Development of Improved Models for Estimation of Bursting Stresses in Elements under High-Concentrated Load

Brian Adjetey Boye,Joao Fonte,Samson Ngambi,Samuel Jonah Abbey

doi:10.1590/1679-78255031

Abstract

© 2019, Brazilian Association of Computational Mechanics. All rights reserved. In precast concrete segmental tunnels, radial and circumferential joints are often the most highly stressed parts and it is therefore important to use appropriate equations to accurately analysed these joints during design and provide adequate structural capacity to avoid failure. Different design codes have put forward equations for the estimation of bursting forces due to concentrated load on precast end blocks. The equations were specifically developed for pre-stressed concrete anchors and not specifically for precast concrete segmental tunnels. The design equations often account for the effects of load eccentricity in estimating bursting force but not the peak stress. This paper assesses the accuracy of published equations for bursting force and peak stress by conducting a high-resolution two-dimensional (2D) finite element (FE) based parametric studies. It was found that the effects of load eccentricity are significant for highly concentrated loads (load width ratios less than 0.3) and that they increase the peak bursting stresses significantly. Regression analysis is used to develop equations for estimating the peak bursting stress and bursting force due to load eccentricity for the design of precast concrete tunnel segments. These equations are more accurate as compared to pre-existing equations and important for practising engineers and designers.

Highlights

When a concentrated load acts on one of the joint faces of the segment, tensile bursting forces develop beneath the applied concentrated load
This is to enable comparison of the study in this paper to the theoretical solution. He and Liu (2011); Zhou et al (2015) used polynomial equations defining the load transfer paths of force (isostatic lines of compression (ILC)) to derive equations for the bursting force and centroid of the force. Their equations for bursting force included the effects of eccentricity, the peak stress was not included in their study (Table 1)
The equation commonly used for bursting force (Equation 1) has been improved by accounting for the non-linearity at low load width ratios (a/d) and including the effects of eccentricity

Summary

INTRODUCTION

When a concentrated load acts on one of the joint faces of the segment, tensile bursting forces develop beneath the applied concentrated load. He and Liu (2011); Zhou et al (2015) used polynomial equations defining the load transfer paths of force (isostatic lines of compression (ILC)) to derive equations for the bursting force and centroid of the force Their equations for bursting force included the effects of eccentricity, the peak stress was not included in their study (Table 1). The study concluded that the provision of transverse steel in the area of maximum tensile stress delays the onset of cracking and that treating the tunnel-lining segment as an end-block and designing it to the CP110 design code led to very conservative results. The effect of the contact stress distribution at the joint of a precast tunnel segment on bursting is highlighted and a procedure for the design of steel fibre reinforced concrete (SFRC) tunnel segments involving the use of non-linear numerical analysis is proposed. The ACI318 (2014) clarifies that the equation for the bursting force is only applicable to small eccentricities and confirms that limitation of the equation

Finite Element Analysis

Results and Discussion

Proposed Bursting Force and Peak Stress Equations

Conclusions