David T. Lau

Modelling of contraction joint and shear sliding effects on earthquake response of arch dams

In an arch dam, adjacent monoliths separated by vertical contraction joints may move relative to each other during an earthquake, resulting in the gradual opening and closing and possible shear movement at the joint surfaces. This paper presents the formulation of a joint constitutive model for a zero-thickness joint element that can simulate both the opening and closing and shear sliding behaviour, as well as the non-linear shear key effects of the joint. The proposed joint element has been implemented in the concrete arch dam finite element analysis program ADAP-88. The response of a typical arch dam subjected to earthquake ground motion is presented to demonstrate the capability of the proposed joint model. Results from a parametric study carried out to study the sensitivity of the response to the joint properties are discussed. The joint parameters considered in the parametric study include apparent cohesion, friction coefficient, and whether the joint has beveled or unbeveled shear key, or the joint is unrestrained in shear sliding. The analysis results show that joint opening and shear slippage at the contraction joints can have significant effects on the response of an arch dam.

Real-Time Data Processing, Analysis and Visualization for Structural Monitoring of the Confederation Bridge

Numerous structural monitoring systems have been developed and installed in the field to collect information on the performance and behaviour of civil engineering structures and systems, such as buildings and bridges. The processing and analysis of large datasets collected from continuous monitoring systems often require a significant amount of time and effort. In order to accelerate the processing of these continuous monitoring data and to facilitate more rapid data analysis, and more timely interpretation and use of the results, a real-time data processing and analysis application platform has been developed which encompasses all aspects of data manipulation. This application platform consists of data processing, analysis and visualization modules, all integrated through graphical user interfaces (GUIs). The applications are designed and adapted to run in a real-time mode by automatically sorting incoming data and re-directing it to the processing and animation modules for graphic display of bridge displacements and motion in near real-time, as limited by the network speed. With this capability, after the occurrence of extreme events such as windstorms, earthquakes or ship impacts, bridge responses and condition of the facility can be assessed in a timely manner for decision support of its operation. The research opportunities that can be explored using the computer tool applications presented in this paper are illustrated by a discussion of recent research results.

Comparison of numerical techniques for 3D flutter analysis of cable-stayed bridges

This paper presents the results of a comparison study of the numerical techniques of structural and aerodynamic force models developed based on the spline finite strip method with the conventional finite element approach in three-dimensional flutter analysis of cable-stayed bridges. In the new formulation, the bridge girder is modelled by spline finite strips. The mass and stiffness properties of the torsional behaviour of complex bridge girder, which have a significant influence on the wind stability of long-span bridges, are modelled accurately in the formulation. The effects of the spatial variation of the aerodynamic forces can be taken into account in the proposed numerical model by distributing the loads to the finite strips modelling the bridge deck. The numerical example of a 423 m long-span cable-stayed bridge is presented in the comparison study. The accuracy and effectiveness of the proposed finite strip model are compared to the results obtained from the equivalent beam finite element models. The advantages and disadvantages of these different modelling schemes are discussed.

A cloud-based approach for smart facilities management

One of the problems with the current practices in the various domains of facility management is that each facility is managed by its stake holder in isolation from the management of other similar facilities. However, with the advent of new technologies such as cloud computing, we have an opportunity to unify the management of multiple geographically dispersed facilities. To that end, this paper presents our joint research efforts on cloud-based smart facility management. More precisely, we present a cloud-based platform in order to manage sensor-based bridge infrastructures and smart machinery. Although the paper focuses on these two applications, the proposed cloud-based platform is designed to support/manage a multitude of smart facilities.

A Cloud-Based Platform for Supporting Research Collaboration

This paper describes a cloud-based platform, called RP-SMARF, for supporting research collaboration in the area of smart facilities management. More precisely, the proposed system delivers sophisticated domain-specific services to users by linking together disparate privately-owned elements such as data repositories, specialized hardware resources and specialized software applications into a unified framework. This allows research collaborators within a knowledge domain to easily run complex applications developed by researchers within the domain on complex datasets. Both batch-type processing as well as interactive application access are supported by the platform. The processing of live data streams generated in one site by an application residing in another site can also be performed. An authorization framework allows element owners to precisely control which users can access various elements. RP-SMARF unifies geographically dispersed heterogeneous resources for research collaborators. This simplifies making software created by researchers more usable by other researchers thereby making many researchers more productive.

In-Plane Seismic Strengthening of Nonductile Reinforced Concrete Shear Walls Using Externally Bonded CFRP Sheets

AbstractThis study evaluated the effectiveness of using externally bonded carbon fiber–reinforced polymer (CFRP) sheets to enhance the seismic performance of nonductile reinforced concrete shear wall specimens representative of low aspect ratio walls. The specimens were designed to replicate structural deficiencies typically found in older concrete structures constructed during the 1960s and 1970s. The nonductile reinforcement details included insufficient shear reinforcement, lack of boundary elements, and low concrete compressive strength. The specimens were repaired or strengthened using vertical and horizontal CFRP sheets and then cyclically tested to simulate seismic loading. A tube anchor system was used to transfer the tensile force carried by the CFRP sheet to the foundation of the specimens. Experimental results showed that the CFRP retrofitting system was able to restore the original strength and initial stiffness of severely damaged specimens and significantly increase the flexural strength, du...

Recent developments on computer bridge analysis and design

Because of the many advances and development in bridge analysis and design, particularly in the area of numerical modelling and computer analysis that have occurred since the advent of the digital computer, previously considered challenging and increasingly more complex highway bridges are now regularly built around the world. These advances oupled with the development of increasingly powerful computers and the fast reducing cost of computing will have significant influence on the future practice of bridge engineering, and also structural engineering in general. This paper presents an overview of some of these developments and the recent trends in bridge modelling and analysis. Language: en

A concentric tube anchor system for fiber-reinforced polymer retrofit of reinforced concrete structural walls under extreme loads

In reinforced concrete elements strengthened with fiber-reinforced polymer sheets, premature debonding of the fiber-reinforced polymer from the concrete substrate occurs due to lack of anchorage, which reduces the efficiency of the retrofitting system. This article reviews several common anchor systems and describes the development, optimization, and testing of a steel tube anchor in retrofit of reinforced concrete structural elements using externally bonded fiber-reinforced polymer sheets suitable for application to improve resistance against extreme load conditions (e.g. blast, impact, or an earthquake). A detailed review of common anchor designs including the proposed tube anchor based on previous studies on flexure-dominated fiber-reinforced polymer-strengthened reinforced concrete shear walls is presented. In this study, finite element analysis is conducted to verify the observed behavior and better understand the deformation mechanisms of the tube anchor. Finite element modeling is then used to evaluate the influence of different design parameters on its performance and propose a design methodology that can be used to optimize the tube anchor design. To verify the performance of the optimized tube anchor, it is tested in an experimental program on the in-plane seismic strengthening of two shear-dominated squat walls strengthened using fiber-reinforced polymer sheets. Experimental results reveal that the optimized tube anchor performs well in preventing premature debonding and allows the fiber-reinforced polymer composite to achieve a higher level of strain when compared to an alternative anchor system. Finally, a set of design steps for the implementation of the tube anchor in fiber-reinforced polymer retrofit applications for reinforced concrete shear walls are presented.

A Comparative Study of System Identification Techniques Under Ambient Vibration

This paper presents the dynamic properties of the Confederation Bridge extracted by four output-only system identification algorithms applied to vibration monitoring data. The purpose of this study is to evaluate the efficiency and accuracy of different modal identification methods, particularly in the presence of high level of uncertainty and noise related to field measurement data. The modal estimates obtained using these alternative approaches are compared and verified against the modal properties from the finite element model.