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Doors are the most critical part in any structure as they may eventually fail first when subjected to extreme loads such as blasts. Blast resistant doors in a structure work as effective barriers against blast pressure thus making the entire structure safe. Accordingly, the need to provide blast resistant doors arises in important structures to endure blast pressure. Herein, the comparative performance of a three-hinged five-latched double leaf composite door subjected to blast loading is investigated using finite element analysis software LsDyna. The composite door consists of front and rear steel plates composed of armor steel and three different infill materials, i.e., polyurethane (PU) foam, aluminum syntactic foam with 200 μm cenosphere (Al200), or plain cement concrete (PC) are explored in this investigation. Comparative studies of these composite doors are performed by varying the thicknesses and types of infill material and blast-scaled distances. The peak deflection, permanent deflection, internal energy, and total energy are compared among the doors considered herein. Weight and cost analysis of the door are also considered to determine the most cost-effective solution. The numerical results show that the polyurethane core door illustrates better performance for 150 mm of core material. However, the plain concrete infill door and cenosphere aluminum alloy core door demonstrate enhanced performance for 100 mm core thickness at 0.15, 0.2, 0.3, and 0.4 m/kg1/3 scaled distances. [ABSTRACT FROM AUTHOR]

Threats involving terrorist attacks using large amounts of explosives are less likely due to the complexity of acquiring them without alerting security agencies. A plausible threat tactic is to detonate small quantities of concealed explosives in contact with critical load-bearing structural members to compromise the structure's stability, leading to its partial or complete collapse. This paper investigates the response of reinforced concrete (RC) columns subjected to blast loads from a small standoff. Columns in buildings are commonly cladded for aesthetics or concealment and can thus be used to create a small standoff distance between the explosive and the column. In this study, three full-scale columns were subjected to blast loads from 115-g and 500-trinitrotoluene (TNT) charge masses placed at 50- and 100-mm standoff distances. The postblast residual axial load capacities of the damaged columns were obtained experimentally. The results were compared to benchmark results from RC columns subjected to the same explosive mass detonated in contact with the columns. The results of the experimental studies indicate that the small standoff distance significantly reduced the column damage. Furthermore, a validated LS-DYNA numerical model has been developed and used in parametric studies to evaluate the effects of various design parameters on the behavior of columns under blast loading. The predominant failure mode of columns subjected to blast loading at scaled distances below 0.1 m/kg1/3 was a local material failure in the core and shear/flexural failure when the scaled distance was above 0.1 m/kg1/3. The numerical results indicate that the Hopkinson–Cranz scaling law is not applicable at small-scaled distances. [ABSTRACT FROM AUTHOR]

Understanding the long-term creep behaviors of asphalt concrete core materials is crucial to the safety of embankment dams. This study systematically analyzes the creep behavior of asphalt concrete materials under a stepped loading path. Static triaxial tests are conducted to determine the stress–strain relation of asphalt concrete core materials. Both stepped loading and separate loading paths are applied on the asphalt concrete samples to analyze the difference between them in terms of the axial strain. To simulate the realistic temperature condition during the operation of dams, the temperature is set to 22.1°C. The test samples are subjected to four confining stresses (i.e., 0.1, 0.4, 0.7, and 1.0 MPa), and the stress levels are 0.2, 0.4, 0.5, and 0.8. For processing the test data obtained under the stepped loading path, the Boltzmann superposition method and Chen's method are applied. Then, the Burgers model is applied to estimate the stress and strain behaviors of the asphalt concrete materials. The results indicate that asphalt concrete materials characterize in primary and secondary creep stages. The data processed by Chen's method is much closer to the data of separate loading path than those processed by the Boltzmann method. The Burgers model describes well the creep behavior of the asphalt concrete materials. Thus, it can be applied in the estimation and analysis of the creep behaviors for embankment dams under long-term operation. [ABSTRACT FROM AUTHOR]

A new prediction formula is proposed to determine wave-induced pore pressure height distribution inside the core of rubble-mound breakwaters. Existing observed field and experimental data in the literature have been examined, and a valuable database has been obtained. Using dimensional analysis, a new wave damping parameter has been derived. In comparison with the existing empirical Biesel's formula, the proposed prediction formula directly takes into account the influence of the mean diameter of the core material, water depth, and important wave parameters such as incident wave height and wavelength, and there is no more necessity to assume appropriate values for the seepage coefficient and the material coefficient that are essentially needed for Biesel's formula. The new prediction formula presented here has its merits in providing an alternative form and insight into the physics of phenomena. [ABSTRACT FROM AUTHOR]

This paper describes the development and validation of a one-dimensional, large-strain consolidation-coupled contaminant transport model. The RCM-XPORT2 model uses the CS2 large-strain consolidation approach coupled with reactive advective/dispersive solute transport through a deforming saturated porous media, capped with a reactive sequestering geomaterial known as a reactive core mat (RCM). Validation of the model is presented by simulating consolidation-coupled contaminant transport experiments performed on naphthalene-spiked sediment from the Neponset River in Milton, Massachusetts. Finally, the paper presents a hypothetical case study of pre- and post-RCM application polychlorinated biphenyl (PCB) fate and transport in the Lower Neponset River using RCM-XPORT2 and U.S. EPA Water Quality Analysis Simulation Program surface water quality model. The Neponset River case study evaluates the long-term effect of sediment RCM capping on reducing the water column PCB concentration. [ABSTRACT FROM AUTHOR]

A new method is proposed for inhibiting the buckling response of steel braces. The strengthening technique involves attaching a core comprised of mortar blocks to the braces and then wrapping the entire system with carbon fiber-reinforced polymer (CFRP) sheets. An advantage of this method is that the technology can be applied in situ by a single individual with minimal training. Test results of seven specimens subjected to reversed axial loading show that it is feasible to achieve buckling restrained response up to 2% interstory drift. Other than the number of longitudinal fiber layers, it is observed that performance of the strengthening scheme depends upon the size of the core material, the presence of bond between the steel plate and core material, the existence of extra stitch plates for double angle members, and the presence of transverse CFRP layers at the member ends. It is also observed that double angle braces benefit more from the strengthening scheme than single angle braces, which are prone to premature out-of-plane buckling. [ABSTRACT FROM AUTHOR]

Because of superior speed and productivity, slip forms were extensively utilized as a potential formwork candidate in constructing concrete structures for the past few decades. Typical projects that employ this formwork technique are: Core of high-rise buildings, silos, telecommunication towers, cooling towers, heavy concrete offshore platforms, etc. The research presented in this paper aims at studying slip-form application to cores and silos, assessing its productivity, and determining its appropriate speed as well as auxiliary resource combinations. Simulation models are developed in which the potential control units in a slip-form system are described for cores and silos. Data are collected from several case study projects. A set of charts has been developed to predict productivity considering different stoppages, core cross section area, slipping (jacking) rate, and concrete placing methods. These charts play an essential role in managing slip-form application to cores and silos. Results show that the developed simulation models predict the productivity of case study projects with 99.70 and 99.30% accuracy for cores and silos, respectively. The presented research is relevant to both researchers and practitioners. It provides practitioners with charts that assist in scheduling and managing the required resources for slip-form application. In addition, it provides researchers with simulation models and framework for implementing slip forms to core and silo construction. [ABSTRACT FROM AUTHOR]

Conventional analysis methods for beams do not distinguish between transverse loads that are applied at the beam centroidal axis and those acting either above or below the centroidal axis. In contrast, this paper formulates a sandwich beam finite element solution which models the effect of load height relative to the centroidal axis. Towards this goal, the governing equilibrium equations and associated boundary conditions are derived based on a Timoshenko beam formulation for the core material. Special shape functions satisfying the homogeneous form of the equilibrium equations are derived and subsequently used to formulate exact stiffness matrices. By omitting the stiffness terms related to the faces, the formulation for a homogeneous Timoshenko beam can be recovered. Also, the Euler–Bernouilli counterpart of the formulation is recovered as a limiting case of the current Timoshenko beam formulation. Effects of load height relative to the centroid are observed to have similarities with those induced by axial forces in beam-columns. For a simply supported beam, downward acting loads located below the centroidal axis are found to induce a stiffening effect while those acting above the centroidal axis are found to induce a softening effect, resulting in higher transverse displacements. [ABSTRACT FROM AUTHOR]

Lightweight and heavy-duty fiber-reinforced polymer (FRP) composite honeycomb sandwich structures have been increasingly used in civil infrastructure. Unique cellular core configurations, such as sinusoidal core, have been applied in sandwich construction. Due to specific core geometry, the solutions for core effective stiffness properties are not readily available. This paper presents a mechanics of materials approach to evaluate the effective stiffness properties of sinusoidal cores. In particular, the internal forces of a curved wall in a unit cell are expressed in terms of resultant forces, and based on the energy method and principle of equivalence analysis, the in-plane stiffness properties of sinusoidal cores are derived. Both finite-element modeling and experimental testing are carried out to verify the accuracy of the proposed analytical formulation. To illustrate the present analytical approach as an efficient tool in optimal analysis and size selection of sinusoidal cores, several design plots are provided and discussed. The simplified analysis and formulation presented for sinusoidal cores can be used in design application of FRP honeycomb sandwich and optimization of efficient cellular core structures. [ABSTRACT FROM AUTHOR]

Presents a commentary on a study which deals with a continuum model for analysis of multiply connected perforated cores. Arguments raised in the study; Reaction from the authors of the study.