Shear behaviour of permanent precast formwork beams

An experimental research was conducted to evaluate the shear capacity of permanent precast formwork beams and compared to normal cast in-situ concrete beams. The traditional approach of normal construction uses conventional timber and plywood, which requires laborious and time consumption of installation. This paper studies the shear behaviour of permanent precast concrete beams using different glass fibre volume (ranging from 0% and up to 1%) in mortar mixes to act as permanent formwork. The mechanical properties tests involved in the mortar were compressive and flexural strength tests. The optimum content of glass fibre then was determined based on several trial mixes made beforehand. Two permanent precast formwork beams, one used 0.52% of glass fibre and the other one used wire mesh were tested under av/d = 1.5 and compared with normal control beam. All beam specimens were tested to obtain the ultimate shear load. The results showed that permanent precast formwork beam with wire mesh gave better performance in terms of ultimate load. Measured shear capacities of the tested beams were then compared with the theoretical values calculated according to BSEN1992:2004

Fresh properties and mechanical properties of steel fibre self-compacting concrete

This paper investigates the fresh properties and mechanical properties of steel fibre selfcompacting concrete (SFSCC). Self-Compacting Concrete (SCC) has several advantages over normal concrete. SCC does not require any efforts of vibrations as it becomes compacted under its own weight. The application of SCC can be greatly improved with steel fibres, randomly added into the mixtures as to enhance the performance of concrete matrix. Addition of steel fibre has shown an improvement on the mechanical properties of concrete such as the tensile and flexural performance. The aim of this study is to determine the mechanical performance of SFSCC with different percentage of steel fibres and also to observe the fresh properties of SCC with and without steel fibres compare to the normal vibrated concrete (NC). In order to compare the performance of SFSCC, the properties of NC and SCC were also studied. The volume percentage of steel fibre is varies at every increment of 0.25% from 0 to 1.25% The results reveal that the addition of steel fibres in concrete matrix shows better mechanical performance compared with NC and SCC with percentage increment more than 50% for tensile, flexural and toughness testing. However, this study also concludes that steel fibre has no significant improvement to the compressive strength where the increament is very little. Based on the overall results obtained from this study, the performance of steel fibre self-compacting concrete shows a significant improvement with the capabilities in absorbing relatively large capacity of energy while delaying the propagation of crack, thus, preventing sudden failure in the concrete matrix as happened in most of conventional concrete

Fresh and hardened properties of self-compacting lightweight concrete using coarse palm oil clinker

The utilisation of industrial waste from the palm oil industry offers benefit to the construction industry and environment. This paper presents the experimental investigation of the fresh and hardened properties of self-compacting lightweight concrete (SCLWC) using coarse palm oil clinker (POC). In this study, POC, a waste by-product of palm oil mill, was utilised at 100 % full replacement of coarse aggregates in the production of self-compacting concrete (SCC). Fresh properties of the concrete mix were determined through tests of slump flow, V-funnel, J-ring, L box and sieve segregation. Meanwhile, the hardened concrete properties were evaluated by means of density, ultrasonic pulse velocity (UPV), compression, tensile splitting and flexural tests. The fresh and hardened properties of SCLWC were compared to normal SCC using normal weight coarse aggregates. Test results indicated that the SCLWC exhibited accepted self-compacting characteristics as recommended by European Guidelines. The SCLWC can be classified as lightweight concrete since its hardened density at 28 days was 1985 kg/m3 and good in quality according to its UPV values. In addition, the substitution of POC reduced the compressive and tensile strengths of the concrete due to its lightweight and porous nature. Based on the performance of SCLWC utilising coarse POC aggregates, the POC is potentially viable to replace natural aggregates and suitable to be used in SCLWC

The thermal response of concrete frame building in Arabic area considering time-dependent properties of concrete

The Arabic area is known for its high temperatures especially during the summer period. It affects the structural displacements and stresses in concrete elements. The main objectives of this paper are to study the effects of thermal loads on the response of super-long reinforced concrete frame buildings in the Arabic area and regions with similar temperature variation patterns, accounting for various design aspects considering both methodologies of time dependent properties of concrete as per CEB FIP 90 code and non-time dependent properties as per ACI 224.3R. To achieve these objectives a total of 272 one story reinforced concrete frame buildings are numerically modelled and analyzed using the finite element procedures of ETABS. The models are divided into two different groups. The first group is with columns fixed supports, the second group is with columns hinged supports. Each group is analyzed twice: once with time dependent concrete properties, and another with non-time dependent concrete properties. The study findings are utilized to develop a clear understanding about mentioned variables effects at thermal deformations and columns reactions to aid structural engineers in the thermal design of super-long buildings with similar conditions of this study within time. The horizontal deformations values increase proportionally with the increase of slab length and column height. The horizontal reactions increase proportionally with the increase of slab length and slab thickness values. Fixed columns horizontal reactions are more than horizontal reactions related to hinged columns conditions while column height is inversely proportional with the lateral reaction’s values. Time dependent properties deformations and reactions ratios are around 160% the non-time dependent properties result for all cases. Ignoring this difference imposes defects, additional cracks and damages at the structures and related serviceability conditions for 70 years period

The effects of seasonal thermal loads at expansion joints locations in Arabic area buildings

Concrete buildings are subjected to fluctuation in seasonal temperature loads between summer and winter in the Arabic area. The long-term effects on buildings of such temperatures, along with the frequent fluctuation in the seasonal temperatures impose overall structural deformation, displacements, and alteration of stresses in concrete elements. The thermally induced deformations affect the serviceability conditions of buildings with time. Concrete creep and shrinkage will increase the cracks widths and the imposed stresses too. To eliminate this phenomenon effects, expansion joints should be provided. However, as per the buildings functions and trend to develop unique buildings by designers, joint-less buildings are usually the preferred option. When using this option, the structural engineer has to consider the effects of thermal loads changes in the design. Clear rules and standards must be provided to define the maximum joints spacing’s allowed length in addition to thermal study procedures. Different approaches are provided by researchers, each methodology provide different value for required joints spacing considering different aspects in design. In this paper I shall try to present three methods with comparison study for considered aspects and gaps for each method analysis to propose the most appropriate methodology as a tool helps engineers in calculating the maximum allowed spacing between expansion joints

Bond behaviour of deformed steel bars in steel fibre high-strength self-compacting concrete

Research on the bond behaviour between deformed steel bars and the Self-Compacting Concrete (SCC) has been conducted extensively. However, bond study using the high-strength SCC (HSSCC) added with steel fibres is still rare and has not been fully explored. Therefore, in this study, experimental works were carried out to investigate the effects of adding 1% hooked-end steel fibres on the bond behaviour between deformed steel bars and the Steel Fibre High-Strength Self-Compacting Concrete (SFHSSCC) using the direct pullout test method. A total of 39 cubes of HSSCC and SFHSSCC pullout specimens with a dimension of 200 mm were prepared and tested. Highyield deformed steel bars were used as reinforcement bars. The effects of bar sizes (12, 16 and 20 mm diameter), concrete cover (94, 92, 90 and 35 mm thickness), embedment length (3 and 5 times bar diameter) and concrete age (30 ± 2 days and 6 months) towards the mode of failures and bond stress-slip curves were investigated. Coring samples were also taken from the pullout specimen to examine the distribution of the steel fibres. The results showed that size effects in rebars and the concrete cover thickness did not affect the mode of failures for a well-confined SFHSSCC as all bar sizes exhibit the same bond failure, which is pullout failure. More importantly, the addition of steel fibres enhanced the bond ductility in SFHSSCC through the passive confinement effects. The addition of steel fibres to SFHSSCC specimens bonded with 20 mm diameter bars also changed the failure mode from premature splitting to pullout. Meanwhile, the self-flowable SFHSSCC mixture effectively flowed and distributed the steel fibres within the concrete matrix

Comparison of bond stresses of deformed steel bars embedded in two different concrete mixes

Catenary action in a precast concrete building structural system is one of the ways to avoid progressive collapse. The key for catenary action to work successfully depends on the strength performance of longitudinal ties, which closely depends on the bond performance between the ties and concrete. This paper investigates the effectiveness of deformed steel bar as catenary tie in precast concrete beam-column connection under column removal scenario. The main objective of the experimental work is to improve the bond performance between deformed steel bar and concrete topping. The parameter considered in the tests is the types of concrete for the topping. The different concrete mixes are normal concrete of Grade 40 and steel fiber reinforced concrete (SFRC). A series of pullout test specimens are conducted to investigate the bond behavior between the steel ties and the surrounding concrete. The results show the comparison of bond stresses of embedded deformed steel bars in two types of concrete mix. The deformed steel bar with concrete fiber provides higher bond strength as compared to bond in normal concrete. Therefore, it is more suitable for effective catenary tie in precast concrete beam-column connection for maximum efficiency and deformability in order to minimize progressive collapse

Palm Oil Clinker as Noise Control Materials

Palm oil clinker (POC) is a waste from the production process of palm oil, a hard and porous materials. Many studies have focused on the effect of POC use on strength while this study discusses the ability of POC in concrete to absorb sound and its relationship with concrete properties. The study was done by replacing natural river sand in stages of 25, 50, 75 and 100 percent in a mixture of 1: 4 (cement: sand). Sound absorption coefficient (SAC), strength and physical properties affect the SAC were measured. Although POC significantly reduced the compressive strength but all specimens poses good strength more than 5 N/mm2. An interesting result is that POC reduces interconnected porosity and total porosity when replacement is 100% but increases interconnected and total porosity when replacement is between 50 and 75%. SAC at 315 Hz was found has good relationship with percentage of POC and density. It is obtained that POC 50% yield good strength and sufficient SAC that can address the middle frequency range problem, thus can be further suggested to be used for masonry block application for noise control materials

Influence of rectangular steel splice-sleeve for precast concrete connection

Precast concrete building system has gained its popularity in Malaysia because of the many advantages such as high quality of structural components, less labour intensive at the construction site, and shorter completion time of a project. One of the constraints in precast concrete structures is to ensure that the connections are strong enough to ensure the structural integrity and robustness of the overall frames. In this study, a total of nine rectangular steel splice-sleeve connections were tested experimentally under incremental tensile loads. Two steel plates were inserted and welded to each end of the steel splice-sleeve. The steel plates act as shear key to provide the interlocking mechanism to the grout and to enhance the bond property between the grout and the splice. These plates were adopted to prevent the grout slippage from the sleeve. The grout strength, embedded steel bar lengths and the size of the steel sleeve splice were varied among the specimens to study their effect on the tensile performance of the connection. The results showed that the higher strength of grout, longer embedded length of steel bar and smaller size of the sleeve contributes to a higher ultimate tensile load

Mechanical properties of lightweight concrete using palm oil clinker: an overview

The use of industrial waste as construction material to build environmentally sustainable structure has several practical and economic advantages. Palm oil clinker is a waste material obtained by burning off solid wastes during the process of palm oil extraction. The research performed over the last two decades concerning the use of palm oil clinker as lightweight aggregates concrete is summarized in this paper. A series of concrete mixes were studied and analysed in replacing the coarse and fine aggregates by palm oil clinker. The mechanical properties of the palm oil clinker lightweight concrete are addressed and discussed. The specific gravity for the palm oil clinker must be less than the normal weight aggregate which is below 2.20. The parameters of mechanical properties were reviewed included compressive strength, tensile strength (flexural and splitting) and Young’s modulus. The review showed the positive impact in concrete properties when replaced the normal coarse and fine aggregates with the palm oil clinker. The range of compressive strength of the palm oil clinker lightweight concrete was 30 to 44 MPa. This indicates that palm oil clinker concrete has potential for a replacement which helps in producing a sustainable environment thus contributing to effective construction cost