Digital image correlation strain measurement of ultra‐high‐performance concrete‐prisms under static and cyclic bending‐tensile stress

Stefan Harenberg,Sha Yang,Diego S Schicchi,Antonio Caggiano,Matthias Pahn,Eddie Koenders,Viktória Malárics‐Pfaff,Frank Dehn

doi:10.1002/suco.201900033

Abstract

AbstractThis paper provides experimental results on investigations for the validation of photogrammetric strain measurements of ultra‐high‐performance concrete (UHPC)‐prisms subjected to static and cyclic bending‐tensile stress. For this purpose, 4 static and 5 cyclic test series were performed. Damage progresses during loading are monitored by means of a digital image correlation (DIC) system and a clip gauge. The control of the DIC by trigger lists and the measurement noise as a function of the measurement rate are examined. All static tests were performed force controlled with the same testing speed and the same measuring rate of DIC and clip gauge. All cyclic tests were performed with the same upper and lower stress levels but with different loading rates.During the static tests, the DIC can be used to make accurate strain measurements before UHPC failure. In the cyclic tests, the measurement noise of the DIC decreases with an increasing measuring rate. The tests performed confirm the control of the DIC by trigger lists for cyclic tests on UHPC‐prisms and show that the measurement noise is negligible in static and cyclic tests.

Highlights

Ultra-high-performance concrete (UHPC) is a composite material characterized by a greater strength and higher durability than a conventional concrete
Aim of the experimental program is the validation of the strain measurement of UHPC-prisms, subjected to cyclic bending-tensile stress, by means of digital image correlation (DIC)
This procedure was chosen because the measurement noise of the DIC depends on the measuring rate, which has to be selected according to the loading rate.[34]

Summary

| INTRODUCTION

Ultra-high-performance concrete (UHPC) is a composite material characterized by a greater strength and higher durability than a conventional concrete. Outstanding test results on UHPC, which are worth of mentioning were published by Brosge[28] and Kessler-Kramer[29] while for tensile-tests by Fitik.[24] within the scope of the DFG-Priority-Program 2020 “Cyclic Damage Processes in High Performance Concretes in the Experimental Virtual Lab”, the Department of Concrete Structures and Structural Engineering of the TU Kaiserslautern, the Institute of Construction and Building Materials of the TU Darmstadt and the Institute of Concrete Structures and Building Materials of the Karlsruhe Institute of Technology (KIT) are running a research project titled “Micromechanical behavior of high performance concrete under cyclic loading at various moisture and thermal conditions”. According to the dimensions of the specimens (Figure 1), the material tests were performed on prisms according to EN 196-1.30 They provided a compressive strength of 107 N/mm[2] and a bending tensile strength of 11.3 N/mm[2]

| EXPERIMENTAL SETUP

| RESULTS AND DISCUSSION

| CONCLUSIONS

33. DIN EN 12390-5