A large volume of test data has been evaluated to establish deformability of reinforced concrete beams, columns, and structural walls in the inelastic range. Experimentally observed deformation capacities of members, and their relationships with design parameters are presented. The paper is intended to demonstrate available ductilities in reinforced concrete structural members for use in earthquake resistant design.
Corrosion of reinforcing steel is a major cause of deterioration of reinforced concrete structures. Two primary causes leading to corrosion of reinforcing steel are, respectively, carbonation and chloride contamination of the concrete cover. Estimating the time to corrosion initiation through modeling enables a qualitative and quantitative assessment of the influence of several variables on the mechanism involved. However, many of these variables are subject to stochastic uncertainty, which can be represented through either frequentist or Bayesian probability. This paper proposes a probabilistic-based model for carbonation-induced corrosion based on a Bayesian belief network. The proposed model is compared with a more traditional probabilistic-based technique, Monte Carlo simulation. Both methodologies are illustrated through two case studies and similarities and differences are highlighted.
Shear is force applied parallel to, or in the plane of a cross section of a structural member. Shear stresses are typically computed across a section that is perpendicular to the member length. Therefore, shear forces used in structural design are often perpendicular (transverse) to member length. is provided for this article.
No abstract is provided for this article.
Large scale high-strength concrete columns were tested under simulated seismic loading. The columns had either a square or a circular cross-section with 104 MPa or 90 MPa concretes, respectively. The test parameters considered included the volumetric ratio, grade and arrangement of transverse reinforcement. The columns were subjected to constant axial compression and incrementally increasing lateral deformation reversals. The results are presented in the form moment-displacement hysteretic relationships and indicate that high-strength concrete columns can be confined to possess inelastic deformabilities usually expected of normal-strength concrete columns. However, high-strength concrete columns do require higher lateral pressure, provided either by increased volumetric ratio or higher grade of transverse reinforcement. The effectiveness of high-strength transverse reinforcement depends on the efficiency of confinement reinforcement and the level of axial compression. Circular columns and square columns with closely spaced transverse and longitudinal reinforcement show superior performance when high-strength steel is used to confine concrete. The use of higher grade transverse steel in these columns permit a reduction in the volumetric ratio, without reducing column deformability.
Experimental research was conducted to investigate the effectiveness of carbon fibre reinforced polymer (CFRP) jackets in retrofitting bridge columns with splice deficiencies. Full-size bridge columns were tested under simulated seismic loading. The columns were subjected to constant axial compression to simulate gravity loading, and incrementally increasing lateral deformation reversals to simulate seismic loading. The specimens represented typical bridge columns between the footing and the point of inflection. Tests of as-built columns were first conducted to assess their deformability in the inelastic range. The specimens included circular and square cross-sections with reinforcement arrangements that were representative of the majority of concrete columns in practice. The longitudinal reinforcement was spliced near the base. These columns had limited deformability and failed shortly after developing 1% lateral drift. Companion columns with identical properties were retrofitted with CFRP jackets and tested to investigate the effectiveness of the retrofit technique. The results indicated that CFRP jacketing was effective in circular columns in improving bond between reinforcement and concrete within the plastic hinge region. The lateral deformability of the circular column improved beyond 6% drift ratio. The CFRP jacket however was not as effective in the square column. The improvement observed in this column was limited to 2% lateral drift, beyond which there was a clear deterioration of the bond within the splice region, as evidenced by significant and rapid strength decay. For the covering abstract see ITRD E123557.
Abstract Bond is an essential property that guarantees the composite action in prestressed concrete (PC) members. This bond may be degraded due to different reasons, corrosion‐induced damage being one of the most frequent ones. The transfer length is the key indicator that describes the bond properties between prestressing steel and concrete. The analysis and design of PC members with prestressing wires require a realistic assessment of the bond transfer length. This paper presents an analytical study of the influence of the governing geometrical and mechanical variables on bond behavior in PC members undergoing steel corrosion. A model describing the deterioration of the transfer length due to corrosion, calibrated and verified through experimental tests, is proposed along with simplified expressions for the assessment of transfer lengths in PC members with corroded wires.
Performance of reinforced concrete frame buildings depends on seismic hazard of the region and vulnerability of the structure. Performance-based evaluation of buildings may be conducted through fragility curves developed for different levels of performance. Reinforced concrete frame buildings with 2, 5, and 10-stories, designed as moderately ductile buildings for Ottawa in Eastern Canada and fully ductile buildings for Vancouver in Western Canada were used to generate seismic fragility curves. The buildings were analyzed using PERFORM-3D software to assess seismic vulnerabilities. Incremental dynamic analysis was employed to generate fragility curves. Two sets of earthquake records compatible with uniform hazard spectra of 2010 NBCC were selected, where each set contained 20 records for each city. The fragility curves depict probabilities of exceedances for different damage states, and can be used for seismic vulnerability assessment of reinforced concrete frame buildings in Canada designed and built after 1985.
This study investigates corrosion-induced deterioration of bond between steel and concrete through finite element analysis (FEA) of the flexural behaviour of corroded reinforced concrete components. The impaired bond capacity is first studied analytically by treating the concrete cover as a thick-wall cylinder subjected to internal pressure. The bond mechanism is later formulated and implemented through link elements in the commercial software ABAQUS. Corrosion-induced damage is introduced in the FEA by reducing the reinforcement cross-sectional area, simulating the splitting of the concrete cover and decreasing the bond capacity with increasing levels of corrosion. The results of the numerical model show good agreement with published experimental observations.
Squat reinforced concrete (RC) shear walls are essential structural elements in low-rise buildings, valued for their high strength and stiffness. However, research on their seismic behavior remains limited, as most studies focus on tall, slender walls, which exhibit distinct failure mechanisms and deformation characteristics. This study addresses this gap by conducting an extensive review of existing research on the seismic performance of squat RC shear walls. Experimental studies, analytical models, and numerical simulations are examined to provide insights into key factors affecting wall behavior during seismic events, including material properties, wall geometry, reinforcement detailing, and loading conditions. The review aims to support safer design practices by identifying current knowledge gaps and offering guidance on areas needing further investigation. The findings are expected to aid researchers and practitioners in refining seismic design codes, ultimately contributing to the development of more resilient squat RC shear walls for earthquake-prone regions. This research underscores the importance of improving structural resilience to enhance the safety and durability of buildings.
Fiber reinforced polymer (FRP) reinforcement, in the form of longitudinal bars and transverse grids is currently being developed for use in new building and bridge structures. However, FRP reinforcement shows linear stress-strain characteristics up to failure, without any ductility. Experimental research is currently conducted at the Structures Laboratory of the University of Ottawa to investigate the seismic performance of FRP reinforced concrete structural elements. Large scale columns and beams are being tested under simulated seismic loading. The results of selected tests are summarized in this paper, with the assessment of their significance from seismic performance perspective. Specimens representing part of a first storey building column between a footing and the point of inflection; and the portion of a beam between a column and the point of inflection, were tested under lateral deformation reversals. The members were reinforced with carbon FRP bars in the longitudinal direction, and carbon FRP grids in the transverse direction. Both the columns and the beams sustained a minimum of 2% to 3% lateral drift ratios, meeting seismic drift limitations of most building codes. Test results indicate that FRP reinforced concrete elements exhibit reduced stiffness and softened response, when compared with conventional steel reinforced concrete elements, because of the lower elastic modulus of FRP bars. This may suggest reduced spectral values associated with longer vibration periods, as well as increased deformability, resulting in seismic resistant structures for which elastic design approach with sufficient deformability may be appropriate.
It has been observed during previous earthquakes that the damage to operational and functional components of buildings often result in more injuries, fatalities and property damage than those inflicted by structural damage. Operational and functional components of a building include architectural components, mechanical and electrical equipment, as well as building contents. A rational approach to designing these elements against seismic excitations involves the use of floor design spectra. The development of such design spectra for buildings in Canada constitutes the objective of the paper. This objective was achieved by conducting comprehensive analyses of selected reinforced concrete buildings, with different lateral force resisting systems and building heights, under code compatible earthquake records for an eastern and a western Canadian city. It was observed that the floor response was significantly amplified, especially for buildings with short periods. Generally, the higher floors showed higher amplifications with differences in spectra between the floors being more pronounced in low-rise buildings and shear wall buildings with short fundamental periods. The results provided a large volume of data to generate floor response spectra for the design of operational and functional components of buildings in Canada. The details of the approach and the design spectra are presented in the paper.
No abstract is provided for this article.
Bridges are essential lifeline infrastructures that must remain in service after strong seismic events. Recent design codes implement performance-based design methodologies which may call for increased seismic demands. However, most of the existing infrastructure in Canada was built prior to the enactment of modern seismic codes of the post-1980 era. Recent earthquakes revealed seismic vulnerability of bridge structures with a number of deficiencies in regards to low seismic design force levels, inadequate column confinement and lack of column shear capacity. The objective of this study is to assess the vulnerability of reinforced concrete bridge columns in Canada. Computer software DRAIN-RC, developed for nonlinear dynamic analysis of reinforced concrete structures, was used to determine the deformation demands of bridge columns under selected Eastern and Western Canadian ground motions. Deformation demands were subsequently compared with available research data in the literature on column deformation capacities to assess seismic vulnerabilities. Results exhibit different levels of performance for existing bridge columns in different regions of Canada, with bridges in western Canada showing higher vulnerabilities.
This paper looks at the use of fiber reinforced polymer (FRP) reinforcement in concrete columns, for use in new construction. The state-of-the-art on FRP reinforced concrete (RC) columns is presented with a brief discussion of research findings. The behavior of columns as well as FRP reinforcement in compression is included. The use of FRP transverse reinforcement is discussed in terms of its effectiveness as confinement reinforcement. The paper also includes a summary of an experimental study of FRP RC columns currently being conducted at the University of Ottawa. Details of the test program, as well as test results, are given. Results indicate that FRP reinforcement can be effectively used in new concrete columns. The use of FRP transverse reinforcement in columns was also investigated experimentally and analytically. Carbon FRP grids were used as column confinement reinforcement. Test results indicate that these grids, with relatively lower elastic modulus as compared to steel of equivalent volumetric ratio, were able to confine concrete effectively and improve column inelastic drift capacity. Columns with CFRP grids showed lateral drift capacities of from 4-6%, depending on the grid size and the number of grid cells.
This paper presents the results of nine as-built and carbon fiber reinforced polymer (CFRP) retrofitted reinforced concrete panels subjected to simulated blast loading using a pneumatically operated shock tube. The objective of the study was to characterize the blast response of CFRP retrofitted reinforced concrete panels, with and without supplemental mechanical anchorage applied to the CFRP. The results indicate that retrofitting can significantly increase the strength and stiffness of reinforced concrete flexure members and greatly enhance the displacement time-history response over non-retrofitted members. Debonding of the externally bonded CFRP was the failure mode for all retrofitted members. FRP anchors, designed to prevent or delay debonding failures through mechanical end-anchorage, were found to substantially enhance the performance of panels experiencing critical diagonal crack debonding. However, the FRP anchors were found to have no substantial effect on retrofit performance for the case plate-end interfacial debonding failures. In addition, the displacement time-histories for as-built and FRP retrofitted panel obtained through detail single degree of freedom analysis were found correlate well with those obtained experimentally. Finally, a discussion on the practical considerations of using externally bonded FRP retrofits to resist blast loads and recommendations for protective design are presented.
