earthquake;  (d) spalling of concrete cover (East side); (e) joint
foundation-S1 (West side); (f) joint S1-S2 .192
Figure 5.4.6.  Specimen C8P after cyclic loading test (West side) ..193
CHAPTER 1
INTRODUCTION 
1.1 Motivation 
Over the past few years, growing attention has been given to the investigation,
development and application of precast concrete bridge elements and systems for
highway bridges. Traditional cast-in-place concrete bridge construction projects normally
cause traffic disruption for long periods of time. The cost of this disruption to road users
can be very high in busy urban areas. Precast concrete bridge construction offers a viable
solution to the problem. It shifts most of the construction activities away from the
construction site and into precast factories where quality control is more reliable. After
adequate concrete strength has been obtained, precast concrete products are transported to
construction sites and assembled within a short period of time, thus minimizing traffic
disruption. Reducing on-site construction activities also means that work zone safety can
be improved and construction quality maintained, since the work environment in a
precast factory is safer and easier for workers to perform their jobs in terms of formwork,
reinforcing ironwork, concreting, compacting and curing. In addition, environmental
impact is reduced, since the demand on the land for construction purposes around the site
is decreased.  The disadvantages of using precast bridge construction as  opposed to cast-in-
place bridge construction include high initial cost and uncertainty about the performance
of precast connections or joints. High initial  cost is largely attributed to transporting
precast products from factories to construction sites and the additional hardware needed
for precast connections. In many cases, these higher costs may become less important if
the many benefits of using precast bridge construction are appropriately weighed.
However, unless the performance of precast connections can be ensured, engineers will
hesitate to use precast bridge construction. As a result, the development of any new
method of precast bridge construction will require rigorous research on the design details
of precast connections to ensure that they will perform as expected over the lifetime of
the bridge.     
Numerous bridge construction projects have successfully used precast concrete
construction in superstructures or substructures or both. Examples can be found in
FHWA (2006). Most precast segmental concrete column and pier construction in the U.S.
is used in areas of low seismicity, as shown in Figure 1.1.1, such as the states of Texas
and Florida. Some well-known examples include the Seven Mile Bridge, Sunshine
Skyway Bridge, Mid-Bay Bridge, and John T. Collinson Bridge in Florida and the
Louetta Road Overpass and U.S. Highway 183  Elevated in Texas.  Precast bridges in
other states include the Linn Cove Viaduct  in North Carolina, C&D Canal Bridge in
Delaware, Varina-Enon Bridge in Virginia, U.S. Highway 70 at Vail Pass in Colorado
(Muller and Barker 1985, Billington et al. 1999 and Figg and Pate 2004), and more
recently, Victory Bridge in New Jersey  (NJDOT 2005 and ASBI 2004) and Colorado River Bridge of Hoover Dam Bypass in Nevada (Structure Magazine 2006 and ASBI
2006). Photos of these bridges are shown in Figure 1.1.2. In regions of high seismicity,
such as the state of California, there has not been any application of segmental column or
pier construction (FHWA 2006). One important reason for this situation is that there is
limited knowledge about the seismic behavior of segmental columns and piers, in
particular, the seismic behavior of the segment joints in segmental columns and piers. 梁桥英文文献和中文翻译(7):http://www.youerw.com/fanyi/lunwen_12276.html