Strain Concentration Ratio Analysis of Different Waterproofing Materials during Concrete Crack Movement

When a crack occurs under an installed waterproofing material and moves due to environmental effects (freeze–thaw, settlement, vibration, dead load, etc.), waterproofing materials without adequate elongation or tensile strength properties may break and tear. To enable the selection of materials with proper response against the strain that occur during crack movement, this study proposes and demonstrates a new evaluation method for determining and comparing strain concentration of waterproofing materials under the effect of concrete crack movement. For the proposed testing method and demonstration, three common types of waterproofing material types were selected for testing, poly-urethane coating (PUC), self-adhesive asphalt sheet (SAS) and composite asphalt sheet (CAS). Respective materials are installed with strain gauges and applied onto a specimen with a separated joint that undergoes concrete crack movement simulation. Each specimen types are subject to repeated movement cycles, whereby strain occurring directly above the moving joint is measured and compared with the strain occurring at the localized sections (comparison ratio which is hereafter referred to as strain concentration ratio). Specimens are tested under four separate movement length conditions, 1.5 mm, 3.0 mm, 4.5 mm and 6.0 mm, and the results are compared accordingly. Experimental results show that materials with strain concentration ratio from highest to lowest are as follows: PUC, SAS and CAS.

Statistical Time Series Analysis of Crack Movements at Bayon Main Tower, Cambodia

Based on the past monitoring data of crack movements and various weather conditions by JASA (Japanese Government Team of Safeguarding Angkor), we quantitatively examine about the effects of each weather conditions to each crack movements at Bayon main tower. Then, we applied the time series analysis using a state-space representation in the examination. In the model of the state-space representation, the factors of crack movement are assumed as temperature, wind velocity and rainfall. Those quantitative examinations of crack movements will be necessary for the planning of reinforcement and restoration at Bayon main tower.

A Fracture Surface Rotation Mechanism for Fatigue Tested 2219-T87 Aluminum Sheet

Fatigue crack propagation tests were conducted on 2219-T87 aluminum sheet to identify the factors that control the rate of fracture surface rotation. Center-cracked, axial loaded specimens were tested in air at room temperature using tension-tension loading. The log (da/dn) versus (ΔK) curve contained an inflection point that was associated with the flat to slant fracture transition. The size and shape of the plastic zone at the crack tip were determined as a function of the half-crack length by using optical interferometry. It was found that the rate of fracture surface rotation was controlled by the changing size of the crack tip plastic zone. It is proposed that fracture surface rotation in this material occurs by a process of crack movement within active slip zones. A discussion is given on the deformation mechanisms associated with fatigue fracture surface rotation.

Design, construction, and performance of a slurry trench wall next to foundations

The stability of excavations adjacent to existing structures is an engineering problem and challenge. With the amount of construction increasing many such excavations are being planned and constructed. This paper documents the design, construction, and performance of a tied-back retaining system constructed by the slurry trench method. The system was necessary to retain the sides of a 30-ft (9.1-m) deep cut in glacial till immediately adjacent to the heavily loaded foundations of historically important and settlement sensitive structures. The main structures next to the excavation included the façade of the south transept and the 266-ft (81.1-m) high steeple of St. Jacques Church. Foundation loads imposed by these structures vary from 5.5 to 6.5 tons/ft2 (527–622 kPa)at a depth of 5 ft (1.5 m) below ground level. The slurry trench, up to 50 ft (15.3 m) in depth, approached to within 8 ft (2.44 m) of these foundations. Excavation was in two stages with tiebacks holding the wall at each level. The slurry trench and surrounding structures were instrumented using settlement points, crack movement devices, horizontal measurement points, inclinometers, and load cells. The soil investigation and design methods adopted are described.