International Concrete Abstracts Portal

The deformability of reinforced concrete walls with staggered lap splices was studied through tests of six cantilevered walls under constant axial load and cyclic reversals of lateral displacement. The height-to-length aspect ratios of the walls were approximately 3.2. Four walls had staggered laps, one wall had non-staggered laps, and one wall had mechanical couplers. Laps were detailed to yield the spliced reinforcement. Test walls with staggered laps lost lateral-load resistance at smaller drift ratios (1.0% to 2.1%) than both the test wall with non-staggered laps (2.3%) and the test wall with mechanical couplers (3.5%). Staggered lap splices resulted in larger strain concentrations than non-staggered lap splices. It was concluded that both staggered and non-staggered lap splices a) can have reduced strain capacity relative to continuous bars (leading to bond failure before or after yield) and b) alter inelastic strain distributions, causing large reductions in effective plastic hinge length.

It can be demonstrated that performance-based seismic design of post-installed anchors in accordance with ACI 318 is not possible by using the anchor qualification information provided by ACI 355. The current state-of-the-art anchor qualification does not provide capacities that reflect actual earthquake responses in seismic design scenarios. This paper provides a comprehensive analysis and highlights the gaps in the current approach. A performance-based framework is proposed as the basis of future developments in seismic design and qualification of post-installed anchors. It is demonstrated that the approach is fully transparent and provides the possibility to identify key driving parameters that need further experimental investigation. The approach acknowledges that performance-based seismic design of post-installed anchors needs an understanding of the seismic damage of the concrete-anchor system. Currently, no design tools are available to predict this damage. The proposed framework adopts the theory of the accumulated damage potential (ADP) as a damage parameter. It is demonstrated that the selected damage parameter is simple but meaningful enough to represent the seismic damage of the concrete-anchor system at the design level. Possibilities for future development of the approach is explored, and directions for the next steps are suggested. It is highlighted that a definition of a framework for realistic seismic performance objectives of post-installed anchors is needed for the development of design tools in the future. The proposed framework has great practical significance and may help fill a gap in the seismic design of post-installed anchors. Promoting a transparent framework that is driven by the needs of performance-based seismic design may help develop a feasible qualification system and replace the currently used pass-or-fail assessment approach that is not suitable to provide anchor capacities for performance-based seismic design.

The paper presents a comparative study on the seismic behavior of circular columns reinforced with glass fiber-reinforced polymer (GFRP) and steel. The study specifically investigates the influence of replacing steel bars with GFRP bars on columns’ seismic response. All the studies summarized in this article were conducted at the University of Toronto. Results from the tests of 24 columns (all having 356 mm diameter and tested in a similar manner) from three different studies are closely analyzed to compare their responses. Based on the experimental results, it is found that replacing steel spirals with GFRP spirals did not result in substantial variation in the seismic performance of columns. Both types demonstrated similar ductility parameters and drift ratios when similar amounts of spirals were used at comparable pitches. Likewise, columns with steel longitudinal reinforcement and GFRP longitudinal reinforcement achieved similar displacement ductility, energy dissipation, and drift ratio.

Filling reinforced concrete (RC) frame spans with RC shear walls constitutes a strategic intervention to existing sub-standard buildings. The efficiency of this intervention depends, among other things, on the behavior of interfaces between the shear wall and the frame elements. The failure of critical interfaces that may lead to undesirable shear sliding of the wall at its base can only be prevented if the interfaces are adequately designed. To investigate the cyclic behavior of interfaces within the composite frame-to-wall members, four frames filled with RC walls, as well as two reference specimens (i.e., a bare frame and a monolithic frame/wall specimen), were subjected to cyclic horizontal displacements. The crucial effect of the interface reinforcement ratio, the detailing, the dowel distribution along the interface, and the embedment length on the behavior of the specimens, in terms of maximum capacity, drift, and failure mode, was confirmed.

In performance-based seismic design, buckling and fracture of longitudinal steel in reinforced concrete columns are damage limit states that may be considered for damage control and near collapse, respectively. This study evaluates the progression of buckling instability, which eventually leads to bar fracture, based on bending strains measured in buckled bars of cyclic quasi-static column tests. Buckling-induced bending strains are calculated with bare bar fiber models and experimental buckled shapes of longitudinal reinforcement in the column data set. This study proposes an empirical equation that calculates the buckling-induced bending strain based on column displacement ductility, low-cycle fatigue, and column design parameters for grade 60 steel. This study also identifies the buckling-induced bending strains that trigger transverse steel yielding, visual bar buckling, and brittle bar fracture.