On April 2020, the 260 m-long reinforced concrete (RC) arch bridge of Caprigliola (Massa and Carrara, Italy) suddenly collapsed into the Magra river. In this work, aimed at investigating potential ...reasons behind the observed failure, a numerical study is conducted using the Applied Element Method (AEM), which allows the explicitly modelling of damage propagation and progressive failure up until complete collapse. Both local and global models of varying levels of detail have been developed and the consequences of different possible failure scenarios induced by selected potential triggering factors are compared with publicly available forensic evidence. Although only cross-correlations against future official post-collapse reports, currently not available, might permit the establishment of more definitive conclusions on the causes behind the observed collapse of the bridge, a seemingly good agreement was nonetheless found between predicted and observed damage and debris distribution for one of the modelled scenarios (induced movements of one of the bridge piers/abutments), which may thus be deemed as potentially more plausible than the others.
•Fatigue behavior on two types of cutout in two closely spaced floorbeams is first studied via field monitoring.•A large radius curve can increase the stress level at the floorbeam cutout.•In-plane ...stress dominates the total stress at the floorbeam cutout.•Fatigue category at the floorbeam cutout need to be reduced for poor fabrication.•Floorbeam thickness should be increased for the bridge under overloaded traffic.
This paper provides comparative results on stress behavior and fatigue performance of two types of cutout geometry on orthotropic bridge decks based on simultaneous field monitoring and finite-element method (FEM) analysis. The two types of cutout are incorporated in two closely spaced diaphragms with distance of 6 m and at the same transverse location on a real bridge, allowing simultaneous stress measurement under random traffic flows. The research was conducted on the Pingsheng Bridge in Southern China, a self-anchored suspension bridge with a main span of 350 m and a steel box girder with orthotropic steel bridge decks (OSBD). Results of the study reveal that the two types of cutout geometry present high stress response and severe stress concentration at the floorbeam (FB) cutout, and that the excessively large stress at the original FB cutout contributes greatly to the early cracks of this detail. Compared to the original cutout geometry, the new cutout geometry with large radius increases the stress level at the FB cutout, resulting in a further low fatigue life at this detail. Meanwhile, the new cutout geometry also deteriorates the fatigue resistance at the rib-to-floorbeam (RF) weld connection, particularly at the detail of rib wall at cutout, where the stress level is significantly increased and its fatigue life becomes substantially lower than the design life of 100 years. In addition, the new cutout geometry only slightly improves the out-of-plane distortion under direct wheel loading, and the in-plane stress still dominates the total stress at the FB cutout. Since the new cutout geometry weakens the FB web, the total stress at FB cutout will increase due to the increased in-plane stress. The research also finds that if the free edge of cutout did not satisfy the fabrication requirement per the AASHTO LRFD, category B is suggested for fatigue evaluation at the FB cutout, which is confirmed by the observed fatigue life of the original FB cutout on the real bridge. It is concluded that the new cutout geometry lowers the fatigue resistance both at the FB cutout and at the RF weld connection, hence it will no longer be recommended to retrofit the present bridge in the future.
Despite many studies on barge collisions with girder bridges in the literature, this paper investigates the progressive damage behaviors and nonlinear failure modes of a cable-stayed bridge pier ...subjected to ship collisions using finite element (FE) simulations in LS-DYNA. The damages in the pier initiate with appearing of local shear failures in the slender columns during the ship collision stage and reach the severe cross-sectional fractures associated with the formation of plastic hinges which causes the combined shear-flexural failures during the free vibration phase of the pier response. In addition, an analytical simplified model with two-degree-of-freedom (2-DOF) is proposed to formulate the strain rate effects of the concrete materials as the dynamic increase factors in the global responses of the impacted pier. It is found that the analytical model is able to efficiently estimate the impact responses of the structure compared to those from the FE high-resolution simulations. Moreover, three different damage indices are proposed based on the pier deflection, the internal energy absorbed by the pier, and the axial load capacity of the pier columns to classify the damage levels of the pier. Finally, an efficient damage index method is determinant by comparing the calculated results with the damage behaviors of the pier observed from the FE simulations.
•The damage progressing process of a concrete cable-stayed bridge pier subjected to ship collision is numerically evaluated.•The strain rate effect is formulated using an analytical model with two-degree-of-freedom (2-DOF).•Different damage indices are proposed based on the pier deflection, internal energy, and residual axial load capacity.•Deflection-based damage index gives a more efficient approach in describing the damage levels compared to FE simulations.
A wireless sensor system has been suggested and tested in the place of forty five sensors of five types among the sensors used extensively in suspension bridges to prove the viability of wireless ...sensor network in actual implementation. ZigBee (IEEE 802.15.4) is used for short-distance communications among sensors and Code Division Multiple Access (CDMA) for long-distance wireless communications with remote locations. A data logger is integrated with a sensor and ZigBee into a one-channel data logger that combines sensor, logger and digital communication modules to allow for the addition or replacement of a sensor with ease. Lastly, the wireless sensor network-based bridge health monitoring system proposed herein is developed in the form of an application that is intended to ensure universal applicability and designed to maximize the ease of wireless sensor network.
► Reliable bridge structural health monitoring using wireless sensor network. ► Wireless sensor network test on a large suspension bridge. ► ZigBee for local sensor network and CDMA for long distance data transferring. ► Antenna type and memory buffer are important for the network reliability.
•Probabilistic approach to numerically evaluate dynamic allowance factors IM.•Vehicle-bridge interaction method to analyze the coupling system.•Stochastic generation of different pavement ...irregularity types in modular bridges.•Deterministic evaluation of IM factors may lead to unreliable results.•Probabilistic evaluation of IM factors can lead to important material savings.
A reliable evaluation of dynamic amplification effects is crucial in bridge design in order to achieve safer and economical solutions. In engineering practice, these effects are commonly taken into account through dynamic load allowance factors (IM) specified by the codes. However, some codes allow the calculation of these IM factors through more advanced dynamic analysis in order to achieve more realistic results. Therefore, a methodology to numerically evaluate the IM in bridges is described. The methodology is based on a vehicle-bridge interaction model that can take into account any configuration of pavement irregularities. A case study consisting of two modular steel bridges is presented. In order to reach a comprehensive characterization of the IM factors, a probabilistic analysis is conducted, taking into consideration the stochastic generation of random irregularity profiles based on pavement roughness and experimentally measured manufacturing imperfections, as well as a wide range of vehicle speeds. The results obtained in this study demonstrate the advantages of performing a probabilistic numerical evaluation of the IM factor in comparison to the use of pre-defined factors proposed by design codes. The consideration of IM factors based on probabilistic assessments can lead to relevant material savings in the design of steel modular bridges.
An ambient vibration survey of the Humber Bridge was carried out in July 2008 by a combined team from the UK, Portugal and Hong Kong. The exercise had several purposes that included the evaluation of ...the current technology for instrumentation and system identification and the generation of an experimental dataset of modal properties to be used for validation and updating of finite element models for scenario simulation and structural health monitoring. The exercise was conducted as part of a project aimed at developing online diagnosis capabilities for three landmark European suspension bridges.
Ten stand-alone tri-axial acceleration recorders were deployed at locations along all three spans and in all four pylons during five days of consecutive one-hour recordings. Time series segments from the recorders were merged, and several operational modal analysis techniques were used to analyse these data and assemble modal models representing the global behaviour of the bridge in all three dimensions for all components of the structure.
The paper describes the equipment and procedures used for the exercise, compares the operational modal analysis (OMA) technology used for system identification and presents modal parameters for key vibration modes of the complete structure.
The results obtained using three techniques, natural excitation technique/eigensystem realisation algorithm, stochastic subspace identification and poly-Least Squares Frequency Domain method, are compared among themselves and with those obtained from a 1985 test of the bridge, showing few significant modal parameter changes over 23 years in cases where direct comparison is possible.
The measurement system and the much more sophisticated OMA technology used in the present test show clear advantages necessary due to the compressed timescales compared to the earlier exercise. Even so, the parameter estimates exhibit significant variability between different methods and variations of the same method, while also varying in time and having inherent variability.
AbstractShake-table response of a 33.6-m-long (110-ft-long), four-span, RC bridge model with a continuous posttensioned superstructure supported on three, two-column bents was studied under ...horizontal bidirectional coherent simulated earthquakes. The pier heights varied, introducing a slight asymmetry about the centerline of the bridge model. The superstructure ends were supported on seat-type abutments that were connected to hydraulic actuators simulating abutment movements. The skew angle was zero. The bridge model was subjected to successive motions simulating a modified version of a record from the 1994 Northridge Earthquake. Results showed that damage was concentrated in plastic hinge regions of the columns and that the pier caps and the superstructure remained essentially elastic. The shortest pier failed, but this pier continued to carry vertical loads, and the bridge did not collapse. Despite the lack of skew, the superstructure-abutment interaction led to large in-plane rotations that caused significant residual displacements in the piers.
Many researchers have conducted comprehensive experimental and numerical investigations to examine civilian structures’ response to explosive loads. Most of the studies reported in the literature ...deal with building structures and structure components. Studies of bridge structures subjected to blast loads are limited. This study performs numerical simulations of dynamic responses of a large cable-stayed bridge under explosive loadings. All numerical simulations are carried out using the LS-DYNA explicit finite element code. This paper describes the bridge under consideration, blast load estimation, finite element model, material model, and detailed numerical simulation results of the bridge to blast loads from a 1000 kg TNT equivalent explosion at 0.5 m from the bridge tower and pier, and 1.0 m above the deck. Damage mechanism and severity of the bridge tower, pier and deck are examined. The companion paper Hao and Tang (2010)
19 presents intensive numerical simulation results of the bridge components under blast loads of different scaled distances, progressive collapse analyses of the bridge after either one of the four main bridge components is damaged, and the safe scaled distance for bridge protection before initiating catastrophic collapse. The effectiveness of FRP strengthening of bridge concrete back span for blast load resistance is also investigated.
•Wave load effects of a floating bridge in a fjord were analyzed.•A method was proposed to account for inhomogeneous wave conditions.•Inhomogeneous wave conditions were assumed based on field ...measurements and numerical simulations.•The effect of inhomogeneity is found to differ for various response variables.•Proper description of inhomogeneous wave filed is important.
When designing a floating bridge crossing a deep and wide fjord, a homogeneous wave field is usually assumed for simplicity. However, waves in fjords are commonly inhomogeneous, and hence the mentioned design practice introduces uncertainty, which should be assessed for the design. In this study, we proposed an approach to account for the inhomogeneous wave load effect on a floating bridge and applied it on a floating bridge that was initially proposed for crossing the Bjørnafjorden. The floating bridge considered is end-anchored, about 4600 m long and consists of a cable-stayed high bridge and a low bridge supported by 19 pontoons. Wave excitation loads on each pontoon were proposed to be modeled and applied separately to account for inhomogeneous waves. By considering 1-year and 100-year wave conditions, dynamic responses of the floating bridge subjected to homogeneous and inhomogeneous waves were analyzed and compared. It is found that inhomogeneous waves cause relatively larger sway motion, axial force, and strong axis bending moment, as well as significantly larger weak axis bending moment along the bridge girder than homogeneous waves. These responses depend on the inhomogeneity level of waves considered. Proper description of the wave field is therefore very important for evaluating the effect of inhomogeneous waves and associated uncertainties.
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•A pedestrian swing bridge with glass fibre-reinforced polymer deck was designed.•Construction stages were suitably studied to reduce the overall deformability.•Structural analysis ...and verifications were conducted according to current standards.•A small-sized electric motor will be sufficient to move the lightweight structure.•Savings in installation, operational, and maintenance costs are expected.
The paper illustrates the feasibility study of a cable-stayed, pedestrian, swing bridge crossing the Navicelli Canal in Pisa, Italy. The static scheme of the bridge is asymmetric with one tower and three pairs of stays. The maximum span length is 21.26 m and the useful width is 2.50 m. According to the proposed design, the bridge deck will be made of glass fibre-reinforced polymer pultruded profiles; the tower and stays will be of ordinary steel; stainless steel bolts and plates will be used for the connections. A finite element model of the bridge was developed to analyse its structural behaviour during construction, service life, and maintenance operations. Construction stages – with particular attention to the cable stringing procedure – were carefully studied to help reduce the overall deformability of the bridge. Structural verifications were carried out according to the EuroComp Design Code, Italian CNR instructions, and German DIBt specifications. The calculated total weight of the bridge deck is about 11 t, including non-structural elements. Thanks to the low self-weight of the deck, a 3 kW electric motor will be sufficient for movement, with savings in both installation and operational costs with respect to a full steel bridge.
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