Wind tunnel measurement of aerodynamic characteristics of trains passing each other on a simply supported box girder bridge

The aerodynamic performance of high-speed trains passing each other was investigated on a simply supported box girder bridge,with a span of 32 m,under crosswinds.The bridge and train models,modeled at a geometric scale ratio of 1:30,were used to test the aerodynamic forces of the train,with the help of a designed moving test rig in the XNJD-3 wind tunnel.The effects of wind speed,train speed,and yaw angle on the aerodynamic coefficients of the train were analyzed.The static and moving model tests were compared to demonstrate how the movement of the train influences its aerodynamic characteristics.The results show that the sheltering effect introduced by trains passing each other can cause a sudden change in force on the leeward train,which is further influenced by the wind and running speeds.Detailed analyses related to the effect of wind and train speeds on the aerodynamic coefficients were conducted.The relationship between the change in aerodynamic coefficients and yaw angle was finally described by a series of proposed fitting formulas.

Weakening effect of vertical prestress ducts on web sections in prestressed concrete box girder bridges

Based on experimental study result of two simply supported beams,which were prestressed by vertical tendons,the research on the weakening effect of vertical prestress ducts on web sections of prestressed concrete box girder was carried out. The test result shows that in the condition without grouting into the ducts,the cracking load is evidently lower than that with full grouting,and stirrup stress and principal tension stress at the surface of concrete will increase obviously. Meanwhile,the finite element analysis has been done to the test beams. The research is consistent with the analysis of finite element. The research tells that strengthening the detection and management for the vertical prestress grouting quality have an important meaning to prevent cracking of the prestressed concrete box girder bridge and provide one theoretical and testing basis for analyzing the cracking reason of such bridges.

Temperature distributions in concrete box girders due to heat of concrete hydration

Based on heat transfer theory,a two-dimensional complex exponential function was used to compute heat of concrete hydration.A concrete box girder consisting of a single box with two cells used on Harbin Songpu Bridge was measured on site.The two coefficients in the complex exponential function were determined to best fit the field measured data.ABAQUS program was used to simulate the heat transfer and determine the temperature distribution in the concrete box girders during concrete setting.The calculated temperature distribution in the box girders were compared with the field measured data and good agreement was observed.The temperature distribution and gradient in the entire box section,webs and bottom slab were analyzed using the measured and calculated results during the course of concrete hydration.

Preliminary Estimation of Torsion of Curved Bridges Subjected to Earthquake Loading

This paper focuses on the seismic response of the curved and post-tensioned concrete box girder bridges. More specifically, it investigates how the curvature influences the response of a bridge subjected to earthquake. Parametric analysis of different radius of curvature is performed and the internal forces, torsion moment, axial and shear along the bridge are calculated. Two types of connections are investigated, the monolithic connection and deck connection with bents and abutments with rubber bearing. The response spectrum seismic analysis was performed. The models were designed, according to the provisions of EC8-part 2, EC2 and the Greek regulations E39/99. Diagrams relating the curvature with the torsion moment have been obtained from the results of parametric analysis. These diagrams could be used by engineers for preliminary design of such kind of bridges.

Computer Simulation of Dynamic Interactions Between Vehicle and Long Span Box Girder Bridges

Moving vehicle loads, associated with roadway traffic can induce significant dynamic effects on the structural behaviours of bridges, especially for long-span bridges. The main objective of current research is to study traffic induced dynamic responses of long-span box-girder bridges. The finite element method has been employed in this study to obtain a three-dimensional mathematical model for the bridge system. For vehicle-bridge dynamic interaction analysis, the vehicle is modeled as a more realistic three-axle, six-wheel system, and the corresponding dynamic interaction equations have been derived. The bridge-vehicle interaction is affected by many factors. The current study has been focused on such factors as: vehicle speed, vehicle damping ratio, multiple traffic lanes, mass ratio of vehicle and bridge, and dynamic characteristics of bridge. Case studies have been conducted to investigate these factors by using several box girder bridge examples including Confederation Bridge, the longest box girder bridge in the world.

Refined analysis and construction parameter calculation for full-span erection of the continuous steel box girder bridge with long cantilevers

To accurately control the full-span erection of continuous steel box girder bridges with complex cross-sections and long cantilevers, both the augmented finite element method(A-FEM) and the degenerated plate elements are adopted in this paper. The entire construction process is simulated by the A-FEM with the mesh-separation-based approximation technique, while the degenerated plate elements are constructed based on 3D isoparametric elements, making it suitable for analysis of a thin-walled structure. This method significantly improves computational efficiency by avoiding numerous degrees of freedom(DoFs) when analyzing complex structures. With characteristics of the full-span erection technology, the end-face angle of adjacent girder segments, the preset distance of girder segments from the design position, and the temperature difference are selected as control parameters, and they are calculated through the structural response of each construction stage. Engineering practice shows that the calculation accuracy of A-FEM is verified by field-measured results. It can be applied rapidly and effectively to evaluate the matching state of girder segments and the stress state of bearings as well as the thermal effect during full-span erection.

Environmental noise beside an elevated box girder bridge for urban rail transit

Noise generated by trains running on elevated lines creates many disturbances to the normal lives of surrounding residents. Investigations have shown that people living along elevated lines complain that the noise is sometimes unbearable. To better control the noise and optimize the acoustic environment, noise spectrum characteristics were analyzed and compared with a field test and a numerical simulation. Through an energy analysis of the noise on the bridge side, the energy distribution characteristics of the noise at specific measuring points in different frequency bands were obtained. The influence of the Doppler effect on frequency shift was analyzed. Based on the partial coherence theory, a multi-input and single-output program was compiled to calculate the correlation and contribution degree of the bridge structure-borne noise and wheel/rail noise at the one-third octave center frequency. The results show that the peak noises of the bridge and the wheel/rail are concentrated at 31.5–63 Hz and 400–800 Hz, respectively. For environmental noise on the bridge side, the frequency band above 250 Hz is mainly affected by the wheel/rail noise. In areas of noise source strength, the relative ratio of noise energy above 250 Hz can reach 83.4%. Noise in the near ground and far bridge area is mainly low-frequency, and the relative energy ratio is about 8.9%. The Doppler effect has an influence of less than 6% on the frequency shift with a speed of 67.9 km/h. In the low-frequency band below 250 Hz, the noise in the acoustic shadow area near the bridge and the ground is mainly contributed to by the vibration-radiated noise of the bridge, of which the contribution of the bottom panel is the most prominent. The noise in the comprehensive noise area of the far bridge is mainly caused by the structure-borne noise of the bridge, and the contribution of each bridge panel is different. This study can provide a reference for finding the source of elevated rail noise in some challenging frequency ranges and for then determining optimal designs and measures for noise reduction.

Temperature Field of PC Box Girder Bridge Based on GPRS Temperature Collection System

In order to study the temperature distribution and the corresponding temperature effects on pre-stressed concrete（PC） curved box girder bridge in Shandong Province, this paper builds and adopts an automatic remote real-time temperature collection system to collect temperature data on site, and further uses the software ANSYS for analysis. Based on the comparisons between the measured data and the simulation results, the following conclusions can be drawn： 1 Our temperature monitoring system is reliable; 2 The corresponding measured data of the web plate and flange plate exposed to the sun, vary more severely than that at other positions, so these plates need higher standard design and construction requirements; 3 In the cold wave where still is sunshine, the box girder temperature effect behaves as sine-like curve.