Faouzi Ghrib

Effect of the Number of Cross-Tie Lines on the In-Plane Stiffness and Modal Behavior Classification of Orthogonal Cable Networks with Multiple Lines of Transverse Flexible Cross-Ties

AbstractUsing cross-ties to connect a vulnerable cable with its neighbor(s) and forming a cable network is a common countermeasure to suppress bridge stay cable vibrations. An effective design of cross-tie solution should provide an optimum combination of cross-tie installation location, stiffness, and number of cross-tie lines to maximize the network in-plane frequency and structural damping while minimizing the number of excited local modes. However, the mechanics associated with cable networks is not as simple as their geometrical appearance. In particular, the addition of an extra line of cross-ties to an existing cable network would considerably increase the complexity of its structural behavior. While the effects of cross-tie position and stiffness on network response have been investigated in some existing studies, that associated with the number of cross-tie lines is scarce. For better understanding of how the dynamic behavior of a group of cables would be influenced when interconnected by differe...

Damage Identification of Euler–Bernoulli Beams Using Static Responses

AbstractThe paper presents two computational procedures to reconstruct the stiffness distribution and to detect damage in Euler–Bernoulli beams. A novel methodology of damage identification is developed using static deflection measurements. The first formulation is based on the principle of the equilibrium gap along with a finite-element discretization, and leads to an overdeterminate linear system. The solution is obtained by minimizing a regularized functional using a Tikhonov total variation (TTV) scheme. The second proposed formulation is a minimization of a data-discrepancy functional between measured and model-based deflections. The optimal solution is obtained using a gradient-based minimization algorithm and the adjoint method to calculate the Jacobian. Also discussed is a simple procedure to measure the deflection of beams using a close-range photogrammetry technique. An edge detection-based algorithm is devised for quasi-continuous deflection measurement. The proposed identification methodology ...

Development of finite element model for the analysis of a guardrail post subjected to dynamic lateral loading

The performance of a guardrail system depends on many factors where the interaction between the soil and the post plays a major role in the vehicle response. In this study, a computer simulation model of a rigid impactor impacting a roadside post has been developed and the interaction of cohesionless soil with a W152 × 13.4 post was studied and compared to the existing dynamic test results from the published literature. Two approaches have been studied: the continuum method where the soil was modelled as a solid element with Drucker and Prager material law and an upgraded subgrade approach where the soil was modelled as a system of parallel springs and dampers with a lumped mass attached to the post. The results of the new subgrade method and the continuum method were compared to the dynamic test. The new method shows very close results to the dynamic tests.

Behavior of RC Slab-Column Connections Strengthened with External CFRP Sheets and Subjected to Eccentric Loading

AbstractStrengthening of both aging and modern infrastructure has become necessary as a result of increased load demand and/or to restore the capacity of a member. For example, flat slabs (commonly utilized in parking garages) are subjected to an aggressive environment and increased traffic loads and additionally require strengthening and/or repair. Fiber-reinforced polymer (FRP) sheets and laminates externally bonded to concrete slabs around the slab-column joint are widely used to enhance the strength of flat slabs. Slab-column connections are most often subjected to eccentric loading; however, most reported studies have focused on retrofitted slab-column connections subjected to concentric loads. This paper aims to fill this knowledge gap and experimentally investigate the effect of eccentric loading on the behavior of slab-column connections retrofitted by externally bonded carbon fiber-reinforced polymer (CFRP) sheets. Six full-scale (2,000×1,000×150-mm) interior slab-column connections subjected to ...

Effect of crushable blockouts on a full-scale guardrail system

ABSTRACT 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.

Crashworthiness of guardrail posts embedded in cohesionless soils: a parametric study

ABSTRACT Guardrail systems are designed to provide a safe environment for vehicles and to reduce the severity of occupants’ injuries. The performance of this safety system is deemed to be vital to highway users. Guardrail post is probably the most important component of any guardrail system design. The evaluation of guardrail posts performance usually involves crash tests, which consist of colliding the post with a bogie. Crashworthiness tests try to cover a range of design parameters such as the soil resistance, impact velocity and blockout crushability. When reviewing the available various dynamic tests conducted to date, it is apparent that the range of the considered design parameters varies widely. Because of the lack of consistency of the diverse test conditions, the statistical analysis of the test results is not an easy task. In the present paper, the finite element method has been employed as a tool to conduct a parametric study and generate statistical data. The generated data are used to establish correlations between the post parameters and the system performance indicators.

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.