Stay Cables Research Articles

Development of Cable-Exciting System for Evaluating Modal Damping of Stay Cables

Development of Cable-Exciting System for Evaluating Modal Damping of Stay Cables

Development of Cable-Exciting System for Evaluating Modal Damping of Stay Cables

One of the effective alternatives to suppress hazardous vibration of stay cables is to use cable dampers. In order to design the cable damper optimally, it is necessary to exactly estimate the dynamic characteristics of existing cables. To estimate more reliable dynamic properties of stay cables, precise excitations inducing forced vibration are needed. Hence, in this paper, a cable-exciting system (cable exciter) controlled digitally is developed. A design formula for the cable exciter is also derived by the solution of the equation of motion of a cable-exciter system. The performance of the cable exciter is verified by sine sweeping tests and resonance tests for a cable model in a laboratory. Also from those tests, more reliable dynamic properties of the cable model are obtained. Thus, it is ascertained that modal damping of stay cables is proportional to the amplitude of cable vibration.

Development of Cable-Exciting System for Evaluating Modal Damping of Stay Cables

Development of Cable-Exciting System for Evaluating Modal Damping of Stay Cables

Constructability Concepts in Kuala Selangor Cable-Stayed Bridge in Malaysia

The writers formulated a case study of the Kuala Selangor Cable Stayed Bridge to examine the application of the constructability concepts particularly during the conceptual planning and the design phases of the project. This paper presents the advantages of implementing the constructability concepts and the barriers that were encountered when applying these concepts during the planning and design phases of the cable stayed bridge project of Kuala Selangor in Malaysia. The writers concluded that barriers to constructability implementation that are related to the owner were the major impediments in the application of constructability concepts during the early conceptual planning phase. The opinion of the engineer was another factor behind nonapplication of some other concepts. At the same time, many others were implemented due to the awareness and opinion of the engineer and his ability to control their application.

Nonlinear Periodically Forced Vibration of Stay Cables

A new method for analyzing nonlinear steady-state dynamic response of three-dimensional sagged stay cables subject to arbitrary periodic excitation is proposed in this paper. Firstly, the nonlinear governing equation of motion of a stay cable with arbitrary sag is formulated in terms of three-node curved finite elements. Then a frequency-domain solution method to obtain the periodically forced response is developed by applying the incremental harmonic balance (IHB) technique to the finite element model. The proposed method is an accurate algorithm in the sense that it accommodates multi-harmonic components and no mode-based model reduction is made in the solution process. Both frequency- and amplitude-controlled algorithms are formulated and are alternatively implemented to obtain complete frequency-response curves including unstable solutions. The proposed method enables direct solution to the sub- and super-harmonic resonances, and gives a way to analyze nonlinear periodic oscillation under parametric excitation and internal resonance. Case study of applying the proposed method to nonlinear dynamic behavior analysis of the Tsing Ma suspension bridge cables is demonstrated. The analysis results show that the side-span free cables of the bridge display distinctly different nonlinear characteristics in the construction stage and in the final stage.

Three-Dimensional Localization of Defects in Stay Cables Using Magnetic Flux Leakage Methods

The application of magnetic flux leakage (MFL) methods to the nondestructive evaluation (NDE) of metal parts has been known for several decades. The inspection of large-diameter cables (O ≥ 100 mm), such as bridge stay cables, is a new field of application for the MFL method. The large cross-section of the cables requires the generation of strong magnetic fields in order to obtain the induction fields necessary for an accurate inspection of the cables. A new device for the inspection of stay cables has been developed in order to meet the requirements given by the size of the cables. Measurements performed with the developed device on full-scale specimens in the laboratory and first calculations confirm the validity of the MFL approach to the inspection of bridge stay cables. The equipment was used satisfactorily in 2001 for the NDE inspection of the 68 locked coil stay cables (121 mm < O < 167 mm) of a bridge in Southeast Asia. For such cables, no exact localization within the cross section was performed. Thus far, an accurate indication of the position of the detected flaws along the length of the cables could be given. A qualitative statement about position and size of the flaws within the cross section of the cable could also be made. Given the large steel cross-section of the cables, no other nondestructive method to confirm the findings could be applied to assess the exact size and position of the detected flaws. The proposed analytical method presented in this paper makes it possible to increase the amount of information that can be extracted from the measured MFL data with regard to the exact location of the detected flaws within a cross section of a stay cable.

Rain-Wind Induced Vibration of Stay Cables: Experimental Results and Numerical Interpretation

Rain-Wind Induced Vibration of Stay Cables: Experimental Results and Numerical Interpretation

Design of Stay Cables for the Main Bridge of Zhangzhou War Preparedness Bridge

Design of Stay Cables for the Main Bridge of Zhangzhou War Preparedness Bridge

Installation of Stay Cables for Zhangzhou War Preparedness Bridge

Installation of Stay Cables for Zhangzhou War Preparedness Bridge

Construction Supervision of the Stay Cable of Zhangzhou War Preparedness Bridge

Construction Supervision of the Stay Cable of Zhangzhou War Preparedness Bridge

Protection of Stay Cable System

Protection of Stay Cable System

Bending of Stay Cables

The bending stresses in stay cables subjected to varying axial forces and imposed end rotations are investigated. It is shown that these stresses can be effectively reduced by a suitable rotation of the anchorages with respect to the chord lines and by guiding the cables at their end, providing a sufficiently stiff support at a certain distance from the anchorage. Recommendations for appropriate guide lengths and stiffness are given.

Construction Technology of HDPE Sheath for Stay Cable

Construction Technology of HDPE Sheath for Stay Cable

Construction Technology for Manufacturing and Installing Stay Cables of Zhangzhou War Preparedness Bridge

Construction Technology for Manufacturing and Installing Stay Cables of Zhangzhou War Preparedness Bridge

Design of Mechanical Viscous Dampers for Stay Cables

External dampers have been utilized in a number of cable-stayed bridges to suppress transverse cable vibrations. However, simple and accurate damper design recommendations that concurrently consider all important cable parameters are lacking. Previous efforts have been based on the idealization of cables as taut strings. In this paper, the governing differential equation for vibration of cables containing a viscous damper was first converted to a complex eigenvalue problem containing nondimensional cable parameters. Then, a parametric study was conducted involving repeated solutions of the eigenvalue problem for a wide range of nondimensional parameters. Based on the results of the parametric study, the effects of dampers on first mode vibration frequencies and first mode cable damping ratios were presented in nondimensional format. It is shown that for the range of parameters involved in most stay cables, the influence of cable sag is insignificant, whereas the cable bending stiffness can have a significant influence on the resulting cable damping ratios. Simplified nondimensional relationships are proposed for calculating damper-induced changes in the first mode cable damping ratios. Results of laboratory tests on a scaled model cable are compared with the estimated values using the formulation presented. Finally, example problems are presented for comparison with other relationships, and for the design of mechanical viscous dampers for suppression of cable vibrations including rain-wind induced vibrations.

Construction of Stay Cables for Vietnam Delong Bridge

Construction of Stay Cables for Vietnam Delong Bridge

Huerfanos Footbridge, Santiago, Chile

The Huerfanos Footbridge is the first cable-stayed bridge in Santiago. Stay cables were used for this particular project due to aesthetic considerations because the bridge is located in a highly populated zone of Santiago. The needs of the pedestrians could have been resolved with a traditional steel bridge, but the client wanted a new landmark for Santiago, at a reasonable cost.

Brazawi Bridge: Damage and Renewal of Stay Cables

Brazawi Bridge: Damage and Renewal of Stay Cables

Bridge Stay Cable Corrosion Protection. I: Grout Injection and Load Testing

This paper is the first of two companion papers that cover the results of corrosion and structural testing of eight large-scale stay cable specimens. Four of the specimens had the traditional stay-cable corrosion protection system of portland cement (PC) grout and high-density polyethylene (HDPE) sheathing, whereas the second four specimens used improved protection systems such as epoxy-coated, galvanized, greased, and sheathed strand or am improved grout with silica fume in the grout. A unique accelerated corrosion testing technique developed for bridge stay cables is also described. Among other critical findings, it was found that the PC grout would crack within 2-3 days after the exterior sheathing was cut to simulate accidental breaks in the field. It was also found that precompressing the grout was not effective in reducing the amount and size of cracks in grout. In addition, it was found that the presence of grout did not significantly increase the axial or flexural stiffness of the test specimens.

Bridge Stay Cable Corrosion Protection. II: Accelerated Corrosion Tests

This paper is the second of two companion papers that cover the results of corrosion and structural testing of eight large-scale stay cable specimens. Four of the specimens had the traditional system of portland cement (PC) grout and high-density polyethylene (HDPE) sheathing, while the other four specimens used improved protection systems such as epoxy-coated, galvanized, greased, and sheathed strands, or a grout improved with silica fume. A unique accelerated corrosion testing technique developed for bridge stay cables is also described. The traditional system of corrosion protection broke down almost immediately after the initiation of the accelerated corrosion test, while the improved corrosion protection systems provided far better corrosion protection than the traditional system. However, some problems were encountered with the improved corrosion protection systems that are of interest.