scholarly journals Vibration Characteristics of Composite Footbridges under Various Human Running Loads

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Faraz Sadeghi ◽  
Ahmad Kueh ◽  
Ali Bagheri Fard ◽  
Nasim Aghili
Keyword(s):  
Vibration Characteristics ◽  
Model Verification ◽  
Structural Performance ◽  
Step Frequency ◽  
Design Standards ◽  
Maximum Acceleration ◽  
Current Design ◽  
Vibration Responses ◽  
Human Running ◽  
Good Agreement

Various types of human running dynamic loads are numerically studied and compared to assess vibration characteristics of the light and slender composite footbridges. Running, which is a common human activity, has been categorized with respect to its intensity into jogging, normal running, and sprinting. To explore the footbridge’s performance, the vibration responses are investigated through a series of analyses in terms of the peak accelerations and displacements. In the model verification, the acquired first natural frequency of structure has shown good agreement with the value reported in the literature. The structural performance of the slender composite footbridge is then evaluated with regard to the serviceability requirement given by the current design standards. It is generally found that the maximum acceleration of the composite footbridge due to the excitation of one person running varies under different running types because of diversities in the velocity and the step frequency. Furthermore, it is shown that the investigated structure provides sufficient human comfort against vibrations for all the examined three types of running loads.

Serviceability Assessment of Composite Footbridge Under Human Walking and Running Loads

2015 ◽  
Vol 74 (4) ◽  
Author(s):  
Faraz Sadeghi ◽  
Ahmad Beng Hong Kueh
Keyword(s):  
Concrete Slab ◽  
Model Verification ◽  
Human Walking ◽  
Steel Beams ◽  
Vibration Source ◽  
Design Standards ◽  
Reinforced Concrete Slab ◽  
Codes Of Practice ◽  
Current Design ◽  
Vibration Responses

Footbridge responses under loads induced by human remain amongst the least explored matters, due to various uncertainties in determining the description of the imposed loadings. To address this gap, serviceability of an existing composite footbridge under human walking and running loadings is analyzed dynamically in this paper employing a finite element approach. The composite footbridge is made-up of a reinforced concrete slab simply supported at two ends on top of two T-section steel beams. To model the walking and running loads, a harmonic force function is applied as the vibration source at the center of the bridge. In the model verification, the computed natural frequency of footbridge exhibits a good agreement with that reported in literature. The vibration responses in terms of peak acceleration and displacement are computed, from which they are then compared with the current design standards for assessment. It is found that the maximum accelerations and displacements of composite footbridge in presence of excitations from one person walking and running satisfy the serviceability limitation recommended by the existing codes of practice. In conclusion, the studied footbridge offers sufficient human safety and comfort against vibration under investigated load prescription.

Experimental Study and Finite Analysis on Flexural Capacity of Laminated Glass

2011 ◽  
Vol 243-249 ◽  
pp. 258-262
Author(s):  
Jun Chen ◽  
Jia Lv ◽  
Qi Lin Zhang ◽  
Zhi Xiong Tao ◽  
Jun Chen
Keyword(s):  
Experimental Results ◽  
Laminated Glass ◽  
Test Results ◽  
Design Code ◽  
Flexural Capacity ◽  
Equivalent Thickness ◽  
High Rise ◽  
Safety Glass ◽  
Current Design ◽  
Good Agreement

Laminated glass has been increasing widely used in high rise buildings as a kind of safety glass in recent years. So we should analyze its material property. In this paper, we use flexural experiments and ANSYS program to analyze the main factors that affect the flexural capacity of the laminated glass. The test results show that the flexural capacity is closely related to film. And the ANSYS program had got good agreement with the experimental results. Comparison of experimental results with calculated ones indicates that the current design code will lead to conservative results and the equivalent thickness of laminated glasses provided in the code should be further discussed.

scholarly journals Calculation features of wall panels with monolithic cement bond of layers in the stages of installation, transportation and maintenance

Vestnik MGSU ◽  
2019 ◽  
pp. 367-375 ◽  
Author(s):  
Elena A. Korol’ ◽  
Marina N. Berlinova
Keyword(s):  
Middle Layer ◽  
Structural Features ◽  
Design Parameters ◽  
Competitive Advantages ◽  
Design Standards ◽  
Wall Panels ◽  
Multilayer Wall ◽  
Current Design ◽  
Infinite Variety ◽  
Construction Practice

Introduction. When building residential, public and administrative buildings of various spatial structural designs (monolithic, precast-monolithic, precast, etc.), it is common practice to design self-sustaining (non-structural) outer walls within a storey. Developing and using new design and fabrication solutions of multilayer industrial-made wall panels in modern construction practice makes actual the issue of improving methods of their calculation in different stages of maintenance and under various sorts and combinations of loads and effects. However, there is an infinite variety of possible loading levels in practice and, therefore, the same variety of design approaches would be required. This is obviously unacceptable for engineering calculations, hence it is necessary to provide a monolithic matrix bond of layers, both technologically and structurally, which can provide a generalized approach to the calculation of multilayer enclosing structures in accordance with current design standards. Materials and methods. The article describes structural features of a multilayer wall panel made of structural concrete with the middle layer of concrete with low thermal conductivity and monolithic bond of layers. These features have an influence on creation of a design model and a calculation procedure in the stages of transportation, installation and maintenance. Results. The article has examined the structures described above in the sense of design parameters that provide their competitive advantages in strength and maintenance as compared with conventional mass-built enclosures. Conclusions. The studies demonstrate that when combining loads of force and non-force character, stresses in the considered structure do not exceed allowable values in all the stages what proves the prospects of using the multilayer panels with monolithic bond of layers for erection of various-purpose frame-panel buildings.

scholarly journals Tests of a Gust-Alleviating Flap in the Gust Tunnel

1940 ◽  
Vol 44 (351) ◽  
pp. 283-294 ◽  
Author(s):  
Philip Donely ◽  
C. C. Shufflebarger
Keyword(s):  
Experimental Results ◽  
Sharp Edge ◽  
Wing Loading ◽  
Longitudinal Stability ◽  
Maximum Acceleration ◽  
Long Period ◽  
Good Agreement ◽  
Made In

SummaryTests were made in the N.A.C.A. gust tunnel to determine the effectiveness of a long-period dynamically overbalanced flap in reducing aeroplane accelerations due to atmospheric gusts. For two gust shapes, one gust velocity, one forward velocity, and one wing loading, a series of flights was made with the flap locked and was then repeated with the flap free to operate. The records obtained were evaluated by routine methods.The results indicate that the flap reduced the maximum acceleration increment 39 per cent, for a severe gust with a representative gust gradient distance of 8 chord lengths and that, for an extreme gust shape (a sharp-edge gust), the reduction was only 3 per cent. The results also indicate that the flap tended to reduce the longitudinal stability of the aeroplane. Computations made of the effectiveness and the action of the flap were in good agreement with the experimental results.

scholarly journals Numerical Analysis of Vibration Responses in High-Speed Railways considering Mud Pumping Defect

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Ting Li ◽  
Qian Su ◽  
Kang Shao ◽  
Jie Liu
Keyword(s):  
High Speed ◽  
Coupled Model ◽  
Test Results ◽  
External Excitation ◽  
Slab Track ◽  
Vibration Responses ◽  
Track Irregularity ◽  
Mud Pumping ◽  
Element Theory ◽  
Good Agreement

As a newly appeared defect under slab tracks in high-speed railways, mud pumping weakens the support ability of the subgrade to slab track, bringing about deviations on the vibration responses of the vehicle, slab track, and subgrade. Therefore, this paper proposes a vehicle-slab track-subgrade coupled model based on the multibody simulation principle and the finite element theory to highlight the influences of mud pumping defect. As an external excitation to this model, random track irregularity is considered. In order to simulate the mud pumping defect, the contact between the concrete base and subgrade is described as a spring-damper system. This model is validated by field test results and other simulation results, and a very good agreement is found. The vibration responses of the vehicle, slab track, and subgrade under different mud pumping lengths and train speeds are studied firstly. The deviations of vibration responses in high-speed railways induced by mud pumping are then obtained, and the limited mud pumping length is put forward finally to provide a recommendation for maintenance works of high-speed railways in practice.

Intersection Design and Decision–Reaction Time for Older Drivers

1997 ◽  
Vol 1573 (1) ◽  
pp. 68-71 ◽  
Author(s):  
David W. Naylor ◽  
Johnny R. Graham
Keyword(s):  
Reaction Time ◽  
Reaction Times ◽  
Older Drivers ◽  
Design Standards ◽  
Older Driver ◽  
The Past ◽  
Sight Distance ◽  
Stop Sign ◽  
Current Design ◽  
Design Value

Trends in automobile and roadway use have changed drastically over the past several years. Changes in the trends include an increase in the percentage of licensed drivers, annual miles driven, and an increase in the number of older drivers. Of particular concern is the increase in the number of older drivers and the question of whether the current design standards adequately meet the needs of the older driver. In this study, the perception-reaction time variable used in calculating intersection sight distance at stop sign-controlled intersections was evaluated. The current design value for the perception–reaction time is 2.0 sec, which has been used since the 1940s when the driving population was much younger. A field experiment was performed to determine an appropriate value for today’s driving population. Subjects were covertly videotaped as they entered two rural and two urban stop sign-controlled interactions. Mean decision–reaction times were determined for an older and a younger group of subjects. The older group, consisting of 104 subjects, averaged 69.3 years of age and had a mean decision–reaction time of 1.32 sec. A group of 104 younger subjects, less than 30 years of age, had a mean decision–reaction time of 1.24 sec. The 85th percentile decision–reaction time for the older group was 1.86 sec and for the younger group, 1.66 sec. Both times were less than the current AASHTO design value of 2.0 sec.

Alleviation of Fatigue in Renewable Energy Support Structures

2011 ◽  
Author(s):  
Feargal Brennan
Keyword(s):  
Renewable Energy ◽  
Offshore Structures ◽  
Support Structures ◽  
Design Standards ◽  
New Era ◽  
The North ◽  
Current Design ◽  
1960S And 1970S ◽  
The 1960S ◽  
Stress Fatigue

Offshore renewable energy is experiencing an explosion of activity in response to ambitious renewable energy targets, however the drive to increase turbine size in deeper water whilst at the same time to reduce capex and installation costs in addition to the speed of development means there is a danger that structures may be designed and deployed that are inherently prone to fatigue. Offshore structures have come a long way since the pioneering early Oil & Gas jackets in the 1960s and 1970s. In forty years of designing and operating large Oil & Gas structures in the North Sea tremendous changes have occurred in development of advanced numerical modelling of stress, fatigue and loading in addition to vast improvements in steel quality/strength, manufacturing processes and inspection, monitoring and quality control. This paper addresses some of the fundamental areas where current design standards may not be appropriate for renewable energy support structures in this new era of advanced sensors and information systems. It will also discuss advanced fatigue alleviation techniques.

Bearing Capacity of Common and Damaged CFRP-Strengthened R. C. Beams Subject to High-Level Low-Cycle Loading

2019 ◽  
Vol 968 ◽  
pp. 185-199
Author(s):  
Vasyl M. Karpiuk ◽  
Yulia A. Syomina ◽  
Diana V. Antonova
Keyword(s):  
Bearing Capacity ◽  
Repeated Loading ◽  
Calculation Methods ◽  
Design Standards ◽  
Deformation Method ◽  
Current Design ◽  
Cycle Loading ◽  
High Level ◽  
Concrete Elements

In the course of operation or armed hostilities the span r.c. structures are subject to substantial damage and considerable reduction of their bearing capacity, especially under low-cycle repeated loading. In this connection it becomes necessary to renew their operation capacity and/or improve their bearing capacity. However, the current design standards contain no recommendations as to determination of the residual bearing capacity of such structures and calculation of their reinforcement. There are methods of the operation capacity renewal and reinforcement of the structures by increasing their sections adding metal or reinforced concrete elements. Still, the calculation methods of such reinforcement are also imperfect. It is proposed to renew operation capacity of such structures by strengthening their tensioned parts with CFRP; the performed experimental research will provide the basis for calculating bearing capacity of said structures with the aid of the deformation method improved by the authors.

Sex Differences in Joint Mobility

1984 ◽  
Vol 28 (11) ◽  
pp. 1006-1006 ◽  
Author(s):  
K. Rene'
Keyword(s):  
Sex Differences ◽  
Study Data ◽  
The Body ◽  
Joint Mobility ◽  
Joint Movement ◽  
Design Standards ◽  
College Female ◽  
Current Design ◽  
Female Data ◽  
Present Design

The primary purpose of this study was to provide a contemporary comparison of college female and male voluntary range of joint mobility. This was achieved by comparing the data collected in this study with that collected in an identical study in which male participants were used. Data were gathered from college females to determine their voluntary range of joint movement. One hundred female students at Texas ASM University participated in the study. The instruments used to take the measures were two hand-held bubble level electrogoniometers. Thirty-two movements of eight different joints of the body were measured. A second goal was to update and broaden the data base of female voluntary flexibility. This goal was met by reporting the data gathered from the female college sample and providing pertinent design information. In addition, the current female data were compared against present design standards. Finally, the present study data and that of the identical male study were combined to allow a comparison with an earlier study of sex differences in joint mobility. Results of this study indicate that females are generally more flexible than males. Significant differences were found to exist in twenty-six of the thiry-two comparisons made between this study and the corresponding male study. In twenty-four of these comparisons, females were found to have greater flexibility. The differences in joint mobility reported were attributed to real differences between the sexes since the methodologies were identical and the samples were drawn from equivalent populations. Comparisons between this study and the current design standards yielded conflicting results due to differences in methodologies and samples. Significant differences were found to exist in the comparisons made between the present data combined with the current male data and an earlier study concerning sex differences in flexibility. These differences were also attributed to differences in methodologies. Both comparisons drew the same conclusion, however: females are generally more flexible than males.

Development of New Zealand seismic bridge standards

2013 ◽  
Vol 46 (4) ◽  
pp. 201-221 ◽  
Author(s):  
L. S. Hogan ◽  
L. M. Wotherspoon ◽  
J. M. Ingham
Keyword(s):  
New Zealand ◽  
Lateral Spreading ◽  
Base Shear ◽  
Design Standards ◽  
Foundation Design ◽  
Ground Shaking ◽  
Lower Base ◽  
Current Design ◽  
Shear Demand ◽  
Structural Detailing

During seismic assessments of bridges where there is a lack of construction documentation, one method of determining likely structural detailing is to use historic design standards. An overview of the New Zealand bridge seismic standards and the agencies that have historically controlled bridge design and construction is presented. Standards are grouped into design era based upon similar design and loading characteristics. Major changes in base shear demand, ductility, foundation design, and linkage systems are discussed for each design era, and loadings and detailing requirements from different eras were compared to current design practices. Bridges constructed using early seismic standards were designed to a significantly lower base shear than is currently used but the majority of these bridges are unlikely to collapse due to their geometry and a preference for monolithic construction. Bridges constructed after the late 1970s are expected to perform well if subjected to ground shaking, but unless bridges were constructed recently their performance when subjected to liquefaction and liquefaction-induced lateral spreading is expected to be poor.

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