Horizontal Diaphragm Research Articles

Earthen masonry dwelling structures for extreme wind loads

Earthen masonry made of compressed and stabilized earth blocks (CSEBs) is emerging as a sustainable and locally appropriate construction material for affordable high-quality dwellings. Compelling features include the local availability and affordability of suitable soils, thermal insulation and humidity control properties, and small embodied energy compared with fired clay masonry. The mechanical properties of CSEBs have been the subject of several investigations. However, the research on the response and design optimization of CSEB masonry building structures is in its infancy, and a significant knowledge and technological gap exists with regard to resistance to extreme loads due to natural hazards (e.g., high winds and earthquakes). It is necessary to address this gap to understand whether engineered earth masonry can be enlisted to respond to the growing demand for hazard-resistant dwellings that are also affordable and sustainable.This paper discusses the feasibility of using earth masonry in low-rise dwelling structures to withstand extreme winds. Hurricanes and tornadoes periodically scourge vast areas in Central and North America and the Caribbean where low-income families live, and where the demand for sustainable construction meets that for structural resistance and affordability. Feasibility is studied based on the structural analysis of the main wind force resisting system (MWFRS) of a typical one-story single-family dwelling subject to wind pressures resulting from 3-s gust speeds up to 90m/s (324km/h). The output consists of parametric curves that relate wind speed with masonry compressive, tensile and shear strength demand for wall thicknesses ranging from 203 to 508mm. The structural adequacy of the MWFRS is assessed for the cases of flat and 15° gable roof. The design implications are discussed vis-à-vis strength reduction factors and design strength demands, and sustainable reinforcement options. It is concluded that it is feasible to design one-story CSEB masonry dwellings that can withstand winds loads from Category 4 hurricanes and EF3 tornadoes, provided that a rigid horizontal diaphragm is used. Grouted steel reinforcement may be used in safety shelter CSEB masonry structures to be designed for more extreme wind loads.

Pseudodynamic tests and earthquake response analysis of timber structures III: three-dimensional conventional wooden structures with plywood-sheathed shear walls

Pseudodynamic (PSD) tests were conducted on plywood-sheathed conventional Japanese three-dimensional (3D) wooden structures. Lateral load was applied to the edge beam of specimen structures to generate eccentricity loading. Specimens were based on a combination of shear walls with openings in the loading direction and horizontal diaphragms with different shear stiffness. The principle deformation of the horizontal diaphragm was torsion for rigid diaphragms and shear deformation for flexible diaphragms. Lumped-mass time-history earthquake response analysis was conducted on the tested structures, and additional calculations were conducted on structures with different eccentricity rates. Dynamic analyses were conducted by varying the masses and the resistance of the walls in the loading direction. The simulated peak displacement response in the loading plane agreed comparatively well with the PSD test results. The maximum displacement response on changing the wall resistant ratio showed almost the same tendency as that obtained by changing the mass ratio up to an eccentricity rate of 0.3; however, the maximum displacement response increased markedly beyond an eccentricity rate of 0.4. It was proved that the lumped-mass 3D model proposed in this study was appropriate for conducting a parameter study on the 3D dynamic behavior of timber structures.

A BASIC STUDY ON DYNAMIC PROPERTY AND SEISMIC RESPONSE OF TIMBER STRUCTURE WITH FLEXIBLE FLOOR AND UNI-AXIAL STIFFNESS ECCENTRICITY

Dynamic properties and seismic responses of timber structure are discussed, with focus on uni-axial stiffness eccentricity of structural walls and horizontal flexibility of floor diaphragm. The stiffness eccentricity factor Re defined in Japanese building standard law assumes rigid diaphragm, which can result in considerable error in estimations for torsional properties/responses of timber structures. Simplified formulations for the dynamic properties considering the diaphragm flexibility are given, and are applied to discuss seismic responses of example structures. The stiffness of horizontal diaphragm appears to affect not only the torsional response but also the translational response of the structure.

CALCULATION METHOD FOR ECCENTRICITY AND CORRECTION COEFFICIENT OF TORSIONAL ON CONSIDERATION WITH FLEXIBLE HORIZONTAL DIAPHRAGM

The current earthquake resistant design code for building in Japan, basically assumed a rigid horizontal diaphragm while calculating the eccentricity and correction coefficient of torsion. Such assumption may cause dangerous design while considering a flexible horizontal diaphragm with large eccentricity for real structure. Considering the shear deformation of floor, calculation method has been presented in this paper for eccentricity and correction coefficient of torsion. In elastic design, eccentric moment caused by earthquake force is generally resisted by the walls both X and Y directions, which in such case show rotation resist effect. Assuming the shear stiffness of the floor and the rotational resistant force from the wall to be in-series, formulae for calculating the eccentricity have been derived. These formulae also are verified by simulating an elastic one span model, using both static analyses and dynamic time history analyses.

Probabilistic Calibration and Experimental Validation of the Seismic Design Criteria for One-Story Concrete Frames

This article investigates the seismic performance of one-story reinforced concrete structures for industrial buildings. To this aim, the seismic response of two structural prototypes, a cast-in-situ monolithic frame and a precast hinged frame, is compared for four different levels of translatory stiffness and seismic capacity. For these structures an incremental nonlinear dynamic analysis is performed within a Monte Carlo probabilistic simulation. The results obtained from the probabilistic analysis prove that precast structures have the same seismic capacity of the corresponding cast-in-situ structures and confirm the overall goodness of the design criteria proposed by Eurocode 8, even if a noteworthy dependency of the actual structural behavior from the prescribed response spectrum is pointed out. The experimental verification of these theoretical results is searched for by means of pseudodynamic tests on full-scale structures. The results of these tests confirm the overall equivalence of the seismic behavior of precast and cast-in-situ structures. Moreover, two additional prototypes have been designed to investigate the seismic behavior of precast structures with roof elements placed side by side. The results of these further tests show that an effective horizontal diaphragm action can be activated even if the roof elements are not connected among them, and confirm the expected good seismic performance of these precast systems. Finally, the results of the experimental tests are compared with those obtained from nonlinear structural analyses. The good agreement between numerical and experimental results confirms the accuracy of the theoretical model and, with it, the results of the probabilistic investigation.

Analytical assessment of blast resistance of precast, prestressed concrete components

Protection against blast has become a high priority for many owners of structures. Blast retrofits/structural hardening, as with earthquake retrofits, can be costly. For this reason, it is important to understand that any structural element has an inherent capacity to absorb energy and resist some level of blast demand. A general evaluation that allows a designer to realize the absorption capacity of a structural element may preclude the need for a blast-specific retrofit. To illustrate this concept, blast resistances of non-loadbearing precast, prestressed concrete sandwich wall panels (PCSWP) are examined. These components are extensively used in modern construction for cladding of structural systems and often provide a significant level of protection from blast events. This paper examines the behavior of PCSWP subjected to blast loads. Four explosive experiments were performed on 4 sets of wall panels. An analytical model was developed and validated with the measured blast demands and peak displacements. The analytical model is used to predict wall-panel damage for varying levels of peak pressures and impulses. An extension of this method is proposed for assessing the blast resistance of horizontal diaphragm elements, such as double tees or hollow-core. An example analysis for a double-tee structural base system with a localized blast is provided.

梁ウェブ接合部分を補強した鋼構造柱梁接合部の力学性能に関する実験的研究

In this paper, the static characteristics of WF beam to SHS column connections that beam web connected parts were reinforced were investigated by cyclic loading test. The methods of reinforcement were inserting horizontal diaphragm or vertical stiffener inside panel zone. The main parameters were type of reinforcements, width-to-thickness ratio of the column and type of web connection. The test results shows that by reinforcing of web connected parts the maximum strength and the plastic deformation ability of the beam-to-column connection are getting better. The reasons are that the out-of-plane deformation of the column is restrained enough and the bending moment carrying ratio of web connected parts becomes large by reinforcement.

Monte Carlo simulation of the cold three-axis spectrometer PANDA

The cold three-axis spectrometer PANDA will be among the first instruments to start operating at the new neutron source in Munich. Monte Carlo simulations of neutrons passing the spectrometer have been performed in order to model the components of the neutron optics and provide information about the features of this new spectrometer in its different modes of operation. In a first step, simulations of the primary neutron flight path from the cold source to the sample were performed. The neutron optics consist of supermirror neutron guides, a variable horizontal in-pile diaphragm, optional collimators and a double-focusing monochromator. In order to model the different configurations of the spectrometer, the energy spectrum of the cold source, the transmission of the collimators and the reflectivity of the supermirrors have been taken into account. The simulations have been performed for several incident energies. The results of these simulations include the flux as well as the divergence and spatial distribution of the neutron intensity at the sample position.

Seismic Response of Light-Frame Wood Buildings

A general three-dimensional (3D) model of light-frame wood buildings is presented. The model has the capabilities of dealing with different structural configurations and different types of loading. Comprehensive verification studies are performed to check the accuracy of the model by comparing with some available experimental data. The proposed model shows excellent correlation with the experimental data. As an application, investigations are conducted to evaluate the seismic response of light-frame wood buildings with different geometric configurations. The effects of the asymmetric in-plane stiffness, dimensions of the horizontal diaphragm, the presence of partition walls, and the ground motion intensity on the structural response are studied. The corresponding load distribution of lateral forces among the shear walls and the deflections of horizontal diaphragms are the main parameters of this study. The application study indicates that rigidity of the horizontal diaphragm is influenced by its dimensions and that partition walls resist a substantial amount of seismic forces depending on their stiffness and the dimensions of the horizontal diaphragm.

Effect of horizontal diaphragm flexibility on the P-delta analysis

This paper investigates the importance of including the effects of the flexibility of the horizontal diaphragms when using the P-delta method of analysis, especially when considering the loads applied to intermediate frames on trusses that are not part of the lateral force resisting system. Analyses were conducted for structural systems with a variable number of stories, number of bays and diaphragm stiffnesses and supported by rigid jointed plane frames or vertical trusses.

Nonlinear finite element analysis of three-dimensional frames

This paper presents a numerical model for the nonlinear analysis of three-dimensional frames using the finite element method. The model is based on a general variational formulation for thin-walled beams with open or closed sections; the mathematical development uses an updated Lagrangian description for shallow arches, taking into account geometrical and material nonlinearities, residual stresses, member initial imperfections, warping, and connection flexibility. The model has been used to evaluate second-order effects and the influence of residual stresses and joint flexibility on the behavior of plane frames. A semirigid space frame has been analyzed and the gain in rigidity offered by a horizontal rigid diaphragm has been evaluated. Key words: analysis, connection, finite element, nonlinearity, residual stress, thin-walled beams, warping.

Diaphragm Height of Ejector of Uniform Sediment

Sediment entry into irrigation and hydropower canals may be controlled by a sediment excluder at canal headworks and/or a sediment ejector on the canal downstream of headworks. These devices take advantage of the fact that the bed‐load part of transported sediment in a stream moves near the bed and the suspended‐load part is distributed nonuniformly in a vertical column, with heavier concentrations near bed. The sediment ejector consists of a horizontal diaphragm slab, positioned slightly above the canal bed, and of ducts below the diaphragm flush the heavy sediment‐laden water into an escape channel. The present study concerns determination of diaphragm height of the ejector for uniform sediment, based on principles of sediment transportation. The diaphragm height should be such that suspended sediment load in the canal approaching the ejector above the diaphragm level should be equal to the total sediment transport capacity of the canal downstream of it. A correction factor is suggested to account for the effect of flow disturbance at the nose of the ejector. A design example has been worked out.

Wing-hearts in Mecoptera (insecta)

The accessory pulsatile organs for hemolymph circulation in the wings of 7 Mecoptera species were investigated by means of serial semi-thin sections, SEM and TEM. The wing-hearts are located in the dorsal meso- and metathorax, and have no connection to the aorta. Each wing-heart consists of a small hemolymph chamber formed above by the convex scutellum, and below by a horizontal muscular diaphragm. The chamber is connected to the posterior wing veins by a cuticular tube on each side of the body. The diaphragm (10–15 μm thick) is convex in cross-section and consists of transversely extended muscle fibers. Their ultrastructure reveals typical characters of myocardial and other visceral muscle fibers. The diaphragm muscle is innervated by a pair of thin nerves originating from the thoracic ganglion of each corresponding segment. The diaphragm is held in a convex position by numerous elastic strands (2 μm in diameter), which extend through the wing-heart lumen between the scutellum and the diaphragm. The diastolic phase of the wing-heart is caused by contraction of the diaphragm muscle fibers. Thus, the diaphragm flattens and hemolymph is drawn from the posterior wing veins. The systolic phase is caused by the elasticity of the suspending strands after relaxation of the muscle fibers. The elastic strands pull the diaphragm back into convex position and hemolymph is expelled out of the scutellum lumen into the thorax cavity through a valvular opening on the anterior side. The hemolymph flow from the posterior wing base to the scutellum lumen, was visualized by staining the hemolymph. In Panorpa communis the volume of the wing-heart lumen measures 1.6 × 10 −2 mm 3 in the mesothorax, and 1.2 × 10 −2 mm 3 in the metathorax. Each heartbeat transports a maximum of 65% of these volumes. The pumping frequency was 78 ± 20 beats per min, registered with a non-invasive photo-optical method in restrained animals. Corresponding pulsating movements occur as a passive phenomenon of wing-heart activity in a distinct area of the wing base. Only minor differences were found in the construction of wing-hearts among the investigated species, except for Boreus hyemalis, which lacks these accessory circulatory organs. The functional morphology of the wing-hearts in Mecoptera is compared with that of other Holometabola and aspects of the evolution of these organs are discussed.

Buckling considerations in the design of elevated steel water tanks

Improved fabrication techniques and the availability of higher strength steels have encouraged greater use of thin-walled containment vessels in recent years. A major increase in computing capability to analyse these structures for buckling modes has also occurred and this paper considers two recently constructed steel water towers. In particular, the effect of door cut-outs on buckling capacity is examined. The analysis techniques used in the paper provide powerful tools for readily estimating buckling modes and assessing the effects of various stiffener arrangements. By far the most effective stiffening element in the stem of a water tower is a horizontal diaphragm which maintains a circular cross-section.

Swimbladder Structure in Morid Cods (Pisces: Gadiformes)

Outgroup comparisons, and dissections of 19 species representing 16 morid genera, indicate that a complete horizontal membranous diaphragm within the posterior chamber of the swimbladder is a synapomorphy of the Moridae. The swimbladder of Pseudophycis differs from that of all other investigated morid genera in possessing lateral diverticula. The presence of lateral diverticula is interpreted as apomorphic and is probably a homoplasy.

Horizontal timber diaphragms for wind and earthquake resistance

This paper discusses the principles of horizontal timber diaphragm behaviour under in-plane loading, gives guidance on analysis, design and details, and reviews relevant research. Plywood, particle board and solid timber boarding are all relevant sheathing materials for wind and earthquake resistance, provided that appropriate stiffness is provided and the design provisions ensure that brittle failure modes are suppressed.

Multicomponent diffusion and vapor‐liquid equilibria of dilute organic components in aqueous sugar solutions

AbstractA technique for direct measurement of the differential diffusion coefficients in a ternary system of water, sugar, and a dilute organic species is described. The individual sugars were d‐fructose, d‐glucose, and sucrose; and ethyl alcohol, ethyl acetate, n‐butyl acetate, and n‐hexanal individually constituted the dilute organic species. The four ternary diffusivities were obtained over a range of sugar concentrations by the use of horizontal diaphragm cells, a differential interferometer, a flame‐ionization gas‐liquid chromatograph and postulation of the validity of the Onsager reciprocal relations. The equilibrium partial pressures of the dilute organic species over these solutions have also been measured, using a vapor head space chromatographic technique.

Testing a Light Gage Steel Hyperbolic Paraboloid Shell

Construction and testing of shell using standard light gage steel roof deck panels; panels are welded intermittently along their seams, and at external edges to light perimeter members; to form doubly curved shear carrying membrane; test indicates that shear values obtained from horizontal diaphragm testing can be used conservatively in design of curved shear surfaces and that rather light marginal members might be used, provided eccentricity in applying load to those members is avoided.