Rehabilitation Of Steel Structures Research Articles

Rehabilitation of steel structures using innovative brace members equipped with YSPD damper

Earthquakes are serious risks to human life and infrastructure. An earthquake's influence on human life and its socioeconomic consequences highlight the need to investigate and create the most efficient and easily adaptable ways to minimize losses. The basic concept of different control mechanisms used for protecting structures from the destructive impacts of earthquakes is to dissipate the energy efficiently, therefore ensuring that the structure remains undamaged or sustains minimum damage. To achieve this purpose, the passive control mechanism is a particularly suitable and reliable technology as it doesn't rely on external power to actively dissipate energy. The present study proposes using a passive energy dissipation device called the Yielding Shear Panel Device (YSPD) for strengthening the current steel structures. The YSPD consists of a square hollow section (SHS) that houses a diaphragm plate. The fundamental concept of the YSPD involves harnessing the lateral deformation of a steel plate to absorb and disperse the seismic energy. The Bouc-Wen-Baber Noori (BWBN) material has been used for simulating the hysteresis force-deformation relationship of YSPDs by pinching. YSPDs are simulated as spring components that connect between the beam and the V-brace. A nonlinear time history dynamic analysis was performed to assess the alteration in the structural capacity with the setting up of YSPDs. The performance of the tested structure was assessed considering story drift, story displacement, story shear, column shear, and YSPD hysteresis loops. The results indicated that YSPD installation has improved the structure's capacity. However, the use of dampers resulted in significant drift in all stories, a reduction in total floor displacement, and a decrease in the shear force of the stories. However, the results demonstrated that the YSPD dampers effectively absorbed energy and exhibited stable hysteresis loops.

Modelling of Strengthened Steel Connections under Static and Cyclic Loading

The rehabilitation of steel structures with Fibre Reinforced Polymers (FRP’s) may appear less effective because they can be bolted or welded with steel plates that display the same mechanical properties. However, this technique has some unwanted consequences such as additional dead weight and an increased risk of corrosion. The aim of the proposed study, therefore, is to present a technique for modelling steel connections strengthened with FRP’s. Two types of composites: Carbon Fibre Reinforced Polymer (CFRP) and Glass Fibre Reinforced Polymer (GFRP) are considered. They are used to strengthen welded steel connections. The main objective consists in evaluating the effect of the reinforcement on the load-carrying capacity of these connections under monotonic and cyclic loadings. The steel is considered to behave in a linear elastic perfectly plastic fashion with isotropic strain hardening, and the FRP’s are assumed to behave linearly up to failure. The behaviour of the adhesive is modelled with the Cohesive Zone Model (CZM) available in Abaqus. Lastly, a parametric study is carried out to investigate the eventuality of strengthening connections made with I-sections, which are very common in practice.

Strengthening of thin-webbed castellated beam using CFRP

The utilisation of fibre reinforced polymers (FRP) in the rehabilitation of steel structures increased in recent years. This article presents the advantages of using carbon fibre reinforced polymers (CFRP) in strengthening of the thin-webbed castellated beam (TCB). The performances of CFRP strengthened TCBs were analysed using finite element (FE) tool ABAQUS®. Nonlinear FE analysis was carried out to find the optimum geometrical. Nine different designations of TCBs were arrived based on weld lengths, perforation sizes and strengthening technique (three each). Though all three techniques increased the strength considerably, the third one had much greater efficiency and was more suitable.

Analytical solution for stiffness prediction of bonded CFRP-to-steel double strap joints

Carbon fiber-reinforced polymer (CFRP) composites have been increasingly used in the strengthening and rehabilitation of steel structures. This paper presents an analytical model for stiffness prediction of CFRP-to-steel double strap joints. Mechanical analysis was performed to determine the shear stress and strain distributions in the bond region, which resulted in deriving a model for stiffness prediction of joints. More than 20 test results from the existing works in the literature were used to validate the proposed model. Results show that the predictions are mostly between 0.8 and 1.2 times the experimental values, with an average error of less than 10%, which demonstrates the effectiveness of the proposed model. Finally, a parametric study with respect to the bond length and the adherend stiffness ratio was performed to give a better understanding of the effect of different parameters.

Rehabilitation of notched circular hollow sectional steel beam using CFRP patch

The application of carbon fiber reinforced polymer (CFRP) composites for rehabilitation of steel structures has become vital in recent years. This paper presents an experimental program and a finite element (FE) modelling approach to study the effectiveness of CFRP patch for repair of notch damaged circular hollow sectional (CHS) steel beams. The proposed modeling approach is unique because it takes into account the orthotropic behavior and stacking sequence of composite materials. Parametric study was conducted to investigate the effect of initial damage (i.e., notch depth) on flexural performance of the notched beams and effectiveness of the repair system using the validated FE models. Results demonstrated the ability of CFRP patch to repair notched CHS steel beams, restoring them to their original flexural stiffness and strength. The effect of composite patch repair technique on post-elastic stiffness was more pronounced compared to the elastic stiffness. Composite patch repair becomes more effective when the level of initial damage of beam increases. Copyright © 2018 Techno-Press, Ltd.

Tensile behaviour of open-hole and bolted steel plates reinforced by CFRP strips

Abstract The behaviours of the open-hole and bolted plates in tension are fundamental in the mechanical assessment of the bolted connections. Regarding the rehabilitation of steel structures, however, the combined effects of bolted washer clamp-up and CFRP reinforcement on the tensile behaviour of the connection with laser cut holes have not been fully understood. This investigation aims to fill the gap by carrying out experimental tests and developing analytical model accounting for these effects. The test results show that the CFRP reinforced plates are failed by the rupture of CFRP and the steel-adhesive interface failure accompanied by CFRP delamination. Both failure modes can be correlated with two load-deformation characterizing curves. It is also found that the increase of the nominal tensile strength of the specimens can be enhanced significantly by the increase of the number of the CFRP layers and further moderately improved with the combined effect of the bolted washer clamp-up. Moreover, the yield load and residual deformability of the specimens can be significantly increased with the bolted washer clamp-up and greater bolt torque respectively. An analytical model taking into account the bolt torque effect and interfacial stress equilibrium has been developed to predict the strength enhancement effects of washer clamp-up and CFRP reinforcement on the open-hole plates in different failure modes. The proposed model has been verified to be effective in providing satisfactory strength ratio in contrast to test data.

An assessment of lead controls for torch cutting and rivet removal on steel structures.

The use of engineering and work practice controls to protect workers from lead-containing dusts and fumes generated during rehabilitation of steel structures is mandated by the Occupational Safety and Health Administration (OSHA) Lead in Construction Standard (1993). Because the implementation and assessment of controls can be problematic in the rugged and dynamic construction environment, industrial hygienists should understand the effectiveness and limitations of controls adopted. The present investigation assesses the efficacy of two controls to reduce lead exposure: paint removal prior to oxy-acetylene torch cutting of steel, and encapsulation of rivets prior to their removal. A task-based exposure assessment approach was used to evaluate these tasks at three sites. Exposures at one site without controls were compared to exposures at sites with controls. Comparison of the results via an analysis of variance (0.05 significance level) indicates that, for torch cutting, exposures at the control site were not significantly different from those at an uncontrolled site (p = 0.14). The results for rivet busting show no significant differences in exposures at the control site compared to the uncontrolled site (p = 0.08). Results are also presented from two control sites where work was done in enclosed spaces. Two main difficulties in applying the controls are explored: technical and managerial. Technical problems during torch cutting included the penetration of paint into the steel profile and the configuration of the structures. For rivet busting, working within an enclosure was an important factor. Management problems arose both from a lack of coordination among different contractors, and from a failure to provide day-to-day guidance and assessment of the control. Important components of a program to implement controls are preplanning and coordination of control implementation, frequent testing of control efficacy, and a method for timely intervention to correct deficiencies.