Skew bridges are known to be susceptible to girder unseating during earthquakes, and empirical equations for minimum support length are used in their design. To determine the degree of conservatism or un-conservatism in these equations, a rigorous model of a skewed bridge was developed in OpenSees and validated against a comprehensive dataset from shake table experiments. The validated model was then used to perform a parameter study on a series of single-span, simply supported, prototype bridges with seat-type abutments. Nonlinear response history analyses were performed that included impact and friction effects at the abutments and were repeated for both far-field and near-field motions. It was found that the additional support length required to prevent unseating is a linear function of skew angle over the range 0°–60° for both types of motions. This is contrary to common practice, which uses a quadratic function (American Association of State Highway and Transportation Officials, AASHTO) or the inverse of cosine of angle of skew (Federal Highway Administration (FHWA)). Consequently, common practice appears to be underestimating support length requirements by up to 50% at midrange skew angles of 30°–40°.
Abdel-MohtiA (2009) Seismic response assessment and recommendations for the design of skewed highway bridges. Doctoral Thesis, University of Nevada, Reno, NV.
2.
Abdel-MohtiAPekcanG (2013a) Assessment of seismic performance of skew reinforced concrete box girder bridges. International Journal of Advanced Structural Engineering5(1): 1–18.
3.
Abdel-MohtiAPekcanG (2013b) Effect of skew on the seismic vulnerability of RC box girder highway bridges. International Journal of Stability and Structural Dynamics13(6): 1350013.
4.
American Association of State Highway Transportation Officials (AASHTO) (2011) Guide Specifications for LRFD Seismic Bridge Design. 2nd ed.Washington, DC: AASHTO.
5.
American Association of State Highway Transportation Officials (AASHTO) (2012) AASHTO LRFD Bridge Design Specifications. 6th ed.Washington, DC: AASHTO.
6.
American Institute of Steel Construction (AISC) (2011) Steel Construction Manual. 14th ed.Chicago, IL: American Institute of Steel Construction.
7.
BjornssonS (1997) Seismic behavior of skew bridges. Doctoral Thesis, University of Washington, Seattle, WA.
8.
BuckleIGFriedlandIManderJMartinGNuttRPowerM (2006) Seismic retrofitting manual for highway structures part 1-bridges. Report no. FHWA-HRT-06-032, January. McLean, VA: Federal Highway Administration.
9.
BuckleIGHubeMChenGYenWAriasJ (2012) Structural performance of bridges in the offshore Maule Earthquake of 27 February, 2010. Earthquake Spectra28(1): 533–552.
10.
California Department of Transportation (Caltrans) (2013) Seismic Design Criteria. Version 1.7. Sacramento, CA: Caltrans.
11.
California Department of Transportation (Caltrans) (2017) Seismic Design Criteria (Draft Version). Version 2.0. Sacramento, CA: Caltrans.
12.
CatacoliSSVenturaCEFinnWDLTaiebatM (2014) In-plane rotational demands of skewed bridges due to earthquake induced pounding. In: Proceedings of the 10th national conference on earthquake engineering: Frontiers of earthquake engineering, Anchorage, AK, 21–25 July.
13.
ChenL (2012) Report on Highway Damage in the Wenchuan Earthquake. Beijing: China Communication Press.
14.
DeepuSPPrajapatKRay-ChaudhuriS (2014) Seismic vulnerability of skew bridges under bi-directional ground motions. Engineering Structures71: 150–160.
15.
DimitrakopoulosEG (2010) Analysis of a frictional oblique impact observed in skew bridges. Nonlinear Dynamics60(4): 575–595.
16.
DimitrakopoulosEG (2013) Nonsmooth analysis of the impact between successive skew bridge-segments. Nonlinear Dynamics74: 911–928.
17.
Eurocode 8 (2005) Design of Structures for Earthquake Resistance-Part 2: Bridges. London: British Standard.
18.
GhobarahAATsoWK (1974) Seismic analysis of skewed highway bridges with intermediate supports. Earthquake Engineering and Structural Dynamics2(3): 235–248.
19.
Japan Road Association (JRA) (2012) Specifications for Highway Bridges-Part V: Seismic Design. Tokyo: Japan Road Association.
20.
KavianiP (2011) Performance-based seismic assessment of skewed bridges. PhD Thesis, Department of Civil and Environmental Engineering, University of California, Irvine, CA.
21.
KavianiPZareianFTacirogluE (2012) Seismic behavior of reinforced concrete bridges with skew-angled seat-type abutments. Engineering Structures45: 137–150.
22.
KawashimaKUnjohSHoshikumaJIKosaK (2011) Damage of bridges due to the 2010 Maule Chile earthquake. Journal of Earthquake Engineering15(7): 1036–1068.
23.
KwonOSJeongSH (2013) Seismic displacement demands on skewed bridge decks supported on elastomeric bearings. Journal of Earthquake Engineering17: 998–1022.
24.
McKennaFFenvesGScottM (2016) OpenSees: Open System for Earthquake Engineering Simulation. Berkeley, CA: Pacific Earthquake Engineering Center. Available at: http://opensees.berkeley.edu (accessed 8 July 2017).
25.
MalekiS (2005) Seismic modeling of skewed bridges with elastomeric bearings and side retainers. Journal of Bridge Engineering10(4): 442–449.
26.
MalekiSBagheriS (2012) Seat width requirement for skewed bridges under seismic loads. Scientia Iranica21: 1471–1479.
27.
MaragakisEA (1985) A model for the rigid body motions of skew bridges. Report no. EERL 85-02, 17 January. Pasadena, CA: Caltech.
28.
MaragakisEAJenningsPC (1987) Analytical models for the rigid body motions of skew bridges. Earthquake Engineering and Structural Dynamics15(8): 923–944.
29.
MengJYLuiEM (2002) Refined stick model for dynamic analysis of skew highway bridges. Journal of Bridge Engineering7(3): 184–194.
30.
NilsonHDarwinDDolanCW (2010) Design of Concrete Structures. 14th ed.New York: McGraw-Hill Companies, Inc.
31.
Pacific Earthquake Engineering Research Center (PEER) (2016) PEER ground motion database. Available at: http://peer.berkeley.edu/nga/ (accessed 12 May 2016).
32.
ShamsabadiA (2007) Three-dimensional nonlinear seismic soil-abutment-foundation-structure interaction analysis of skewed bridges. PhD Thesis, University of Southern California, Los Angeles, CA.
WakefieldRRNazmyASBillingtonDP (1991) Analysis of seismic failure in skew RC bridge. Journal of Structural Engineering117(3): 972–986.
35.
WieserJ (2014) Experimental and analytical investigation of seismic bridge-abutment interaction in a curved highway bridge. PhD Thesis, University of Nevada, Reno, NV.
36.
WuS (2016) Effect of skew on seismic performance of bridges with seat-type abutments. Doctoral Thesis, University of Nevada, Reno, NV.
37.
WuS (2019) Unseating mechanism of a skew bridge with seat-type abutments and a simplified method for estimating its support length requirement. Engineering Structures191: 194–205.
38.
WuSBuckleIGItaniA (2016) Effect of skew on seismic performance of bridges with seat-type abutments. Report no. CCEER-16-08, 12 January. Reno, NV: Center for Civil Engineering Earthquake Research, University of Nevada.
39.
WuSBuckleIGItaniAMIstratiD (2019a) Experimental datasets from large-scale shake table experiments on skew bridges. Epub ahead of print14 January. DOI: 10.17605/OSF.IO/2Q3DP.
40.
WuSBuckleIGItaniAMIstratiD (2019b) Experimental study on seismic response of skew bridges with seat-type abutments. I: Shake table experiments. Journal of Bridge Engineering24(10): 04019096.
41.
WuSBuckleIGItaniAMIstratiD (2019c) Experimental study on seismic response of skew bridges with seat-type abutments. II: Results. Journal of Bridge Engineering24(10): 04019097.
42.
ZakeriBAmiriGG (2014) Probabilistic performance assessment of retrofitted skewed multi-span continuous concrete I-girder bridges. Journal of Earthquake Engineering18: 945–963.
