International Concrete Abstracts Portal

ACI 437 provides requirements for the performance of large scale structural load tests. These include mapping and monitoring cracks, shoring, and actual application of the load in a minimum of four separate increments. Any walls or other improvements that might provide support to the element being evaluated must be cut free. Deflection is to be monitored and load deflection curves prepared for each increment, and the full load is to remain in place for a minimum of 24 hours. Straightforward as these requirements appear, they can present a daunting task for those actually conducting the test. Where reaction is available for simple tests such as for beams and girders, either hydraulic jacks or pneumatic bags can be used to supply the load. Where large horizontal areas such as floors are involved, such simplicity is often not possible and some form of physical mass must be used. In areas that are open, the load can be applied with a crane, but on the interior of structures it must often be applied by hand or with the aid of small handling equipment, which severely limits the choice of load media. Whereas load tests are usually designed by structural engineers, the actual application is performed by construction workers. In order to assure optimal performance, it is imperative that both work together during the design as well as the application. The schedule and logistics of the loading operation must be well thought out prior to the actual work. Obviously, safety of the overall operation must be assured. Consideration must be given to not only the potential failure of the element being evaluated, but damage to other portions of the structure as well. This can include overloading of other elements during movement and handling of the load media, or damage by flooding where water is used. The logistics of load tests are discussed in detail, including preloading surveys and documentation, provision of shoring and other required preparation of the test area, selection of the load media and its application, and the required monitoring and control.

Wacker Drive in Chicago is a double-deck viaduct constructed along the Chicago River. Because of severe moisture-driven deterioration, the section of the elevated road between Randolph Street and Michigan Avenue are being reconstructed using a post-tensioned slab produced of high-performance concrete topped with a replaceable latex-modified concrete overlay. In order to verify the adequacy of the road way design, a full scale prototype was built and a test program was executed to evaluate the structural performance of the superstructure and its elements. Specifically, the following structural performance characteristics were evaluated: Positive and negative flexural strength Shear strength Live load stress range in concrete and post tensioning tendons Cracking at service load, overload and ultimate load Deflection at service load, overload and ultimate load Overlay bond strength and interaction between overlay and substrate Dynamic response This paper describes the prototype construction, analysis and testing.

This paper presents the results of an investigation on the fatigue performance of two full-size pre-cracked prestressed concrete bridge girders. One AASHTO Type III girder and one AASHTO Type V girder were tested under 1,000,000 cycles of repeated service load intermingled with 2,500 cycles of repeated overload. The behavior of the girders was monitored after each 200,000 cycles of service load as well as each 500 cycles of overload. At the end of the fatigue tests, the girders were tested to failure to determine their ultimate strengths. The test results demonstrated that the fatigue loadings had virtually no effect on the girder behavior. The girders showed no degradation in stiffness or strength after 1,002,500 cycles of fatigue loading. Both girders showed considerable ductility, and their ultimate loads and maximum deflections exceeded the predicted values.

The pier supporting Canada Place Cruise Terminal in Vancouver, British Columbia was constructed in the 1920s. Repairs and upgrading of the reinforced concrete structure were completed in the early 1980s for the 1986 World Expo, to provide hotel and convention centre facilities and a terminal for cruise ships. Since 2000, the Port of Vancouver has undertaken major renovations and expansion to increase the capacity of the facility and meet demands of the expanding cruise ship market. The extension to the existing pier added a third berth and provided additional passenger handling facilities. The expansion required the aprons of the original deck to carry wheel and outrigger pad loads in excess of load ratings previously in use. In the absence of detailed drawings, design data and material specifications to allow assessmetn of the load carrying capacity of the original structure, full scale structural load tests were performed in accordance with Canadian Standards Association CAN/CSA-A23.3 procedures. All thirteen tests were successful, confirming adequacy of the structure to carry the new loads. This paper presents the structural parameters, methodology and results of the test load programme.

A unique large-scale testing apparatus has been designed and built to facilitate the stressing and testing of 18.3 m lengths of steel prestressing strand. The strands are tested in a draped configuration to simulate the load and boundary conditions typical of an unbonded monostrand tendon in a post-tensioned concrete slab. Individual wires can be cut to simulate the occurrence of wire breaks due to corrosion. The apparatus consists of a steel wide flange beam with a parabolic profile plate that aligns the tendon in a draped configuration while providing access along the entire length for strain gauges. The overall length was selected, using mechanical models presented elsewhere, so that complete strain recovery could be observed in a wire with a break at the tendon mid-length. Other geometric variables were set to mimic the typical drape-to-span ratio of an unbonded monostrand tendon in a post-tensioned slab. Test results for intact 7-wire monostrand tendons correspond well to those predicted using the mathematical model of Machida and Durelli. Standard errors of 220 N and 133 microstrain were determined for the tendon load and wire strains, respectively. Thus, the apparatus can be used to accurately measure the mechanical response of unbonded 7-wire tendons.