Performance and Analysis of Concrete Bridge Railing using Conventional and Composite Reinforcement Materials

Federal Highway Administration2018PDFTech ReportAlaywan, Walid R.Louisiana Transportation Research CenterLouisiana. Department of Transportation and DevelopmentUnited States. Federal Highway AdministrationLouisiana Transportation Research CenterUnited StatesLouisianaBridge railingsConcrete structuresYield line methodCollapsePrecast concreteInstrumentationField testsPrecast barriersyield line theoryFHWA/LA.16/547The guidelines proposed by the NCHRP Report 350 pertaining to the safety of roadway hardware devices necessitated the evaluation of those devices. This study deals with the strength evaluation of precast concrete bridge railing that is a part of the roadway hardware devices. Though many articles, reports, and publications were found regarding the testing of cast-in-place concrete barriers, similar publications pertaining to precast concrete bridge railing were almost non-existing and so testing a precast concrete barrier was the focus of this study. The study of the performance of a concrete barrier with composite reinforcement was not warranted since such barriers can be replaced if they get damaged and investing in composite reinforcement would not be a good decision. The theoretical work was performed using the yield line theory to predict the strength of the precast barrier. Though the theory was developed for cast-in-place barriers where the lateral impact force would be transferred to the reinforcement in the deck, there was no developed equations for evaluating the strength of the precast or bolted section. The theory was tested in this study. The experimental work consisted of casting, instrumenting, testing, and evaluating data collected afterwards. Even though the reinforcement pattern remained unchanged along and across the faces of the barrier throughout, the section capacity of the barrier at the end region was smaller and thus, controlled the ultimate yield strength of the barrier. This is due to the end region being semi-continuous, unlike the intermediate region of the barrier. This led to different failure patterns. The failure of the precast section was in torsion of the wall followed by concrete break out at some anchor locations. This result is due to the different mechanisms through which a cast-in-place barrier and a precast barrier transfers the applied load to the deck. The measured resistive force at the intermediate section ranged from 40 kips (first appearance of cracks) to 79 kips (failure of the section) while the estimated value was 83 kips. Since the barrier collapsed while testing the intermediate region, testing of the end region could not be carried out. Since the transverse force causing failure of the end region is the controlling one and could not be verified, the estimated value of that resistive force (56 kips) could be used to conservatively imply that this barrier is TL-2 compliant. The use of this section should be limited to conditions that qualify for TL-2, i.e., work zones and most local and collector roads as well as where a small number of heavy vehicles is expected and posted speeds are reduced. Speed limit in work zones is limited to 45 mph. However, by properly designing the section and the anchoring detail, the performance of this barrier may upgraded to comply with TL-3 requirements, or higher, after successful full-crash testing.119