Important Aspects of Executing Large Scale Load Tests


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Title: Important Aspects of Executing Large Scale Load Tests

Author(s): J. Warner

Publication: Special Publication

Volume: 211


Appears on pages(s): 343-368

Keywords: deflection; deflection monitoring; load media; load tests; shoring

Date: 2/1/2003

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.