This study is aimed to investigate cracking mechanism of steel members under cyclic bending. The process of crack initiation and propagation in the seven specimens are studied. The effects of notch shape and cyclic loading pattern on ductile fracture of the specimens are discussed. A large radius notch can delay crack initiation and propagation. Also, differences in loading pattern affect crack initiation and propagation. Therefore, the strength, cumulative ductility ratio and energy absorption of the specimens show different results depending on the notch shape and loading pattern.
The authors have investigated practical application of beam-to-column connection with exterior diaphragm assembled by high-strength bolts. When horizontal loads due to bending moments of beams act at this connection under seismic force, local out-of-plane deformation of square hollow section (SHS) columns may occur. In this paper, experiment and FEM analysis with a part of SHS column were conducted to verify the effects of several parameters on local deformation behavior. Furthermore, based on the stress distribution obtained by the FEM analysis, a method of evaluating the strength of SHS by local deformation was proposed.
This paper deals with the fatigue durability of typical welded gusset joints in steel bridges strengthened by externally bonded carbon fiber (CF) sheets using Vacuum assisted Resin Transfer Molding (VaRTM) technique. The target specimens of welded gusset plates were fabricated and subjected to cyclic load. The fatigue tests of two types of specimens, non-strengthened and strengthened specimen with CF sheets using VaRTM technique, have been conducted in the parameter of nominal stress ranges and strengthened effects have been evaluated under applied stress ranges. The result shows that the fatigue durability of welded gusset joints strengthened by CF sheets using VaRTM technique can be remarkably improved.
Fatigue cracks in the web gusset round weld are regarded as important targets in bridge inspection. In order to avoid the risk of fracture certainly, it is necessary to understand the propagation behavior of the crack, critical crack size and detection methods. For these purposes, fatigue loading test using a large-size girder specimen with same gusset details as actual bridge was carried out to clarify the crack propagation by introducing beach marks. At the same time, several crack detection methods were applied during the fatigue test to find their detection ability with respect to the crack size. Based on those results, the control limit size for the crack inspection is proposed.
This paper presents seismic responses of steel frames with large deformable elastic braces by means of time domain analyses. Large deformable elastic braces are braces which never yield under even major earthquakes. The braces can realize large deformable elastic capability by unique topologies cut from steel plates. Seismic responses are compared and discussed for various steel frames with and without large deformable elastic braces.
The purpose of this study is to propose a method to evaluate yield strength of square CFT columns. Yield strength of a CFT column is calculated by assuming the stress-strain relationships of concrete and steel tube and using the Navier's hypothesis. Yield strength is compared with the superposed strength of square CFT short columns. Yield strength can be classified by four types of m-n interaction curves depending on the strain condition of the section. The formula for calculating yield strength is proposed by straight lines for each type. We show the difference between the simplified strength and yield strength and the method for determining the type and a calculation example.
As an effective countermeasure to prevent fatigue cracks at existing orthotropic steel deck (OSD) bridges, steel fiber reinforced concrete (SFRC) overlays have been increasingly used for damaged OSDs. SFRC has been adhesively bonded to deck plate by epoxy adhesives. A series of tensile shear and compressive tests of specimens using several epoxy adhesives immersed in water with high temperatures were conducted in order to examine the environmental degradation of the adhesive joints. Based on the experiments, this paper describes degradation tendency of the strength of the adhesively bonded joints and the material properties.
The purpose of this study is to suggest estimated formula of stress concentration factor on weld toe of non-load-carrying cruciform welded joints by externally bonded CF sheets. The regression lines of the relationship between numbers of CF sheet layers and stress reduction factor was analytically investigated using finite element (FE) model varying the toe radius. Further, estimated formula of stress concentration factor has been proposed by combined with the estimated formula of the stress concentration coefficient at the weld toe. The verification of the proposed estimated formula was carried out by comparing the stress concentration factor by tensile test and FE model simulating the weld toe of specimen.
Horizontal shear force acting on shear connectors in steel-concrete composite bridge decks has been basically designed by using Design Code for Steel Structures PART B so far. However, Specifications for Highway Bridges were revised in 2017 and the design load condition became different between them. In this study, shear force was analyzed by using elastic FE programs when T-type loads specified in the Specifications for Highway Bridges were applied on steel-concrete composite bridge decks. From the analytical results, the maximum shear force was presented at each loading position. Furthermore, from case studies, sharing ratio of the horizontal shear force acting on headed stud connectors was determined.