Quantifying axial deformations of core shear walls using modal parameters

Differential axial deformation between column elements and shear wall elements of cores increase with building height and geometric complexity. Adverse effects due to the differential axial deformation reduce building performance and life time serviceability. Quantifying axial deformations using ambient measurements from vibrating wire, external mechanical and electronic strain gauges in order to acquire adequate provisions to mitigate the adverse effects is well established method. However, these gauges require installing in or on elements to acquire continuous measurements and hence use of these gauges is uneconomical and inconvenient. This motivates to develop a method to quantify the axial deformations. This paper proposes an innovative method based on modal parameters to quantify axial deformations of shear wall elements in cores of buildings. Capabilities of the method are presented though an illustrative example.

An analytical investigation into shear wall and slab interconnections between reinforced concrete modules for high -rise buildings utilising modular construction under extreme seismic and wind loading

This research investigates a new structural system utilising modular construction. Five-sided boxes are cast on-site and stacked together to form a building. An analytical model was created of a typical building in each of two different analysis programs utilising the finite element method (Robot Millennium and ETABS). The pros and cons of both Robot Millennium and ETABS are listed at several key stages in the development of an analytical model utilising this structural system. Robot Millennium was initially utilised but created an analytical model too large to be successfully run. The computation requirements were too large for conventional computers. Therefore Robot Millennium was abandoned in favour of ETABS, whose more simplistic algorithms and assumptions permitted running this large computation model. Tips are provided as well as pitfalls signalled throughout the process of modelling such complex buildings of this type. ^ The building under high seismic loading required a new horizontal shear mechanism. This dissertation has proposed to create a secondary floor that ties to the modular box through the use of gunwales, and roughened surfaces with epoxy coatings. In addition, vertical connections necessitated a new type of shear wall. These shear walls consisted of waffled external walls tied through both reinforcement and a secondary concrete pour. ^ This structural system has generated a new building which was found to be very rigid compared to a conventional structure. The proposed modular building exhibited a period of 1.27 seconds, which is about one-fifth of a conventional building. The maximum lateral drift occurs under seismic loading with a magnitude of 6.14 inches which is one-quarter of a conventional building's drift. The deflected shape and pattern of the interstorey drifts are consistent with those of a coupled shear wall building. In conclusion, the computer analysis indicate that this new structure exceeds current code requirements for both hurricane winds and high seismic loads, and concomitantly provides a shortened construction time with reduced funding. ^

A new measure to quantify chest wall deformity in scoliosis patients : does rib hump measurement correlate with anterior chest wall deformity post surgery?

The primary aims of scoliosis surgery are to halt the progression of the deformity, and to reduce its severity (cosmesis). Currently, deformity correction is measured in terms of posterior parameters (Cobb angles and rib hump), even though the cosmetic concern for most patients is anterior chest wall deformity. In this study, we propose a new measure for assessing anterior chest wall deformity and examine the correlation between rib hump and the new measure. 22 sets of CT scans were retrieved from the QUT/Mater Paediatric Spinal Research Database. The Image J software (NIH) was used to manipulate formatted CT scans into 3-dimensional anterior chest wall reconstructions. A ‘chest wall angle’ was then measured in relation to the first sacral vertebral body. The chest wall angle was found to be a reliable tool in the analysis of chest wall deformity. No correlation was found between the new measure and rib hump angle. Since rib hump has been shown to correlate with vertebral rotation on CT, this suggests that there maybe no correlation between anterior and posterior deformity measures. While most surgical procedures will adequately address the coronal imbalance & posterior rib hump elements of scoliosis, they do not reliably alter the anterior chest wall shape. This implies that anterior chest wall deformity is to a large degree an intrinsic deformity, not directly related to vertebral rotation.

Intracardiac acoustic radiation force impulse (ARFI) and shear wave imaging in pigs with focal infarctions.

Four pigs, three with focal infarctions in the apical intraventricular septum (IVS) and/or left ventricular free wall (LVFW), were imaged with an intracardiac echocardiography (ICE) transducer. Custom beam sequences were used to excite the myocardium with focused acoustic radiation force (ARF) impulses and image the subsequent tissue response. Tissue displacement in response to the ARF excitation was calculated with a phase-based estimator, and transverse wave magnitude and velocity were each estimated at every depth. The excitation sequence was repeated rapidly, either in the same location to generate 40 Hz M-modes at a single steering angle, or with a modulated steering angle to synthesize 2-D displacement magnitude and shear wave velocity images at 17 points in the cardiac cycle. Both types of images were acquired from various views in the right and left ventricles, in and out of infarcted regions. In all animals, acoustic radiation force impulse (ARFI) and shear wave elasticity imaging (SWEI) estimates indicated diastolic relaxation and systolic contraction in noninfarcted tissues. The M-mode sequences showed high beat-to-beat spatio-temporal repeatability of the measurements for each imaging plane. In views of noninfarcted tissue in the diseased animals, no significant elastic remodeling was indicated when compared with the control. Where available, views of infarcted tissue were compared with similar views from the control animal. In views of the LVFW, the infarcted tissue presented as stiff and non-contractile compared with the control. In a view of the IVS, no significant difference was seen between infarcted and healthy tissue, whereas in another view, a heterogeneous infarction was seen to be presenting itself as non-contractile in systole.

Process Modelling for Control of Product Wall Thickness in Thermoforming

The present paper describes the results of an investigation into the modelling of plug assisted thermoforming. The objective of this work was to improve the finite element modelling of thermoforming through an enhanced understanding of the physical elements underlying the process. Experiments were carried out to measure the effects on output of changes in major parameters and simultaneously simple finite element models were constructed. The experimental results show that the process creates conflicting and interrelated contact friction and heat transfer effects that largely dictate the final wall thickness distribution. From the simulation work it was demonstrated that a high coefficient of friction and no heat transfer can give a good approximation of the actual wall thickness distribution. However, when conduction was added to the model the results for lower friction values were greatly improved. It was concluded that further work is necessary to provide realistic measurements and models for contact effects in thermoforming.

Morphometric analysis of tracheary elements in four Portulaca species

This paper deals with the morphological features of the tracheary elements of the vegetative organs in four Portulaca species (Portulaca hirsutissima Camb., P. halimoides L., P. wedermannii Poelln. and P. mucronata Link.) occurring in Southeast and Northeast Brazil. The vessel elements are small (< 25 mu m) and with simple perforation plate. The pattern of wall thickening varied from bordered pitting (in roots) to scalariform and helicoidal (stem and leaves). Statistical methods show variation in vessel-element diameter in different vegetative organs; wider elements were observed in roots. Tracheids occurring in leaves of P. hirsutissima and P. wedermannii, have morphological features that are similar to terminal tracheids or tracheoid idiolasts frequently associated with xerophytes. The paedomorphic features (juvenlism) observed here may be related, in part, to aspects of water transport and storage as described in Cactaceae.

Microgranitic Enclaves as Products of Self-mixing Events: a Study of Open-system Processes in the Maua Granite, Sao Paulo, Brazil, Based on in situ Isotopic and Trace Elements in Plagioclase

Felsic microgranular enclaves with structures indicating that they interacted in a plastic state with their chemically similar host granite are abundant in the Maua Pluton, SE Brazil. Larger plagioclase xenocrysts are in textural disequilibrium with the enclave groundmass and show complex zoning patterns with partially resorbed An-rich cores (locally with patchy textures) surrounded by more sodic rims. In situ laser ablation-(multi-collector) inductively coupled plasma mass spectrometry trace element and Sr isotopic analyses performed on the plagioclase xenocrysts indicate open-system crystallization; however, no evidence of derivation from more primitive basic melts is observed. The An-rich cores have more radiogenic initial Sr isotopic ratios that decrease towards the outermost part of the rims, which are in isotopic equilibrium with the matrix plagioclase. These profiles may have been produced by either (1) diffusional re-equilibration after rim crystallization from the enclave-forming magma, as indicated by relatively short calculated residence times, or (2) episodic contamination with a decrease of the contaminant ratio proportional to the extent to which the country rocks were isolated by the crystallization front. Profiles of trace elements with high diffusion coefficients would require unrealistically long residence times, and can be modeled in terms of fractional crystallization. A combination of trace element and Sr isotope data suggests that the felsic microgranular enclaves from the Maua Pluton are the products of interaction between end-member magmas that had similar compositions, thus recording `self-mixing` events.

Noble metals and associated trace elements in sulfides from the active TAG mound, ODP Site 158-957

Primary sulfides from cores of ODP Holes 158-957M, 158-957C, and 158-957H on the active TAG hydrothermal mound (Mid-Atlantic Ridge, 26°08'N) have been studied for concentrations of several chemical elements. Based on 262 microprobe analyses it has been found that the sulfides have extremely heterogeneous distribution of noble metals (Au, Ag, Pt, and Pd) and several associated elements (Hg, Co, and Se). Noble metals are arranged in the following order in terms of decreasing abundance, i.e. concentration level above detection limits (the number of analyses containing a specific element is given in parentheses): Au (65), Ag (46), Pt (21), and Pd (traces). The associated trace elements have the following series: Co (202), Hg (132), and Se (49). The main carriers of "invisible" portion of the noble metals are represented by pyrite (Au, Hg), marcasite and pyrite (Ag, Co), sphalerite and chalcopyrite (Pt, Pd), and chalcopyrite (Se). Noble metal distribution in sulfides reveals a lateral zonality: maximal concentrations and abundance of Au in chalcopyrite (or Pt and Ag in chalcopyrite and pyrite) increase from the periphery (Hole 957H) to the center (holes 957C and 957M) of the hydrothermal mound, while Au distribution in pyrite displays a reversed pattern. Co concentration increases with depth. Vertical zonality in distribution of the elements mentioned above and their response to evolution of ore genesis are under discussion in the paper.

Concentrations of tektites and chemical elements in sediments from ODP Holes 121-758B and 124-769A

Recently published studies of Ocean Drilling Project (ODP) cores from near southeast Asia revealed microtektite contents much higher than those in previously studied cores, suggesting that Ir contents might be enhanced in the tektite-bearing horizons. We determined a positive Ir anomaly in ODP core 758B from the Ninetyeast Ridge, eastern Indian Ocean; the peak Ir concentration of 190 pg/ g was ~2X the continuum level. The net Ir fluence is 1.8+/-0.5 ng/cm**2 over the depth interval from 10.87 to 11.32 m; a small additional peak also associated with microtektites contributes another 0.5 ng Ir/cm**2. Concentrations of Ir in core 769A show more scatter, but a small Ir enhancement is associated with the peak microtektite abundance; our best estimate of the poorly constrained fluence is 1.3+/-0.7 ng/cm**2. Data on deep-sea cores show that the microtektite fluence falls exponentially away from southeast Asia, the fluence dropping a factor of 2 in ~400 km. In southeast Asia the trend merges with a roughly estimated mass fluence of ~1.1 g/cm**2 inferred from evidence of a melt sheet in northeast Thailand. Integration of the inferred distribution yields a total mass of Australasian tektites of 3.2x10**16 g, much higher than previous estimates. Assuming a similar fallout distribution for the impactor and a chondritic composition allows us to calculate its mass to be 1.5x10**15 g, about 3 orders of magnitude smaller than the minimum mass of the impactor responsible for the extinctions at the end of the Cretaceous.

Turgor Regulation via Cell Wall Adjustment in White Spruce1

Turgor regulation at reduced water contents was closely associated with changes in the elastic quality of the cell walls of individual needles and shoots of naturally drought-resistant seedlings of white spruce (Picea glauca [Moench] Voss.) and of seedlings of intermediate resistance that had been pretreated with paclobutrazol, a stress-protecting, synthetic plant-growth regulator. Paclobutrazol-treated seedlings showed marked increases in drought resistance, and pressure-volume analysis combined with Chardakov measurements confirmed observations that water stress was ameliorated during prolonged drought. Turgor was maintained in the paclobutrazol-treated and in the naturally resistant drought-stressed seedlings despite water contents near or below the turgor-loss volumes of well-watered controls. The maintenance of turgor in these seedlings was in large part a function of the dynamic process of cell wall adjustment, as reflected by marked reductions in both the saturated and turgor-loss volumes and by large increases in the elastic coefficients of the tissues. Shear and Young's moduli, calculated from pressure-volume curves and the radii and wall thicknesses of mesophyll cells, also confirmed observed changes in the elastic qualities of the cell walls. Elastic coefficients of well-watered, paclobutrazol-treated seedlings were consistently larger than those in well-watered controls and several times larger than the values in untreated plants, which succumbed rapidly to drought. In contrast, untreated seedlings that withstood prolonged drought without wilting displayed elastic coefficients similar to those in seedlings that had been treated with paclobutrazol but that had not been exposed to drought.

A numerical method to quantify the axial shortening of vertical elements in concrete buildings

Differential axial shortening, distortion and deformation in high rise buildings is a serious concern. They are caused by three time dependent modes of volume change; “shrinkage”, “creep” and “elastic shortening” that takes place in every concrete element during and after construction. Vertical concrete components in a high rise building are sized and designed based on their strength demand to carry gravity and lateral loads. Therefore, columns and walls are sized, shaped and reinforced differently with varying concrete grades and volume to surface area ratios. These structural components may be subjected to the detrimental effects of differential axial shortening that escalates with increasing the height of buildings. This can have an adverse impact on other structural and non-structural elements. Limited procedures are available to quantify axial shortening, and the results obtained from them differ because each procedure is based on various assumptions and limited to few parameters. All these prompt to a need to develop an accurate numerical procedure to quantify the axial shortening of concrete buildings taking into account the important time varying functions of (i) construction sequence (ii) Young’s Modulus and (iii) creep and shrinkage models associated with reinforced concrete. General assumptions are refined to minimize variability of creep and shrinkage parameters to improve accuracy of the results. Finite element techniques are used in the procedure that employs time history analysis along with compression only elements to simulate staged construction behaviour. This paper presents such a procedure and illustrates it through an example. Keywords: Differential Axial Shortening, Concrete Buildings, Creep and Shrinkage, Construction Sequence, Finite Element Method.