Identification of prestress force from measured structural responses

Lu, Zhong-Rong; Law, S.S.

doi:10.1016/j.ymssp.2005.09.001

Cited by 58 publications

(34 citation statements)

References 11 publications

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“…In particular, in the case of slightly eccentric tendon arrangement, the authors found that the natural frequency decreased for the dominance of axial force. Lu and Law (2006) tested a 4.0 m long RC beam with an ungrouted seven-wire straight strand, located at the centroid of the beam cross-section. Two conditions were tested: with and without a prestressing force of 66.7 kN.…”

Section: Experimental Testsmentioning

confidence: 99%

On the Evaluation of Prestress Loss in PRC Beams by Means of Dynamic Techniques

Breccolotti

2018

Int J Concr Struct Mater

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In the last few decades, prestressing techniques have been used to build very important structures and infrastructures. Since the serviceability and the safety of prestressed reinforced concrete (PRC) elements rely on the effective state of prestressing, development of tools and procedures capable of estimating the effective prestress loss would be very useful. Amongst other techniques, dynamic identification has proved to be an economical, quick and reliable method to evaluate structural integrity. However, the influence of prestressing in the dynamic behavior of PRC elements is not completely clear. In fact, while many references in the literature state that the prestressing force does not affect the frequencies of vibration, almost every experimental test carried out on PRC beams shows an increase in the eigenfrequencies for increasing value of the prestressing force. This paper aims to contribute to the debate, investigating the dynamic behaviour of PRC beams taking into account properties, such as nonlinearity, softening, confinement and micro-cracking of concrete subjected to compression and tension stress states, and the variation of the flexural stiffness of the PRC beam along its length according to bending stress distribution. Non-linear discrete modelling, in combination with system identification and optimization was used to define the dynamic properties of PRC beams, taking into account the effect of prestressing level. The proposed model was applied to four PRC beams with known mechanical and dynamic properties in literature. The influence of the prestressing force on the trend of frequencies of vibration was closely captured for each beam, with errors less than 3% of the estimated frequencies. The results of this investigation thus indicate that dynamic identification techniques can potentially be used to identify the prestressing force level, and consequently the prestress loss, provided the complete concrete mechanics is taken into account.

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Section: Experimental Testsmentioning

confidence: 99%

On the Evaluation of Prestress Loss in PRC Beams by Means of Dynamic Techniques

Breccolotti

2018

Int J Concr Struct Mater

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“…Therefore, the compression-softening effect is insufficient to explain the dynamic behavior of internally prestressed concrete beams. Law and Lu (2005) and Lu and Law (2006) considered the finite element model of internally prestressed concrete beams with time domain responses such as acceleration and strain data. They estimated the tensile force using system identification approach using sinusoidal and impact loads.…”

Section: Relationship Between Natural Frequencymentioning

confidence: 99%

“…Many researchers have been attempted to apply the vibration method using acceleration data to evaluate tensile force of internal tendons (Clough and Penzien, 1993;Saiidi et al, 1994;Law and Lu, 2005;Lu and Law, 2006;Kim et al, 2004;Hamed and Frostig, 2006). Their researches were focused on finding the relationship between the natural frequency of a structure, which can be extracted from the acceleration data and tensile force of internal tendons.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation of dynamic behavior of prestressed girders with internal tendons

Noh

Seong

Lee³

et al. 2015

Int J Steel Struct

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In this study, the dynamic behavior of internally prestressed concrete beam is extensively investigated using the scaled experimental specimens to identify the influence of prestressing force on the natural frequency because there are inconsistent analytical theories in the relationship between natural frequency and prestressing force of internally prestressed concrete beam. Three experimental specimens, i.e., the straight line of tendon with and without eccentricity and parabolic tendon profile are considered to investigate the dynamic behavior of internally prestressed concrete beam. Based on the experimental results, it is observed that the natural frequency is increased as tensile force of tendon is increased in the specimen with eccentricity, however, no meaningful relationship between natural frequency and tensile force could be found in the specimen without eccentricity. These results are related not only to the tensile force itself but also to the camber of the beam introduced by the tensile force. Therefore, it is difficult to establish the distinct relationship between natural frequency and tensile force. Instead, this relationship may be explained as dual effects of tendon on the natural frequency of beam, i.e., stiffening and softening effects. Therefore it is important to consider not only tensile force but also many other parameters such as tendon profile, camber of beam, boundary conditions, ratio of stiffness of concrete and tendon, and etc. for estimating the natural frequency or tensile force of the internally prestressed concrete beam.

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“…To achieve this purpose, the beams should be monitored and non-destructive control methods should be used. Inverse techniques using dynamic responses have been developed in [2] to identify the prestress force in a beam. A one-dimensional (1D) beam modelisation was considered.…”

Section: Introductionmentioning

confidence: 99%

Identification of Reinforced Concrete Beam Parameters Using Inverse Modeling Technique and Measured Dynamic Responses for Structural Health Monitoring

Waeytens¹,

Corvec²,

Lévêque³

et al. 2014

Proceedings of the 4th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COM

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Abstract. Reinforced and prestressed concrete beams are widely employed in civil engineering structures, e.g. in simply supported spans using prestressed concrete beams (VIPP). To reduce the financial cost due to maintenance, structure damages have to be detected early. To achieve this purpose, one needs robust monitoring techniques. The paper deals with the determination of mechanical parameters, useful for Structure Health Monitoring, in a 2D beam using inverse modeling technique. The optimal control theory is employed. As an example, we aim to identify a reduction of the steel bar cross-section and a decrease of the concrete Young modulus in damaged area. In our strategy, the beam is instrumented with strain sensors, and a known dynamic load is applied. In the inverse technique, two space discretizations are considered: a fine dicretization (h) to solve the structural dynamic problem and a coarse discretization (H) for the beam parameter identification. To get the beam parameters, we minimize a classical data misfit functional using a gradient-like algorithm. A low-cost computation of the functional gradient is performed using the adjoint problem solution. The inverse problem is solved in a general way using engineer numerical tools: Python scripts and the free finite element software Code Aster. First results show that a local reduction of the steel bar cross-sections and a local decrease of concrete Young modulus can be detected using this inverse technique.

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Identification of prestress force from measured structural responses

Cited by 58 publications

References 11 publications

On the Evaluation of Prestress Loss in PRC Beams by Means of Dynamic Techniques

On the Evaluation of Prestress Loss in PRC Beams by Means of Dynamic Techniques

Experimental investigation of dynamic behavior of prestressed girders with internal tendons

Identification of Reinforced Concrete Beam Parameters Using Inverse Modeling Technique and Measured Dynamic Responses for Structural Health Monitoring

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