Abstract
Concrete box-girder bridges are widely used in China. During several routine inspections of two-year-old highway bridges of this type in the China Central Plains region, we found that transverse cracks are widespread on the bottom flanges of those box girders, mainly distributed in the area of 1/4L to 3/4L of the span. Selected cracks were then monitored continuously for one year. Our results showed that there had been no change in the widths of the cracks, but their lengths had increased and new cracks had formed. Taking into consideration factors like hydration reaction, relative humidity difference, shrinkage and creep, sunlight thermal differential effect, sudden temperature change, vehicle load, and their combined efforts, we have developed spatial structural models and conducted stress analyses on the reinforced concrete and prestressed concrete box-girder bridges, respectively. Our numerical analysis results indicated that the hydration reaction is the main reason for the initial bottom flange crack and the temperature difference between the inside and the outside of the box girders caused the crack developments at the later stage.
Highlights
Concrete bridge structures are influenced by a variety of natural conditions where environmental thermal actions, such as solar radiation, ambient temperature, and wind, play major roles
For a prestressed concrete bridge, the results of the calculation by Condition 3 show that the stress of the bottom slab is between 1.9 and 2.3 MPa when affected by dead load, temperature difference, and prestressed force
We have studied in this paper the influence of the temperature on the cause of cracking in concrete box-girder bridges, based on our inspections of highway bridges of this type in the China Central Plains region. e cause of cracking was first investigated, followed by the case study on the field measurement
Summary
Concrete bridge structures are influenced by a variety of natural conditions where environmental thermal actions, such as solar radiation, ambient temperature, and wind, play major roles. Most cracks on prestressed concrete box-girder bridges were caused by thermal stress. Researchers concentrated on the temperature difference in sunlight when the study of thermal stress in concrete box-girder bridges was conducted. With the development of computer technology, the main numerical methods of stress analysis of box-girder bridge are finite element method and meshless method. Meshless method is based on the nodes to establish approximation function, and it does not need the remesh of the solution domain when studying large deformation problems. It can increase the density of nodes to obtain the solutions with higher-computational accuracy [13]. Over the last two decades and especially in recent times, smart materials have attracted immense interest and have been studied intensively worldwide by both intradisciplinary and multidisciplinary research groups [16]
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