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Design of Substructure
Published in Dongzhou Huang, Bo Hu, Concrete Segmental Bridges, 2020
The principal component of elastomeric bearings is a neoprene pad which distributes the loads from the super-structure to the substructure and accommodates the rotation and longitudinal movement of the super-structure. Neoprene pads are available with durometer hardness values ranging from 50 to 70. However, most current manufacturers are specifying a hardness value of 55±5. Typical material properties are listed in Table 11-1. For the neoprene pad with a hardness value of 55, its shear modulus can be taken as 150 psi. There are two types of elastomeric bearings: plain and laminated. In concrete segmental bridges, steel laminated elastomeric bearings are typically used due to the bridges' higher loads and greater thermal expansions. Their maximum vertical capacities are related to their sizes and typically can range up to 580 kips[11-7]. The components of a typical steel laminated elastomeric bearing and its dimensions are illustrated in Fig. 11-21. For steel laminated elastomeric bearings, the ratio of the shape factor to the number of interior layers of the elastomeric bearing should meet Si2n<22
Influence of properties of elastomeric bearings on dynamic behavior of an integral bridge under a seismic shock
Published in Alphose Zingoni, Insights and Innovations in Structural Engineering, Mechanics and Computation, 2016
Elastomeric bearings are commonly used in a wide range of applications where flexible structural support or vibration isolation is required. In recent decades they have become the preferred choice, being extensively applied in bridge design and retrofit in seismic zones (Buckle et al. 2002, Grant et al. 2004).
Fatigue of steel bridge infrastructure
Published in Hyun-Moo Koh, Dan M. Frangopol, Bridge Maintenance, Safety, Management, Health Monitoring and Informatics, 2008
Hyun-Moo Koh, Dan M. Frangopol
For SIBs subjected to far-field ground motions, the Isolator Displacements (IDs) generally have manageable magnitudes. However, for SIBs subjected to NF ground motions with directivity effect, the IDs tend to be considerably large. Thus, isolators, expansion joints and substructures with very large dimensions may be required for SIBs located in NF zones to accommodate such large IDs. Consequently, the application of seismic isolation to bridges in NF zones becomes virtually impractical as a stand-alone seismic mitigation technique. Although it may be possible to reduce the IDs and Substructure Forces (SFs) to manageable ranges by providing additional seismic control devices, most of such devices are generally expensive and are not commonly used for seismic protection of bridges, mainly due to the lack of experience with such devices and the associated maintenance cost. Thus, a rational solution to the problem associated with large IDs for SIBs subjected to NF earthquakes is required. To address the problem stated above, the efficiency of using Elastic Gap Devices (EGDs) in SIBs for reducing the IDs while keeping the SFs at reasonable ranges for a wide range of NF earthquake magnitudes is investigated. Elastomeric bearings placed in parallel with isolators between the superstructure and substructures that are engaged upon closure of a gap may be used for this purpose. Elastomeric bearings have already been used over many years by state departments of transportation and require only minimal initial cost and maintenance compared to most seismic control devices. Thus, they can easily be used for seismic design and retrofitting of SIB located in NF zones.
Investigation and treatment of bearing diseases for typical expressway and high-speed railway bridges in Eastern China: a field practice campaign
Published in Structure and Infrastructure Engineering, 2022
Fengbo Ma, Lu Zhang, Mida Cui, Xiaoxiang Cheng, Youquan Zou, Yi Cui, Gang Wu
Bearings can usually be classified into elastomeric bearings, pot bearings, spherical bearings, rocker bearings and roller bearings, according to their structural types (CEN, 2000). Elastomeric bearings, inlaid, bonded, and vulcanised by multilayer rubber and thin steel plates, are widely used in medium- and small-span highway bridges because of their advantages, such as simple structure, low cost, and easy installation and replacement (Heymsfield, Mcdonald, & Avent, 2001; Zheng et al., 2014). However, elastomeric bearings might easily be corroded due to their exposure to air, so their durability is often questionable (Heymsfield et al., 2001), and their design service life is usually 15 years at least (SAC, 2015). Pot bearings are composed of steel members and rubber, and they have the advantages of a large bearing capacity and flexible translational deformation. Therefore, they are ideal bearing types for long-span concrete bridges of HSRs before 2010 (Zhuang, 2015). Spherical bearings, due to their flexible rotating ability and the absence of low-temperature brittleness and degradation of rubber, are especially suitable for wide bridges, curved bridges and bridges in low-temperature areas (Kang, 2018; Zhuang, 2015). The design service life of pot/spherical bearing is usually more than 50 years (SAC, 2015).
Seismic Reliability Assessment of Typical Road Bridges in Hungary
Published in Journal of Earthquake Engineering, 2018
József Simon, László Gergely Vigh
The most commonly used bearing type is the elastomeric bearing. The behavior in the free horizontal direction can be characterized by a bilinear curve (Fig. 2c, material model 4). The stiffness of the elastomeric bearing is associated with the shear stiffness of the rubber bearing, while the shear capacity is calculated as the dynamic friction capacity considering a friction coefficient of 0.4 for concrete and 0.35 for steel surfaces [Caltrans, 2013]. In the fixed direction, the behavior is highly dependent on the actual configuration and restrainer components. Ultimate resistance of the bearings could be estimated from the design forces of the ultimate limit state; however, cyclic and even post-yielding behaviors are unpredictable without laboratory tests or detailed finite-element models. For this reason, a simplified modeling is followed: bearing stiffness is fully rigid in the restrained direction, while their failure is not incorporated in the model (infinite strength is assumed) (see Fig. 2c, material model 5). The same assumption applies for other CBs in this study. Note that the decreased stiffness due to yielding leads to lower seismic demands of the piers, abutments, and foundations; thus, it is a conservative approach with regard to these important components maintaining the structural integrity of the structure.
Probabilistic Seismic Performance Analysis of RC Bridges
Published in Journal of Earthquake Engineering, 2020
Araliya Mosleh, Jose Jara, Mehran S. Razzaghi, Humberto Varum
The abutments and backfill soil were modeled as elastic springs in the longitudinal and transverse directions according to the Caltrans recommendation [Caltrans, 2013]. Elastomeric bearings are located between the superstructure and substructure components, without any dowel or connecting device. The lateral and vertical stiffness of the elastomeric bearing, modeled as linear elastic springs, are [Priestley and Park, 1987]: