On a nonlinear hybrid method for multiscale analysis of a bearing-capacity test of a real-scale segmental tunnel ring.

Jiao‐Long Zhang,Herbert A Mang,Yong Yuan,Xian Liu,Bernhard Pichler

doi:10.1002/nag.2894

Jiao‐Long Zhang, Herbert A Mang + Show 3 more

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https://doi.org/10.1002/nag.2894

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Abstract

SummaryA nonlinear hybrid method is developed for multiscale analysis of a bearing‐capacity test of a real‐scale segmental tunnel ring subjected to point loads. The structural analysis consists of two parts. Part I refers to modeling of bending‐induced tensile cracking of the segments, resulting from the external loading. The segments are subdivided into elements, according to the crack spacing. Each element is either intact or contains one central crack band, flanked by lateral undamaged domains. A multiscale model for tensile softening of concrete is used to describe the progressive deterioration of the crack bands. After iterative determination of their state of damage, the effective bending and extensional stiffnesses of the corresponding elements are quantified by means of Voigt‐Reuss‐Hill estimates. The effective stiffnesses are used for linear‐elastic simulations of the segmental tunnel ring. Part II refers to the relative rotation angles at the joints, which are estimated from monitoring data, using the Bernoulli‐Euler hypothesis. Since the validity of this hypothesis is questionable for neck‐like joints, the relative rotation angles are post‐processed such that they refer to rigid body displacements of the segments. The following conclusions are drawn: The presented approach yields good estimates of crack widths. Relative rotation angles at the joints mainly result in rigid body displacements of the segments, governing the convergences. Because realistic interface models are lacking, hybrid analysis based on displacement‐monitoring data allows for performing ultimate‐load analysis of segmental tunnel rings.

Highlights

The linings of tunnels, excavated by boring machines, consist of segmental rings
Equations 1 to 19 allow for analytical structural analysis of segmental tunnel rings, provided that the material behavior of the segments is linear elastic, the external loading is known, and the relative rotation angles at the joints were either measured or computed by means of interface models
Two questions are posed at the beginning of the discussion. They read as follows: Are the relative rotation angles at the joints related to rigid body displacements, or do they activate internal forces? How important is the consideration of bending-induced tensile cracking of the segments in the context of quantifying the internal forces and the convergences?

Summary

Introduction

The linings of tunnels, excavated by boring machines, consist of segmental rings. The individual segments are made of precast reinforced concrete. Their design, including the geometric layout of the initial segment-to-segment contact area[5] and the use of bolts, connecting neighboring segments, either non-prestressed or prestressed.[6,7] The behavior of the joints is nontrivial, because of (1) nonlinearities resulting from bending-induced partial segment-from-segment separation,[8,9] (2) nonlinearities resulting from the material behavior, including crushing of concrete[5,10] and yielding of the steel bolts, 6,7 and (3) the time-dependent viscoelastic material behavior of concrete.[11] The aim of the present paper is to consider all of these influence factors in the framework of analyzing a bearing-capacity test of a segmental tunnel ring,12without the need to explicitly model the nontrivial joint behavior. The analysis is based on the linear theory of slender circular arches.[13]

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