THE BEHAVIOR AND STRENGTH OF LAPPED SPLICES IN REINFORCED CONCRETE BEAMS SUBJECTED TO CYCLIC LOADING.

摘要

Presented are the results of the second phase of a continuing investigation of tensile lap splices in reinforced concrete beams being conducted at Cornell. Specimens were subjected to repeated and reversed cyclic loading into the inelastic range.;The experimental program consisted of a series of tests on full scale beam specimens which had either two ;Test results indicated that for loading in the inelastic range, the number of cycles and maximum strain level has a greater influence on splice performance than if load reversals are included in the loading sequence.;When splices are subjected to inelastic straining, progressive splitting along a splice length can lead to loss of anchorage and failure. Providing uniformly spaced stirrups along the splice length is essential if a member is to sustain a dozen or more load cycles up to twice the yield displacement (2-5 times the yield strain in the spliced reinforcement).;The principal aim of the investigation is two-fold: First, to evaluate the parameters that influence the strength of tensile lap splices. Second, to develop guidelines for the design of splices to resist seismic loading.;Moderate levels of shear ((LESSTHEQ) 250 psi) resulted in better splice performance in terms of both strength and ductility over identical splices in regions of constant moment. Because moments are not equal, penetration into the splice region is reduced resulting in superior performance.;The recommended spacing of stirrups along a splice of at least 30 bar diameters in length is:;(DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI).;for grade 60 main bars and stirrups, where d(,t) is the diameter of the stirrup, d(,b) is the diameter of the spliced bar and (,s) is the splice length. Modifications are indicated when main bars or stirrups are of different grades or more than two bars at a section are spliced. When a splice is subjected to shear, stirrup spacing may be increased by the following multiplicative factor:;(DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI).;where M is the higher moment at the splice ends and M(,y) is the section yield moment. A maximum spacing of 6" is suggested to insure splice ductility.