Civil Engineering Reference
In-Depth Information
Current as-cast curve
Theoretical casting curve to reach
Match segment
Cast segment
Cast segment
Casting segment
Partially correct position
One step fully correct position
Figure 18.21
Error of as-cast curve and correction.
casting segment and the remaining error can be carried to the next segment.
This technique is called split error correction.
18.6.6 evolution of geometry control in
precast segmental bridge
The precast segmental bridge construction method was first developed in
1930s by French engineer Eugene Freyssinet. It was first practiced in 1973 in
the United States. Precasting and geometry control methods had long been
developed ever since. However, advancing of computer and survey technolo-
gies impacts the evolution of geometry control techniques. For example, the
modern computer software technologies have enabled controlling of more
sophisticated 3D curves and the replacement of traditional optical theodo-
lite by modern total station has greatly improved the survey accuracy and
field efficiency. Real-time survey and control technologies have also enabled
the automation of the whole process of measuring, calculating, and adjust-
ing (Kumar et al. 2008).
18.6.7 geometry transformation
As the underlying process of geometry control, geometry transformation is
the basis. The goal of geometry transformation is to find the ordinate repre-
sentation of a fixed point in another coordinate system, given that another
coordinate system is defined under one coordinate system. Geometry trans-
formation is also a primary process in computer graphics; its principle can be
widely found in computer graphics topics. One point that should be noted
is what is used of geometry transformation in match cast geometry control
is much simpler than what computer graphics may be used of. In computer
graphics, transformations are most aimed at object transforming, in which
a point is either translated/rotated along an axis or scaled. In this section,
Search WWH ::
Custom Search