aim was to determine their local ductility and resistance. The verification of various strength functions and the determination of an appropriate partial factor γ M was done by means of statistical analysis according to EN 1990, Annex D. Emphasis is given to the reliability of Eurocode provisions for the design resistance of net cross-sections.

Experimental behaviour of high strength steel end-plate connections

The use of high strength steel in construction has recently provided some challenges to structural engineers. One such challenge is to minimise the cross-section dimensions as the material provides higher strength, which brings great economic benefits. However, high strength steels exhibit high yield ratios and limited deformation capacity when compared to mild steel grades. This behaviour can be particularly important when structures are designed for abnormal loading conditions that produce inelastic deformations. In this situation, both members and connections have to develop sufficient ductility. The connections between members, in particular, are the regions where the material is exposed to higher deformation demands. To address these topics, an experimental investigation was undertaken of moment connections with end-plates made up of the high strength steel S690. The major contributions of this study are (i) the characterisation of the nonlinear behaviour, (ii) the validation of current Eurocode 3 specifications and (iii) the ductility analysis of high strength steel moment connections. The test results show that the tested connections satisfy the current design provisions for stiffness and resistance and achieve reasonable rotation demands.