Papers by Keyword: Prestressed Concrete

Abstract: On the south of Brazil the main Brazilian highway pass around the town Laguna only on a dual lane carriage way. There are regular traffic congestions with several hours of delay. The federal government invests a lot of money to increase the capacity of the main highway. The bridge over Canal Laranjeiras takes part of these improvements. It has a total length of 2 800m and overpasses two times the railway, the Laguna bay to Imauri and future navigation channel Laranjeiras. Its main part consists of 400m length of cable-stayed bridge with two pylons a 200m main span. The pylons are 76m height and are formed by box section. The cable-stayed part is situated in plan curvature and the main plane of longitudinal stays is supplemented by two planes of transversal stays for each pylon. The paper deals with conceptual design of the bridge and construction methodology.

Abstract: Using the finite element software ANSYS to establish the model of prestressed concrete T beam .With the combination of dynamic and static load test data, the objective function was constructed by taking the vertical deflection of the static load test and the top five vertical natural frequency of dynamic test as state variables. The results revealed that,after being modified ,the error between the calculation value and the testal results of the model was converged in a reasonable error range.In addition ,The modified model could be used in the assessment of bridge structure performance,and it shows the practical application value.

Abstract: The Hodder Avenue underpass – recipient of the Precast/Prestressed Concrete Institute (PCI)’s Harry H. Edwards Industry Advancement Award – is a new highway bridge near Thunder Bay, Canada that utilized a modular construction approach facilitated by the extensive use of ultra-high performance fibre-reinforced concrete (UHPFRC) to expedite construction, elevate aesthetic value and enhance quality and durability. Almost all structural components were precast in facilities and assembled on site using UHPFRC joints, which have compact geometries with less complexity, superior durability and strength. The precast elements include a unique UHPFRC pier cap and pier column shells, high performance concrete (HPC) box girders, sidewalks/parapet walls, abutment caps, ballast walls, slope paving panels and approach slabs. Aesthetically, the structure achieved a slender and open form with the use of shallow precast box girders and a unique pier cap visually and structurally integral with the superstructure. The cap beam was prestressed and precast fully with UHPFRC to overcome design challenges such as geometrical limitations and complex loading. The pier cap and girders were made composite using field-cast UHPFRC joints reinforced with stainless steel bars and threaded bolts. The pier columns also utilized a unique design with precast UHPFRC shells serving as an aesthetic stay-in-place form as well as a protective layer for the salt splashes during Thunder Bay’s harsh winter seasons.

Abstract: With the continuous development of China's coal technology, prestressed concrete stand in the coal mine construction jobs because of the building structure stiffness, mechanical characteristics, and other characteristics of joints less widely used. Firstly, the main concepts of prestressed concrete is analyzed, combined with the building of a coal mine stent design prestressed concrete examples of the main problems in the mine design process involved the stent to expand a detailed analysis and discussion, hoping to mine construction of large buildings play a guiding role in improving mine safety production conditions, to provide reliable protection for coal mine safety.

Abstract: On the basis of the joint model experiment, the non-linear performance of joints is analysed by using finite element program. The concrete stress distribution, stirrups stress and dangerous area of joints with spread-ended beams are discussed. Finite element analysis shows that effective prestressing tendons through the joint core region play a beneficial role in concrete and can improve the compressive strengths of concrete, and help to improve the shear strength of joints. Finally, according to experiments and theoretical analysis, the beginning of the haunched region is the dangerous area of joint. In order to avoid concrete tension failure when exerting prestress, the beginning of the haunched region must have enough transverse U-shaped bars to resist the prestressing tension.

Abstract: Based on the concrete carbonization theory, we analyze the time when prestressed steel strands begin to corrode, and put forward the degradation time-dependent model for cross-sectional area of a corroding steel strand; with the comparison of existing research results, we propose the degradation time-dependent model for mechanical properties of corroded steel strands, including the nominal ultimate strength and nominal elastic modulus. We deduce a time-dependent model for the prestressing loss due to steel strand corrosion. Taking a prestressed concrete hollow slab bridge as an example, we analyze the time-dependent effect of the corroded strands on the concrete stress at serviceability limit state and flexural bearing capacity at ultimate limit state. Research shows that the bottom edge stress and flexural bearing capacity at mid-span of the beams will reduce sharply if the prestressed strands corrode, even corrosion can damage the safety of bridge in just a few years. These results can be for information of further experiments and researches.

Abstract: The topic of this paper is the description of different approaches to numerical simulation of prestressed concrete in computational system ANSYS 14.5. Due to increasing popularity of the numerical simulations, the paper aims to divide and describe simple methods and related aspects of modeling prestress on the finite element level. The paper contains three main part: the analytical solution, the numerical solution and the final comparison of the results. The obtained numerical results proved applicability of FEA for solving problems of prestressed concrete elements.

Abstract: The purpose of this paper is aimed at according to the "highway reinforced concrete and prestressed concrete bridge and culvert design specifications (JTG D62-2004) and (JTJ 023-85) design of jacking construction of continuous girder bridge for reliability analysis. By establishing a finite element model of construction stage and into a bridge stage respectively the reliability index of the typical cross section is analyzed. Aiming at construction stage, by choosing typical cross section of reliability analysis, draw a cross section of reliability index with the change of construction stage. Calculation results show that, according to JTG D62-2004 specification of reliability index calculation results than based on results of calculating the JTJ 023-85 specification. In this paper, the analysis results can provide reference for pushing the construction of the continuous girder bridge design.

Abstract: Prestressed concrete continuous rigid frame bridge is widely used in bridge engineering. Its closure is one of very important working procedure in the bridge construction. In this paper, taking Liangjiang Great Bridge in Xinxu Highway as an example, the methods for determining the Jacking force and displacement are discussed. The implementation of the process and construction technology of closure jacking scheme is introduced in detail. Through the finite element simulation, the stress state of on the structural pusher is analyzed. And the maximum stress of the pier bottom and the displacement of the pier top are obtained. They can verify the feasibility of the scheme. Monitoring results from the site construction verify the safety of the scheme. The method has a certain reference value on jacking closure construction for the similar bridge.

Abstract: Concrete continuous box- girder bridges have a large proportion in small span and long span bridges, and it has very broad prospects for development. Along with the large-scale construction of this kind of bridge, various problems have also emerged, especially the damage of RC beam’s diagonal section in bridge girder deflection. It always appears the inclined cracks in webs which cause by principal tensile stress, so it will be the potential damage to the whole bridge. However, the existence of the vertical prestress, will make the principal tensile stress of box girder in greatly reduced. So as to make cracking resistance performance of diagonal section is better than the ordinary reinforced concrete bridge. For an engineering example, this paper puts forward several different vertical prestressed steel arrangements. Based on different decorate a form of vertical pretressd bridge girder under stress numerical simulation, it is concluded that bridge’s web principal tensile stress distribution and its variation law, and then optimize the vertical reinforcing steel arrangement, improve the overall safety of bridge structure. It can provide the reference in the process of construction when we face the similar problems in the future.