Priyan Mendis

Plastic Hinge Lengths of Normal And High-strength Concrete In Flexure

Full-range analysis methods are becoming popular in design of reinforced concrete structures. These methods require a knowledge of the behaviour of plastic hinges up to advanced curvatures. Concrete sections characteristically soften beyond the plastic phase. To analyse a strain-softening structure, many researchers have used a finite hinge length. In this paper, existing formulae are re-examined and the effects of different variables on hinge length are discussed. Experimentally measured values are compared with the values predicted by using these formulae. It is shown that the upper and lower bounds suggested by the ACI committee 428 provide reliable estimates of hinge lengths for both normal and high-strength concrete flexural hinges up to 80 MPa.

MEASUREMENT AND ANALYSIS OF ELECTROMAGNETIC FIELDS FROM TRAMS, TRAINS AND HYBRID CARS

Electricity is used substantially and sources of electric and magnetic fields are, unavoidably, everywhere. The transportation system is a source of these fields, to which a large proportion of the population is exposed. Hence, investigation of the effects of long-term exposure of the general public to low-frequency electromagnetic fields caused by the transportation system is critically important. In this study, measurements of electric and magnetic fields emitted from Australian trams, trains and hybrid cars were investigated. These measurements were carried out under different conditions, locations, and are summarised in this article. A few of the measured electric and magnetic field strengths were significantly lower than those found in prior studies. These results seem to be compatible with the evidence of the laboratory studies on the biological effects that are found in the literature, although they are far lower than international levels, such as those set up in the International Commission on Non-Ionising Radiation Protection guidelines.

Effects of architecture on ballistic resistance of textile fabrics: Numerical study:

Composite textiles composed of materials such as Kevlar, Dyneema and Zylon are extensively used in many force/impact protection applications, such as body armor, and automobile and airplane engine fragment resistant containment. Significant effort has been devoted to ballistic testing of composite fabrics made from various manufacturing processes and designs. Performing comprehensive ballistic and impact tests for these composite textiles is a very time-consuming and costly task. Numerical models are presented in this research, thereby providing predictive capability for the manufacturer and designer to minimize field testing, as well as shedding light on to the damage mechanisms of composite fabrics subjected to ballistic impact. Several representative composite fabric architectures (such as plain weave, basket weave and knitted fabrics) are generated for finite element analysis. Numerical investigation is conducted on these fabric structures of the same mass per unit area subjected to projectile impacts. Failure patterns of woven and knitted fabrics obtained from numerical simulations are compared with those observed experimentally. Performances of the representative textile structures are evaluated based on the resultant velocity of the projectile, as well as various energy components. The influences of yarn–yarn and yarn–projectile friction properties on the ballistic performance of various textile structures are presented. To highlight the effects of projectile geometry and angular rotation on the fracture of woven and knitted fabrics, a series of simulations are also performed with three distinctive projectiles of the same mass and impact energy.

Interior wide beam connections subjected to lateral earthquake loading

Abstract The use of wide beam–column systems has become increasingly popular in low to moderate seismic regions, despite very little information being available on their performance under seismic action. Therefore, this investigation was conducted to determine the behavior and likely failure mode of wide beam connections when subjected to earthquake loading. In this investigation, two interior reinforced concrete wide beam subassemblages and one post-tensioned concrete wide beam subassemblage were tested under quasi-static cyclic loading up to a drift ratio of 3.5%. It was found that the wide beam connection is likely to experience severe torsion cracking in the beam portions located at the sides of the column when subjected to severe earthquake loading. A special detailing strategy was developed to inhibit the torsion cracking and was found to be effective in the subsequent tests. The experimental behavior of the subassemblages is reported in this paper.

A framework for a microscale flood damage assessment and visualization for a building using BIM–GIS integration

Flood damage assessment (FDA) is a key component of risk-based method for flood management. In the current FDA approaches, generally the uniqueness of the building is disregarded in the analysis. Therefore, they are unfit for detailed applications in which case-by-case analysis of building damage is an essential requirement. This limitation is compounded by the use of incomplete and often low-quality data inputs about the building and the assumptions and approximations made regarding the geometry and materials of its components. Such shortcomings may result in incomplete and uncertain outcomes. Considering the benefits and increasing use of three-dimensional (3D) urban modeling and Building Information Model in various urban management processes, in this paper, an integrated framework for utilization of detailed 3D building models for the assessment and 3D visualization of flood damage to building according to its distinct behavior against flood is presented. A proof-of-concept demonstration of the framework in a case study underlined the feasibility of implementation of the framework, which can potentially benefit a variety of users and be used as a complementary approach to the current FDA methods for improving the resilience of the community toward floods and their adverse impacts.

Reinforced Concrete Interior Wide-Band Beam-Column Connections Subjected to Lateral Earthquake Loading

This paper presents experimental results from quasistatic cyclic lateral load tests on 2 half-scale reinforced concrete interior wide-band beam-column subassemblages. The 1st connection is detailed without any special provision for seismicity, and the 2nd connection is similarly detailed with a few modifications that are shown to improve the performance of the connection. The 2nd connection includes a unique detailing strategy involving the debonding of reinforcing bars to prevent the formation of undesirable torsion and shear cracks. This connection is shown to perform very well up to the maximum applied 4% nominal drift; thus, a recommendation is made that limits on beam width in regions of high seismicity could be removed from current design codes if the unique detailing strategy is employed.

Elastomeric polymers for retrofitting of reinforced concrete structures against the explosive effects of blast

The main distinction of blast load from other types of dynamic loadings is its impulsive nature, where the loads usually act for a very short duration but transmit very high impulsive pressures. This paper presents an overview of the present retrofitting techniques in use to enhance the capacity of structural elements to withstand the effects of blast loads, and introduces an alternative retrofitting approach by utilizing polymer coatings. The authors have demonstrated the positive effects of this approach by conducting a numerical investigation on the behavior of an unretrofitted reinforced concrete panel subjected to the blast load from a 2 kg charge at 1.6 m stand-off distance, and subsequently comparing its performance with several polymer coated panels. The analysis was performed by using an explicit nonlinear finite element (FE) code. The results demonstrate the contributions of this technique in terms of panel displacement control and energy dissipation. Considering that the polymer coating can also act as a protective layer in improving the durability of structural materials, this technique can also be optimized favorably to enhance the overall sustainability of structures.

Experiences of Deploying an Indoor Building Sensor Network

Monitoring and automatic control of building environment is a crucial application of Wireless Sensor Network (WSN) in which maximizing network lifetime is a key challenge. We investigate the link quality distribution to obtain full coverage of signal strength in a single floor of building environment, experimentally. Our results confirmed the transitional region is particular concern in wireless sensor network since it accommodates high variance unreliable links. The reason due to this transitional region in inside building environment could be the obstacles including concrete/brick walls, partitions, office furniture and other items affect as additional absorption term to the path loss.

Performance of reinforced concrete frames using force and displacement based seismic assessment methods

This paper reviews the traditional force-based (FB) seismic design method and the newly proposed displacement-based (DB) seismic assessment approach. A case study is presented for reinforced concrete (RC) moment-resisting frames designed and detailed according to European and Australian earthquake code provisions, having low, medium and high ductility capacity. The aim is to assess the performance characteristics of these frames, using the well known El Centro NS earthquake ground motion as the seismic input. Overall ductility demands have been computed for the force-based analyses conducted on the typical design frames. In the second part of the paper, the performance of the case study frames has been re-evaluated in the light of displacement-based principles. A recently proposed method for displacement-based seismic assessment of existing RC frame structures has been implemented for this purpose, from which it has been concluded that the displacement-based approach predicts very similar overall displacement demands for such frames. These results, whilst limited to the consideration of a small number of seismic frame structures and a single, typical strong earthquake ground motion, nevertheless give confidence that the displacement-based approach can rapidly and easily facilitate a seismic assessment of an existing RC structure, without the necessity to undertake detailed inelastic dynamic analyses.

Role of chemical and mechanical stimuli in mediating bone fracture healing.

1. Bone is a remarkable living tissue that provides a framework for animal body support and motion. However, under excessive loads and deformations, bone is prone is to damage through fracture. Furthermore, once the bone is weakened by osteoporosis, bone fracture can occur even after only minimal trauma.