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International Concrete Abstracts Portal

Showing 1-5 of 595 Abstracts search results

Document: 

SP-342_01

Date: 

June 1, 2020

Author(s):

Benjamin Z. Dymond, Catherine E. W. French, Carol K. Shield

Publication:

Symposium Papers

Volume:

342

Abstract:

An experimental investigation was conducted on a full-scale prestressed concrete girder laboratory bridge to determine whether linear elastic shear distribution principles are conservative for load rating at ultimate capacity. A secondary goal was to determine whether existing web-shear cracks would be visible in an unloaded state. Two tests were conducted to failure (one near the end with a partial-depth diaphragm and one near the end without) to determine if the most loaded interior girder shed shear force to adjacent girders as it transitioned from uncracked to cracked to failure. Failure during each test was characterized by web-shear crushing and bridge deck punching at the peak applied load. Differences in the behavior of the two ends (with and without partial depth end diaphragm) affected the diagonal crack pattern, shear distribution, and loads at cracking and failure. The effect on loading was less than 10%. Inelastic shear distribution results indicated the girder carrying the most load redistributed shear to the other girders as it lost stiffness due to cracking. Use of linear elastic load distribution factors was conservative considering shear distribution at ultimate capacity. The visibility of web-shear cracks in an unloaded state was found to be a function of stirrup spacing.


Document: 

SP-342_02

Date: 

June 1, 2020

Author(s):

Marc Savard and Jean-François Laflamme

Publication:

Symposium Papers

Volume:

342

Abstract:

Several of the first prestressed concrete segmental bridges in North America were built in Quebec, Canada. The Rivière-aux-Mulets bridge was one of them. Built in the early 1960s, this bridge experienced several disorders due to inadequate design criteria enforced at that time. Despite a structural strengthening in the late 1980s, a bridge behavior follow-up has been required to ensure reliability. The structural health monitoring program implemented to track structural disorders, along with results from modal analysis and diagnostic load tests, is presented with a focus on the instrumentation and the data analysis. A three-dimensional finite element model was developed and calibrated using the frequencies and mode shapes detected under ambient traffic conditions. Data analyses showed that the expansion bearings were frozen, causing bending of the associated piers, which generated axial forces in the deck and decompression of concrete in the area surrounding active cracks. This process enables premature failure of prestressing tendons in the vicinity of these cracks, especially those located in the top flange, which is a corrosion-friendly environment. Development of cracks and associated prestress loss caused a reduction in the bridge load-carrying capacity. Analyses of health monitoring data led to acute assessment of the overall bridge structural performance.


Document: 

SP-340-02

Date: 

April 1, 2020

Author(s):

Olga Iatsko and Andrzej S. Nowak

Publication:

Symposium Papers

Volume:

340

Abstract:

In the new generation of design code, safety of structures is provided in form of load and resistance factors. Safety is measured in terms of the reliability index. The acceptability criterion in the selection of load and resistance factors is closeness to the target reliability index which can be different depending on limit state. The paper presents a procedure to determine these factors using the concept of “design point”. The coordinates of design point are equal to factored load or factored resistance. The required input data includes for each load component and resistance: mean values, bias factor (ratio of mean to nominal), standard deviation or coefficient of variation. The procedure is demonstrated on example of bridge design code (AASHTO[1]) and design code for concrete buildings (ACI 318[2]) for prestressed concrete girders and reinforced concrete beams in flexure and shear.


Document: 

SP-340-14

Date: 

April 1, 2020

Author(s):

Raymon W. Nickle and Yail J. Kim

Publication:

Symposium Papers

Volume:

340

Abstract:

With over 80 years of history, it is only in the last 20 years that the use of fiber reinforced polymer (FRP) materials has become feasible for bridge applications in part due to the ever increasing requirement to make structures last longer, with the current American Association of State Highway Transportation Officials (AASHTO) Load and Resistance Factor Design (LRFD) Bridge Design Specifications requiring that structures be designed for a 75 year design life; but also in the development of cost effective production techniques, and the introduction of FRP materials, which bring the cost and strength of FRP materials closer to traditional steel reinforcement. Published documents provide comprehensive recommendations on design methodology, predictive equations, and recommendations for strength and service limits states. In this paper, the background of FRP-prestressed concrete bridges is discussed and trial bridges are designed. Research needs to advance the state of the art are identified and delineated.


Document: 

SP-340-08

Date: 

April 1, 2020

Author(s):

Tevfik Terzioglu, Dongqi Jiang, Mary Beth D. Hueste, and John B. Mander

Publication:

Symposium Papers

Volume:

340

Abstract:

A new bridge system was recently developed for short span bridges in low clearance areas. This system uses the same concept as spread box beam bridges in which standard TxDOT precast prestressed slab beams are spaced apart. The deck is composed of stay-in-place precast concrete panels spanning between beams with a cast-in-place reinforced concrete deck. This paper presents a comprehensive approach for the investigation and development of this alternative spread slab beam bridge system including design, construction, field testing, modeling, and derivation of live load distribution factors (LLDFs). A parametric design study was conducted to evaluate the potential bridge spans when considering the four standard TxDOT slab beam types, a range of beam spacings, and potential bridge widths. One of the challenging geometries with widely spaced slab beams was constructed at full-scale to assess constructability and in-service behavior. The full-scale test bridge and a recently constructed on-system bridge with more closely spaced slab beams were tested under static and dynamic truck loads to obtain important insight into their structural performance and live load distribution behavior, while also providing data to guide analytical and computational modeling studies. Finite element models were developed to investigate an array of possible bridge geometries and determine the effect of key parameters on the load sharing behavior. Based on the research findings, it was concluded that spread slab beam bridges with a topped panelized deck provide a viable construction method for short-span bridges. For both tested bridges, the desired performance was achieved for in-service loading. Experimental and computational LLDFs were evaluated, and LLDF equations for spread box beams were reviewed for applicability to spread slab beam bridges. The AASHTO LRFD spread box beam LLDFs range from being unconservative to very conservative. Unique moment and shear LLDFs were developed for use in design of spread slab beam bridges.


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