Siti Aminah Osman

Application of shape memory alloy bars in self-centring precast segmental columns as seismic resistance

The objective of this study is to investigate analytically the performance of self-centring precast segmental bridge columns with shape memory alloy (SMA) starter bars under nonlinear static and lateral seismic loading. For this purpose, a 3D finite element model for hybrid post-tensioned bridge column has been developed. The precast post-tensioned segmental bridge columns possessing a central tendon and adequate transverse confinement provided by the steel tube jacketing as self-centring bridge columns have an undesirable high lateral seismic demand due to their low energy dissipation. In order to eliminate this deficiency while keeping the residual displacement small, SMA starter bars are applied in this system. The effect of post-tensioning (PT) forces of the central strands and SMA bar size are investigated. The results indicate that in high seismicity zones, bridge columns with SMA bars at a higher level of PT forces have a superior performance against earthquake loading.

A numerical study on seismic response of self-centring precast segmental columns at different post-tensioning forces

Precast bridge columns have shown increasing demand over the past few years due to the advantages of such columns when compared against conventional bridge columns, particularly due to the fact that precast bridge columns can be constructed off site and erected in a short period of time. The present study analytically investigates the behaviour of self-centring precast segmental bridge columns under nonlinear-static and pseudo-dynamic loading at different prestressing strand levels. Self-centring segmental columns are composed of prefabricated reinforced concrete segments which are connected by central post-tensioning (PT) strands. The present study develops a three dimensional (3D) nonlinear finite element model for hybrid post-tensioned precast segmental bridge columns. The model is subjected to constant axial loading and lateral reverse cyclic loading. The lateral force displacement results of the analysed columns show good agreement with the experimental response of the columns. Bonded post-tensioned segmental columns at 25%, 40% and 70% prestressing strand stress levels are analysed and compared with an emulative monolithic conventional column. The columns with a higher initial prestressing strand levels show greater initial stiffness and strength but show higher stiffness reduction at large drifts. In the time-history analysis, the column samples are subjected to different earthquake records to investigate the effect post-tensioning force levels on their lateral seismic response in low and higher seismicity zones. The results indicate that, for low seismicity zones, post-tensioned segmental columns with a higher initial stress level deflect lower lateral peak displacement. However, in higher seismicity zones, applying a high initial stress level should be avoided for precast segmental self-centring columns with low energy dissipation capacity.

THE NATURAL FREQUENCIES OF COMPOSITE PROFILED STEEL SHEET DRY BOARD WITH CONCRETE INFILL (PSSDBC) SYSTEM

This paper aims to measure natural frequencies of Profiled Steel Sheet Dry Board (PSSDB) with Concrete infill (PSSDBC) system. For this purpose, experimental tests by estimation of Frequency Response Function (FRF) and a numerical method by development of Finite Element Model (FEM) are used. The connection stiffness between Peva45 as Profiled Steel Sheet (PSS) and different concrete grades of 25 (C25), 30 (C30), and 35 (C35) are measured by push-out tests to be used in the FEM. The effect of presence of concrete in the PSSDB system on the natural frequencies such as Fundamental Natural Frequency (FNF) of the system is investigated. The variability in the FNF of the studied system under different parameters such as concrete grades, thicknesses of PSS and Dry Board (DB), and boundary conditions is determined. In a wide numerical study, the FNF of the PSSDBC system with practical dimensions is revealed for different lengths, widths, and boundary conditions. The results help designer predict serviceability and design criteria of the studied panels.

Dynamic response of low frequency Profiled Steel Sheet Dry Board with Concrete infill (PSSDBC) floor system under human walking load

This paper investigates the dynamic response of a composite structural system known as Profiled Steel Sheet Dry Board with Concrete infill (PSSDBC) to evaluate its vibration serviceability under human walking load. For this point, thirteen (13) PSSDBC panels in the category of Low Frequency Floor (LFF) were developed using Finite Element Method (FEM). The natural frequencies and mode shapes of the studied panels were determined based on the developed finite element models. For more realistic evaluation on dynamic response of the panels, dynamic load models representing human walking load were considered based on their Fundamental Natural Frequency (FNF), and also time and space descriptions. The peak accelerations of the panels were determined and compared to the limiting value proposed by the standard code ISO 2631-2. Effects of changing thickness of the Profiled Steel Sheet (PSS), Dry Board (DB), screw spacing, grade of concrete, damping ratio, type of support, and floor span on the dynamic responses of the PSSDBC panels were assessed. Results demonstrated that although some factors reduced dynamic response of the PSSDBC system under human walking load, low frequency PSSDBC floor system could reach high vibration levels resulting in lack of comfortableness for users.

Behaviour of stiffened concrete-filled steel composite (CFSC) stub columns

This paper investigates the behaviour of axially loaded stiffened concrete-filled steel composite (CFSC) stub columns using the finite element software LUSAS. Modelling accuracy is established by comparing results of the nonlinear analysis and the experimental test. The CFSC stub columns are extensively developed using different special arrangements, number, spacing, and diameters of bar stiffeners with various steel wall thicknesses, concrete compressive strengths, and steel yield stresses. Their effects on the columns behaviour are examined. Failure modes of the columns are also illustrated. It is concluded that the parameters have considerable effects on the behaviour of the columns. An equation is proposed based on the obtained results to predict the ultimate load capacity of the columns. Results are compared with predicted values by the design code EC4, suggested equation of other researchers, and proposed equation of this study which is concluded that the proposed equation can give closer predictions than the others.

Axial Load Behavior of Acomposite Wall Strengthened with an Embedded Octagon Cold-Formed Steel

This study investigates the axial load behavior of an existing composite wall consists of a double-skinned profiled steel sheet in-filled with normal concrete. Three different composite walls in three-dimensional finite element models were developed, i.e. profiled steel sheet (PSS), core concrete, and the full composite wall system. The models were simulated and compared with the experimental results published by other researchers. Studies are then carried out on different effect of varying the PSS thicknesses, an embedded octagon cold-formed steel (CFS) thickness, and an embedded octagon CFS supported by two stiffeners with different shapes. As a result, the ultimate axial load of the composite wall was increased by approximately 3.3% when PSS thickness changed from 0.8 mm to 1.0mm. Meanwhile, the ultimate axial load was also increased by 17% and 55% when an embedded octagon CFS with thicknesses of 0.8 mm and 1.0 mm were used. Lastly, the ultimate axial load was raised by 54% and 78% when an L-shaped and a T-shaped stiffener were added.

Numerical study of concrete-filled steel composite (CFSC) stub columns with steel stiffeners

Numerical study of concrete-filled steel composite (CFSC) stub columns with steel stiffeners is presented in this paper. The behaviour of the columns is examined by the use of the finite element software LUSAS. Results from nonlinear finite element analyses are compared with those from corresponding experimental tests which uncover the reasonable accuracy of the modelling. Novel steel stiffeners are used in the CFSC stub columns of this study. The columns are extensively developed considering three different special arrangements of the steel stiffeners with various number, spacing, and widths of the stiffeners. The main variables are: (1) arrangement of the steel stiffeners (C1, C2, and C3); (2) number of the steel stiffeners (2 and 3); (3) spacing of the steel stiffeners (50 mm and 100 mm); (4) width of the steel stiffeners (50 mm, 75 mm, and 100 mm); (5) steel thickness (2 mm, 2.5 mm, and 3 mm); (6) concrete compressive strength (30 MPa, 40 MPa, and 50.1 MPa); (7) steel yield stress ( 234.3 MPa, 350 MPa, and 450 MPa). Effects of the variables on the behaviour of the columns are assessed. Failure modes of the columns are also illustrated. It is concluded that the variables have considerable effects on the behaviour of the columns. Moreover, ultimate load capacities of the columns are predicted by the design code EC4, suggested equation of other researchers, and proposed equation of the authors of this paper. The obtained ultimate load capacities from the analyses are compared with the predicted values. It concludes that EC4 gives more conservative predictions than the equations.

Dynamic response of low frequency Profiled Steel Sheet Dry Board (PSSDB) floor system

Slender structural floors could experience irritating vibration problems due to human walking load and so, vibration acceptability of such floors is an essential subject in addition to the usual strength criterion. This paper focuses on the dynamic response of a lightweight composite structural system known as Profiled Steel Sheet Dry Board (PSSDB) to evaluate its vibration acceptability under human walking load. For this point, twelve (12) PSSDB panels in the category of Low Frequency Floor (LFF) were developed via Finite Element Method (FEM). The natural frequencies and mode shapes of the studied panels were determined based on the developed finite element models. For more realistic evaluation on dynamic response of the panels, dynamic load models representing human walking load were considered based on their Fundamental Natural Frequency (FNF), and also time and space description. The peak accelerations of the studied panels were determined and then compared to the limiting value proposed by the standard code of ISO 2631-2. Effects of changing thickness of the Profiled Steel Sheet (PSS) and Dry Board (DB), screw spacing, damping ratio, type of support, and floor span on the dynamic responses of the PSSDB panels were evaluated. According to literature, effect of presence of concrete on the dynamic response of the PSSDB system was revealed. The results demonstrated that although some factors reduced dynamic response of the PSSDB system under human walking load, low frequency PSSDB floor system could reach high vibration levels resulting in lack of comfortableness for users.

INVESTIGATION OF CONCRETE-FILLED STEEL COMPOSITE (CFSC) STUB COLUMNS WITH BAR STIFFENERS

Abstract This paper is concerned with the investigation of concrete-filled steel composite (CFSC) stub columns with bar stiffeners. In order to study the behaviour of the columns, the finite element software LUSAS is used to conduct the non-linear analyses. Results from the non-linear finite element analysis and the corresponding experimental test are compared which reveal the reasonable accuracy of the three-dimensional finite element modelling. A special arrangement of bar stiffeners in the columns with various number, spacing and diameters of the bar stiffeners are developed and studied using the non-linear finite element method. Effects of various variables such as different number and spacing of the bar stiffeners and also steel wall thicknesses on the ultimate axial load capacity and ductility of the columns are examined. Moreover, effects of different diameters of the bar stiffeners, concrete compressive strengths and steel yield stresses on the ultimate axial load capacity of the columns are evalu...

Physical Damages Effect on Residential Houses Caused by the Earthquake at Ranau, Sabah Malaysia

Earthquake, the destructive natural disaster had recently stormed East Malaysia. This study aims to identify the physical effects of the earthquake to the building that occurred in Sabah, Malaysia. A survey method had been conducted among 221 citizens in the affected area to meet the requirements of this research objective. The result shows that 68% responded that building cracks had formed on the wall, 48% cracked floor, 23% cracked columns, 10% damages on roof and 8% responded no damages at all while only 2% stated the total collapse of the houses’ structures. Researchers have also identified that the impact of the earthquake towards their house yards shows that 55% and 12% responded experienced cracks on ground and landslide respectively, 25% with flood occurrence and 1% are caught with fire. Finally, almost 90% of the respondents are ready to upgrade their house structures. Thus, this research will be continued by developing the retrofitting and strengthening methods for the low rise buildings.