STR-961: FRP SHEAR CONNECTORS FOR REINFORCED CONCRETE COMPOSITE ELEMENTS

Currently, friction shear dowels (steel stirrups) are being used in bridge construction at the interface plane between the cast-in-place deck slab and the precast girder to ensure the composite action for stronger cross section. As the bridge deck slab deteriorated over time due to the environmental conditions, these shear steel dowels are also susceptible to sever corrosion and will need replacement, especially when de-icing salt is used. This results in gradual loss of the composite behavior and strength of the composite section. Fiber reinforced polymers (FRPs) reinforcements have shown to be an effective alternative to black steel as flexure and shear reinforcement for RC elements over the past 10 years. This research project aims to investigate a new application for FRP reinforcement as friction shear reinforcement between the precast and cast-in-place concrete members to overcome the corrosion problem and the corresponding high maintenance cost. This paper investigates the visibility of using FRP as shear-friction reinforcement (connectors) through push-off experimental tests on concrete specimens with Glass FRP (GFRP) shear connectors. The tested parameters included the shear connector’s reinforcement ratio, geometry and layout. Test results are presented in terms of comparisons of the ultimate capacity and failure mode against steel reinforced ones as well as load-slip and load-strain relationships. Test results indicates an outstanding capacity and behavior of GFRP shear connectors compared to steel ones

STR-962: FLEXURAL STRENGTHENING OF RC BEAMS USING GLASS-FRCM

Externally bonded Fiber reinforced polymer (FRP) sheets made of fiber net embedded in epoxy matrix has been successfully used in the repair and strengthening of both the shear and flexural capacities of reinforced concrete (RC) beams, slabs and columns since the 90\u27s. Although the epoxy gives the system most of its durability, it is also responsible for many disadvantages, such as poor performance in elevated temperature and fire, lack of permeability, as it traps moisture, and degradation when exposed to ultraviolet radiation. In order to avoid such drawbacks, composite material utilizing cement-based matrix called Fabric Reinforced Cementitious Matrix (FRCM) has been recently introduced. The FRCM system consists of fiber-reinforced composites in the form of meshes or grid embedded in a cementitious bonding material. This research investigated the flexure strengthening of reinforced concrete (RC) beams with glass-FRCM. The experimental study included characterization of the mechanical properties of GFRCM through axial tensile testing on 20 coupon specimens. Also, four large scale, 150 mm x 250 mm x 2400 mm, reinforced internally with steel bars had been constructed, strengthened in flexure with FRCM and tested under four-point bending. The investigated parameters included the internal steel reinforcement ratio. Test results showed that GFRCM did not affect the ultimate load capacity of the beams, however, the ultimate midspan deflection was increased. Debonding/Delamination of the FRCM was observed. Continuation of this research is going on, on which U-wrapped strips will be used to ensure no debonding of the FRCM from concrete substrate

Effect of crushable blockouts on a full-scale guardrail system

Since the performance of the guardrail system depends in part on the compatibility of vehicle-to-roadside hardware, it is important to improve the interaction of the vehicle with the guardrail system by adding more compliance to the guardrail system. In this paper, a finite-element baseline model of a guardrail system consisting of a light truck (2000 kg) travelling at 100 km/h and striking a guardrail was developed in accordance with the NCHRP Report 350 guidelines for Test Level 3 safety performance. The model was validated through comparison to a full-scale test conducted by the Texas Transportation Institute. In order for the guardrail system to absorb more energy and offer better stability to the vehicle, a rigid wooden blockout was replaced by a new crushable blockout design that was evaluated at the component level. The new blockout was formed by three crash cans and triggered at the corner, then was implemented in the full-scale model. The results of the analysis indicate that the both models satisfy the requirements of NCHRP Report 350 for the Test 3-11 conditions and show that the crushable blockout offers better vehicle stability in terms of roll angle and vehicle deceleration.Scopu

Impact of Cross-Tie Properties on the Modal Behavior of Cable Networks on Cable-Stayed Bridges

Dynamic behaviour of cable networks is highly dependent on the installation location, stiffness, and damping of cross-ties. Thus, these are the important design parameters for a cable network. While the effects of the former two on the network response have been investigated to some extent in the past, the impact of cross-tie damping has rarely been addressed. To comprehend our knowledge of mechanics associated with cable networks, in the current study, an analytical model of a cable network will be proposed by taking into account both cross-tie stiffness and damping. In addition, the damping property of main cables in the network will also be considered in the formulation. This would allow exploring not only the effectiveness of a cross-tie design on enhancing the in-plane stiffness of a constituted cable network, but also its energy dissipation capacity. The proposed analytical model will be applied to networks with different configurations. The influence of cross-tie stiffness and damping on the modal response of various types of networks will be investigated by using the corresponding undamped rigid cross-tie network as a reference base. Results will provide valuable information on the selection of cross-tie properties to achieve more effective cable vibration control