Seismic design of bridge structures with allowance for large relative girder movements to avoid pounding

2009 ◽  
Vol 42 (2) ◽  
pp. 75-85 ◽  
Author(s):  
Nawawi Chouw ◽  
Hong Hao
Keyword(s):  
Ground Motion ◽  
Soil Structure ◽  
Influence Factors ◽  
Bridge Girders ◽  
Gap Size ◽  
Expansion Joint ◽  
Vibration Properties ◽  
Bridge Structures ◽  
Almost All ◽  
Bridge Spans

Pounding between bridge girders have been observed in almost all previous major earthquakes. This is because the gap size of conventional bridge expansion joint is usually only a few centimetres, which is not sufficient to preclude poundings owing to large relative displacements between bridge girders caused by the effect of varying vibration properties of adjacent bridge spans, varying ground motions at bridge supports and varying soil-structure interaction (SSI). In this work a new design of bridge expansion joint is introduced. Instead of tolerating pounding and providing possible mitigating measures, this new design approach enables large movement between bridge girders which makes a complete pounding preclusion possible. The new expansion joint is called Modular Expansion Joint (MEJ). The large movability is achieved by installing a number of small gaps in the joint. In this study, the MEJ gap size required to completely avoid girder pounding is investigated. The most significant influence factors – the varying vibration properties of adjacent bridge spans, the effect of SSI and ground motion spatial variation on expansion joint size required to preclude pounding- are calculated. Discussions on the relative importance of various structural and ground motion properties in generating relative displacements of adjacent bridge girders are made.

scholarly journals Regulation of dynamic characteristics of bridge spans in the conditions of the changing impact of the temporary moving load

2021 ◽  
Vol 1 ◽  
pp. 4-19
Author(s):  
Vladimir Mikhailovich Kartopoltsev ◽  
◽  
Andrey Vladimirovich Kartopoltsev ◽  
Keyword(s):  
Dynamic Characteristics ◽  
Moving Load ◽  
Musical Instrument ◽  
Oscillatory Process ◽  
Natural Oscillations ◽  
Structural Content ◽  
Bridge Structures ◽  
National Programs ◽  
And Control ◽  
Bridge Spans

It is known that an unregulated structure is likened to an unadjusted musical instrument [7]. The adjusted dynamic stress-strain state of the bridge spans will be adequate to the parameters of the design and operational state as a result of the introduction of regulation and control of fl uctuations in the conditions of the changing impact of the temporary mobile load. Methods for regulating dynamic characteristics by changing the frequency of natural oscillations of the system, taking into account energy dissipation, as well as introducing into the oscillatory process a transformed form of intense oscillations in the process of artifi cial or selective resonance, in which the oscillations of the system either damp or cease to be dangerous, are especially carefully considered. Attention is focused on the infl uence of the defectiveness of the roadway with an increase in the mass and speed of a temporary moving load. For this purpose, a classifi er of bridge deck defects has been developed to clarify the boundaries of the eff ect of a defect on the dynamic operation of a structure [1, 3]. Analysis of the structural content and criteria for determining shows the insuffi ciency of the components assessing the eff ect of the temporary mobile load on the span under non-stationary oscillations, and also reveals contradictions in the assessment of the dynamic additive . The practical use of the research results is advisable by the Ministry of Transport Construction in the implementation of state national programs and projects for improving structures, calculation methods, design and operation of bridge structures

The effect of soil-structure interaction on seismometer readings

1978 ◽  
Vol 68 (3) ◽  
pp. 823-843
Author(s):  
G. N. Bycroft
Keyword(s):  
Ground Motion ◽  
Soil Structure ◽  
Free Field ◽  
Soil Structure Interaction ◽  
Rigid Sphere ◽  
Elastic Space ◽  
Structure Interaction ◽  
Frequency Components ◽  
Low Shear

abstract Rocking and vertical and horizontal translations of typical “free-field” seismometer installations lead to magnification of the ground motion record. This magnification can be significant for the higher frequency components if the terrain has a relatively low shear-wave velocity. Seismometers placed on foundations which cover a significant part of a wavelength of a horizontally incident wave, experience an attenuated ground motion. A method of correcting the seismograms for these effects is given. Compliance functions for a rigid sphere in a full elastic space are derived and are used to show that, in practical cases, down-hole seismometer installations are not significantly affected by interaction. These compliance functions should be useful in discussing the soil structure interaction of structures erected on bulbous piles. They may be also used as the basis of a method of determining elastic constants of ground at depth, in situ, and at different frequencies.

scholarly journals Influence of the Acoustic Cover of the Modular Expansion Joint on the Acoustic Climate in the Bridge Structure Surroundings

Materials ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 2842
Author(s):  
Janusz Bohatkiewicz ◽  
Michał Jukowski ◽  
Maciej Hałucha ◽  
Marcin Dębiński
Keyword(s):  
Sound Level ◽  
Structural Elements ◽  
Expansion Joint ◽  
Expansion Joints ◽  
The Road ◽  
Sound Levels ◽  
Road Surfaces ◽  
Before And After ◽  
Bridge Structures

The noise generated at the interface between the wheels of vehicles and the road surface is well recognized in the literature worldwide. Many publications describe the phenomenon of reducing this kind of impact by silent road surfaces. A specific type of this noise is the sound generated by vehicles passing over the expansion joints of bridge structures. Due to the impulsive nature of this sound, it is very onerous for people living in the close vicinity of bridge structures. The passage of vehicles over expansion joints causes the formation of vibrations that are transmitted to the structural elements of bridge structures, which may cause the formation of the material sounds (especially arduous in the case of bridges with steel elements). An attempt to reduce this impact was made by making a prototype acoustic cover of the expansion joint on the selected bridge. The paper presents the results of research on the “in situ” acoustic effectiveness of this cover. Additionally, the noise was modelled in the object surroundings before and after the cover’s application. The acoustic efficiency of the cover in the whole measured frequency range was 5.3 dBA. In the narrower frequency bands (1/3 octave bands), larger sound level reductions were observed. The maximum sound levels measured under the tested dilatation were less than 10.0 dBA lower than the maximum sound levels measured under the reference dilatation.

scholarly journals Engineering better chimeric antigen receptor T cells

2020 ◽  
Vol 9 (1) ◽  
Author(s):  
Hao Zhang ◽  
Pu Zhao ◽  
He Huang
Keyword(s):  
T Cells ◽  
Intracellular Signaling ◽  
Influence Factors ◽  
Target Antigen ◽  
Car T Cells ◽  
Car T ◽  
Underlying Mechanisms ◽  
Almost All

AbstractCD19-targeted CAR T cells therapy has shown remarkable efficacy in treatment of B cell malignancies. However, relapse of primary disease remains a major obstacle after CAR T cells therapy, and the majority of relapses present a tumor phenotype with retention of target antigen (antigen-positive relapse), which highly correlate with poor CAR T cells persistence. Therefore, study on factors and mechanisms that limit the in vivo persistence of CAR T cells is crucial for developing strategies to overcome these limitations. In this review, we summarize the rapidly developing knowledge regarding the factors that influence CAR T cells in vivo persistence and the underlying mechanisms. The factors involve the CAR constructs (extracellular structures, transmembrane and intracellular signaling domains, as well as the accessory structures), activation signaling (CAR signaling and TCR engagement), methods for in vitro culture (T cells collection, purification, activation, gene transduction and cells expansion), epigenetic regulations, tumor environment, CD4/CD8 subsets, CAR T cells differentiation and exhaustion. Of note, among these influence factors, CAR T cells differentiation and exhaustion are identified as the central part due to the fact that almost all factors eventually alter the state of cells differentiation and exhaustion. Moreover, we review the potential coping strategies aiming at these limitations throughout this study.

Detection and Identification of Bridges Considering Soil Effect

2004 ◽  
Author(s):  
Jun-Ping Pu ◽  
Yao-Min Fang ◽  
Hung-Ren Chen ◽  
Jian-Fa Huang
Keyword(s):  
Soil Structure ◽  
Structural Condition ◽  
Analytical Models ◽  
Dynamic Monitoring ◽  
Structural Monitoring ◽  
Structure Model ◽  
Bridge Inspection ◽  
Inspection Method ◽  
Detection And Identification ◽  
Bridge Structures

Unexpected collapses and near collapse of bridges during the 1999 Chi-Chi earthquake underline the need for effective structural monitoring. Periodic structural condition monitoring of bridge structures is necessary to ensure that they provide a continued and safe service. A systematic study of typical bridges is needed, focusing on identifying elastic analytical models that will incorporate the existing state of bridge. To establish dynamic monitoring as a routine bridge inspection method, the soil-structure model of these two bridges are established and compared theoretically and experimentally.

Research on the Energy Saving Performance of the Enthalpy Recovery Ventilator in Chinese Residential Buildings

Solar Energy ◽  
2006 ◽  
Author(s):  
Junjie Liu ◽  
Bin Wang ◽  
Youhao Xu
Keyword(s):  
Energy Saving ◽  
Residential Buildings ◽  
Influence Factors ◽  
Coefficient Of Performance ◽  
Weather Data ◽  
Outdoor Air ◽  
Enthalpy Recovery ◽  
Save Energy ◽  
Definition Of ◽  
Almost All

In order to fulfill the indoor comfort and health requirements, people need to supply a large amount of outdoor fresh air into the indoor environment. In the past, because of the poor airtight performance of the residential buildings in China, there is usually no mechanical ventilator installed, almost all of the outdoor air infiltrates from the leaks through the windows and doors. Recently, in order to improve the energy saving performance, the windows and doors of the residential buildings become more and more airtight so that the outdoor air can’t infiltrate into the rooms easily, but it results in the worse and worse indoor air quality. People need supply enough outdoor fresh air into the rooms without increasing the energy consumption greatly. The installation of the enthalpy recovery ventilator (ERV) is an effective method. It can transfer heat and moisture from the exhaust air into the outdoor fresh air to save energy. Nowadays, ERV has been widely used in the commercial and industry buildings, and started in the residential buildings in China. But ERV is not always energy saving in anywhere and anytime. Its energy saving performance depends on a lot of factors, such as the outdoor environmental condition, the enthalpy effectiveness of the enthalpy recovery medium, the Coefficient of Performance (COP) of the air condition system and so on. Based on the weather data, this paper calculates the hourly energy saving performance of ERV for residential buildings that are hypothetically located in five Chinese representative cities of five different climate zones in summer. It gives the definition of the cooling ventilation season and studies the influence factors related to the energy saving performance of ERV.

SEPTEMBER 26, 2019 Mw5.8 MARMARA SEA-SILIVRI (ISTANBUL) EARTHQUAKE: ANALYSIS OF GROUND MOTION RECORDS

2020 ◽  
Author(s):  
Seyhan Okuyan Akcan ◽  
Can Zulfikar
Keyword(s):  
Ground Motion ◽  
North Anatolian Fault ◽  
Marmara Region ◽  
Marmara Sea ◽  
The North ◽  
Tectonically Active ◽  
Earthquake Research ◽  
Earthquake Research Institute ◽  
Ground Motion Records ◽  
Almost All

<p>Marmara region located on the western end of the North Anatolian Fault Zone is a tectonically active region in Turkey. There have been frequent severe earthquakes in the region and will continue to occur. There was no serious earthquake in the region after the 1999 Mw7.4 Kocaeli and Mw7.2 Düzce earthquakes. A Marmara Sea offshore earthquake Mw5.8 close to Silivri Town of Istanbul Metropolitan City has occurred on September 26, 2019 daytime at 13:59. The earthquake happened at the coordinate of 40.87N – 28.19E with a depth of 7.0km on the Kumburgaz segment of the North Anatolian Fault line. It was felt in almost all Marmara region. In some settlements in Istanbul City, slight to moderate damages were observed. A foreshock earthquake of Mw4.8 occurred on the same segment on 24 September, 2019. 150 aftershock events ranging from M1.0 to M4.1 have been recorded within the 24 hours after the mainshock. The ground motions have been recorded in the region by the several institutions including AFAD (Disaster and Emergency Management Presidency), KOERI (Kandilli Observatory and Earthquake Research Institute) and IGDAS (Istanbul Gas Distribution Industry and Trade Inc.). The ground motion records and selected parameters have been examined in this study. The ground motion parameters (MMI, PGA, PGV, Sa, Sv, Sd) distribution have been achieved and checked by the recent NGA-West2 ground motion prediction equations (GMPEs); ASK2014, CY2014 and BSSA2014. The compatibility of the GMPEs for a moderate size Marmara Sea earthquake has been examined.</p>

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