Combined shear and flexure performance of prestressing concrete T‐shaped beams: Experiment and deterministic modeling

Abstract

The development of a nonlinear numerical computational model for the detailed description of destructive tests generally requires a multiple-stage, strategic model updating procedure. In this contribution, a model updating procedure is applied to the simulation of prestressed reinforced concrete (RC) beams. The combined ultimate shear and flexure capacity of the beams is affected by many complex phenomena, such as the multi-axial state of stress, the anisotropy induced by diagonal concrete cracking, the interaction between concrete and reinforcement (bond), and the brittleness of the failure mode. In this research, a series of material, small-scale component fracture tests were carried out by two collaborating laboratories. These tests provided advanced statistical identification of the fracture-mechanical parameters of the optimized concrete mixtures for the prestressed laboratory-tested beams mentioned above (with a span of 5.00 m) and associated field-tested, longspan concrete TT roof elements (with a span of 30.00 m). Ten scaled laboratorytested beams with heights of 0.30, 0.45, and 0.60 m were used in a procedure for the comprehensive updating of the nonlinear numerical model with respect to shear resistance performance. The objectives of this research are, in addition to the analysis, the effective development of an updating process for nonlinear numerical modeling which is based on the information from different monitoring systems. Hence, this contribution focuses on the presentation of a comprehensive updating procedure for the shear capacity of nonlinear numerical models of prestressed beam elements using information about fracture-mechanical material parameters gained from (a) different monitoring systems and (b) code-based methods. K E Y W O R D S experimental testing, monitoring systems, nonlinear numerical modeling, prestressed beam elements, shear capacity, updating procedure 1 | INTRODUCTIONThe ultimate capacity of RC beams subjected to combined shear and flexure is affected by many complex phenomena, such as the existing multi-axial state of stress, the anisotropy induced by diagonal concrete cracking, the interaction between concrete and reinforcement (bond), and the brittleness of the failure mode. A large number of shear tests have been performed during the last decades, as summarized in Reference 1 in order to obtain valuable information about the shear transfer mechanisms involved. Currently, both in the United States and in Europe, shear design provisions/ recommendations are undergoing revision. Open questions concern, among other things, the influence of the degree of reinforcement and the prestressing level. Many different model formulations have been proposed. They are either Discussion on this paper must be submitted within two months of the print publication. The discussion will then be published in print, along with the authors' closure, if any, approximately nine months after the print publication.

A comparison of sensitivity analyses for selected prestressed concrete structures

“…The presented T30 150/V2 girder, which is a scaled down version of a full‐scale TT‐shaped LDE7 roof girder, was subjected to a destructive shear test under laboratory conditions; see the geometry and test layout in Figure . The obtained results helped with the development of basic deterministic and stochastic models of both scaled down and full‐scale girders in order to perform the reliability‐based optimization of precast structural members; see Slowik et al, Strauss et al for details. Sensitivity analysis plays a significant role within the development process by helping to focus analysis only on important parameters and reduce the enormous computational burden connected with the utilization of the accurate nonlinear finite element models.…”

“…The obtained information was used to set up their stochastic models and response surfaces in an optimum manner for particular limit states and for the subsequent determination of selected uncertain design parameters followed by load‐bearing capacity and reliability assessments of the bridge . The dominant input parameters were also put to similar use in performance of the reliability‐based optimization of precast T‐shaped structural members …”

Probabilistic and Semi-Probabilistic Analysis of Slender Columns Frequently Used in Structural Engineering

“…In a further step, the reliability and the sensitivity analyses were also performed for the N-M gradients with respect to the associated I-Ds by using the non-linear finite element (NLFEM) elaborations [3,32]. These probabilistic NLFEM studies, as allowed in EN 1992-1-1 [8], also primarily served to evaluate the proposed safety factors for NLFEM considerations [33].…”

“…The probabilistic analysis was carried out as follows: (a) the preparation of the numerical non-linear models for the stochastic procedure including the definition of the random variables (scattering quantities) used in the non-linear numerical analysis for material laws, geometries and loading procedure, see Tables 3 and 4, (b) the formulation of the correlations between the random variables (see Table 5), (c) the implementation of the statistical structural responses of the probabilistic non-linear numerical analyses into the reliability-based verification method in the form of a limit state equation, see Equation (1), (d) the definition of the random variables X i for the limit state equation, (e) the generation of the n-simulation sets, or sample sets using LHS technique for non-linear finite element calculations (for LHS see Section 2.3, for NLFEM see Section 4.3) based on the probabilistic parameters of the random variables displayed in Tables 4 and 5, (f) the n-fold repetition of the NLFEM computation and the structuring of the statistical system responses in response vectors of dimension n suitable for the reliability assessment and (g) the determination of the reliability and failure probabilities with regard to predefined limit values and the study of the sensitivities of the input base variables with regard to the examined limit state equations. The correlations according to [32] were set up for the numerical simulations as shown in Table 5.…”

Assessment of posttensioned concrete beams from the 1940s: Large‐scale load testing, numerical analysis and Bayesian assessment of prestressing losses

“…A better approach for estimating general prestress losses is the one applied in Sousa et al 10 , where prestress losses are updated based on measured displacements. Literature on destructive assessment of prestressed structures can be found in Bagge et al 11 ; Huber et al 1 ; Strauss et al 12 . Nevertheless, these works do not account for relevant uncertainties and lack a probabilistic approach.…”