Lap Splice Strength Research Articles

On estimating the drift capacity of reinforced concrete walls with lap splices at their bases

AbstractFailures in reinforced concrete (RC) structural walls have been reported to occur at longitudinal lap splices in earthquakes as far back as 1964 (Kunze et al. in JP 62:635–650, 1965) and as recently as 2023 (Pujol et al. in ES 63:777, 2024). Design codes such as ACI318-19 (2019) and JSCE Standard Specification for Concrete Structures (2007) have been adjusted accordingly and have banned the placement of lap splices near sections where longitudinal reinforcement is expected to yield in reinforced concrete structural walls. But minimizing lap splice vulnerabilities in new construction does not address existing buildings that may be vulnerable to earthquakes because of lap splices placed at or near critical sections. A simple, rapid assessment technique should be adopted to address the large number of existing buildings with potentially vulnerable RC walls. To investigate the deformation capacity of structural walls with lap splices near sections where longitudinal reinforcement yields, a two-part experimental program is ongoing: four large-scale walls with non-staggered lap splices were tested at Purdue University (Pollalis Drift capacity of reinforced concrete walls with lap splices, Purdue University: West Lafayette, 2021) and two large-scale walls with staggered lap splices have been tested at the University of Canterbury (Kerby et al. Experimental study of staggered lap splices in RC structural walls, 2023). Results from these six tests are added to a dataset of 15 previous tests of walls with non-staggered lap splices compiled by Almeida et al. (JSE 143:853, 2017). A method to estimate drift capacity of walls with lap splices is proposed based on estimates of lap splice strength, steel stress–strain relationships, and moment-area theorems. Two sets of assumptions can be used to produce estimates of drift capacity. The first set of assumptions applies when detailed information of reinforcement stress–strain relationships is available, and the second set of assumptions applies when reinforcement stress–strain relationships must be assumed. Both sets of assumptions produce reasonable estimates of the drift capacity of walls with lap splices, and the second set of assumptions can be used for rapid assessment given minimal information about the detailing and material properties of a wall.

Diagonal tensile strength and lap splice behavior of concrete masonry assemblies with lightweight grout

Lightweight (LW) grout is not yet permitted per the TMS 402/602–16 masonry design code as only limited testing has been done to characterize the difference in its behavior from normal weight (NW) grout. This paper presents an experimental investigation carried out as a part of a pilot project directed in comparing the performance of LW grout with NW grout by completing diagonal tensile strength tests and lap splice tests. For the diagonal tensile strength tests, three types of wall panels, each fully grouted with either expanded clay (EC) grout, expanded slate (ES) grout or NW grout, are constructed, and tested in accordance with ASTM E519. The results of the dataset are compared to the predicted diagonal tensile strength for a NW specimen using equations from TMS 402/602–16. For the lap splice test, two lap splice configurations are tested using masonry assemblies constructed with EC and ES grout. Regression analysis is used to compare this dataset to historical data of lap splice specimens with NW grout. For both the diagonal tension tests and the lap splice tests, results are compared to other NW masonry testing in the literature, if available. Additionally, parallels are drawn between the relative performance of masonry assemblies grouted with LW and NW grout and the relative performance of LW versus NW concrete specimens from the literature. The results of this study indicate that a reduction (λ) factor in the design value of diagonal tensile strength and lap splice strength for masonry assemblies with LW grout is merited, analogous to reduction factors for these properties in LW concrete.

압축을 받는 고강도 D22 철근 겹침이음의 이음강도 상한

압축을 받는 고강도 D22 철근 겹침이음의 이음강도 상한

Experimental investigation on the deformation capacity of lap splices under cyclic loading

Correct detailing and positioning of lap splices is essential in order to prevent premature failure of reinforced concrete structural members. Especially before the introduction of capacity design guidelines, lap splices were often placed in member regions that undergo inelastic deformations under earthquake loading. When assessing the seismic performance of such members, not only the lap splice strength, which was assessed in previous studies, but also information on the deformation capacity of lap splices is required. This paper analyses the results of a recently concluded experimental programme on spliced RC wall boundary elements tested under uniaxial tension–compression cyclic loading. The study aimed at investigating the influence of lap splice length, confining reinforcement and loading history on the deformation capacity of lap splices. The latter is defined as the average strain, at the onset of splice failure, ascribed to deformations originating from the lap splice zone. Analysis of the test results showed that the deformation capacity of lap splices: (1) increases with lap splice length; (2) increases with confining reinforcement but the effectiveness of the confining reinforcement is dependent on the lap splice length; (3) decreases with larger imposed compression levels; (4) is larger for bottom-casted with respect to top-casted lap splices. Finally, an empirical model is proposed to estimate the strain capacity of lap splices, which provides a good fit with the experimental results.

Effect of Preexisting Cracks on Lap Splice Strength of Reinforcing Bars

Effect of Preexisting Cracks on Lap Splice Strength of Reinforcing Bars

Response of lap splice of reinforcing bars confined by FRP wrapping: modeling approach

This paper presents a tri-uniform bond stress model for predicting the lap splice strength of reinforcing bar at the critical bond splitting failure. The proposed bond distribution model consists of three zones, namely, splitting zone, post-splitting zone and yielding zone. In each zone, the bond stress is assumed to be constant. The models for bond strength in each zone are adopted from previous studies. Combining the equilibrium, strain-slip relation and the bond strength model in each zone, the steel stress- slip model can be derived, which can be used in the nonlinear frame analysis of the column. The proposed model is applied to derive explicit equations for predicting the strength of the lap splice strengthened by fiber reinforced polymer (FRP) in both elastic and post-yield ranges. For design purpose, a procedure to calculate the required FRP thickness and the number of FRP sheets is also presented. A parametric investigation was conducted to study the relation between lap splice strength and lap splice length, number and thickness of FRP sheets and the ratio of concrete cover to bar diameter. The study shows that the lap splice strength can be enhanced by increasing one of these parameters: lap splice length, number or thickness of FRP sheets and concrete cover to bar diameter ratio. Verification of the model has been conducted using experimental data available in literature.

보강 섬유 종류에 따른 고인성 시멘트 복합체내에서 철근의 겹침 이음 성능

초록·키워드 목차 오류제보하기 등록된 정보가 없습니다. ABSTRACT1. 서론2. 실험3. 철근의 겹침이음 실험 결과4. 결론참고문헌요약

Size effect on bond strength of deformed bars

The size-effect on bond strength between deformed bars and concrete is investigated using pullout and lap splice tests. The specimen parameters include bar diameter (up to 52 mm), rib shape, cover thickness, and the presence/absence of confining reinforcement. The experimental results show that: (1) pullout specimens with the smallest cover thickness exhibit the largest size-effect; (2) larger confinement by either cover concrete or steel reinforcement results in smaller size-effect, and; (3) the size-effect is mainly attributable to brittle splitting cracks, and not to local crushing of concrete in front of the bar ribs. Prevailing design equations for lap splice strength are modified to better account for the size-effects observed in the experiments. The equations yield a large size-effect for splices with small cover and short splice length, where brittle failure is expected. On the other hand, the equations yield a small size-effect for splices with low rib-height bars and many stirrups, where ductile failure is expected. The proposed equations agree with both the experimental results presented in this study and the bulk of the experimental data reported in the literature.

Stirrup distribution across the beam width in tension lap splices

The influence of the distribution of transverse confining steel on the strength of tension lap splices was investigated experimentally in this study. Beam specimens contained three lap-spliced No. 35 bars placed in one layer. Either two or three stirrup legs were placed across the beam width to provide splitting confinement. Both configurations were designed to provide similar stirrup resistances for intercepting horizontal bond splitting. The effectiveness of the different stirrup configurations was compared by investigating the performance of beams subjected to static, fatigue, and fully reversed inelastic loading. Twenty-three full-size beam specimens were tested with the lap splice placed symmetrically within a maximum moment, zero-shear region. Specimens were constructed and tested in six different series (concrete batches). Within each series, the total bond resistance, as evaluated on the basis of CSA A23.3-94, was similar even though the lateral distribution of transverse steel was varied. Nine specimens were tested under monotonically increasing (static) loading to failure, six specimens were subjected to fatigue load cycling between 25% and 75% of their ultimate static strength, and eight specimens were subjected to fully reversed inelastic load cycling. Test results for six similar specimens from a previous study were also included in the current investigation analysis. Test results indicated that using three vertical stirrup legs across the beam width to provide a more uniform distribution of stirrup confinement significantly enhances post yield ductility under fully reversed inelastic load cycling. Meanwhile, specimens tested under static loading showed that CSA A23.3-94 provisions provide a consistent and conservative prediction of lap-splice strength for the specimen configurations investigated, regardless of the distribution of stirrup confinement across the beam width. Finally, the performance of fatigue specimens indicated a slight improvement with the use of the three-leg stirrup configuration. However, this result does not agree with previous observations made at the same institution where it was suggested that stirrup confinement intercepting vertical splitting plays a more significant role in defining fatigue resistance.Key words: reinforced concrete, bond, confinement, lap splices, stirrups, static loading, fatigue load cycling, inelastic load reversal.