Browsing by Subject "Anchorage (Structural engineering)"
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Item The anchorage behavior of headed reinforcement in CCT nodes and lap splices(2002) Thompson, Keith; Jirsa, J. O. (James Otis)The behavior of headed reinforcement in concrete was studied using full scale tests of CCT nodes and lap splices. The mechanics of the anchorage behavior were observed and recorded to evaluate the manner in which the capacity of a headed bar is developed. The measured data were used to evaluate existing models of headed reinforcement anchorage as well as the ultimate limit state for anchored bars in CCT nodes. Observations from the CCT node tests provided information on the stages of truss development in a simple strut-and-tie model as well as the stress state of the concrete in the node and adjacent struts. Observations from the lap splice tests provided information on the mechanism of stress transfer between lapped bars. The results indicate that strut-and-tie modeling can be successfully applied to understand the behavior of non-contact lap splices and is necessary in determining the anchorage length of lapped bars. Observations of headed bar anchorage have shown that the final anchorage capacity consists of peak head bearing and reduced bond. A model for anchorage capacity was produced based on this concept. Finally, recommendations for structural concrete design using headed reinforcement were made.Item Anchorage of grouted vertical duct connections for precast bent caps(2005) Brenes, Francisco Javier; Wood, Sharon L.; Kreger, Michael E.In the last decade, the need to reduce traffic disruption at construction sites has led to innovations in bridge prefabrication. In Texas, most of these recent innovations have involved prefabrication of bent cap elements. Bent cap-tocolumn connections currently being used incorporate either corrugated galvanized steel or plastic ducts that are precast in the bent cap element to serve as sleeves to house connectors. Designers and contractors prefer this type of precast connection over other types because the volume of grout that is required to complete the capto-column connection is minimized. This research intends to reduce some of the uncertainties that currently surround the design of grouted vertical duct connections. The main test parameters that influence connection performance are identified. These parameters include bar coating, duct material, embedment depth, number of connectors, bar eccentricity, and transverse reinforcement. The experimental program examines the behavior and failure modes of grouted vertical duct connections. Results from thirty-two large-scale pullout tests are reported, and the effects of the studied parameters on connection behavior are evaluated. A simple phenomenological bond-slip model is presented that can be used to estimate the observed behavior. The development of the anchorage design provisions considers the stress in the connectors at service load levels. Design provisions are developed for connectors that experience: (1) compression or low tension, and (2) significant tension. Design provisions applicable to connectors that experience compression or low levels of tension are based on limiting serviceability stresses related to widespread splitting in the connection specimens. Connectors that experience significant tension and may be expected to yield are designed using anchorage provisions based on experimental average peak bond strengths. Observed pullout modes of failure are precluded by incorporating adequate levels of safety in the development of the design recommendations.