• Søren Hansen
4. term, Structural and Civil Engineering, Master (Master Programme)
An experimental and numerical study of the partially concrete filled steel tube is conducted in order to investigate their mechanical behaviour.
Initially a hypothesis of the mechanical behaviour is developed. It is believed that the main pa-rameters to dominate the mechanical behaviour of the PCFT besides the length of the grout core and the slenderness of the element (L/D)is the diameter- thickness ratio (D/t), the material strength and the bonding between steel and grout.
This thesis focus on the influence of the grout strength and the bonding by testing 6 steel tubes partially filled with high strength grout (fc = 115 MPa) and 6 filled with low strength grout (fc = 7.7 MPa) in 3-point bending. Half the test specimens are greased inside in order to remove the bonding between grout and steel.
An experimental test is carried out on an empty steel tube as a reference for the setup of a nu-meric model and the results of the experimental testing of the partially concrete filled steel tubes.
The Plastic-damage model in Abaqus is chosen as material model for the grout. The material model is described and a sensitivity study shows that the model is mesh-dependent when the viscoplastic regularization is activated.
Material testing on the grout determines the compressive and tensile strength. The modulus of elasticity and Poisson’s ration is found for the high strength grout.
A simplified numerical model for the steel tube is fitted to the reference tube and the numeric model of the partially concrete filled steel tube is based on this simplified model.
The test results shows that the grout extend the linear elastic range of the load-deflection relation for the partially concrete filled steel tubes with 57-112 % depending on the grout strength and the contact relations.
The numeric results correspond to the experimental tests initially but underestimate the peak load due to the simplified model of the steel tube.
The failure mechanism is depending of the grout strength and the bonding between grout and steel. The cracks in the grout in the greased tubes are wider and the number of cracks reduced. In the low strength grout the crack width is so small that the invisible by the naked eye. The crushing is significant in the low strength grout contrary to the test specimens with high strength grout.
The failure in the steel differs due to the crushing in the grout. Outward buckling develops in the steel tubes partially filled with high strength grout and the inward deformation of the steel where the load is applied occurs.

LanguageEnglish
Publication date20 Jun 2011
Number of pages84
ID: 53074431