Ton-Lo Wang

Impact analysis of cable-stayed bridges

Abstract An impact analysis of cable-stayed bridges due to a vehicle moving across rough bridge decks is presented. In the study, the vehicle was simulated by a nonlinear vehicle model with seven degrees of freedom according to the HS20-44 truck. The cable-stayed bridge was modeled as a planar bar system. The road surface roughness of the approach roadways and bridge decks was generated from power spectral density function for very good, good, and average roads according to International Organization for Standardization (ISO) specification. The geometric nonlinearities arising from cable sag and the effect of the axial forces on the stiffness of members were taken into account. The dynamic behavior and impact percentages of these different types of bridges were studied. Furthermore, the influence of damping ratio was discussed. The results obtained are applicable to the design of cable-stayed bridges.

Dynamic behavior of horizontally curved I-girder bridges

Abstract The purpose of this paper is to investigate the dynamic behavior of horizontally curved I-girder bridges due to one or two trucks (side by side) moving across rough bridge decks. The bridge is modeled as a planar grillage beam system composed of horizontally curved beam elements and straight beam elements. Warping torsion is taken into consideration in the analysis. The analytical vehicle is simulated as a nonlinear vehicle model with 11 independent degrees of freedom according to the HS20–44 truck design loading contained in the American Association of State Highway and Transportation Officials (AASHTO) specifications. Four different classes of road surface roughness generated from power spectral density function for very good, good, average, and poor roads are used in the study. The analytical results are very significant and show that the dynamic behavior of curved I-girder bridges is quite different from that of straight girder bridges. The impact factors of bending and shear for inside girders of curved I-girder bridges are significantly smaller than those for outside girders.

VIBRATION OF HORIZONTALLY CURVED BOX GIRDER BRIDGES DUE TO VEHICLES

Abstract The purpose of this paper is to develop a procedure for obtaining the dynamic response of thin-walled curved box girder bridges due to truck loading and to get their basic impact characteristics. The box girder bridge is divided into a number of thin-walled beam elements. Both warping torsion and distortion are considered in the study. The analytical vehicle is the AASHTO HS20-44 truck simulated as a nonlinear vehicle model with 11 independent degrees of freedom. Four different classes of road-surface roughness generated from power spectral density function for very good, good, average, and poor roads are used in the analysis. In comparison with the other approaches developed by former investigators, the proposed procedure not only facilitates a physical understanding of the general structural response, but also greatly reduces the computing time required and output obtained. The analytical results show that most impact factors of torsion and distortion are much larger than those of vertical bending response. The impact factors of normal stress at different points in the same cross section are quite different. The larger the normal stress, the smaller the impact factor will be. Though the static normal stresses at different positions in the same cross section may be extremely different for a curved box girder bridge, their dynamic normal stresses tend to be uniform.

Dynamic response of highway girder bridges

Abstract The objective of the paper is to investigate the variation of dynamic loading of girder bridges with different girder number and span length due to several vehicles moving across rough bridge decks. Nine girder bridges with girder number ranging from four to eight and span length changing from 40 to 120 ft are designed based on the AASHTO standard highway bridges and modeled as grillage beam systems. The vehicle is simulated as a nonlinear vehicle model with 11 d.f. according to the HS20-44 truck design loading contained in the AASHTO specifications. Four types of road surface roughness generated from power spectral density function for very good, good, average and poor roads in accordance with International Organization for Standardization (ISO) specifications are used in this study. The maximum impact factors of different girders of bridges are obtained for different number of loading trucks (side by side), road surface roughnesses, transverse loading positions and the vehicle speeds changing from 15 to 75 mph. The conclusions reached in this study are useful in the further study of the impact of highway bridges and for practical bridge design engineers.

Vibration of highway steel bridges with longitudinal grades

Abstract The purpose of this paper is to analyze the effect of longitudinal grade on the vibration of highway bridges. The bridges are modeled as grillage beam systems. The vehicle is simulated as a nonlinear vehicle model with 11 independent degrees of freedom according to the HS20-44 truck design loading specified in the American Associate of State Highway and Transportation Officials (AASHTO) specifications. A good road surface roughness generated from the power spectral density function for the approach roadways and bridge decks is used in the analysis. Two types of longitudinal grade shape with six different grades ranging from 1% to 6% are analyzed. The dynamic responses of three steel multigirder bridges with different span lengths due to multiple vehicles moving across rough bridge decks with different vehicle speeds are evaluated. The analytic results are useful for practical bridge design.

Free Vibration of Helical Springs

This paper presents a theoretical investigation of the coupled extensional-torsional vibration of helical springs. The shapes of the individual waves are simple, but the oscillation of the spring is complex due to the interaction and superposition of the component waves

DYNAMIC RESPONSE OF HIGHWAY TRUCKS DUE TO ROAD SURFACE ROUGHNESS

Abstract Vehicle characteristics, vehicle speed and road surface roughness are major factors influencing bridge dynamic response. In order to improve the previous vehicle model studies, vehicle models with seven or twelve degrees of freedom were developed for H20–44 and HS20–44 trucks, respectively. Vehicle models were validated by comparisons with the real truck dynamic systems. The road surface roughness was generated from power spectral density (PSD) functions for very good, good, average, and poor roads. The impact factors of suspension and tire forces were obtained for vehicle models running on different classes of roads at various speeds. A comparison of computed and experimental impact results was also made.

Impact in highway prestressed concrete bridges

Abstract The purpose of this paper is to study the factors which affect the dynamic behavior of highway prestressed concrete bridges. An HS20–44 truck model with 12 degrees of freedom was developed and used in this analysis. Highway prestressed concrete bridge models with spans of 30, 60, 90, and 120 ft (1 ft = 0.305 m) were designed according to American Association of State Highway and Transportation Officials (AASHTO) standard bridge girders. Two percent of the critical damping was assumed for the bridge. The road surface roughness of the approach roadways and bridge decks was generated from power spectral density (PSD) function for very good, good, average, and poor roads in accordance with International Organization for Standardization (ISO) specification. The impact percentages in moment, deflection, and end shear of the bridge for different bridge span lengths, vehicle speeds, and road surface roughness were calculated and compared with the AASHTO specified values.

Impact in a railway truss bridge

Abstract The aim was to investigate the dynamic interactions between an open deck steel truss bridge and a moving freight train. A non-linear, 100-ton (gross weight 131.5 tons), freight car vehicle model and the 200-ft, open deck, Warren-type steel bridge model were used in this study. Equations of motion for the vehicle, bridge, and bridge/vehicle interactions were also presented. The track irregularities on the approach and the bridge were generated from power spectral density functions for Federal Railroad Administration (FRA) class 4 track (maximum speed 60 mph). Both zero and two percent of the critical damping were assumed for the bridge. Impact percentages in the bridge due to a three, 100-ton freight car train operating at 20, 40, and 60 mph were calculated. These were compared with the data obtained from an earlier field investigation and those specified by the American Railway Engineering Association (AREA) specifications.

Work-of-indentation as a means to characterize indenter geometry and load-displacement response of a material

Normalized indentation works, referred to as the total and elastic energy constants, have been shown to be effective in the representation and analysis of experimental load‐displacement data. However, their physical meaning, influencing factors, variation range and relationships with other nanomechanical quantities are not precisely known. In this study, the load‐displacement data obtained as a result of simulations of elastic and elasto-plastic indentations are extensively analysed to enhance our understanding concerning these two energy-based parameters. It has been shown that while the total energy constant describes the state of an indenter tip and the type of contact regime, the elastic energy constant characterizes the response of a material to indentation. In addition, their applications in the evaluation of key nanomechanical quantities such as the indenter tip radius, the nominal hardness and the contact depth are also discussed. (Some figures may appear in colour only in the online journal)