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The hybrid composite beam (HCB) is an innovative idea that incorporates traditional construction materials (i.e., steel and concrete) with fiber-reinforced polymer (FRP) composites in an efficient configuration to optimize the beam constituents’ performance. The HCB is comprised of three main subcomponents: a composite shell, a compression reinforcement, and a tension reinforcement. The shell is comprised of a glass-fiber-reinforced polymer (GFRP) box. The compression reinforcement consists of self-consolidating concrete (SCC) that is pumped into a profiled conduit within the shell. The tension reinforcement consists of galvanized-steel tendons anchored at the compression reinforcement ends. The HCB is a promising technology in bridge applications because it has several advantages over the conventional structural members (e.g., a prolonged lifetime and a lighter weight). This new technology was recently used to construct three bridges in Missouri. This research study performs the first investigation and analysis for an in-service HCB bridge superstructure’s behavior subjected to thermal loads and proposes a thermal design methodology. This investigation is crucial because the thermal stresses, if not accounted for during the design, can significantly affect a bridge superstructure’s durability, which this new HCB technology strives to address. Beam elements from the longest spanning HCB constructed bridge in Missouri were instrumented with various strain gauges and thermocouples. The constituting elements’ temperatures and the corresponding induced strains were recorded over 6 months. The proposed algorithm was used to predict the induced strains. A two-step thermostructural finite-element analysis (FEA) was performed to analyze the HCB’s thermal behavior and further evaluate the proposed algorithm’s performance. The results of this study showed that the proposed algorithm was able to predict, with acceptable accuracy, the thermal stresses and strains in a HCB bridge superstructure. Subsequently, this algorithm is recommended as a useful tool for designing and analyzing HCB bridges that are undergoing environmental thermal effects. The current study also presents recommendations for modifying the thermal gradients recommended by AASHTO for the thermal design of reinforced concrete (RC) superstructures to better suit HCB bridges. Finally, the study proposed techniques for increasing the stiffness of a HCB bridge superstructure, while at the same time minimizing the induced thermal stresses under temperature fluctuations. [ABSTRACT FROM AUTHOR]

Three bridges were recently constructed in Missouri using a new type of hybrid composite beam (HCB) incorporated within traditional RC deck systems. These HCBs are comprised of three main subcomponents: a composite shell, compression reinforcement, and tension reinforcement. The compression reinforcement is a self-consolidating concrete (SCC) arch that is tied at the ends by high-strength galvanized steel strands. The compression and tension reinforcements are encapsulated in a glass fiber-reinforced polymer (GFRP) box, and the voids are filled with polyisocyrunate (polyiso) foam. This unique configuration aims to optimize the structural performance of the HCB constituents, hence optimizing the overall performance of the beam. However, because of the novelty of the HCB, its structural behavior is not yet completely understood. Consequently, the finite-element (FE) modeling of this new type of beam is crucial for providing deeper insight into its structural behavior and validating the current design assumptions. It is, therefore, the main goal of this study to examine the accuracy of linear FE analysis (FEA) in predicting the static behavior of the HCB under service loads. This paper explains in detail the FE modeling of the superstructure of one of the recently constructed HCB bridges, using two commercial FEA packages. A field load test that simulates several load cases was applied to the bridge, and the deflections of the HCBs were measured at different locations. A simple analytical procedure that is based on the transformed area method is also used to predict the HCB deflections. The comparison between measured deflections and predicted deflections shows that the FEA can predict the HCB bridge behavior with acceptable accuracy, whereas the theoretical procedure significantly overestimates the beams' deflections. Finally, the two FE models are used to analyze the behavior of the HCBs. [ABSTRACT FROM AUTHOR]