Precast Prestressed Girders Research Articles

Analytical, numerical, and experimental determination of dynamic characteristics of prestressed concrete girders

To determine the dynamic characteristics of bridges with prestressed girders, their natural frequencies and mode shapes used to construct the superstructure must be known. However, there is no agreement among scientists on how prestress force affects the dynamic characteristics of a precast prestressed girder. The purpose of this paper is to obtain the dynamic characteristics of prestressed concrete girders through analytically, numerically, and operational modal testing. For this purpose, one of a typical precast I-girder with 1.2 m height and 27.45 m effective span length is selected as a numerical application. The three-dimensional (3D) finite element model (FEM) of the girder is modeled by SAP2000. Experimental measurements of the girder were conducted at the construction site by the operational modal testing method. For experimental measurements, ten uniaxial seismic accelerometers were mounted at the top flange of the PSC girder in the x- and z-direction. The vibrations that occur from the movement of trucks and cranes at the construction site and the impact of the hammer were measured by these accelerometers as acceleration. The measured signal was collected at the data bank and then sent to the computer equipped with Operational Modal Analysis software which used Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification techniques. The dynamic behaviors of girder were derived from analysis performed by this software. At the end of the study, the dynamic characteristic was obtained by the analytical prediction, numerical and experimental were compared with each other. It is seen that natural frequencies and mode shapes obtained from theoretical prediction, numerical and operational modal testing are not too far apart.

Performance assessment and design of ultra-high performance concrete (UHPC) structures incorporating life-cycle cost and environmental impacts

Ultra-high performance concrete (UHPC) as a novel concrete material is associated with very high strength and low permeability to aggressive environment. There have been many studies focusing on the development of UHPC materials. More studies are needed to implement the knowledge obtained from material level into the structural design and construction level. This paper emphasizes on the structural modeling and performance assessment of bridge girders made of UHPC considering the major improvements in terms of structural performance, durability, environmental impacts, and cost-effectiveness in a long-time interval. Additionally, the effect of the concrete strength increase on the life-cycle environmental impact and cost is assessed on a structural scale. An illustrative example is established to demonstrate the use of UHPC within precast-prestressed girder bridge. It is found that the use of UHPC can result in a significant reduction of concrete volume and CO2 emissions compared with conventional bridge with the same span length. Additionally, the life-cycle cost and equivalent annual cost associated with these two bridges are compared. This study aims to aid the development and adaptation of novel materials within civil engineering to make optimal use of the favorable material properties.

Diagnostic Assessment of One of the First Generation of Prestressed Concrete Bridges in Slovakia

The first generation of precast prestressed girder bridges have been used in Czechoslovakia in the 1950s. Nowadays, many of this bridges are in insufficient condition and require extensive rehabilitation. Concrete bridge No. 59-090 on the important international route I/59 connecting Slovakia to Poland, was in failure condition before collapse. After visual inspection it was necessary to definitely eliminate traffic on the bridge. The diagnostic survey has confirmed the necessity to replace the superstructure of the bridge and repair the original abutments and bridge pier. The bridge was closed and the traffic was redirected on temporary bridge during the reconstruction time. This paper focuses on the diagnostic survey of this type of prestressed concrete bridge.

Parametric Effects on Evaluation of an Impact-Damaged Prestressed Concrete Bridge Girder Repaired by Externally Bonded Carbon-Fiber-Reinforced Polymer Sheets

AbstractThis paper investigates the evaluation procedure of an AASHTO Type 3 precast-prestressed girder that was extensively damaged by truck impact and then repaired using externally bonded fiber-reinforced polymer (FRP) composites. Results of this study can be applied to bridges having similar vehicle impact incidents. Parameters whose effects were investigated on the evaluation procedure include (1) the effect of horizontal resistance of elastomeric bearing supports, (2) the presence of barrier wall and sidewalk, and (3) live load distribution factors obtained from finite-element analysis (FEA) compared with the simplified method prescribed by other codes. FEA showed that support horizontal resistance has negligible effects on live load distribution factors for shear, Fv, while it has considerable effect on live load distribution factors for moment, Fm. The live load distribution factors Fm and Fv calculated from the simplified method of analysis prescribed by other codes were observed to all be greate...

The Load Testing and Numerical Verifying of the Precast Prestressed Girder

Precasting can solve complicated structural details, ambitious demands to quality of surface arrangements and manage hard terms filling at present. The prestressed precast girders are produced to 30.0 m span and are distributed for the realization of big shopping centers. The design and realization of the prestressed precast tie-beam for a skeleton system is presented in this paper. The experimental and numerical analyses were performed to verify the safety and reliable acting of the girder for the next service.

Numerical analysis of time-dependent behavior of pre-cast pre-stressed concrete girder bridges

This paper deals with the analysis of uncertainties associated with the behavior of bridges constructed with pre-cast pre-stressed girders and a continuous deck. To analyze the long-term behavior of bridges, an analytical model which can simulate the effects of creep, the shrinkage of concrete, and the cracking of concrete slabs in the negative moment regions is introduced. Based on the equilibrium of forces and the compatibility of strains with time, the prediction of stresses and strains in the constitutive materials at any time is achieved. To consider the different material properties across the sectional depth, the layer approach in which a section is divided into imaginary concrete and steel layers is adopted. An element stiffness matrix is constructed according to the assumed displacement field formulation, and the creep and shrinkage effects of concrete are considered in accordance with the first-order recursive algorithm based on the expansion of the compliance function. Correlation studies between analytical and experimental results are conducted with the objective of establishing the validity of the proposed model. Also, many parameters related to the continuity of spans are analyzed to minimize deck cracking at the interior supports.

Corrosion prevention and remediation strategies for reinforced concrete coastal bridges

Oregon's coastal highway includes over 120 bridges, most of which are reinforced concrete bridges. Twelve are historic structures. Over 40,000 m 2 of bridge surface has been repaired and is protected from further corrosion damage using thermal-sprayed zinc anodes in impressed current and galvanic cathodic protection (CP) systems. In addition, thermal-sprayed titanium, thermal-sprayed Al–12Zn–0.2In, and zinc-hydrogel anodes are being evaluated in demonstration projects on coastal bridges. Thermal-sprayed zinc anodes are estimated to have a service life exceeding 25 yr but exhibit increasing anode polarization with electrochemical age. Humectants such as lithium nitrate and lithium bromide can reduce anode polarization and extend anode service life. Catalyzed thermal-sprayed titanium anodes develop no significant anode polarization and exhibit stable long-term performance. Zinc-hydrogel galvanic anodes produce a stable protection current with no evidence of aging effects. One of the more powerful and economical tools available for assessing potential corrosion problems in a structure and for characterizing the corrosivity of bridge microclimates is chloride profiling. Current Oregon DOT specifications call for the use of stainless steel reinforcing bar in deck, beams, and precast prestressed girders, and of microsilica concrete in all future coastal bridge construction. Stainless steel bar adds a 10% premium to total project cost compared to black iron bar but is expected to reduce cumulative costs by 50% over the 120+ yr bridge life.