Dongzhou Huang

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.

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.

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.

ANALYTICAL AND FIELD INVESTIGATION OF LATERAL LOAD DISTRIBUTION IN CONCRETE SLAB-ON-GIRDER BRIDGES

The aim of this paper was to evaluate the accuracy of equations specified by the current AASHTO-LRFD codes for highway concrete slab-on-girder bridge bending moment distribution factors. A total of 645 bridges were modeled and analyzed using the 3-D finite element method. AASHTO HS20-44 design trucks were used in the analysis. The load distribution values obtained from analysis were compared to the code values. Results of the investigation indicate that the AASHTO-LRFD load distribution equations for the interior girders of bridges with single-lane loading, as well as for the exterior girders of bridges with 2 or more design lanes loaded, are accurate for most practical cases. Other findings are also provided.

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.

Probabilistic fatigue life analysis of highway steel bridges

Abstract The purpose of this paper was to calculate the fatigue lives of highway steel bridges using a reliability-based methodology. An HS20-44 truck model with 12 degrees of freedom was developed and used in the analysis. Both noncomposite and composite steel beam, 60 ft (18.3 m) long, highway bridges were adopted in this study. Two percent of critical damping was assumed for the bridges. The road surface roughness of the approach roadways and bridge decks was generated from a power spectral density (PSD) function for very good, good, average, and poor roads in accordance with International Organization for Standardization (ISO) specifications. The fatigue life of both noncomposite and composite steel beam bridges for different vehicle speeds and classes of road surface roughness is calculated from the generated stress time-histories.