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OCR for page 49
49 5. The bases of shear design provisions include experi- time to revise code specifications. Process 12-50 devel- mental test data, the equilibrium condition of members oped some of the structure for creating this archive, but in the ultimate limit state, and comprehensive behav- additional coordination and efforts are required. An ioral models for capacity. example of an experimental test archive being devel- oped by the earthquake engineering community as part of a large new initiative by the National Sciences Foun- 4.2 RECOMMENDED RESEARCH dation is available at http://nees.org 3. Because provisions principally are validated by test Several significant shortcomings in shear design practice data, shear tests are needed on the types of members were presented above. Of particular concern are the large dif- built with provisions but for which there is little or no ferences between codes of practice in the required amount of test data. This missing population principally consists shear reinforcement, the maximum allowable shear design of large members, continuous members, members sup- stress, minimum shear reinforcement requirements and how porting distributed loads, and members that fail in the depth effect in shear is addressed. Equally important are regions other than adjacent to a support. the lack of experimental validation for practical design cases 4. Where testing of members is not practical, suitable and the lack of understanding and consensus on how struc- numerical approaches should be used to obtain the best tural concrete members carry shear. To address these con- possible estimates of shear capacity and behavior. cerns, the following research efforts are recommended. 5. Standards for shear testing should be developed so as to ensure that material test data and the detailed struc- 1. Process 12-50 should be populated with the range and tural Response 2000 are measured in such ways that frequency of members commonly designed using the they can enable the evaluation of structures under AASHTO Bridge Design Specifications. This will service load levels, as well as ultimate load levels, and enable a much more accurate assessment of the effect the validation of numerical methods and behavioral of proposed changes to the specifications on the safety models for analyzing Response 2000. and economy of the nation's current and future inven- 6. Although the depth effect in shear has been well tory of bridge structures. demonstrated, the range of applicability of this effect 2. A web-based national database of shear test results and its relation to minimum shear reinforcement should be established. This can be used by researchers requirements needs to be better understood. It is likely and funding agencies to understand where research that depth rather than concrete compressive strength is is most needed. It will also ensure that the resources a better parameter for establishing minimum shear rein- spent in conducting experiments are used when it is forcement requirements.