Interface Shear Strength at Joints of Ultra-High Performance Concrete Structures

Young-Jin Kim,Se-Jin Jeon,Won-Jong Chin

doi:10.1186/s40069-018-0298-8

Abstract

When ultra-high performance concrete (UHPC) is fabricated as precast members such as in a UHPC segmental bridge, the joint design between the precast members can significantly affect the overall integrity and safety of the structure. Therefore, the structural behavior of the UHPC joint was experimentally investigated in this study with test variables including joint type, number and height of shear keys, type of filler, curing temperature, and lateral compressive stress. The UHPC considered in this study is the K-UHPC developed in Korea with a specified compressive strength as high as 180 MPa and high flowability. The joint shear strengths affected by the test variables were investigated in detail. The test results were also compared with two representative predictive equations for interface shear strength to determine an appropriate equation for the joint design of UHPC. These equations did not match well with the test data because they were originally proposed for normal strength concrete. However, the JSCE equation could be improved by modifying a coefficient to show good agreement with the test especially in the case of the dry joint with epoxy application.

Highlights

Ultra-high performance concrete (UHPC) has superior mechanical properties in terms of compressive and tensile strengths, ductility, toughness, flowability, durability, etc., when compared to ordinary concrete
Two types of joints have been applied to precast UHPC structures to ordinary concrete structures: a wet joint, where the joint is cast in-place with a selected material (Ishii et al 2008; Matsubara et al 2008; Park et al 2013) and a dry joint, where the surfaces of two precast segments formed by match-casting are in direct contact
5 Conclusions The interface shear behavior at the joints of UHPC segments was experimentally investigated by push-off tests in this study with the test variables including joint type, number and height of shear keys, type of filler, curing temperature, and lateral compressive stress

Summary

Introduction

Ultra-high performance concrete (UHPC) has superior mechanical properties in terms of compressive and tensile strengths, ductility, toughness, flowability, durability, etc., when compared to ordinary concrete. Two types of joints have been applied to precast UHPC structures to ordinary concrete structures: a wet joint, where the joint is cast in-place with a selected material (Ishii et al 2008; Matsubara et al 2008; Park et al 2013) and a dry joint, where the surfaces of two precast segments formed by match-casting are in direct contact. Shin (2016) investigated the failure mode of UHPC shear key made in the form of a dry joint without epoxy, where the contribution of steel fibers was noted. Structural behavior of a UHPC joint was experimentally investigated in this study with the test variables including joint type, number and height of shear keys, type of filler, curing temperature, and lateral compressive stress. The test results were compared with several predictive equations for interface shear strength to determine an appropriate equation for the joint design of UHPC members

Test of UHPC Joints

Analysis of Test Results

Comparison of Experiment with Design Provisions

Findings

Conclusions