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The shear lag effect on stress concentration in a simply-supported stiffened box girder is investigated by three-dimensional finite element analysis. In the analysis, the dependence of the stress concentration on the finite element mesh is circumvented by the multimesh extrapolation method. An extensive parametric study is conducted with respect to the geometry of the stiffened box girder including the cross-sectional area of stiffeners. The influence of the method of load application is also studied. The stress concentration due to the shear lag is sensitive to the way a concentrated load is modeled, while relatively insensitive to the way a uniformly distributed load is modeled. The estimation of the stress concentration by the formula of Eurocode 3 agrees well with the present finite element analysis results for an unstiffened box girder. However, the formula tends to overestimate the influence of the stiffener. Regression analysis is then conducted, taking three approaches. The multiple linear regression equation is the simplest approach and helps identify the degree of the influence of each parameter, yet the accuracy is low, as the mean square error is as large as 16–20%. Though a little more involved, the accuracy of the empirical formula is much higher, with the mean square error about 3%. An artificial intelligence technique, based on the regression model of the multi-layer perceptron, is also examined. The accuracy is the highest of the approaches tested: the mean square error is well below 1%. • 3-D FEA is conducted to investigate the stress concentration due to shear lag in a simply-supported stiffened box girder. • The discretization error is reduced by applying the multimesh extrapolation method. • An extensive parametric study is conducted to reveal the influence of the geometric parameters. • The influence of the method of load application is studied. • To provide simple means of evaluating the stress concentration factor, regression analysis is carried out. [ABSTRACT FROM AUTHOR]

This paper presents the results of seismic connection testing and finite element analyses (FEA) on the slenderness limitations of steel H-beams in special moment-frame (SMF) connections. The effectiveness of FEA models was first validated by the full-scale testing of a reduced-web-section (RWS) connection, and a post-earthquake bolted-web-welded-flange (BWWF) connection. FEA simulations were then performed to study the beam section properties and seismic connection performance. The result shows that if a H-beam has a compact section, the adopted connection will develop strength and ductility meeting the AISC seismic requirements, even though the plastic section modulus ratio between the beam flanges and whole section is less than 70%. The result also suggests the effectiveness of adding a web opening to a BWWF connection. These findings call for a re-examination of the requirements of highly ductile members in SMF connections. • The slenderness limitations and Z f / Z ratios are examined for steel H-beams for SMF connections. • The result suggests the effectiveness of adding a web opening to a BWWF connection. • The findings call for a re-examination of the requirements of highly ductile members in SMF connections. [ABSTRACT FROM AUTHOR]

In a steel I-bridge, corrosion often occurs severely at the I-girder end rather than at other parts. Therefore, this work mainly discusses the corrosion at the I-girder end as a bearing problem and shear capacity of the end plate. A finite element model (FEM) of a corroded steel I-girder end is developed considering commonly occurring corrosion at first. For the initial imperfection of a steel I-girder end, the initial deformation and residual stress are considered in the model which are simulated by elastic buckling analysis (eigenvalue analysis) and thermal stress, respectively. To investigate the effect of the corrosion pattern on the strength development, the single-area corrosion (flange, stiffener, web) and multi-area corrosion are included in the case study. Finally, the simulation results from the case study using finite element analysis (FEA) are used to formulate the simplified equations for evaluating the remaining load-carrying capacity of a corroded steel I-girder end with the specified corrosion patterns. Furthermore, for the engineering design and preliminary assessment of a corroded steel I-girder end, the simplified equations for evaluating the remaining yield strength ratio are also provided based on the remaining load-carrying capacity. • FE analyses for investigating the load-carrying capacity of the corroded I-girder end are conducted. • Equations for determining the load-carrying capacity of the corroded I-girder end are proposed. • Equations for determining the remaining yield strength of the corroded I-girder end are proposed. [ABSTRACT FROM AUTHOR]

Abstract: Quite a few researches on shear lag effect in box girder have been reported in the past, and many of them employed the finite element method. The past researchers, however, do not seem to have paid much attention to the influence of the finite element mesh on the shear lag, although the shear lag effect in terms of stress concentration can be quite sensitive to the mesh employed in the finite element analysis. In addition, most of the researchers on the shear lag have focused on simply supported girders and cantilever girders, while continuous girders have been dealt with in very few researches. The present study investigates the shear lag effect in a continuous box girder by using the three-dimensional finite element method. The whole girder is modeled by shell elements, and an extensive parametric study with respect to the geometry of a box girder is carried out. The influence of finite element mesh on the shear lag is carefully treated by the multimesh extrapolation method. Based on the numerical results thus obtained, empirical formulas are proposed to compute stress concentration factors that include the shear lag effect. [Copyright &y& Elsevier]

Abstract: The shear lag has been studied for many years. Nevertheless, most of the studies are related to the effect of the shear lag on stress distribution and very few have investigated the effect on deflection, although some design codes have formulas for the effect of the shear lag on deflection. In this conjunction, the present study carries out three-dimensional finite element analyses for various box girders to investigate the deflection at the mid-span. The multimesh extrapolation is employed to ensure the accuracy. The present study thus reveals the influence of the parameters that characterize the geometry of a box girder on the deflection. It is also shown that the formulas adopted in the design codes underestimate the deflection considerably. Based on the present numerical results, empirical formulas are proposed to compute the deflection magnification factors that account for the difference between the deflections due to the finite element analysis and the beam theory. [Copyright &y& Elsevier]

• Rubber insertion can act as a trapping layer to prevent bullet ricocheting. • Panels with energy absorption larger than bullet's energy can prevent perforation. • Energy absorption depends on thickness, and fiber geometry and volume fraction. In this study, the effect of para rubber insertion sheet on impact behavior of multilayer bulletproof panel made of steel fiber reinforced concrete was investigated. The objective of inserting rubber sheet into the middle layer was to act as a trapping layer to prevent bullets from ricocheting off the panel. Two test series were carried out: (1) investigation on energy absorption of each materials and (2) investigation on impact behavior of multilayer panel. The results from the 1st test series were used in the design of multilayer panels used in the 2nd series. The target impact energy of the bullet was 607 J. The multilayer panels were designed to have energy level ranging from 450 to 750 J. The panels were subjected impact by 9 mm caliber bullet with velocity of about 398 m/s. Results showed that the panels with impact energy absorption (IEA) level lower than the kinetic energy of the bullet (607 J.) failed by perforation. The panels with IEA level equal to or higher than 607 J. exhibited penetration failure mode with circular spalling at the back surface. There was no bullet ricocheting that occurred beyond this IEA level. At the level of IEA higher than 672 J, the failure mode shifted to penetration without visible damage at the back surface. [ABSTRACT FROM AUTHOR]

Aerodynamic stability of π section, which is structurally economical, was studied. By locating the main girders at inward location, so that the ratio of the floor deck overhang C to the girder height D′, C/D′, to be 2.0, and also setting solid barriers at inward location, the wind-induced responses were much suppressed even under various angles of attack. Although, some wind-induced responses were still observed with the improved section, the magnitude of the negative aerodynamic damping that caused the vibration was found to be small, thus the section could be thought as a probable choice for long-span bridges. The stability due to the solid barrier location was accomplished by the separated flows mutual interference effect; the unsteady pressure on the upper surface of the deck decreased significantly for the torsional motion. [Copyright &y& Elsevier]