Design Of Pedestrian Bridges Research Articles

CUANTIFICACION DE LA PERCEPCION DE LA VIBRACION EN PASARELAS PEATONALES

Modern pedestrian bridges are very often slender and very flexible structures, where the first natural frequencies of vibration may fall close to dominant frequencies of the dynamic excitation due to walking or running. Pedestrian loads are low intensity quasi-periodic loads. Applied to very stiff and massive structures this loads could hardly make them vibrate significantly. Aesthetic, technical and technological developments lead to ever more slender, flexible and low damped footbridges and, as a consequence, they can vibrate significantly even under a single person and frequently require a thorough dynamic analysis. Some codes, standards or guidelines establish acceptable values in terms of acceleration functions. In many of these codes, dynamic problems are addressed by defining limits for the natural frequencies of the structures or for the accelerations associated with pedestrian-induced vibrations. Such approaches are usually conservative and fail to deal with all the parameters relevant to human sensitivity to vibrations, which is highly subjective. This, together with the fact that the natural frequencies and accelerations calculated by analytical or numerical methods are subject to uncertainties, may hinder pedestrian bridge design. In general, the perception and the individual judgement, whether vibrations are disturbing or not, are based on psychological parameters and can lead to different limits, as certain persons can detect vibrations without being discomforted by them. Some of these parameters are difficult to quantify or are highly subjective. They include the number of simultaneous users, frequency of use, pedestrians’ activity (walking, jogging, standing or sitting on the bridge), flexibility of the pavement, time of exposure, deck and guard rail transparency, height over ground level, footbridge appearance, if vibration is expected or not, etc. In this work the vibration perception is addressed and certain applied approaches are presented.

Aesthetics and Economy in Pedestrian Bridge Design

Two common pitfalls of pedestrian bridge design are explored: the idea that a structure that is efficient will automatically be elegant versus the notion that a lot of money must be spent to get a beautiful structure. The drive for landmark bridges has led some engineers to disregard the engineering ethic of economy with some recent footbridges. The Töss Footbridge by structural artist Robert Maillart is shown as a model structure, with Maillart's calculations and a description of the bridge's structural behavior presented. Then an extremity on the other side of the spectrum is analyzed: the Turtle Bay Sundial Bridge in Redding, California. The cost escalation and a scientific explanation of the irrationality of the bridge form are presented for this $23.5 million footbridge. In order to explore both pitfalls in the United States an informal national study of all 50 states was performed. Results from the national study (including costs) are described and interpreted. Three unique structures from this study are presented which are reasonably economical and prove that a so-called signature bridge does not require extreme cost.

First ISIS Canada pedestrian bridge: student design perspective

In January 2002, the Intelligent Sensing for Innovative Structures (ISIS) Canada Networks of Centres of Excellence announced its first pedestrian bridge design competition for ISIS students. The bridge is located on the campus of the Université de Sherbrooke to provide a new access to the new east entrance of the Faculty of Engineering Building. The proposed design was required to convey the innovation and ingenuity of the ISIS Canada Research Network through the use of fibre-reinforced-polymer (FRP) materials. Based on these requirements, five graduate students from the Department of Civil Engineering at Queen's University joined forces to produce the winning conceptual design, demonstrating cost-effectiveness, visual stimulation, and innovation. This application paper presents details of the competition and the winning design for the pedestrian bridge as told by the winning design team. The bridge was built during the summer of 2002 at the Université de Sherbrooke. The objective of the paper is to present the student experience from this highly successful competition, and thus to promote similar design competitions for engineering students.Key words: short span, pedestrian bridge, fibre-reinforced polymers, reinforced concrete, conceptual design, innovation, ingenuity.

Dynamic response of pedestrian bridges for random crowd-loading

The publicity regarding the 18-month closure of London’s Millennium Bridge due to excessive lateral vibration response under crowd loading during its opening ceremony has highlighted the necessity for further investigation into the sources of this problem. Current design guidelines focus on single pedestrian dynamic loading and subsequently underestimate the dynamic response associated with crowd loading in the design of pedestrian bridges. This deficiency is addressed in this paper with the mathematical incorporation of random crowd effects into the dynamic analysis procedure. The introduction of a crowd factor (Cf) allows the individual response to be extended to incorporate multiple pedestrians with random arrival times. A subsequent statistical analysis into the mean, variance and distribution shape of Cf allowed the mathematical derivation of an equation stipulating its maximum upper value for a deemed appropriate level of confidence.

Identification of a human walking force model based on dynamic monitoring data from pedestrian bridges

A general investigation procedure for the vibration serviceability of pedestrian bridges is accomplished by comparing the dynamic response of structures to vibration effects on serviceability limiting states. The purposes of this study were to investigate the dynamic response characteristics of pedestrian bridges and to develop a human walking force model to assist in the development and design of pedestrian bridges. Human walking force parameters were identified by a genetic algorithm (GA) from experimental forced vibration data. The results of the dynamic response obtained by the GA were in agreement with the experimental results. Therefore, the GA system was useful in the identification of pedestrian walking forces, and from the experimental and calculated results, it is considered that the walking force model identified by the GA is substantially accurate.

Aesthetic Considerations for Urban Pedestrian Bridge Design

Many urban pedestrian bridges have been built in the world. However, their aesthetic aspect has often been neglected. As the loadings of an urban pedestrian bridge is comparatively small and its width is relatively narrow, the modeling of the bridge is more flexible than other types of bridges. In this paper, the factors affecting the formation of urban pedestrian bridges are analyzed. These factors include the surroundings, positions of viewers, and types of bridge structures. Additionally, some basic considerations and regulations concerning the aesthetic shaping of urban pedestrian bridges and plane and space compositions are developed. These regulations can help engineers better understand the aesthetic aspect of urban pedestrian bridge design. Finally, the aesthetic analysis of several existing bridges based on the presented regulations is given.