The development of analytical methods for quantitatively predicting the cracking effects on the lateral deflection and stiffness characteristics of tall reinforced concrete buildings under service loads is the main objective of this study. There are many factors that influence the overall response of reinforced concrete structures, for instance, loading types, boundary conditions, material and section properties, arrangement of reinforcement in the structures, various cracking patterns, tension stiffening effects, aggregate interlock, concrete-steel bond and dowel action. These factors can be categorized into three classes, external causes, internal causes and consequences. The external causes include loading types and boundary conditions, the internal causes involve material and sectio...[ Read more ]

The development of analytical methods for quantitatively predicting the cracking effects on the lateral deflection and stiffness characteristics of tall reinforced concrete buildings under service loads is the main objective of this study. There are many factors that influence the overall response of reinforced concrete structures, for instance, loading types, boundary conditions, material and section properties, arrangement of reinforcement in the structures, various cracking patterns, tension stiffening effects, aggregate interlock, concrete-steel bond and dowel action. These factors can be categorized into three classes, external causes, internal causes and consequences. The external causes include loading types and boundary conditions, the internal causes involve material and section properties, and the consequences include various cracking patterns and tension stiffening. The philosophy in solving for the cracking effects is that it is a result of the interaction of the external causes and the internal causes.

Based on the above philosophy, a general probability based effective stiffness of the member level is proposed to determine the relationship between flexural stiffness reductions and the various moments due to loading acting on the members. The reinforcement effect has been considered as a part of the secondary effects on the member's stiffness characteristics. Extensive discussions and comparisons have been conducted with the proposed model, and the code relationships of different countries and previous experimental data. A series of large-scale beam tests have been conducted to further investigate the behavior and stiffness reduction of reinforced concrete flexural members and to determine the limitation and accuracy of the proposed behavior model. These beams had various reinforcement ratios and were tested under different types of loading.

An experimental series of large-scale shear wall tests was also conducted to investigate the behavior and stiffness characteristics of reinforced concrete shear walls with various aspect ratios and subjected to combinations of various vertical and lateral loads. The proposed model was found to be sufficiently accurate for design purpose in predicting the flexural stiffness reduction of both the low-rise and high-rise shear walls.

The most significant feature of the proposed model is its extensive applicability to the members subjected to various load types, which is inherent in the developed theory. By introducing the probability of cracking occurrence in terms of a specific ratio, - the area of the moment diagram over which the working moment exceeds the cracking moment, S_cr to the total area of moment diagram, S, this model can be readily used as a general constitutive model on the member level in the tall reinforced concrete buildings. A design-oriented cracking analysis system can be established by integrating the proposed stiffness reduction model, iterative algorithms and commercial packages of linear finite element analysis. This work forms a design-oriented integrated analysis system to quantitatively account for the cracking effects on the lateral deflection and stiffness characteristics of tall reinforced concrete buildings with loading in serviceability range. Primary verification has been achieved by comparing the analytical results with the experiment results of frame structures obtained from previous studies.

The technique has been validated by comparing the analytical results and experimental results of a large-scale test of rigid-frame. In addition, a wall-frame structure was also tested and good agreement between the experimental data and analytical results indicated that its application can be expanded to tall reinforced concrete buildings where a wall-frame structure is used as the lateral load resisting system.

A primary application of the proposed method on a 40-storey tall reinforced concrete building is presented. The cracking effects on the lateral deflection and stiffness characteristics were analyzed explicitly and quantitatively for the first time.