An Rapid Assessment Method for Bearing Capacity of RC Girder Bridges Based on Residual Strain

In order to realize the in-situ evaluation of reinforced concrete bridges subjected to fatigue for a long time or after earthquake, an evaluation method for cumulative damage of concrete structures based on unloading elastic modulus was proposed. First, according to the concrete stress-strain curve and the statistical relationship between residual strain and cumulative strain, the calculation method of static equivalent strain and residual strain concrete based on unloading elastic modulus and the method for estimating the strength of concrete after damage were proposed. The detailed steps of field test and analysis and the practical damage indicators of residual strain were given. Then, the evaluation method of existing stress and strain of Reinforced Concrete Bridge under dead load and the concept of “equivalent dead load bending moment” were put forward. On this basis, the paper analyzed the root cause of the decrease of bearing capacity of Reinforced Concrete Bridge after fatigue damage, and pointed out that the equivalent strain or residual strain of reinforced concrete increases under the fatigue effect, which led to the decreasing of actual live moment and deformation performance while the ultimate load-carrying capacity remained constant or very little decrease. The evaluation method of structure residual capacity was given, and through comparative analysis of eight T reinforced concrete beams that had been in service for 35 years with the static failure tests, the effectiveness of the method was verified.

Analysis of Bridge-Bearing Capacity Detection and Evaluation Technology

A bridge project is taken as an example to analyze the application of bearing capacity detection and evaluation.This article provides a basic overview of the project,the application of bearing capacity detection technology,and the bearing capacity assessment analysis.It is hoped that this analysis can provide a scientific reference for the load-bearing capacity detection and evaluation work in bridge engineering projects,thereby achieving a scientific assessment of the overall load-bearing capacity of the bridge engineering structure.

Analysis of the Application of Static Load Test in Bridge Bearing Capacity Testing

This article uses real engineering projects as examples to analyze how static load test technology is applied in testing the bridge-bearing capacity.The analysis covers aspects such as testing section layout,test load and efficiency coefficient,loading plan,evaluation optimization,test result modification,and result evaluation.The aim is to support the accurate detection and evaluation of bridge-bearing capacity.

Ultra-High Performance Concrete: An Advanced Solution for Accelerated Bridge Pier Cap Rehabilitation and Bearing Replacement

The objective of this paper is to propose and illustrate feasibility, approach, validation as per prevailing codes and design standards, specification to rehabilitate bridge pier cap by using Ultra-High Performance Concrete (UHPC). The evaluation of existing pier caps and bearings indicates that the complete removal of existing bearing is undesirable due to 1) massive size of bearing 2) difficulty in cutting through the thick components of existing bearing 3) deeply anchored lower shoe of existing bearings 4) huge cost and time required to erect temporary support system for superstructure to facilitate the construction of new piers. To overcome these difficulties, UHPC could be cast around the lower shoe up to the existing bearing pin. This UHPC cast could be used to support jacks and temporary bearings. The new low height permanent bearing could then be installed after removing the upper shoe of the existing bearing. In the present research, first properties of UHPC are summarized followed by evaluation of case studies to check feasibility of the solution to rehabilitate pier cap by using UHPC. The complex load paths in pier cap are idealized by using validated strut and tie model as per prevailing AASHTO LRFD Bridge Design Specification.

Structure Bearing Capacity Testing and Evaluation of Existing Bridges

The bearing capacity testing and evaluation of the existing bridge engineering structure is not only the key to clarify its structural quality and safety performance,but it also can lay a solid foundation for subsequent repairs and maintenance work.To ensure the bearing capacity,durability and reliability of existing bridges,this paper analyzes the importance and methods of testing and evaluation of structural bearing capacity of a bridge.This analysis aims to provide scientific reference for the quality assessment and subsequent repair and maintenance of existing bridge engineering structures.

METHOD FOR BRIDGE BEARING CAPACITY ASSESSMENT BASED ON ANALYTIC HIERARCHY PROCESS

By analyzing the existing methods for the bridge bearing capacity assessment, an analytic hierarchy pro cess estimation model with a variable weight and fuzzy description is proposed based on the nondestructive infor mation. Considering the actual strength, the bearing capacity is first calculated from its design state, and then modified based on the detection information. The modification includes the section reduction and the structure deterioration. The section reduction involves the concrete section and the steel cross-section reduction. The structure deterioration is decided by six factors, i.e. , the concrete surface damage, the actual concrete strength, the steel corrosion electric potential, the chloride ion content, the carbonization depth, and the protective layer depth. The initial weight of each factor is calculated by the expert judgment matrix using an analytic hierarchy process. The consistency approximation and the error transfer theory are used. Then, the variable weight is in- troduced to expand the influences of factors in the worse state. Finally, an actual bridge is taken as an example to verify the proposed method. Results show that the estimated capacity agrees well with that of the load test, thus the method is objective and credible

Study of the seismic performance of expansion double spherical seismic isolation bearings for continuous girder bridges

The development of an expansion double spherical seismic isolation (DSSI) bearing by modifying the fixed DSSI bearing is described in this paper. The expansion DSSI bearing is characterized by its good energy dissipation and horizontal displacement capacity and has been successfully integrated into the seismic design of several important engineering projects in China. It is envisioned to be used as a substitute for ordinary expansion bearings in continuous girder bridges to distribute the longitudinal earthquake action among all the piers. Its development, configuration and working mechanism are introduced first. The test method and the seismic performance of an expansion DSSI bearing are then briefly described. A theoretical analysis followed by a numerical analysis for an actual four-span continuous girder bridge are provided as an example, and it is concluded that the expansion DSSI bearing can be integrated into the seismic design of continuous girder bridges.

Seismic performance of cable-sliding friction bearing system for isolated bridges

During past strong earthquakes, highway bridges have sustained severe damage or even collapse due to excessive displacements and/or very large lateral forces. For commonly used isolation bearings with a pure friction sliding surface, seismic forces may be reduced but displacements are often unconstrained. In this paper, an alternative seismic bearing system, called the cable-sliding friction bearing system, is developed by integrating seismic isolation devices with displacement restrainers consisting of cables attached to the upper and lower plates of the bearing. Restoring forces are provided to limit the displacements of the sliding component. Design parameters including the length and stiffness of the cables, friction coefficient, strength of the shear bolt in a fixed-type bearing, and movements under earthquake excitations are discussed. Laboratory testing of a prototype bearing subjected to vertical loads and quasi-static cyclic lateral loads, and corresponding numerical finite element simulation analysis, were carried out. It is shown that the numerical simulation shows good agreement with the experimental force-displacement hysteretic response, indicating the viability of the new bearing system. In addition, practical application of this bearing system to a multi-span bridge in China and its design advantages are discussed.

Effects of vertical excitation on the seismic performance of a seismically isolated bridge with sliding friction bearings

A finite element model is constructed for a sliding friction bearing in a seismically isolated bridge under vertical excitation with contact/friction elements. The effects of vertical excitation on the seismic performance of a seismically isolated bridge with sliding friction bearings and different bearing friction coefficients and different stiffness levels （pier diameter） are discussed using example calculations, and the effects of excitation direction for vertical excitation on the analysis results are explored. The analysis results shows that vertical excitation has a relatively large impact on seismic performance for a seismically isolated bridge with sliding friction bearings, which should be considered when designing a seismically isolated bridge with sliding friction bearings where vertical excitation dominates.

Numerical analysis on bearing capacity of middle pylon caisson foundation of Taizhou Bridge

Because of the computation difficulty of the beating capacity of large underwater caisson foundation on thick overburden layer ground, the geotechnieal software FLAC3D was utilized in the 3D numerical analysis on the bearing capacity of middle pylon foundation. From the computational results, it is concluded that the caisson foundation has a good bearing capacity on thick overburden layer ground and the beating capacity can be improved assuming that the soil near the area of basal comer is reinforced.

A Study on the Seismic Isolation Systems of Bridges with Lead Rubber Bearings

This study consists of the development and presentation of example of seismic isolation system analysis and design for a continuous, 3-span, cast-in-place concrete box girder bridge. It is expected that example is developed for all Lead-Rubber Bearing (LRB) seismic isolation system on piers and abutments which placed in between super-structure and sub-structure. Design forces, displacements, and drifts are given distinctive consideration in accordance with Caltrans Seismic Design Criteria (2004). Most of all, total displacement on design for all LRBs case is reduced comparing with combined lead-rubber and elastomeric bearing system . Therefore, this represents substantial reduction in cost because of reduction of expansion joint. This presents a summary of analysis and design of seismic isolation system by energy mitigation with LRB on bridges.

Analysis on Bearing Capacity of Tunnel-Type Anchorage of a Long-Span Suspension Bridge

Due to complicated rock structure and environment, a prototype test for a tunnel-type anchorage is infeasible. Based on the rock mass parameters from tests, a three-dimensional （3D） elastoplastic analysis was performed to simulate the influence of the construction procedure of Siduhe bridge with tunnel-type anchorage （TTA） in Hubei Province, China. The surrounding rock and concrete anchorage body were simulated by 8 nodes 3D brick elements. The geostatic state of the complex geometric structure was established with initial data. The in-situ concrete casting of the anchorage body and excavation of the rock mass were simulated by tetrahedral shell elements. The results show that the surrounding rock is in an elastic state under the designed cable force. The numerical overloading analysis indicates that the capacity of the surrounding anchorage is 7 times that of the designed cable force. The failure pattern shows that two anchorage bodies would be pulled out in the end. The maximum shear stress appears 10 m before the back anchorage face. The maximum range influenced by the TTA under ultimate loads is about 16 m.

Application of LRB isolation technology in continuous girder bridges

This paper summarizes the superiority of lead-rubber beating （LRB） continuous girder bridges. The research method for isolation performance is discussed when pile-soil interaction is considered. By the finite element method and self-compiling program, a systematic study of the reliability of LRB continuous girder bridges is given by the use of different indicators, including the riding comfort of the LRB system, the pounding and dynamic stability when the LRB system is subjected to seismic excitations, and the reliability of the LRB system when subjected to other common horizontal loads. The results show that the LRB system has obvious advantages over the traditional continuous girder structure. The LRB isolation effect remains good even when pile-soil interaction is considered; the vertical rigidity of the LRB guarantees desirable riding comfort. The LRB demonstrates good reliability when subjected to the effects of braking, wind loads and temperature. However, it is also pointed out that the pounding of the LRB system subjected to earthquakes must be avoided, and the dynamic stability may be reduced when the LRB system has higher piers and generates a larger displacement in a strong earthquake. Useful advice and guidance are proposed for engineering application.

Study on the seismic performance of a double spherical seismic isolation bearing

In this paper, the configuration and working mechanism of the recently developed double spherical seismic isolation （DSSI） bearing are introduced in detail. Then, vertical displacement of the DSSI bearing due to sliding on a spherical surface is analyzed. The results from seismic performance testing of the bearing are given, and a numerical analysis of a four span continuous girder bridge is performed. The numerical analysis compares the influence of three different bearing arrangement schemes on the structural seismic response, and the results show that the DSSI bearing is effective in increasing the vertical load bearing capacity, reducing the vertical displacement, and controlling the energy dissipation capacity within a certain range.

Design of a d_(33)-mode piezocomposite electricity generating element and its application to bridge monitoring

The piezoelectric effect is used in sensing applications such as in force and displacement sensors.However,the brittleness and low performance of piezoceramic lead zirconate titanate(PZT) often impede its applicability in civil structures which are subjected to large loads.The concept of a piezocomposite electricity generating element(PCGE) has been proposed for improving the electricity generation performance and overcoming the brittleness of piezoceramic wafers.The post-curing residual stress in the PZT layer constitutes a main reason for the PCGE's enhanced performance,and the outer epoxy-based composites protect the brittle PZT layer.A d33-mode PCGE designed for bridge monitoring application was inserted in a bridge bearing to provide a permanent and simple weigh-in-motion system.The designed PCGEs were tested through a series of tests including fatigue and dynamic tests to verify their applicability for monitoring purposes in a bridge structure.A simple beam example was presented to show the applicability of the proposed bridge bearing equipped with the PCGE for adequately measuring the traffic loads.

Experimental and Finite Element Analysis for Multi-lead Rubber Bearings:A Comparative Study

The mechanical properties of multi-lead rubber bearings （MLRBs） were investigated by experiment and finite element analysis. First, the vertical stiffness, horizontal stiffness and yielded shear force were tested for four MLRB specimens and two specimens of the single-lead rubber bearings （ SLRBs）. Then, the MLRBs were modeled by the explicit finite element analysis software ANSYS/ LS-DYNA, in order to evaluate the horizontal force-displacement hysteretic curves under static vertical and dynamical horizontal loadings. The disagreement between the tested and theoretical values was less than 11.4%, and MLRBs and SLRBs were similar in vertical stiffness, pre-yield stiffness and yield stiffness.

Load-Measuring Pot Bearing with Built-In Load Cell —Part I: Design and Performance

This paper presents the underlying principle and the results of various performance evaluations for a load-measuring pot bearing with built-in load cell. The pot bearing composed of a pot made of steel in which an elastomer disk is inserted is a bearing supporting larger loads than the elastomeric bearing and accommodating rotational movement. Owing to a Poisson’s ratio close to 0.5, elastomer withstands hydrostatic pressure when confined in a rigid body. Accounting for this principle, the vertical load applied on the pot bearing can be obtained by converting the pressure acting on the elastomer. Therefore, a load-measuring pot bearing is developed in this study by embedding a load cell exhibiting remarkable durability in the base plate of the bearing. The details for the insertion of the load cell in the base plate of the pot were improved through finite element analysis to secure sufficient measurement accuracy. The evaluation of the static performance of the pot bearing applying these improved details verified that the bearing exhibited sufficient accuracy for the intended measurement purpose. The dynamic performance evaluation results indicated that accurate measurement of the dynamic load was also achieved without time lag.

Identification of Bridge Movement Mechanisms

Bridge behavior is highly dependent upon the movement mechanisms present throughout the structure. These mechanisms (e.g. bearing, joints, etc.) have a substantial impact on the long-term durability and potential safety of the structure. A major distinguisher between the varieties of movement systems is their operating timescale. In some cases, they function rapidly, within fractions of a second, and in other cases gradually over days, months or even years. However, in nearly all cases, the lifecycle of the movement system is shorter than that of the bridge assuring the need for future intervention. Breakdown of a movement system can produce unintended forces/deformations that progressively degrade the structure. Identification and tracking of movement mechanisms proactively address long-term durability by helping to avoid these unintended consequences. A general framework for characterization of these mechanisms was developed. This framework was applied to an operating bridge that includes several critical mechanisms operating over different timescales. As a result of this and other studies, recommendations are provided for identification of bridge movement systems.

Assessment and Retrofit of the Bridge over Kouris River, Cyprus

The main objective of the present study is the assessment and retrofit of an existing road bridge that is located in Cyprus over the river Kouris. In particular the study concerns in a road bridge with seven spans of 10.5 m + 5 * 12.6 m + 10.5 m, a cross section width of 7.10 m and a 5 m piers height that was constructed in the early 50’s. The structural system of the bridge comprises of cast in situ reinforced concrete T-beams and slab deck that is simply supported on masonry piers. According to the new urban plan to design the bridge should now accommodate two lanes per direction, a pedestrian walkway and a cycling lane with total cross section width of new deck 15.60 m. The deck of the bridge widened using for aesthetic reasons the same cross section type and the new T-Beams and slab deck connected monolithically to the existing one. The existing part of the deck was strengthened with reinforced concrete jacketing due to inadequacy in shear resistance. Major challenge of the project posed the existing masonry pier layout that was insufficient to carry the new design seismic forces. New piers, founded on piles, were designed adjacent to the existing piers in order to support the new widened part of the bridge, and also to bear all the horizontal loads arising from the masses of the total deck. Sliding bearings (free movement) placed in the part of the bridge over the existing piers and elastomeric bearings with movement only in the longitudinal direction placed in the new piers.

The Detection Evaluation and Reinforcement Research of Kankan River Bridge

This design is about Chongqing Wanzhou district KanKan river crossing test evaluation and reinforcement renovation. The bridge is an open spandrel stone arch bridge. After years of operating, defects arise from different parts. To verify whether the bridge meets the bearing capacity of highway grade I standard, this design firstly evaluates the bridge through the apparent diseases. Then it uses Midas/Civil to calculate the bearing capacity of lateral control section for Zhou Jiaba arch foot, L/4 and arch section. Using Midas/Civil control section load calculation, load test plan is made. In the end, by increasing cross-section method, the bridge reinforcement maintenance plan is made;that is increasing abdominal 26 cm concrete layer in the main arch ring of arch so that the bridge meets grade I highway capacity requirements.