Ductile connection to improve the fire performance of bare-steel and composite frames

PurposeIn order to improve the robustness of bare-steel and composite structures in fire, a novel axially and rotationally ductile connection has been proposed in this paper.Design/methodology/approachThe component-based models of the bare-steel ductile connection and composite ductile connection have been proposed and incorporated into the software Vulcan to facilitate global frame analysis for performance-based structural fire engineering design. These component-based models are validated against detailed Abaqus FE models and experiments. A series of 2-D bare-steel frame models and 3-D composite frame models with ductile connections, idealised rigid and pinned connections, have been created using Vulcan to compare the fire performance of ductile connection with other connection types in bare-steel and composite structures.FindingsThe comparison results show that the proposed ductile connection can provide excellent ductility to accommodate the axial deformation of connected beam under fire conditions, thus reducing the axial forces generated in the connection and potentially preventing the premature brittle failure of the connection.Originality/valueCompared with conventional connection types, the proposed ductile connection exhibits considerable deformability, and can potentially enhance the robustness of structures in fire.

Development Of A Quick Design Method For Composite Concrete Slab-Over Steel I-Girder Bridges For Project Bidding

In bridge analysis, designers calculate maximum bending moment, MT, and shear force, VT, of a bridge girder under truck loading, then use available truck fraction, FT to generate the longitudinal live load effects. This Thesis presents structural analysis of different girder configurations subjected to CL-W truck loading. Girder geometries include single-, two-, three- and four-span girders. The maximum shear, deflection and moments were plotted and then used to develop equations to represent their values. Furthermore, a software was developed to perform composite steel I-girder design. The software optimizes the I-girder size based on CHBDC design procedure. Using the developed software, a parametric study was conducted to determine the required composite moment of inertia, moment of inertia of the bare steel section and steel web area to satisfy all design requirements. Empirical equations for these three properties were developed to assist bridge designers in estimating steel I-section sizes for contract bidding.

Development Of A Quick Design Method For Composite Concrete Slab-Over Steel I-Girder Bridges For Project Bidding

In bridge analysis, designers calculate maximum bending moment, MT, and shear force, VT, of a bridge girder under truck loading, then use available truck fraction, FT to generate the longitudinal live load effects. This Thesis presents structural analysis of different girder configurations subjected to CL-W truck loading. Girder geometries include single-, two-, three- and four-span girders. The maximum shear, deflection and moments were plotted and then used to develop equations to represent their values. Furthermore, a software was developed to perform composite steel I-girder design. The software optimizes the I-girder size based on CHBDC design procedure. Using the developed software, a parametric study was conducted to determine the required composite moment of inertia, moment of inertia of the bare steel section and steel web area to satisfy all design requirements. Empirical equations for these three properties were developed to assist bridge designers in estimating steel I-section sizes for contract bidding.

The effect of additive particle size on the anti-corrosion behavior of PU coating

Purpose The purpose of this study is to investigate the influence of additive particle size on the anti-corrosion behaviors of polyurethane (PU) coating. Design/methodology/approach The graphite (Gr) and poly-graphite (PGr) were used as large size additive and small size additive, respectively. The immersion test and electrochemical test were used to study the corrosion behaviors. Findings In the immersion test, the surface of the bare steel sample was corroded uniformly. However, for the steel samples with coatings, the surfaces were corroded locally. This phenomenon showed that the coating can isolate artificial sea-water and samples and then decreased the corrosion rate. Furthermore, the most severe corrosion was observed on the sample with the Gr/PU coating compared with other anti-corrosion coatings. The results of the electrochemical measurements indicated that the corrosion rate of the sample with PGr/PU coating was approximately two times lower than that of the sample with the Gr/PU coating and the sample with PGr/PU coating was hardest to be corroded. Originality/value To have a more objective and direct recognition of the particle size effect on the coating quality.

The role of chromium content in the long-term atmospheric corrosion process

The corrosion of alloy steels with different amounts of Cr was studied using electrochemical tests, wet–dry cycle corrosion, X-ray diffraction, and Kelvin probe force microscopy. The results show that the content of Cr is positively correlated with the corrosion resistance of bare steel, but the corrosion resistance of atmospheric corrosion does not show the same pattern. The atmospheric corrosion resistance of Cr-containing steel exhibits three different stages with the change of Cr element content. When the Cr content is in the range of 1–4%, the corrosion rate is high and does not change within the Cr content. As the Cr content was further increased from 4 to 7%, the corrosion rate exhibited a linear decrease and then drops rapidly when the Cr content reaches 8%. These three different corrosion rate stages are related to the influence of Cr content on Fe3O4 content in the rust layer.

Experimental study on friction performance of damaged interface in steel-concrete composite beam connected by high-strength bolt

Although traditional steel-concrete composite beam has excellent structural characteristics, it cannot meet the requirement of quick disassembly and repair in the bridge. This article presents an experimental study on friction performance of damaged steel-concrete interface in recoverable composite beam connected by high-strength frictional bolts. A total of 21 specific split tests were carried out using different concrete strength, steel strength, and surface treatment of steel. The experimental results showed that the demountable high-strength frictional bolt used in composite beam has similar performance as in the bare steel structures. The initial friction coefficient and slip stiffness were measured to be 0.34–0.47 and 52.3–116.1 kN/mm, respectively. Friction performance of damaged interface was obtained, proving that friction coefficient and slip stiffness will not decrease after the first slip damage. It is also confirmed that shot blasted steel and concrete with higher strength were more suitable in the demountable composite beam.

Effects of Sputtering Current on Electrochemical Corrosion Characteristics of Nanoscale Chromium Films Deposited by Direct Current Magnetron Sputtering

Chromium coatings are often used for surface treatment of metals and alloys. In this study, nanoscale chromium coatings were deposited on 316L stainless steel by direct current magnetron sputtering. The effects of sputtering currents on electrochemical corrosion behavior of nanochromium coatings were investigated in 0.5 M H2SO4 + 2 ppm F− solution by electrochemical methods at room temperature. Results showed that the corrosion rates for nano-chromium coatings deposited at 0.25 A, 0.35 A, and 0.4 A were lower than bare steel by more than two orders of magnitude. The chromium coatings deposited at 0.25 A were inclined to degrade in the electrolyte after long-term immersion in the electrolyte, due to lesser coverage of passivity film on chromium coating. Moreover, the chromium coatings deposited at 0.3 A and 0.4 A exhibited excellent corrosion resistance due to formation of a continuous, compact and protective passive film.

Numerical Investigation on the CFRP Strengthened Steel Frame under Earthquake

Steel structures are commonly used in seismic regions of the world because of its strength and ductility. However, these structures are still prone to damage during an earthquake. With this risk of seismic damage, the strengthening of steel structures is a major concern in order to resist the dynamic loads resulted from earthquakes. This report investigates the potential for the use of Carbon Fibre Reinforced Polymer (CFRP) to strengthen the rigid steel frame under a real earthquake load. This research will be undertaken using Strand7, a finite element (FE) analysis software. To validate the accuracy of this research, the finite analysis results have been compared to the available experimental study by the Authors. First, both FE models of a five-story bare steel frame and CFRP strengthened steel frame has been developed. Then the predicted numerical results of bare steel frame and CFRP strengthened steel frame under earthquake excitation are compared. The results indicated an increase in the seismic performance of the steel structure due to the strengthened with CFRP. The CFRP strengthened steel frame showed 15% less tip deflection compared to bare steel frame. Further analysis on the strengthening capabilities of higher thickness CFRP was performed to assess the effect of the thickness of CFRP and the higher thickness CFRP showed better seismic performance compare to normal thickness CFRP by reducing 34.38% of tip deflection.

Effect of alloying elements in Fe-based hardfacings to improve the abrasive wear behavior of ploughshares

Generally, during soil tillage it is seen that farmers complain about the higher wear rate of agricultural implement. Wear of cultivator shovels is one of the major problem faced by farmers in the agricultural sector. Any improvement in the life of ploughshares will be of great significance to the farming sector. The aim of the present work is to improve the life of cultivator shovels by way of hardfacings by shielded metal arc welding process. The wear behavior of bare (EN-47 steel) and four different hardfacings (H1, H2, VB, and LH550) having different chromium content (i.e. 0.86% Cr, 2.4% Cr, 3.19% Cr, and 6.72% Cr) were investigated with regard to wear behavior. A test was conducted on a 60 ha area of the wheat field after harvesting (latitude 30.121207, longitude 75.009159). During the time of cultivation soil was dry and hard. Wear behavior of bare and hardfaced steel was analyzed in terms of weight loss (g/ha) and by wear resistance indices. Techniques like optical microscopy, scanning electron microscopy, X-ray diffraction analysis were used for testing. The hardfaced steel has shown significantly better wear behavior in comparison to bare steel except H2. Wear of ploughshares according to cultivated area was found to be 3.459 g/ha for regular, 3.41 g/ha for H1, 4.267 g/ha for H2, 2.553 g/ha for VB, and 1.993 g/ha for LH550 hardfacing. The WRIs of different hardfacings, i.e. H1, H2, VB, and LH550 were found to be 1.014, 0.81, 1.354, and 1.735.