On the Effectiveness of Vibration-Based Monitoring for Integrity Management of Prestressed Structures

In this paper, the effectiveness of vibration-based tests for the detection of damages for prestressed concrete beams is investigated. Despite large research efforts, discrepant and sometimes contradicting conclusions have been drawn regarding the efficacy and reliability of vibration-based monitoring for prestressed structures. Herein, a contribution to this discussion is provided by tackling the problem from a different perspective. Specifically, the question that this paper intends to answer is: “Do vibration-based tests support decision-makers in integrity management operations for prestressed elements?” The discussion is carried out by comparing the performance of prestressed and ordinary reinforced concrete beams with similar capacities. Both analytical and numerical case studies are considered. Results show that, for prestressed beams, in contrast to reinforced concrete beams, modal parameters can provide information regarding damage only when the structure is close to its ultimate conditions. This makes this information hardly useful for integrity management purposes and the effectiveness of vibration-based tests questionable for this type of structural element.

Steel Reinforcement Corrosion - Its Impact on Features of Steel PSC Strand

Steel reinforcement made of refined maraging steel in the form of wires and strands has been for a long time used commonly for reinforcement of prestressed concrete structures. Defects on some of them and unfortunately even accidents of some cases of bridge objects, mainly recently published by media, related to corrosion of prestressed reinforcement awoke interest of both professional and wide non-professional public related to its durability. This issue also opens up a question of durability and liability of prestressed structures. In majority of existing prestressed structures the anticorrosion protection of reinforcement was traditionally secured mainly by alkalinity of the environment, i.e. concreting and/or grouting of prestressed elements in ducts. The abstract presents information related mainly to mechanical characteristics of corrosion-affected prestressed elements.

Prestressing Steel Ropes - Corrosion Impact on its Properties

Steel reinforcement made of refined maraging steel in the form of wires and tendons has been for a long time used commonly for reinforcement of prestressed concrete structures. Defects on some of them and unfortunately even accidents of some cases of bridge objects, mainly recently published by media, related to corrosion of prestressed reinforcement awoke interest of both professional and wide non-professional public related to its durability. This issue also opens up a question of durability and liability of prestressed structures. In majority of existing prestressed structures the anticorrosion protection of reinforcement was traditionally secured mainly by alkalinity of the environment, i.e. concreting and/or grouting of prestressed elements in ducts. The abstract presents information related mainly to mechanical characteristics of corrosion-affected prestressed elements.

Calculation of prestressed structures for shock loading

Introduction. With the use of prestressing, coatings are made for special-purpose buildings, requiring calculations for extreme impacts. Such impacts include an airplane strike. Modeling of prestressed structures and calculation of shock loads is difficult to implement in classical calculation programs. A universal tool for solving such problems is the PC SOFiSTIK. This software complex allows you to interact with the most modern software solutions. Materials and methods. For the description of the method, special-purpose coating was selected and the strike calculation of the Learjet 23 aircraft was performed. For modeling prestressing, the SOFIPLUS interface is used. To describe the impact, the internal programming language CADINP is used. Results. The nature of the change in the coating deformations in the first seconds of the aircraft crash is presented graphically. Also, iso-ares of internal bending moments of the coating were derived for the selection of reinforcement and the diagram of the moments of the beams from the action of prestressing, taking into account tension losses. Conclusions. SOFiSTIK PC allows you to solve complex engineering problems with a high degree of automation. Thanks to the open source code, it becomes possible to calculate atypical extreme effects. The obtained graphs and diagrams confirm the passage of checks on the limiting states of the coating, and can also be used to design and calculate similar special-purpose structures.

Design and Experimental Verification of Asphalt-Based Material for Grouting of Prestressed Structure

The quality of the grouting is an important factor affecting the durability of prestressed structures, especially in corrosive environment with stray current. Uncompacted grouting will lead to rapid corrosion and failure of steel strand. In this paper, an asphalt-based material as grouting material was designed to solve this problem due to the characteristics of asphalt material as impermeability, anticorrosion, and insulation. The viscosity and shear strength were considered as the main performance parameters of the grouting material for prestressed grouting. The composition and proportion of the asphalt-based material were determined through the tests, including natural asphalt (rock asphalt) being 12.5% and admixture (slaked lime and cement) being 40%. For this grouting material, the shear strength was 697.21 kPa at normal temperature, and the suitable grouting temperature was 115°C. Then, the grouting test of the prestressed concrete beam was carried out to verify the groutability of this material. The grouting slurry can be filled with prestressed duct, and the temperature stress of the concrete near the duct was lower than 1.4 MPa, which met the safety requirement of the concrete. This study provides a new option for guaranteeing the quality of grouting and improving the durability of prestressed structures in corrosive environment.

Numerical Modeling of Time-Dependent Deformations of Concrete at 3D Analysis of Structures

Concrete is a material with highly nonlinear behavior. In parallel, there are numerous secondary effects in concrete, such as aging, shrinkage, and creep, which further complicate the realistic simulation of reinforced concrete and prestressed concrete structures. In modern times, due to bolder construction, increasing spans and high rising construction, the need for realistic simulation of the behavior of concrete structures under conditions of various types of loads is becoming more pronounced. On the other hand, models with a small number of real-life parameters that can describe the actual behavior of concrete as accurately as possible are necessary. One such model, the previously developed model Precon 3D, which is based on a small number of parameters and can very well describe the behavior of concrete, reinforced concrete and prestressed structures for short-term static loads was taken as the basis for this work. Through this work, the numerical model Precon 3D has been upgraded with a model for following the behavior of concrete during time, i.e. the model has been upgraded with a model of creep and shrinkage of concrete, which is necessary for following the behavior of prestressed structures. The developed software has been tested against several experimental examples from the literature, with a very good match between numerical and experimental results.

Prediction of Restraint Moments in Precast, Prestressed Structures Made Continuous

This paper studies restraint moments developing in simple-span precast, prestressed beams made continuous. Methods of evaluating restraint moments produced by creep and differential shrinkage are presented. Shrinkage and creep properties of composite structures, beam and deck parts were tested and compared to values defined according to Eurocode models. Finally, the restraint moments were calculated with both material models for the two-span parking deck structure. The study confirmed the findings of previous studies: that the methods that are used overestimate the negative restraint moment produced by differential shrinkage.