Seismic performance of concrete bridges during Canterbury earthquakes

Tall hollow concrete piers with high width‐to‐thickness ratios are commonly used in long‐span box girder bridges. Such thin‐walled structures present the possibility of failure due to local buckling. So, in common practice, diaphragms are usually included in hollow piers to improve the local stability; however, is that necessary? Although experimental research on the buckling behaviour of hollow piers has been conducted extensively, few analytical attempts have been performed to reveal the effects of the width‐to‐thickness ratio on local buckling behaviour. To this end, an analytical model has been proposed to investigate the local buckling behaviour of hollow piers. Following the Ritz‐Timoshenko method, an analytical formula for critical local buckling stress has been developed and verified to have good accuracy compared with finite element analyses. Based on the buckling failure mode of a hollow pier with a slenderness ratio > 6, it can be reasonably postulated that the strength of the hollow pier will be unaffected by local compression flange buckling when the wall width‐to‐thickness ratio is < 24, and it is entirely unnecessary to include diaphragms in hollow piers for stability. Additionally, it is equally interesting that the critical width‐to‐thickness ratio of a hollow pier with a slenderness ratio > 4 derived using the proposed model is the same as the value given by the current AASHTO‐LRFD Bridge Design Specifications.

Investigation of the buckling behaviour of thin‐walled hollow concrete piers

Zhou

Liu

2016

Experimental study on seismic performance of steel fiber reinforced concrete wall piers

Babaei

Mortezaei

Salehian

2020

Extensive damage to the bridges in recent earthquakes has revealed the vulnerability of these structures to the seismic excitation. Bridge piers play a key role in maintaining the operability of the bridge structure during and after earthquakes. As determinant elements in single‐pier bridges, wall piers significantly affect the bridge structure behavior. Hence, the present experimental study was conducted to examine the seismic performance of wall piers made of modern materials, that is, fiber reinforced concrete (FRC) in RC bridges. Eight wall piers made of steel fiber reinforced concrete (SFRC) with different aspect ratios, steel percentages and concrete strength were subjected to lateral load. The results showed that using SFRC reduced the steel strain within the serviceability range. Compared to conventional concrete, SFRC changes failure modes and deformational characteristics and also increases the energy dissipation capacity, stiffness in every drift values, load‐bearing capacity as well as yielding length.

Improvement of energy damage index bounds for circular reinforced concrete bridge piers under dynamic analysis

Amirchoupani

Abdollahzadeh

Hamidi

2021

An improvement of energy damage index bounds for circular reinforced concrete (RC) bridge piers under dynamic time history analysis is presented in this study. The energy-based damage model has been defined as a ratio of hysteresis dissipation energy to input energy for performance evaluation of circular RC bridge pier systems. Based on the energy balance equation, the mentioned damage model can consider all energy aspects, including kinematic energy, strain energy, hysteresis energy, damping energy, and input energy. Additionally, the effect of ground motion duration, amplitude, and frequency content is appropriately considered in this damage model. For this purpose, the damage limit state bounds for two empirical RC bridge piers are statistically evaluated under the 22 far-field ground motion sets of FEMA-P695 for simulation of strong-earthquake motion and consideration of record-to-record variability.First of all, appropriate validation between empirical and numerical fiber element models is implemented to estimate accurate results. Then, damage data at each performance level through strain limit states are collected by developing energy incremental dynamic analysis curves. Statistical results on collected damage data are presented in all performance levels to determine damage index bounds by the convolution of fragility curve distribution. Hence, five damage index bounds at five performance-level are suggested, including very slight, slight, moderate, extensive, and complete damage. Finally, the effect of the other damping ratios on the modified energy damage model is carried out by using the beta coefficient in the formula. In the end, the modified energy damage model is compared with other damage indices to investigate the efficiency of the proposed damage model.