International Concrete Abstracts Portal

Utilizing fiber reinforced plastic (FRP) reinforcement for concrete guideway structures in a superconductive magnetically levitated train system is desirable because FRP reinforcement is diamagnetic. For the design of guideway structures using FRP reinforcement, performance of structural reinforced concrete (RC) and prestressed concrete (PC) members must be understood. Flexural behavior of these members can be predicted by conventional design procedures, taking the mechanical properties of FRP reinforcement into account. However, shear-resisting behavior of RC and PC members has not yet been clarified, for the following reasons. 1. Unlike flexural behavior, shear-resisting behavior is complicated. 2. An experimental equation for shear capacity of RC members using reinforcing steel does not appear to be applicable, since such mechanical properties as Young's modulus and elongation are different from those of reinforcing steel. Under these circumstances, the authors carried out a basic experiment on shear capacity of rectangular beams using FRP tendons and FRP shear reinforcement. As a result, the following factors are elucidated. 1. Shear capacity of RC beams without shear reinforcement can be predicted to some degree by taking into account the tension stiffness of FRP reinforcement. 2. It seems possible to predict contribution of prestress to shear capacity from decompression moment. 3. Contribution of FRP shear reinforcement to shear capacity is smaller than the value calculated by truss analogy. The reasons seem to be related to experimental results showing that the maximum strain value of FRP shear reinforcement at shear failure is smaller than the elongation of FRP reinforcement.

The Vancouver (B.C.) Advanced Light Rapid Transit System (ALRT) has been selected as an example of a comprehensive transportation construction project where Quality Assurance played a major role. The primary aspects of a Q.A. philosophy, and its interrelationships with other design and construction requirements, are summarized. Discussion of the methodology of Q.A. for the ALRT links these conceptual ideas to the actual design and construction of the guideway system. The precast concrete beam manufacturing process, and the interfacing of Quality Control and Quality Assurance functions during beam manufacture, provide examples of a systematic approach to review, monitoring and recording all significant factors. The paper concludes with reference to the need for appropriate allocation of responsibility to attain desired results, and the delegation of the necessary authority to achieve those results.

Three f u l l -s c a l e , precast, prestressed doub le-tee girders measuring 80 ft (24.4 m) long by 5 ft (1.5 m) deep by 12 ft (3.7 m) wide were con-stru cted. One girder was used to monitor long-term deformations under site conditions. Two girders were tested to demonstrate the adequacy of the girder design, to check construction and reinforcement details, and to verify fatigue performance. Static tests of uncracked and deliberately precracked girders showed that torsional rotations due to service loads were in close agreement with the analysis and were smal 1 enough to ensure rider comfort. Fatigue resis-tance of the girders was verified using two separate test spectra involving 5- and 6-million cycles of loading. The loading represented the cumulative fati gue damage of sixty years of operational llife . Over load tests of the girders showed adequate strength and ductility . A strength of at least 1.6 times the required factored severe derailment load including 100% impact was obtained. The excellent behavior of the girders from serviceability and strength viewpoints substantiated the design methods and construction details used.

In 1985 Metropolitan Dade County, Florida, completed its first stage of Metrorail. This 22.5 miles of rapid transit system includes 21.5 miles of aerial guideways . The standard aerial structures used for the guideways are prestressed concrete doubletee girders, each 80 feet long, 12 feet wide, 5 feet deep, and weighing 94 tons. The double-tee design concept was the first of such a structure to be used in a U.S. transit system. It was recommended for reasons of aesthetics as well as economy. As compared to the traditional box sections, the double-tee girders were estimated to have resulted in savings of up to $10 million. Extensive technical studies were conducted to examine the various aspects of design and performance of thee structure. including the testing of two 2/3-scale models and three full scale cale girders. . Special attention has been given to shear and torsional design, since large torsional moments were produced by wind load on vehicles and structures , b y the horizontal nosing /lurching action of the vehicles, and by the centrifugal forces on curved tracks. Vlosov's elastic torsion analysis has been made which considers both the St. Venant tosrsion and the warping torsion. This is the theory that accurately predicted the behavior of the girders before cracking. Based on this theory, torsional rotatoin at service load stage was controlled to provide riding comfort for the passengers. Vlasov's theory based on uncracked section was found to be very uneconomical for the design of shear and torsional reinforcement. Considerable savings were achieved by extending Vlasov's theory to the post-cracking ultimate loads stage using a reduced torsional characteristic number. Recommended design value fork is 30% of the torsional characteristic number for an uncracked beam.

This paper describes the manufacture of 1040 prestressed concrete trapezoidal box girder guideway beams for the 14.8 km long dual-lane aerial guideway for the Vancouver Advanced Light Rapid Transit Project. The guideway beams are up to 36 m in length and weigh up to 100 t. In order to achieve the extremely tight tolerances dictatedbythe direct fixation ofrunning and linear induction motor railstotheprecastbeams, a sophisticated forming system was utilized to produce b ea ms with continuously varying vertical and horizontal alignment and super-elevation. Ahigh-precision jigging system was developed to cast in threaded inserts for attachment of the track hardware, and a thorough quality control program for dimensional and material control was instituted to ensure compliance with the construction specifications. Thedesignofthe first pumped concrete placing system to be used in a North American precast plant is described, as well as details of the plant layout, movable shelters, hoisting equipment and steam curing system utilized. Stripping, storageandtransportationoftheserrassivebeamstothe siteovercity streets at night is described. Details of the plant and field post-tensioning operations which were included inthebeamsupplycantract are also provided.