Seismic Mitigation of Curved Continuous Girder Bridge Considering Collision Effect

Due to structural irregularity, curved bridgesaremore likely to cause non-uniform collisions and unseating between adjacent components when subjected to earthquakes. Based on the analysis of the collision response of curved bridges duringearthquakes, and according to the seismic characteristics of curved bridges, research was carried out on pounding mitigation and unseating prevention measures. A curved bridge with double column piers was taken as an engineering example, and a finite element model of curved bridges thatcould consider the non-uniform contact collision between adjacent components was built with ABAQUS software. Viscoelastic dampers, viscous dampers, and a lead rubber bearing were selected as the damping devices, and a steel wire rope-rubber mat was used as the pounding mitigation device to form the combinatorial seismic mitigation system. Based on the principle of energy dissipation combined with constraints, three kinds of combined seismic mitigation case were determined; a seismic response analysis was then performed. The results indicated that the three kinds of combined seismic case were effective atreducing the response topounding force, stress, damage, girder torsion and displacement, and achieved the goals of seismic mitigation and unseating prevention.

A Golden Ratio for Shaping the Curve – Lessons Learned

<p>Can we establish the guidelines that make our designs into a success? Is there something like the Golden Ratio for shaping the curve? The Golden Ratio is a common mathematical ratio found in nature, which can be used to create pleasing, organic-looking compositions. This is used for the overall shape and proportions in bridge design. In our practice and in modern-day bridge design we see more and more curved bridges.</p><p>Especially with the rise of parametric design a whole world opened up for (more) complex curved designs. Curviness (either vertical, horizontal or both) is not just a nice aesthetic feature. We encounter design principles that need to be taken into account to get to the ultimate elegancy that we thrive for in our bridge design.</p><p>In our practice, shaping the curve of a bridge is a recurrent topic in the design process – from concept to realisation. From the forming of the (3D) <i>alignment, </i>it’s about how curves fluidly connect. It’s all about the radius, diameter, arcs, splines, offsets and the way to connect with tangents and sinusoids. This is best shown by the Lucky Knot and the Zaligebrug by NEXT architects. We also experienced the difficulties during construction phase and learned to control dealing with the unexpected.</p><p>With a series of case studies from our own bridges we show the importance of precision in shaping curves to make a design that is both natural and understandable to the eye of the user. If done right, curves seem logic and right; but if done improperly, it ends up as a disaster.</p>

Load Distribution Factors for Curved Concrete Slab-on-Steel I-Girder Bridges

The use of complex interchanges in modern highway urban systems have increased recently in addition to the desire to conform to existing terrain; both have led to increase the demand for horizontally curved bridges. One type of curved bridges consists of composite concrete deck over steel I-girders which has been the preferred choice due to its simplicity in fabrication, transportation and erection. Although horizontally curved steel bridges constitute roughly one-third of all steel bridges being erected today, their structural behavior still not well understood. Due to its geometry, simple presence of curvature in curved bridges produces non uniform torsion and consequently, lateral bending moment (warping or bi-moment) in the girder flanges. The presence of the lateral bending moments would significantly complicate the analysis and the design of the structure. Hence, a parametric study is required to scrutinize a simplified method in designing horizontally curved steel I-girder bridges. A parametric study is conducted, using the finite-element analysis software "SAP2000", to examine the key parameters that may influence the load distribution on the curved composite steel girders. Based on the data generated from the parametric study, sets of empirical equations are developed for the moment and shear distribution factors for straight and curved steel I-girder bridges when subjected to the Canadian Highway Bridge Design Code (HCHBDC) truck loading.

Load Distribution Factors for Curved Concrete Slab-on-Steel I-Girder Bridges

The use of complex interchanges in modern highway urban systems have increased recently in addition to the desire to conform to existing terrain; both have led to increase the demand for horizontally curved bridges. One type of curved bridges consists of composite concrete deck over steel I-girders which has been the preferred choice due to its simplicity in fabrication, transportation and erection. Although horizontally curved steel bridges constitute roughly one-third of all steel bridges being erected today, their structural behavior still not well understood. Due to its geometry, simple presence of curvature in curved bridges produces non uniform torsion and consequently, lateral bending moment (warping or bi-moment) in the girder flanges. The presence of the lateral bending moments would significantly complicate the analysis and the design of the structure. Hence, a parametric study is required to scrutinize a simplified method in designing horizontally curved steel I-girder bridges. A parametric study is conducted, using the finite-element analysis software "SAP2000", to examine the key parameters that may influence the load distribution on the curved composite steel girders. Based on the data generated from the parametric study, sets of empirical equations are developed for the moment and shear distribution factors for straight and curved steel I-girder bridges when subjected to the Canadian Highway Bridge Design Code (HCHBDC) truck loading.

Free Vibration Analysis Of Horizontally Curved Composite Concrete Deck Over Steel I-Girder Bridges

Curved composite I-girder bridges provide an excellent solution to problems of urban congestion, traffic and pollution, but their behavior is quite complex due to the coupled bending and torsion response of the bridges. Moreover, dynamic behavior of curved bridges further complicates the problem. The majority of curved bridges today are designed using complex analytical methods; therefore, a clear need exists for simplified design methods in the form of empirical equations for the structural design parameters. In this thesis paper, a sensitivity study is conducted to examine the effect of various design parameters on the free-vibration response of curved composite I-girder bridges. To determine their fundamental frequency and corresponding mode shape an extensive parametric study is conducted on 336 straight and curved bridges. From the results of the parametric study, simple-to-use equations are developed to predict the fundamental frequency of curved composite I-girder bridges. It is shown that the developed equations are equally applicable to curved simply supported and composite multi-span bridges with equal span lengths.

Parametric study of curved steel I-girder bridges at construction phase.

The desire to conform to the existing terrain has largely increased the use of curved bridges for complex interchanges. Bridge curvature produces warping moments (lateral bending moments) in girder flanges under truck loading conditions and even during the construction phase. These warping moments increase girder flexural stresses at construction phase in case of un-shored construction. An extensive parametric study was conducted, using the finite-element analysis software "SAP2000", to examine the key parameters affecting warping stresses in curved girder bridges under construction loads. A strengthening technique "torsion box" at the girder supports was proposed and examined with respect to girder warping, flexural stresses and support reactions. The key parameters considered in this study included number of girders, girder spacing, number of cross bracing intervals, degree of curvature and girder span length. Based on this study empirical expressions for moment and shear distribution factors for the curved girder were developed.

Parametric study of curved steel I-girder bridges at construction phase.

The desire to conform to the existing terrain has largely increased the use of curved bridges for complex interchanges. Bridge curvature produces warping moments (lateral bending moments) in girder flanges under truck loading conditions and even during the construction phase. These warping moments increase girder flexural stresses at construction phase in case of un-shored construction. An extensive parametric study was conducted, using the finite-element analysis software "SAP2000", to examine the key parameters affecting warping stresses in curved girder bridges under construction loads. A strengthening technique "torsion box" at the girder supports was proposed and examined with respect to girder warping, flexural stresses and support reactions. The key parameters considered in this study included number of girders, girder spacing, number of cross bracing intervals, degree of curvature and girder span length. Based on this study empirical expressions for moment and shear distribution factors for the curved girder were developed.