Title page for ETD etd-11072006-150416

Type of Document Dissertation
Author Shi, Xiaomin
Author's Email Address xshi1@lsu.edu
URN etd-11072006-150416
Title Structural Performance of Approach Slab and Its Effect on Vehicle Induced Bridge Dynamic Response
Degree Doctor of Philosophy (Ph.D.)
Department Civil & Environmental Engineering
Advisory Committee
Advisor Name Title
Steve C. S. Cai Committee Chair
Ayman M. Okeil Committee Member
George Z. Voyiadjis Committee Member
Su-Seng Pang Committee Member
Chunyan Li Dean's Representative
  • approach slab
  • trucks
  • bridges
  • dynamics
  • impact factor
  • road surface
Date of Defense 2006-10-09
Availability unrestricted
Differential settlement often occurs between the bridge abutment and the embankment soil. It causes the approach slab to lose its contacts and supports from the soil and the slab will bend in a concave manner. Meanwhile, loads on the slab will also redistribute to the slab ends, which may result in faulting (or "bump") at the slab ends. Once a bump forms, repeating traffic vehicles can deteriorate the expansion joint in turn. In this case, the vehicle receives an initial disturbance before it reaches the bridge. This excitation introduces an extra impact load on the bridge and affects its dynamic responses. The present research targets at the structural performance of the approach slab as well as its effect on the vehicle induced bridge vibration.

Firstly, the structural performance of the approach slab is investigated. Based on a parametric study, a correlation among the slab parameters, deflections, internal moments, and the differential settlements has been established. The predicted moments make it much easier to design the approach slab considering different levels of embankment settlements. While flat approach slab may be used for some short span applications, large span length would require a very thick slab. In such case, ribbed approach slabs are proposed, providing advantages over flat slabs. Based on finite element analysis, internal forces and deformations of ribbed slabs have been predicted and their designs are conducted.

Secondly, a fully computerized vehicle-bridge coupled model has been developed to analyze the effect of approach slab deformation on bridges’ dynamic response induced by moving vehicles. With this model, the dynamic performance of vehicles and bridges under different road conditions (including approach slab deformation) can be obtained for different numbers and types of vehicles, and different types of bridges. A parametric study reveals that the deformation at the approach span causes significant dynamic responses in short span bridges. AASHTO specifications may underestimate the impact factors for short bridges with uneven joints at the bridge ends.

Finally, this study investigated the possibility of using tuned mass damper (TMD) to suppress the vehicle-induced bridge vibration under the condition of uneven bridge expansion joints.

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