Raymond Ian Gilbert

One of the main areas where it is generally accepted that fibers play a significant contribution in construction practice is in the control of cracking. The primary objective of the fibers is to traverse cracks after they nucleate. The fibers provide some post‐cracking resistance to the otherwise brittle concrete. Much of the research contained in the literature on the cracking behavior of fiber reinforced concrete (FRC) members has focused on instantaneous load scenarios, without much consideration for the long‐term behavior (i.e., for members which are subjected to a sustained service moment). This is mirrored in design standards where limited guidance is provided to engineers to predict and assess the long‐term serviceability performance of FRC members. This paper presents a simplified model, which may be suitable for design, that can reliably predict the cracking behavior, over time, of FRC members subjected to a sustained in‐service flexural load. Predictions of the proposed model are compared to both instantaneous and long‐term data available in the literature. Satisfactory correlation is observed.

This chapter presents a state-of-the-art review of work published to date on the time-dependent response of composite steel-concrete slabs. The key components of this form of construction are introduced in the first part of the chapter, followed by a review of the time-dependent behaviour of the concrete and how it affects the in-service response of composite slabs. Throughout the chapter, particular attention is given to recent experimental and modelling work related to concrete time effects, and how these affect the in-service response of composite slabs, including the development of non-uniform shrinkage gradients that have been recently shown to occur in composite floors due to the inability of the concrete to dry from its underside because of the presence of the profiled steel sheeting.

This chapter provides an introduction to the constitutive models commonly specified in design guidelines to describe the time-dependent behaviour of concrete and that can be used for the time-dependent analysis of composite structures. These formulations range from the simplest algebraic methods, such as the Effective Modulus Method that is widely recommended in design guidelines, to more sophisticated approaches that can account for creep and shrinkage effects in advanced modelling. The last part of the chapter provides a brief overview of multi-physics modelling that could be useful in predicting the concrete time-dependent response for composite construction.

This chapter presents a state-of-the-art review of the time-dependent behaviour of composite columns. The first part of the chapter outlines the available typologies and advantages of composite columns. This is followed by an overview of the time-dependent response of concrete (specific to composite columns) and an introduction to concrete confinement. The main part of the chapter is devoted to the state-of-the-art review on how concrete time effects influence the long-term and ultimate behaviour of concrete-filled steel tube (CFST) columns, and on the combined effects produced by sustained loading and chloride corrosion on CFST columns. The review then deals with the long-term behaviour of concrete-filled double skin tube (CFDST) and encased composite columns. The final parts of the chapter provide a review of the time-dependent differential axial shortening (DAS) in vertical components of multi-storey buildings and on the long-term response of arch bridges.

This chapter introduces three case studies that describe how aspects related to the serviceability limit state design associated with the time-dependent behaviour of concrete can be considered in a design situation. The first case study considers the Oxec II Bridge in Guatemala. It provides an overview of the stress verification of the steel section of the composite bridge and accounts for concrete time effects to capture the stress redistribution that occurs between the concrete and the steel components. The second case study deals with the Yalquincha Viaduct in Chile and provides an overview of the type of long-term analyses that can be carried out when considering the influence of different cross-sectional arrangements on the time-dependent response of the bridge. The last case study focusses on the Serra Cazzola Viaduct in Italy and highlights the opportunities available to designers in exploiting optimised casting sequences to reduce the time-dependent stresses induced in the concrete and, therefore, mitigate the likelihood of concrete cracking.

This chapter provides an introduction to the constitutive models commonly specified in design guidelines to describe the time-dependent behaviour of concrete and that can be used for the time-dependent analysis of composite structures. These formulations range from the simplest algebraic methods, such as the Effective Modulus Method that is widely recommended in design guidelines, to more sophisticated approaches that can account for creep and shrinkage effects in advanced modelling. The last part of the chapter provides a brief overview of multi-physics modelling that could be useful in predicting the concrete time-dependent response for composite construction.

This chapter presents a number of case studies that deal with the service design of composite steel-concrete buildings associated with the time-dependent behaviour of the concrete. The particular focus of this chapter is to outline key design aspects that need to be accounted for in design and that are influenced by concrete time effects. The first case study provides an overview of the design considerations related to the time-dependent column shortening in typical multi-storey buildings by considering the layout of the Intesa Sanpaolo Headquarters in Turin as reference. The second case study focuses on a composite floor of a commercial building constructed in Australia and it provides an overview of the conceptual design used to select the steel beam framing arrangement to support the composite floor system while accounting for concrete cracking and time effects. The third case study deals with the Quay Quarter Tower that has been designed for the repurposing of an existing 50-year old building in Australia while accounting for the time-dependent interaction between the existing and the new concrete components of the building.

This chapter provides an overview of the work carried out to date on the long-term behaviour of composite steel-concrete beams. In the first part of the chapter, a description of the components forming a composite member is presented. This is followed by an outline of the main kinematic concepts, such as full and partial shear interaction, that influence the structural response of this form of construction due to the flexibility of the shear connection provided between the concrete and steel components. The review of the work performed on the time-dependent behaviour of concrete and its influence on the long-term structural response of composite beams for building and bridge applications is then presented. The modelling and experimental work considered in the review highlights the importance of considering concrete time effects, when predicting the in-service response of composite beams.