Response Of Piers Research Articles

Experimental study on the behavior of precast segmental piers under ship impact loading

This paper is to study the difference of anti-collision performance between precast segmental piers and conventional monolithic reinforced concrete (RC) piers. A reduced scale model was used, and the dynamic responses of piers with different structures under impact were compared and analyzed. The nonlinear finite element (FE) model of pier impact was established and numerical simulation of the impact responses and the failure mode of piers was carried out. The research results indicated that under impact, the failure mode of monolithic pier is tension bending failure, and for the segmental piers, the shear slip and concrete crushing in the impact segment occur mainly. The test results also indicated that the segmental piers are more flexible than monolithic piers, which leads to the peak impact force of the segmental pier reduced by 21.25% and 6.55%, respectively, under the impact of rigid head and ship bow compared to that on the monolithic pier. The study also found that segmented piers have better deformation capability and less residual displacement, but fail to show good self-reset capability. The results of FE calculation match well with the test results, which verifies the applicability and reliability of the FE model used in this paper.

Structural Systems Comparison of Simply Supported PSC Box Girder Bridge Equipped with Elastomeric Rubber Bearing and Lead Rubber Bearing

This study compares the influence of elastomeric rubber bearing (ERB) as the regular bearing support and lead rubber bearing (LRB) as the seismic isolation device on the seismic performance of a seven-span simply supported prestressed concrete (PSC) box girder bridge, which was analyzed using nonlinear time history analysis (NLTHA) with the OpenSees software. The results showed that the maximum pier responses and damage were smaller in models with LRB than with ERB. The bridge model using ERB occurred the slightest damage at levels II, while the one using LRB was at levels I. In addition, the highest seismic performance level in the model with ERB was at the operational limit. Meanwhile, the seismic performance in the model with LRB was at the fully operational limit. Thus, LRB was a good preference for improving the seismic performance and mitigating the damage due to the seismic excitation with a slender pier.

Response of piers installed in sand near sloping ground under inclined loading

Response of piers installed in sand near sloping ground under inclined loading

A simple numerical approach for the pushover analysis of slender cantilever bridge piers taking into account geometric nonlinearity

The response of slender bridge piers to horizontal actions may be significantly influenced by geometric nonlinearities. In such conditions, the use of sophisticated models implemented in complex structural analysis software can be economically disadvantageous, especially in the preliminary design phases. This paper proposes a simple numerical procedure to compute the nonlinear pushover response of cantilever bridge piers subject to horizontal loads. The procedure is based on an iterative approach to enforce the element equilibrium under large displacements, efficiently accounting for P-Delta effects induced by vertical loads. Evaluation of the bending moment–curvature response of the pier base cross section is required and used as basic input data. For fast preliminary analyses, sectional response can be manually computed in simplified linearized form, thus completely eliminating the need to use structural analysis software. Indeed, the entire procedure can be implemented in standard programming codes, such as PythonTM or Matlab®, and used to evaluate the pushover response of piers with arbitrary cross section. Comparison with experimental test results and solutions based on Finite Element models shows that proposed procedure can be used to get a fast, yet accurate, estimate of the entire force–displacement curve and, in particular, of the pier ultimate displacement.

Seismic response sensitivity of a V-shaped canyon-crossing bridge considering the near-source canyon topographic effects

Past seismic events have shown that the canyon-crossing bridges are more vulnerable due to the canyon topographic effects. The seismic responses of such bridges are affected by various influential factors, including source-to-canyon distance, depth-to-half-width ratio of the canyon, incident angle of the ground motion, and shear wave velocity. This study numerically examines the impacts of these factors on the seismic responses of a typical bridge across a V-shaped canyon, which are not adequately investigated in the existing literature. To represent the canyon topographic effects, the ground motions at each bridge pier location are synthesized by the scattering and diffraction models of seismic waves induced by the V-shaped canyon. The accuracy of the analytical model in describing the effect of the source location has been validated. A detailed parametric analysis is conducted to evaluate the importance of the main influential factors in the seismic design of the bridge. The results demonstrated that the incident angle and depth-to-half-width ratio result in significant effects on the bridge responses. When the incident angle is larger than 45°, the topographic amplification effect on the bridge responses should be considered in the seismic design of the bridge. The source location and soil property show certain influences on the seismic responses of the piers. The deep canyon can cause much higher bridge responses than the shallow canyon. When the depth-to-half-width ratio is larger than 0.4, the topographic irregularities can cause noticeable amplifications on the pier responses at the illuminated canyon side. After the earthquake events, the bearings experience noticeable residual deformations under the seismic waves with unequal amplitudes and phases induced by the local topography.

A quasi-tuned-mass-damper design concept for mitigating the dynamic displacement demand of tall piers

For bridges with tall piers, how to control the excessive displacement at the top during base excitation is a difficult problem. Related research has involved additional components and very high-cost requirements. A quasi-tuned-mass-damper (quasi-TMD) concept is proposed in current paper controlling dynamic displacement demand at the top of tall piers. The term ‘quasi’ here refers to the fact that the mechanics of this proposed concept is similar to TMDs, but it is realized in a different way. In this quasi-TMD system, the tall piers are considered as the primary structures and the girders are regarded as an additional mass block. Bearings between super- and sub-structures are utilized offering the required stiffness and damping. Since girders provide significantly greater mass ratio, new characters and problems may be encountered and should be solved compared with traditional TMDs. One of the most significant advantages of this quasi-TMD system is that none of additional components are required. While a more detailed design procedure should be conducted for bearings selecting optimal parameters. The equations of motion of tall piers with ground excitations are derived and solved in the frequency domain. A detailed analysis and optimization process are then presented. The case analysis of a typical tall pier bridge illustrates the efficiency of the proposed quasi-TMD in suppressing the response of tall piers excited by seismic motions. Since no additional sub-structure is needed and it is easy to design and implement, it is believed that the quasi-TMD proposed in this paper will attract widespread attention and interest.

Curvature response of bridge pier subjected to earthquake action in a saline soil environment

The curvature of bridge piers can be described in terms of their syntagmatic deformation in the cross-sectional tensile and compressive zones. In the present study, 12 reinforced concrete bridge piers were designed and cast. Two of them were control specimens without corrosion, while the other 10 were corroded by immersion in a saline solution through the application of an electrical current; pseudo-static tests were conducted on the bridge piers after corrosion. The failure modes, corrosion ratios of the rebars, and load–curvature backbone curves were obtained and discussed. The evolution in curvature, in relation to different axial forces and corrosion ratios, was compared and analysed. It was found that the effective diameter of the rebars was reduced by corrosion, resulting in considerable reductions in the expected deformability (curvature) of the bridge pier cross-section. A robust load–curvature model was derived based on classical lamination theory and by dividing the bridge pier cross-section into concrete and steel reinforcement bar layers. The modelled curvature values match the results of the pseudo-static tests well. The experimental data and model can help lay out improved guidelines for bridge design, particularly for the seismic design of bridge piers in saline soil environments.

Transverse seismic damage mode identification of deteriorating simply-supported highway bridges

The sliding of laminated rubber bearings (LRBs) and failure of shear keys observed in the Wenchuan earthquake significantly increase the span collapse risk of simply-supported highway bridges and contradict the ductile design philosophy recommended by the current design code in China. In the meantime, the seismic damage mode of bridges may also change with increasing service time due to environmental corrosion sustained by the ductile element of pier. It is well accepted that the change of bridge damage mode will cause the ineffectiveness of original seismic design. In order to identify transverse seismic damage modes of deteriorating simply-supported bridges, a five-span bridge is selected as the baseline bridge and a series of time-dependent models considering the chloride intrusion are developed. A methodology for identifying the seismic damage mode of the bridge system is proposed. Incremental dynamic analyses (IDAs) are performed to study the effects of service time and shear key capacity on seismic damage modes of the baseline bridge. To validate the results obtained from the baseline bridge, comparisons of the lifetime damage modes for several typical bridge configurations are conducted through the proposed methodology. The results indicate that with the increase of the service time of bridge, the displacement response of LRBs decreases slightly while the displacement ductility response of piers increases significantly under earthquakes, and the seismic damage mode of the bridge shows a trend of changing from displacement-oriented to strength-oriented or combined damage modes. On the other hand, the increase of shear key capacity can effectively prevent excessive girder movement but intensifies the damage level of piers under earthquakes, which is in accordance with the expectations of the ductile design philosophy. In conclusion, the combined effects of environmental corrosion and shear key capacity can significantly change the seismic damage modes of bridges along the transverse direction and thus should be considered carefully during the seismic design.

Structural robustness of an RC pier under repeated earthquakes

The seismic resilience of structures and infrastructures is affected by damage accumulation phenomena, mainly related to the type of hysteresis. Specifically, pinching drives the cyclic response of several building materials, such as reinforced concrete and masonry. Structural systems affected by pinching phenomena are prone to exhibit a dramatic increment of their displacement response after multiple cycles (e.g. repeated earthquakes). The authors estimate a reinforced concrete pier's response using truncated incremental dynamic analysis by concatenating three earthquake scenarios. The authors adopted a Bouc–Wen class hysteresis model to simulate the reinforced concrete pier's cyclic response, matching its experimental cyclic response. The current analysis proved that ductility and resistance primarily drive the seismic response after a single earthquake. However, the performance after multiple earthquakes strongly depends on the pinching, degradation and drift accumulation, which are generally neglected in standard design practices.

Study on reasonable restraint system of double-deck frame bridge subjected to seismic action

In this paper, in order to improve the seismic performance of frame type double deck overpass bridge under seismic action, the most reasonable restraint system of frame double-deck overpass is studied. Based on the typical frame-type double-deck continuous overpass-hushen bridge, the finite element analysis model of the solid bridge is established. Then, from six different directions, eight different constraint combinations are established. Finally, through the analysis of the bridge direction control point of the internal force, displacement and other parameters, research and contrast the frame double-deck overpass under different constraints of the seismic response. The results show that the combination of rubber bearing, steel wire rope and concrete block can effectively limit the relative displacement between piers and beams, and reduce the internal force response of Piers and residual deformation of supports.

Test for Influence of Socket Connection Structure on Dynamic Response of Prefabricated Pier under Vehicle Collision

In order to obtain the difference of anti-collision performance between the socket assembled bridge pier and integral bridge pier, this research conducted the model test of the bridge piers subjected to vehicle impact. The influence of the socket connection form and structure parameters such as embedment depth, interface roughness, and reserved hole opening size on the response of bridge piers to vehicle collision was analyzed by comparing them with those of the cast-in-place bridge pier. Results show that vehicle speed and socket depth are important factors affecting the dynamic response of socket bridge piers to vehicle crash. The maximum impact force on a bridge pier is obviously affected by the embedment depth of the pier column, but no clear change rule exists between them. The opening size of the reserved cavity affects the impact force slightly when the vehicle speed is low, but gradually increases with the increase in vehicle speed. The damage degree of the bridge pier gradually decreases with the increase in the embedment depth of the pier column and increases with the increase in vehicle speed. The acceleration of the bridge pier tends to increase with the vehicle speed, but no clear law of change with the socket depth exists. The maximum strain of the steel bar at the root of the socket pier is greater than that of the impact position, and the maximum strain distribution of the steel bars of the pier column with the socket embedment depth greater than or equal to 1.0 times diameter of the column is similar to that of the cast-in-place one. The maximum strain of steel bars of the both are at the root of the pier column. The study results provide a data reference for further studying the actual vehicle bumping on socket bridge pier and prefabricated bridge anti-collision design.

Effects of axial loads and higher order modes on the seismic response of tall bridge piers

Tall piers are essential components of the earthquake resisting system of bridges. The dynamic behaviour of tall piers differs significantly from that of short piers due to a number of factors, such as their high flexibility and inertia. This paper aims to quantify the influence of axial loads and higher order modes on the seismic response of bridges tall piers and to provide results useful for a more informed design and assessment. For this purpose, an analytical formulation of the dynamic problem, developed and validated in a previous study, is employed to analyse a wide range of piers and bridge configurations. In the first part of the paper, a thorough parametric investigation is carried out to evaluate the influence of axial loads and higher order modes on both the modal properties and the seismic response of tall piers with different geometries and vertical loads. Subsequently, three realistic case studies representing bridges with different geometrical, mechanical and dynamic conditions are analysed and seismic time-history analyses are performed to further investigate the problem. The obtained results provide useful insights into the seismic behaviour of bridges with tall piers, identify the relevant governing parameters and shed light on the accuracy of simplified approaches suggested by the Eurocode 8 to account for the second order effects.

Bi-directional implementation of multiple-slider surface bearing to girder bridges: simplified 3-D modelling and seismic performance assessment

The uplifting slide shoe (UPSS) bearing, consisting of multiple sliding surfaces, is a new type of bearing which has been proposed to achieve reduced displacement under strong earthquakes without losing advantage of the slide bearing to deal with the thermal effects on bridges girders. In the present study, bi-directional implementation of the UPSS devices is proposed to achieve effectiveness in controlling the bi-directional seismic response of girder bridges induced by bi-directional ground motions. A simplified multi-spring model of the bi-directional UPSS, considering the coupling effect of the friction mechanism and the geometric contact condition of the slider, is established to assess the bi-directional bridge response including the integrated nonlinear interaction between the longitudinal and transverse components. Numerical simulations demonstrate that the bi-directional UPSS is effective in reducing the pier response in the transverse direction compared with the conventional UPSS. The seismic performance of the bridge with the application of the bi-directional UPSS is shown to be superior to that of the functionally discrete bearing (FDB) systems in effectively reducing both the bearing displacement and the pier response ductility factor.

Three-dimensional finite element analyses for cyclic responses of precast segmental bridge piers accounting for bond-slip degradation

Precast segmental piers are attracting the bridge community due to the merits of faster construction speed, smaller site disruption and higher construction quality. Compared to numerous experimental studies, accurate finite element (FE) models to investigate seismic responses of precast piers are rather rare. Among them, an apparent insufficiency is ignorance or inappropriate treatment of bond behavior. To this end, a zero-thickness interface element is adapted between 1 D truss element (rebars) and solid element (concrete). The bond behavior is implemented within the interface element, especially the strength degradation subject to cyclic loading, which renders simulations more realistic. The models further incorporate the softened damage-plasticity model for concrete and Menegotto-Pinto model for rebars. Viscous regularization scheme is adopted to circumvent the convergence difficulty brought out by the strain softening. The 3 D FE models are validated by the experimental works recently performed by authors. All analyses are performed on Abaqus/Standard platform, with the implicit incremental-iterative Newton-Raphson algorithm. The source code (UEL subroutine) is disclosed on github to faciliate relevant researches.

Shaking table test study on seismic performance of UHPC rectangular hollow bridge pier

To study the seismic failure mode and dynamic response characteristics of ultra-high performance concrete (UHPC) rectangular hollow bridge pier under dynamic loads, the El Centro wave, Taft wave, and Northridge wave were selected as seismic excitation for the shaking table test. The responses such as natural frequency, damping ratio, acceleration-time and displacement–time curves were investigated and the results were compared with the finite element simulation results. At the same time, 8 finite element models (FEMs) of UHPC rectangular hollow bridge pier were established to explore the influence of longitudinal reinforcement ratio and stirrup ratio on the seismic performance of bridge piers. The results indicated that with the increase of peak ground acceleration (PGA), the damping ratio, acceleration, displacement and UHPC strain of the specimen increased, while the natural frequency and the dynamic amplification factor of the pier decreased gradually due to the accumulation of damage. The increase of longitudinal reinforcement ratio improves the ductility, and the increase of stirrup ratio enhances the constraint effect of core UHPC and ductility to a great extent, which leads to different acceleration, displacement and equivalent plastic strain response of bridge piers. On the whole, the stiffness of UHPC rectangular hollow bridge pier was degraded after the input of seismic wave, but the ultimate bearing capacity was not deteriorated. The overall seismic performance is superior. In areas with low seismic fortification intensity, the reinforcement ratio of UHPC rectangular hollow bridge piers can be appropriately reduced.

Seismic performance of fibre-reinforced polymer and steel double-reinforced bridge piers

The re-centring ability and durability of important bridges have been the main objectives in recent provisions of seismic design codes. To achieve better recoverability and durability for piers, this article presents a double-reinforced pier configuration, in which the outer layer is reinforced with fibre-reinforced polymer (FRP) rebar and the inner layer is reinforced with steel rebar. An equal flexural capacity design method was used to determine the double-reinforced configurations. The effects of the potentially influential design parameters on the seismic response of piers were studied and compared to those of conventional RC piers. The results show that the proposed design method can satisfy the ultimate capacity and durability demands. The double-reinforced piers had a better performance than conventional piers in terms of the ductility, post-yield stiffness and residual deformation. The maximum deformation and energy dissipation capacity of the double-reinforced piers were comparable to those of the conventional RC piers. The results also demonstrated that the proportion of steel reinforcement had a clear effect on the performance of double-reinforced piers. However, FRP reinforcement with a high modulus of elasticity should be avoided due to the adverse effect on ductility.

SHAKING TABLE TESTS ON THE SEISMIC RESPONSE CHARACTERISTICS OF DOUBLE-COLUMN PIERS WITH SHEAR BEAMS

Shaking table tests were carried out to study the influences of shear beams on the seismic response of double-column piers that were designed to support the girder of a full cable-stayed bridge model. The double-column pier with shear beams included two columns and five shear beams equally installed between the two columns. A full cable-stayed bridge model of 1/70-scale that included the pier (a double-column pier and a double-column pier with shear beams), tower, girder, pile group, and artificial soil was designed and tested on a shaking table array. The seismic response characteristics were compared between the double-column piers with and without shear beams when they were subjected to various earthquake waves of various frequency contents, such as the artificial, El Centro, and Mexico City waves. The experimental results show that the maximum strains at the bottom of the double-column pier with shear beams were less than those of the double-column pier under the artificial, El Centro wave, and Mexico City waves of various shaking amplitudes. The additional shear beams significantly mitigated the strain responses at the bottom of the double-column pier, and decentralized the inner force of the columns. The maximum accelerations at the bottom of the double-column pier with shear beams are 1.4-1.8 times those of the shaking table when the bridge model was subjected to the artificial, El Centro, and Mexico City waves with 0.1 g, 0.15 g, and 0.2 g. The pile-soil-structure interaction significantly affected the seismic response of the double-column pier with shear beams and increased its longitudinal acceleration responses. The seismic responses, such as the acceleration, displacement, and strain responses of the double-column pier with and without shear beams were significantly affected by the frequency spectral characteristics of the various earthquake waves. The extent of the influence was dependent on the relationship between the frequency contents of the earthquake waves and the frequency spectral characteristics of the piers.

Study on the influence of trains on the seismic response of high-speed railway structure under lateral uncertain earthquakes

At present, specific earthquake motion is often used for analyzing the influence of trains on high-speed railway structure; however, the uncertainty of earthquake motion is rarely taken into consideration. In this study, on the basis of considering the uncertainty of earthquake motion, and taking a simply-supported beam with CRTS II track system and CRH2 high-speed train in China as the research objects, a finite element analysis model of vehicle-bridge coupled model was established and verified by tests. The influencing mechanism of the trains on structural response under the action of uncertain earthquake was analyzed, and the range of the influence levels of trains on seismic response of structure was calculated. The research findings show that under the effect of earthquake, the presence of trains decreases the responses of piers and bearings, while increases the response of track structure. With increasing peak ground acceleration, the effect of trains on the track structure deformation increases, while that on the bending moment of piers, shearing force, and bearing deformation all decrease. The increase in train speed will not significantly affect the seismic response of structures. The ratio of seismic response between the operating conditions with and without vehicles was kept within a certain range, so that the demand range for seismic response under the operating condition with vehicles can be approximately simplified.

Wavelet-Based Analysis for Detection of Isolation Bearing Malfunction in a Continuous Multi-Span Girder Bridge

ABSTRACT This paper describes techniques for detecting bearing malfunction directly from the seismic response of the bridge using wavelet transform time-varying identification. Instantaneous frequency of continuous wavelet and detail components of discrete wavelet transform are utilized as structural features, and they characterize isolation bearing condition via statistical clustering technique. Accuracy and efficacy of the techniques were verified in numerical simulations using analytical and finite element models. The techniques were implemented on seismic records from long-term monitoring of multi-span continuous-girder isolated bridge. Results demonstrate that wavelet-based features can effectively characterize the condition of the isolation bearing directly from seismic responses of girder and piers.

Unified calculation model for the longitudinal fundamental frequency of continuous rigid frame bridge

The frequencies formulas of the bridge are of great importance in the design process since these formulas provide insight dynamic characteristics of the structure, which guides the designers to parametric analyses and the layout of the bridge in conceptual or preliminary design. Continuous rigid frame bridge is popular in the mountainous area. Mostly, this type of bridge was simplified either as a girder or cantilever when calculating the frequency, however, studies showed that the different configuration of the bridge made the problem more complex, and there is no unified fundamental calculation pattern for this kind of bridge. In this study, an empirical frequency equation is proposed as a function of pier's height, stiffness of pier and the weight of the structure. A unified fundamental frequency formula is presented based on the energy principle, then the typical continuous rigid frame bridge is investigated by finite element method (FEM) to study the dynamic characteristics of the structure, and then several key parameters are investigated on the effect of structural frequency. These parameters include the number, position and stiffness of the tie beam. Nonlinear regression analyses are conducted with a comprehensive statistical study from plenty of engineering structures. Finally, the proposed frequency equation is validated by field test results. The results show that the fundamental frequency of the continuous rigid frame bridge increases more than 15% when the tie beams are set, and it increases with the stiffness ratio of tie beam to pier. The results also show that the presented unified fundamental frequency has an error of 4.6% compared with the measured results. The investigation can predicate the approximate longitudinal fundamental frequency of continuous ridged frame bridge, which can provide reference for the seismic response and dynamic impact factor design of the pier.