Design of Metal Building Roof Purlins Including System Reliability Effects

Final Project ReportThis report provides a framework to incorporate structural system reliability effects in the design of roof purlins in a typical metal building. Today every roof purlin is considered as a separate component and the effect of spatial variation in the demand loads and potential redistribution and load sharing in the roof system capacity are ignored in design. Component reliability is established by first-order reliability methods implemented through load and resistance factor design. Based on recent work in loading bearing cold-formed steel framing systems the load and resistance factor design framework is extended from components to systems through an additional resistance factor to account for system influence. An archetypical metal building is designed and selected for this study. Monte Carlo simulations of a segment of the metal building roof are performed with consideration of both randomness in the demands and capacity and employing geometric and material nonlinearity in the response model of the roof. The simulations indicate that the system effect in metal building roofs is beneficial, and increases in the design capacity when evaluated against demands may be appropriate. Sensitivity to the target reliability (allowed probability of failure), deflection limits, and modeling assumptions are observed and discussed. Preliminary factors to account for roof system reliability are provided.Metal Building Manufacturers Association (MBMA

Cyclic Performance and Behavior Characterization of Steel Deck Sidelap and Framing Connections

A wide variety of steel deck sidelaps and framing connections have been experimentally studied to characterize the cyclic performance required in seismic evaluation of steel deck diaphragms. This study intends to provide cyclic test results of common steel deck connections including screw nestable and top arc seam sidelaps; and powder actuated fasteners, arc spot weld, and arc seam weld framing connections. A total of 24 sidelap and 36 framing connection tests have been performed in the Thin-Walled Structures Laboratory at Johns Hopkins University by NBM Technologies. The connection test results have been used to parameterize a nonlinear hysteretic spring element (i.e. utilizing the Pinching04 material model) applicable to modeling of the connections in high fidelity steel deck diaphragms to evaluate the seismic behavior of the steel deck diaphragm in rigid wall flexible diaphragm buildings, where inelasticity and ductility of the building system are intended to be derived largely from the diaphragm and the connections. Finally, the test results have been compared to AISI 310 and DDM04 connection strength and stiffness predictions. This experimental program is a task within a larger effort, i.e. “Advancing Seismic Provisions for Steel Diaphragm in Rigid Wall - Flexible Diaphragm Buildings” by NBM Technologies. The object of the larger effort is to investigate alternative seismic design provisions for conventionally designed steel diaphragms in Rigid Wall - Flexible Diaphragm Buildings

Effect of Connection Details on the Cyclic Behavior of Nestable Screw Sidelaps

The connection strength and stiffness sensitivity of screwed sidelaps in nestable steel decks to screw installation details has been experimentally explored via cyclic testing. The cyclic behavior of sidelaps has been recently incorporated in the high fidelity modeling and seismic evaluation of the steel deck diaphragm in rigid wall - flexible diaphragm buildings, where “unzipping” a sidelap (loss of a significant number of sidelap connections along a deck edge) could significantly reduce the seismic performance of the whole diaphragm. A total of 24 monotonic and cyclic sidelap tests have been performed in the Thin-Walled Structures Laboratory at Johns Hopkins University. Two different screw edge distances, three different deck thicknesses (i.e. 18 gauge 20 gauge, and 22 gauge), and two different screw sizes were included in the test matrix. The screws were installed either “close to the edge” or “far from the edge”. For the “close to the edge” condition the typical 1.5d edge distance limitation in the design specification was not satisfied. Both monotonic and cyclic test results show that the strength of the sidelap connection can be correlated to edge distance and screw installation details. A maximum 25% and 19% difference in the ultimate strength of the screw sidelaps were observed in monotonic and cyclic tests, respectively. The rest results were compared to sidelap strengths in the literature, and potential changes to sidelap strength predictions and installation methods are discussed

Reduced Order Models for Profiled Steel Diaphragm Panels

The objective of this paper is to provide progress on development and validation of reduced order models for the in plane strength and stiffness of profiled steel panels appropriate for use in structural models of an entire building. Profiled steel panels, i.e, metal deck, often serve as a key distribution element in building lateral force resisting systems. Acting largely as an in-plane shear diaphragm, metal deck as employed in walls, roofs, and floors plays a key role in creating and driving three-dimensional building response. As structural modeling evolves from two-dimensional frameworks to fully three-dimensional buildings, accurate and computationally efficient models of profiled steel panels are needed. Three-dimensional building response is increasingly required by ever-evolving structural standards, particularly in seismic design, and structural efficiency demands that the benefits of three-dimensional response be leveraged in design. Equivalent orthotropic plate models provide a potential reduced order model for profiled steel panels that is investigated in this paper. A recent proposal for the rigidities in such a model are assessed against shell finite element models of profiled steel panels. In addition, the impact of discrete connections and discrete panels, as occurs in an actual roof system, are assessed when applying these reduced order models. Extension of equivalent orthotropic plate models to elastic buckling and strength, in addition to stiffness, both represent work in progress, but initial results are provided. Examples show that equivalent orthotropic plate models must be used with care to yield useful results. This effort is an initial step in developing efficient whole building models that accurately incorporate the behavior of profiled steel panels as diaphragms

Holographic Hydrodynamics of {\it Tilted} Dirac Materials

We present a gravity dual to a quantum material with tilted Dirac cone in 2+1 dimensional spacetime. In this many-body system the electronics degrees of freedom are strongly-coupled, constitute a Dirac fluid and admit an effective hydrodynamic description. The holographic techniques are applied to compute the thermodynamic variables and hydrodynamic transports of a fluid on the boundary of an asymptotically anti de Sitter spacetime with a boosted black hole in the bulk. We find that these materials exhibit deviations from the normal Dirac fluid which rely on the tilt of the Dirac cone. In particular, the shear viscosity to entropy density ratio is reduced and the KSS bound is violated in this system. This prediction can be experimentally verified in two-dimensional quantum materials ({\it e.g.} organic $\alpha$-({BEDT}-{TTF})$_2$I$_3$ and $8Pmmn$ borophene) with tilted Dirac cone.Comment: 7 two-column page

Electron Currents from Gradual Heating in Tilted Dirac Cone Materials

Materials hosting tilted Dirac/Weyl fermions upgrade the solid-state phenomena into a new spacetime structure. They admit a geometric description in terms of an effective spacetime metric. Using this metric that is rooted in the long-distance behavior of the underlying lattice, we formulate the hydrodynamics theory for tilted Dirac/Weyl materials in $2+1$ spacetime dimensions. We find that the mingling of space and time through the off-diagonal components of the metric gives rise to: (i) heat and electric currents proportional to the "temporal" gradient of temperature, $\partial_t T$ and (ii) a non-zero Hall conductance $\sigma^{ij}\propto \zeta^i\zeta^j$ where $\zeta^j$ parametrizes the tilt in $j$'th space direction. The finding (i) above that can be demonstrated in the laboratory, suggests that thanks to the non-trivial spacetime geometry in these materials, naturally available sources of $\partial_t T$ in hot deserts offer a new concept for the conversion of sunlight heating into electric energy. We further find a tilt-induced non-Drude contribution to conductivity which can be experimentally disentangled from the usual Drude pole

An Archetype Mid-Rise Building for Novel Complete Cold-Formed Steel Buildings

This paper introduces an archetype mid-rise cold-formed steel (CFS) building that aids in assessing the limits of current structural solutions, particularly lateral force resisting systems, and also in the development of new CFS technologies. A unified archetype building provides a platform for comparing the performance of new lateral force resisting systems to existing ones. The study herein provides quantitative evaluation of the design limitations of a typical “complete” cold-formed steel building (i.e. only cold-formed steel based elements are used for all gravity and lateral force resisting systems) at different heights (4 through 20 stories) located in a high seismic zone. The primary focus is the seismic force resisting system, which is limited to shear wall systems detailed in AISI specifications. The archetype buildings are designed using ASCE7-10 for all required loads and load combinations; and the CFS framing systems are designed utilizing AISI specifications, particularly AISI-400-15. Limitations in the application of current specifications for designing mid-rise cold-formed steel buildings are provided, and the potential for further studies discussed

Substituting Sodium Hydrosulfite with Sodium Metabisulfite Improves Long-Term Stability of a Distributable Paper-Based Test Kit for Point-of-Care Screening for Sickle Cell Anemia

Sickle cell anemia (SCA) is a genetic blood disorder that is particularly lethal in early childhood. Universal newborn screening programs and subsequent early treatment are known to drastically reduce under-five SCA mortality. However, in resource-limited settings, cost and infrastructure constraints limit the effectiveness of laboratory-based SCA screening programs. To address this limitation our laboratory previously developed a low-cost, equipment-free, point-of-care, paper-based SCA test. Here, we improved the stability and performance of the test by replacing sodium hydrosulfite (HS), a key reducing agent in the hemoglobin solubility buffer which is not stable in aqueous solutions, with sodium metabisulfite (MS). The MS formulation of the test was compared to the HS formulation in a laboratory setting by inexperienced users (n = 3), to determine visual limit of detection (LOD), readout time, diagnostic accuracy, intra- and inter-observer agreement, and shelf life. The MS test was found to have a 10% sickle hemoglobin LOD, 21-min readout time, 97.3% sensitivity and 99.5% specificity for SCA, almost perfect intra- and inter-observer agreement, at least 24 weeks of shelf stability at room temperature, and could be packaged into a self-contained, distributable test kits comprised of off-the-shelf disposable components and food-grade reagents with a total cost of only $0.21 (USD)

FastFloor Residential Testing Report

The goal of the FastFloor Residential project is to create a new floor system that is lightweight, fast to construct and nonproprietary. FastFloor Residential strives to achieve this by using 3 in. deep steel deck of 18 gauge that is fastened back-to-back to create a cellular deck. The cellular deck is then topped with a cementitious panel that is screwed to the steel deck. A series of physical four-point bending tests on this unique cellular steel deck composite with cementitious panels floor system were conducted in the Thin-Walled Structures Lab at Johns Hopkins University. The goal of the testing is to understand the behavior of the composite action between the steel deck and cementitious panel, identify the failure modes, and evaluate the strength and stiffness of the composite floor system.American Institute of Steel Construction (AISC), Steel Deck Institute (SDI