The purpose of this research is to investigate the influence of the weld penetration depth on the fatigue behavior of beam-to-column connections in steel piers. Fatigue loading tests were carried out on three types of the welded connections. FEM analyses were also performed on the specimens to clarify the stress distributions at the vicinity of the connection. The observation of fracture surfaces indicates that fatigue cracks are initiated not from the inherent cavity at the end of the connections but the weld roots and/or weld toes. The fatigue cracks may be initiated at the weld roots and toes when the weld penetration depth is less than one-third of the flange plate thickness. The S-N diagrams based on hot-spot stress range, of which extrapolation points are O.5t and 1.0t (t: flange plate thickness), shows that the fatigue strength is almost the same despite the weld penetration depth.
In this study, the effect of welding fabrication conditions on mechanical properties of weld metal is investigated by experiment and numerical analysis by FEM. The cooling time of welding metal is taken up among the factors which affect the strength of weld metal. Experiment was performed as a parameter heat input, interpass temperature and plate thickness which affects the cooling time, and tensile coupon tests were carried out to clarify relation between each factor and strength. Numerical analysis was performed to investigate the cooling time of the weld metal, and relation between each factor and cooling time was clarified. It is shown that the strength of weld metal can calculate with sufficient accuracy using cooling time.
Bolting-Stop-Hole method is one of useful countermeasures against fatigue cracks originating in steel members. If bearing type of high strength bolts are applied instead of usual high strength bolt, stress transmission in the hole can be expected by stress transfer through bolt itself in addition to friction between the base plate and bolt head (nut). This study aims at making clear the fatigue strength of fatigue cracked out-of-plane gusset welded joints repaired by the bolting-stop-hole method using bearing type of high strength bolt. For this purpose, fatigue tests and stress-measuring tests on model specimens have been performed in consideration of plate thickness.
In this paper, the static characteristics of the bond joint type column base were investigated by cyclic loading test. The bottom of SHS column was welded to the connecting cast iron part with sleeves. The anchor bar was connected to the sleeve by filling with mortar. The main parameters were the forms of the concrete foundation. The test results show that the behavior of a this type column base was comparatively good. The elastic limit strength, the yield strength, the ultimate strength and the initial stiffness can be estimated by Euler-Bernoulli's assumption on the upper surface of concrete founda tion, taking neutral axis into consideration.
Steel column members with Embedded Plastic Segment (EPS) has been developed and proposed as a new seismic retrofitting technique for existing steel bridge piers to enhance the ductility with less increment in the ultimate strength of the columns. In this paper, the effect of the seismic retrofitting technique on the ductility and ultimate strength of a steel column member is investigated by comparing with a concrete filled column member and a constitutive model of EPS with the proper length is proposed for the elasto-plastic analysis in the design. lso presented is an application example of the seismic retrofitting technique into an actual existing steel bridge pierrequired to be retrofitted.
A series of compressive tests of virgin specimens and ones corrected by heating was carried out. Buckling strength of specimens by heating correction became lower than that of virgin specimens. The ultimate strength of them was almost equal to that of virgin specimens. Residual imperfection, which was not completely corrected by heating, largely affects a decreasing of buckling strength. Making residual imperfection extremely small, buckling strength was hardly lowered. If the absolute value of residual imperfection was same as plate thickness, 80-9O% buckling strength of a virgin specimen could be kept.
Shaking table tests of a 1/3rd-scale three-story steel moment resisting frames with viscoelastic damper have been conducted to verify the evaluation method for earthquake response of buildings. The effect of added viscoelastic dampers on the maximum displacement and the story shear of steel frame are investigated. The input ground motion is an artificial earthquake with a target response spectrum prescribed in the current seismic code. Test results show that the viscoelastically-damped structure can achieve a significant reduction of earthquake response as compared to the case with no dampers. Analytical simulations were also conducted. The dynamic response of the steel frame with added viscoelastic damper could be evaluated using the Voigt model and the Maxwell type 5-element model.
A suspension bridge shows economical priority in ultra-long span. However there are not a few cases that a suspension bridge is adopted in span of less than 1000m from the viewpoint of the local condition or landscape. It is an important subject to reconsider the cable safety factor for suspension bridges, because reduction of the construction cost is a strong requirement. In this paper we design some middle single-span suspension bridges, and calculated the random live loads under traffic congestion by Monte Carlo simulation. We arrived at the conclusion that the reduction of the cable safety factor for middle-span suspension bridges is possible using load factor design method.
Ultimate states of cylindrical reticular structures subjected to earthquakes are evaluated based on energy balances. The collapse mechanism of the structures can be grouped into two sorts: the roof brace failure type and gable vertical brace failure type. Then using the collapse mechanism and the maximum drift obtained by the static nonlinear analysis, the safety criterion is proposed based on the concept that all the input plastic energy is dissipated by inelastic deformation in brace members.