Regina Katsman

Model for Moisture-Content Evolution in Porous Building Elements with Hygro-Thermal Bridges and Air-Voids:

Addressing the effects of moisture movement and residual moisture-con tents is becoming a recognized part of performance-based design of buildings. However, the multi-directional moisture-movement and subsequent moisture-content evolution in most common building elements with hygro-thermal bridges, without or with air-voids, has yet not been investigated. An integral presentation was utilized to establish the coupled heat and mass transfer field equations for these cases, and for their reduction to a discrete set of alge braic equations. An interactive converging numerical process solves the implicit set of alge braic non-linear equations. Results address some examples for verification of the computational procedure, and a symmetric drying process of an autoclaved-aerated- concrete block-wall with cementitious-mortar joints and renderings, with and without air- voids.

Investigation of thermally-induced loads in modified bituminous roofing membranes

Abstract When exposed to various thermal conditions, installed roofing membrane experiences dimensional change, which creates induced, loads on the membrane material. These loads can cause a number of undesirable effects such as the membrane separating away from the parapet wall, seam components splitting, membrane tear at the vicinity of fasteners and membrane slag causing blistering. This paper deals with two kinds of thermally-induced loads, namely, reversible thermal expansion/contraction and irreversible stress releasing. The mechanisms for each type of induced load have been explored in detail on two membrane types of different internal structure. Thermal conditions are configured in the experiments to simulate typical Canadian summer and winter temperatures on a black roofing membrane surface. This study also explores the role of the membranes length and pre-loading on the induced loads. Based on limited data, some practical recommendations are given, such as regarding the influence of the induced loads in the membrane and on the performance integrity of the roofing assembly constructions when subjected to various exposure conditions.

The role of transport processes of particulate mercury in modifying marine anthropogenic secondary sources, the case of Haifa bay, Israel.

We have assessed the redistribution of a secondary source of sedimentary anthropogenic mercury in the Haifa bay (HB) area (SE Levantine basin), which is the northern sink for Nile-driven sand. A long-term (30years) ~80% decrease of the total sedimentary mercury concentrations (THg) was recorded in the inner bay, while an up to 3-fold increase was recorded in the top sediments of the outer bay. Sedimentary THg depth profiles and their temporal variability were used to model the main re-distribution processes, mainly resuspension associated with winter storm-derived transport. This mechanism transforms a secondary, sandy and well-aerated sink into a tertiary, more silty and hypoxic source at adjacent peripheral areas, affecting mercury bioavailability. We revisited the concept of environmental relaxation, i.e. the rate of return of a polluted environment to an acceptable state, showing that sedimentary transport processes may affect the associated ecological risks, mainly at shallow-water coastal sites.

The formation of graben morphology in the Dead Sea Fault, and its implications

The Dead Sea Fault (DSF) is a 1000 km long continental transform. It forms a narrow and elongated valley with uplifted shoulders showing an east-west asymmetry, which is not common in other continental transforms. This topography may have strongly affected the course of human history. Several papers addressed the geomorphology of the DSF, but there is still no consensus with respect to the dominant mechanism of its formation. Our thermomechanical modeling demonstrates that existence of a transform prior to the rifting predefined high strain softening on the faults in the strong upper crust and created a precursor weak zone localizing deformations in the subsequent transtensional period. Together with a slow rate of extension over the Arabian plate, they controlled a narrow asymmetric morphology of the fault. This rift pattern was enhanced by a fast deposition of evaporites from the Sedom Lagoon, which occupied the rift depression for a short time period.

Mapping the acoustical properties of the upper sedimentary layer in Lake Kinneret

A series of field experiments were conducted to estimate the effective acoustical properties of the bottom in Lake Kinneret (Israel). A wideband sound source (300 Hz to 2 kHz) was positioned at different ranges (1 m to 6 km) from a single hydrophone. Both local and long-range measurements of the sound field were carried out. All the acoustic data demonstrated a high reflectivity of the lake bottom at all grazing angles that is specific feature of gas-bearing sediments. Experimental sound pulses were compared with the simulated ones to obtain the values of effective sound speed in the sedimentary layer at different locations in the lake. Using a basic three component sediment’s model (water, rigid particles, and gas bubbles), the gas fraction in the bottom was estimated. A high correlation between the calculated gas fraction and previously measured organic matter concentration was observed. [Work was supported by ISF.]