The tensile test results for welded joiut of Austenitic staiuless steel for buildiug structure SUS304A usiug weldiug wire TS308MoJ show failure in the weld metal and lower teusile strength than base metal, whereas the joints exhibit strength overmatch in weld metal. FE-analytical studies demonstrate that those failure behaviors come from the large difference in uniform elongation between the base metal and the weld metal. The mechanical parameters which should be controlled to ensure a failure in a base metal and tensile strength of a base metal for a tensile specimen of the overmatched joint are proposed.
The load-sharing and axial reinforcement ratios are the two important indices which will directly affect the performance of RCFT columns. To obtain optimal ranges for these two indices which will put the RCFT into better mechanical and economic condition, using the validated numerical simulation model for RCFT, numerical parametric studies on load-sharing and reinforcement ratios of RCFT columns subjected to both axial compression and bending are performed. Through a plenty of simulation and analyses, optimal ranges for both load-sharing and axial reinforcement ratios are proposed. Meanwhile, the proposed optimal ranges are validated with both big-sized RCFT columns same to actual construction and bending. According to the validation results, the proposed ranges are applicable to RCFT columns under axial compression and bending and in any size.
Built-up columns comprising H-SA700 steel is proposed for use in all-bolted, seismically resilient building structures. The columns are formed by combining two plates acting as flanges and two cold-formed channels acting as dual web by F14T bolts. Laboratory experiments were conducted to examine the flexural properties of these columns. The results suggest that the flexural strength is dictated either by fracture of the perforated section, buckling of the flange plate, or inelastic out-of-plane distortion. The perforation due to bolt holes does not affect the elastic stiffness. Advantages offered by the built-up columns include a large elastic drift limit of 0.02 rad, the flexural strength twice as large, and reduction in the cross-sectional area.
In order to reduce erection pieces at combined joints of steel bridges, we proposed a new connection method in which we use bolted joints of longitudinal ribs as restrainers by tightening the bolts before welding of webs and flanges. The bolted joints of the longitudinal ribs have mixed state of damaged and undamaged friction surfaces. To establish the execution procedure, we investigated slip coefficient of the mixed state friction surfaces by slip tests. As a result, we obtained the relationship between the ratio of damaged surface and the reduction ratio of slip strength. On the basis of the test results, we showed the detailed procedure and applicable conditions of the proposed connection method.
Undercuts are typical weld defects in steel welded structures, and they are considered to decrease fatigue strength. In this study, shape and size of undercuts including in cruciform welded joints are measured with the laser displacement sensor, and an influence of the undercut on fatigue strength is investigated through fatigue tests on cruciform welded joints with various shape and size of undercuts and without undercuts. The influence of undercut shape and size on stress concentration is also discussed through three dimensional finite element stress analyses on joint models with actual shape and size of undercuts.
This paper presents design formulas for rotational deformation of several natural and high damping rubber bearings based on finite element analyses. At first, critical rotational angles on a natural rubber bearing in arbitrary rectangular shapes are computed and, design formula of the bearing is constructed. Then, material properties of the other three types of natural and high damping rubber materials are identified on the basis of several material tests and, the critical angles of the bearings with those materials are computed. From the results, the design formulas on those bearings are developed. Finally, the critical angles in oblique angle direction are computed for a natural rubber bearing and, its design formula is updated．
In 2007, the building standard law of Japan was revised and a specification of column overdesign factor (COF) was added in case of square tube columns. This research deals with existing non-conformed steel buildings using STKR columns according to being not satisfied with the specification of COF. In this paper, firstly, a practical investigation of existing steel buildings is conducted to the conformance to the specifications of current allowable stress design. As a result, it is clarified that a lot of buildings are not satisfied with the specification of COF. Next, previous researches of reinforcements to increase column overdesign factor are reviewed, and finally, some kinds of reinforcements for column are proposed based on the practical investigation.
In this paper, we studied experimentally the strength of long steel channel columns with the plates that tied fl ange by testing axial compression. The results show that the tie plates are eff ective in preventing torsional-fl exural buckling. In addition, we propose that it is possible to gain effective slenderness ratio from elastic analysis and show that the relationship between this ratio and the experimental strength corresponded to the previous evaluation formula. Therefore, it is clear that the buckling strength of a lightweight steel channel column can be estimated from a simple elastic analysis.
Strain measurements of orthotropic steel deck in steel box girder, Yahagigawa Bridge, were carried out in May and August 2011. The thickness of deck plate is mainly 12mm. However, partially deck plate of 16mm thickness is used near the end of bridge because of the reinforcement against the impact loads. Furthermore, ICR treatment for improving the fatigue strength of welded joint between vertical stiffener end in diaphragm and deck plate was carried out in this bridge. Therefore, strain measurements focused on the welded joints between vertical stiffener and deck plate and between deck plates of 12mm and 16mm in thickness and trapezoidal ribs. Equivalent stresses of deck plate near the vertical stiffener end and deck plate of 12mm thickness measured in August were higher than that measured in May. Equivalent stress of 12mm deck plate was higher than that of 16mm deck plate in both seasons.