# Reliability Analysis of the Main Pier during the Construction Period of HLCR Bridges
## 3 Reliability Analysis of the Main Pier of an HLCR Bridge with a Cradle Construction
### Project Examples  
This special bridge across a river is difficult to construct and has a long construction cycle, with the total design requiring 79,024 tons of steel and 452,000 cubic meters of concrete. The whole bridge is designed in separate bridge sections; the main bridge is arranged as an 87 + 6 \(\times\) 160 + 87-m continuous rigid bridge. The total span length of the left bridge is L = 3057 m and of the right bridge is L = 3145 m. The layout of some of the bridge is shown in Figure 1. The maximum pile length of the main bridge part is 93 m, the maximum height of the bridge is 137 m and the maximum pier height is 125 m. The main pier spans 6\(\mu\)-12\(\mu\). Among these, 7\(\mu\)-12\(\mu\) adopts the form of a variable-section hollow pier; the upper 65 m of the variable section takes the form of double limbs laterally, the single-limb width is 6.5 m, the wall thickness of the hollow pier is 0.8 m, a horizontal partition is set every 20 m vertically, the wall thickness of the horizontal partition is 0.8 m and the hollow pier wall thickness is 0.8 m. The lower part of the hollow pier adopts an integral single-box and three-chamber structure, where the wall thickness is again 0.8 m. The longitudinal bridge adopts a variable section form, where the top width is 7.5 m, theslope rate is 1:80. The pier heights across 7#-12# are 122 m, 125 m, 120.5 m, 116 m, 116.5 m and 108 m, respectively. A pier design drawing is shown in Figure 2. The main bridge is arranged as an 87 + 6 \(\times\) 160 + 87-m single-box, single-chamber, box-type, variable-section, prestressed, concrete, continuous rigid bridge with a joint length of 1134 m. The height of the box girder and the thickness of the bottom plate are changed parabolically by 1.8 times. The height of the root girder at the center line of the box girder is 10.5 m. The height of the span and end girder is 4 m. The cross-section is a single-box, single-chamber, straight-web box girder. The width of the top plate is 12.25 m, the width of the bottom plate is 6.5 m and the length of the cantilever is 2.875 m. The section of block 0# is 14 m long. The thicknesses of the top plate, bottom plate and web are 0.7 m, 1.8 m and 1.1 m, respectively. The thickness of the top plate of other sections is 0.3 m. The thickness of the bottom plate is 1.8 times greater, parabolically curving from root 1.143 m to mid-span 0.32 m. The thickness of the web of blocks 1#-6# and 13#-18# are 0.80 m and 0.55 m, respectively, with blocks 7#-12# forming a transition section. The main girder is divided into 182 cantilevered sections on both sides of block 0#, with a segmental length of 2 \(\times\) (6 \(\times\) 3.5 + 6 \(\times\) 4 + 6 \(\times\) 4.5) meters, a side span cast-in-place section of 5.6 m and a 2-m section for both the middle and side span. A structural design drawing of the main bridge box girder is shown in Figure 3. The main bridge is constructed by seven \"T\" type symmetrical cantilevers cast-in-place on pairs 6, 7, 8, 9, 10, 11 and 12, except for the 0# girder section, which is cast in brackets beside the top of the pier. The heaviest suspended section was girder 1# with a weight of 2345.2 kN, and the cast-in-place section of the side span was erected with a beryl truss. The weight of hanging baskets and formwork is calculated as 1200 kN, the maximum deformation is no more than 0.02 m and the maximum allowable deviation of concrete pouring at both ends of the cantilever is no more than 3 m\({}^{3}\). The reliability of the main pier in the construction process is analyzed under unfavorable conditions.