Investigation of hybridized polyurethane, glass fibre reinforced cement and steel laminate in structural floor plate systems

Sandwich components have emerged as light weight, efficient, economical, recyclable and reusable building systems which provide an alternative to both stiffened steel and reinforced concrete. These components are made of composite materials in which two metal face plates or Glassfibre Reinforced Cement (GRC) layers are bonded and form a sandwich with light weight compact polyurethane (PU) elastomer core. Existing examples of product applications are light weight sandwich panels for walls and roofs, Sandwich Plate System (SPS) for stadia, arena terraces, naval construction and bridges and Domeshell structures for dome type structures. Limited research has been conducted to investigate performance characteristics and applicability of sandwich or hybrid materials as structural flooring systems. Performance characteristics of Hybrid Floor Plate Systems comprising GRC, PU and Steel have not been adequately investigated and quantified. Therefore there is very little knowledge and design guidance for their application in commercial and residential buildings. This research investigates performance characteristics steel, PU and GRC in Hybrid Floor Plate Systems (HFPS) and develops a new floor system with appropriate design guide lines

Dynamic Behaviour of Flat Post-Tensioned Floor Plates

Vibration is a serviceability limit state for the design of suspended floor systems in buildings that is not well understood by many structural engineers. Dynamic behaviour is an important design consideration for slender, two-way floors, particularly for those of post-tensioned concrete construction. At present, there are no reliable design guidelines that deal with this problem. This paper describes a research program on the dynamic behaviour of posttensioned concrete floors that is presently underway at Queensland University of Technology in Brisbane, Australia. Results from this research will enable the development of much needed design guidance on the dynamic behaviour post-tensioned concrete floors in buildings. A full-scale, post-tensioned slab specimen has been constructed in the university’s structural laboratory. Purpose-designed support brackets have been fabricated which have enabled an investigation on the effects of various support conditions at the corners of the specimen. A series of static and dynamic tests are being performed in the laboratory to obtain basic material properties and behavior of the specimen. Data collected from these experiments will be used to tune finite element models for computational, parametric studies. Preliminary finite element analyses of both composite and homogeneous material cross-sections have been calibrated against results from initial laboratory experiments. Further field instrumentation and testing of floors in existing buildings will be conducted to validate computational studies. These computational studies will be expanded to generate predictive guidelines for the free vibration and response of two-way, post-tensioned concrete floors

Review: Acoustic emission technique - Opportunities, challenges and current work at QUT

Acoustic emission (AE) is the phenomenon where high frequency stress waves are generated by rapid release of energy within a material by sources such as crack initiation or growth. AE technique involves recording these stress waves by means of sensors placed on the surface and subsequent analysis of the recorded signals to gather information such as the nature and location of the source. AE is one of the several non-destructive testing (NDT) techniques currently used for structural health monitoring (SHM) of civil, mechanical and aerospace structures. Some of its advantages include ability to provide continuous in-situ monitoring and high sensitivity to crack activity. Despite these advantages, several challenges still exist in successful application of AE monitoring. Accurate localization of AE sources, discrimination between genuine AE sources and spurious noise sources and damage quantification for severity assessment are some of the important issues in AE testing and will be discussed in this paper. Various data analysis and processing approaches will be applied to manage those issues

Classification of railway bridges based on criticality and vulnerability factors

Bridges are currently rated individually for maintenance and repair action according to the structural conditions of their elements. Dealing with thousands of bridges and the many factors that cause deterioration, makes this rating process extremely complicated. The current simplified but practical methods are not accurate enough. On the other hand, the sophisticated, more accurate methods are only used for a single or particular bridge type. It is therefore necessary to develop a practical and accurate rating system for a network of bridges. The first most important step in achieving this aim is to classify bridges based on the differences in nature and the unique characteristics of the critical factors and the relationship between them, for a network of bridges. Critical factors and vulnerable elements will be identified and placed in different categories. This classification method will be used to develop a new practical rating method for a network of railway bridges based on criticality and vulnerability analysis. This rating system will be more accurate and economical as well as improve the safety and serviceability of railway bridges

Synthetic rating system for railway bridge management

Railway bridges deteriorate with age. Factors such as environmental effects on different materials of a bridge, variation of loads, fatigue, etc will reduce the remaining life of bridges. Bridges are currently rated individually for maintenance and repair actions according to the structural conditions of their elements. Dealing with thousands of bridges and several factors that cause deterioration, makes the rating process extremely complicated. Current simplified but practical rating methods are not based on an accurate structural condition assessment system. On the other hand, the sophisticated but more accurate methods are only used for a single bridge or particular types of bridges. It is therefore necessary to develop a practical and accurate system which will be capable of rating a network of railway bridges. This paper introduces a new method for rating a network of bridges based on their current and future structural conditions. The method identifies typical bridges representing a group of railway bridges. The most crucial agents will be determined and categorized to criticality and vulnerability factors. Classification based on structural configuration, loading, and critical deterioration factors will be conducted. Finally a rating method for a network of railway bridges that takes into account the effects of damaged structural components due to variations in loading and environmental conditions on the integrity of the whole structure will be proposed. The outcome of this research is expected to significantly improve the rating methods for railway bridges by considering the unique characteristics of different factors and incorporating the correlation between them

Frequency Response of Flat Post-tensioned Concrete Floors: Frequency Coefficient-Root Function Method

Vibration is a serviceability limit-state for the design of suspended floor systems in buildings that is not well understood by many structural engineers, and is often ignored. Dynamic response is an important design consideration for slender, two-way floors, particularly for those of post-tensioned concrete construction. At present, there are no reliable design guidelines that deal with this problem. This paper describes a research program, which will enable the development of much needed design guidance on the dynamic behavior of suspended post-tensioned concrete floors. Results from this parametric investigation have led to the preliminary development of new approach for predicting the natural frequency of flat, post-tensioned concrete floor structures. This new method has been named, the Frequency Coefficient-Root Function (FCRF) method. The FCRF method is a revolutionary and convenient tool structural engineers can use to design for the vibration serviceability limit-state of cast-insitu, post-tensioned concrete floor systems

Damage quantification techniques in acoustic emission monitoring

Acoustic emission (AE) analysis is one of the several diagnostic techniques available nowadays for structural health monitoring (SHM) of engineering structures. Some of its advantages over other techniques include high sensitivity to crack growth and capability of monitoring a structure in real time. The phenomenon of rapid release of energy within a material by crack initiation or growth in form of stress waves is known as acoustic emission (AE). In AE technique, these stress waves are recorded by means of suitable sensors placed on the surface of a structure. Recorded signals are subsequently analysed to gather information about the nature of the source. By enabling early detection of crack growth, AE technique helps in planning timely retrofitting or other maintenance jobs or even replacement of the structure if required. In spite of being a promising tool, some challenges do still exist behind the successful application of AE technique. Large amount of data is generated during AE testing, hence effective data analysis is necessary, especially for long term monitoring uses. Appropriate analysis of AE data for quantification of damage level is an area that has received considerable attention. Various approaches available for damage quantification for severity assessment are discussed in this paper, with special focus on civil infrastructure such as bridges. One method called improved b-value analysis is used to analyse data collected from laboratory testing

AFRP retrofit of reinforced concrete columns against impact loading

Structures can be exposed to impact loads as a result of an explosion, falling objects, projectiles and vehicle collisions. Within the increasing threat of these impact sources, it is very important to protect the columns that are the vital members of the structural systems to ensure structural and personal safety. This study focuses on the performance of axially loaded reinforced concrete members subjected to impact loading. A dropped-weight test set-up developed to perform impact tests on reinforced concrete members. The test set-up was used to perform low elevation impact tests on reinforced concrete (RC) columns that targets to simulate vehicular impact against ground floor columns of low-rise buildings. Since, there is limited information about the transverse impact performances of RC columns; the main objective of this research is to assess the vulnerability of RC columns under transverse impact loads and to enhance their performances by using Aramid Fiber Reinforced Polymer (AFRP) sheets. The scope is limited to 300 mm square columns with 3 m height in low to medium rise buildings which were found to be more vulnerable to lateral impacts according to previous research conducted by the authors, (Gurbuz et al. 2010, 2011). This research provides fundamental knowledge on the behavior of RC columns under low elevation impact loading and also generates new information on impact strengthening of vulnerable concrete columns by AFRP sheets

Development of a cost-effective and flexible vibration DAQ system for long-term continuous structural health monitoring

In the structural health monitoring (SHM) field, long-term continuous vibration-based monitoring is becoming increasingly popular as this could keep track of the health status of structures during their service lives. However, implementing such a system is not always feasible due to on-going conflicts between budget constraints and the need of sophisticated systems to monitor real-world structures under their demanding in-service conditions. To address this problem, this paper presents a comprehensive development of a cost-effective and flexible vibration DAQ system for long-term continuous SHM of a newly constructed institutional complex with a special focus on the main building. First, selections of sensor type and sensor positions are scrutinized to overcome adversities such as low-frequency and low-level vibration measurements. In order to economically tackle the sparse measurement problem, a cost-optimized Ethernet-based peripheral DAQ model is first adopted to form the system skeleton. A combination of a high-resolution timing coordination method based on the TCP/IP command communication medium and a periodic system resynchronization strategy is then proposed to synchronize data from multiple distributed DAQ units. The results of both experimental evaluations and experimental-numerical verifications show that the proposed DAQ system in general and the data synchronization solution in particular work well and they can provide a promising cost-effective and flexible alternative for use in real-world SHM projects. Finally, the paper demonstrates simple but effective ways to make use of the developed monitoring system for long-term continuous structural health evaluation as well as to use the instrumented building herein as a multi-purpose benchmark structure for studying not only practical SHM problems but also synchronization related issues

Seismic design of masonry-infilled frames: A review of codified approaches

This paper reviews the approach of eleven national codes on the analysis and design of masonry-infilled frames. It is shown that, in general, codes can be divided into two groups. The first group isolates the masonry and frame members by providing gaps to minimize the interaction between them. This method ensures that the complexities involved in analyzing the structure is avoided. However, the width of the gaps recommended is different for each of the codes. The second group takes advantage of the presence of high stiffness and strength masonry infill. In this technique, an equivalent-strut modeling strategy is mostly recommended. It is shown that the strut model suggested in each of the codes is different. An attempt to obtain a generic model for masonry-infilled frame failed largely due to the existence of many behavior-influencing parameters. Finally, it is suggested to have a paradigm shift in the modeling strategy where the masonry-infilled frames are classified into different categories and a model is suggested for each of them