Proceedings

Abstract: This paper investigates the influence of longitudinal CFRP straps on the behaviour of circularised and FRP wrapped square hollow reinforced concrete (RC) columns. Twelve square hollow RC specimens were prepared and tested under concentric axial loads, eccentric axial loads and four-point bending. The specimens were divided into three groups of four specimens. The specimens in the first group were the non-strengthened square hollow RC specimens. The specimens in the second group were circularised by adding concrete segments to the sides of the square hollow RC specimens. Then the circularised specimens were wrapped with two layers of CFRP. The specimens in the third group were strengthened by attaching one longitudinal CFRP strap on each side of the square hollow RC specimens. Then the specimens were circularised with concrete segments and wrapped with two layers of CFRP. The test results showed that circularisation of the square hollow RC specimens enhanced the performance of the specimens in terms of ultimate axial load and ductility. The influence of the longitudinal CFRP straps was insignificant in increasing the ultimate axial load and ductility of concentrically loaded specimens. The presence of the longitudinal CFRP straps enhanced the axial load at yield of concentrically loaded specimens. The presence of the longitudinal CFRP straps enhanced the ultimate axial load and ductility of eccentrically loaded specimens. The contribution of the longitudinal CFRP straps to the ultimate axial load and ductility of the circularised square hollow RC specimens increased with the increase in load eccentricity. Also, the longitudinal CFRP straps increased the bending moment capacity of the circularised and CFRP wrapped square hollow RC specimens.

Abstract: Steel reinforced concrete (SRC) structures have been widely applied in civil engineering. High speed railway is quickly developed all over China in recent years. SRC beams are often used in bridges as well as in floors of buildings for high speed railway stations. Fatigue design is essential for a structure subjected to high-cycle fatigue loading. The fatigue behaviour of steel beams, reinforced concrete beams and steel-concrete composite beams has been investigated quite well and relevant fatigue design specifications have come into use (Eurocode 2, 2005; Eurocode 3, 2005). However, fatigue of SRC beams is a new research topic. Tong et al (2012; 2013) carried out fatigue tests on SRC beams and their connections in order to meet needs of fatigue design of the engineering project for Shanghai Hongqiao Railway Station. A fundamental study on fatigue behaviour of SRC beams are reported in this paper. Both the experimental and numerical simulation results are presented.

Abstract: Structural strength, stiffness, and stability are three of the most important factors which should be considered for assessing structural designs. Therefore, in order to achieve safe and practical designs, structural stability must be taken into account during a structural optimization procedure. Buckling optimization has drawn more research attention in recent years.
Some issues in the topology optimization of continuum structures considering structural stability are investigated. The optimization problem of compliance minimization under constraints on material volume and buckling load factors is considered. The Solid Isotropic Material with Penalization (SIMP) material model is used for topology optimization and a hybrid stress element is employed in structural analysis.
An adaptive continuation method is proposed, in which the penalty parameter in the SIMP model is automatically adjusted during the optimization procedure according developed rules. Using these rules, buckling constraints would be properly considered throughout the optimization to guide optimized designs to move in more appropriate directions.
Numerical examples will be presented to demonstrate the effectiveness of the proposed method and future applications of the method discussed.

Abstract: Concrete-filled double skin steel tubular (CFDST) member consists of inner and outer steel tubes with concrete in-filled in the sandwiched cavity. It inherits advantages of the common concrete-filled steel tube, such as high resistance, high stiffness and good constructability. It also has some other characteristics, such as lighter self-weight and better fire performance. It is found that the inner tube can provide a sufficient support to the sandwiched concrete, and the steel-concrete-steel interfaces can work together effectively under various loading conditions. The concrete-filled double skin steel tubes may provide a better design option when designing members of large cross-sectional profile. Therefore they have been used in some engineering projects in China.

Abstract: Fibre-reinforced polymer (FRP) composite materials can be applied to existing reinforced concrete (RC) structures for a variety of reasons ranging from strengthening and retrofitting to rehabilitation and repair. Experimental and numerical investigations over the last two decades and more have demonstrated the effectiveness of the FRP intervention. By far and large the most commonly investigated scenarios include the flexural and shear strengthening of flexural members such as beams, as well as the confinement of compression members such as columns. As a result of such research advances and understanding, design guidelines have been steadily appearing throughout the world since the middle to late 1990s. Leading design guidelines are now available in their second or third versions (e.g. ACI 440.2R-17, Concrete Society 2012) and some countries are at the stage of developing and publishing standards.

Abstract: This study examines the consequences of the different analysis approaches traditionally followed by designers in consulting offices during the design process of high-rise buildings utilizing thick transfer slabs between their tower and podium floors. Emphasis is placed on the importance of accounting for the interaction between the transfer plate slabs and the building structural elements during the analysis process. The effect of the transfer slab span to thickness ratio on the structural behaviour of such buildings is investigated. It was concluded that interaction between the transfer slabs and building vertical structural elements can significantly affect the straining actions calculated within these elements and consequently this effect should be accounted for during analysing these structures. Also, it was shown that the transfer slab should be accurately modelled during developing the building structural numerical model to simulate the real structural behaviour for such type of building.

Abstract: This research proposes to combine recycled aggregate concrete (RAC) with steel fibres (SF), to provide an environment-friendly, sustainable, and structurally sound alternative to natural aggregate concrete (NAC). When steel fibre reinforced recycled aggregate concrete (SFRRAC) is used in construction, the existing design equations and associated safety factors need to be revised; the existing design provisions are applicable only to NAC and cannot be applied to SFRRAC directly. In this research, safety factors of design equations for beams provided in the current Australian, American, and European design codes are calibrated based on the first-order reliability method (FORM) when used for the structural design of SFRRAC beams. This is carried out based on a proposed prediction model for the flexural capacity of SFRRAC, which considers the contribution of SF unlike the conventional prediction model for RC beams. The uncertainty of the prediction model is estimated based on nine experimental results of secondary SFRRAC beams tested for flexural failure under three-point bending. These beams are fabricated with varying contents of recycled aggregate and steel fibre ratios. Furthermore, the reliability index ratios of the different SFRRAC mixes considered are estimated.

Abstract: This paper reports the results of an experimental investigation on the behaviour of square High Strength Concrete (HSC) columns reinforced longitudinally with either steel bars or Steel Equal Angle (SEA) sections under concentric axial compression. The use of SEA sections as longitudinal reinforcement may enhance the load carrying capacity and ductility of concrete columns. These enhancements are because for a given cross-sectional area, a SEA section has a higher second moment of area and radius gyration than a steel bar. Also, the SEA sections provide a greater confinement area for the concrete core of columns. A total of 6 column specimens with a square cross section of 210 mm and 600 mm height were tested under concentric axial compression. The specimens were divided into two groups and each group contains three specimens. The specimens in the first group (Group 1) were reinforced longitudinally with four N12 (12 mm diameter) deformed steel bars and served as reference specimens. The remaining four specimens in the second group (Group 2) were reinforced longitudinally with four A30 (29.1 mm x 29.1 mm x 2.25 mm) SEA sections. The lateral reinforcement spacing in each group of specimens varied between 50 mm and 200 mm. The influence of the type of longitudinal reinforcement (steel bars and SEA sections) and the spacing of the lateral reinforcement on the performance of the column specimens were investigated and discussed. The results of this investigation showed that for specimens reinforced with SEA sections, the ductility significantly enhanced compared to corresponding specimens reinforced with steel bars. The test results also indicated that as the lateral reinforcement increased from 50 mm to 200 mm, specimens reinforced with SEA sections showed better enhancement in ductility and strength than the specimens reinforced with steel bars.

Abstract: This paper presents the behaviour of square high-strength concrete (HSC) specimens reinforced longitudinally with steel equal angle (SEA) sections under different loading conditions. For the same cross-sectional area, a SEA section has a higher second moment of area than a steel bar, which results in a greater bending stiffness of the concrete member reinforced with SEA sections. Also, the area of confined concrete is greater in concrete members reinforced with SEA sections compared to members reinforced with steel bars, which results in higher strength and ductility. A total of 8 specimens of 210 mm square cross-section and 800 mm height were constructed and tested. The specimens were divided into two groups with four specimens in each group. Group R-S50 specimens serve as the reference group and were reinforced longitudinally with four N12 (12 mm diameter) deformed steel bars. Group A30-S50 specimens were reinforced longitudinally with four A30 (29.1 mm x 29.1 mm x 2.25 mm) SEA sections. All specimens were reinforced laterally with R10 (10 mm diameter) plain steel bars and spaced at 50 mm centres. The main variables considered in the study included the type of longitudinal reinforcement and the magnitude of load eccentricity. It was obtained from the experimental results that specimens reinforced longitudinally with SEA sections showed greater ductility compared to specimens reinforced longitudinally with steel bars under different loading conditions.

Abstract: Packing density method is new kind of mix design method, generally used for design normal, high-strength and self-compacting concrete. This method considers the volume and density variation between different types and sizes of aggregate. The adoption of packing density method optimises the particle packing density of concrete by selecting the right amount of various aggregates to fill up the voids between large and small aggregates, which allows a more dense and stiff structure. This paper is devoted to the studies of material and mechanical properties of recycled aggregate concrete using packing density method. This paper considers mix of two different aggregate sizes of 10 and 20mm, 0, 30, 50, 70 and 100% recycled aggregate replacement ratios, and water-cement ratio of 0.35, 0.45 and 0.55. In total of fifteen concrete mix designs are considered. The paper presents the material properties of aggregates which were obtained from the material testing. The mix design method and results of mechanical testing will be discussed. The results show that the packing densities of natural and recycled aggregates are different, and should not be treated in the same way. By using packing density mix design method, recycled aggregated concrete strengths fluctuation can be resolved, and the concretes can have similar strengths consistency, regardless the recycled concrete aggregate replacement ratios. This method minimise the influence of recycled concrete aggregates obtain from various sources with variable quality.

Abstract: Different materials and structures are designed for a certain service life. However, integrity and durability of materials particularly, newly-developed or waste materials used in construction to make them environmentally friendly, can affect the performance of structures and the design life. This integrity could be in the materials from the beginning like porous recycled aggregates that may cause pops out in concrete. It also could happen during the service life due to different reasons such as exposure to aggressive environments or fire. Loss of integrity of the anode metal used in cathodic protection of concrete structures is an example of the later mentioned issue. Detecting the mechanism of defect of construction materials used, not only assists to improve the development of better future construction materials, but also assists with the repair of the defects. Microstructural analysis of samples is an effective method to assess the integrity of materials. It is used to determine practical solutions for the repair and remediation. This paper reveals the importance of use of microstructural analysis to evaluate materials used in structures through explanation of examples of the application of scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) analysis methods and X-ray mapping (XRM) utilised in diagnosis of the construction materials in service.

Abstract: Beam-column joints are critical regions in reinforced concrete structures which require proper design approach to lead to ductile behaviour instead of a brittle one and increase resilience and energy absorption capacity of structures particularly during earthquakes. For this purpose, the amount of steel reinforcement in this region has usually high density, particularly the number of stirrups as transverse reinforcement are increased to provide the desired ductility required by different design codes. However, the use of large amounts of reinforcement is associated with difficulties regarding concrete pouring and vibration of fresh concrete. The lack of full concrete penetration into the joint region causes porosity and formation of voids and honey comb in concrete at this critical region. To address this problem extensive studies have been conducted to evaluate and improve structural performance of beam-column connections. This paper is part of an ongoing research in this area through experimental testing of a novel concrete in beam-column joint specimens and a conventional concrete for comparison. To evaluate the behaviour of these beam-column joints, failure mode, crack at the failure, load-deflection behaviour and ultimate load capacity of the subassemblies were investigated according to the data obtained from the experiments. The novel concrete tested in this research showed better performance in terms of failure mode, crack propagation and ultimate load capacity.

Abstract: Despite proven to exhibit excellent mechanical properties, fresh geopolymer paste is highly viscous and displays low workability, which has become a major obstacle for it to be widely accepted for larger structural application. For cast-in-place applications, geopolymer concrete requires to be cured at ambient temperatures. Temperature and humidity varies in different seasons. The humidity variation has been found to have influence on the occurrence of white efflorescence on geopolymer samples. However, effects of temperature on efflorescence have received little attention, although temperature effects on strength are well-known. This paper will investigate the effect of a change in seasonal temperature on the properties of geopolymer mortars. The investigated properties include workability, compressive strength and efflorescence. Mini slump tests method will be carried out to determine the effect of adding extra water and commercially available superplasticisers (SP) on the flowability of geopolymer mortar. From the obtained test results, it was found that SIKA Visco Crete PC HRF – 2 has achieved the highest relative slump as compared to the reference mix RM8. Regarding strength development, it was observed those samples cured in hot (summer) conditions are more desirable to cure geopolymer mortar. Also, specimens cured under lower temperature curing conditions and low in humidity had formed white efflorescence after 7 days curing period, and rapid growth was observed over the period of 28 days curing cycle.

Abstract: Geopolymeric binders exhibit high thermal stability and consequently it is believed that these materials can be extensively used in the construction of infrastructure, where fire safety is of major concern. For such applications, thermal properties play a fundamental role in the heat transfer calculation. This paper aims to provide a comprehensive experimental study of thermal properties of various geopolymeric binders at elevated temperatures. The binders were prepared using alkali-activated low calcium fly ash/ground granulated blast-furnace slag at ratios of 100/0, 50/50, 10/90 and 0/100 wt%. A transient plane source measurement technique was applied to assess the heat capacity and thermal conductivity at temperatures ranging from 23–600 oC. Data generated was utilised to develop analytical expressions for estimating thermal properties as a function of temperature. The simplified relationships can be used for estimating the fire resistance of structural elements made with geopolymeric materials.

Abstract: Concrete exhibits excellent compression strength and durability properties; however, it is weaker in shear. The shear resistance of concrete is largely influenced by the strength of the interfacial zone between the aggregates and the mortar. To enhance the density and strength of the interfacial zone of the concrete, silica fumes have been mixed with the mortar and aggregates. This investigation focuses on the effect of multi-walled carbon nano-tubes (MWCNTs) and graphite nano-fibres (GNFs) on the shear strength of concrete. Since these nano-materials are small in size and possesses large surface areas and strong van der Waals interaction forces, it is expected that they can bridge the zone between the mortar and aggregate interface, thus limiting the formation and growth of micro-cracks. However, nano-materials tend to bundle up and form entangled clumps due to their strong van der Waals interaction forces. For this reason, the nano-materials were dispersed using gum arabic (GA). Two series were investigated; one incorporating GA and MWCNTs, and the other one incorporating GA and GNFs. In both series GA equivalent to 1% of the water was mixed with water and nano-materials (MWCNTs or GNFs) equivalent to 1% of the cement weight were mixed with the cement powder and subsequently mixed with the aggregates.

Abstract: Construction projects use up large quantities of natural resources and produce tonnes of construction and demolition waste (CDW). Because of its growth, these quantities have increased in the last few years and it has now become necessary to create a sustainable method of development in civil construction. Therefore, recycling and utilization of recycled materials in construction projects can be the most promising solution for this problem. Due to important role and high portion of aggregates in asphalt concrete, utilization of recycled materials including recycled construction aggregates (RCA) can provide enormous benefits from the viewpoint of environmental sustainability and effective use of resources. In spite of the awareness of the importance of using RCA and much research being conducted, there is still a need for a deeper study about the characteristics of the RCA. The variability in behaviour and performance of RCA used in construction projects indicates the variability in their composition. This paper presents the results of a statistical study, image analysis and experimental study to evaluate the characteristics of RCA as an alternative for virgin aggregate in asphalt mixture. A series of characterization tests were conducted three times, using RCA collected at different dates.

Abstract: Known for their structural efficiency, sandwich panels have evolved with advances in materials science. These panels are now used extensively in many fields including the construction industry to take advantage of their light weight and ease of construction. Metals and timber-based products, especially oriented strand board, have continued to be the facing materials of choice. However, plastic, polymer and concrete or other cementitious facings reinforced with glass, steel, carbon, natural fibres or textiles are finding increasing use. Core materials now include balsa and other types of wood, expanded polystyrene (EPS), rigid foams, and foamed or lightweight cements and concretes. Some cores incorporate various lattice, truss or pyramid-type structures while others have honeycombs. Such assemblies are fabricated using materials ranging from paper to aluminium and steel. The current review surveys structural sandwich panels with non-profiled faces and a range of innovative core composites and configurations. Specifically, it examines the properties that make them particularly suitable for their respective applications as well as any inherent weaknesses or peculiarities that require due consideration in design. Structural response under bending and compression, and typical failure modes are also considered.

Abstract: This paper aims to study the behaviour of axially loaded innovative cold-formed steel (CFS) built-up stub columns. Four innovative CFS built up sections is presented in this paper. Each section is composed of combination of more than two elements as follows: channels, channels with lip, Sigma section and /or plates. The elements of each section are assembled together by using self tapping screws. The axial load capacity of each of the four sections was investigated numerically by using finite element (FE) model using ABAQUS program. The FE model was verified against previous test data. The FE model was used to study different parameters that affect the load capacities of the innovative CFS built-up stub columns, these parameters are: columns profile, steel thickness, steel grade and longitudinal spacing between screws (fasteners), cross sectional area.

Abstract: Materials such as timber, concrete and steel have been utilised in the fabrication of transoms in railway bridges worldwide. Timber transoms are commonly used in Australia’s railway network but frequently require maintenance and replacement due to the degradation of the timber. Therefore, they are not favourable for use in today’s railway systems. To be a viable option for replacement, proposed transoms should provide practical, financial and structural benefits. This research outlines the structural benefits of composite steel-concrete transoms for ballastless tracks on the Sydney Harbour Bridge. The paper herein considers both reinforced concrete and prestressed concrete and simulates the derailment impact loading of a train through dynamic experimental testing. The paper also evaluates the potential use of 3 different shear connectors; welded shear studs, Lindapter bolts and Ajax bolts. The results of the experimental tests are used to determine whether each transom is a viable option for the replacement of the current timber transoms on the Sydney Harbour Bridge and whether they provide a stronger and longer lasting solution to the current transom problem.

Abstract: The Sydney Harbour Bridge requires the replacement of the timber transoms that currently reside in the railway system. Composite steel and precast reinforced concrete transoms have been proposed as the replacement for the current timber counterparts. In existing studies, it is found that there is little investigation into the effect of derailment loading on reinforced concrete transoms. This paper provides a continuation on a previous study of static loading on reinforced concrete transoms and investigates the failure behaviour through means of finite element analysis. The FEA commercial software known as ABAQUS was used to investigate the effect of static loading on the composite concrete transoms. The FE data accuracy was verified by comparing the existing experimental results. The experimental study and numerical investigation, transoms using AJAX bolts was shown to perform better than the welded headed shear studs. Additionally, the FE models produced in this study were validated by the results of the experimental study; however, further investigation into the damage properties is required before proper evaluation of the failure behaviour is determined.

Abstract: Circular hollow sections (CHS) are widely used in most types of structures such as bridges, communication towers and offshore platforms that are subjected to different types of loading. The main girder for truss arch bridges and cabled stayed bridges can be made of CHS and concrete-filled circular hollow sections (CFCHSs) in large span bridges. Extensive experimental determinations of stress concentration factors (SCFs) on empty tube to tube T-joints have been previously investigated. These investigations resulted in the development of design guidelines for fatigue of CHS uniplanar T-joints such as CIDECT Design Guide No. 8. On the other hand, little research has been carried out on the determination of the SCFs of T-joints with concrete-filled chords. As a result, there is no design guide for T-joints with concrete-filled chords. An experimental investigation was performed at Western Sydney University (WSU), Kingswood Campus. The strain gauging process was used to install strip and single strain gauges onto two T-joint specimens with concrete-filled chords for the measurement of strains. The strain gauging enabled the measurement of strains in concrete-filled T-joints and determined the SCFs of two concrete-filled T-joints specimens under axial tension, axial compression and in-plane bending. The stress distributions around the weld joints for empty T-joints have been previously researched. Calculations of the SCFs for these empty T-joints under axial load and in-plane bending can be determined based on the CIDECT Design Guide No.8. The calculated SCFs values for empty joints are compared to the SCFs of the concrete-filled chord T-joints obtained from the results of the experiment. The purpose of this comparison is to find out if it is beneficial to use concrete- filled T-joints for fatigue design.

Abstract: The purpose of this study is to identify structurally efficient and practical post-installed shear connectors for composite structures designed with a focus on sustainability. According to the Australian 2010 Infrastructure Report Card, a large number of Australian infrastructures are reaching the end of their design life. Therefore, there is a need for repair and strengthening of deteriorated, damaged and substandard infrastructures. The use of post-installed shear connectors to develop composite action in lieu of conventional headed shear studs and in strengthening and retrofitting of existing composite structures can be a structurally efficient and cost-effective approach. While composite beams that are retrofitted with post-installed shear connectors are potentially sustainable and recyclable elements, research contributions on these types of beams are very limited. In this paper a three-dimensional finite element model is developed to investigate the structural performance of a steel–concrete composite beam with post installed shear connectors and the factors that influence static strength of these types of connectors. The accuracy of the 3-D finite element model proposed in this work is validated by comparison with available experimental results.

Abstract: This paper studies the vibration properties of circular concrete-filled steel tubular (CFST) beams and their potential applications in determining the flexural stiffness of CFST and detecting steel-concrete interface debonding. A total of 8 specimens, 4 intact ones and 4 with circumferential debonding, were tested with impact hammer excitation. The frequency response function (FRF) curves of the specimens were calculated and the first few modes of natural frequencies and mode shapes of the specimens were extracted. Numerical model was established to predict the natural frequencies of the intact CFST beams. By comparing the predicted and extracted natural frequencies, the flexural stiffness of the beam was calibrated. It shows that employing the gross flexural stiffness in the numerical model could predict the natural frequencies of CFST with good accuracy. The major characteristics of debonded CFST vibration was also summarized, including the presence of extra modes and the reduction of natural frequencies of flexural modes. Such characteristics could be used as indicators of steel-concrete interface debonding in CFST structures.

Abstract: In the last few decades, different studies have been conducted to develop high-performance fibre reinforced cementitious composites (HPFRCCs) exhibiting very high tensile strain. This type of material is designed based on micromechanics principles and is different from conventional concrete as it contains only very fine sand, usually silica sand with maximum aggregate size about 250µm. However, other types and sizes of aggregates have been successfully used to produce HPFRCCs. This study aims to develop ECC, which is a class of HPFRCCs, produced with a replacement of silica sand with dune sand at 0, 50 and 100% by weight. The presence of dune sand was seen to improve the strength of ECC by up to 50% at both early and later ages. The tensile strain at early age also was seen to improve in comparison to the control mix.

Abstract: Recent academic research has focused on the need to develop an environmentally sustainable substitute for conventional Ordinary Portland Cement (OPC) based concrete. The need to develop such substitute stems from the global effort to reduce the consumption of natural resources and minimize carbon dioxide emissions. In this regard, the utilisation of Fly Ash (FA) based Geopolymer Concrete (GPC) within global construction applications can significantly reduce pollution and landfill issues associated with cement production and FA burial, respectively. However, essential additives such as Granulated Blast Furnace Slag (GBFS) and Superplasticizers (SPs) are required to achieve effective ambient temperature curing. Without effective curing within ambient temperature conditions, GPC behaves poorly with respect to important factors such as, strength development and workability Bakharev (2005). Consequently, this paper presents and discusses the methodology and results for both the fabrication and testing stages of eight push test specimens which incorporate GPC. A total of four specimens consist of standard Solid Slab (SS1, SS2, SS3, SS4) push tests and the remaining four specimens (B1, B2, B3, B4) consist of identical Solid Slab specimen dimensions with the additional implementation of Bondek (Profiled-Steel-Sheeting). Specimen SS1 outperformed all other Solid Slab (SS2, SS3) specimens which incorporated GPC in terms of maximum shear resistance capacity (MSRC) by achieving a value of 927kN, additionally, Bondek specimen B2 achieved a MSRC of 393.04kN, thus proving that outdoor temperature curing is superior than indoor temperature curing conditions and that the implementation of up to 30% recycled coarse aggregate (RCA) does not negatively impact the performance or durability of concrete with respect to 100% Natural Coarse Aggregate (NCA), respectively. Furthermore, the comparison of specimens SS1 and B2 to the control OPC based specimens, SS4 and B4 proves that GPC is capable of effectively replicating characteristics such as strength and durability of conventional OPC based concrete.

Abstract: This study explores the effect of length to diameter (L/D) ratio on the axial load capacity of self-compacting concrete-filled small diameter steel tube (SCFT) specimens. The SCFT specimens with L/D ratio of 2, 4, 6, 8, 10, 12 and 14 were tested. Two different cold-formed steel tubes were used in the construction of the SCFT specimens. For each L/D ratio, two specimens were tested. For tension tests, three specimens were tested for each type of unfilled steel tube. A total of 62 steel tube specimens were tested which included 6 specimens under axial tension and 56 specimens under axial compression. The experimental results of the SCFT specimens were compared with the estimates from three design standards: American Standard, Canadian Standard and European Standard (Eurocode 4). It was found that Eurocode 4 provided the best estimate, whereas American Standard provided the most conservative estimate. Also, when the L/D ratio of SCFT specimens increased from 2 to 8, the parameter related to the effect of confinement concrete (η_c) which is calculated from Eurocode 4 decreased. Therefore, the decrease in η_c resulted in a decrease in the concrete enhancement factor. For SCFT specimens with L/D ratio ≥ 10 the parameter η_c was negligible and resulted in the concrete enhancement factor =1.

Abstract: Long-term durability is the main concern in the area of civil engineering due to safety considerations. This paper reports the strength and ductility behaviour of steel plate reinforced concrete beams under four-point bending. A total of three full-scale beams of 200 mm width, 300 mm height and 4000 mm length were cast and tested. All the beams had the same details of stirrups and compression reinforcement. The first beam was reinforced with ordinary reinforcement (2 deformed steel bars with a nominal diameter of 20 mm) and served as a reference beam. The second beam was reinforced with a chequer steel plate and provided with 20 steel bolts welded to the chequer steel plate at a regular distance of 200 mm centre to centre. The third beam was reinforced with a chequer steel plate and provided with 4 steel angles welded at the ends of the steel plate. Each plate reinforced concrete beam was designed to have an equivalent force to the ordinary reinforced concrete beam. The strengths, ductilities and analytical considerations of the beams are covered in this paper. The results showed no significant difference (less than 2%) between the strengths of ordinary and plate reinforced concrete beams. On the other hand, the steel plates significantly increased the ductility. The ductilities of plate reinforced concrete beams provided with steel bolts and angles increased by up to 3.7 and 2.3 times, respectively compared with the ordinary reinforced concrete beam. It was also observed, that the use of steel bolts in the plate reinforced concrete beam, improved the ductility by 43.2% compared to the steel angles.

Abstract: The problem of cracked concrete structures is receiving considerable attention in the construction industry worldwide. Externally bonded steel plates are used to repair cracked reinforced concrete structures in a number of projects in various parts of the World, but their overall performance is still not fully understood. This investigation assesses the strength and deflections of 12 full-scale reinforced concrete (RC) beams of 175 mm wide x 300 mm deep x 3200 mm long that were pre-cracked, repaired with steel plate at its soffit, using strong epoxy glue and after that, tested to failure under a four-point loading. The beams were divided into three groups. Group 1 comprised of two control beams, which were tested until failure, and were not repaired with steel plates. Group 2 consisted of five beams which were pre-cracked up to the serviceability capacity of the control beams, and Group 3 consisted of five beams which were pre-cracked up to 85% of the capacity of the control beams. All the pre-cracked beams were repaired with steel plates of 6 mm thickness and widths which varied from 75 mm up to 175 mm, in increments of 25 mm. The structural behaviour of all the beams is reported in terms of flexural strength, stiffness, maximum deflections and failure modes. Finally, experimental results are compared with code-predicted results calculated using the EN 1992-1-1 (2004). Externally bonding the steel plate to the pre-cracked reinforced concrete beams resulted in increased stiffness and maximum load capacities and decreased in the maximum midspan deflections. The strength and rigidity of the repaired beams were found to increase with increasing the width-to-thickness ratio of the steel plate.

Abstract: External bonding of steel plates to structural concrete members has widely gained popularity in recent years, particularly for repairing and strengthening reinforced concrete beams. The success of this bonding technique depends on the effectiveness of the surface preparation of the steel and concrete beams. Studies have shown that most of the beams strengthened using this technique usually fail prematurely by debonding. In this study, concrete beams with different types of surface preparations were investigated, such as no surface preparation (NSP), wire brushing (WB), scabbling (SC) and hand chipping (HC). The quality of the surface preparation established was measured based on the flexural performance of the externally strengthened steel-concrete beams. Eight (8), 250x450x3600 mm reinforced concrete beams were prepared and strengthened with glued steel plates on their soffits. All the specimens were tested under two-point static loading and failure modes were observed. The results showed that beams with rougher surface preparation have a high bond strength as compared to smoother surface preparations. The increase in the average capacity of strengthened beams with the surface prepared by hand-chipping, scabbling, wire brushing was found to be 75.3%, 67.5% and 46.9% respectively, compared to the capacity of the beam strengthened without surface preparation.

Abstract: The concept of strengthening reinforced concrete (RC) beams using epoxy-bonded steel plates (EBSP) is a well-known solution in structural engineering. Experimental investigations conducted in the past has proved that strengthening RC beams with steel plates are the most efficient, effective, and cost-effective technique of increasing the flexural performance of these elements. However, the focus has been on effect of the external bonded steel plate, and not on the effect of the overall steel contribution ratio on the behaviour of the strengthened beams. Several codes give the minimum reinforcement ratios for concrete beams in order to encourage/improve their flexural behaviour such as cracking and ductility failure. The purpose of this present study is to investigate the effect of the steel contribution ratio on the flexural behaviour of concrete beams strengthened on their tension face with epoxy bonded steel plate, using the experimental results obtained by various researchers in this field. The outcomes of strengthening RC beams are decrease in mid-span deflections, decrease in crack-widths, and increase in first crack load, and consequently increase in both serviceability load and ultimate load, thus making it to be the most feasible strengthening technique

Abstract: To solve the convergence problem of the building structures under the strong nonlinear condition, this paper develops a series of hybrid algorithms for strong nonlinear analysis of the building structures, which combine the advantages of explicit and implicit algorithms. In the time-domain hybrid algorithm, the switch between the implicit algorithm and the explicit is decided by the occurrence of iteration non-convergence when the implicit algorithm is used for the analysis of the whole building structure. And in the space hybrid algorithm, the whole structure is divided into several floor areas and interface areas to decouple the independent dynamic balance equation of each floor area by predicting the dynamic responses of interface, so that the proper dynamic integral algorithm of each area could be confirmed through its real state. The time-space hybrid algorithm, using the occurrence of the implicit algorithm iteration non-convergence as the switch criterion for the dynamic algorithm in the time domain and referring to the displacement difference vector of the iteration failure moment, can determine the area in the state of strong nonlinear and automatically partition the building structure according to the freedom number, then switch to the space hybrid algorithm to calculate the current time step. The hybrid dynamic algorithm realized in the self-development finite element analysis platform presents the superiority in solving the strong nonlinear problems over the Newmark algorithm when it is applied to the nonlinear time-history analysis of strong earthquake for building structures.

Abstract: Most researches about bushfire and wind, individually focuses on the origins, impacts and reconstruction process which are systematically studied after a devastating event. Indeed, it can reveal a lack of research as both bushfire and wind are interrelated and subsequently referred as ‘bushfire enhanced wind’. This phenomenon has long been acknowledged by researchers, however it’s understanding about the different interactions and effects still remain relatively limited. Therefore, this research addresses the impacts of bushfire enhanced wind over residential structures by numerical investigation using a finite element commercial software known as Abaqus. The model first simulates the most common type of wall system (i.e. masonry: double brick) in Australia with the results presented as pressures and stress distribution. Secondly, the finite element analysis emphasises on the critical sections (i.e. wall and roof connections) when the model contains an opening (i.e. window). The outcomes generated by the finite element analysis are expected to provide valuable understanding into the fire-wind interaction and subsequently impact the Australian Standards aimed at improving structural design within bushfire prone areas.

Abstract: It has long been known that extreme bushfire circumstances are always associated with violent winds. There has been a wealth of research devoted to investigating the effect of wind on bushfire spread, but only recently is attention being paid to the enhancement wind by fire and the subsequent impact on buildings. Previous studies have focused on building blocks with simple configurations, however, building structures in reality can be quite complex. This research examines the effects of bushfire-enhanced wind on a typical structural configuration, that is, a building with openings. The computational fluid dynamics approach was employed to reveal pressure distributions, wind velocity, and temperature profiles. The numerical simulations also revealed an interior flow within the building, which is believed to have been caused by the stack effect. Consequently, fire-generated wind pressure loading on the building is different to that on a building with no opening. The analytical information obtained will assist in research on structural response during intense bushfire, furthering the development of relevant standards for better protection of building structures against bushfire attacks.

Abstract: Base isolation (BI) systems have been found to be effective tools to safeguard multi-storey buildings and other structures from severe earthquake excitations. It requires the structure to be separated from the ground by isolation devices which can dissipate energy. This is proven technology which may add a little to the initial cost of the building, but will prove to be less expensive in the long term. Base isolation technology introduces flexibility into the connection between the structure and the foundation. In addition to allowing movement, the isolators are often designed to absorb energy and thus add damping to the system. Furthermore reduces the seismic response of the building and also enables a building or non-building structure (such as a bridge) to survive a potentially devastating seismic impact, following a proper initial design. This study discusses the concept of base isolation and reviews existing base isolation systems.

Abstract: Geopolymer has been known as an eco-friendly alternative to Portland cement-based concrete. Geopolymer concrete usually uses alkali-activated fly ash as the binder, and develops desirable strength within 8 hours when a heat-curing regime is used. Due to its ceramic-like properties, geopolymer concrete is believed to have high fire resistance. When heat-cured geopolymer concrete is exposed to high temperatures, a strength gain is often reported. However, the heat-curing procedure limits the future of geopolymers for on-site applications. To solve this issue, suitable additives (e.g., ground granulated blast-furnace slag and calcium aluminate cement) can be used in the binder which can develop the desirable strength of geopolymer concrete. It is important to understand the high-temperature performance of ambient-cured geopolymer concretes which have received little attention. This paper presents a study on the high-temperature performance of fly ash-based geopolymer concrete cured at ambient temperature. Compression tests were carried out on geopolymer mortars at temperatures of 23, 600 and 800 °C. As an outcome from this work, the authors have proposed a geopolymer concrete mixing design based on the parameter analysis, and the fire performance of the geopolymer concrete are compared with that of the reference OPC concrete at different temperatures.

Abstract: The aim of this study is to explore the initiation of stress concentrations around the base connections of columns made of cold-formed channels, and its influence on the combined ultimate axial and flexural capacity. Recent numerical studies on columns under axial load showed that welding the column’s flanges and/or web to the base plate causes significant stresses at the edges of the flange and web elements, which leads to premature failure of the column. In this paper, a finite element model of several cold formed lipped channel cross sections, connected rigidly to the base through the web only, flanges only and web and flanges only, is developed to create different boundary conditions at the bottom of the column. The models are subjected to axial load, and combined axial and moment through an eccentrically applied load. The study is extended to include the effect of the end distance of the welds on the capacity of the column.

Abstract: structural analysis tools in parametric platform are widespread, these tools rarely have the capability to estimate seismic responses rapidly and accurately. Considering the severe damage caused by strong earthquakes, a parallel finite element analysis tool is implemented as a plugin in the parametric modelling platform—Grasshopper. With the help of the series of components, engineers could achieve static analysis and nonlinear dynamic analysis to any structure. Some open-source codes are incorporated in the program using C++ programming language, which involve matrix calculation libraries, material constitutive models, etc. Two parallel computing strategies, the parallel state transformation procedures (PSTP) and the parallel factorization of Jacobian (PF), are adopted to make up for the low speed of nonlinear dynamic analysis. In Grasshopper, geometries are converted to structural models through nine new data types, i.e. Material, Section, Line Element, Shell Element, Load, Constraint, Analysis, Damping and Model. A case study on two 14-storey frame-shear wall structures with the same parametric modelling logic has demonstrated the operational convenience of the dynamic analysis tool. Variables include geometric variables, topological variables and structural variables. A top displacement time history is presented to show the different seismic performance of these structural models.

Abstract: Granular materials have wide applications in producing structural materials such as concrete and pavement. However, their behaviours are still limited understood. In recent years, characterizing and modelling the structure of granular materials under different conditions has become a hot multidisciplinary research topic attracting both scientists and engineers. In this work, we develop a numerical model based on discrete element method (DEM) to study the structure of granular materials in a container subjected to vibration. In particular, we investigate the influence of shape of the container on the self-assembly of the particles, i.e., the phase change from disordered to ordered structures. Our simulated containers are prisms with different bottom shapes (e.g., circle, equilateral triangle, square and hexagon). For each shape, we conduct simulations under different vibration frequencies and amplitudes. The structure of the vibrated granular material is characterized by packing density (porosity), coordination number, radial distribution function and bond orientation order parameters. Opting for desired vibrational parameters, it is found that the triangular container would produce comparatively more ordered structures. The simulation results manifest the effect of boundary and vibration on the structure of granular materials, which could provide the strategies for controlling the structure of granular materials for optimising the production of structural materials.

Abstract: This finite element study focuses on the compressive resistance of the cold-formed lipped channels, connected to the base through the web only. The influence of the cross-section geometry, column length and end distance on the ultimate capacity is investigated. The numerical models cover four end distances and three different values for the length of the column, flange width and lip width. A commercial finite element analyses software ABAQUS and a direct strength method (DSM) in were used to determine the nominal capacity of the columns. According to the observations and assumptions, this paper shows that the current DSM distortional equation is not safe for this boundary condition, however, the end distance has positive effect on the column capacity.

Abstract: Thermal analysis of both traditional and new advanced building materials can provide valuable information on their behaviour under different environmental conditions. This type of analysis involves techniques that look at changes in the physical, chemical and mechanical properties of a material as a function of temperature. The Advanced Materials Characterisation Facility (AMCF), located at Western Sydney University’s Parramatta campus, is home to a suite of thermal analysis instrumentation that are able to carry out various thermal analysis techniques on small scale samples. These techniques include Thermo-Gravitation Analysis (TGA), Differential Scanning Calorimetry (DSC), Infra-Red (FTIR) analysis of evolved gasses from TGA/DSC and Thermo-Mechanical Analysis (TMA). Properties that can be analysed include mass changes, material phase transitions (e.g. crystalline, amorphous, melting, etc), heat capacity, expansion, tension, young’s modulus, sintering, softening points, evolved gases and much more.This paper will provide an overview of each of the thermal analysis instruments housed at the AMCF. Examples of thermal analysis previously undertaken on various materials will also be given in order to show the potential of thermal analysis techniques on future construction materials.

The entire proceedings.