The review outlines modern trends in theoretical developments, novel designs and modern applications of sandwich structures. The most recent work published at the time of writing of this review is considered, older sources are listed only on as-needed basis. The review begins with the discussion on the analytical models and methods of analysis of sandwich structures as well as representative problems utilizing or comparing these models. Novel designs of sandwich structures is further elucidated concentrating on miscellaneous cores, introduction of nanotubes and smart materials in the elements of a sandwich structure as well as using functionally graded designs. Examples of problems experienced by developers and designers of sandwich structures, including typical damage, response under miscellaneous loads, environmental effects and fire are considered. Sample applications of sandwich structures included in the review concentrate on aerospace, civil and marine engineering, electronics and biomedical areas. Finally, the authors suggest a list of areas where they envision a pressing need in further research.

Review of current trends in research and applications of sandwich structures

Disposal of waste tire rubber has become a major environmental issue in all parts of the world. Every year millions of tires are discarded, thrown away or buried all over the world, representing a very serious threat to the ecology. It was estimated that almost 1000 million tires end their service life every year and out of that, more than 50% are discarded to landfills or garbage without any treatment. By the year 2030, there would be 5000 million tires to be discarded on a regular basis. Tire burning, which was the easiest and cheapest method of disposal, causes serious fire hazards. Temperature in that area rises and the poisonous smoke with uncontrolled emissions of potentially harmful compounds is very dangerous to humans, animals and plants. The residue powder left after burning pollutes the soil. One of the possible solutions for the use of waste tire rubber is to incorporate into cement concrete. This paper presents an overview of some of the research published regarding the fresh and hardened properties of rubberized concrete. Studies show that there is a promising future for the use of waste tire rubber as a partial substitute for aggregate in cement concrete. It was noticed from literatures that workable concrete mixtures can be made with scrap tire rubber and it is possible to make light weight rubber aggregate concrete for some special purposes. Rubberized concrete shows high resistance to freeze-thaw, acid attack and chloride ion penetration. Use of silica fume in rubberized concrete enables to achieve high strength and high resistance to sulfate, acid and chloride environments.

A comprehensive review on the applications of waste tire rubber in cement concrete

Seismic Design and Retrofit of Bridges

Workability and mechanical properties of alkali-activated fly ash-slag concrete cured at ambient temperature

Waste tyres and their accumulation is a global environmental concern; they are not biodegradable, and, globally, an estimated 1.5 billion are generated annually. Waste tyres in landfill and stockpiles are renowned for leaching toxic chemicals into the surrounding environment, acting as breeding grounds for mosquitoes, and fuelling inextinguishable fires. The properties of waste tyre rubber and engineering applications have been previously reported in a range of publications with respect to the environmental, economic, and technical factors. This study compiles and reviews this research with a focus on geotechnical engineering applications, such as earthworks and infrastructure construction. The applications of waste rubber in construction materials includes cementitious concrete, asphalt concrete, and granular materials for earth structures. Crumb rubber, when used as a sand replacement in flowable concrete fill, improved ductility and strength-to-weight ratio. A 40 MPa concrete mix with 0.6% rubber crumb content exhibited optimal strength and air entrainment capabilities, displaying minimal damage after 56 freeze/thaw cycles. Rubber, as a partial replacement for aggregate in road base and sub-base layers, adversely affected the California Bearing Ratio (CBR) of the graded aggregate base course. Rubber-soil mixtures as the interface of foundation and structure yielded a 60–70 % reduction in vertical and horizontal ground accelerations when subjected to earthquake simulation modelling. There is concern regarding the toxicity of waste rubber incorporated products due to leachates of heavy metals and other chemicals common in tyres. Further comprehensive studies in this area are needed. Leachate studies should be conducted under different pH and liquid to solid ratios.

Recycling waste rubber tyres in construction materials and associated environmental considerations: A review

Analytical model for the in-plane shear behavior of URM walls retrofitted with FRP

Force–displacement behavior of unbonded post-tensioned concrete walls

Shaking-Table Testing of High Energy–Dissipating Rubberized Concrete Columns

In this chapter, the behavior of PT-MWs is investigated using a database of tested walls. The accuracy of ignoring elongation of PT bars which is considered in the current masonry standard joint committee (MSJC in Building code requirements for masonry structures, ACI 530/ASCE 5, TMS 402, American Concrete Institute, Detroit, 2013) code in evaluating the strength of PT-MWs is studied using the available test results. Using the experimental results, the structural response parameters including ductility, response modification factor and displacement amplification factor are determined for different types of walls including fully grouted, partially grouted, ungrouted walls, walls with confinement plates, walls with supplemental mild steel and walls with an opening.

Strength and Seismic Performance Factors of Posttensioned Masonry Walls

A novel form of thin-walled composite beams has been developed by bonding cold-formed steel (CFS) and engineered cementitious composites (ECC). Apart from the superior material strength and ductility of CFS and ECC, the proposed CFS/ECC composite system also benefits from the lightweight concept of thin-walled sections and improved buckling performance due to the ECC restraints on CFS. An experimental study, utilising cold-formed steel sections with a yield strength of 450 MPa and engineered cementitious composites with an ultimate tensile strength of 7 MPa, was conducted to investigate the improvement of the innovated structural system over the traditional CFS structures. Two series of composite CFS/ECC beams, namely, short- and long-span Series, were prepared and tested to monitor the shear and flexural behaviours of the novel composite system. Three locations of thin-layered ECC; outside, inside, and in–out of the CFS section were proposed to determine the perfect composite action between ECC and CFS. The load capacity of the composite beams (ECC—in composite beams) increased to eight times those of the bare CFS members in the short-span Series and up to four times in the long-span Series. The failure modes of the novel composite beams were more ductile compared to the bare CFS. Numerical modelling was conducted and validated using the results obtained from the experimental study. This FE model was employed in a small-scale parametric study to investigate the influence of beam spans on the structural behaviour of the composite CFS/ECC beams.

Mohamed A. ElGawady

Papers

Analytical model for the in-plane shear behavior of URM walls retrofitted with FRP

Force–displacement behavior of unbonded post-tensioned concrete walls

Shaking-Table Testing of High Energy–Dissipating Rubberized Concrete Columns

Strength and Seismic Performance Factors of Posttensioned Masonry Walls

Structural performance of novel thin-walled composite cold-formed steel/PE-ECC beams