Effects of anchor wedge dimensional parameters on posttensioning strand performance

Abstract

A lthough unbonded posttensioning for use in gravity load systems (for example, floor and roof slabs) has been available in the United States since the 1950s and standards exist for its application, 1-4 this construction method is increasingly being considered and applied in more extreme loading environments, such as in primary earthquake-resisting structural components (for example, primary shear walls and moment-resisting frames). Recent advances in the seismic application of unbonded posttensioning include precast concrete buildings, steel buildings, and bridge systems. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] The posttensioning tendon anchorages in unbonded posttensioned building and bridge systems are important structural components because of the transfer of the entire posttensioning force at these locations. Posttensioning anchorage designs, configurations, manufacturing processes, and materials have significantly changed since the initial research that led to their development. [25][26][27][28][29] All of this early work focused on structures under gravity loads, with no consideration for extreme loads such as earthquakes. As a potential limitation for seismic applications, premature strand wire fractures were observed by Weldon and Kurama 30 during reversed-cyclic lateral load testing of unbonded posttensioned precast concrete coupled wall subassembly specimens. Subsequently, a detailed experimental study on the ultimate performance of industry-■ This paper reports on an experimental investigation of the effects of anchor wedge dimensions on the ultimate strains of posttensioning strand.■ The results demonstrate that slight increases in the taper angle of the anchor wedge outer surface and the thickness of the anchor wedge can significantly improve the ultimate performance of the strand at failure.

Load Carrying and Hydrostatic Performances of Innovative Encapsulated Anchorage System for Unbonded Single Strand

“…Kwon et al [1] proposed an anchorage device with lateral reinforcement to resist bursting stress and developed a modified equation of bearing capacity based on their experimental and analytical results. Walsh et al [2] showed that posttensioning of the anchor or wedges plays a significant role in anchorage performance by controlling the stress transfer from the tendon to the anchor and, based on experimental results, proposed wedge details that can improve performance. Kim et al [3] investigated the effects of steel fiber and steel reinforcements on the ultimate bearing strength of the local anchorage zone and compared the results of the experimental results with the design equation.…”

Experimental investigation of a low‐prestressed self‐centering energy dissipative brace

“…The configuration shown in Figure 3(A) adopts a high‐strength, rod‐chuck ratchet component. The details of the ratchet component are shown in Figure 3(B), which consisted of the left plate, middle plate, four high‐strength rods (HSRs), eight nuts, and four “chucks.” Each “chuck” consists of commercially available anchorage hardware used to anchor pretensioned strands during fabrication, 32 The left end of the four HSRs was anchored to the left plate using eight nuts, to enable the connection to resist compression or tension. Their right ends went through the four chucks, which were welded to the right side of the middle plate, and could slide through the plate when the rod was in compression.…”

Seismic-Resistant Precast Concrete Structures: State of the Art

“…To prevent this behavior, the studies have recommended maximum allowable strand strains for use in the design of jointed precast structures. Walsh et al (2015) showed that higherperforming PT anchors that allow greater strand strains without fracture can be achieved by slightly changing the anchor wedge geometry.…”