scholarly journals Strengthening and Rehabilitation of U-Shaped RC Bridges Using Substitute Cable Ducts

2019 ◽  
Vol 2019 ◽  
pp. 1-21
Author(s):  
Adam Svoboda ◽  
Ladislav Klusáček ◽  
Martin Olšák
Keyword(s):  
Bridge Deck ◽  
High Efficiency ◽  
Concrete Bridges ◽  
Traffic Load ◽  
Structural System ◽  
Historical Structures ◽  
Reinforced Concrete Bridges ◽  
Before And After ◽  
Post Tensioning ◽  
Existing Bridges

The presented paper deals with strengthening and rehabilitation of U-shaped reinforced concrete bridges from the period of 1905–1930 using post-tensioning, which is a suitable, reliable, and durable method. These bridges have two main beams pulled over the bridge deck, which is supported by cross girders. The cross girders connect the two main beams forming a half-frame in the transverse direction, which provides spatial rigidity to the structure. The spans of these bridges are usually between 15 and 25 m. The high efficiency of post-tensioning can be seen on many implemented applications for bridge reconstructions worldwide. However, in this paper, the post-tensioning method is extended by a unique structural system of substitute cable ducts that allows for significantly expanding applicability of this method on existing concrete bridges. This method is highly recommended due to minimization of interventions into the constructions, unseen method of cable arrangement, and hence the absence of impact on appearance, which is appreciated not only in case of valuable historical structures but in general as well. In conclusion, the post-tensioning by monostrands in substitute cable ducts is a highly efficient method for strengthening of existing bridges in order to increase their load-bearing capacities in terms of current traffic load and to extend their service life. This method was also verified by monitoring the behavior of rehabilitated bridges before and after strengthening.

A methodology for evaluating the effects of spalling on the structural capacity of reinforced concrete bridge girders

2014 ◽  
Vol 41 (3) ◽  
pp. 197-205 ◽  
Author(s):  
Jeffrey Luckai ◽  
Maria Anna Polak ◽  
Scott Walbridge
Keyword(s):  
Reinforced Concrete ◽  
Rapid Assessment ◽  
Concrete Bridges ◽  
Bridge Girders ◽  
Reinforced Concrete Bridge ◽  
Reinforced Concrete Bridges ◽  
Structural Capacity ◽  
Practical Evaluation ◽  
Deterioration Mechanism ◽  
Existing Bridges

Corrosion of the reinforcing steel is a primary deterioration mechanism for reinforced concrete bridges. The spatial distribution of such spalling, relative to bar splices and laps, has not been considered in previous studies and may have a significant influence on structural capacity. In this paper, a modified area concept for considering this spalling is proposed. A methodology has been developed that employs this concept for the practical evaluation of existing bridges. It uses graphical spalling surveys, reinforcement layout information, and existing information regarding material and geometric properties as inputs for the flexural and shear analysis of deteriorated bridge girders. This methodology is easily adapted for full bridge analysis and to consider the effects of bar section loss and bond deterioration. A case study bridge is evaluated to show that this methodology offers a viable tool for the rapid assessment of spalled bridge girders to facilitate the prioritization of rehabilitation projects.

Monitoring of a Norwegian steel-concrete bridge strengthening for composite action

2021 ◽  
Author(s):  
Victor Vestman ◽  
Peter Collin ◽  
Robert Hällmark ◽  
Magnús Arason
Keyword(s):  
Load Capacity ◽  
Design Procedure ◽  
Concrete Bridges ◽  
Traffic Load ◽  
Traffic Density ◽  
Concrete Bridge ◽  
Composite Action ◽  
Shear Connectors ◽  
Coiled Spring ◽  
Existing Bridges

<p>Traffic density and vehicle weight have been increasing over time, which implies that many existing road bridges were not designed for the high service loads and the increased number of load cycles that they are exposed to today. One way to increase the traffic load capacity of non-composite steel- concrete bridges is to use post-install shear connectors and one type of shear connector is the coiled spring pin. This type of connector has advantages for strengthening of existing bridges, since it enables an installation from below while the bridge is still in service and does not bring along removal of concrete and pavement, nor welding to the top flange.</p><p>This paper describes one ~50 years old Norwegian single span steel-concrete bridge that was strengthened with post-installed coiled spring pins. The strengthening method and the design procedure are presented, along with the results from a field monitoring on Sagstu bridge, performed to evaluate the behaviour of the strengthened structure. The results show that the coiled spring pins counteract the slip and bring along a very good degree of composite action.</p>

The Story of the Koror Bridge

10.2749/cs001 ◽  
2014 ◽  
Author(s):  
Man-Chung Tang
Keyword(s):  
Bridge Deck ◽  
Structural System ◽  
Design Recommendations ◽  
Long Time ◽  
Post Tensioning ◽  
The Republic ◽  
Republic Of Palau ◽  
Engineering Firm ◽  
Concrete Girder

<p>Koror Babeldaob Bridge, also called Koror Babelthuap Bridge or simply Koror Bridge, connects the islands of Koror and Babeldaob in the Republic of Palau. The design of the bridge began in 1974 and was based on the prevailing AASHO Standard Specifications at that time and was supplemented by ACI and CEB-FIP design recommendations on an as-needed basis. When the Koror Bridge was opened to traffic in April 1977, it was the world's longest concrete girder span. A few years later, the bridge began to deflect more than had been anticipated. The owner commissioned a Japanese engineering firm in 1985 and then a US engineering firm in 1993 to conduct in-depth investigations of the structure. Both firms came to the same conclusion that the bridge was structurally safe and that the excessive deflection was an unexplainable phenomenon. Nevertheless, in order to improve the driving quality of the bridge deck, the owner decided to repair the bridge. The repair scheme made changes to the structural system and added a large amount of post-tensioning force to the bridge. Unfortunately, less than three months after the repair, late in the afternoon on 26 September, 1996,nineteen and a half years after it was opened to traffic, the bridge collapsed. Thereafter, most of the documents were sealed as a result of litigation between the various parties and the debris was cleared. For a long time, it was impossible to study the facts surrounding the bridge's collapse. Only recently, through continuous probing by a group of engineers, were these documents made accessible to researchers.</p>

Possibility of Increasing the Load Bearing Capacity of Parapet Bridge Structures

2018 ◽  
Vol 272 ◽  
pp. 319-324
Author(s):  
Adam Svoboda ◽  
Ladislav Klusáček
Keyword(s):  
Reinforced Concrete ◽  
Concrete Beam ◽  
High Efficiency ◽  
Load Capacity ◽  
Reinforced Concrete Beam ◽  
Traffic Load ◽  
Load Bearing Capacity ◽  
Reinforced Concrete Bridge ◽  
Bridge Structures ◽  
Post Tensioning

Post-tensioning is a suitable, reliable and durable method for strengthening existing reinforced concrete bridge structures. The high efficiency of post-tensioning can be seen on many implemented applications for bridge reconstructions worldwide. There are still several thousands of beam and slab bridges the load capacity of which no longer meets the demanding transport conditions. The oldest reinforced concrete beam bridges, from 1905-1915, are designed according to the Austrian Ministry of Railways Bridge Standard of 1904 when the largest load to be considered was the 18-tonne road steamroller. These bridges are not dimensioned for the currently valid traffic load values. The paper deals with the strengthening of the parapet beam bridges from the period of 1905-1930. These bridges have two main beams pulled over the bridge deck which is supported by cross beams. The cross beams connect the two main beams, forming a half-frame in the transverse direction which provides spatial rigidity of the structure. The spans of these bridges are usually in the range of 15 to 25 m.

EFFICIENCY OF NEW HEMOSORBENT IN ACUTE AMITRIPTYLINE AND CYCLODOL POISONING

2020 ◽  
pp. 14-18
Author(s):  
A. M. Fomin
Keyword(s):  
Clinical Effect ◽  
High Efficiency ◽  
Initial Level ◽  
Synthetic Polymer ◽  
Complex Treatment ◽  
Direct Hemoperfusion ◽  
Selective Sorption ◽  
Positive Clinical Effect ◽  
Before And After

A complex treatment of a patient with acute amitriptyline and cyclodol poisoning using enterosorption, intestinal lavage and hemosorption on a new column with a synthetic sorbent is presented. A two-layer synthetic polymer column developed for the selective sorption of cytokines by direct hemoperfusion was used for hemosorption. Quantitative determinations of amitriptyline and cyclodol levels before and after the column, as well as before and after hemosorption have showed high efficiency of the sorbent to remove the toxicant from the blood. The use of 6-hour hemosorption allowed to reduce the level of amitriptyline from the initial level by more than 4 times and the level of cyclodol - by more than 3 times to therapeutic levels and to obtain a pronounced positive clinical effect in the complex treatment of a patient with severe poisoning.

scholarly journals Advanced treatment of effluent extended aeration process using biological aerated filter (BAF) with natural media: modification in media, design and backwashing process

AMB Express ◽  
2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mohammad Malakootian ◽  
Ali Toolabi ◽  
Saeed Hosseini
Keyword(s):  
High Efficiency ◽  
Treatment Plant ◽  
Hospital Wastewater ◽  
Optimal Method ◽  
Metal Grid ◽  
Before And After ◽  
The Media ◽  
Aeration Process ◽  
Aerated Filter ◽  
Natural Media

AbstractBiological aerated filters (BAFs) have high filtration efficiency due to their tolerance of hydraulic and organic shocks are suitable for the treatment of complex and sanitary wastewater. In this study, for the first time, natural media of date kernel from Bam city was used as the BAF reactor media, with a meshing sand filter separated by a standard metal grid from the natural filter section used at the end of the reactor. This can be considered an innovation in the media and filtration. Aeration in the related reactor with 160 cm height was performed bilaterally as up-flow and continuously by nozzles throughout the reactor media. In this work, the actual effluent of the hospital wastewater treatment plant was employed as the inflow wastewater to the reactor, and its organic and inorganic parameters were measured before and after the treatment by the BAF reactor. The backwashing process was also studied in three ways: bottom backwashing (TB), top backwashing (BB), and top and bottom backwashing (TBBS), to determine the amount of water consumed and to achieve the desired result. According to the results obtained in this study, the removal efficiencies of inorganic and microbial contaminants, amoxicillin and azithromycin were obtained as follows: BOD5: 98.48%, COD: 92.42%, $${\text{NO}}_{3}^{ - }$$ NO 3 - : 99.4%, P: 93.3%, Coliforms: 97%, Color: 42.8%, Turbidity: 95%, Sulphate: 30%, TSS: 98.9%, Amoxicillin: 20% and azithromycin: 13%. In the backwashing process, the amount of water consumed in these three TB, BB, and TBBS methods were obtained 300, 164, and 118 L, respectively, So, TBBS method was selected as the optimal method. Based on the results obtained in this study, it is concluded that the BAF process with natural date kernel has a high efficiency in removing organic and inorganic contaminants from hospital wastewater, also the concentration of most of the effluent parameters was less or in accordance with EPA standard.

The Effect of Type and Height of Piers on the Seismic Behavior of Reinforced Concrete Bridges

2019 ◽  
Vol 41 ◽  
pp. 79-87 ◽  
Author(s):  
Mohamed Cherif Djemai ◽  
Mahmoud Bensaibi ◽  
Fatma Zohra Halfaya
Keyword(s):  
Reinforced Concrete ◽  
Structural Parameters ◽  
Strong Motion ◽  
Concrete Bridges ◽  
Geometrical Parameters ◽  
Girder Bridges ◽  
Building Research Institute ◽  
Reinforced Concrete Bridges ◽  
Dynamic Analyses ◽  
Strong Motion Database

Bridges are commonly used lifelines; they play an important role in the economic activity of a city or a region and their role can be crucial in a case of a seismic event since they allow the arrival of the first aid. Reinforced concrete (RC) bridges are worldwide used type view their durability, flexibility and economical cost. In fact, their behavior under seismic loading was the aim of various studies. In the present study the effect of two structural parameters i.e. the height and the type of piers of reinforced concrete bridges on seismic response is investigated. For that reason, different multi-span continuous girder bridges models with various geometrical parameters are considered. Then, non-linear dynamic analyses are performed based on two types of piers which are: multiple columns bent and wall piers with varying heights. In this approach, a serie of 40 ground motions records varying from weak to strong events selected from Building Research Institute (BRI) strong motion database are used including uncertainty in the soil and seismic characteristics. Modelling results put most emphasis on the modal periods and responses of the top pier displacements, they show the influence of the considered parameters on the behavior of such structures and their impact on the strength of reinforced concrete bridges.

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