Abstract
In recent years, the use of modular bridge deck components has gained popularity for facilitating more durable components in bridge decks, but these components require field-applied connections for constructing the entire bridge. Ultra-High-Performance Concrete (UHPC) is being extensively used for highway bridges in the field connections between girders and deck panels for its superior quality than conventional concrete.
Thus far, very limited data is available on the modeling of hybrid-bridge deck connections. In this study, finite element models have been developed to identify the primary properties affecting the response of hybrid deck panel system under monotonic and reverse cyclic loads. The commercial software ABAQUS was used to validate the models and to generate the data presented herein. The concrete damage plasticity (CDP) model was used to simulate both the conventional concrete and UHPC. In addition, numerical results were validated against experimental data available in the literature. The key parameters studied were the mesh size, the dilation angle, reinforcement type, concrete constitutive models, steel properties, and the contact type between the UHPC and the conventional concrete. The models were found to capture the load – deformation response, failure modes, crack patterns and ductility indices satisfactorily. The damage in concrete under monotonic loading is found higher in normal concrete than UHPC with no signs of de-bonding between the two materials. It is observed that increasing the dilation angle leads to an increase in the initial stiffness of the model. Changing the dilation angle from 20° to 40° results in an increase of 7.81% in ultimate load for the panel with straight reinforcing bars, whereas for the panel with headed bars, the increase in ultimate load was found 8.56 %.
Furthermore, four different types of bridge deck panels were simulated under reversed cyclic loading to observe overall behavior and the damage pattern associated with the reversed cyclic load. The key parameters investigated were the configurations of steel connections between the precast concrete deck elements, the loading position, ductility index, and the failure phenomena. The headed bar connections were found to experience higher ductility than the ones with straight bars in the range of 10.12% to 30.70% in all loading conditions, which is crucial for ensuring safe structural performance. This numerical investigation provides recommendations for predicting the location of the local damage in UHPC concrete bridge deck precast panel connections under reversed cyclic loading.
Despite of having excellent mechanical and material properties, the use of Ultra-High-Performance Fiber Reinforced Concrete (UHP-FRC) is not widespread due to its high cost and lack of widely accepted design guidelines. This research also aims to develop a UHPC mixture using locally and domestically available materials without heat curing in hopes of reducing the production cost. Several trial mixtures of UHPC have been developed using locally available basalt and domestically available steel fibers. Among them, one trial mixture of 20.35 ksi compressive strength was selected for further study. To investigate the applicability of this locally produced UHPC in bridge closure, two full scale-8 ft. span hybrid bridge deck slabs with UHPC closure were constructed and tested under monotonic loading to identify the structural and material responses. The load- deflection response of the hybrid connection confirms that the deflection increased linearly until the initiation of first crack, after that it increased non-linearly up to the failure of the connection. The strain response also confirms that UHPC experiences less strain than normal strength concrete under compression loading. In addition, a moment curvature analytical graphical user interface model of hybrid bridge deck connection has been developed using MATLAB to predict ductility, curvature, and the stress distributions in those connections. The predicted value of moment and curvature from the code was found in good agreement with experimental data as well. The code provides a tool to professional engineers to predict ductility, curvature, and the stress distributions in those connections. The code is built in such a way to allow various input parameters such as concrete strength, dimensions of hybrid connection and deck panels, reinforcement configuration and the shape of the connection.
Though, ultra-high-performance fiber reinforced concrete (UHP-FRC) has very high compressive strength compared to conventional concrete, the failure strain of UHP-FRC is not enough to withstand large plastic deformations under high stain rate loading such as impact and blast loading. Hence, a numerical study has been conducted to simulate low-velocity impact phenomenon of UHP-FRC. The responses obtained from the numerical study are in good agreement with the experimental results under impact loads. Five different types of UHP-FRC beams were simulated under impact loading to observe the global and local material responses. The key parameters investigated were the reinforcement ratio (ρ), impact load under various drop heights (h), and the failure phenomena. It was observed that higher reinforcement ratio showed better deflection recovery under the proposed impact. Also, for a specific reinforcement ratio, the maximum deflection increases approximately 15% when drop height decreases from 100 mm to 25 mm. Moreover, the applicability of concrete damage plasticity model for impact loading is investigated. The results also provided recommendations for predicting the location of the local damage in UHP-FRC beams under impact loading.
Moreover, this research work includes a nonlinear finite element analysis of high-strength concrete confined with opposing circular spiral reinforcements. The spiral reinforcement is a very common technique used for reinforcing columns in active seismic regions due to its high ductility and high energy absorption. The results are compared with previously tested small-scale concrete columns made with the same technique under monotonic axial loads. The proposed technique is developed to improve the strength and ductility of concrete columns confined with conventional spiral systems. The finite element (FE) analysis results have shown that the proposed model can predict the failure load and crack pattern of columns with reasonable accuracy. Beside this, the concrete plasticity damage showed very good results in simulating columns with opposing spirals. The FE model is used to conduct a study on the effect of spiral spacing, γ (ratio of the core diameter to the whole cross section diameter) and compressive strength on the behavior of circular spiral reinforced concrete columns confined with opposing circular spiral reinforcements. The results of the parametric study demonstrated that for the same spacing between spirals and same strength of concrete, increasing γ increases the failure load of the column. It is also observed from the study that the ductility of the studied columns is not affected by changing the value of γ. In addition, a correlation between the γ factor, three different compressive concrete strengths, and the spacing of opposing spirals was developed in this study.