Strength and Deformations of Structural Concrete Subjected to In-Plane Shear and Normal Forces

Abstract

PrefaceThe present doctoral thesis was developed within the framework of the research project "Deformation Capacity of Structural Concrete". This project aims at developing a consistent and experimentally verified theory of the deformation capacity of structural concrete. Previous work included the development of a theoretical model, the so-called Tension Chord Model, which allows a comprehensive description of the load-deformation behaviour of tension members in non-prestressed and prestressed concrete structures.The present work focuses on a new theoretical model, the so-called Cracked Membrane Model. For members subjected to in-plane forces this new model combines the basic concepts of the modified compression field theory and the tension chord model. Crack spacings and tension stiffening effects in cracked membranes are determined from first principles and the link to plasticity theory methods is maintained since equilibrium conditions are formulated in terms of stresses at the cracks rather than average stresses between the cracks.The research project "Deformation Capacity of Structural Concrete" has been funded by the Swiss National Science Foundation and the Association of the Swiss Cement Producers. This support is gratefully acknowledged. Zurich, July 1998Prof. Dr. Peter Marti AbstractThis thesis aims at contributing to a better understanding of the load-carrying and deformational behaviour of structural concrete subjected to in-plane shear and normal forces. Simple, consistent physical models reflecting the influences of the governing parameters are developed on whose basis (i) a realistic assessment of the deformation capacity of structural concrete subjected to in-plane loading is possible, (ii) the limits of applicability of the theory of plasticity to structural concrete can be explored, and (iii) current design provisions can be critically reviewed, supplemented and harmonised.In the first part of this thesis relevant properties of concrete and reinforcement are examined, basic aspects of the theory of plasticity and its application to structural concrete are summarised, previous work on plane stress in structural concrete is reviewed, and fundamental aspects of the behaviour of cracked concrete membranes are investigated.In the second part a new model for cracked, orthogonally reinforced concrete panels subjected to a homogeneous state of plane stress is presented. The cracked membrane model combines the basic concepts of original compression field approaches and a recently developed tension chord model. Crack spacings and tensile stresses between the cracks are determined from first principles and the link to limit analysis methods is maintained since equilibrium conditions are expressed in terms of stresses at the cracks rather than average stresses between the cracks. Both a general numerical method and an approximate analytical solution are derived and the results are compared with previous theoretical and experimental work. Simple expressions for the ultimate load of reinforced concrete pane...

On Development of Suitable Stress Fields for Structural Concrete

“…on the influence of the transverse strains η(ε j ) in the concrete strength, leading to various models 17,[19][20][21] that, in general, provide similar results. For instance, according to Hars,21 this parameter can be evaluated using where f c ′ is the compressive strength of concrete in MPa (6.90 MPa = 1ksi).…”

Time-dependent modelling of RC structures using the cracked membrane model and solidification theory

“…(6) and (7) require modification. For service conditions, however, the steel is rarely at yield and the reader is referred to Kaufmann [14] and Foster and Marti [11] for details of the calculation of mean steel and concrete stresses post yield. As discussed by Foster and Marti [10], the crack spacing given by Vecchio and Collins [19] is a reasonable approximation to the exact solution and is given by…”

“…For FE modelling, the growth of concrete tensile strength with time was taken from Eq. (14) with A fct ¼ 4 MPa and B fct ¼ 12 days. The shrinkage constants were calculated from measurements on shrinkage companion specimens giving A sh = 950 le and B sh = 45 days in Eq.…”

Querkrafttragfähigkeit von Stahlbetonträgern

“…Dieses Modell wird in [10] und [21] ausführlich vorgestellt und in [19] in eine modifizierte Form gebracht. Es beruht auf dem so genannten Zuggurtmodell [20], das die Abschätzung von Rissabständen und Rissbreiten sowie die rechnerische Berücksichtigung der Mitwirkung des Betons zwischen den Rissen gestattet.…”