This paper presents results of a numerical study that examined the flexural behavior of corroded reinforced concrete (RC) beams. Two-dimensional nonlinear finite element (FE) models were built and analyzed using DIANA FE analysis software. A simplified approach was implemented in the FE models to simulate the damage induced by corrosion to reduce the computational efforts. The numerical analyses were validated with experimental tests of large-scale and small-scale RC beams subjected to the coupled effects of corrosion and different levels of service loads. The predicted response was in good agreement with test results in terms of failure modes, residual ultimate load capacity, and ductility. The validated FE models were then used to conduct a parametric study for cases that were not covered in the experimental program, including the level of corrosion, level of service loads, strength of concrete, and tensile reinforcement ratio. This investigation showed that increasing service load levels of corroded beams caused a further reduction in ultimate load capacity and ductility. Moreover, increasing the tensile reinforcement ratio had a significant impact on improving the load-carrying capacity of corroded RC beams.

Recent seismic events revealed the vulnerability of older structures. Retrofitting, especially with active force control, mitigates seismic risk by calculating real-time control forces to minimize deformations during earthquakes. However, current strategies often overlook nonlinear behavior. This study develops an active force control procedure for reinforced concrete frames, considering both elastic and inelastic deformations. It incorporates a time-varying stiffness matrix and rotational springs to simulate hysteretic response. Control forces are computed using an instantaneous optimal control algorithm. The procedure effectively reduces inelastic deformations and associated damage, despite challenges in hardware implementation and time delays.

Reinforced concrete shear walls are crucial in providing lateral resistance and stability to structures during seismic events. Despite extensive research on shear walls, a significant gap exists in accurately estimating the shear capacity of barbell squat shear walls, especially when subjected to seismic forces. This gap presents a critical challenge in ensuring the safety and resilience of structures in earthquake-prone regions. Accordingly, the study aims to develop advanced machine-learning models to predict the shear capacity of barbell squat shear walls under seismic loads. By utilizing a comprehensive dataset of experimental results, the study seeks to create high-accuracy predictive models. The significance of this research lies in its potential to enhance the understanding and prediction of shear wall behavior for earthquake-resistant design, contributing to the construction of safer and more resilient buildings. Furthermore, the machine learning models developed in this study can be a valuable tool for engineers and researchers for preliminary assessment of shear capacity within the range of the compiled experimental database, while recognizing that response-related variables such as εcc limit direct design-stage use unless omitted or estimated independently. Additionally, feature importance analysis is conducted to identify the most influential variables affecting shear capacity. This approach improves model transparency and offers more profound insights into the key factors affecting the performance of barbell squat shear walls under seismic conditions. The outcomes of this research are expected to bridge the current knowledge gap and pave the way for more informed decision-making in seismic design practices.

An experimental study was carried out to examine the flexural behavior of reinforced concrete (RC) beams subjected to service loads coupled with the corrosion of the flexural reinforcement. The experimental program consisted of tests of six simply supported beams with dimensions of 200 & times; 300 & times; 3400 mm. Two beams were loaded to failure using a four-point bending test, serving as control specimens. Two beams were first loaded to 60% of the beam ultimate load capacity, and then the corrosion process of the longitudinal tensile reinforcement was accelerated using the direct impressed current technique while sustaining the applied loads. Similarly, one beam was corroded under service loads but for a shorter duration to examine the influence of different levels of corrosion. The remaining beam specimen was corroded with no service loads. Test results indicated that corrosion of the main flexural reinforcement resulted in significant reductions in the ultimate load capacity and ductility of RC beams. The results of this study were also compared with test results obtained from corroding small-scale beams with a smaller percentage of steel and fewer number of bars. The comparison revealed that the reduction rates in ultimate load capacity and ductility associated with corrosion in RC beams under service loads were accelerated when a smaller percentage of steel with fewer bars was used.

Canadian highway bridges are aging and giving rise to safety concerns. Frequent monitoring and significant investments are required to maintain their safety and serviceability levels. Corrosion of steel in reinforced concrete (RC) bridges leads to deterioration of materials, reduction of load-bearing capacity and increased maintenance costs. There is concern that climate change may further accelerate and amplify existing and new deficiencies alike, increasing the rate of corrosion and imposing new extreme loads on existing infrastructure. A now common technique for rehabilitation consists of externally bonded (EB) fibre-reinforced polymers (FRP) in critical locations of RC components to improve their overall structural performance. This technique has been shown to provide increased load-bearing capacity for damaged girders, however, there remains uncertainty related to their effectiveness when subjected to high environmental temperatures, especially when combined with corrosion damage. A two-span simply supported prestressed RC highway bridge was designed based on a review of existing bridges in Canada. A parametric study was conducted on this bridge to examine the effects of EB FRP rehabilitation on its performance when subjected to various levels of flexural reinforcement corrosion. The composite effects of heatwaves on the rehabilitated bridge were also investigated to assess their influence on the load-carrying capacity and serviceability levels. The study managed to quantify the ultimate strength and serviceability levels of EB FRP-strengthened bridges. This information will help determine the rehabilitation requirements of existing infrastructure, enabling adaptation to emerging challenges posed by climate change in the upcoming decades.

Over the past few decades, there has been a growing interest in the use of carbon fibre-reinforced polymers (CFRP) for the cables of cable-stayed bridges due to their high strength, corrosion resistance, relatively high stiffness, good fatigue resistance, and high resistance to creep rupture. One notable difference between the mechanical properties of steel and CFRP is their coefficients of thermal expansion at 12 × 10–6 °C−1 and 0.6 × 10–6 °C−1, respectively, and it is conceivable that this difference causes bridges with CFRP cables to behave differently under temperature loads than bridges with steel cables. A literature review revealed that very few studies examine this topic. This paper studies the structural performance of cable-stayed bridges with CFRP cables subjected to temperature loads by creating finite element models of a cable-stayed bridge with a main span of 250 m, one with steel cables and one with CFRP cables, and comparing their performance. The two bridges were subjected to thermal expansion and contraction loads, which were determined using the requirements of CSA S6-19. This paper collects and discusses the following data: cable forces; axial force, shear, and bending moment in the deck; axial force, shear, and bending moment in the pylons; and vertical deck displacements. It was found that temperature loads significantly impact the behaviour of bridges with CFRP cables due to CFRP’s low coefficient of thermal expansion, and it is evident that this behaviour is also affected by the type of connection between the deck and the pylons.

Base isolation technology has significantly advanced infrastructure protection against moderate and severe seismic activities. Consequently, it gained considerable attention over the past with new systems and approaches developed to improve its applications. Nevertheless, the literature still lacks a new literature review paper that summarizes and discusses previous findings on multi-stage friction pendulum bearings (MFPs), which offer heightened energy dissipation at the expense of increased complexity. Accordingly, this study performs a bibliometric analysis, summarizes and discusses key findings related to MFPs, and explores the balance between enhanced energy dissipation and the complexity trade-offs in MFPs with increased effective pendula. Besides, it briefly reviews the evolution and current state of MFPs and highlights their capacity to mitigate seismic vibrations through a combination of sliding and rolling friction modes. Moreover, it discusses the improvements in the hysteresis behavior of MFPs that led to better energy dissipation and smoother loading and unloading processes in structural engineering applications. Furthermore, the study describes the critical trade-offs between the complexity of MFP analysis and design and their superior energy dissipation capabilities.

The design of blast-resistant civilian structures is not a common practice because blast is a rare event to occur. However, the rising concern from the increased number of terrorist attacks targeting civilian facilities triggered new challenges and accelerated the need for designing and building blast-resistant structures. Columns are critical structural elements, and loss of a column can trigger progressive collapse of the building. Protecting building columns through hardening can significantly improve the structure’s resistance to blast loads. The current research aims to address blast risk of reinforced concrete (RC) columns and potential improvements in their response by developing an innovative hardening technique. The experimental part of the study involves designing, building, and testing four half-scale RC columns that are hardened by externally anchored longitudinal prestressing seven-wire strands. The strands are anchored to the columns with three different longitudinal profiles: single harped, double harped, and triple harped or parabolic. A reference column and three hardened columns were tested under blast-induced shock waves generated by a blast simulator (shock tube). The test results included reflected pressure and impulse, maximum deflection, support reactions, and qualitative assessment of the level of damage. The results indicated that the behavior of hardened columns was significantly improved compared to the reference column. It was concluded that, on average the hardened columns could resist 20

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.

A performance -based unified (PBU) procedure has recently been proposed by the National Research Council Canada to systematically evaluate seismic design requirements available in the National Building Code of Canada (NBC). Conventional construction reinforced concrete moment -resisting frame (CC-CMF) and ductile reinforced concrete moment -resisting frame (D-CMF) systems were used in this paper to first assess the proposed PBU procedure and second determine the adequacy of the basis for seismic design requirements in NBC and see its performance margin against different structural performance levels. Results indicate that the detailed screening in the PBU procedure efficiently reduces the number of incremental dynamic analysis by more than 60% for CC-CMF while providing remarkable accuracy. It was also found that the CC-CMF system designed for the Normal importance category can provide an adequate margin against life safety performance level objectives, while the D-CMF system designed for the same importance category passes the collapse prevention performance level criteria.

This paper investigates the nonlinear static and dynamic analysis of seismically deficient reinforced concrete frames retrofitted with a novel buckling restrained brace (BRB). The authors developed the new BRB system through experimental research, featuring a gapless inner stainless-steel bar, enhancing inelastic deformability and energy dissipation. The study aims to develop reliable models for reinforced concrete frames with and without the BRB system using numerical analyses under reversed cyclic loading. Initially, nonlinear static analysis was conducted on two single-story, single-bay, large-scale reinforced concrete test frames: one representing an older building and the other retrofitted with the BRB system. Validation of the numerical results was achieved by comparing them against experimental data. Subsequently, the analysis was extended to a six-story existing frame building in Vancouver, Canada, to evaluate the BRB system's effectiveness through nonlinear dynamic response history analysis. Key performance metrics such as story drift ratios, base shear force, column capacity versus demand, moment-chord rotation response, and ductility were assessed. The retrofitted building showed significant improvements in seismic performance, with the maximum interstory drift ratio reduced to 1.16 % from 2.3 %, achieving the Life Safety performance level per ASCE 41-13 standards. Column shear deficiencies were reduced by 64 %. Additionally, the BRBs demonstrated stable axial force-axial displacement hysteretic behavior, with a maximum displacement ductility demand ratio of 4.1 and a maximum strain of 0.15 %, within the Enhanced Safety performance range. This research confirms the novel gapless BRB system as an effective retrofitting solution for older buildings in seismically active regions.

The National Building Code of Canada (NBC) employs seismic force modification factors (i.e. ductility-related factor, R d , and an overstrength-related factor, R o ) for different Seismic Force Resisting Systems (SFRSs), which, since 2005, are largely based on engineering judgment and qualitative comparisons of seismic response characteristics of different SFRSs. Currently, there is no unified procedure in Canada for systematically quantifying these values, which has potentially led to perceived inconsistent levels of performance between buildings built with different SFRSs. While some research has been carried out in Canada to quantitatively evaluate the seismic response of different SFRSs using the FEMA P695 methodology with some modifications, inconsistencies exist among different research works. Moreover, the number of archetypes developed in these studies was limited, due to the computationally laborious incremental dynamic analysis (IDA) step in FEMA P695. Therefore, there is a need for a consistent and efficient methodology for structural performance assessment of different SFRSs in Canada. The proposed performance-based unified (PBU) procedure is to systematically quantify R d and R o factors for different SFRSs in the NBC. The PBU procedure is designed to be a performance-based approach (vs the risk-based approach of FEMA P695). In addition, our procedure is devised to optimize the number of archetypes through a two-level screening procedure using a nonlinear pushover and time history analyses before running the IDA. To validate the PBU procedure, we developed 21 different concrete moment frame archetypes covering various key parameters. The results verify the efficiency of the screening feature of the PBU procedure by a significant reduction in the number of archetypes requiring IDA.

A combined experimental and analytical investigation was conducted at the University of Ottawa to assess the performance of blast-resistant window retention anchors to generate design information. The experimental phase of research involved 46 full-scale window tests with different parameters. The analytical investigation included numerical modeling and dynamic analysis of windows to expand the experimental results and to assess the significance of design parameters. Computer software LS-DYNA was selected for the analyses. Analytical models of selected test windows with aspect ratios of 1.0 and 3.0 anchored on structural steel, reinforced concrete, concrete block masonry, and stone masonry substrates were modeled. The models were validated against experimental data. Additional windows with aspect ratios of 1.5 and 2.0 were also modeled for investigation. The models were used to conduct a parametric investigation with the parameters consisting of substrate flexibility, anchor fixity conditions, window size and aspect ratio, frame rigidity, number and spacing of anchors, and the threat level as defined by reflected pressure-impulse combinations. The significance of each parameter is illustrated with emphasis placed on the magnitude of anchor shear and tension design forces. The distribution of anchor forces is obtained numerically. Anchor forces and distributions are compared with those observed experimentally. Design force distribution along the perimeter of window frames is recommended for use in design. The paper provides the results of numerical simulations illustrating the significance of design parameters on anchor design force levels and their distributions.

This paper presents a summary of experimental research on the performance of blast-resistant window anchors and the development of a design procedure for the anchors. The experimental results, obtained from forty-six window tests conducted under simulated blast loading using a shock tube are reported. Two analysis procedures that were developed for anchor design are described. The first procedure involves a two-degree-of-freedom dynamic analysis. The second procedure involves a single degree of freedom analysis that can be implemented manually. The development of both methods is presented for the anchorage design of windows subjected to blast loads.

For the past few decades, there has been an increase in awareness regarding the safety of highway bridges from blast loads. Since abutments/Retaining walls (RWs) are portions of bridges, investigating abutments/RW or RW behaviour under blast loads is important. As there have not been any studies investigating the dynamic response of retaining walls due to blast loading, an experimental study was conducted to examine the influence of blast loads on the dynamic behaviour of reinforced concrete retaining wall (RCRW) with sand as a backfill material. A shock tube was used to generate blast loads on the soil-RW model. The influence of the relative density, backfill saturation, blast load intensity, and traffic load equivalent surcharge on the blast behaviour of RCRW with sand backfill was studied. The results showed that the modes of wall movement were affected by the backfill relative density, blast load intensities, and degree of saturation. Under the same load conditions, an increase in the wall movement was noticed in loose backfill, and a translation response mode was evident in this condition. A relationship between wall relative movements and mobilized earth pressure coefficients was determined. The mobilized passive resistance of the RW backfill induced by blast load was used to determine the force–displacement relationship. Acceleration time histories for RW/backfill were found for all conditions. The findings of this research will help to properly evaluate and design bridges’ abutment and to develop resilient transportation infrastructure systems.

National Building Code of Canada (NBC) specifies 45 Seismic Force Resisting Systems to ensure the safety of building structures. Conventional construction concrete moment-resisting frame (CC-CMF) is one of these systems whose seismic response has not been systematically studied in Canada. This paper is an attempt to study the seismic performance of this system using the FEMA P695 methodology. In this regard, different archetype configurations were developed and analyzed through nonlinear static and dynamic analyses. Performance assessment results show that the CSA and NBC requirements for CC-CMF system represent the lower bound of values for seismic force modification factors, and conservatively meet life safety objectives presented in the NBC. Furthermore, different scenarios were considered for identifying ductility-related seismic force modification factor from pushover curves. The effect of height and gravity load levels on seismic force modification factors and collapse margin ratios are also presented by comparing archetypes having different configurations.

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.

•Response of retaining structure (RS) to blast load studied.•RS model was subjected to a simulated blast load using a shock tube.•Lateral earth pressures increased with blast load intensities.•Maximum dynamic resistance function reached at high-intensity pressure.