The Detection Research of Tension about Vertical Prestressed Fine Rolled Twisted Bar in Box-Girders Construction of Civil Engineering

2012 ◽  
Vol 568 ◽  
pp. 134-137
Author(s):  
Xing Yuan Lin ◽  
Yan Feng Wu ◽  
Wei Wei Wang ◽  
Feng Zhang
Keyword(s):  
Prestressed Concrete ◽  
Civil Engineering ◽  
Tensile Force ◽  
Construction Process ◽  
Box Girders ◽  
Box Girder ◽  
Box Beam ◽  
Rigid Frame ◽  
Relationship Of ◽  
The Relationship

At present, vertical prestress detection is almost blank during box-girders construction of civil engineering . In order to effectively detect the effective tension at box-girder construction process in civil engineering based on the theory of structural dynamics, scene detection means, the relationship of box-girder vertical prestressing tensile force and dynamic characteristics of the exsertion segment reinforced was established. Vertical prestress of part of the box beam segments of a three-span prestressed concrete continuous rigid frame was detected , the shortcomings of the current vertical prestressing tensile force was analyzed . The results show that: the proposed method is direct, effective and able to effectively monitor the vertical prestressing tensile force. The research has important theoretical and engineering applications for crack prevention of box-girders.

scholarly journals Effect of Construction Method on Shear Lag in Prestressed Concrete Box Girders

2012 ◽  
Vol 2012 ◽  
pp. 1-17 ◽  
Author(s):  
Shi-Jun Zhou
Keyword(s):  
Cross Sections ◽  
Prestressed Concrete ◽  
Construction Process ◽  
Shear Lag ◽  
Box Girders ◽  
Box Girder ◽  
Construction Methods ◽  
Concrete Box Girder ◽  
Concrete Box Girder Bridges ◽  
Girder Bridge

Most of the previous researches conducted on shear lag of box girders were only concerned about simple types of structures, such as simply supported and cantilever beams. The structural systems concerned in these previous researches were considered as determined and unchangeable. In this paper, a finite element method considering shear lag and creep of concrete was presented to analyze the effect of dynamic construction process on shear lag in different types of concrete box-girder bridges. The shear lag effect of the three types of a two-span continuous concrete beam classified by construction methods was analyzed in detail according to construction process. Also, a three-span prestressed concrete box-girder bridge was analyzed according to the actual construction process. The shear lag coefficients and stresses on cross sections along the beam including shear lag were obtained. The different construction methods, the changes of structural system with the construction process, the changes of loading and boundary conditions with the construction process and time, the prestressing, and creep were all imitated in the calculations. From comparisons between the results for beams using different construction methods, useful conclusions were made.

scholarly journals Influence of end Contsrains on the Global Behaviour of a Box Girder

2016 ◽  
Vol 6 (1) ◽  
pp. 7-15
Author(s):  
Daniela Mihaela Boca ◽  
A. Faur ◽  
A. Boca
Keyword(s):  
Prestressed Concrete ◽  
Transport Infrastructure ◽  
Box Girders ◽  
3D Fem ◽  
Important Data ◽  
Box Girder ◽  
Fem Model ◽  
Global Behaviour ◽  
Applied Forces ◽  
Precast Prestressed Concrete

Abstract This study aims to presents the importance of end constrains, boundary conditions and position of the applied forces regarding the design of precast/prestressed concrete box girders. The study is based on a destructive test which was performed on a 37.1 m span single-cell prestressed concrete box girder. The scope of the test was to certify the usage of such girders for the new Transylvania motorway bridges. The test is numerically reproduced through a full 3D FEM model implemented in SAP2000. The influence of the end diaphragms is considered by analysing the beam’s behaviour to six loading conditions: one of which is replicating the loadings during the test, while the others are conceived as real vertical and horizontally loading scenarios. The results obtained for the girders with and without end constrains are compared. The performances of both design solutions in the presence of prestressing are highlighted where applicable. It is considered that the results of this study may provide very important data if considering that Romania has an urgent need to realize a modern and an adequate transport infrastructure.

Optimization on Closure Scheme of Multi-Span Prestressed Concrete Box-Girder Bridge

2010 ◽  
Vol 163-167 ◽  
pp. 2369-2375 ◽  
Author(s):  
Ming Yuan ◽  
Dong Huang Yan
Keyword(s):  
Stress State ◽  
Prestressed Concrete ◽  
Box Girder ◽  
Rigid Frame ◽  
Closure Scheme ◽  
Concrete Box Girder ◽  
Box Girder Bridge ◽  
Girder Bridge ◽  
Cantilever Construction ◽  
Rigid Frame Bridge

The stress state of finished bridge and service stage is influenced by various closure schemes in cantilever construction of multi-span prestressed concrete box-girder bridge. Two typical bridges—multi-span prestressed concrete continuous rigid frame bridge and girder bridge are investigated, The stress state in different closure schemes are analyzed using finite element(FE) analysis. Meanwhile, compared the healthy monitoring data, it has been found that taking the closure sequence from side span to middle span in cantilever construction of multi-span prestressed concrete box-girder bridge can lower stress of girder and pier in finished bridge stage, as well as reducing deformation of girder in service stage. Hence, the closure sequence from side span to middle span is more suitable for cantilever construction of multi-span prestressed concrete box-girder bridge.

scholarly journals Computation of Deflections for PC Box Girder Bridges with Corrugated Steel Webs considering the Effects of Shear Lag and Shear Deformation

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Wei Ji ◽  
Kui Luo ◽  
Jingwei Zhang
Keyword(s):  
Shear Deformation ◽  
Prestressed Concrete ◽  
Displacement Function ◽  
Shear Lag ◽  
Longitudinal Displacement ◽  
Box Girders ◽  
Element Analysis ◽  
Box Girder ◽  
Bridge Model ◽  
Bridge Models

Prestressed concrete (PC) girders with corrugated steel webs (CSWs) have received considerable attention in the past two decades due to their light self-weight and high prestressing efficiency. Most previous studies were focused on the static behavior of CSWs and simple beams with CSWs. The calculation of deflection is an important part in the static analysis of structures. However, very few studies have been conducted to investigate the deflection of full PC girders or bridges with CSWs and no simple formulas are available for estimating their deflection under static loads. In addition, experimental work on full-scale bridges or scale bridge models with CSWs is very limited. In this paper, a formula for calculating the deflection of PC box girders with CSWs is derived. The longitudinal displacement function of PC box girders with CSWs, which can consider the shear lag effect and shear deformation of CSWs, is first derived. Based on the longitudinal displacement function, the formula for predicting the deflection of PC box girders with CSWs is derived using the variational principle method. The accuracy of the derived formula is verified against experimental results from a scaled bridge model and the finite element analysis results. Parametric studies are also performed, and the influences of shear lag and shear deformation on the deflection of the box girder with CSWs are investigated by considering different width-to-span ratios and different girder heights. The present study provides an effective and efficient tool for determining the deflection of PC box girders with CSWs.

Electromechanical analysis of length-related resistance and contact resistance of conductive knitted fabrics

2012 ◽  
Vol 82 (20) ◽  
pp. 2062-2070 ◽  
Author(s):  
Li Li ◽  
Song Liu ◽  
Feng Ding ◽  
Tao Hua ◽  
Wai Man Au ◽  
...  
Keyword(s):  
Contact Resistance ◽  
Electrical Resistance ◽  
Tensile Force ◽  
Standard Errors ◽  
Knitted Fabrics ◽  
High Coefficient ◽  
Proposed Model ◽  
Conductive Yarns ◽  
Relationship Of ◽  
The Relationship

Conductive fabrics usually exhibit two types of electrical resistance: the length-related resistance and contact resistance. The length-related resistance increases with the applied extensile force, whereas the contact resistance decreases with the contact force. The resistance of conductive knitted fabrics could be modeled by the superposition of the length-related resistance and contact resistance. Three experiments were conducted to investigate the resistance of conductive yarns: two overlapped conduct yarns and conductive knitting stitches under unidirectional extensile forces, respectively; and the corresponding empirical equations were developed. The relationship of the resistance, tensile force, fabric length and width were established. The fitting curves with high coefficient of determinations (>0.94) and low standard errors (<0.18) given by the modeling equations were achieved. Therefore, the proposed model could be used to compute the resistance of the conductive knitting fabrics under unidirectional extension.

scholarly journals Development of the mechanism of motivation and tangible incentivisation

2018 ◽  
Vol 170 ◽  
pp. 01094
Author(s):  
Ludmila Lavrova ◽  
Nikolay Chernegov ◽  
Maria Ivanova ◽  
Zhanna Lemesheva ◽  
Elena Akimova
Keyword(s):  
Construction Industry ◽  
Performance Indicators ◽  
Key Performance Indicators ◽  
Construction Process ◽  
Construction Enterprises ◽  
Strategic Objective ◽  
Motivational Mechanism ◽  
Relationship Of ◽  
The Relationship

The main objective of the study is the development of an effective motivational mechanism for employees of construction enterprises. The paper considers particularities of remuneration of participants of construction process in order to define the application of various mechanisms of motivation and incentivisation. The existing methods of development of motivation and incentivisation are analyzed as a tool for increasing the performance of the enterprise. Scientific and methodological recommendations on the establishment and implementation of the mechanisms of motivation and incentivisation as a tool for increasing the performance of enterprises in the construction industry were developed. These recommendations allow identifying the relationship of motivation and incentivisation with the performance of the enterprise. The developed mechanism is based on the relationship between the strategic objective of the enterprise and the key performance indicators of the units or specific employees.

Monitoring of External Prestressing Tendons Construction Process of Jiamusi Highway Prestressed Concrete Bridge during Strengthening in China

2010 ◽  
Vol 163-167 ◽  
pp. 2873-2879
Author(s):  
Ali Fadhil Naser ◽  
Zong Lin Wang
Keyword(s):  
Prestressed Concrete ◽  
Concrete Bridge ◽  
Construction Process ◽  
Box Girder ◽  
External Prestressing ◽  
Maximum Value ◽  
External Tendons ◽  
Monitoring Process ◽  
Left And Right ◽  
Prestressed Concrete Bridge

Jiamusi highway prestressed concrete bridge is located in the Jiamusi City within Heilongjiang province in the east north of China. The strengthening and repairing of the bridge structure can be provided an effective and economic solution in appropriate situation. The objective of this study are to monitor the construction process of external prestressing tendons for strengthening of Jiamusi highway prestressed concrete bridge. Monitoring process includes measurement of external prestressing tendons natural frequency, monitoring of tensile forces values of external prestressing tendons, monitoring of development of anchor beams cracks, and monitoring of anchor beam deformation. The results of monitoring process show that the box girder No. 11 has the largest values of proportional coefficient (K) and the maximum value is 327.8. Box girder No. 8 has the largest values of frequency, the maximum value is 3.499. Five levels of tension are used in the application of tensile force in the tension process of external prestressing tendons. These levels are level 1=248.2kN, level 2=496.4kN, level 3=744.6kN, level 4=992.8kN, and level 5=1241kN. The measured tendons elongation values of left box girder No.8 are more than the theoretical values. For left and right box girder No. 9, side external tendons of left box No. 10, and left and right box girder No. 11, the measured values are less than theoretical values of elongation. After tension process, there are no new cracks in the top, web, and bottom of anchor beam and a small number of cracks developed slightly. These cracks are found around ducts of external tendons. The length of cracks rang from 0.03m to 0.5m and width rang from 0.05 mm and 0.25mm. The longitudinal deformation of the interface and top of anchor beam is very small, ranging from 0.001mm to0.115mm, which averaged 0.026mm. The overall state of anchor beams and box girders during strengthening is good.

Effect of the Hydration Heat on Creep

2013 ◽  
Vol 405-408 ◽  
pp. 2507-2510
Author(s):  
Rui Rao ◽  
Yong Hui Huang ◽  
Ai Rong Liu
Keyword(s):  
General Condition ◽  
Hydration Heat ◽  
Box Girders ◽  
Box Girder ◽  
Creep Stress ◽  
The Relationship

A method for the box girders creep calculation considering the hydration heat is proposed and the effect of the hydration on the creep is discussed. The box girder is divided into several components and the average hydration temperature of the component is defined to represent the general condition resulted in the hydration. The formulae of the average hydration temperature have been recommended based on the discussion with respect to the formulae accuracy. The effect of the hydration on the creep is changed into that of the variable age of loading and the relationship between them is also given. It has been found that the hydration decreases the creep stress obviously.

Design and Analysis of Anchorage Zone and Deviation Block of External Prestressed Concrete Bridge

2013 ◽  
Vol 710 ◽  
pp. 342-347
Author(s):  
Bing Yi ◽  
Fang Yuan Li
Keyword(s):  
Prestressed Concrete ◽  
Optimization Design ◽  
Finite Element Models ◽  
3D Fem ◽  
Box Girder ◽  
Continuous Rigid Frame Bridge ◽  
Rigid Frame ◽  
Key Points ◽  
Prestressed Concrete Bridge ◽  
Rigid Frame Bridge

As an external prestressed concrete box girder continuous rigid-frame bridge with the longest span in China, the Xiantan Bridge was reported in this paper for its special characteristics. The key points of the end cross beam for anchorage zone and deviation block for the deviator were introduced in detail for its design. The finite element models for them with 3D FEM were created to get the stress state to ensure the safety. Taking the stress distribution results into account, the optimization design for the thickness for these key locations was reported too. The results can provide reference for the similar projects.

Creep Effects on Simply Supported Prestressed Concrete Box Girder of High-Speed Railway with Ballastless Tracks

2012 ◽  
Vol 238 ◽  
pp. 733-737 ◽  
Author(s):  
Wang Fang ◽  
Bing Han ◽  
Shao Kun Yang
Keyword(s):  
Prestressed Concrete ◽  
High Speed ◽  
Element Model ◽  
Dead Load ◽  
Box Girders ◽  
Box Girder ◽  
High Speed Railway ◽  
Simply Supported ◽  
Creep Models ◽  
Curing Age

Creep will lead to increasing deflection of prestressed concrete girder, which may induce rails uneven, especially to ballastless tracks in high-speed railways. In this paper, two creep models, CEB-FIP90 and ACI209, were used in a finite element model to analyze influences of creep on simply supported prestressed concrete box girders which are used in high-speed railway in China. Sensitivity analysis was carried on towards curing age, secondary dead load, loading time and prestressing method on deformation of the girder. The results show creep should be controlled in engineering to ensure driving security.

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