A simplified method for evaluation of shear lag stress in box T-joints considering effect of column flange flexibility

Piseth Doung,Eiichi Sasaki 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.73 No.2

This study provides a simplified method for the evaluation of shear lag stress in rectangular box T-joints. The occurrence of shear lag phenomenon in the box T-joint generates stress concentration localized at both web-flange junctions of the beam, which leads to cracking or failure in the weld region of the joint. To prevent such critical circumstance, peak stress at the weld region is required to be checked during a preliminary design stage. In this paper, the shear lag stresses in the T-joints were evaluated using least-work solution in which the longitudinal displacements of the beam flange and web were presumed. The evaluation process considered particularly the effect of column flange flexibility, which was represented by an axial spring model, on the shear lag stress distribution. A simplified method for stress evaluation was provided to avoid solving complex mathematical problems using a stress modification factor βs from a parametric study. The results showed that the proposed method was valid for predicting the shear lag stress in the box T-joints manually, as well compared with finite element results. The results are further summarized, discussed, and clarified that more flexible column flange caused higher stress concentration.

Experimental Study on Low Cycle Fatigue Strength of Beam-to-column Connections in Steel Bridge Bents with Different Plate Assembling and Material Mismatching

Kawin Saiprasertkit,Eiichi Sasaki,Chitoshi Miki 한국강구조학회 2012 International Journal of Steel Structures Vol.12 No.3

This study examined the effects of inherent defects due to plate assembling and material mismatched condition between base and weld metal on the fatigue strength of beam-to-column connections. Low cycle fatigue tests were carried out on specimens with different plate assembling systems and material mismatched conditions. The test results revealed that the global loaddisplacement relationships from specimens with different plate assembling systems and material mismatched conditions are similar, meaning these effects involve only local behavior of specimens. However, the fatigue strength of the specimens strongly depends on the location of defects resulting from plate assembling and mismatched conditions. The specimen with the undermatched conditions and the existing defect located closer to the corner of beam-to-column connection tends to have lower fatigue strength. The fracture surfaces indicated that failure patterns of specimen are different regarding mismatched conditions. While the crack propagated through the weld metal for the undermatched condition, it propagated towards the boundary between base and weld metal for overmatched condition. Elasto-plastic shell analysis was performed under the same condition as the experiments. And it is found that when evaluating fatigue strength of beam-to-column connections, the effects of plate assembling system and material mismatched condition should be considered.

Experimental and Numerical Evaluation of Bearing Capacity of Steel Plate Girder Affected by End Panel Corrosion

Nauman Khurram,Eiichi Sasaki,Hiroshi Katsuchi,Hitoshi Yamada 한국강구조학회 2014 International Journal of Steel Structures Vol.14 No.3

The present study deals with the effect of uniform and non-uniform local corrosion damages at the bearing stiffener andnearby web on the bearing capacity of plate girder. Five plate girder ends simulated with different uniform and non-uniformtypes of corrosion damage, at the base of the bearing stiffener are used in the experimental program. The experimental resultsare modeled and verified on a Finite Element (FE) software ABAQUS, considering shell-solid coupling elements formulation. The study is further extended to various damage cases i.e., stiffener damage, stiffer plus web damages etc. considering differentdamage heights and residual thicknesses. The study concludes that minimum thickness within any damage height may be usedto simulate the corrosion damage in a FE analysis. At the end, some empirical relationships are also proposed to estimate thebearing strength of the plate girder affected by the local corrosion damage at plate girder end.

Involvements of Stress Triaxiality in the Brittle Fracture during Earthquakes in Steel Bridge Bents

Hiroshi Tamura,Eiichi Sasaki,Hitoshi Yamada,Hiroshi Katsuchi,Theeraphong Chanpheng 한국강구조학회 2009 International Journal of Steel Structures Vol.9 No.3

Stress triaxiality is proposed as one of the key parameters to discuss the cause of brittle fracture during earthquakes in steel structures. This study analytically investigated the features of stress triaxiality in steel bridge bent subjected to earthquakes. The target structure is a steel bridge bent actually fractured during the South Hyogo prefecture Earthquake. From the investigations, it was confirmed that high stress triaxiality was generated at a point supposed as fracture origin. There is a possibility that the triaxiality was involved in the fracture strongly through the increase of maximum principal stress. Moreover, from the analyses accounting for several kinds of large earthquake waveforms, it was indicated that threre is possibility that the distribution of triaxiality around the fracture origin was not affected by significantly by each cycle and each waveform. Stress triaxiality is proposed as one of the key parameters to discuss the cause of brittle fracture during earthquakes in steel structures. This study analytically investigated the features of stress triaxiality in steel bridge bent subjected to earthquakes. The target structure is a steel bridge bent actually fractured during the South Hyogo prefecture Earthquake. From the investigations, it was confirmed that high stress triaxiality was generated at a point supposed as fracture origin. There is a possibility that the triaxiality was involved in the fracture strongly through the increase of maximum principal stress. Moreover, from the analyses accounting for several kinds of large earthquake waveforms, it was indicated that threre is possibility that the distribution of triaxiality around the fracture origin was not affected by significantly by each cycle and each waveform.

Finite Element Investigation of Shear Capacity of Locally Corroded End Panel of Steel Plate Girder

Nauman Khurram,Eiichi Sasaki,Hiroshi Katsuchi,Hitoshi Yamada 한국강구조학회 2013 International Journal of Steel Structures Vol.13 No.4

This study discusses the effect of local corrosion damages nearby the bearing region including the bearing stiffener andadjacent web damage on the ultimate shear and post-buckling strength of steel plate girder bridges. A computer packageABAQUS is utilized for the verification and extension of the numerical study. Various corrosion damage cases, specifically thebearing stiffener are studied considering different damage thickness and damage heights. The study concludes that local damageon bearing stiffener damage is more fatal than the local web damage for the shear resistance of the plate girder. Further, someempirical relationships are also derived to assess the residual shear capacity of the locally corroded plate girder at the bearingregion.

Fracture in Steel Bridge Piers due to Earthquak

Chitoshi Miki,Eiichi Sasaki 한국강구조학회 2005 International Journal of Steel Structures Vol.5 No.2

In recent years, the use of cold-formed steel rof truss has been increased in steel houses and high-rise apartments. The designexperimental research on the structural behavior of anchor connections is described. Roof truss and connection members couldbe jointed directly with self-driling screw fasteners or simple shaped connection members, which are excellent in workabilityand structural capacity. They could also be used to connect roof truss and sub-structure. The conecting method has beenselected according to the construction material of sub-structures: chemical anchor for reinforced concrete structures and weldingstrength and the stiffness, and the test results have been compared with AISI (1996) and AISC (1989) specifications. Simpleformulas for the ultimate shear strength of the screw fastener connections are proposed and compared with conection tests.

Experimental and Numerical Evaluation of Bearing Capacity of Steel Plate Girder Affected by End Panel Corrosion

Nauman Khurram,Eiichi Sasaki,Hiroshi Katsuchi,Hitoshi Yamada 한국강구조학회 2015 International Journal of Steel Structures Vol.15 No.1

The present study deals with the effect of uniform and non-uniform local corrosion damages at the bearing stiffener and nearby web on the bearing capacity of plate girder. Five plate girder ends simulated with different uniform and non-uniform types of corrosion damage, at the base of the bearing stiffener are used in the experimental program. The experimental results are modeled and verified on a Finite Element (FE) software ABAQUS, considering shell-solid coupling elements formulation. The study is further extended to various damage cases i.e., stiffener damage, stiffer plus web damages etc. considering different damage heights and residual thicknesses. The study concludes that minimum thickness within any damage height may be used to simulate the corrosion damage in a FE analysis. At the end, some empirical relationships are also proposed to estimate the bearing strength of the plate girder affected by the local corrosion damage at plate girder end.

Investigations on the Effect of Weld Penetration on Fatigue Strength of Rib-to-Deck Welded Joints in Orthotropic Steel Decks

Cao Vu Dung,Eiichi Sasaki,Keiji Tajima,Toshimitsu Suzuki 한국강구조학회 2015 International Journal of Steel Structures Vol.15 No.2

A common practice for the manufacture of orthotropic steel decks in Japan is to use 75% partial joint penetration welds between closed ribs and deck plates. To evaluate the effectiveness of the proposed 100% penetration on improving the fatigue strength of rib-to-deck welded joints in orthotropic steel bridge decks, four full-scale orthotropic deck specimens were subjected to laboratory testing. Specimens, consisting of a 12-mm-thick deck plate and 6-mm-thick rib, with one closed rib, were fabricated with 75% and 100% penetration. Fatigue test results showed that fatigue cracks initiated from the weld toe inside the rib in the 100% penetration specimens, but from weld root inside the rib in the 75% penetration specimens. To investigate this fatigue behavior, strain measurements were taken at 5 mm from the rib-to-deck weld line. Results of finite element analysis using the effective notch stress method indicate that a deeper partial penetration results in a slightly higher effective notch stress at the weld root of the partial penetration weld. The effective notch stress at the crack initiation location with 100% penetration is lower than that obtained with partial penetration. The open angle appears to have a significant effect on the effective notch stress at the upper weld toe when using 100% penetration. Therefore, the proposed 100% penetration appeared to have a positive effect on enhancing the fatigue resistance of rib-to-deck welded joints.

Applicability of Performance Improvement Method of Existing Steel Railway Bridges by Installing Concrete Decks

Masamichi Saito,Ichiro Sugimoto,Eiichi Sasaki 한국강구조학회 2013 International Journal of Steel Structures Vol.13 No.3

Steel railway bridges which exceed their design lifetime are increasing in Japan, and some of them have problems such as corrosion and fatigue. In this study, we proposed a method to improve the performance, such as the load-carrying capacity, of the existing steel railway bridges by installation of concrete decks. To figure out the applicability of the proposed method, we discussed the applicable range of span and the effect of stress reduction. Considering application into actual bridges, we proposed an installation method using pre-cast concrete decks and girder-deck connection with filler mortar and steel fasteners. Finally, we carried out loading tests of the connection with fasteners and bending tests of the applied girders. As a result, we found that the girder-deck connections have enough static capacity for lateral force and train loads, under the condition that the studs are installed and the gaps between the pre-cast decks are filled with mortar.

Experimental Study on Noise Reduction Effect of Installing Concrete Deck on Existing Steel Girders

Masamichi Saito,Ichiro Sugimoto,Eiichi Sasaki 한국강구조학회 2015 International Journal of Steel Structures Vol.15 No.1

There are a number of existing steel railway bridges which has problems regarding structure-borne noise under train passage. Authors have proposed a performance improvement method of existing steel railway bridges by installing concrete deck. Bythis method, the vibration of the girder and the structure-borne noise are expected to be reduced. Generally, it is known thatconcrete deck can reduce the vibration and the noise. However, the noise reduction effect has not been clarified. In this study,impact hammer tests were carried out to figure out the reduction effect of the concrete deck on the vibration and the noise. Through the test, it was found that the response acceleration of the steel girder web was reduced by installing the concrete deck,as a result of reducing the propagation of on-girder vibration into the steel girder.