# Influence of Construction Joint and Bridge Geometry on Integral Abument Bridges
## 5 Conclusions  
This study investigated the influence of bridge design parameters that should be determined by bridge designers. The parametric study evaluated the effect of four parameters: (1) girder material, (2) AB joint stiffness, (3) backfill height, and (4) bridge length. The analysis results were evaluated for four critical response parameters: (1) girder axial force, (2) girder moment, (3) pile moment, and (4) pile head displacement. **Girder axial force**: bridge length most significantly influenced girder axial forces. Steel girder IAB response was clearly different from those of PSC bridges and tended to produce larger compressive forces and smaller tensile forces. As bridge length increased from 30.5 to 182.9 m, positive and negative steel girder axial forces increased 3.0 and 2.0 times larger than those of 30.5 m long IABs, respectively. Positive and negative PSC girder axial forces increased 7.5 and 3.1 times larger than those of 30.5 m long IABs. During bridge contraction, an increase of backfill height reduced at least 0.81 and 0.78 times less steel and PSC girder tensile forces than those of IABs with 3.1 m high backfill. However, the increase of backfill height increased steel and PSC girder axial forces to at most 1.2 and 1.5 times larger than those of IABs with 3.1 m high backfill. This tensile axial force in a PSC girder should be carefully undertaken during design process. Moreover, the largest girder axial forces, about 2500 and \(-\)2100 kN for PSC and 1800 and \(-\)2600 kN for steel girder IABs, that can occur during thermal movement should be considered in bridge design within the scope of this study. **Girder moment**: Bridge length and AB joint stiffness most significantly influenced the girder moments, because the superstructure moment induced by the thermal movement related to bridge length is transferred to the substructure through the AB joint. The negative moments in 182.9 m long steel and PSC girder IABs increased 2.24 and 2.87 times higher than those in 30.5 m long IABs. The AB joint stiffness influence on girder moment in steel girder IABs was opposite to those in PSC girder IABs. For steel girder IABs, hinged AB joints would reduce 41% girder moments compared with those with rigid AB joint. However, for PSC girder IABs, rigid AB joints would reduce 43% girder moments compared with those with hinged AB joint. Positive and negative PSC girder moments in 4.6 and 6.1 m high backfill increased 1.04 and 1.21 times higher and 3.95 and 5.52 times higher than those in 3.1 m high backfill. Negative steel girder moments in 4.6 and 6.1 m high backfill increased 1.09 and 1.35 times higher than those in 3.1 m backfill, while positive steel girder moments decreased 0.90 and 0.82 times. **Pile moment**: Bridge length, AB joint stiffness, and backfill height significantly influenced the pile moments. Pile moments increased as AB joint stiffness or bridge length increased. For AB joint stiffness, hinged joints showed less pile moment and rigid joints showed higher a pile moment. Steel girder IABs tended to produce larger pile moments than did PSC girder IABs. Pile moments in steel girder IABs with PA standard and rigid AB joint increased 1.52 and 2.14 times higher than those with hinged AB joint. Pile moments in PSC girder IABs with PA standard and rigid AB joint increased 1.17 and 1.60 times higher than those with hinged AB joint. Therefore, short PSC girder IABs with hinged AB joint and 4.6 m high backfill would be effective to reduce the pile moment. **Pile displacement**: Bridge length mainly influenced pile head displacement. Most of the considered cases for steel and PSC girder IABs were well below the free expansion prediction. A hinged construction joint and high abutment height tended to reduce pile head displacement in IABs. For bridge expansion, because of the backfill resistance increase, both PSC and steel girder IABs developed lower pile head displacements than free expansion predictions.