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<p> The behavior of concrete block walls subjected to vertical compressive loads with out-of-plane eccentricities was investigated both experimentally and analytically. Particular attention was devoted to the effect of wall slenderness on capacity.</p> <p> In the experimental study, 14 full scale walls and numerous small specimens were tested to provide complete and reliable data concerning the behavior of concrete block walls and its components. Plain walls and partially grouted reinforced walls were tested in symmetric single curvature under compressive loads with out-of-plane eccentricities. Reinforced walls were tested in pure bending, as well.</p> <p> Prisms were tested to analyze the behavior of concrete masonry in compression with no slenderness or eccentricity effects. Bond tests were carried out to determine the behavior at interfaces of grout and steel reinforcing bars as well as between mortar and concrete blocks. Material tests were conducted to determine the mechanical properties of the blocks, mortar, grout and steel reinforcement used.</p> <p> A two-dimensional finite element model for the vertical cross section of block masonry walls was developed. It is capable of modeling local failure modes such as cracking, crushing and debonding. Material properties of the concrete blocks, mortar, grout, and steel bars were treated individually. The large deformation analysis allowed for consideration of the slenderness effect. The model was verified through comparison with experimental results. Fairly good agreement was obtained.</p> <p> The material properties of specimens tested during the experimental investigation were the basis of a parametric study. Results of this study were used to investigate the effect of the wall slenderness and the eccentricity of applied loads on the capacity of concrete block walls. They were used to evaluate the current provisions in the Canadian Masonry Code, CAN3-S304-M84. An attempt was made to develop original design equations based on the reduction coefficient approach. The proposed equations for plain and reinforced blockwork were shown to provide more consistent predictions of capacity than current design methods.</p> / Thesis / Master of Engineering (MEngr)

This paper presents a nonlinear 3-D finite element model for eccentrically loaded concrete encased steel composite columns. The columns were pin-ended subjected to an eccentric load acting along the major axis, with eccentricity varied from 0.125 to 0.375 of the overall depth (D) of the column sections. The model accounted for the inelastic behaviour of steel, concrete, longitudinal and transverse reinforcement bars as well as the effect of concrete confinement of the concrete encased steel composite columns. The interface between the steel section and concrete, the longitudinal and transverse reinforcement bars, and the reinforcement bars and concrete were also considered allowing the bond behaviour to be modelled and the different components to retain its profile during the deformation of the column. The initial overall geometric imperfection was carefully incorporated in the model. The finite element model has been validated against existing test results. The concrete strengths varied from normal to high strength (30¿110 MPa). The steel section yield stresses also varied from normal to high strength (275¿690 MPa). Furthermore, the variables that influence the eccentrically loaded composite column behaviour and strength comprising different eccentricities, different column dimensions, different structural steel sizes, different concrete strengths, and different structural steel yield stresses were investigated in a parametric study. Generally, it is shown that the effect on the composite column strength owing to the increase in structural steel yield stress is significant for eccentrically loaded columns with small eccentricity of 0.125D. On the other hand, for columns with higher eccentricity 0.375D, the effect on the composite column strength due to the increase in structural steel yield stress is significant for columns with concrete strengths lower than 70 MPa. The strength of composite columns obtained from the finite element analysis were compared with the design strengths calculated using the Eurocode 4 for composite columns. Generally, it is shown that the EC4 accurately predicted the eccentrically loaded composite columns, while overestimated the moment.

A nonlinear finite element analysis was performed for an axial loaded reinforced concrete column subjected to biaxial bending taking into account second-order effects. According to Eurocode there are two ways to take second-order effects into consideration: nonlinear FE analysis and hand calculation based on the simplified methods explained in Eurocode 2. Since simulating this kind of structures in ABAQUS is difficult, several simulations were made to find the correct model with satisfying accuracy. The nonlinear analysis focused on material modelling of concrete and its nonlinear behaviour. The simulation took into consideration the inelastic behaviour of concrete along with the confinement effect from transverse reinforcement. The finite element model was verified by comparing the obtained results from FEA to the results from a benchmark experiment. The mean values needed for simulating the FE model was derived from the mean compressive strength of concrete. After verification, another FE model using design parameters was analysed and the results were compared to the results from calculations based on simplified methods according to Eurocode 2 to see how much they agreed with each other. In a parametric study, the effect of eccentricity, compressive and tensile strength of concrete, fracture energy, modulus of elasticity, column cross-section dimension and length, steel yield stress and stirrup spacing were studied. A comparison between outcomes from the simplified methods and ABAQUS, calculated with design parameters showed that the bearing capacity from FE analysis was 21-34 % higher than the one obtained with the simplified methods. It is recommended that in further studies, analyse different slender reinforced concrete column with different L/h with FE-simulation to investigate if FEA always gives a more accurate result. For this case, and probably for columns with complex geometries, a finite element analysis is a better choice. / En icke-linjär finitelementanalys för en armerad betongpelare utsatt för tvåaxlig böjning genomfördes med hänsyn till andra ordningens effekter. Enligt Eurokoder finns det två sätt att iaktta andra ordningens effekter: icke-linjär analys och handberäkning baserad på de förenklade metoderna förklarad i Eurokod 2. Eftersom det är svårt att simulera den här typen av konstruktioner i ABAQUS, så har flera simuleringar utgjorts för att finna ett modell med acceptabelt noggrannhet. Den icke-linjära analysen fokuserade på korrekt materialmodell av betong och dess icke-linjära beteende. Modellen tog hänsyn till betongens oelastiska beteenden och inkluderade fleraxiella effekten. Finitelementmodellen verifierades genom att jämföra de erhållna resultaten från FEA till resultaten från ett försök. Värden som behövdes för att simulera FE-modellen härleddes från betongens medeltryckhållfasthet. Efter att referensmodellen var verifierad, ytterligare en FE-modell, som inkluderade designparametrar, analyserades och resultaten jämfördes med resultaten från beräkningar baserade på förenklade metoderna enligt Eurokod 2 för att se hur mycket de stämde överens med varandra. I en parameterstudie har effekten av excentricitet, tryck- och draghållfasthet av betong, brottenergi, elasticitetsmodul, pelarens tvärsnittsdimension och längd, stålsträckgränsen och centrumavstånd på byglar studerat. En jämförelse mellan resultaten från de förenklade metoderna och ABAQUS, beräknade med designparametrar visade att bärighetförmågan från FE-analys var 21-34% högre än den som erhålls med de förenklade metoderna. Det rekommenderas att i fortsatta studier, analysera flera slanka armerade betongpelare med olika L/h med FE-simulering för att undersöka om FEA alltid ger ett nogrannare resultat. För denna studie, och förmodligen för pelare med komplexa geometrier, är en FE-analys ett bättre val.