State of the art on pre-tensioning steel straps confinement: literature review

This paper presents the state-of-the-art of the current research development on pre-tensioning steel straps confinement. Critical review was conducted based on careful selection of references to provide in-depth overview in the development of this confining technique. The paper was started with highlighting the features of such confining technique, then an extensive description of the connection clip systems was presented. The experimental and numerical investigations performed on steel-strapped concrete structures were discussed at length in the paper. The potential usage of pre-tensioning steel straps confinement in increasing the bond properties of confined concrete and as a repairing technique of damaged concrete were also covered in this paper

Load-deformation behaviour of eccentrically loaded SSTT-confined high strength concrete columns

The application of steel-straps confinement or better known as steel-strapping tensioning technique (SSTT) has been proven to be effective in increasing the strength and ductility of High-Strength Concrete (HSC) column comparable to Fiber-Reinforced Polymer (FRP). However, most of the research of confined HSC column has mainly concentrated on concentric loading. In actual practical condition, most of the columns are subjected to eccentric loading. The scarcity of the experimental data for eccentric loaded confined HSC column has prevented the potential use of this type of structure element. In this paper, five HSC columns were tested. The specimens were SSTT-confined and tested with 25mm and 50 mm eccentric loading. The results show that SSTT confinement can increase the strength and deformability of high-strength concrete column, although the strain gradient reduces the confining efficiency. Therefore, smaller capacity enhancement factor should be used in eccentrically loaded SSTT-confined HSC columns compared to concentrically loaded columns. Furthermore, the non-linear theoretical model established in this study can be used for templates for future work on SSTT-confined HSC columns

State of the art on pre-tensioning steel straps confinement: literature review

This paper presents the state-of-the-art of the current research development on pre-tensioning steel straps confinement. Critical review was conducted based on careful selection of references to provide in-depth overview in the development of this confining technique. The paper was started with highlighting the features of such confining technique, then an extensive description of the connection clip systems was presented. The experimental and numerical investigations performed on steel-strapped concrete structures were discussed at length in the paper. The potential usage of pre-tensioning steel straps confinement in increasing the bond properties of confined concrete and as a repairing technique of damaged concrete were also covered in this paper

Excavation assessment in wet tropically sedimentary rock

The selection of suitable methods to be employed for surface excavation works is particularly important in geotechnical engineering projects. Factors such as environmental constrains, rock properties and size of site may affect the selection of machine required for surface excavation. Wrong selection of equipment and technique can result in unrecoverable expenses and thus, should be avoided. Great challenges in excavation works are expected in sedimentary rock where the occurrence of discontinuity such as bedding thickness, foliation and the inhomogeneity of rock as well as effect of moisture can greatly affect its excavatability. This paper aims to identify and highlight the factors affecting the excavation works in wet tropically weathered sedimentary area as what have been experienced in Malaysia. Some of these factors, however, are not specified in the existing general excavatability assessments. Assessment by practical excavation was carried out at three sedimentary rock sites in Nusajaya, Malaysia, taking into account the related parameters. Statistical analysis by using SPSS was then being conducted in order to determine the correlation of each parameter with productivity of excavation and their significance in affecting the excavatability.Based on the results obtained, it was found that the parameters such as Is50, R, UCS, density, ITS, Js, JL, Jd, IP and moisture content play significant roles in affecting the excavatability of sedimentary rocks. Meanwhile, the existence of bedding, Id2 and Jn are deemed to be neglected. It is believed that this study can help to enhance the knowledge on factors that complicate the excavation works in sedimentary area

Estimating uniaxial compressive strength of tropically weathered sedimentary rock using indirect tests

Uniaxial compressive strength (UCS) of intact rock is particularly important in rock mechanic studies, especially for those involving civil and mining projects. However, the determination of UCS using direct test is generally expensive, time consuming and almost impossible in preparation of samples for highly weathered sedimentary rocks. In view of this, indirect tests are comparatively cheap, simpler, faster and more convenient to perform either in laboratory or at site. This paper aims to develop an estimation procedure in determining the UCS values of such weak weathered rocks. Among the indirect tests present herein are point load index, Schmidt Rebound hammer, Brazilian tensile test and slake durability test. Unfortunately, it was found that the accuracy of each single test varies with weathering states. Hence, a recommended procedure using combined indirect tests in determining UCS of weak sedimentary rocks is presented herei

Behaviour of lightweight foamed concrete with pre-tensioning steel straps confinement

Due to its low compressive strength and ductility, lightweight foamed concrete (LFC) cannot be used in structural members such as beams, slabs and columns. One way to improve the strength and ductility of LFC is by confining the concrete laterally by using active external confinement. This research therefore aimed to investigate the effectiveness of external confinement by using low cost steel straps tensioning technique (SSTT) to the LFC columns. A total of 36 cylindrical specimens with 100 mm diameter, 200 mm height and density of 1500 kg/m3, 1650 kg/m3 and 1800 kg/m3 were prepared in this study. The strength of the LFC columns was significantly improved with the increase in number of layers and decrease in spacing of the SSTT confinement. This paper also presents the axial compression stress-strain relationship of the SSTT-confined LFC. SSTT confinement is proven to be effective in increasing the performance of the LFC columns, especially in the specimens with the density of 1500 kg/m3

Pullout behaviour of bars in concrete confined with post-tensioned steel straps

This paper presents the experimental results of bond and anchorage behaviours under Steel Strap Tensioning Technique (SSTT) confined high-strength concrete (HSC). The experimental tests consisted of pull-out test with short bond length and pull-out test with long bond length were performed to determine the bonding and anchorage capacity of SSTT-confined HSC. A total 36 specimens with short bond length and 16 specimens with long bond length were tested in this study. Three batches of concrete with compressive strength of 30 MPa, 60 MPa and 90 MPa were tested. Other parameter in this study was rebar diameter of 12 mm and 16 mm and different SSTT confinement ratios ranging from 0 to 0.2. To determine the effects of confinement on development bond and anchorage, an analytical expression was developed based on the parameters tested in this study. The equation is then verified with the bond strength proposed by the existing bond equations. The results from conducted tests indicated that the application of SSTT as an external confinement can increase the bond strength of confined concrete by up to 50%

Compressive strength of lightweight foamed concrete with charcoal as a sand replacement

Foamed concrete, a high performance concrete with lightweight properties and strength-enhancing additive have drawn the attention of researchers towards a sustainable life style. This paper presents a study of the compressive strength of various charcoal-filled lightweight foamed concrete (LFC), where waste materials, water-reducing agent and strength enhancement additives are introduced to the mix design in order to obtain further lightweight concrete. Five series of experimental tests were carried out, where Series 1 tested optimum ratio of silica fume and superplasticizer, Series 2 depicted the design mix of sand replacement with charcoal, Series 3 described the mix for additives, Series 4 illustrated effect of aggregate size for charcoal and different densities, as well as Series 5 was the conventional design mix ratio. The fresh and harden densities have been recorded while the shrinkage of LFC had also been observed during the casting and curing period. From the results, the mixture with silica fume replacing the cement was found to have a lower compressive strength as compared to mixtures with a full portion of cement. The strength reductions ranged between 62 to 80% for the mix with no superplasticizer and 29 to 82% for the mix with superplasticizer, which was obtained from the 20 to 50% of cement replacement with silica fume. Foamed concrete with superplasticizer achieved 66% of higher compressive strength. However, concrete expansion and spalling were discovered at the later concrete age of Series 5 which degraded the concrete strength. From this study, it was found that charcoal with low specific gravity is a suitable for full sand replacement in foamed concrete prior to the treatment that can lower its alkalinity

Time history shaking table test and seismic performance analysis of Industrialised Building System (IBS) block house subsystems

An Industrialised Building System (IBS) block house was innovated from safe room or hurricane shelter designs developed by the Federal Emergency Management Agency (FEMA) in the United States. This IBS block house is made by a pre-cast reinforced concrete block system designed for the purpose to protect inhabitants from natural disasters and other unpredictable events. To investigate its dynamic seismic performance, time history testing on a shaking table with 1:5 downscaled block house column and sub-frame models were carried out. Sabah earthquake 2015 with a PGA of 0.126 g was used as the input signal for the time history shake table test. The dynamic response and structural behaviour of the models subjected to increasing seismic intensities were investigated via the analysing of time history test data and the observed cracking pattern of the scaled models. Different dynamic parameters such as acceleration, displacement, and hysteresis responses were evaluated. Based on all the analysed parameters, it can be concluded that no severe damages occurred on either model even when the vibration is increased to PGA 1.0 g. Both tested models were classified in a serviceability stage after the experiment. Dynamic Finite Element Analysis (FEA) of the models was also conducted. Compared with experimental results, the FEA results show good agreement with high R2 values of 0.9612 and 0.9771 for column and sub-frame models respectively. Hence, both time history testing and numerical analysis give a better understanding on the seismic performance and dynamic behaviour of IBS block house models under real time earthquake

Rubber damping system of industrialised building system (IBS) block work house

The block work house with Industrialised Building System (IBS) is innovated to minimize the rate of casualties from earthquake disaster. In order to improve the ductility of IBS block work house, rubber dampers were used to resist dynamic motion of a structure under seismic event. Through the research, the seismic performance of the 1:5 down scaled IBS block work column was obtained. The objective of this research is to create a robust IBS column by improving the damping system. Time History Test on shake table was conducted for IBS column models to determine its structural behaviour under seismic loading. Three types of IBS column models with different rubber damper type and application were tested. The rubber damping properties for two different rubber types were also obtained. Sabah earthquake 2015 with the PGA of 0.126g was simulated for the time history shake table test. The dynamic parameters such as acceleration, response spectra, and displacement were evaluated. As the results of the study, it was found that the hard rubber has better damping properties than soft rubber. The rubber dampers that installed in xy-plane horizontally on the column system is effective as vibration isolator