Pier Models Research Articles

Seismic performance analysis of self-centering segment piers with mortise-tenon shear connectors based on cyclic pseudo-static test

In the past decades, more and more precast piers have been used in actual engineering, which brings convenience in construction and standardization of production. However, precast piers still have some shortcomings, such as shear slip between segments and poor energy dissipation. Thus, a self-centering mortise-tenon segmental bridge pier was proposed in this paper. To research the seismic performance of the self-centering mortise-tenon segment piers, three scaled model piers with their scale ratio as 1:3 were designed and prefabricated, namely as a cast-in-place model pier (CP) and 2 self-centering mortise-tenon segment model piers (designated as MTSP1 and MTSP2) with the initial pretension of 1302 MPa and 1488 MPa, respectively. The cyclic pseudo-static tests of the three piers were carried out. The comparison analysis was made respecting to the test results including the damage form, hysteretic characteristics, skeleton curve, energy dissipation capacity, residual displacement and equivalent stiffness of the three specimens. It was shown that MTSP specimens had higher horizontal bearing capacity. While the yield load, ultimate load, displacement ductility coefficient and initial stiffness of MTSP1 and MTSP2 were higher than those of CP. The MTSP had better performance considering the above aspects. The mean value of the residual displacement of MTSP2 was lower than that of CP 21.14 % and 29. 72 % respectively, as the drift ratio reaching 5 %. The MTSP specimens had better self-centering capacity due to the increased pretension stress which reducing the residual displacement greatly. The energy dissipation reinforcements improved the energy dissipation capacity of the segmental assembled piers. Based on the ABAQUS model, the numerical simulation was carried out and compared with the experimental data. MTSP had great energy dissipation capacity and self-centering capacity. It was suggested that MTSP should be used to make up for the deficiency of segmental assembled pier and improve the seismic performance of segmental assembled pier.

Experimental and numerical study on seismic behavior of a self-centering railway bridge pier

This study mainly focuses on experimental and numerical investigation of the isolation mechanism and seismic performance of a self-centering railway bridge pier. To begin, a 1/25 scale typical self-centering railway pier model was designed and constructed, which consisted of a gravity pier, a spread foundation and a pedestal. The gravity pier was rigidly connected to the spread foundation, which was then directly seated at the top of the pile cap to allow the uplift of the pier during strong earthquakes. The model was tested in a pseudo-static manner under constant axial load and cyclic lateral load to characterize its seismic performance. It was found that the lateral load, the bending moment at the pier bottom, and the width of compression zone at the bottom of pier remained essentially constant when the uplift reached a certain extent. The hysteretic curves were in inverse 'Z' shape with narrow loops indicating good self-centering effect but poor energy dissipation. This means that the lateral force-displacement relationship of this type of piers can be simplified as an elasto-plastic curve and they should be used along with additional energy-dissipation devices. Upon the test results, a two-spring model was proposed and developed in the OpenSees platform to represent the test model, which was analyzed using the test load history. The results indicate that the two-spring model can simulate the pseudo-static test with high precision. This modeling technique hence can be employed to analyze seismic response of this type of bridge piers.

Flow Characteristics and Scour Depth in Lenticular Shaped Pier: Case Study at Ciujung Bridge, Banten

Pier is part of the structure under the bridge. The existence of a pier in the river flow causes changes in river flow patterns. Changes in the flow pattern will result in local scouring around the pier. This study aims to determine the effect of the shape of the pier on the potential for local scour that occurs around the pier, and the flow characteristics around the pier. This studymodelled the existing conditions of the Ciujung Bridge, where the Ciujung Bridge uses an oblong pier shape, and the shape will be replaced with a lenticular model pier. FLOW-3D (CFD) software will be used to modelled flow characteristics and the depth of scour that occurs.

Study On The Vibration Amplitudes Of Reinforced Concrete Bridge Piers Using ABAQUS Software

The Dynamic characteristics such as damping ratio and natural frequency are an important indicator for predicting the dynamic behavior of bridges, but it is customary during the design that the designer assess the dynamic properties of the dynamic analysis because it is very difficult to determine the damping of the origin before construction and damping is taken as a predetermined constant value independent of the response amplitude and frequency of the structure. In the dynamic analysis of constructions design some experimental research has been concerned with the determination of dynamic structural properties and their relationship with the response amplitude experimentally, but the changes in dynamic properties with vibration amplitude has never been taken During dynamic analysis, further analytical treatments and computer modeling were required to study different cases based on the experimental results available by simulating them with a computer model. Dynamic characteristics are very essential to accurately determine the dynamic response, and it is necessary to study the effect of changes of the actual dynamic characteristics of bridges, which were determined by measuring their vibration in the results of dynamic analysis and comparing them with results that do not take into account the changes of dynamic properties and with laboratory results in order to assess the role of. Dynamic analysis inputs in simulating vibrations by monitoring their responses. As a result, it was found that the dynamic properties are independent of the shape of the external exactions. Also, it was concluded that relationships express the change of dynamic properties in terms of vibration amplitudes. And Similar reliance of the dynamic characteristics to the vibration amplitude is confirmed for the pier model, where the increase of the amplitude of the acceleration is accompanied by a decrease in the natural frequency, and an increase in the damping ratio is obvious. Before choosing design values when considering the dynamic characteristics of a structure, we need to give unique concentration to the predictable vibration amplitudes. Dynamic characteristics changes during dynamic analysis should be considered to produce analytical results that simulate experimental results and are closer to reality.

RESEARCH ON THE INFLUENCE OF MILD STEEL DAMPERS ON SEISMIC PERFORMANCE OF SELF-RESETTING PIER


 
 
 In order to improve the energy consumption capacity of the assembled self-resetting pier, the mild steel damper is added to the prefabricated self-resetting pier to form a prefabricated self- resetting pier with an external mild steel damper. Two sets of pier models were established by numerical simulation. On the basis of verifying the correctness of the traditional prefabricated self- resetting pier model, the two sets of pier models were subjected to low-cycle reciprocating loading to study the influence of the mild steel damper yield strength parameters and the pier axial compression ratio parameters on the seismic performance of the pier structure. The results show that compared with traditional prefabricated self-resetting piers, the hysteresis curve of self-resetting piers with mild steel dampers is fuller, and energy consumption and bearing capacity are greatly improved. With the increase of the yield strength of the mild steel damper, the energy consumption capacity will decrease when the loading displacement is less than 25mm, but the overall energy consumption capacity will increase. As the axial compression ratio of the pier column increases, the bearing capacity and energy consumption capacity of the structure increase significantly, but the impact is not obvious when the axial compression ratio exceeds 0.052.
 
 

Natural Frequencies of Model Piers under Different Ground Support Conditions

The natural frequency is critical for evaluating the integrity of bridge piers. However, the natural frequency of bridge piers can vary with the support condition of the ground. The aim of this study is to investigate the natural frequency of bridge piers under different ground conditions and at different embedded depths using a small-scale concrete pier. The model piers were fixed to asphalt concrete pavement using epoxy to simulate the rock site condition. Furthermore, model piers of different embedded depths were installed in a soil chamber with dimensions of 1.0 m × 1.0 m × 0.5 m to simulate weathered soil conditions. The upper part of the model pier was hit with a hammer having a rubber tip, and the acceleration signals were measured using three accelerometers installed at the upper, middle, and bottom parts of the model pier. Fast Fourier transforms were performed to analyze the natural frequencies of the model piers. The experimental results showed that the natural frequency under the fixed condition using epoxy was significantly higher than that under the unfixed condition. In the case of weathered soil conditions, three peak points appeared in the frequency domain. The natural frequencies measured at these three points increased with the embedded depth. The increment ratio of the natural frequency with the largest amplitude was significant. This study demonstrates that ground support conditions should be considered when evaluating the integrity of bridge piers through natural frequency analysis.

Dynamic response of different bridge piers

Throughout their construction period and service lifespan, the piers of bridges that built in earthquake zones are susceptible to abrupt earthquake. Thus, during their design period, all the possible circumstances must be taken into consideration because they are strategic infrastructures. Basically, the piers can be considered as the major part of the bridges. This paper presents an experimental work to investigate how the earthquakes influence on the seismic behavior of the selected concrete bridge piers. Physical modeling principals were applied to prepare three models of piers and table of shaking (1-g tests). The piers models were tested under 0.8g waveform for three cases, a rectangular pier constructed on a saturated cohesionless layer of soil, a hexagonal pier constructed over a saturated cohesionless layer and a circular pier installed on saturated cohesionless layer. The obtained results involved the time-acceleration measurement from the accelerometers throughout the shacking, the dynamic earth pressure, and the seismic displacement piers models. Basically, the obtained results of the experiments revealed that the acceleration amplification enhanced greatly at the pier top. The seismic displacement increased sharply because of the strong motion. The rectangular pier exhibited the highest values of the dynamic earth pressure.

A Numerical Case Study on Pier Shape Coefficient of Seismic Hydrodynamic Pressure in Design Codes

To study the pier shape coefficient of seismic hydrodynamic pressure, three waterpier coupling finite element models of piers with circular, rectangular and elliptical sections are built. The results numerically calculated with the same input ground motion show that the horizontally distributions of the hydrodynamic pressures from the vertical central lines to the edges of the three types of piers at a given depth are almost the same, the difference among the pressures on the three piers is mainly from the decreasing rate from the central line to the edge. The pressures decrease with the input direction from perpendicular to parallel. The result values of shape coefficients are close to the provisions in Japanese code, and those for circular and elliptical piers are slightly less than that stipulated in the code; and the coefficient values for rectangular pier are less than that in Euro code 8 and those for elliptical pier are in the range of the code.

Numerical modelling for a simplified bridge pier model under high-speed train passage over the bridge

In this work, we simplify a moving high-speed train as combination of a series of the axe loads from the front and rear bogies of cars. We build a simplified bridge pier model, as a result, train source expressions with cars moving on land and bridges are given respectively. Considering that the piers are inserted into the ground at a depth of a few tens meters and reach the bedrock. When the high-speed train passes the piers, the piers will appear oscillating motion which is subjugated by the ground, and this oscillating motion is relative to the microstructure interactions of subsoil and bedrock in the frame of the generalized continuum mechanics theory. Hence, we derive the elastic wave equations based on the modified couple stress theory to perform numerical modelling for a simplified bridge pier model under high-speed train passage over the bridge. Based on the wave equation and the train source expressions, a theoretical seismogram of a moving high-speed train with 16 cars on the bridge are obtained. Compared with the real data recorded when a high-speed train passed the piers in Dingxing County, some conclusions are drawn.

Dynamic behavior and damage mechanisms of reinforced concrete piers subjected to truck impact

In this paper, the dynamic behavior and damage mechanisms of reinforced concrete (RC) piers subjected to truck impact are investigated using finite-element (FE) simulations in LS-DYNA. Firstly, high-fidelity FE models of trucks and RC piers are established and verified against previous experimental data together with a real traffic accident. Then, an intensive parametric study is carried out to evaluate the effect of truck type on the impact force, failure mode, internal force, energy absorption, and reinforcement stress of RC piers. The simulation results show that the impact force is greatly affected by the structural stiffness and mass distribution of the trucks. Big differences exist in dynamic responses and failure modes of the piers under the impact of the different trucks. Besides, the concrete plays a dominant role in the energy absorption of the piers in the initial impact stage, and the energy dissipated by the reinforcements mainly depends on the lateral deformation of the pier in the following stage. Finally, two typical failure processes of RC piers subjected to truck impact are identified based on the interaction of shear and flexural responses.

Low cyclic loading tests and fatigue damage models of concrete bridge piers reinforced with high-strength rebar

Reinforced concrete bridge piers are extremely vulnerable to damage during long-duration ground excitations or main shock-aftershock type earthquakes due to accumulated damage caused by a great number of reversed excursions in elastic-plastic range. However, few studies on fatigue damage of piers can be found in literature. Low-cyclic loading tests of four identical RC bridge piers with high-strength rebar HRB600E (yield strength about 600 MPa) were carried out in this study. One of specimens was taken as the benchmark and was subjected to a conventional load protocol, and the rest was subjected to one, two and three times yield displacement, respectively. The research results showed that the fatigue strength of RC bridge piers tended to drop drastically at about ten cycles and then slowed down gently. It was found that strength degradation rate increased significantly with the displacement amplitude for fatigue tests while the fatigue life decreased dramatically with the displacement amplitude. In particular, when the cyclic loading displacement exceeded 2 times the yield displacement, the fatigue life dropped dramatically. Based on the experimental data, an exponential-type damage model was proposed with the peak lateral force at the first cycle as the coefficient, the cycle count as the base and factor of the loading displacement amplitude as the exponent, which could accurately predict the degraded lateral force of the bridge piers at different constant drifts. An accumulative fatigue damage index was established to evaluate the damage level of bridge piers.

Seismic Hydrodynamic Pressure on Concrete Bridge Pier with Submerged Depth from a Set of Shaking Table Model Tests

To study the variation of hydrodynamic pressure on concrete bridge pier with submerged depth in water, a series of shaking table model tests are completed recently. The result shows that the pressures increase with submerged depth obviously with a similar rate for all pier models, input direction combinations and total water depths. The hydrodynamic pressures and the rates increase with the total water depth and input intensity. The pressures on the three models with cross section, rectangular, elliptic and variable rectangular, are varied and different from the provision on the shape coefficient of pier in seismic design codes of highway bridges. The effect of the absorbing stuff adopted in the tests to reduce the potential reflection wave is not obvious. The result suggests to fix more sensors not only at central and but also along the edge lines, to examine the potential horizontal variation of pressures on upstream faces of the piers with different section shapes and the reflected wave must be eliminated with some new way in future test to close to the reality.

Study on Dynamic Behavior of Bridge Pier by Impact Load Test Considering Scour

In this study, for the establishment of a safety evaluation method, non-destructive tests were performed by developing a full-scale model pier and simulating scour on the ground adjacent to a field pier. The surcharge load (0–250 kN) was applied to the full-scale model pier to analyze the load’s effect on the stability. For analyzing the pier’s behavior according to the impact direction, an impact was applied in the bridge axis direction, pier length direction, and pier’s outside direction. The impact height corresponded to the top of the pier. A 1-m deep scour was simulated along one side of the ground, which was adjacent to the pier foundation. The acceleration was measured using accelerometers when an impact was applied. The natural frequency, according to the impact direction and surcharge load, was calculated using a fast Fourier transform (FFT). In addition, the first mode (vibratory), second mode (vibratory), and third modes (torsion) were analyzed according to the pier behavior using the phase difference, and the effect of the scour occurrence on the natural frequency was analyzed. The first mode was most affected by the surcharge load and scour. The stability of the pier can be determined using the second mode, and the direction of the scour can be determined using the third mode.

Effect of complex shape of pier foundation exposure on time development of scour

Local pier scour has been recognized as one of the most significant causes of bridge failures. Despite numerous studies on the subject of local pier scour have been conducted, there remain problems in accurate scour prediction because almost of the past studies have focused only on scour depth around simple shape of a bridge pier with or without considering their time development, even though prototype bridges usually have complex pier configurations. Thus, the objective of this study is investigation of the scour process around complex shape of pier including various shape of foundations and columns other than cylindrical shape over time for the purpose of understanding the relationships between hydraulic variables and resulting time development of scour. In this study, two field sites in Georgia, USA were selected, and corresponding scale-down bridge models and river geometries were fabricated in a hydraulic laboratory to address objectives of this study. Three different sizes of sediment and several geometric scales of bridge pier models were used to investigate the effect of relative sediment size, which is defined as the ratio of the pier width to the median sediment size. Through the visualization experiment, it is observed that exposure of complex shape of pier footing has important role for the temporal variations of scour depth over time. In addition to the quantitative visualization analysis, based on the experimental results, scouring rate formulas are suggested with the help of dimensionless, effective flow work concept according to the value of the relative sediment size. Findings in this research can be used to improve scour prediction methods that currently tend to overpredict bridge scour depth.

Mechanical performance study of the retractable pier column after stiffening

To solve the problem that the overlapping parts of a retractable pier column are prone to damage, this paper proposed the reinforcing measure of setting a stiffener ring at the bottom of the steel pipe. To study how the stiffener-ring parameters influence the mechanical properties of the pier column, 12 scale model specimens (including nine specimens with stiffener-ring widths of 40, 50, and 60 mm and three unstiffened comparison specimens) were tested under axial compression. Based on the test results, the specimen load–displacement, load–deflection, and load–strain curves were analyzed, and a finite-element model of a pier column under axial compression was established to determine the optimal stiffener size. The results show that setting a stiffener ring enhances the cooperative working ability between the steel pipe and the internal filling material and restrains the lateral deformation of the pier column, thereby improving the ultimate bearing capacity and overall stability of the pier column. The ultimate bearing capacity of the pier column is related to the width and thickness of the stiffener ring. The optimal size of the stiffener ring of the model pier column is 70 mm in width and 4 mm in thickness. The present research results provide a reference for designing compressible pier columns and column stiffening in mines and have important practical significance.

Using Rocking Frequencies of Bridge Piers for Scour Monitoring

In this study, scour-based vibrations of bridge piers are investigated using a bridge model in a water flume. First, the eigenmode corresponding to the measured frequencies of pier-like structures is identified. Second, the effect of the pier–deck interaction is studied. Finally, a theoretical model is proposed to characterize the pier vibration and identify its input parameters. To this end, experiments were conducted and a laboratory-scale model pier was tested in two configurations: single piers and two piers in a bridge configuration. The experimental results enable the identification of the modal shape and indicate that the deck decreases significantly the pier's frequency. In parallel, a theoretical model was proposed to model the pier, where the soil was modeled with both lateral springs along the pier and a rotational spring at the base. The spring stiffnesses were then identified using a three-dimensional finite element model. The results obtained from the theoretical and numerical models are in good agreement with the experimental results with the bridge pier in the two tested configurations. The obtained theoretical, numerical and experimental results were compared to experimental data found in the literature for further validation.

Vibration characteristics of spread foundation pier model with progress of local scouring

Vibration characteristics of spread foundation pier model with progress of local scouring

Seismic performance of bridge piers

The bridges that constructed in earthquake-prone areas perhaps subjected to sudden earthquake through their construction and service period. So, attentions should be pushed during bridge design specially, as they are one of the main civil infrastructures. The bridge piers are the main parts of bridges whether they are built across river or even as an express highway projects. This paper presented an experimental study of seismic performance of concrete bridge piers. Several important parameters have been studied such as acceleration response, seismic displacements, the bridge pier model settlement and the failure mechanism. Principles of physical modeling are used to fabricate two bridge pier models and shaking table (1-g tests) were performed under 0.82g waveform (i) Chamfered bridge pier built on saturated cohessionless soil (test-1) (ii) Oblong bridge pier built on saturated cohessionless soil(test-2). The output results included the acceleration response in term of the time acceleration and acceleration response spectra, failure mechanism during shacking, seismic displacement of the bridge pier model. The results show that the amplification in the acceleration is increases significantly at the top of the bridge pier. The seismic displacement is suddenly increased sharply due to strong motion. Overturning failure mechanism about the heel of the bridge pier has been observed in test-1 and test-2.

Hysteretic Mechanical Behaviour of an Eccentrically Loaded Partially-Concrete-Filled Steel Tubular Bridge Pier under Out-of-Plane Horizontal Cyclic Loading

To investigate the hysteretic behaviour of an eccentrically loaded partially-concrete-filled steel tubular (PCFST) bridge pier in an out-of-plane horizontal direction, a quasi-static experiment and finite element (FE) analysis of steel tubular columns were carried out. In this study, four PCFST column specimens were tested under constant eccentrically loaded and out-of-plane horizontal cyclic loading. The elasto-plastic behaviour and failure mode of these specimens were investigated. Secondly, the FE models of these four experimental PCFST columns were established, through comparisons with the experimental results, the validity of the selected elements, mesh division, the contact relationship between the concrete and the steel pipe, and the boundary conditions of FE models were verified. Thirdly, 30 FE models of PCFST bridge piers were analyzed to ascertain the effects of slenderness ratio λ, radius-thickness ratio Rt, and vertical load eccentricity ratio e/L on ultimate strength and ductility. Finally, an empirical formula was proposed to describe the ultimate strength and ductility of such bridge piers for engineering application under complicated loading conditions.

Prediction of scour depth around bridge piers in tandem arrangement using M5 and ANN regression models

Purpose: Due to an increase in a number of bridges being constructed, scour depth around bridge piers is gradually being recognized as one of the possible reasons for bridge failure. According to [1] about 53% of bridge failures in the US were caused due to floods and corresponding scour in the rivers. Lots of work has been carried out around the single pier but in the case of group piers, the work is very less. Hence, it becomes necessary to calculate the actual scour depth around the bridge piers considering the close location of bridges as well. Design/methodology/approach: Recognizing the need for research in this direction, an experimental study was planned and conducted in the Hydraulics Laboratory of Civil Engineering Department of National Institute of Technology Kurukshetra, India. Experiments were conducted in a standard recirculating tilting bed water flume 15 m long, 0.4 m wide, and 0.60 m deep. The orientation of more than one pier, namely Tandem pattern was employed for the work. Two pier models, 62 mm and 42 mm diameter were used for the experimental study. The mobile bed used in the experiments had an average mean size, d50 = 0.23 mm, 0.30 mm and 0.50 mm. Findings: The outcomes of the ANN function and M5 model analysis have been used to compare with experimental results. From the earlier studies, it was concluded that, when the clear spacing between the pier models was greater than 0D the scour depth around the piers increase with a rapid rate. However, in the case of modelling techniques, M5 models show higher predictive accuracy than ANN models. Research limitations/implications: It is a significant area of research. However, the present study has been a time and facility- constrained study. Therefore, there is a large scope to conduct further studies on the subject, Different pattern i.e. Side by Side; Staggered and Group of piers can be adopted for further investigations. Originality/value: Sufficient work has been done by number of researchers around the single bridge pier. But due to rapid urbanization a number of bridges constructed in close proximity to each other which affects the scour depth of each other. Modelling techniques used in hydraulic engineering are not always effective in practice. The present study discusses the effect of spacing on scouring around piers in a tandem arrangement using experimental as well as modelling techniques. To predict the scour depth of the Tandem arrangement 89 laboratory data sets have been used.