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Lap splicing of longitudinal reinforcing bars in shear walls is often encountered in practice, and the transfer of forces in lap-spliced reinforcing bars to the surrounding concrete depends on the bond strength. Buildings with shear walls during an earthquake develop plastic hinges in the shear walls, particularly where the reinforcing bars are lap-spliced. Brittle failure is commonly observed in reinforcing bar lap-spliced shear walls, which needs to be minimized by choosing the appropriate percentage of lap-spliced reinforcing bars. Therefore, it is essential to address the detailing of the lap-spliced regions of reinforced concrete (RC) shear walls. Several seismic design codes provide guidelines on lap-spliced detailing in shear walls related to its location, length of lap-splice, confinement reinforcement, and percentage of reinforcing bars to be lap-spliced. In this study, the percentage of reinforcing bars to be lap-spliced at a section is examined with staggered lap-splicing of 100, 50, and 33% of longitudinal reinforcing bars, in addition to a control RC shear wall without lap-splicing. This study tested four half-scale RC shear walls with boundary element (BE), designed as per IS 13920 and ACI 318, under quasi-static reversed cyclic loading. From the experimental study, it is observed that the staggered lap splicing of reinforcing bars nominally reduces the performance of shear walls under cyclic load in terms of the reduced flexural strength, deformation capacity, energy dissipation, and ductility of the shear walls compared to the control shear wall without lap splicing. It is also observed that the unspliced reinforcing bars do not sustain the cyclic loading in staggered lap-splice after the post-peak. Current provisions of ACI 318, EC2, and IS 13920 recommend staggered lap-splice detailing in shear walls. However, from the current study, shear walls with different percentages of staggered lap splice show that the staggered lap-splice detailing in shear walls does not improve its seismic performance.

This paper investigates the seismic performance of exterior beam-column joints in special moment frames (SMFs) with varying axial load ratios. Cyclic testing of four additional specimens with an axial load ratio of 0.45 is compared with four companion specimens at 0.10. Each specimen was designed and constructed with Gr.60 (420), Gr.80 (550), or Gr. 100 (690) reinforcement in accordance with ACI CODE-318 provisions for special moment frame joints, except for the provisions of joint shear and confinement. While ACI CODE-318 tightens confinement requirements for SMF columns and joints, especially under high axial loads, this study reveals that increasing the axial load ratio benefits joint behavior. The study also demonstrates the feasibility of using high-strength reinforcement in exterior beam-column joints of SMFs, provided that appropriate modifications are made. The findings in this study have influenced modifications from ACI CODE-318 to the Building Code Requirements for Concrete Structures in Taiwan.

To secure emulative seismic performances of precast concrete (PC) special moment frame buildings, two capacity-based connection design options (that is, strong and ductile precast connections) are provided in the current version of ACI 318. However, the evolving performance-based seismic design and response evaluation requires a reasonable estimation of the energy dissipation and corresponding hysteresis damping characteristics so that their potential performance level can be properly predicted. Therefore, this study focuses on the seismic performances, especially the energy dissipation and damping performances of the Code- compliant PC wide beam-column connections. Three PC wide beam-column connection specimens under the ductile connection design principle with different joint details and a reinforced concrete (RC) control specimen were fabricated and tested under reversed cyclic loadings. In addition, an energy-based macro-modeling method was developed to characterize the cyclic responses, including the damping response of PC wide beam-column connections. The test results revealed that the Code-required overstrength of shear-friction strength between PC beam members and cast-in-place (CIP) concrete is crucial to achieving the ductile performance of precast connections. It also appeared that the energy-based macro-modeling method could capture the hysteresis features through the relationship between the equivalent viscous damping (EVD) ratio and the ductility capacity of PC wide beam-column connections.

The first edition of ACI CODE-440.11 was published in September 2022, where some code provisions were either based on limited research or only analytically developed. Therefore, some code provisions, notably shear and development length in footings, are difficult to implement. This study, through a design example, aims at a better understanding of the implications of code provisions in ACI CODE-440.11-22 and compares them with ones in CSA S806-12, thereby highlighting a need for reconsiderations. An example of the footing originally designed with steel reinforcement was taken from the ACI Reinforced Concrete Design Handbook and redesigned with GFRP reinforcement as per ACI CODE- 440.11-22 and CSA S806-12. A footing designed as per ACI CODE- 440.11-22 requires a thicker concrete cross section to satisfy shear requirements; however, when designed as per CSA S806-12, the required thickness becomes closer to that of the steel-reinforced concrete (RC) footing. The development length required for a glass fiber-reinforced polymer-reinforced concrete (GFRP-RC) cross section designed as per ACI CODE-440.11-22 was 13% and 92% greater than that designed as per CSA S806-12 and ACI 318-19, respectively. Also, the reinforcement area required to meet detailing requirements is 170% higher than that for steel-RC cross section. Based on the outcomes of this study, there appears to be a need for reconsideration of some code provisions in ACI CODE-440.11-22 to make GFRP reinforcement a viable option for RC members.

The ACI 318-19 Building Code does not allow the use of headed bars larger than No. 11 (No. 36) due to insufficient experimental data. Thirty large-scale simulated beam-column joint specimens containing high-strength No. 11 (No. 36), No. 14 (No. 43), or No. 18 (No. 57) headed bars were tested to investigate the effects on anchorage strength of key factors, including bar stress at failure, bar size, bar spacing, embedment length, transverse reinforcement, concrete compressive strength, and loading condition. Specimens exhibited concrete breakout, side splitting, or a combination, with four exhibiting a shear-like failure. Anchorage of larger bars is noticeably influenced by joint shear demand and loading conditions. Descriptive equations developed based on 164 tests, accurately characterize anchorage strength for headed bars up to No. 18 (No. 57). They indicate that anchorage strength is proportional to concrete compressive strength to a power close to 0.2 and that the contribution of parallel ties for large headed bars is lower than that observed for smaller headed bars.