Seismic performance of fixed offshore structures under far field earthquake

Malaysia is located at a very low seismic activity area but the active earthquake fault line is through the centre of Sumatran, Indonesia which lies just approximately 350km from Peninsular Malaysia. The earthquake that occurs in Indonesia was due to the strike-slip fault that has affected the building structure in Malaysia. It happens because of the amplification process generated from the source of the event. The aim of this study was to evaluate performance and vulnerability of offshore structures using real peak ground acceleration. Between 2004 and 2012, a few interpolate earthquake events with magnitudes of Mw = 3.5 were recorded. These data were provided by Malaysia Meteorological Department Malaysia (MMD) and 10 of the events were shallow strikeslip events. The earthquake Off West Coast of Sumatra that happened on 26th December 2004 has been selected as the biggest earthquake event in the Malaysia region during that time. By using regression analysis, attenuation function that has been developed and the value of maximum ground acceleration that hit offshore platform was identified. Using the real peak ground acceleration, vulnerability and performance of 5 models of typical offshore platforms were evaluated. The typical fixed offshore platform was analysed by using SAP 2000 finite element software. Time history analysis and pushover analysis were done on the models in which the results were compared to the resistance value itself and the performance indicator produced by FEMA-365. The offshore structure was analysed by several steps in pushover in terms of x-direction and y-direction and some parts of the structure were classified as Immediate Occupancy (IO), Life Safety (LS), and Collapse Prevention (CP) level of performance. Moreover, the results retrieved from the real scale analysis were compared to the experimental work that employed the harmonic shaking table machine. In conclusion, the findings contribute to the seismic performance of offshore platforms in Malaysia. It proves that the offshore platforms in the country is very well sustained with a high-end performance

Properties of concrete containing ground palm oil fuel ash as fine aggregate replacement

Environmental degradation resulting from increasing sand mining activities and disposal of palm oil fuel ash (POFA), a solid waste generated from palm oil mill needs to be resolved. Thus, the present research investigates the effect of ground palm oil fuel ash as partial fine aggregate replacement on workability, compressive and flexural strength of concrete. Five mixtures of concrete containing POFA as partial sand replacement designed with 0%, 10%, 20%, 30% and 40% of POFA by the weight of sand were used in this experimental work. The cube and beam specimens were casted and water cured up to 28 days before subjected to compressive strength and flexural strength testing respectively. Finding shows that concrete workability reduces as the amount of POFA added become larger. It is worth to note that 10% of POFA is the best amount to be used as partial fine aggregate replacement to produce concrete with enhanced strength

Seismic analysis for low-rise buildings based on different types of soil consideration

The earthquakes around the neighboring country caused Malaysia to experience small tremors from the quake. One of the distant earthquakes is the West Sumatra earthquake that affected several tremors felt in Peninsular Malaysia, causing vibrations in some areas and causing damage to buildings and injuries to people. The earthquake disaster that hit Ranau, Sabah on the 5th of June, 2015, increased the awareness of Malaysians on the matter of considering seismic design for the building. Consequently, the engineers in Malaysia should have to consider the seismic design and construction even though Malaysia has not encountered an active seismic fault zone. This undertaking will impact construction costs, specifically in terms of materials. As a result, this research analyses the cost of steel tonnage for structural work on a double-storey house with a seismic design. Because this study focuses on seismic design buildings in Malaysia, we applied the Malaysia National Annex to Eurocode 8. In this study, three steps involved which is the design of a primary model, structural analysis and seismic design, and finally, the take-off procedure. As a starting point, a double-storey house was constructed. The model considered all soil types. The reference peak ground acceleration, αg 0.07g applied for DCL. According to the simulation data, the expenditure of steel tonnage for the soil types A and B structure reduces the cost of steel R reinforcement by approximately 0% to 3%, against a non-seismic model, and, the expenditure of steel tonnage for the other soil types which are C, D and E structure increase the cost of steel reinforcement by approximately 4%, against a non-seismic model. By this means, the non-seismic models in this study required more steel reinforcement than the soil types A and B models due to the domination of wind load on the structure that produces a bigger force, and for the soil types C, D, and E models required more steel reinforcement than the non-seismic models because the soil softer compared to soil types A and B. In this study, the softer soil required more steel reinforcement compared to the stiff soil and the cost of steel reinforcement is anticipated to rise depending on the type of soil and the level of seismicity

Study on Durability Performance of Concrete Containing Laterite Aggregates

This paper addresses the durability performance of concrete containing laterite aggregate against corrosion, acid attack and carbonation. Two types of mixes were used, that is plain concrete (0% laterite aggregate) and another one, produced by integrating 20% of laterite aggregate as partial coarse aggregate replacement.  The corrosion resistance test was conducted by immersing the 28 days water cured specimens in sodium chloride for 1, 7 and 15 days. The steel bars were then connected to the data logger to determine the corrosion potential of each specimen. The acid resistance of specimens were investigated by immersing it in hydrochloric acid solution and the mass of cubes were measured at every 100 hour until 1800 hour. Carbonation depth was determined by spraying phenolphthalein indicator on broken surface of prism with curing age up to 1 year. The corrosion potential of both types of concrete rose as experimental period become longer. The acid resistance results show the difference in total mass loss of laterite concrete and control specimen is less than 5%. Carbonation results of the specimens are also close to each other. Utilization of 20% laterite aggregate as partial coarse aggregate replacement influences the resistance of concrete upon corrosion effect, acid attack and carbonation

Effect of Mixing Ingredient on Compressive Strength of Oil Palm Shell Lightweight Aggregate Concrete Containing Palm Oil Fuel Ash

AbstractThe increasingly generated oil palm shell (OPS) and palm oil fuel ash (POFA) which is a by-product of Malaysian palm oil mills annually, has lead towards the effort of integrating palm oil fuel ash as mineral admixture in lightweight aggregate concrete which produced using 100% oil palm shell as lightweight aggregate. This paper addresses the compressive strength of this oil palm shell lightweight aggregate concrete upon usage of different ash replacement level, water cement ratio, superplasticiser, sand and cement content. At the early state of investigation, cubes of (100x100x100mm) containing various replacement level of ash were produced and tested for it compressive strength. Then, the 20% replacement levels of POFA which give the highest compressive strength value were used for further experimental work. Experimental work to investigate the effect of water content, percentage of superplasticiser, sand content and amount of cement used were conducted using two types of mixes. Plain oil palm shell lightweight aggregate concrete (0% POFA) as reference specimen, and oil palm shell lightweight aggregate containing 20% palm oil fuel ash (20% POFA) were prepared in form of cubes. All the specimens were subjected to water curing until the testing date. The compressive strength test was conducted following the procedures in BSEN 12390 – 3 at 28 days. Integration of 20% POFA in oil palm shell lightweight aggregate concrete leads to production of a greener lightweight aggregate concrete product with optimum strength. Inclusion too much of water should be avoided as it diminishes the concrete compressive strength. Only right formulation of palm oil fuel ash, water, superplasticizer, sand and cement content would be able to produce oil palm shell lightweight aggregate concrete containing palm oil fuel ash exhibiting optimum strength

Seismic Effect of the Offshore Structure Under Different Earthquake Loadings

Peninsular Malaysia is most affected by the distant Sumatra subduction zone earthquake. Meanwhile, Eastern Malaysia was subjected to major Philippine and Indonesian earthquake. Most of the offshore platform is at Terengganu, Sabah, and Sarawak. More than 65% of the offshore platform structure exceed the range of design between 20-30 years. This research aims to determine the vulnerability and risk analysis for the existing 3-legged offshore platform under earthquake load, study the behaviors of an offshore platform under major or minor earth-quake loading, and study the dynamic characteristic of an offshore platform. SAP 2000 is use to analyses and modelling the 3-legged offshore platform. In SAP 2000, the response spectrum, time history, and free vibration will be performed. The mixed load of the platform consists of dead load, imposed load, environment loads, and earthquake load. The position of the offshore platform has referred to American Petroleum Institute (API) standard. The major earthquake under off-shore platform is El-Centro and the minor is Aceh compared to time history. Based on this study, Malaysia can withstand this low seismic activity, overall joint acceleration, velocity and displacement

Seismic Effect of the Offshore Structure Under Different Earthquake Loadings

Peninsular Malaysia is most affected by the distant Sumatra subduction zone earthquake. Meanwhile, Eastern Malaysia was subjected to major Philippine and Indonesian earthquake. Most of the offshore platform is at Terengganu, Sabah, and Sarawak. More than 65% of the offshore platform structure exceed the range of design between 20-30 years. This research aims to determine the vulnerability and risk analysis for the existing 3-legged offshore platform under earthquake load, study the behaviors of an offshore platform under major or minor earth-quake loading, and study the dynamic characteristic of an offshore platform. SAP 2000 is use to analyses and modelling the 3-legged offshore platform. In SAP 2000, the response spectrum, time history, and free vibration will be performed. The mixed load of the platform consists of dead load, imposed load, environment loads, and earthquake load. The position of the offshore platform has referred to American Petroleum Institute (API) standard. The major earthquake under off-shore platform is El-Centro and the minor is Aceh compared to time history. Based on this study, Malaysia can withstand this low seismic activity, overall joint acceleration, velocity and displacement

Evaluation of climate variability performances using statistical climate models

Uncertainty of the climates nowadays bring the crucial calamities problems especially at unexpected areas and in anytime. Thus, the projection of climate variability becomes significant information especially in the designing, planning and managing of water resources and hydrological systems. Numerous climate models with varies methods and purposes have been developed to generate the local weather scenarios with considered the greenhouse gasses (GHGs) effect provided by General Circulation Models (GCMs). However, the accuracy and suitability of each climate models are depending on the atmospheric characters’ selection and the variables consideration to form the statistical equation of local-global weather relationship. In this study, there are two well-known statistical climate models were considered; Lars-WG and SDSM models represent for the regression and weather typing methods, respectively. The main aim was to evaluate the performances among these climate models suit for the Pahang climate variability for the upcoming year Δ2050. The findings proved the Lars-WG as a reliable climate modelling with undemanding data sources and use simpler analysis method compared to the SDSM. It is able to produce better rainfall simulated results with lesser %MAE and higher R value close to 1.0. However, the SDSM lead in the temperature simulation with considered the most influenced meteorological parameters in the analysis. In year Δ2050, the temperature is expected to rise achieving 35°C. The rainfall projection results provided by these models are not consistent whereby it is expecting to increase 2.6% by SDSM and reduce 1.0% by Lars-WG from the historical trend and concentrated on Nov

Structure vulnerability and risk analysis of 3-legged offshore structure

Peninsular Malaysia is most affected by the distant Sumatra subduction zone earthquake. Meanwhile, Eastern Malaysia was subjected to major Philippine and Indonesian earthquake. Most of the offshore platform is at Terengganu, Sabah, and Sarawak. More than 65% of the offshore platform structure exceed the range of design between 20-30 years. This research aims to determine the vulnerability and risk analysis for the existing 3-legged offshore platform under earthquake load, study the behaviors of an offshore platform under major or minor earthquake loading, and study the dynamic characteristic of an offshore platform. SAP 2000 is use to analyses and modelling the 3-legged offshore platform. In SAP 2000, the response spectrum, time history, and free vibration will be performed. The mixed load of the platform consists of dead load, imposed load, environment loads, and earthquake load. The position of the offshore platform has referred to American Petroleum Institute (API) standard. The major earthquake under off-shore platform is El-Centro and the minor is Aceh compared to time history. Based on this study, Malaysia can withstand this low seismic activity, overall joint acceleration, velocity and displacement

Structure vulnerability and risk analysis of 4-legged offshore structure

Offshore structures are commonly used in oil and gas collecting sector. This industry is one of the major economic sector in Malaysia. Since distant earthquakes from neighbour countries (Indonesia and Philippines) had caused significant structural damages in the past few years, the perfomance level of offshore due to seismic effect need to be undergone detailed investigation. Therefore, this research aims to investigate the vulnerability and analyze the risk of 4-legged fixed offshore structure under different excitations. In order to achieve the objectives, SAP 2000 was chosen to analyze the offshore structure modelling by referring to the API (American Petroleum Institute) criteria. Time history, response spectrum and free vibration analysis have been performed. The behaviour of the offshore structure was observed and evaluated through the natural frequencies and periods. Meanwhile, results outcome of the joint displacement, velocity, and acceleration represented the dynamic characteristic of the structure. The 4-legged fixed offshore structure categorized as Immediate Occupancy (IO) based on FEMA 356 guidelines. From the results, it showed that existing 4-legged offshore structures in Malaysia are capable to resist seismic loads and in stable condition