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Optimum span length for a PCI-girder expressway bridge
Abstract
In the design of PCI-girder bridges, the application of various optimum design methodologies can result in significant cost savings and improved structural performance. However, most of the optimisation techniques focus on the individual components and the overall structural system of the superstructure of the bridge system. Limited studies are carried out in the context of longitudinal and transverse configurations of the members in a particular bridge system. This study identifies the optimum span for the PCI-girder expressway bridge system by adopting longitudinal and transverse arrangement of members as design variables while keeping the cross-section of the girder constant. Using an existing case study bridge structure located in Bangkok, selected parametric studies are carried out to achieve cost optimisation. It is observed that the optimum span range for the PCI-girder bridge is in the range of 25 m (82 ft) to 33 m (108 ft).
The traditional stability evaluation method of corrugated steel web box girder ignores the calculation of evaluation index weight, which leads to large deviation of evaluation results. Therefore, a new fuzzy comprehensive evaluation method for the overall stability of box girder with corrugated steel webs is proposed. According to the structural characteristics of corrugated steel web box girder, the stability coefficient of corrugated steel web box girder is calculated, and the stability calculation index of corrugated steel web box girder is obtained. In this paper, the constraint equation of bridge instability process is introduced, and Midas civil software is used to simulate the instability of box girder with corrugated steel webs during bridge construction. Based on this, the instability of the bridge is analyzed, the index weight of the anti-instability ability of the box girder with corrugated steel webs under different loads is calculated, and the overall stability of the box girder with corrugated steel webs is evaluated by fuzzy comprehensive evaluation. The test results show that this method can accurately evaluate the overall stability of box girder with corrugated steel webs, and the calculation accuracy is increased by 32.7% and the calculation speed is increased by about 1.62 seconds. It has high credibility and authenticity.
Recent surveys have indicated that between 30% and 40% of all bridges in North America are in various states of deterioration. Funding is limited owing to the existence of other deficient components of the transportation infrastructure. It is clear, therefore, that the return on the available funding needs to be maximized. This paper presents a review of publications on cost optimization of concrete bridge components and systems and then continues with a review of the state-of-the-art in life-cycle cost (LCC) analysis and design of concrete bridges. The main objective of the paper is to encourage bridge engineers to move towards the increased use of advanced analysis and design optimization methods.Key words: bridge, concrete, cost, high-performance concrete, infrastructure, life-cycle cost, optimization, prestressed girders, reliability.Des relevés récents indiquent qu'entre 30 % et 40 % de tous les ponts en Amérique du Nord sont à des niveaux variés de détérioration. Le financement est limité en raison de l'existence d'autres composantes déficientes de l'infrastructure de transport. Il est donc clair que le retour sur le financement disponible doit être maximisé. Cet article présente une revue des publications sur l'optimisation des coûts des composantes et des systèmes de ponts en béton. L'article poursuit ensuite avec une revue de ce qui est d'avant-garde dans l'analyse des coûts de cycle de vie et de conception des pont en béton. L'objectif principal de cet article est d'encourager les ingénieurs en structures de ponts à utiliser d'avantage les méthodes d'analyse évoluées et d'optimisation de conception.Mots clés : pont, béton, coût, béton haute performance, infrastructure, coût du cycle de vie, optimisation, poutres précontraintes, fiabilité.[Traduit par la Rédaction]
Designers have experienced limitations when using existing precast, prestressed concrete I-girders in continuous span bridges. The Nebraska University (NU) girder series was recently developed to overcome these limitations and to take advantage of recent advances in precast concrete production technology. This paper presents a brief history of precast, prestressed concrete bridge I-girder development, the procedure undertaken to develop the NU girder series, performance comparisons with several existing standard girder shapes, and the steps taken by the Nebraska Department of Roads to implement the research results.
Minimum Design Loads for Buildings and Other Structures provides requirements for general structural design and the means for determining dead, live, soil, flood, wind, snow, rain, atmospheric ice, and earthquake loads, as well as their combinations, which are suitable for inclusion in building codes and other documents. This Standard, a complete revision of ASCE/SEI 7-02, includes revised and significantly reorganized provisions for seismic design of structures, as well as revisions in the provisions for determining live, flood, wind, snow, and atmospheric ice loads. Supplement No. 1, which is included with the Standard, ensures full and complete coordination between ASCE/SEI 7-05 and the 2006 International Building Code. The updates which comprise Supplement No. 1 are seamlessly integrated into this volume and are not available anywhere else.
ASCE/SEI 7-05 is an integral part of building codes in the United States. The earthquake load provisions in ASCE 7-05 are substantially adopted by reference in the 2006 International Building Code and the 2006 NFPA 5000 Building Construction and Safety Code. Many other provisions, including calculations for wind and snow loads, are also adopted by reference by both IBC and NFPA model building codes.
Structural engineers, architects, and those engaged in preparing and administering local building codes will find this Standard an essential reference in their practice.
This is a report on an investigation done to evaluate latest prestressed concrete bridge girders in the United States and to determine which are optimum designs that could be promoted as national or regional standards. The study was limited to bridges with pretensioned I- and T-sections with spans in excess of 80 ft, concrete compressive strengths up to 7000 psi, and 5- and 6-in. webs. After completion of the study, Modified Bulb-T girders with 6-in.-thick webs are recommended for use as the national standard in precast, prestressed concrete bridges with spans from 80 to 140 ft.
A practical approach to the optimal design of precast, prestressed concrete highway bridge girder systems is presented. The approach aims at standardizing the optimal design of bridge sections. Structural system optimization is shown to be more relevant than conventional girder optimization for an arbitrarily chosen structural system. Bridge system optimization is defined as the optimization of both longitudinal and transverse bridge configurations (number of spans, number of girders, girder type, reinforcements and tendon layout). As a result, the preliminary design process is much simplified by using some developed design charts from which selection of the optimum bridge system, number and type of girders, and amounts of prestressed and non-prestressed reinforcements are easily obtained for a given bridge length, width and loading type.
According to the Federal Highway Administration, almost one-quarter of the more than one-half-million U.S. bridges make use of prestressed concrete beams in their designs. In this paper, a method is presented for the total cost optimization of precast, prestressed concrete I-beam bridge systems, by taking into account the costs of the prestressed concrete, deck concrete, prestressed I-beam steel, deck reinforcing steel, and formwork. The problem is formulated as a mixed integer-discrete nonlinear programming problem and solved using the robust neural dynamics model of Adeli and Park. An example is presented to demonstrate the practical application of the methodology. Typical network convergence curves using three different network starting points demonstrate the excellent convergence and the robustness of the optimization model presented in this paper.
There are three main types of concrete bridges in the United States. These types are cast-in-place, precast and special long span bridges. The focus in this paper is on precast concrete bridges, especially precast concrete I-girder bridges. The design of I-girder bridges can be optimized by increasing the area of the bottom flange, by using welded wire reinforcement for shear reinforcement, by using high-performance concrete, or by splicing the I-girders. Stay-in-place deck slab forms or full depth deck slab panels are used to achieve rapid construction, improve safety and reduce the cost of the deck slab removal.In order to increase precast concrete I-girder spans while minimizing the superstructure depth, four different systems for creating continuous spliced concrete I-girders are presented. The first system is limited to spans where full-span segment lengths are spliced over the piers. Within the first system, three different methods of continuity are presented. The other three systems are cantilever type bridges which utilize post-tensioning of partial span segments, with prismatic or non-prismatic pier segments. Comparisons among the system capacities are presented. Details of a specific bridge (Highland View Bridge) are presented here, to provide an example of spliced precast I- girders. Copyright © 2007 John Wiley & Sons, Ltd.
The purpose of this study is to optimize the topology and shape of prestressed concrete bridge girders. An optimum design
approach that uses a genetic algorithm (GA) for this purpose is presented. The cost of girders is the optimum design criterion.
The design variables are the cross-sectional dimensions of the prefabricated prestressed beams, the cross-sectional area of
the prestressing steel and the number of beams in the bridge cross-section. Stress, displacement and geometrical constraints
are considered in the optimum design. AASHTO Standard Specifications for Highway Bridges are taken into account when calculating
the loads and designing the prestressed beams. A computer program is coded in Visual Basic for this optimization. Many design
examples from various applications have been optimized using this program. Several of these examples are presented to demonstrate
the efficiency of the algorithm coded in the study.
This investigation comprised four major tasks: (1) Survey of existing precast, pretensioned bridge girder sections in the United States; (2) Evaluation of the structural efficiency and cost effectiveness of girder sections from the survey; (3) Selection of best girders to use within given span range; and (4) Development of design aids to determine appropriate girder cross section for given span range and finding the required number and layout of prestressing strands. It was found that for the state of Indiana, Kentucky bulb tees are more efficient than standard AASHTO girders in spans from 90 to 130 ft (27.4 to 39.6 m).
AASHTO LRFD Bridge Design Specifications. Washington: American Association of State Highway and Transportation Officials
- Aashto
AASHTO. 2012. AASHTO LRFD Bridge Design Specifications.
Washington: American Association of State Highway and
Transportation Officials.
Memos to Designers 10-20 Attachment 2: Deck Slab Thickness and Reinforcement Schedule
- Caltrans
Caltrans. 2008. Memos to Designers 10-20 Attachment 2: Deck
Slab Thickness and Reinforcement Schedule. Sacramento,
CA: California Department of Transportation.
Bridge Design Practice. California: Department of Transportation. DPT 1302-52
- Caltrans
Caltrans. 2015. Bridge Design Practice. California:
Department of Transportation.
DPT 1302-52. 2009. Seismic Design Forces to Medium-rise
Buildings. Bangkok: Department of Public Works and
Town &Country Planning.
Analysis of Pre-Stressed Flyover Elements
- Durga Bhavani
- K Sandhya
- M D Waseem
- M. Manoj Kumar
Durga Bhavani, B., K. Jeevana Sandhya, M. D. Waseem,
and M. Manoj Kumar. 2018. "Analysis of Pre-Stressed
Flyover Elements." International Journal of Innovative
Research in Science 7 (3): 2917-2923.