Excellence in Research and Innovation for Humanity

International Science Index

Commenced in January 1999 Frequency: Monthly Edition: International Abstract Count: 46013

Structural and Construction Engineering

Hygrothermal Assessment of Internally Insulated Prefabricated Concrete Wall in Polish Climatic Conditions
Internal insulation of external walls is often problematic due to increased moisture content in the wall and interstitial or surface condensation risk. In this paper, the hygrothermal performance of prefabricated, concrete, large panel, external wall typical for WK70 system, commonly used in Poland in the 70’s, with inside, additional insulation was investigated. Thermal insulation board made out of hygroscopic, natural materials with moisture buffer capacity and EPS board was used as interior insulation. Experience with this natural insulation is rare in Poland. The analysis was performed using WUFI software. First of all the impact of various standard boundary conditions on the behavior of the different wall assemblies was tested. The comparison of results showed that the moisture class according to the EN ISO 13788 lead to too high values of total moisture content in the wall. Given that the boundary condition according to the EN ISO 15026 should be usually applied. Then hygrothermal 1D-simulations were conducted by WUFI Pro for analysis of internally added insulation, and the weak point like the joint of the wall with the concrete ceiling was verified using 2D simulations. Results showed that in the Warsaw climate and the indoor conditions adopted in accordance with PN-EN 15026, in the tested wall assemblies, regardless of the type of interior insulation, there would not be any problems with moisture - inside the structure and on the interior surface.
Optimum Design of Dual-Purpose Outriggers in Tall Buildings
In this study, outriggers, which are horizontal structures connecting a building core to distant columns to increase the lateral stiffness of a tall building, are used to reduce differential axial shortening in a tall building. Therefore, the outriggers in tall buildings are used to serve the dual purposes of reducing the lateral displacement and reducing the differential axial shortening. Since the location of the outrigger greatly affects the effectiveness of the outrigger in terms of the lateral displacement at the top of the tall building and the maximum differential axial shortening, the optimum locations of the dual-purpose outriggers can be determined by an optimization method. Because the floors where the outriggers are installed are given as integer numbers, the conventional gradient-based optimization methods cannot be directly used. In this study, a piecewise quadratic interpolation method is used to resolve the integrality requirement posed by the optimum locations of the dual-purpose outriggers. The optimal solutions for the dual-purpose outriggers are searched by linear scalarization which is a popular method for multi-objective optimization problems. It was found that increasing the number of outriggers reduced the maximum lateral displacement and the maximum differential axial shortening. It was also noted that the optimum locations for reducing the lateral displacement and reducing the differential axial shortening were different. Acknowledgment: This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Science and ICT (NRF-2017R1A2B4010043) and financially supported by Korea Ministry of Land, Infrastructure and Transport(MOLIT) as U-City Master and Doctor Course Grant Program.
The Effect of Heat Treatment on the Corrosion Behavior of Stainless Steel
The work described in this report examines the aqueous corrosion behavior of duplex grades of stainless steel which are used as corrosion resistant castings for applications such as valve and pump bodies. The corrosion behavior of steels in the as-cast condition has been examined using potentiostatic studies to illustrate the need for correct thermal treatment. A metallurgical examination and chemical analysis were carried out to establish the morphology of the steel structure. Optical and scanning electron microscopy examinations confirmed that the austenitic steels will suffer from severe localized interdendritic pitting attack, while highly alloyed duplex steels will give inferior corrosion resistance if castings are not homogenized and solution treated by water quenching before service.
Practical Methods to Predict the Actual Completion Date of the Project
One of the most important issues for stakeholders, managers and the entire body of the project is to know the actual completion date of the project. Lack of knowledge of this subject and lack of familiarity with the techniques of estimating the actual completion date of the project, additional to the mistaken decisions made by the project managers and stakeholders, will result in financial and credibility losses for the project implementers. This paper presents some of the most practical techniques for predicting the actual completion date used in construction projects, reviewing the conditions of use, and the strengths and weaknesses of each of the techniques.
Performance-Based Design Analysis for Vertical Extension of Residential Structure
There is no reinforcement example for the vertical expansion of existing of structures in Korea. Among these existing structures, the shear wall structures are rare from overseas, while Korea has many shear wall apartment houses. Recently, in Korea, few researchers are trying to confirm the possibility of vertical expansion in existing building with shear walls. This study evaluates the possibility of expansion by applying performance-based seismic design to existing buildings with shear walls in the analysis phase of the structure. In addition, force-based seismic design, used by general structural practitioners in Korea, is carried out to compare the amount of reinforcement of wall, which is the main component of the wall structure. As a result, it suggested that the performance-based design obtain more economical advantages than the force-based seismic design.
Influence of Cathodic Protection on High Strength, Pre-Stressed Corroded Tendons
Cathodic protection (CP) is a technique commonly used to arrest corrosion of steel in infrastructure. However, it is not generally used on high strength, pre-stressed tendons due to the risk of hydrogen generation, leading to possible embrittlement. This paper investigates its use in such circumstances where the applied protection potential is varied to determine if CP can be safely employed on pre-stressed tendons. Plain steel tendons measuring 5.4 mm diameter were pre-stressed in timber moulds and embedded in sand/cement mortar, formulated to represent gunite. Two levels of pre-stressing were investigated (400MPa and 1200MPa). Pre-corrosion of 0% (control), 3% and 6% target loss of cross-sectional area was applied to replicate service conditions. Impressed current cathodic protection (ICCP) was then applied to the tendons at two levels of potential to identify any effect on strength. Instant-off values up to -950mV were used for normal protection with values of -1100mV or more negative to achieve overprotection. Following the ICCP phase, the tendons were removed from the mortar, cleaned and weighed to confirm actual percentage of corrosion. Tensile tests were then conducted on the tendons. The preliminary results show the influence of normal levels and overprotection of CP on the ultimate strength of the tendons.
Investigation of Light Transmission Characteristics and Co2 Capture Potential of Microalgae Panel Bioreactors for Building Façade Applications
Algae-culture offers new applications in sustainable architecture with its continuous productive cycle, and a potential for high carbon dioxide capture. Microalgae itself has multiple functions such as carbon dioxide fixation, biomass production, oxygen generation and waste water treatment. Incorporating microalgae cultivation processes and systems to building design to utilize this potential is promising. Microalgae cultivation systems, especially closed photo bioreactors can be implemented as components in buildings. And these systems be accommodated in the façade of a building, or in other urban infrastructure in the future. Application microalgae bio-reactors of on building’s façade has the added benefit of acting as an effective insulation system, keeping out the heat of the summer and the chill of the winter. Furthermore, microalgae can give a dynamic appearance with a liquid façade that also works as an adaptive sunshade. Recently, potential of microalgae to use as a building component to reduce net energy demand in buildings becomes a popular topic and innovative design proposals and a handful of pilot applications appeared. Yet there is only a handful of examples in application and even less information on how these systems affect building energy behavior. Further studies on microalgae mostly focused on single application approach targeting either carbon dioxide utilization through biomass production or biofuel production. The main objective of this study is to investigate effects of design parameters of microalgae panel bio-reactors on light transmission characteristics and CO2 capture potential during growth of Nannochloropsis occulata sp. A maximum reduction of 18 ppm in CO2 levels of input air during the experiments with a % light transmission of 14.10, was achieved in 6 day growth cycles. Heat transfer behavior during these cycles was also inspected for possible façade applications.
Analysis and Design of Offshore Triceratops under Ultra-Deep Waters
Offshore platforms for ultra-deep waters are form-dominant by design; hybrid systems with large flexibility in horizontal plane and high rigidity in vertical plane are preferred due to functional complexities. Offshore triceratops is relatively a new-generation offshore platform, whose deck is partially isolated from the supporting buoyant legs by ball joints. They allow transfer of partial displacements of buoyant legs to the deck but restrain transfer of rotational response. Buoyant legs are in turn taut-moored to the sea bed using pre-tension tethers. Present study will discuss detailed dynamic analysis and preliminary design of the chosen geometric, which is necessary as a proof of validation for such design applications. A detailed numeric analysis of triceratops at 2400m water depth under random waves is presented. Preliminary design confirms member-level design requirements under various modes of failure. Tether configuration, proposed in the study confirms no pull-out of tethers as stress variation is comparatively lesser than the yield value. Presented study shall aid offshore engineers and contractors to understand suitability of triceratops, in terms of design and dynamic response behaviour.
Quantification of Factors Contributing to Wave-in-Deck on Fixed Jacket Platforms
Wave-in-deck phenomenon for fixed jacket platforms at shallow water condition has been reported as a notable risk to the workability and reliability of the platform. Reduction in reservoir pressure, due to the extraction of hydrocarbon for an extended period of time, has caused the occurrence of seabed subsidence. Platform experiencing subsidence promotes reduction of air gaps, which eventually allows the waves to attack the bottom decks. The impact of the wave-in-deck generates additional loads to the structure and therefore increases the values of the moment arms. Higher moment arms trigger instability in terms of overturning, eventually decreases the reserve strength ratio (RSR) values of the structure. The mechanics of wave-in-decks, however, is still not well understood and have not been fully incorporated into the design codes and standards. Hence, it is necessary to revisit the current design codes and standards for platform design optimization. The aim of this study is to evaluate the effects of RSR due to wave-in-deck on four-legged jacket platforms in Malaysia. Base shear values with regards to calibration and modifications of wave characteristics were obtained using SESAM GeniE. Correspondingly, pushover analysis is conducted using USFOS to retrieve the RSR. The effects of the contributing factors i.e. the wave height, wave period and water depth with regards to the RSR and base shear values were analyzed and discussed. This research proposal is important in optimizing the design life of the existing and aging offshore structures. Outcomes of this research are expected to provide a proper evaluation of the wave-in-deck mechanics and in return contribute to the current mitigation strategies in managing the issue.
Damage Assessment and Repair for Older Brick Buildings
The experience of engineers and architects practicing today is typically limited to current building code requirements and modern construction methods and materials. However, many cities have a mix of new and old buildings with many buildings constructed over one hundred years ago when building codes and construction methods were much different. When a brick building sustains damage, a structural engineer is often hired to determine the cause of damage as well as determine necessary repairs. Forensic studies of dozens of brick buildings show an appreciation of historical building methods and materials is needed to correctly identify the cause of damage and design an appropriate repair. Damage on an older, brick building can be mistakenly attributed to storms or seismic events when the real source of the damage is deficient original construction. Assessing and remediating damaged brickwork on older brick buildings requires an understanding of the original construction, an understanding of older repair methods, and, an understanding of current building code requirements.
Influence of Alccofine on Semi-Light Weight Concrete under Accelerated Curing and Conventional Curing Regimes
This paper deals with the performance of semi-light weight concrete, prepared by using wood ash pellets as coarse aggregates which were improved by partial replacement of cement with Alccofine. Wood ash is a tamarind bark combustion product composed of fine particles that falls in the bottom of the modern rice mill dryers. Alccofine is a mineral admixture which contains high glass content obtained through the process of controlled granulation. These cementitious materials are much finer than cement and carries its own pozzolanic property. Therefore, cement could be replaced by Alccofine as 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, and 70% to enhance the strength and durability properties of concrete. High Range Water reducing admixtures (HRWA) was used in these mixes which were dosed up to 1.5% weight of the total cementitious materials content. It also develops the weaker transition zone into more impermeable layer. Specimens were subjected to accelerated curing method as well as conventional curing method. Experimental results were compared and reported that a maximum 28th day compressive strength of 32.6 MPa has achieved at 30% replacement level with a density of 2200 kg/m³ in conventional curing while in accelerated curing, the maximum compressive strength has achieved at 40% replacement level. Rapid chloride penetration test output results of conventional curing method for 0% and 70% gives 3296.7 and 545.6 coulombs.
Finite Element Analysis of Steel-Concrete Composite Structures considering Bond-Slip Effect
A numerical model considering slip behavior of steel-concrete composite structure is introduced. This model is based on a linear bond stress-slip relation along the interface. Single node was considered at the interface of steel and concrete member in finite element analysis, and it improves analytical problems of model that takes double nodes at the interface by adopting spring elements to simulate the partial interaction. The slip behavior is simulated by modifying material properties of steel element contacting concrete according to the derived formulation. Decreased elastic modulus simulates the slip occurrence at the interface and decreased yield strength simulates drop in load capacity of the structure. The model is verified by comparing numerical analysis applying this model with experimental studies. Acknowledgment—This research was supported by a grant(13SCIPA01) from Smart Civil Infrastructure Research Program funded by Ministry of Land, Infrastructure and Transport(MOLIT) of Korea government and Korea Agency for Infrastructure Technology Advancement(KAIA) and financially supported by Korea Ministry of Land, Infrastructure and Transport(MOLIT) as U-City Master and Doctor Course Grant Program.
Modelling of Factors Affecting Bond Strength of Fibre Reinforced Polymers Externally Bonded to Timber and Concrete
In recent years, fibre reinforced polymers as applications of strengthening materials have received significant attention by civil engineers and environmentalists because of their excellent characteristics. Currently, these composites have become a mainstream technology for strengthening of infrastructures such as steel, concrete and more recently, timber and masonry structures. However, debonding is identified as the main problem which limits the full utilisation of the FRP material. In this paper, a preliminary analysis of factors affecting bond strength of FRP-to-concrete and timber bonded interface has been conducted. A novel theoretical method through regression analysis has been established to evaluate these factors. Results of proposed model are then assessed with results of pull-out tests, and satisfactory comparisons are achieved when measured failure loads compared against of predicted loads.
Cable Supported Facades under Blast Loading
Structural Glass Facades (SGFs) are used in most modern buildings due to their unique architectural aesthetics and energy performance. Cable Supported Facades (CSFs), both cable truss facades and cable net facades are gaining in popularity among the SGFs due to their increased transparency and minimal and highly flexible supporting structures. With the increased threat of terrorist attacks around the world, designers are concerned in making these facades blast resistant for credible blast events as impact of flying glass fragments has been the primary cause of injury during a blast event. Early approaches to designing blast resistant facades identified Laminated Glass (LG) panels as the preferred glass type due to their high energy absorption capacity and the specific interlayer properties. Several design standards were developed for blast resistant design. However, these standards are conservative and less applicable to today’s innovative structural glass façade systems. There has been some recent research on developing methods to design CSFs subjected to blast events. However, most of these studies suggested the use of external devices to mitigate the adverse effects of a blast event on the façade. These developed systems have limitations in application and installation of external devices significantly increases the cost of the façade and the difficulty in construction. There is hence a need to develop a practical CSF system with a blast resisting capacity under credible blast loads. With this in mind, a research project has been undertaken to develop a CSF system without installing any expensive external devices, instead varying the system parameters to create a cost effective and efficient system for a credible blast event. The applications of systems and technology used in innovative wind resisting CSFs are considered for blast applications. Towards this end, this paper investigates the behavior of CSFs under blast loading by a numerical analyses carried out with the finite element models developed using LS DYNA simulation software. Modular units of cable net facades are created in FE code and modelling techniques are validated with existing numerical and experimental data. The behavior of facade elements under a pressure acting on the front face due to unconfined surface burst is evaluated. The material models, element formulations and connections and contact types for the different components of the cable supported façade are confirmed in an iterative manner by investigating different combinations. Finally, a comprehensive numerical model that can be used to analyze the global behavior of a CSF under credible blast pressure is proposed. This model can be used to study the influence of the controlling parameters and thereby to develop an optimized blast resistant CSF.
Computational Modeling of Perpendicular to Grain Stress in a Non-Standard Glulam Beam
This paper focuses on the analysis of tensile stresses perpendicular to the grain in simply supported beams with different geometry made of glued laminated timber. Two types of beams are considered: standard double-tapered beams described in Eurocode 5 and non-standard glulam beams with a flattened apex. The beams are analyzed using two methodology approaches: a code design verification method and a finite element method (FEM) in terms of the linear theory of elasticity with plane stress assumption. The performed analyses proved that both methodologies lead to consistent results in case of standard glulam beams and therefore, the FEM can be used in case of non-standard structures, which are not included in Eurocode 5. Moreover, the FE analysis of the glulam beam with a flattened apex showed that it can be treated as a structure with two apex zones.
An Overview of Electronic Waste as Aggregate in Concrete
Rapid growth of world population and widespread urbanization has remarkably increased the development of the construction industry which caused a huge demand for sand and gravels. Environmental problems occur when the rate of extraction of sand, gravels, and other materials exceeds the rate of generation of natural resources. Therefore, an alternative source is essential to replace the materials used in concrete. Nowadays electronic products have become an integral part of daily life which provides with more comfort, security, easy exchange of information. These electronic wastes (E-Wastes) materials have serious human health concerns and require extreme care in its disposal to avoid adverse impacts. Disposal or dumping of these electronic wastes also causes major issues because it is highly complex to handle and often contains highly toxic chemicals such as lead, cadmium, mercury, beryllium, Brominates Flame Retardants (BFRs), Poly Vinyl Chloride (PVC) and phosphorus compounds. These E-Wastes can be incorporated in concrete to make sustainable environment. This paper deals with the composition, preparation of E-Waste material and its properties. This paper also provides a detailed literature review on the behavior of concrete with incorporation of E-Wastes. Many research shows a strong possibility of using E-waste as a substitute of aggregates in concrete. As a result of this tends to decrease the use natural aggregates in concrete and a prime importance where substitute of aggregates can be explored.
Effect of Water-Cement Ratio on the Compressive Strength of Sandcrete Block Blended with Sawdust Ash
The problem of managing agricultural and industrial wastes has become a challenge in recent time. Therefore, research in the area of minimizing waste accumulation through reclamation and recycling has been ignited considering their aesthetic and ecological problems caused by the improper disposal. Areas of research aimed at reducing waste include the use of sawdust ash, rice-husk ash and groundnut-husk ash to partially replace cement in the production of concrete or sandcrete blocks. The use of sawdust ash (SDA) as replacement of cement in the production of sandcrete blocks was investigated. The aim was to determine the percentage of SDA and water-cement ratio that would give the 28-day maximum strength. The sawdust ash was used to partially replace Ordinary Portland Cement (OPC) in various proportions (0%, 5% 10%, 15% and 20%).Cubes were produced using mix ratio 1:4 and water-cement ratios of 0.40, 0.50, 0.55 and 0.60.The cubes were tested at the ages of 7, 14, 21 and 28 days for each proportion of OPC/SDA and water cement ratio. The results indicated that compressive strength of blocks at 28 days was 3.80N/mm2 and 3.50N/mm2 for 5% SDA at water-cement ratios 0.55 and 0.60 respectively. The compressive strength for 10% SDA was 2.87N/mm2 and 3.10N/mm2 at water-cement ratios 0.55 and 0.60 respectively. The 5% and 10% percentage replacements have compressive greater than the required strength of 2.00N/mm2 specified by the Nigerian National Building Code (2006) for non-load bearing walls. By these results sandcrete blocks with up to 10% SDA replacement at water-cement ratios 0.55 and 0.60 can be used for non-load bearing walls.
Studying the Structural Behaviour of RC Beams with Circular Openings of Different Sizes and Locations Using FE Method
<p class="Abstract">This paper aims to investigate the structural behaviour of RC beams with circular openings of different sizes and locations modelled using ABAQUS FEM software. Seven RC beams with the dimensions of 1200 mm&times;150 mm&times;150 mm were tested under three-point loading. Group A consists of three RC beams incorporating circular openings with diameters of 40 mm, 55 mm and 65 mm in the shear zone. However, Group B consists of three RC beams incorporating circular openings with diameters of 40 mm, 55 mm and 65 mm in the flexural zone. The final RC beam did not have any openings, to provide a control beam for comparison. The results show that increasing the diameter of the openings increases the maximum deflection and the ultimate failure load decreases relative to the control beam. In the shear zone, the presence of the openings caused an increase in the maximum deflection ranging between 4% and 22% and a decrease in the ultimate failure load of between 26% and 36% compared to the control beam. However, the presence of the openings in the flexural zone caused an increase in the maximum deflection of between 1.5% and 19.7% and a decrease in the ultimate failure load of between 6% and 13% relative to the control beam. In this study, the optimum location for placing circular openings was found to be in the flexural zone of the beam with a diameter of less than 30% of the depth of the beam.
Impact of Joule Heating on the Electrical Conduction Behavior of Carbon Composite Laminates under Simulated Lightning Strike
Increasing demands for high strength and lightweight materials in aircraft industry prompted the wide use of carbon composites in recent decades. Carbon composite laminates used on aircraft structures are subject to lightning strikes. Unlike its metal/alloy counterparts, carbon fiber reinforced composites demonstrate smaller electrical conductivity, yielding more severe damages due to Joule heating. The anisotropic nature of composite laminates makes the electrical and thermal conduction within carbon composite laminates even more complicated. Good understanding of the electrical conduction behavior of carbon composites is the key to effective lightning protection design. The goal of this study is to numerically and experimentally investigate the impact of ultra-high temperature induced by simulated lightning strike on the electrical conduction of carbon composites. A lightning simulator is designed to apply standard lightning current waveform to composite laminates. Multiple carbon composite laminates made from IM7 and AS4 carbon fiber are tested and the transient resistance data is recorded. A microstructure based resistor network model is developed to describe the electrical and thermal conduction behavior, with consideration of temperature dependent material properties. Material degradations such as thermal and electrical breakdown are also modeled to include the effect of high current and high temperature induced by lightning strikes. Good match between the simulation results and experimental data indicates that the developed model captures the major conduction mechanisms. A parametric study is then conducted using the validated model to investigate the effect of system parameters such as fiber volume fraction, inter-ply interface quality, and lightning current waveforms.
Model-Based Fault Diagnosis in Carbon Fiber Reinforced Composites Using Particle Filtering
Carbon fiber reinforced composites (CFRP) used as aircraft structure are subject to lightning strike, putting structural integrity under risk. Indirect damage may occur after a lightning strike where the internal structure can be damaged due to excessive heat induced by lightning current, while the surface of the structures remains intact. Three damage modes may be observed after a lightning strike: fiber breakage, inter-ply delamination and intra-ply cracks. The assessment of internal damage states in composite is challenging due to complicated microstructure, inherent uncertainties, and existence of multiple damage modes. In this work, a model based approach is adopted to diagnose faults in carbon composites after lighting strikes. A resistor network model is implemented to relate the overall electrical and thermal conduction behavior under simulated lightning current waveform to the intrinsic temperature dependent material properties, microstructure and degradation of materials. A fault detection and identification (FDI) module utilizes the physics based model and a particle filtering algorithm to identify damage mode as well as calculate the probability of structural failure. Extensive simulation results are provided to substantiate the proposed fault diagnosis methodology with both single fault and multiple faults cases. The approach is also demonstrated on transient resistance data collected from a IM7/Epoxy laminate under simulated lightning strike.
Seismic Performance of Benchmark Building Installed with Semi-Active Dampers
The seismic performance of 20-storey benchmark building with semi-active dampers is investigated under various earthquake ground motions. The Semi-Active Variable Friction Dampers (SAVFD) and Magnetorheological Dampers (MR) are used in this study. A recently proposed predictive control algorithm is employed for SAVFD and a simple mechanical model based on a Bouc–Wen element with clipped optimal control algorithm is employed for MR damper. A parametric study is carried out to ascertain the optimum parameters of the semi-active controllers, which yields the minimum performance indices of controlled benchmark building. The effectiveness of dampers is studied in terms of the reduction in structural responses and performance criteria. To minimize the cost of the dampers, the optimal location of the damper, rather than providing the dampers at all floors, is also investigated. The semi-active dampers installed in benchmark building effectively reduces the earthquake-induced responses. Lesser number of dampers at appropriate locations also provides comparable response of benchmark building, thereby reducing cost of dampers significantly. The effectiveness of two semi-active devices in mitigating seismic responses is cross compared. Among two semi-active devices majority of the performance criteria of MR dampers are lower than SAVFD installed with benchmark building. Thus the performance of the MR dampers is far better than SAVFD in reducing displacement, drift, acceleration and base shear of mid to high-rise building against seismic forces.
Seismic Assessment of Flat Slab and Conventional Slab System for Irregular Building Equipped with Shear Wall
Particular instability of structural building under lateral load (e.g earthquake) will rise due to irregularity in vertical and horizontal direction as stated in SNI 03-1762-2012. The conventional slab has been considered for its less contribution in increasing the stability of the structure, except special slab system such as flat slab turned into account. In this paper, the analysis of flat slab system at Sequis Tower located in South Jakarta will be assessed its performance under earthquake. It consists of 6 floors of the basement where the flat slab system is applied. The flat slab system will be the main focus in this paper to be compared for its performance with conventional slab system under earthquake. Regarding the floor plan of Sequis Tower basement, re-entrant corner signed for this building is 43.21% which exceeded the allowable re-entrant corner is 15% as stated in ASCE 7-05 Based on that, the horizontal irregularity will be another concern for analysis, otherwise vertical irregularity does not exist for this building. Flat slab system is a system where the slabs use drop panel with shear head as their support instead of using beams. Major advantages of flat slab application are decreasing dead load of structure, removing beams so that the clear height can be maximized, and providing lateral resistance due to lateral load. Whilst, deflection at middle strip and punching shear are problems to be detail considered. Torsion usually appears when the structural member under flexure such as beam or column dimension is improper in ratio. Considering flat slab as alternative slab system will keep the collapse due to torsion down. Common seismic load resisting system applied in the building is a shear wall. Installation of shear wall will keep the structural system stronger and stiffer affecting in reduced displacement under earthquake. Eccentricity of shear wall location of this building resolved the instability due to horizontal irregularity so that the earthquake load can be absorbed. Performing linear dynamic analysis such as response spectrum and time history analysis due to earthquake load is suitable as the irregularity arise so that the performance of structure can be significantly observed. Utilization of response spectrum data for South Jakarta which PGA 0.389g is basic for the earthquake load idealization to be involved in several load combinations stated on SNI 03-1726-2012. The analysis will result in some basic seismic parameters such as period, displacement, and base shear of the system; besides the internal forces of the critical member will be presented. Predicted period of a structure under earthquake load is 0.45 second, but as different slab system applied in the analysis then the period will show a different value. Flat slab system will probably result in better performance for the displacement parameter compare to conventional slab system due to higher contribution of stiffness to the whole system of the building. In line with displacement, the deflection of the slab will result smaller for flat slab than a conventional slab. Henceforth, shear wall will be effective to strengthen the conventional slab system than flat slab system.
Performance Evaluation of Composite Beam under Uniform Corrosion
Composite member (concrete and steel) has been widely advanced for structural utilization due to its best performance in resisting load, reducing the total weight of the structure, increasing stiffness, and other available advantages. On the other hand, the environment load such as corrosion (e.g. chloride ingress) creates significant time-dependent degradation for steel. Analysis performed in this paper is mainly considered uniform corrosion for evaluating the composite beam without examining the pit corrosion as the initial corrosion formed. Corrosion level in terms of weight loss is modified in yield stress and modulus elasticity of steel. Those two mechanical properties are utilized in this paper for observing the stresses due to corrosion attacked. As corrosion level increases, the effective width of the composite beam in the concrete section will be wider. The position of a neutral axis of composite section will indicate the composite action due to corrosion of composite beam so that numerous shear connectors provided must be reconsidered. Flexure capacity quantification provides stresses, and shear capacity calculation derives connectors needed in overcoming the shear problem for composite beam under corrosion. A model of simply supported composite beam examined in this paper under uniform corrosion where the stresses as the focus of the evaluation. Principal stress at the first stage of composite construction decline as the corrosion level incline, parallel for the second stage stress analysis where the tension region held by the steel undergoes lower capacity due to corrosion. Total stresses of the composite section for steel to be born significantly decreases particularly in the outermost fiber of tension side. Whereas, the available compression side is smaller as the corrosion level increases so that the stress occurs on the compression side shows reduction as well. As a conclusion, the increment of corrosion level will degrade both compression and tension side of stresses.
Design of an Automatic Saw Cutting Machine for Wood and Aluminum
The uses of wood in furniture, building, bridges and aluminum in transportation and construction, make aluminum and forest economy a prominent matter in North America. Machines available to date to cut the aforementioned materials are mostly industry oriented with complex structure and operations which require special training and skill. Furthermore, requirements such as pneumatics, 3-phase supply are associated with cost, maintenance, and safety hazards. Power saws are very useful tools used to cut and shape materials; however, they can cause serious hand injuries. Operator’s hands in table saw are vulnerable as they are used to guide pieces into the saw. Apart from hands, saw operator is also prone to material being kicked back out of the saw or sustain eye or respiratory injuries due to rapidly flying sawdust and other debris. In this paper, design of an automatic saw cutting machine has been proposed to ensure safety, portability, usage at domestic level and capability to cut both aluminum and wood. This paper demonstrates detailed Mechanical design in SOLIDWORKS and Control Systems using Programmable Logic Controller (PLC), based on the aforementioned design objectives.
Forced Vibration of a Planar Curved Beam on Pasternak Foundation
The objective of this study is to investigate the forced vibration analysis of a planar curved beam lying on elastic foundation by using the mixed finite element method. The finite element formulation is based on the Timoshenko beam theory. In order to solve the problems in frequency domain, the element matrices of two nodded curvilinear elements are transformed into Laplace space. The results are transformed back to the time domain by the well-known numerical Modified Durbin’s transformation algorithm. First, the presented finite element formulation is verified through the forced vibration analysis of a planar curved Timoshenko beam resting on Winkler foundation and the finite element results are compared with the results available in the literature. Then, the forced vibration analysis of a planar curved beam resting on Winkler-Pasternak foundation is conducted.
The Effect of Transparent Oil Wood Stain on the Colour Stability of Spruce Wood during Weathering
Nowadays the use of wood, both indoors and outdoors, is constantly increasing. However wood is a natural organic material and in the exterior is subjected to a degradation process caused by abiotic factors (solar radiation, rain, moisture, wind, dust etc.). This process affects only surface layers of wood but neglecting some of the basic rules of wood protection leads to increased possibility of biological agents attack and thereby influences a function of the wood element. The process of wood degradation can be decreased by proper surface treatment, especially in the case of less naturally durable wood species, as spruce. Modern coating systems are subjected to many requirements such as colour stability, hydrophobicity, low volatile organic compound (VOC) content, long service life or easy maintenance. The aim of this study is to evaluate the colour stability of spruce wood (Picea abies), as the basic parameter indicating the coating durability, treated with two layers of transparent natural oil wood stain and exposed to outdoor conditions. The test specimens were exposed for 2 years to natural weathering and 2000 hours to artificial weathering in UV-chamber. The colour parameters were measured before and during exposure to weathering by the spectrophotometer according to CIELab colour space. The comparison between untreated and treated wood and both testing procedures was carried out. The results showed a significant effect of coating on the colour stability of wood, as expected. Nevertheless, increasing colour changes of wood observed during the exposure to weathering differed according to applied testing procedure - natural and artificial.
Response of Solar Updraft Power Plants Incorporating Material Nonlinearity
Solar updraft power plants (SUPP) provide a great potential for green and environmentally friendly renewable power generation. An up to 1000 m high chimney represents one of the major parts of each SUPP, which consist of the main shell structure and the stiffening rings. Including the nonlinear material behavior in a simulation of the chimney is computationally a demanding task. However, allowing the formation of cracking in concrete leads to a more economical design of the structure. In this work, an FE model of a SUPP is presented incorporating the nonlinear material behavior. The effect of wind loading intensity on the structural response is explored. Furthermore, the influence of the stiffness of the ring beams on the global behavior is as well investigated. The obtained results indicate that the minimum reinforcement is capable of carrying the tensile stresses provided that the ring beams are rather stiff.
Submodeling of Mega-Shell Reinforced Concrete Solar Chimneys
Solar updraft power plants (SUPPs) made from reinforced concrete (RC) are an innovative technology to generate solar electricity. An up to 1000 m high chimney represents the major part of each SUPP ensuring the updraft of the warmed air from the ground. Numerical simulation of nonlinear behavior of such large mega shell concrete structures is a challenging task, and computationally expensive. A general finite element approach to simulate reinforced concrete bearing behavior is presented and verified on a simply supported beam, as well as the technique of submodeling. The verified numerical approach is extended and consecutively transferred to a more complex chimney structure of a SUPP. The obtained results proved the reliability of submodeling technique in analyzing critical regions of simple and complex mega concrete structures with high accuracy and dramatic decrease in the computation time.
Testing of the Decreasing Bond Strength of Polyvinyl Acetate Adhesive by Low Temperatures
When using wood products bonded by polyvinyl acetate, glues such as windows are the most limiting element of degradation of the glued joint due to weather changes. In addition to moisture and high temperatures, the joint may damage the low temperature below freezing point, where dimensional changes in the material and distortion of the adhesive film occur. During the experiments, the joints were exposed to several degrees of sub-zero temperatures from 0 °C to -40 °C and then to compare how the decreasing temperature affects the strength of the joint. The experiment was performed on wood beech samples (Fagus sylvatica), bonded with PVAc with D3 resistance and the shear strength of bond was measured. The glued and treated samples were tested on a laboratory testing machine, recording the strength of the joint. The statistical results have given us information that the strength of the joint gradually decreases with decreasing temperature, but a noticeable and statistically significant change is achieved only at very low temperatures.
Finite Element Analysis of the Ordinary Reinforced Concrete Bridge Piers
Most of the concrete bridges in Nepal constructed during 90's and before are made up of low strength ordinary concrete which might be one of the reasons for damage in higher magnitude earthquake. Those bridges were designed by the outdated bridge codes which might not account the large seismic loads. This research investigates the seismic vulnerability of the existing single column ordinary concrete bridge pier by finite element modeling, using the software Seismostruct. The existing bridge pier capacity has been assessed using nonlinear pushover analysis and performance is compared after retrofitting those pier models with CFRP. Furthermore, the seismic evaluation was made by conducting cyclic loading test at different drift percentage. The performance analysis of bridge pier by nonlinear pushover analysis is further validated by energy dissipation phenomenon measured from the hysteric loop for each model of ordinary concrete piers.