Papers by Keyword: Steel Columns

Abstract: Nonlinear time history analyses of SDOF bridge columns with elasto-plastic flexural behaviour which are subject to eccentric gravity loading are conducted to quantify the effect of ratchetting. Peak and residual displacements were used as indicators of the degree of ratchetting. The effects of member axial loads and design force reduction factors were also investigated. It was shown that displacement demands increased with increasing eccentric moment. For eccentric moment of 30% of the yield moment, the average maximum and residual displacements increase by 4.2 and 3.8 times the maximum displacement, respectively, which the engineers calculate using static methods without considering ratchetting effect. Design curves for estimating the displacement demands for different eccentric moments are also developed. The current NZ1170.5 (2016) provisions were found to be inadequate in estimating the maximum displacement for steel structures, and hence, new provisions for steel structures should be presented.

Abstract: This paper summarizes the findings of two test programs that investigated the hysteretic behavior of wide-flange columns in steel moment-resisting frames. Both deep and shallow steel columns were examined. The members were subjected to unidirectional and bidirectional lateral loading histories coupled with constant and varying axial load demands. The experimental findings highlight the dependence of the steel column response on the member end boundary conditions, the biaxial bending, the loading history, as well as the test-scaling. Steel columns subjected to high axial load demands do not behave as force-controlled elements as suggested by current nonlinear modeling recommendations in North America. Accordingly, an updated axial force limit is proposed in this case. Moreover, in light of the test findings, seismic design recommendations are proposed to limit column damage during strong earthquake shaking.

Abstract: With the lapse of time, the carrying capacity of early steel structure buildings which affected by various factors in the process of long service has dropped. Meanwhile, the use function of buildings has been asked for a higher level with the improvement of people's living standard. In this case, the assessment and reinforcement on buildings are particularly important. In this paper, the characteristics and mechanical properties of axially loaded steel columns strengthened by welding under load and axially loaded steel columns strengthened by enclosed reinforced concrete under load, the mechanism of steel and concrete work together and the reduction coefficients of steel and concrete of enclosed reinforced concrete have been systemically introduced. To pave the way for the following researches of steel numbers reinforced under load.

Abstract: This paper presents the results of a simulation study of fire tests of restrained (fixed-hinged) hot rolled steel column sections subjected to axial compression in addition to constant and variable thermal loads. Finite element computer software is utilized to study steel columns stability under thermal loads using three approaches; non-linear buckling analysis, thermal structural-Load Transfer Method (LTM) analysis, and Direct Coupled Field analysis. The finite element results are in good agreement with experimental results found in literature. The Direct Coupled Field analysis is also used to study a non-uniform temperature distribution on one side of the steel column. The LTM shows the best capabilities in studying such problems compared to the other two approaches

Abstract: The use of hollow structural steel (HSS) columns filled with concrete has become widespread in the past few decades. The residual strength of a composite column may used to assess the potential damage caused by fire and help to establish an approch to calculate the strctural fire protection. Sum up BS standard, AISC standard and some research about cementiteous sprayed monolithic fire protection coatings of Prof. Han’s and calculate the residual strength of a composite column for New Terminal Building of Republic of Mauritius Sir Seewoosaugur Ramgoolam International Airport Expansion Project. The concolusion and method may be used by other approximate project.

Abstract: One of the critical factors affecting the strength of steel columns at elevated temperatures is the influence of material creep. Under fire conditions, steel columns can exhibit creep buckling, a phenomenon in which the critical buckling load for a column depends not only on slenderness and temperature, but also on the duration of the applied load. This paper will propose a preliminary methodology to study the phenomenon of creep buckling in steel columns subjected to fire. Analytical solutions using the concept of time-dependent tangent modulus are developed to model time-dependent buckling behavior of steel columns at elevated temperatures. Results from computational creep buckling studies using ABAQUS^® are also presented, and compared with analytical predictions. Both analytical and computational methods utilize material creep models for structural steel developed by Harmathy, and by Fields and Fields. The analytical and computational results clearly indicate that accurate knowledge of material creep is essential in studying creep buckling phenomenon at elevated temperatures, and that neglecting creep effects can lead to potentially unsafe predictions of the strength of steel columns subjected to fire.