Pedestrian Loading Research Articles

Vibration control study of a suspension footbridge using hybrid slotted bolted connection elements

A hybrid finite element of a slotted bolted connection element (SBCE) is developed which constitutes a frictional damper and two truss elements. The damping mechanism of the damper is based on the micro-slip elements in the contact surface, and the damping properties can be designed for any specific requirements by adjusting several design parameters which in turn, depends on the physical parameters of the joint. Simulation studies are reported on the vibration mitigation of a suspension footbridge due to pedestrian loading with twenty-eight SBCEs. The dynamic load model reported in the London Millennium Footbridge [Struct. Eng. 79 (2001) 17] is adopted. Recommendations on the design of parameters of the dampers are given. The damping by energy dissipation in the structure is discussed with reference to the time response history of the structure and the hysteretic loops of the dampers.

Application of non‐linear multiple tuned mass dampers to suppress man‐induced vibrations of a pedestrian bridge

AbstractThis paper presents an application of multiple tuned mass dampers (MTMDs) with non‐linear damping devices to suppress man‐induced vibrations of a 34m long pedestrian bridge. The damping force generated by each of these damping devices is simply a drag force from liquid acting on an immersed section. The quadratic non‐linear property of these devices was directly determined from free vibration tests of a simple laboratory set‐up. Dynamic models of the bridge and pedestrian loads were constructed for numerical investigation based on field measurement data. The control effectiveness of non‐linear MTMDs was examined along with its sensitivity against estimation errors in the bridge's natural frequency and magnitude of pedestrian load. The numerical results indicated that the optimum non‐linear MTMD system was as effective and robust as its linear counterpart. Then, a six‐unit non‐linear MTMD system was designed, constructed, and installed on the bridge. Field measurements after the installation confirmed the effectiveness of non‐linear MTMDs, and the measurement results were in good agreement with numerical predictions. After the installation, the average damping ratio of the bridge was raised from 0.005 to 0.036 and the maximum bridge accelerations measured during walking tests were reduced from about 0.80–1.30 ms−2 to 0.27–0.40 ms−2, which were within an acceptable range. Copyright © 2003 John Wiley & Sons, Ltd.

空間-時間系モデルを用いた歩行者空間の混雑評価

The purpose of this study is to evaluate the pedestrian space with time series interfering area model. The model illustrates the interference of pedestrian's area in the several directions. And the coordinates of pedestrians are sensed and used for evaluation of the space. Pedestrian movement was recorded by the VCR camera and coded individual frames at sampling intervals of 0.5 seconds. The records were projected and corrected for foreshortened perspective. Then the coordinates of pedestrians in each frame were calculated. The pedestrian area is defined as the circle 0.9 meters in diameter in which pedestrian can avoid and pass others. When someone approaches another in pedestrian area, the conflict between two pedestrians occurs. The term "interfering load" can be defined as a load which pedestrians take in such a situation. There are two types of interfering load. One is a load between pedestrians in the same direction and the other is a load between pedestrians in the opposite direction. We only concerned with the Interfering load between bidirectional pedestrians, because monodirectional pedestrians reduce their walking load by forming groups in the same direction. The "time series interfering area model" describes the load between pedestrians in the several directions. This model's advantage is as follows; (1) The characteristics of pedestrian loads in a time series are grasped and comprehended with it. (2) As the congestion in the observation area in a time series is observed, and the area is evaluated particularly. (3) The situations of intersecting pedestrians in the several directions are grasped.

Evaluation of design requirements for footbridges excited by vertical forces from walking

The continuing trend towards the design of more slender, lighter, and livelier footbridges has created new challenges that are not properly addressed in a number of widely used codes of practice in Europe and Canada. Recent research into vibration serviceability of slender structures under human-induced dynamic loading suggests that improvements to the existing footbridge design guidelines are possible in the area of modelling human-induced excitation in the vertical direction. This paper evaluates the performance of currently used codes of practice regarding vibration serviceability of footbridges under human-induced loads due to walking. The evaluation is supported by experimental evidence from tests carried out by the authors on potentially lively footbridges. A description of recent research advances is included, together with a comparative analysis of the approaches of some pertinent guidelines used internationally to tackle this design problem. In addition, suggestions are made for re-addressing the problem of vibration serviceability of footbridges by focusing attention on a more realistic definition of vertical pedestrian loading and the corresponding frequency ranges of interest. It was found that the codes are either conservative or lack appropriate safety margins, depending on the frequency range excited by moving pedestrians. This is principally due to the lack of proper consideration for the frequency content of the pedestrian load, which would take into account developments since the 1970s when the scientific data used in the majority of the current codes of practice were produced.Key words: vibration, serviceability, walking, footbridges, design, codes, dynamic loading factor, evaluation.

Bridge loads – An international perspective

This book provides a detailed summary of bridge loads from an international perspective. The authors cover all aspects from the methodology behind the calculation of bridge loads and the complex interactions between loads and bridges, to economic considerations. A wide range of bridge loads are covered, including highway vehicle loads, pedestrian loads, railing loads and wind loads. The structure and design of bridges to accommodate these loads are examined and examples provided. Different modes of failure and current codes of practice are also covered. (A)

Avifaunal Use of Wooded Streets in an Urban Landscape

Abstract: Birds in urban landscapes primarily occupy parks ( forest fragments), wooded streets ( linear strips connecting fragments), or the urban matrix. I studied the effects of street location in the landscape, vegetation structure, and human disturbance ( pedestrian and automobile load) within wooded streets on bird species richness, temporal persistence, and density of feeding and nesting guilds, and on the probability of street occupation by individual species in Madrid during two consecutive breeding seasons. The number of species recorded increased from the least suitable (control streets without vegetation) to the most suitable habitats (urban parks), with wooded streets being intermediate landscape elements. Fourteen species, belonging to four of the eight guilds identified in this system, were recorded in wooded streets in both years. Streets that connected urban parks, along with vegetation structure, positively influenced the number of species within wooded streets, species persistence, guild density, and probability of occupation of streets by individual species. Human disturbance exerted a negative influence on the same variables. Wooded streets potentially could function as corridors, allowing certain species—particularly those feeding on the ground and breeding in trees or tree holes—to fare well by supporting alternative habitat for feeding and nesting. Local improvements in corridor quality, through increased vegetation complexity and reduced human disturbance, could exert a positive influence on the regional connectivity of the system. Because of differential use of corridors by species with different habitat requirements, however, corridor implementation should also take into account the target species of management.

A202歩行者領域モデルを用いた群集流動効率の可視化

The purpose of this study is to evaluate the pedestrian space with time series interfering area model. The model illustrates the interference of pedestrian's area in the several directions. And the coordinates of pedestrians are sensed and used for evaluation of the space. The “time series interfering area model” describes the load between pedestrians in the several directions. This model's advantage is as follows; (1) The characteristics of pedestrian loads in a time series are grasped and comprehended with it. (2) As the congestion in the observation area in a time series is observed, and the area is evaluated particularly. (3) The situations of intersecting pedestrians in the several directions are grasped.

The Clear Creek Hybrid Composite I-Girder Pedestrian Bridge

An 18.3 m (60 ft) pedestrian I-girder bridge was analyzed, designed, tested, and constructed. The main load-carrying members for the bridge are two 61-cm (24-in.) deep composite fiberglass I-girders with embedded carbon fibers in the flanges. Laboratory testing quantified the increased stiffness of the hybrid glass/carbon fiber-reinforced polymer beams over those manufactured solely with glass fibers. Typical joint connections were tested to investigate their performance, and a dynamic analysis was performed to check the bridge's vibration under pedestrian load.

VIBRATION CHARACTERISTICS OF A SUSPENSION FOOTBRIDGE

A suspension footbridge located in a tourist attraction in Singapore has a suspended span of 35 m and was designed for static pedestrian and wind loads. In common with other bridges of this type, it is a light, efficient structure and has a lively dynamic performance.Distributed parameter and finite element models were used to understand the vertical plane behaviour of the bridge and a prototype dynamic test using impact excitation was conducted to check the models and investigate the dynamic response.The first two vertical vibration modes were found to occur at the same frequency, 2 Hz, as the average pedestrian footfall. Response to pedestrians was simulated using linear and non-linear models of a moving excitation source.

Vibration of Pedestrian Overpass

The levels of vibration induced by pedestrian traffic on a pedestrian overpass with a 43.3‐m (142‐ft) main span are found to be perceptible to its users. The maximum root‐mean‐square (RMS) acceleration measured in the field exceeds the acceptable level of vibration recommended by the American National Standards Institute (ANSI). Three structural modification schemes, proposed to alleviate the vibration serviceability problem, are analyzed and compared. The comparison is based on the acceleration response to pedestrian loading represented by a pulsating load traveling across the bridge span. It is found that adding viscoelastic structural dampers is the more efficient and preferable scheme of modification for reducing the pedestrian‐induced vibrations.