This paper presents a numerical study on the cumulative plastic deformation capacity determined by local buckling of cold-formed circular tubular beam-columns subjected cyclic loading. The parameters are diameter-thickness ratio, axial force ratio, and slenderness ratio, the main amplitude of rotation angle which is expected to be occurred to the strong earthquake motion is 0.03rad. The equations that can evaluate the cumulative plastic deformation capacity are proposed, these equations are compared with the results of experiments.
Initial bolt forces have relationship with collapse modes through t-stub flange thickness showing that the lines of tcriijmn defined in reference except a mode, in which faying surfaces are separated, are having a common point. β(the ratio of an initial bolt force to yield bolt force) being the abscissa of the point and t(flange thickness) is determined by the stub dimensions except flange thickness. The collapse modes indicated by β and t are divided into four regions, in which each collapse characteristic is distinguishable.
In the preceding researches authors have proposed the seismic upgrading method of an anchor-bolt in an exposed-type column base in the existing old steel buildings and the tension test of the upgraded anchor-bolt showed enough upgrading effect. In this paper an experimental test of exposed-type column base using such upgraded anchor-bolts is performed and upgrading effect is recognized, and it is shown that the exposed-type column bases using such upgraded anchor-bolts could satisfy the rotation capacity demanded in the structural design.
This paper proposes two types of dampers using fasteners of PCa curtain walls in order to reduce seismic response and damage of steel structures. Two types of dampers proposed here are friction damper and flexural yielding damper, dynamic and static cyclic loading tests were performed to investigate the hysteretic performance of dampers. Both friction damper which constructed the steel plate fastener, curtain walls, and concrete plate, and flexural yielding damper using rolled H-shaped steel showed stable behavior until cumulative slip or plastic deformation exceeded 2000mm.
In the current design method, high strength bolts is widely used as how to join components. The provisions of bearing connection joints high strength bolts is specified in the present design standard, but those are similar to the rivet connection. They are not conditions that bolt touches bolt hole, therefore it is necessary to clear those dynamics movement and limit state. This paper shows load transmission mechanism and limit strength of the bearing connection for high strength bolts, with the elasto-plastic finite displacement analysis for high strength bolted joints, and what various parameters affect is investigated.
The welded joints of steel structure often accompany the high strain concentration and stress multiaxiality. Especially in the case of welded joints which subjected to bending during earthquakes, there is a possibility that a ductile crack occurs in the toe and the crack becomes the trigger of brittle fracture. In this study, the weld shape effect on ductile crack initiation and the control effect which produced by toe grinding were investigated through the cyclic loading tests of cross joint specimen and nonlinear FEM analyses on the specimen. As a result of loading test, the weld shape effect on ductile crack initiation at toe was confirmed. From the analytical investigation, the influence of the toe radius, the bead shape, and the base metal wastage accompanied with toe grinding were revealed. In particular, it was shown that the toe radius strongly affects on the risk of ductile cracking and toe grinding is effective to control the risk.
In order to estimate heat-affected zone (HAZ) toughness of electroslag welds of building box columns, formulas consisting of steel chemical compositions have been proposed. The connection between inner-diaphragm steel and skin-plate steel have been studied by electroslag welding tests and simulated HAZ tests. The Charpy absorbed energy (vE0: average value at 0 degree C) for the skin-plate HAZ, 1mm from the weld fusion line, can be simply estimated by the formulas using the chemical compositions (mass %) of the skin-plate steel.
This study describes fracture strength of electro-slag welded (ESW) connections in beam-to-welded box column connection. The discussions are based on subassemblage connection test results of ESW joints and finite element analysis (FEA) results of corresponding analytical models. Case studies are also carried out making the gap between an interior diaphragm and a beam flange main analytical parametes. Results are summarized as follows; 1) The subassemblage connection test results show roughly positive correlation between the fracture toughness and the fracture strengths of ESW joints. 2) The subassemblage connection test results and the corresponding FEA results correlate the fracture toughness with calculated equivalent maximum principal stress. 3) The fracture behavior of ESW joints shows good correlation between subassemblage connection test and cruciform model test.
This paper discusses the effect of connection details on plastic deformation capacity of steel beam-to-column connections. The subjects are beam end connection with either through-diaphragms, exterior-diaphragms or knee brace dampers. It is clarified from the experimental results that connections with exterior-diaphragms and knee brace dampers have two or three times plastic deformation capacity of connections with through-diaphragms, whose capacity have been improved more by many researches than before the Kobe earthquake.
We propose a method for obtaining quantitative information for preparing new steel section lists that reflect recent variations in construction demands. To quantify new demands for steel section sizes, we solve a series of design optimization problems, wherein new construction demands, e.g., demands for longer spans, are reflected as the distributions of design conditions. Applying a statistical approach to the distributions of the optimal solutions, we obtain the quantitative information on the section sizes to be selected in new steel section lists. Through an example problem of hospital buildings, we demonstrate the change of the distributions of the optimal solutions with respect to the variations in span lengths. We also demonstrate that sections with thinner flanges are often selected than those in the current section list.