Microbiologically influenced corrosion (MIC) of S32654 (654SMO) super austenitic stainless steel (SASS) by acid producing bacterium (APB), Acidithiobacillus caldus SM-1, a strain of sulfur-oxidizing ...bacteria (SOB) used in biohydrometallurgy field, was investigated using electrochemical measurements and surface characterizations during a 14-day immersion test. The results indicated that S32654 SASS was susceptible to MIC by APB, and A. caldus SM-1 was capable of producing an aggressive acidic environment underneath the biofilm, resulting in the dissolution of the passive film and severe pitting attacks against S32654 SASS, which is commonly regarded as a corrosion resistant material.
•The MIC behavior of S32654 SASS in the presence of Acidithiobacillus caldus SM-1 was investigated.•The sulfuric acid produced by A. caldus SM-1 led to a severe MIC attack against S32654 SASS.•The biogenic H2S may result in the formation of MoS2 under the biocatalysis.
•A total of 196 new concrete-filled ferritic stainless steel tubular (CFFSST) joint results are reported.•CIDECT provisions exhibit remarkable scatter predictions for the CFFSST joints.•Existing ...design rules are generally not accurate for the CFFSST joints.•Improved design rules are proposed to predict the capacities of CFFSST X-and T-joints.
The behaviour and resistances of concrete-filled ferritic stainless steel tubular (CFFSST) joints were studied and presented in this paper based upon experimental and numerical investigations. A test program was firstly undertaken on a series of X- and T-joints with square and rectangular hollow section (SHS and RHS) chords. The stainless steel SHS/RHS tubes were cold-rolled from EN 1.4003 ferritic grade sheets, and the specimens were in-filled with either normal or high strength concrete. The experimental study including the detailed material properties, joint test setups, test procedures and results is reported. Numerical models were also developed and verified against the CFFSST joint test results, and followed by a parametric study generating further numerical results over a wider range of key joint parameters. The obtained experimental and numerical CFFSST joint capacities were compared with existing design recommendations as per the CIDECT Design Guide and design rules proposed by previous researchers. The comparison results indicate that the existing provisions are not capable of predicting the capacities of the investigated composite tubular joints in an accurate and reliable manner. Hence, modified design rules are put forward in this paper for the design of CFFSST joints.
The global shortage of zinc mines makes the extraction of zinc from zinc-containing wastes a hot research topic. Most kinds of steel mill dust (SMD) cannot be directly returned to the ironmaking and ...steelmaking processes due to their zinc content. A large amount of SMD produced during steelmaking has become a major challenge for steel plants due to environmental pollution, health issues and land scarcity. Lots of processes for recovering metals from SMD have been developed to comprehensively utilize them and solve these environmental problems. Zinc in SMD can be recovered by these technologies, and the residue can be used as raw material for ironmaking. In this work, the sources and characteristics of SMD from different processes were analyzed firstly. Then, the mechanisms of physical, hydrometallurgical, pyrometallurgical and pyrometallurgy–hydrometallurgy combined processes for SMD disposal are presented, and these methods are compared in terms of energy consumption, process complexity and industrial application. Finally, suggestions and prospects for utilization of SMD are put forward.
•The seismic behavior of two reinforced concrete (RC) walls with openings on scale of 1/3 accompanied by steel reinforced concrete (SRC) was investigated.•The walls behavior was assessed to determine ...their patterns of cracking failure mode, loading capacity, strength, and stiffness and dissipated energy with respect to the generated deformations.•After performing the loading test in the forms of lateral cyclic load as well as constant axial gravity load, the results of walls’ cyclic behavior, walls’ strength and stiffness degradation indexes, walls’ cumulative energy, and walls’ ductility were extracted based on displacement controlled and compared. Then, by means of FEM, the numerical analyses of both walls were performed.•The backbone curves for the FE models were then compared with the experimental diagrams and a desirable agreement between the results was observed.•This study can be useful in applied structural engineering because of applying eccentric braces at openings of a reinforced composite shear wall.
Reinforced concrete shear walls with the steel reinforced concrete frames is a common lateral force resisting structural system that is applied high-rise steel buildings in various forms. In this study, seismic behavior of two reinforced concrete (RC) shear walls with openings accompanied by steel reinforced concrete (SRC) on scale of 1/3 were investigated. One of the shear walls consisted of a steel truss reinforced concrete (STRC) with a specified eccentricity in each story level and its end was connected to the bracing’s steel beam. Both of the shear walls were coincidentally subjected to specific constant gravity load and cyclic load. Behavior assessment of shear walls included determination of the failure mode cracking pattern, loading capacity, strength, stiffness and dissipated energy with respect to generated deformations. Results revealed that the shear wall with encased steel brace (ESB) was more effective in terms of all the mentioned parameters compared to SRC wall. In the following, pushover curves for shear walls were investigated using finite element (FE) models and confidentiality of analytical models and prediction of behavior of these walls were verified based on real prototypes. Finally, effects of axial gravity load variations on FE models of both shear walls were evaluated. This study can be useful in applied structural engineering because of applying eccentric braces in openings of a reinforced composite shear wall.
In the past decades, the steel industry has experienced a rapid growth in the use of intumescent coatings for protecting load-bearing steel structures in the event of a fire. The onset of swelling is ...key for assuring the effectiveness of thin intumescent coatings for providing thermal insulation to the steel substrate during fire. The study presented herein investigates the onset of swelling for a commercially available thin intumescent coating applied on steel plates and exposed to a wide range of heating conditions. Experiments were performed using an array of radiant panels for controlling incident radiant heat flux at the exposed surface of coated steel samples. Within the scope of this research study, the onset of swelling was defined based on two conditions: (1) visual observation of swelling during heating or (2) time-history of the steel temperature. Research outcomes derived from this work defined a threshold for the onset of swelling in terms of steel and coating temperatures and it concluded that the onset of swelling is directly influenced by the heating conditions at the exposed surface and the original applied dry film thickness.
The steel tube confined concrete (STCC) column piers of marine structures have been proposed in recent years. The main advantages of STCC piers include the convenient construction process and ...improved core concrete strength. This research presents an experimental investigation on stainless steel tube confined concrete (SSTCC) column piers subjected to axial loading. Thirty two specimens were prepared and tested. Test variables included section shape, steel tube thickness, and concrete strength. Failure modes, axial ultimate compressive strength, strain characteristics, rigidity, confinement effect, and ductility were comprehensively investigated. Test results demonstrated that the main failure modes for circular and square specimens were concrete shear failure and steel tube fracture caused by concrete deformation, respectively. The axial compressive ultimate strength was affected by the tube thickness and concrete strength. The ultimate strength increased with the increase in the confinement factor, and the increasing ratio of the circular specimens was five times to that of square specimens. The differences in axial ultimate compressive strength of SSTCC column piers, carbon steel tube confined concrete column piers, and concrete filled steel tube column piers were also analyzed. Increasing tube thickness could increase the ductility and rigidity of the specimens. Moreover, axial ultimate compressive strengths were calculated and discussed based on different calculation models.
•Axial compression behaviors of stainless steel tube confined concrete (SSTCC) column piers were experimentally studied.•The differences in failure modes, ultimate strength, strain, rigidity, confinement effect, and ductility were discussed.•The differences in axial strength of SSTCC column piers, CSTCC column piers, and CFST column piers were analyzed.•Axial ultimate compressive strengths were calculated and compared using different calculation models.
In this research, the hot deformation behavior and dynamic recrystallization (DRX) of strategic Nb and V‐bearing high‐Mn steels are investigated. Therefore, the hot compression tests are performed at ...temperature range of 850–1150 °C with temperature interval of 100 °C and strain rates of 0.001, 0.01, 0.1, and 1 s−1. The peak stress, temperature, and strain rate for steels are related by the hyperbolic sine function and the average activation energies for high Mn‐steel, V‐bearing steel and Nb‐bearing steel are obtained 495, 510, and 433 kJ mol−1. The peak stress‐temperature plots show the higher peak stress for Nb bearing steel due to finer initial grains and the presence of NbC precipitates in microstructure. Microstructure results show that DRX as necklace structure is the main mechanism of work softening during process for steels whiles the start of DRX for Nb‐bearing steel is occurred at lower strains than other steels.
In this research, the hot deformation behavior and dynamic recrystallization (DRX) of strategic Nb and V‐bearing high‐Mn steels are investigated at temperature range of 850–1150 °C. Results show that DRX as necklace structure is the main mechanism of work softening during process whiles the start of DRX for Nb‐bearing steel is occurred at lower strains than other steels.
AbstractCollision of vehicles into RC bridge columns can result in significant damage to individual bridge components, leading to partial or full collapse of the entire bridge. Among various ...alternatives to RC columns, concrete-filled steel tubes (CFSTs) have received growing attention because of their rapid construction, reduced labor requirement, and reasonable material cost. Despite the promise of this alternative, however, there is a gap in the existing literature concerning the measures that can be used for the analysis and design of this important category of bridge columns subjected to impact loads. To address this gap, a detailed investigation is conducted in the current study, using a set of impact simulations. For this purpose, representative finite-element (FE) models are developed and validated with the experimental test results. To make a direct comparison possible, the numerical simulations include both CFST and RC columns under a range of vehicle impact scenarios. The structural performance is evaluated using a comprehensive set of measures, including peak dynamic force (PDF) and equivalent static force (ESF). On establishing the necessary metrics, the current study provides a systematic effort to examine the contribution of the main analysis and design parameters to the impact response of the columns under consideration. Based on the simulation results, the sufficiency of the current specifications is evaluated, and a generalized equation is proposed to predict the ESF for CFST columns.
The thermomechanical interactions between two different regions with different carbon contents during cooling from the austenite single phase condition was studied with a sandwich-like clad sheet. ...The clad steel with a layered structure where a 0.65%C high-carbon steel sheet was sandwiched by 0.05%C low-carbon steel sheets was prepared. The benefit of this clad structure for this study is that any fraction of the composed layers can be fabricated artificially with the constant carbon content in both component layers. In the experiments, the clad sheets were prepared by plain strain compression at 900 °C for welding, followed by gas quenching. The microstructural observation revealed that the fraction of the martensite structure in the high-carbon steel layer decreased and, alternatively, a pearlite structure evolved as the fraction of the low-carbon steel layers was increased; whereas the low-carbon steel layers showed ferrite and pearlite structures with any construction of the clad steel. Consequently, the hardness of the high-carbon steel layer decreased in the sheet with the higher fraction of low-carbon steel layers. The reason for this change is due to both the elastic strain and the plastic deformation of the high-carbon steel layer induced by phase transformation in the low-carbon layers.
•A dual moment frame lateral-force resisting system is proposed.•The system relies on CFT columns to provide additional strength and stiffness.•1- to 4-story buildings with the dual CFT system were ...less susceptible to collapse.•CFT columns were most effective in 1-story and 2-story office buildings.
A dual lateral-force resisting system consisting of a primary lateral-force resisting system and secondary concrete-filled steel tube (CFT) columns placed in the gravity framing is presented in this paper. The dual CFT system concept relies on the primary lateral-force resisting system to supply the main lateral strength, while additional lateral strength and robustness is provided by the CFT columns. To explore the viability of the concept, the predicted seismic performance of 1-story, 2-story, and 4-story office conventional buildings, with perimeter steel moment frames and wide-flange gravity columns, was compared to the performance of the same buildings but employing square HSS columns filled with unreinforced concrete. The analyses predicted that, compared to conventional buildings, buildings with the dual CFT system were 20–83% less susceptible to seismic collapse, depending on the strength and ductility of the primary moment frame, the orientation of the wide-flange columns in the conventional building, and the number of stories. Using high-strength, thick, or slightly larger CFT columns did not significantly improve collapse safety. Buildings with the dual CFT system generally had improved seismic performance, depending on the moment frame design, the number of stories, and the intensity of the ground shaking. Buildings with the dual CFT system had up 45% lower repair costs, up to 64% shorter repair time, and a lower probability that the building would be deemed unsafe.
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