scholarly journals Study on the additional support length requirements of single-span bridges due to skew using a simplified method

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Suiwen Wu ◽  
Junfeng Jia ◽  
Chiyu Jiao ◽  
Junfei Huang ◽  
Jianzhong Li
Keyword(s):  
Aspect Ratio ◽  
Response Spectrum ◽  
Skew Angle ◽  
Empirical Formulas ◽  
Design Response Spectrum ◽  
Skew Bridges ◽  
Simplified Method ◽  
Additional Support ◽  
Linear Manner ◽  
Support Length

AbstractSkew bridges with seat-type abutments are frequently unseated in earthquakes due to large transverse displacements at their acute corners. It is believed these large displacements are due to in-plane rotation of the superstructure. Lack of detailed guidelines for modeling of skew bridges, many current design codes give empirical expressions rather than theoretical solutions for the additional support length required in skew bridges to prevent unseating. In this paper, a parametric study has been carried out to study the influence of skew angle, aspect ratio and fundamental periods of bridges on the additional support length requirements of single-span bridges due to skew using a shake table experiment validated Simplified Method, which is capable of simulating gap closure based on response spectrum analysis. This method is developed based on the premise that the obtuse corner of the superstructure engages the adjacent back wall during lateral loading and rotates about this corner until the loading reverses direction. A design response spectrum specified in AASHTO LRFD Specifications was employed to represent the design-level earthquakes. The results show the additional length required to prevent unseating due to skew increases with the skew angle in an approximately linear manner when the angle is less than a critical value and decreases for angles above this value. This critical skew angle increases with the aspect ratio approximately in a linear manner and shows negligible dependence on the fundamental periods of the bridges, and combination of span length and width. In addition, the critical skew angle varies between 58° and 66°, when the aspect ratio is varied from 3.0 to 5.0. The results also show that the empirical formulas for minimum support length requirements of skew bridges in current codes and specifications can not accurately reflect the influence of skew.

Effect of skew on the minimum support length requirements of single-span bridges with seat-type abutments

2020 ◽  
Vol 36 (3) ◽  
pp. 1119-1140
Author(s):  
Suiwen Wu ◽  
Ian G Buckle
Keyword(s):  
Near Field ◽  
Quadratic Function ◽  
Parameter Study ◽  
Skew Angle ◽  
Minimum Support ◽  
State Highway ◽  
Rigorous Model ◽  
Additional Support ◽  
Shake Table Experiments ◽  
Support Length

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°.

Study on Dynamic Characteristic and Seismic Response of Long-Span Suspension Bridge with 1960 MPa Cable Wire

2016 ◽  
Vol 858 ◽  
pp. 157-162 ◽  
Author(s):  
Hao Lei Wang ◽  
Feng Jie Ma ◽  
Chao Zhu
Keyword(s):  
Dynamic Characteristic ◽  
Seismic Response ◽  
Response Spectrum ◽  
Water Channel ◽  
Suspension Bridge ◽  
Viscous Damper ◽  
Vibration Period ◽  
Long Span ◽  
Design Response Spectrum ◽  
Cable Wire

In order to break through the limitation of the width of river, depth of water, channel and etc., it is an optimal choice to construct a long-span suspension bridge. In a suspension bridge, the main cable is the major bearing member; and the use of super high strength cable wire can lighten the dead weight and obtain an economical design. 1960 Mpa cable wire is adopted by an under-construction suspension bridge, namely Ni-Zhou Channel Bridge, for the first time in China. In this paper, taking the Ni-Zhou Channel Bridge as a case-study, comparative analyses on dynamic characteristic and seismic response of long-span suspension bridge with 1960 Mpa cable wire are performed. Firstly, dynamic calculating model for Ni-Zhou Channel Bridge is built and its dynamic characteristics are studied; then by using response spectrum and time history analysis method, seismic response of Ni-Zhou Channel Bridge is investigated on the basis of design response spectrum and artificial seismic ground motions; finally, the energy dissipation performances of a seismic protection devices (viscous damper) are also discussed. The results show that long-span suspension bridge with 1960 Mpa cable wire has a longer natural vibration period; the use of viscous damper can effectively reduce the peak value of bending moment in stiffening girder. This paper can provide references for the project’s construction.

scholarly journals Implementation of the structural performance factor (Sp) within a displacement-based design framework

2018 ◽  
Vol 51 (3) ◽  
pp. 159-165 ◽  
Author(s):  
Dion Marriott
Keyword(s):  
Response Spectrum ◽  
Time History ◽  
Structural Performance ◽  
Integration Time ◽  
Design Framework ◽  
Base Shear ◽  
Structural Behaviour ◽  
Performance Factor ◽  
Design Response Spectrum ◽  
Displacement Based

This paper discusses the application of the Structural Performance factor (SP) within a Direct Displacement-Based Design framework (Direct-DBD). As stated within the New Zealand loadings standard, NZS1170.5:2004 [1], the SP factor is a base shear multiplier (reduction factor) for ductile structures, i.e. as the design ductility increases, the SP factor reduces. The SP factor is intended to acknowledge the better-than-expected structural behaviour of ductile systems (both strength, and ductility capacity) by accounting for attributes of response that designers are unable to reliably estimate. The SP factor also recognizes the less dependable seismic performance of non-ductile structures, by permitting less of a reduction (a larger SP factor) for non-ductile structures. Within a traditional force-based design framework the SP factor can be applied to either the design response spectrum (a seismic hazard/demand multiplier), or as a base shear multiplier at the end of design (structural capacity multiplier) – either of these two approaches will yield an identical design in terms of the required design base shear and computed ULS displacement/drift demands. However, these two approaches yield very different outcomes within a Direct-DBD framework – in particular, if SP is applied to the seismic demand, the design base shear is effectively multiplied by (SP)2 (i.e. a two-fold reduction). This paper presents a “DBD-corrected” SP factor to be applied to the design response spectrum in Direct-DBD in order to achieve the intent of the SP factor as it applies to force-based design. The proposed DBD-corrected SP factor is attractive in that it is identical to the SP relationship applied to the elastic site hazard spectrum C(T) for numerical integration time history method of analysis within NZS 1170.5:2004 [1], SP,DDBD = (1+SP)/2.

scholarly journals Basin Resonance and Seismic Hazard for Jakarta, Indonesia

2018 ◽  
Author(s):  
Athanasius Cipta ◽  
Phil Cummins ◽  
Masyhur Irsyam ◽  
Sri Hidayati
Keyword(s):  
Ground Motion ◽  
Seismic Waves ◽  
Response Spectrum ◽  
Capital City ◽  
Earthquake Ground Motion ◽  
Computational Domain ◽  
Near Surface ◽  
Earthquake Scenario ◽  
Design Response Spectrum ◽  
Intraslab Earthquake

We use earthquake ground motion modelling via Ground Motion Prediction Equations (GMPEs) and numerical simulation of seismic waves to consider the effects of site amplification and basin resonance in Jakarta, the capital city of Indonesia. While spectral accelerations at short periods are sensitive to near-surface conditions (i.e., Vs30), our results suggest that, for basins as deep as Jakarta’s, available GMPEs cannot be relied upon to accurately estimate the effect of basin depth on ground motions at long periods (>1 s). Amplitudes at such long periods are influenced by entrapment of seismic waves in the basin, resulting in longer duration of strong ground motion, and interference between incoming and reflected waves as well as focusing at basin edges may amplify seismic waves. In order to simulate such phenomena in detail, a basin model derived from a previous study is used as a computational domain for deterministic earthquake scenario modeling in a 2-dimensional cross-section. A Mw 9.0 megathrust, a Mw 6.5 crustal thrust and a Mw 7.0 instraslab earthquake are chosen as scenario events that pose credible threats to Jakarta, and the interactions with the basin of seismic waves generated by these events were simulated. The highest PGV amplifications are recorded at sites near the middle of the basin and near its southern edge, with maximum amplifications of PGV in the horizontal component of 200% for the crustal, 600% for the megathrust and 335% for the deep intraslab earthquake scenario, respectively. We find that the levels of ground motion response spectral acceleration fall below those of the 2012 Indonesian building Codes's design response spectrum for short periods (< 1 s), but closely approach or may even exceed these levels for longer periods.

Post-Yielding Behavior of Hinge-Supported Wall with Buckling-Restrained Braces in Base

2019 ◽  
Vol 13 (03n04) ◽  
pp. 1940003 ◽  
Author(s):  
Xiaoyan Yang ◽  
Jing Wu ◽  
Jian Zhang ◽  
Yulong Feng
Keyword(s):  
Response Spectrum ◽  
Time History ◽  
Shear Wall ◽  
Seismic Intensity ◽  
Nonlinear Time History Analysis ◽  
Wall Structure ◽  
Superposition Method ◽  
Structural Wall ◽  
Design Response Spectrum ◽  
Buckling Restrained Braces

A novel structural wall with hinge support and buckling restrained braces (BRBs) set in the base (HWBB) is studied. HWBB can be applied to precast manufacturing due to its considerable ductility and the separate loading mechanism in HWBB–frame structure. In elastic stage, BRBs play a brace role to make the hinged wall resist horizontal forces like a shear wall. BRBs dissipate seismic energy through plastic and hysteresis effects after yielding and the damage is only concentrated in BRBs. The performance of an HWBB is equivalent to a shear wall structure with excellent ductility and stable energy dissipation capacity. Numerical analysis indicates that the hinged wall body in the HWBB well controls the deformation mode of the structure, avoiding the concentration of story drifts, thereby protecting the remaining parts of the structure. It is revealed that the moments of the wall body will generate significant increments after BRBs yielding, and the Seismic Intensity Superposition Method is proposed to calculate the moments. In this method, nonlinear response of an HWBB can be regarded as the sum of the responses of two elastic corresponding structures excited with two parts of the seismic intensity, respectively. Modes and moments equations of the hinged wall with uniform distribution of stiffness and mass are derived, and calculation results coincide with that of the nonlinear time history analysis (NHA). For a more general case, the white noise scan method is proposed to solve the structure’s natural characteristics and to further calculate the response. Finally, the post-yielding moment calculation method and the process based on design response spectrum are proposed. It is proved that the moments from proposed Seismic Intensity Superposition Method can envelop most of the moments from NHA, and it is a good estimate of the response of HWBB in nonlinear stage.

scholarly journals Analysis of Offshore Structures Based on Response Spectrum of Ice Force

2019 ◽  
Vol 7 (11) ◽  
pp. 417 ◽  
Author(s):  
Liu ◽  
Li ◽  
Zhang
Keyword(s):  
Sea Ice ◽  
Large Scale ◽  
Response Spectrum ◽  
Time History ◽  
Offshore Structures ◽  
Potential Threat ◽  
Influence Coefficients ◽  
Design Response Spectrum ◽  
Ice Force ◽  
Bending Failure

With the development of large-scale offshore projects, sea ice is a potential threat to the safety of offshore structures. The main forms of damage to bottom-fixed offshore structures under sea ice are crushing failure and bending failure. Referred to as the concept of seismic response spectrums, the design response spectrum of offshore structures induced by the crushing and bending ice failure is presented. Selecting the Bohai Sea in China as an example, the sea areas were divided into different ice zones due to the different sea ice parameters. Based on the crushing and bending failure power spectral densities of ice force, a large amount of ice force time-history samples are firstly generated for each ice zone. The time-history of the maximum responses of a series of single degree of freedom systems with different natural frequencies under the ice force are calculated and subsequently, a response spectrum curve is obtained. Finally, by fitting all the response spectrum curves from different samples, the design response spectrum is generated for each ice zone. The ice force influence coefficients for crushing and bending failure are obtained, which can be used to estimate the stochastic sea ice force acting on a structure conveniently in a static way. A comparison of the proposed response spectrum method with the Monte Carlo method by a numerical example shows good agreement.

Buckling of laminated composite cylindrical skew panels

2015 ◽  
Vol 30 (9) ◽  
pp. 1175-1199
Author(s):  
Srinivasa Venkateshappa Chikkol ◽  
Prema Kumar Puttiah Wooday ◽  
Suresh Jayadevappa Yelaburgi
Keyword(s):  
Finite Element ◽  
Aspect Ratio ◽  
Laminated Composite ◽  
Buckling Load ◽  
Finite Element Solution ◽  
Element Solution ◽  
Skew Angle ◽  
Critical Buckling Load ◽  
Aluminum 7075 ◽  
Experimental Values

Experimental studies were made on isotropic cylindrical skew panels made of Aluminum 7075-T6 and laminated composite cylindrical skew panels under uniaxial compression. The experimental values of the critical buckling load ( Pcr) were determined using five different methods. The values of Pcr were also determined using MSC/Nastran and CQUAD8 finite element. The experimental values of the Pcr obtained by different methods were compared with the finite element solution. The effects of the skew angle and aspect ratio on the critical buckling load of isotropic cylindrical skew panels made of Aluminum 7075-T6 were studied. The effects of the skew angle, aspect ratio, and the laminate stacking sequence on the critical buckling load of laminated composite cylindrical skew panels were also studied. It is found that the method IV (based on a plot of applied load ( P) vs. average axial strain) yields the highest value for Pcr and method III (based on a plot of P vs. square of out-of-plane-deflection) the lowest value for Pcr. The experimental values given by method IV are seen to be closest to the finite element solution, the discrepancy being in the range of 5–23% for laminated composite cylindrical skew panels. For isotropic panels, it is found that the value Pcr initially increases with an increase in the skew angle and later decreases as the skew angle increases beyond 15°. For laminated composite panels, the Pcr value decreases as the aspect ratio increases for all laminate stacking sequences.

Effects of Site Classification on Platform Value of Response Spectrum

2011 ◽  
Vol 378-379 ◽  
pp. 306-309
Author(s):  
Ping Li ◽  
Jing Shan Bo ◽  
Xiao Yun Guo ◽  
You Wei Sun ◽  
Yu Dong Zhang
Keyword(s):  
Ground Motion ◽  
Seismic Design ◽  
Wave Motion ◽  
Response Spectrum ◽  
Equivalent Linearization ◽  
Earthquake Response ◽  
Response Analysis ◽  
Site Classification ◽  
Earthquake Motion ◽  
Design Response Spectrum

Regarding the design response spectrum in the code for seismic design of buildings as target spectra，the 28 acceleration histories are formed artificially．They are used as the inputs ground motion in earthquake response analysis．Four site classifications profiles were selected or constructed from practical site profiles．With the use of 1-D equivalent linearization wave motion method that is wildly used at present in site seismic response analysis, the platform values of surface response spectrum for different profiles under different ground motion inputs were calculated．Different platform values of the response spectrum and relational expression which is seven input earthquake motion intensity and site classifications have been given by statistical analysis.

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