Research On Dynamic Behavior Of Cold-formed Square Steel Tubular T-joints Under Impact Load

With the rapid development of social economy, the tubular structure has beenwidely used because of its good mechanical properties and beautiful architecturalstyle, such as offshore platforms, railway stations, stadiums, and airports. In recentyears, Terrorist attacks, fires, explosions and other extreme disasters have causeddisastrous casualties and property loss because of building collapse. The impact loadis often an important reason for structural damage, so more and more attention hasbeen focused on the evaluation and design of the impact resistance of engineeringstructures. As a key element of tubular structure, the impact resistance of the tubularjoints primarily determines whether the tubular structure has good impact resistanceor not. At present, the study of tubular joints and stiffened tubular joints has mainlyfocused on the static mechanical properties. While the research of failure mechanisms,ultimate bearing capacity, structural deformation, energy conversion of tubular jointsunder impact load is not enough, and previous studies is mainly about hot-rolled pipes.A lot of basic study works on the cold-formed tubular joints need to be carried out.For the above reasons, an experimental study research of cold-formed square tubularT-joints and stiffened joints were conducted to study the impact mechanical propertiesusing the high-performance drop hammer tester in Hunan University. Numericalanalysis was carried out by using general nonlinear FEA software ABAQUS. Theresearch work can be summarized as follows:(1) Experimental study of4unstiffened cold-formed square tubular T-joints and2stiffened joints were conducted to study the failure modes of unstiffened tubularjoints and stiffened tubular joints; The law of change and development of impactperformance indicators were revealed, such as deformation of joints, bearing capacityand energy dissipation. Such indicators of unstiffened tubular joints and stiffenedtubular joints have been compared to verify the effectiveness of stiffened measures.(2) The influences of impact energy, the width ratio of branch member to chordmember, and stiffened methods to resistant performance indicators including impactforce and displacement have been compared. And resistant performances ofunstiffened joints and stiffened joints have been studied through load-displacementcurve and energy dissipation.(3) The finite element model of cold-formed tubular T-joints under impact loading was developed using ABAQUS/Explicit. The numerical results have a goodagreement with the research of scholars in the past and experimental results in thispaper. Based on this numerical model, how the tubular joints works to resist impactload has been analyzed. The coupling relationship between local deformation andoverall deformation has also been preliminarily studied. Simplified formula of theimpact strength of unstiffened joints has been proposed through the relationshipbetween the energy dissipation and the impact energy.(4) The effects including impact energy, the width ratio of branch member tochord member and the ratio of width to thickness of chord member have been studiedin the numerical model. The differences of mechanical performance betweenhot-rolled tubular joints and cold-formed joints under impact load have beencompared.