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This paper presents the analytical formulation and computational implementation of a conceptual probabilistic performance-based seismic design (PBSD) framework for ordinary standard bridge (OSB) structures. An updated probabilistic performance-based earthquake engineering (PBEE) assessment methodology is used for the parametric performance assessment of four distinct OSBs in California to investigate the effects of varying key structural design parameters over a primary design parameter space on risk-based structural performance measures. The dire need for a systematic PBSD framework for OSBs is illustrated given the significant variability in risk-based performance levels exhibited by these traditionally designed testbed OSBs. A PBSD methodology involving the design of the bridge piers is proposed wherein a risk-based feasible design domain in the primary design parameter space is identified which facilitates the risk-informed design/decision making process in the face of uncertainty. Sensitivities of risk-based feasible design domains compared with other (secondary) design variables and with the method employed for damage hazard assessment are investigated. [ABSTRACT FROM AUTHOR]

The existing machine learning (ML) models for vibration-based damage assessments often use highly compressed features or are restricted to preprocessed signals with fixed durations and sampling rates. Additionally, the learning capacities of ML models and computational resources are limited, which restricts using raw signals as direct input. This paper studied Mel filter banks (MFBs) for seismic signal processing, inspired by speech recognition technology. It is argued that the same filter designs in audio engineering may not be appropriate for seismic records, and therefore, a customized filter bank formulation was developed. Hybrid deep learning models for rapid assessments (HyDRA) were introduced as multibranch neural network architectures that enable end-to-end training for different types of processed vibration data structures. Moreover, the performance-based earthquake engineering (PBEE) equation was adjusted to integrate ML model uncertainties for probabilistic assessments. The proposed concepts were validated in a case study based on a data set of 32,400 nonlinear time-history analyses of a highway bridge in California. Insights and guidelines are provided for optimum filter design based on 5,184 experiments. Several HyDRA architectures were compared with benchmark models. The optimized MFB feature type outperformed features obtained from continuous wavelet transform and a stacked vector of conventional earthquake engineering indexes. A Bayesian variant of HyDRA was investigated to showcase its integration in the modified PBEE equation. Adopting custom filter banks with the HyDRA architecture enables effective feature extraction from raw vibration records by diversifying feature space and preserving information in the time and frequency domains. [ABSTRACT FROM AUTHOR]

This paper presents full-scale experiments and computational analyses on exposed column–base plate connections with ductile anchors. The aim is to examine the seismic performance of these connections for their prospective use as weak bases, wherein steel moment frames are designed to concentrate inelastic rotations in the base connections rather than in the connected columns. The connections feature upset thread anchor rods in which the threads are milled to a smooth shank, providing a designated stretch length over which inelastic deformations may be concentrated. The shank is frictionally isolated from the footing using polyethylene tape. The four full-scale experiments investigate the effects of axial force, rod diameter, and rod material grade. The test specimens withstand (without anchor rod failure) the application of two Applied Technology Council–the Joint Venture partners of the Structural Engineers Association of California, the Applied Technology Council, and the Consortium of Universities for Research in Earthquake Engineering (ATC-SAC) protocols applied consecutively (each to drift amplitudes of 5%), followed by additional cycles to 6.5% drift amplitude. Complementary line element–based and continuum finite-element simulations are conducted to examine to what extent the experimentally observed response may be generalized to untested configurations. Implications for design are summarized, along with the limitations of the study. [ABSTRACT FROM AUTHOR]

Base isolators and fluid viscous dampers are viable protective devices that have been commonly considered in the seismic protection of civil engineering structures. However, the optimal design of these devices remains a tedious and iterative undertaking due to the uncertainty of ground motions, the nonlinear behavior of the structure, and its change of dynamic characteristics (i.e., effective stiffness and damping ratio) under each new design. The optimal design problem becomes more challenging concerning a multiresponse bridge system where conflicting damage potential is often expected among multiple bridge components (e.g., column, bearing, shear key, deck unseating, foundation). In this respect, this study develops a risk-based optimization strategy that directly links the expected annual repair cost ratio (ARCR) of the bridge to the design parameters of base isolators and fluid dampers. This strategy is achieved by devising a multistep workflow that integrates a seismic hazard model, a design of experiment for bearings and dampers, a logistic regression towards parameterized component-level fragility models, and a bridge system-level seismic loss assessment. The developed ARCR is parameterized as a convex function of the influential parameters of seismic protective devices. As such, optimal bearing and damper designs can be pinpointed by directly visualizing the global minimum of the parameterized ARCR surface. The optimal design is carried out against a typical reinforced concrete highway bridge in California that is installed with the fluid dampers and three types of widely-used isolation bearings—the elastomeric bearing, lead-rubber bearing, and friction pendulum system. It is shown that optimal design parameters can be obtained to significantly reduce the expected ARCR of the bridge, whereas combining optimally designed bearings and dampers can provide the minimum seismic risk. [ABSTRACT FROM AUTHOR]

This study develops the probabilistic seismic response and capacity models for the broad collection of standard pile designs that are routinely incorporated into bridges in California. A review of the state bridge inventory indicates considerable variations in design details for different standard pile types used across multiple eras. For each pile type, fiber-section-based pile models attached with p-y soil springs are built to incorporate nonlinear behaviors of soil materials, a wide array of heterogeneous soil profiles, full-range damage states of piles, and realistic connection details between piles and footings (i.e., pile caps). Moreover, force-displacement responses of pile-soil systems under a large number of pushover analyses are regressed as response models consisting of five parameters [termed as response five parameter (R5P) models], which can capture all essential behaviors of laterally-loaded piles. Capacity damage states and limit state models are defined for different pile types by linking pile global responses to fiber-scale material behaviors at plastic hinge locations. Procedures are further provided to expand R5P models to pile foundation models at the regional scale, taking into account the pile group effect and capacities of pile cap backfills. R5P models for all distinct pile types are further summarized in an Excel workbook to facilitate their practical implementations. In general, this study provides a comprehensive and consistent set of response and capacity models to quantify the seismic damage potential of regional pile foundations, as well as to capture their dynamic interplays with other crucial bridge components, such as columns and abutment components. The proposed pile models are expected to significantly enhance the existing modeling capability toward improved seismic risk assessment of California's bridge infrastructure. [ABSTRACT FROM AUTHOR]