Comprehensive safety recommendations for the precast concrete products industry.

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Applications of precast concrete in repair and replacement of civil works structures /

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Performance of 1/3-scale model precast concrete beam-column connections subjected to cyclic inelastic loads : report no. 4 /

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Precast Concrete Elements for Accelerated Bridge Construction Final Report, Volume 1-1. Laboratory Testing of Precast Substructure Components: Boone County Bridge, January 2009

In July 2006, construction began on an accelerated bridge project in Boone County, Iowa that was composed of precast substructure elements and an innovative, precast deck panel system. The superstructure system consisted of full-depth deck panels that were prestressed in the transverse direction, and after installation on the prestressed concrete girders, post-tensioned in the longitudinal direction. Prior to construction, laboratory tests were completed on the precast abutment and pier cap elements. The substructure testing was to determine the punching shear strength of the elements. Post-tensioning testing and verification of the precast deck system was performed in the field. The forces in the tendons provided by the contractor were verified and losses due to the post-tensioning operation were measured. The stress (strain) distribution in the deck panels due to the post-tensioning was also measured and analyzed. The entire construction process for this bridge system was documented. Representatives from the Boone County Engineers Office, the prime contractor, precast fabricator, and researchers from Iowa State University provided feedback and suggestions for improving the constructability of this design.

Precast Concrete Elements for Accelerated Bridge Construction Final Report Volume 2. Laboratory Testing, Field Testing, and Evaluation of a Precast Concrete Bridge: Madison County Bridge, January 2009

The importance of rapid construction technologies has been recognized by the Federal Highway Administration (FHWA) and the Iowa DOT Office of Bridges and Structures. Recognizing this a two-lane single-span precast box girder bridge was constructed in 2007 over a stream. The bridge’s precast elements included precast cap beams and precast box girders. Precast element fabrication and bridge construction were observed, two precast box girders were tested in the laboratory, and the completed bridge was field tested in 2007 and 2008.

Precast Concrete Elements for Accelerated Bridge Construction Final Report Volume 3. Laboratory Testing, Field Testing, and Evaluation of a Precast Concrete Bridge: Black Hawk County,v January 2009

The importance of rapid construction technologies has been recognized by the Federal Highway Administration (FHWA) and the Iowa DOT Office of Bridges and Structures. Black Hawk County (BHC) has developed a precast modified beam-in-slab bridge (PMBISB) system for use with accelerated construction. A typical PMBISB is comprised of five to six precast MBISB panels and is used on low volume roads, on short spans, and is installed and fabricated by county forces. Precast abutment caps and a precast abutment backwall were also developed by BHC for use with the PMBISB. The objective of the research was to gain knowledge of the global behavior of the bridge system in the field, to quantify the strength and behavior of the individual precast components, and to develop a more time efficient panel-to-panel field connection. Precast components tested in the laboratory include two precast abutment caps, three different types of deck panel connections, and a precast abutment backwall. The abutment caps and backwall were tested for behavior and strength. The three panel-to-panel connections were tested in the lab for strength and were evaluated based on cost and constructability. Two PMBISB were tested in the field to determine stresses, lateral distribution characteristics, and overall global behavior.

Analysis of a semi-rigid connection for precast concrete

This paper presents a study of a specific type of beam-to-column connection for precast concrete structures. Furthermore, an analytical model to determine the strength and the stiffness of the connection, based on test results of two prototypes, is proposed. To evaluate the influence of the strength and stiffness of the connection on the behaviour of the structure, the results of numerical simulations of a typical multi-storey building with semi-rigid connections are also presented and compared with the results using pinned and rigid connections. The main conclusions are: (a) the proposed design model can reasonably evaluate the studied connection strength; (b) the evaluation of strength is more accurate than that of stiffness; (c) for a typical structure, it is possible to increase the number of storeys of the structure from two to four with lower horizontal displacement at the top, and only a small increase of the column base bending moment by replacing the pinned connections with semi-rigid ones; and (d) although there is significant uncertainty in the connection stiffness, the results show that the displacements at the top of the structure, and the column base moments present low susceptibility deviations to this parameter.

An Integral Abutment Bridge with Precast Concrete Piles, May 2007

The use of precast, prestressed concrete piles in the foundation of bridge piers has long been recognized as a valuable option for bridge owners and designers. However, the use of these precast, prestressed concrete piles in integral abutment bridges has not been widespread because of concerns over pile flexibility and the potential for concrete cracking and deterioration of the prestressing strands due to long-term exposure to moisture. This report presents the details of the first integral abutment bridge in the state of Iowa that utilized precast, prestressed concrete piles in the abutment. The bridge, which was constructed in Tama County in 2000, consists of a 110 ft. long, 30 ft. wide, single-span PC girder superstructure with a left-side-ahead 20º skew angle. The bridge was instrumented with a variety of strain gages, displacement sensors, and thermocouples to monitor and help in the assessment of structural behavior. The results of this monitoring are presented, and recommendations are made for future application of precast, prestressed concrete piles in integral abutment bridges. In addition to the structural monitoring data, this report presents the results of a survey questionnaire that had been mailed to each of the 50 state DOT chief bridge engineers to ascertain their current practices for precast, prestressed concrete piles and especially the application of these piles in integral abutment bridges.

Precast Concrete Panel Thickness for Epoxy-Coated Prestressing Strands, Volume 1, HR-353, 1994

This final report for Phase 1 of the research on epoxy-coated, prestressing strands in precast prestressed concrete (PC) panels has been published in two volumes. This volume, Volume 1--Technical Report, contains the problem description, literature review, and survey results; descriptions of the test specimens, experimental tests, and analytical models; discussions of the analytical and experimental results; summary, conclusions, and recommendations; list of references; and acknowledgment. Volume 2--Supplemental Report contains additional information in the form of summarized responses to the questionnaires; graphs showing the strand forces; figures showing the geometry of the specimens and concrete crack patterns that formed in the strand transfer length and strand development length specimens; and graphs of the concrete strains in the strand transfer length specimens, load-point deflections, and strand-slip measurements for the strand development length specimens.

Precast Concrete Panel Thickness for Epoxy-Coated Prestressing Strands, Volume 2, HR-353, 1994

This final report for Phase 1 of the research on epoxy-coated, prestressing strands in precast prestressed concrete (PC) panels has been published in two volumes. Volume 1--Technical Report contains the problem description, literature review, and survey results; descriptions of the test specimens, experimental tests, and analytical models; discussions of the analytical and experimental results; summary, conclusions, and recommendations; list of references; and acknowledgments. Volume 2--Supplemental Report contains additional information in the form of appendix material for Volume 1 on the questionnaires, strand forces, geometry of the specimens, concrete crack patterns that formed in the strand transfer length and strand development length specimens, concrete strains in the strand transfer length specimens, and load-point deflections and strand-slip measurements for the strand development length specimens. Appendix A contains the questionnaires that were sent to the design agencies and precast concrete producers. A summary of the results to the questions on the surveys are given as the number of respondents who provided the same answers and as paraphrased comments from the respondents. Appendix B contains graphs of strand force versus time, strand force versus temperature, and strand force versus strand cutting sequence for the concrete castings. Appendix C contains figures that show the location of each specimen in the prestress bed, the geometrical configurations for the strand transfer length (T-type) specimens and strand development length (D-type) specimens, and the concrete cracks that developed in some of the T-type specimens when they were prestressed. Appendix D contains figures that show the concrete cracks that developed in the D-type specimens during the strand development length tests. For each of these tests, the sequence of the failure for the specimen is specified. Appendix E contains graphs of concrete strain versus distance from the end of the T-type specimens that were instrumented with internal embedment strain gages. Appendix F contains graphs of load versus load-point deflection and load versus strand-slip for the strand development length tests of the D-type specimens.

Field and Laboratory Evaluation of Precast Concrete Bridges, TR-440, 2001

Recent data compiled by the National Bridge Inventory revealed 29% of Iowa's approximate 24,600 bridges were either structurally deficient or functionally obsolete. This large number of deficient bridges and the high cost of needed repairs create unique problems for Iowa and many other states. The research objective of this project was to determine the load capacity of a particular type of deteriorating bridge – the precast concrete deck bridge – which is commonly found on Iowa's secondary roads. The number of these precast concrete structures requiring load postings and/or replacement can be significantly reduced if the deteriorated structures are found to have adequate load capacity or can be reliably evaluated. Approximately 600 precast concrete deck bridges (PCDBs) exist in Iowa. A typical PCDB span is 19 to 36 ft long and consists of eight to ten simply supported precast panels. Bolts and either a pipe shear key or a grouted shear key are used to join adjacent panels. The panels resemble a steel channel in cross-section; the web is orientated horizontally and forms the roadway deck and the legs act as shallow beams. The primary longitudinal reinforcing steel bundled in each of the legs frequently corrodes and causes longitudinal cracks in the concrete and spalling. The research team performed service load tests on four deteriorated PCDBs; two with shear keys in place and two without. Conventional strain gages were used to measure strains in both the steel and concrete, and transducers were used to measure vertical deflections. Based on the field results, it was determined that these bridges have sufficient lateral load distribution and adequate strength when shear keys are properly installed between adjacent panels. The measured lateral load distribution factors are larger than AASHTO values when shear keys were not installed. Since some of the reinforcement had hooks, deterioration of the reinforcement has a minimal affect on the service level performance of the bridges when there is minimal loss of cross-sectional area. Laboratory tests were performed on the PCDB panels obtained from three bridge replacement projects. Twelve deteriorated panels were loaded to failure in a four point bending arrangement. Although the panels had significant deflections prior to failure, the experimental capacity of eleven panels exceeded the theoretical capacity. Experimental capacity of the twelfth panel, an extremely distressed panel, was only slightly below the theoretical capacity. Service tests and an ultimate strength test were performed on a laboratory bridge model consisting of four joined panels to determine the effect of various shear connection configurations. These data were used to validate a PCDB finite element model that can provide more accurate live load distribution factors for use in rating calculations. Finally, a strengthening system was developed and tested for use in situations where one or more panels of an existing PCDB need strengthening.

A cost optimization-based design of precast concrete floors using genetic algorithms

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Behaviour of grouted dowels used in precast concrete connections

This research deals with the behaviour of grouted dowels used in beam-to-column connections in precast concrete structures. The research focuses primarily on the theoretical and experimental analysis of the resistance mechanism of the dowels. The experimental programme included 15 models for analysing the following variations in dowel parameters: a) dowel diameters of 16, 20 and 25 mm, b) dowel inclinations of 0 degrees (i.e. perpendicular to the interface), 45 degrees and 60 degrees, c) compressive strength of classes C35 and C50 for the concrete adjacent to the dowels, and d) the absence or presence of compressive loads normal to the interface. The experimental results indicate that the ultimate capacity and shear stiffness of the inclined dowels are significantly higher than those of the perpendicular dowels. Based on these results, an analytical model is proposed that considers the influence of the parameters studied regarding the capacity of the dowel.

The strength of precast concrete pipe reinforced with welded wire fabric /

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