Electric power transmission needs huge amount of investment. The electric industry requested further improvement in strength of steel angles for transmission towers as an effective means of the cost reduction. This is the report of the final results obtained by the committee which was formed it accordance with this requirement in April 1988. The successful outcome will be approved b3 Japan Society of Steel Construction and become one of its standards in September 1999. The newly developed angles will become in practical use in the near future after several structura. tests.
This paper describes a method that estimates some deterioration causes of steel bridge paint. A numerical formula that attaches environment and the deterioration causes that environment is composed the relation is supposed to calculate influence degree of the deterioration causes. As the method that calculates the influence degree, the authors use back propagation method (BP) that is a general learning method of neural network that is one of AT technology. By express the numerical formula with a network and using BP, it becomes possible to calculate the influence degree that matches to data most. Actual inspection data has scatter not a little. The scatter can be considered by using BP. Granted, scatter of the data is scatter in the subjectivity by inspector, the method is able to correspond flexibly.
On the demolition works of steel buildings which reach their durable period, the blasting demolition method might be very effective. In order to control the demolition of steel buildings safely and surely, it is necessary that the minimum amount of high explosives can be estimated. Therefore, as the basic study which probes the impact fracture mechanisms of steel plates with shaped charges, we prepared the shaped charges, whose design parameters are materials of liners and amount of high explosive, and obtained the control of notch depth of steel plates through many experiments. And we carried out the Metallurgical analysis for grasping dynamic effects on steel plates against impact force.
This paper presents the structural performance of H-beam-and-RHS column subassemblage without any diaphragms. The column thickness at beam-to-column connection area is increased by the induction heating procedure. To discuss the reinforcing effects by the horizontal haunch of beam and column with increased thickness, the cyclic reversal loading test for beam-and-column subassemblages was carried out. To represent the reinforcing effect of column with increasing thickness, constant axial load was applied on the top of the column. The elastic-plastic behaviors of subassemblages are evaluated by using finite element and numerical in-plane analyses. The full plastic and ultimate strengths of the beam-to-column connection are estimated by the yield line theory.
This paper proposes to apply steel bellows as energy absorbing restrainers for steel girders and piers system. The shoes of the bridge are intentionally collapsed as fuse members for heavy earthquakes in order to decrease seismic forces acting to piers, and after collapses of shoes, inertia forces and response displacements of girders are restrained by energy absorption due to bellows plant is deformation. Two span, three span and four span simple steel girders supported steel piers are modeled as mul t i- degree freedom systems by nonlinear springs andmass elements. In-plane elasto-plastic dynamic response analyses are carried out to examine and evaluate the effect and performance of the proposal design method. The results show that the proposal method may become effective seismic design method.
Creep and relaxation occur after High Tension Bolt (HTB) tightening causing shaft tension loss and further stress redistribution in the connected components. Past research has shown that ductility improvement and shaft tension loss control can be achieved by waisting the HTB shank. With the further modification of making the HTB head plate shaped counter sunk Head plate bolt with an aesthetically pleasing, flat surface less susceptible to rain corrosion results. In this research, tensile, relaxation and friction grip joint slip experiments are done on waisted shank, counter sunk head HTB to ascertain the ductility improvement, the resulting decrease in shaft tension loss and its magnitude, as well as their applicability in friction grip steel connections.
High Tension Bolts (HTB) are known to exert a significant influence on connection strength characteristics and have and influence ductility of the joint. Normally failure occurs in shape resultant high stress concentration neck and threads areas, resulting in low ductility characteristics. In this research by waisting the HTB shaft such that failure occurs in the waisted shaft we investigated the stress concentration decrease in neck and thread regions and the ductility increase by finite element analysis and static tensile experimental tests. The improvement of bolt shaft tension loss was also examined
In the 1995 Hyogoken-Nanbu earthquake, brittle fracture of beam flange in the vicinity of beam-to-column connections were widely observed.To investigate this phenomenon, a series of tests on beam-to-column connections were carried out with regard to mechanical properties of beam materials(low toughness hot-rolled H-section vs high toughness hot-rolled H-section) and geometrical condition of the welded joints.The obtained results are as followings:(1)There was no remarkable difference on the deformation capacity between specimens using low toughness hotrolled H-section and specimens using high toughness one.It was considered to be attributed to low yield-ratio of beam flange and stress intensity ratio of beam and diaphragm.(2)The shape of the weld access hole and fillet weld of backing strip have an important influence upon the fracture behavior especially in the case of low fracture toughness of the hot-rolled H-section.
Experimental study about the exposed type column base using special anchor bold with upset threaded parts, which guarantee the full plastificatk n of the shank. Test results shows that this type of column basepelf well until large plastic deformation (dry angle of the column ≅1/25). After this loading the nuts wererelightened and additional loading cntinued At this stage the ookamn base behaved well again. From the test results of cyclic loading tests using four full size specimens, it becomes clear that the statical characteristics of this exposed-type of column base with special anchor bolts are slip models but those stiffness, yield strength and plastic defomlation rapacity are priate. The statical characteristics of this type column base after repair by retightening of nuts are also good. It means that this type of exposed-column bases have good repairable ability after earthquake damage.
A sereis of formulae is proposed for predicting the buckling coefficient of a web plate on the launching shoe which is practicized during the girder erection process with the launching (or push out) method. The formulae are established from the authors' FEManalyses on the patch loaded web plate, and the magnitude of the in-plane bending moment, shear force and so on can be took into the account. Through the formulae, the estimation of the buckling strength of a web plate on a launching shoe can be made easily.
This paper presents experimental and numerical studies on the effects of undermatched welds with pure iron welding wires using GTAW process on 490N/mm2 class steels. Undermatched welds prevent cold cracking without preheating, and allow the use of short bead welding without reducing fracture toughness of base metals and welds, then they prevent brittle fracture under high strain rate like seismic load. The results of fatigue tests of welded joints showed that undermatched welds reduce stress concentrations and improve fatigue strength.
In a civil engineering field, steel pipes are used to various structures, penstocks, piers, piles, etc. Some geometrical imperfections would bring deterioration of their strength and shortening of their lifetime. However, effect of geometrical imperfections of steel bending roll pipes on local buckling strength and local stress is still indistinct. Therefore, it becomes important how to evaluate the strength of members with geometrical imperfections. This paper presents the finite element analysis of steel bending roll pipes and characteristics of their strength. Results of the numerical analysis make effect of geometrical imperfections on local bucklinE strength and local stress clear quantitatively.