Strength and Behavior of Unconfined Noncontact Hooked Bar Lap Splices

Abstract

Hooked bars are commonly used in lap splices to connect precast concrete elements to reduce required splice lengths; however, practically, no tests of large hooked bars in such elements have been conducted. To address this knowledge gap, 29 beam specimens containing unconfined noncontact hooked bar lap splices were tested under four-point bending. The beams were designed to examine the influence of splice length, hook shape, bar diameter, splice spacing, concrete compressive strength, and cover on splice strength (i.e., achievable splice stress). Splice strengths were determined using moment–curvature analysis and used in parametric analyses to understand the influence of each anchorage parameter on splice strength. The test results were used to rationalize the resistance mechanism of unconfined hooked bar lap splices, showing that force is developed through a three-dimensional load path consisting of diagonal compression struts equilibrated by concrete tension ties. By comparing the developed stresses with a descriptive equation for straight bar lap splices and the hooked bar development length design equation, it was determined that hooked bars are an effective detail to reduce splice lengths. However, the hooked bar development length equation is ineffective in determining required splice lengths. Unconfined hooked bar lap splices developed 35%–48% more force than similar unconfined straight bar splices, justifying the use of hooked splices to achieve shorter connection widths in accelerated bridge construction. Increases in splice length, concrete compressive strength, and cover resulted in increased splice strength. However, increases in bar diameter and splice spacing reduced splice strength.