Abstract:When a seismic force acts on bridges, the pier can be damaged by the horizontal inertia force of the superstructure. To prevent this failure, criteria for seismic reinforcement details have been developed in many design codes. However, in moderate seismicity regions, many existing bridges were constructed without considering seismic detail because the detailed seismic design code was only applied recently. These existing structures should be retrofitted by evaluating their seismic performance. Even if the seis… Show more
“…The multiple plastic hinge (4) formations is what really induce the higher peak loads. Kim et al 35 investigation also confirms the formation of four plastic hinges in the lateral directions, even though the investigation of 35 was based on circular columns with different material properties and dimensions. Figure 25 Geometry of twin column.…”
Bridges are among the most vulnerable structures to earthquake damage. Most bridges are seismically inadequate due to outdated bridge design codes and poor construction methods in developing countries. Although expensive, experimental studies are useful in evaluating bridge piers. As an alternative, numerical tools are used to evaluate bridge piers, and many numerical techniques can be applied in this context. This study employs Abaqus/Explicit, a finite element program, to model bridge piers nonlinearly and validate the proposed computational method using experimental data. In the finite element program, a single bridge pier having a circular geometry that is being subjected to a monotonic lateral load is simulated. In order to depict damages, Concrete Damage Plasticity (CDP), a damage model based on plasticity, is adopted. Concrete crushing and tensile cracking are the primary failure mechanisms as per CDP. The CDP parameters are determined by employing modified Kent and Park model for concrete compressive behavior and an exponential relation for tension stiffening. The performance of the bridge pier is investigated using an existing evaluation criterion. The influence of the stress–strain relation, the compressive strength of concrete, and geometric configuration are taken into consideration during the parametric analysis. It has been observed that the stress–strain relation, concrete strength, and configuration all have a significant impact on the column response.
“…The multiple plastic hinge (4) formations is what really induce the higher peak loads. Kim et al 35 investigation also confirms the formation of four plastic hinges in the lateral directions, even though the investigation of 35 was based on circular columns with different material properties and dimensions. Figure 25 Geometry of twin column.…”
Bridges are among the most vulnerable structures to earthquake damage. Most bridges are seismically inadequate due to outdated bridge design codes and poor construction methods in developing countries. Although expensive, experimental studies are useful in evaluating bridge piers. As an alternative, numerical tools are used to evaluate bridge piers, and many numerical techniques can be applied in this context. This study employs Abaqus/Explicit, a finite element program, to model bridge piers nonlinearly and validate the proposed computational method using experimental data. In the finite element program, a single bridge pier having a circular geometry that is being subjected to a monotonic lateral load is simulated. In order to depict damages, Concrete Damage Plasticity (CDP), a damage model based on plasticity, is adopted. Concrete crushing and tensile cracking are the primary failure mechanisms as per CDP. The CDP parameters are determined by employing modified Kent and Park model for concrete compressive behavior and an exponential relation for tension stiffening. The performance of the bridge pier is investigated using an existing evaluation criterion. The influence of the stress–strain relation, the compressive strength of concrete, and geometric configuration are taken into consideration during the parametric analysis. It has been observed that the stress–strain relation, concrete strength, and configuration all have a significant impact on the column response.
“…Prior to conducting numerical simulations of multi-column bents, it was decided that the modeling scheme outlined in Chapter 2 should be further validated using experimental data for a multicolumn bent. A review of the literature resulted in the selection of specimen RH-NS-T tested by Kim et al (2021) that best conformed to the reinforcement details of a Caltrans Era-1 bridge. The primary sectional data for specimen RH-NS-T is listed in Table 5.1.…”
Section: Validation Of Multi-column Bent Modelmentioning
confidence: 99%
“…An elevation and typical column cross-section are shown in Figure 5.2. Complete details of the specimen configuration and material properties can be found in Kim et al (2021).…”
Section: Validation Of Multi-column Bent Modelmentioning
The ShakeCast software platform, used by the California Department of Transportation (Caltrans), utilizes near real-time ground shaking maps generated by the US Geological Survey in conjunction with demand and capacity models, to evaluate the likely damage to all bridges in the vicinity of an earthquake event. The ability to estimate with reasonable accuracy the likelihood and extent of damage to bridges following an earthquake is crucial to post-earthquake activities such as the mobilization of emergency response. While the development of seismic demand models has seen considerable progress, there is a significant gap in our current ability to correlate demands with capacity limit states, particularly for older California bridges. Whereas modern bridges designed after 1990 are expected to perform well, older bridges, particularly those built before 1971 (and referred to as Era-1 bridges in this report), are vulnerable to damage. It is the goal of this research to address this gap by developing a range of component capacity limit states (CCLS), from minor damage up to collapse, for pre-1971 Caltrans bridge columns through modeling and comprehensive simulations. A simulation model is developed for typical non-ductile bridge columns considering flexure, shear and mixed shear-flexure failure modes and incorporating critical effects at the material level (such as confinement in concrete and bar buckling in reinforcing steel) and the sectional level (such as bond-slip due to strain penetration). Given the prevalence of drift-based measures in seismic design and assessment, the first choice considered in the development of the CCLS models was ductility. A strain-based approach was used to correlate damage with capacity limit states for both circular and wide rectangular sections that typify Era-1 bridge columns. Findings from this phase of work exposed a major drawback in using ductility-based measures to characterize capacity limit states under random earthquake-induced loading. Hence, a major effort was dedicated to developing a damage-index based approach to classifying limit states. The proposed damage-based approach to developing CCLS models was validated against experimental data and then applied to single, two and three-column bents. Fragility functions were developed wherein exceedance probabilities of damage states were examined as a function of a seismic intensity measure. The new damage-based methodology was successful in predicting a range of capacity limit states associated with visual damage such as cracking of the cover concrete, spalling of concrete, buckling of longitudinal reinforcement, crushing of the core concrete and multi-bar rupture. Findings from the study will not only assist in post-earthquake emergency response efforts but also in prioritizing strengthening of older, nonductile bridges.
“…When existing bridge structures are subjected to earthquakes, finally, special retrofit interventions should be needed for piers and connection details. An experimental study is presented in [10], based on six small scale specimens reconstructed to describe existing bridge piers under seismic (laboratory) conditions.…”
Exceptional loads on buildings and structures are known to take origin and manifest from different causes, like natural hazards and possible high-strain dynamic effects, human-made attacks and impact issues for load-bearing components, possible accidents, and even unfavorable/extreme operational conditions [...]
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