The performance objective of current seismic design guidelines such as CALTRANS or LRFD for ordinary bridges follows the life-safety design premise, where significant structural damage is possible under design-level earthquakes while the risk of collapse is minimized. In order to mitigate the overall damage level of bridges from earthquakes and improve their post-earthquake serviceability, an ordinary RC bridge, whose design characteristics are consistent with the recent specifications, was retrofitted by adding an SMA reinforced concrete jacket around its column. Detailed analytical models of the original and the retrofitted bridge, in which modeling of various bridge components and soil-structure effects are accounted for, were developed and analyzed under a suite of near-fault earthquake records. Damage levels of the bridge components were determined based on the achievement of the predefined component limit states, and they were used to guide system-level bridge damage states, thereby, the post-earthquake service level of the bridge. The original bridge experienced some significant damage levels, requiring bridge services to be suspended, while the damage levels of the retrofitted bridge did not go beyond moderate damage levels, in which the bridge services can still be open to the public with some safety measures in place. The large residual column drift responses in the original bridge, resulting from the low residual strain capacity of conventional steel rebars, were the primary reason for rendering the original bridge out of service under some events. Such an issue of large residual column drift responses was not observed in the retrofitted bridge owing to the self-centering capability of the SMA reinforcing bars used in the concrete jacket. Moreover, it was observed that introducing SMA reinforcing bars in the bridge column helped mitigate not only the damage levels of the column but also the damage levels of the other bridge components. Overall, the applied retrofitting technique was deemed effective in addressing the vulnerability of the case study bridge and thus improving its post-earthquake serviceability.

In highly seismic regions, RC walls as LFRS are being designed according to chapter 18 of ACI 318 which are categorized as special structural walls. Hence, there are additional requirements regarding the detailing and position of lap splices. However, in low-to-moderate seismic and wind-controlled regions, RC walls as LFRS can be designed as ordinary walls according to chapter 11 of ACI 318; there are no specific requirements of detailing and position of lap splices in these ordinary walls, yet. Hence, these lap splices can be placed at critical sections of the walls which might be problematic.

At the current time, the approach of seismic design and wind design differs in terms of nonlinear demands. Seismic design has developed R factors to reduce loads with an expense of having an inelastic behavior or a performance-based design approach to evaluate demands and behavior of the building, whereas wind design still relies on having a linear response to code prescriptive wind load provisions from the current ASCE 7 strength-level demands. One of the reasons for elastic design of structures under wind loading is due to the lack of research and data regarding structure’s performance subjected to wind loading. While intending a structure to behave linearly seems like a safer way to design, this approach can lead to overly-conservative design which can induce unintended negative effects on the structural performance under seismic loading due to wind-based design (Abdullah et al. 2020; Unal et al. 2024).

Favorably, the advancement of performance-based wind design needs is recognized with the publication of ASCE’s Prestandard for Performance-Based Wind Design (2019), NIST’s Advancement in Performance-Based Wind Design Workshop Report (2023), and the development of Appendix W in ACI 318-25 regarding performance-based wind design. The current emphasis is to have a minor nonlinearity in critical sections of LFRS; in the case of core walls, these critical sections will be on coupling beams and wall piers. Nevertheless, critical sections of core walls must sustain cyclic loadings; as mentioned in the previous paragraph, lap splices can be placed at the critical sections for ordinary walls. Hence, further studies and experiments to evaluate the nonlinear behavior of these elements are significant to accelerate the transition to nonlinear design for wind loading.

After a moderate-to-strong earthquake, post-earthquake assessment of structures will be required, and visual inspection and damage classification are key steps in that process. Therefore, a reliable methodology to classify damage of components based on the visual inspection was developed to ease and improve the accuracy of post-earthquake assessment. Visual Damage States (VDS) databases of twelve reinforced concrete components were compiled to facilitate damage classification by comparing the observed damage pattern/level of a component with the progressive damage of experimental tests. VDS databases include specimen data, photos at different damage states and key parameters to filter and select representative test specimens. Each damage state is related to a component damage classification and a level of repair required. The methodology is used in the Guideline for Post-Earthquake Assessment, Repair, and Retrofit of Buildings of the project ATC-145.

Safety-critical repair is required for components with lateral strength loss (LSL). Therefore, guidance on the efficacy of reinforced concrete wall repair is essential for future earthquakes. A lack of test of flexural repair of reinforced concrete walls was found, especially in walls with splices and ordinary detailing. To address this issue, a 1/3-scale c-shaped ordinary reinforced concrete wall with lap splices in the wall-foundation interface was tested, repaired, and retested. As damaging protocol, a simulated wind loading protocol and then a seismic loading protocol was applied up to a 67% lateral strength loss. The wall had a flexural failure so damage before repair included buckling and fracture of longitudinal reinforcement, concrete spalling, and severe core concrete crushing in the flanges above the splice region. The repair technique involves concrete and reinforcement replacement in the splice region and the heavily damaged region. New longitudinal reinforcement was spliced in the bottom with the starter bars and connected to the existing reinforcement in the top with a mechanical coupler. During repair, transversal reinforcement spacing was reduced in the hinge region from 3 in. to 2.25 in, which prevent bar buckling before 2.0% hinge rotation in the repaired wall. The overall performance of the original wall and the repaired wall was similar up to 1.5% hinge rotation. The cold joints between existing concrete and the new concrete did not affect the structural performance of the repaired wall. A description of the repair technique and a comparison of the test results will be presented. Furthermore, different repair approaches for future tests will be presented.

As part of the Next Generation Liquefaction (NGL) project, we are developing probabilistic triggering and manifestation models using laboratory data and cone penetration test (CPT) case histories in the NGL database. The case histories are used to develop probabilistic models for surface manifestation conditional on susceptibility, liquefaction triggering, soil properties, stratigraphic details, and other features. Susceptibility is interpreted as a sole function of soil composition and is expressed as a probabilistic function of soil behavior type index, Ic, obtained from CPT. A triggering model is derived based on laboratory tests on high-quality specimens from literature; this model captures mean responses and uncertainty reflective of data dispersion and is considered as a Bayesian prior that will subsequently be updated by field observation data. A manifestation model is then regressed from field case histories where surface manifestation was or was not observed, information on soil conditions that enables identification of layers likely to liquefy, and ground shaking conditions. We describe the approach applied to develop our manifestation model; for a given layer this model considers layer depth, thickness, CPT tip resistance, and Ic. The result of this process is a logistic function in which manifestation probability decreases with increasing depth, decreasing thickness, increasing tip resistance, and increasing Ic. Profile manifestation is then derived by aggregating individual layer manifestation probabilities.