Solid Piers Research Articles

A numerical algorithm for damage progression of reinforced concrete bridge piers during air temperature and solar radiation cycles

Reinforced concrete (RC) solid piers are unavoidably affected by air temperature changes and solar radiation during service life. Nevertheless, the deterioration of pier concrete with increased exposure age remains unclear. A novel thermal-mechanical numerical algorithm (finite element model) for characterizing the deterioration characteristics of RC structures under cyclic environmental loads has been suggested. The deterioration of RC pier concrete after 100 years of air temperature and solar radiation cycles is simulated. The numerical results demonstrate that tensile damage of pier concrete during air temperature and solar radiation cycles increases continuously with exposure age. After one year of exposure, the tensile damage value of pier surface concrete increased to 0.201 and further increased to 0.286 and 0.357 as the exposure age grew to 10 and 100 years. Pier concrete tensile damage can be mitigated by using surface short-wave absorption-reducing methods, controlling the thermal properties of concrete, and raising the concrete peak tensile strain. The proposed finite element framework and numerical solutions enable a viable simulation-based method for the analysis of bridge structural long-term deterioration behavior and design of the bridge engineering.

Quasi-static tests and seismic fragility analysis of RC bridge piers with high-strength steel bars and high-strength/ultra-high performance concrete

The use of high-strength steel bars (HSSB), high-strength concrete (HSC) and ultra-high performance concrete (UHPC) in bridge piers can obviously improve bearing capacity and save material consumption. However, the use of high strength materials may detrimentally affect the seismic performance of reinforced concrete (RC) piers. This paper tries to study the seismic performance of RC piers with HSSB and HSC/UHPC by quasi-static tests and seismic fragility analysis. Three RC piers, solid pier with normal strength steel bars (NSB) and normal strength concrete (NSC), solid pier with HSSB and HSC, and hollow pier with HSSB and UHPC, were designed and tested under quasi-static loading. The failure mode, hysteretic performance, stiffness degradation and residual displacement of three specimens were compared and analyzed. A fiber-based beam-column finite element model (FEM) was developed to simulate the nonlinear response of RC piers with HSSB and HSC/UHPC. On this basis, the seismic fragility analysis was performed to study the effects of high-strength materials on the seismic performance of RC piers. Research results show that, compared with NSC piers, HSC piers reinforced with a small amount of HSSB still exhibited slightly larger lateral bearing capacity but lower deformability due to the higher brittleness of HSC. The UHPC hollow pier presented obviously larger deformation capacity, and more slow decline speed of lateral stiffness than NSC and HSC solid piers. Meanwhile, the matching use of UHPC and HSSB in hollow pier can improve the elastic deformation, and then reduce residual displacement of RC piers. The proposed fiber-based finite element model (FEM) can simulate the nonlinear response of RC piers with different high-strength materials with reasonable accuracy. Fragility results demonstrate that, HSC pier presents lower seismic fragility than NSC pier at different damage states except for collapse due to lower ductility of HSC pier. The UHPC hollow pier with HSSB has lower seismic fragility than NSC and HSC solid piers at the same seismic intensity. Overall, the hollow pier with HSSB and UHPC can maintain good seismic performance while greatly saving material consumption.

Mega-earthquake response of benchmark high-speed rail bridge piers based on shaking table tests

The notion of Mega-Earthquake hazard level is first established in this paper. Three 1/5-scale and six 1/8-scale round-ended rectangular-shaped cross-sections (RERSCS) RC solid piers were tested on a shaking table. A series of shaking table experimental and numerical research on RERSCS RC solid piers shows the successful seismic response of the Mega-Earthquake-affected high-speed rail (HSR) bridge. The test revealed that the piers maintained outstanding integrity and stability beneath the earthquake action, with a peak ground acceleration (PGA) of 0.96 g. The results indicate that the test piers can withstand the higher seismic loads. Then, the seismic response of bridge pier specimens was analyzed to Mega-Earthquake loading. The longitudinal reinforcement rate substantially impacts the form of the bridge pier's hysteresis curve and the energy dissipation capacity. The study's findings can provide a reference for transforming seismic design from the current three-level fortification principle to the four-level fortification principle.

Experimental investigation on the flexural-shear performance of railway short piers

To investigate the seismic behavioral characteristics of railway solid piers with small aspect ratio, low axial load ratio and light reinforcement, twenty 1/5-scaled specimens were tested under cyclic loading with constant axial load. The test parameters consisted of longitudinal steel ratio, aspect ratio, width-to-depth ratio, axial load ratio, cross-section type, and lateral steel ratio. The damage evolution, strain profile, and hysteretic curves of railway piers were presented, followed by the discussion on the influence of above parameters in terms of ductility, dissipated energy, damping ratio and nominal shear strength. The applicability of several existing shear strength formulas to such type railway piers was evaluated based on the test data. The results showed that the railway short solid piers with low axial load tended to fail in flexural-shear or even flexural mode instead of shear failure though with light reinforcement, implying the axial compression affected significantly the seismic behaviors of such type members. The longitudinal rebar, transverse rebar, section types exerted great influence on the crack distribution. Appropriate enhancement of stirrup could improve the damping ratio. Compared with the existing formulas, the modified Sezen model can be the used to estimate the shear strength of railway short solid piers precisely.

Shear strength evaluation of RC solid piers of high-speed railway bridges in China

Piers are the main lateral force-resisting members of high-speed railway (HSR) bridges used in China and are characterized by low axial load ratios, low longitudinal reinforcement ratios, low stirrup ratios, and high shear span ratios. It is well known that flexural, flexural-shear, and shear failures of piers may occur during an earthquake. In this study, a new shear strength model was developed to simulate the seismic failure of HSR solid piers accurately. First, low cyclic-loading test data of solid piers obtained in recent years were collected to set up a database for model verification. Second, based on the test database, the applicability of existing shear strength models was evaluated. Finally, a new shear strength model for HSR solid piers with round-ended cross-sections was derived based on the truss model and ultimate equilibrium theory. In comparison with existing models, it was demonstrated that the proposed model could be used to predict the shear strength of HSR piers more accurately.

REVISITING DURABILITY OF BRIDGE SOLID PIERS

The paper presents data on the prevalence and service life of solid piers of railroad bridges of the Russian Railways. The dynamics of solid pier damages, the development of normative documents on assessing their technical conditions and durability, and methods of assessing the residual life of bridge structures are shown herein. Information on the threshold values of failure is also given. The residual life of the intermediate masonry support is analyzed and estimated using two standard techniques. Their similarities and differences are determined and their limitations are compared. Proposals are made to clarify the damage parameters described in the current normative document for assessing the technical condition of railway structures. For statistical data processing in relation to bridge damages and prediction of their development, a model is proposed on the basis of semi- Markovian process. Possible data sources for constructing such a model are indicated. An alternative model for estimating the reliability of bridge structures is shown.

Seismic Performances of Mountainous Continuous Rigid Frame Solid and Hollow Pier Railway Bridges

This paper focuses on the seismic performance of mountainous railway bridges having different pier type i.e. rectangular hollow piers and solid piers. The piers used were of same materials and inertial properties. For this, 3-D FEM models of these bridges were created by ANSYS 15.0. For seismic assessment, Response Spectrum and Dynamic Time-History Analysis methods were adopted. Different types of earthquake waves used were Elcentro, Wenchuan and Nepal earthquakes, all normalized to 0.3 g Peak Ground Acceleration (PGA). The study concluded that even though the hollow pier bridges are susceptible to large displacements, its dealing with internal forces is remarkable compared to solid pier bridges.

Experimental investigations of the seismic performance of bridge piers with rounded rectangular cross-sections

Solid piers with a rounded rectangular cross-section are widely used in railway bridges for high-speed trains in China. Compared to highway bridge piers, these railway bridge piers have a larger cross-section and less steel reinforcement. Existing material models cannot accurately predict the seismic behavior of this kind of railway bridge piers. This is because only a few parameters, such as axial load, longitudinal and transverse reinforcement, are taken into account. To enable a better understanding of the seismic behavior of this type of bridge pier, a simultaneous influence of the various parameters, i.e. ratio of height to thickness, axial load to concrete compressive strength ratio and longitudinal to transverse reinforcements, on the failure characteristics, hysteresis, skeleton curves, and displacement ductility were investigated. In total, nine model piers were tested under cyclic loading. The hysteretic response obtained from the experiments is compared with that obtained from numerical studies using existing material models. The experimental data shows that the hysteresis curves have significantly pinched characteristics that are associated with small longitudinal reinforcement ratios. The displacement ductility reduces with an increase in ratio of axial load to concrete compressive strength and longitudinal reinforcement ratio. The experimental results are largely in agreement with the numerical results obtained using Chang-Mander concrete model.

A Method for Checking Eccentricity of Solid Concrete Piers with Low Longitudinal Reinforcement Ratio under a Minor Earthquake

Solid concrete piers with low longitudinal reinforcement ratio are extensively used in high-speed railway in China. However, how to check such structures is not specified in current technical codes. Checking these structures by eccentricity and stress indexes is discussed hereby. The moment-curvature relationships for piers of various reinforcement ratios are presented by employing the software UCfyber and these moments are compared with moments calculated by allowable stress approach, moments corresponding to the code-specified permissible eccentricity, moments corresponding to the allowable reinforcement stress and stabilizing moments induced by tensile reinforcement and self-weight of the piers, respectively. The results show that the allowable stress approach could be used to check the strength and eccentricity of solid concrete piers with low longitudinal reinforcement ratio in high-speed railway; the restriction on permissible eccentricity may be to a proper extent relaxed for such piers, based on the fact that tensile reinforcement provides an additional stabilizing moment and the reinforcement contributes to the pier’s bearing capacity.

Operational modal analysis of a multi-span skew bridge using real-time wireless sensor networks

A large-scale field deployment of high-density, real-time wireless sensors networks for the acquisition of local acceleration measurements across a medium length, multi-span highway bridge is presented. The advantages, performance characteristics, and limitations of employing this emerging technology in favor of the traditional cable-based acquisition systems are discussed in the context of the in-service instrumentation and ambient vibration testing of a multi-span bridge. Of particular highlight in this study is the deployment of a large number of stationary rather than reference-based accelerometers to uniquely permit simultaneous acquisition of vibration measurements across the structure and thereby ensure consistent temperature, ambient vibration, and traffic loading. The deployment consisted of 30 dual-axis accelerometers installed across the girders of the bridge and interfaced with 30 wireless acquisition and transceiver nodes operating in two star topology networks. Real-time wireless acquisition at a per channel sampling rate of 128 samples per second was maintained across both networks for the specified test durations of 3 min with insignificant data loss. Output-only system identification of the structure from the experimental data is presented to provide estimates of natural frequencies, damping ratios, and operational mode shapes for 19 modes. The analysis of the structure under test provides a unique case study documenting the measured response of a multiple-span skewed bridge supported by elastomeric bearings. The feasibility of embedded wireless instrumentation for structural health monitoring of large civil constructions is concluded while highlighting relevant technological shortcomings and areas of further development required. In particular, previously undocumented obstacles relating to radio transmission of the sensor data using low-power 2.4 GHz wireless instrumentation, such as the effect of solid piers within the line-of-sight and the reflection of the radio waves on the surface of the water, are discussed.

Analysis of RC Hollow Columns Strengthened with GFRP

Reinforced concrete (RC) hollow piers in bridges withstand high moment and shear demands ensured with reduced mass and lower stress on foundations compared with solid piers. Failure of hollow columns is typically affected by premature buckling of reinforcing bars and concrete cover spalling. At present, no guidelines are available for the design of their upgrade, and few research investigations can be found on hollow columns strengthened by using fiber-reinforced polymer (FRP) materials. This paper discusses an experimental program carried out on purely compressed RC hollow columns externally wrapped with glass-fiber-reinforced polymer (GFRP). Three specimens were tested: one specimen was unstrengthened and used as the benchmark; the other two specimens were GFRP-wrapped with different confining reinforcement ratios. Each specimen was designed according to dated codes (i.e., prior to 1970) accounting only for gravity loads. In particular, steel longitudinal bars cross section and steel tie-spacing were designed with the minimum amount of longitudinal reinforcement and minimum tie area at maximum spacing. Tests results highlight that the GFRP-jacket mainly provided ductility increases before low strength increments could be obtained. Refined and simplified numerical models for hollow square RC columns, previously proposed by the authors, herein extend to hollow rectangular members. Comparisons of experimental results and theoretical predictions on the basis of both refined and simplified confinement models were performed and showed good agreement. In the case of the simplified model, a value for the effective ultimate FRP strain was suggested.

50%주철근 겹침이음을 갖는 중실 및 중공 사각단면 교각의 거동특성

50%주철근 겹침이음을 갖는 중실 및 중공 사각단면 교각의 거동특성

Flow resistance due to slotted piers

Resistance to flow due to an obstruction in the form of bridge piers give rise to many problems which are of engineering interests. An experimental study of the effects caused to some of these problems due the introduction of a vertical longitudinal slot to an obstruction in the form of a pier is carried out. Experiments are performed in the subcritical range of Froude number to measure the drag force and the energy loss with various slot width to pier thickness ratios, and the results are compared with those of conventional solid piers. The results obtained show a substantial reduction in the drag coefficient for slotted piers compared to the solid ones under the same flow conditions. Experiments also indicate the existence of an optimum value of slot width to pier thickness ratio. The loss in the total energy of the flow is also found to be smaller for the slotted pier compared to a similar solid pier.