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Concrete is indeed one of the most consumed construction materials all over the world. In spite of that, its behavior towards absolute volume change is still faced with uncertainties in terms of chemical and physical reactions at different stages of its life span, starting from the early time of hydration process, which depends on various factors including water/cement ratio, concrete proportioning and surrounding environmental conditions. This interest in understanding and defining the different types of shrinkage and the factors impacting each one is driven by the importance of these volumetric variations in determining the concrete permeability, which ultimately controls its durability. Many studies have shown that the total prevention of concrete from undergoing shrinkage is impractical. However, different practices have been used to control various types of shrinkage in concrete and limit its magnitude. This paper provides a detailed review of the major and latest findings regarding concrete shrinkage types, influencing parameters, and their impacts on concrete properties. Also, it discusses the efficiency of the available chemical and mineral admixtures in controlling the shrinkage of concrete.

Tensile strength of soil is indeed one of the important parameters to many civil engineering applications. It is related to wide range of cracks specially in places such as slops, embankment dams, retaining walls or landfills. Despite of the fact that tensile strength is usually presumed to be zero or negligible, its effect on the erosion and cracks development in soil is significant. Thus, to study the tensile strength and behavior of soil several techniques and devices were introduced. These testing methods are classified into direct and indirect ways depending on the loading conditions. The direct techniques including c-shaped mold and 8-shaped mold are in general complicated tests and require high accuracy as they are based on applying a uniaxial tension load directly to the specimen. On the other hand, the indirect tensile tests such as the Brazilian, flexure beam, double punch and hollow cylinder tests provide easy ways to assess the tensile strength of soil under controlled conditions. Although there are many studies in this topic the current state of the art lack of a detailed article that reviews these methodologies. Therefore, this paper is intended to summarize and compare available tests for investigating the tensile behavior of soils.

Indeed, base isolation systems have gained significant attention from researchers and designers over the last few decades. Within this context, various technologies were developed to improve the performance of structures under strong earthquake shaking intensities. Recently, a new generation of multi-stage friction pendulum (FP) bearings known as “Quintuple Friction Pendulum” (QFP) was introduced to the literature to attain high energy dissipation capability. The main advantages of this bearing come from its ability to achieve complex multi-stage adaptive behavior with smoothed loading and unloading when subjected to lateral forces owing to its five effective pendula and nine operation regimes. On the other hand, investigations that studied the influence of the bearing properties and the impact of various ground motion characteristics on the performance and behavior of this isolation system are scarce. Thus, this research aims to conduct a parametric assessment that highlights and quantifies the effect of the various isolator properties and earthquake characteristics on the behavior of the base-isolated structure. As a part of the study, finite element models considering the nonlinearity of the isolation system and the superstructure will be developed in OpenSees. Generally, the study results have shown that the behavior of the isolator is significantly influenced by its properties and the type of earthquake being applied.

Base isolation systems have attained significant advancements over the past several decades, with new technologies being developed to enhance the performance of structures when subjected to moderate and severe seismic excitations. The multi-stage friction pendulum is among the most efficient systems owing to its broad range of effective pendula with several regimes that provide excellent energy dissipation abilities. Lately, a new generation of friction pendulum bearings called “Quintuple Friction Pendulum” was introduced to the literature and has since gained the attention of researchers. This isolator’s most significant advantages are the results of its capability to achieve multi-stage adaptive behavior which shows high energy dissipation capability from structures exposed to horizontal forces. Indeed, investigations that outlined the process for nonlinear modeling of structures supported on this type of isolation system are scarce. Thus, this research is intended to illustrate and discuss the approach for developing seismic code compliance finite element models for designing and analyzing reinforced concrete moment frames supported on quintuple friction pendulum bearings for nonlinear response-history analysis in OpenSees and SAP2000. As a part of the study, the nonlinearity of the isolation system and the superstructure will be considered. Moreover, the methods for overcoming essential issues such as damping leakage and isolator’s stiffness correction will be discussed. In general, the results of the discussed numerical examples have shown that both finite element packages are capable of achieving QFP hysteresis behavior as well as computing similar superstructural responses. Furthermore, the illustrated method of overcoming damping leakage provided reliable outcomes compared to the theoretical expectations. As well as the suggested approach for correcting the isolator’s initial stiffness was helpful in terms of accurately capturing the structure’s periods.