Focus Styling and Analysis by SPACE GASS and ETABS - Assignment Example

Core Modeling and Analysis by SPACE GASS and ETABS Presented by Name Presented To Lecturer Institution Topic Date Core Modeling and Analysis by SPACE GASS and ETABS Introduction: The progressive collapse of the World Trade Center towers has generated a worldwide concern of the risks of progressive collapse in multi-story buildings. The prevention of progressive collapse lies primary in the proper and effective analysis of the structures having high potential to progressivity (Rittenhouse and Smilowitz, 2004). Different analysis methods are presented herein such as linear elastic static, non-linear static, linear elastic dynamic and non-linear dynamic analysis. To minimize the progressive collapse risks, the structural system of the building should be able to tolerate the removal of one or more structural members and redistribute their load on the surrounding members, so that disproportionate collapse would not take place. In this paper, a building has been analyzed by use of two Softwares, ETABS and SPACE GASS. This paper also discusses the use of Softwares in performing building analysis. Structural loads: The objective of every structural or civil design is basically to come up with a structure that is strong against the various loads acting on it. There are various loads that act on the building and these falls into three broad categories; dead loads, imposed loads and environmental loads. Dead load comprises of all the weight of the construction including the walls, the roof, partitions and any other permanent construction in the building. Imposed load, also called live loading comprises of the load resulting from the usage of the building. This includes the weight of the people living in the building and all other non permanent facilities placed in the building. Environmental loading on the other hand results from environmental factors such as wind, earthquakes and snow (Applied Technology Council (ATC), 1996). Wind loads for instance, causes the various structural elements such as the core and the columns to deflect and if wind load exceeds the limit of the structural elements, failure and collapse arises. It is dynamic in nature and among the three categories, this appears to be the most complicated type of load to design and analyses the building for. This complexity arises as a result of lack of a definite behavior of any of them. Take wind load for instance, its intensity will depend on the area of exposure and more so on the speed of the wind. It is quite impossible to predict for a certain speed although engineers design based on the history of the place regarding the wind. Seismic loads are also very difficult to determine since they occur at different magnitude (Willford, Whittaker and Klemencic, 2008). Modeling is thus of importance in building design in order to analyze the behavior of the building under different conditions, that is wind intensity. It is also expected that there will be a combination of all the above categories during the life of the structure, implying that comprehensive and accurate analysis is required during the design phase of the structure to ensure that the building remains safe for its intended use. The complexity of the loads arising from the combination of the various types of loads demands a more comprehensive and complex analysis of the various structural elements. Methods of building core analysis: According to Vishay Systems (2006), there are two methods of analyzing a building structure, linear elastic and linear inelastic analysis. Simiu and Scanlan (1996 further points out that building analysis can be linear elastic static, non-linear static analysis and non-linear dynamic analysis. Basically, linear elastic static analysis is the simpler of the two, (Gupta and Ajaya, 1993), since it involves static removal of the major structural elements. The procedure is this based on approximation. Non-linear static analysis takes into considerations the non-linear properties and behaviors of the structural element, which is the main advantage of the method. This method is very helpful in evaluating the ductility property of the structural element. Finally, non-linear dynamic analysis is considered to be the most accurate analysis method since it excellently expresses the behavior of the structure through removal of a single or a number of the structural elements. Though complicated and time consuming method, Simiu and Scanlan (1996) point out that it is more realistic due to its ability to account for the various properties such as the yielding, damping and cracking. When conducting an analysis for multi-storey buildings, Marjanishvili (2004) indicates that it is good practice to begin with the simple analysis methods such as the linear elastic static method. This sometimes may be sufficient to conduct the analysis but if the design demands further analysis, one can seek the help of more complicated and accurate analysis methods such as the non-linear elastic static method and/or the non-linear dynamic analysis method. Reasons for using Softwares in building analysis: Vishay Systems (2006) classifies dynamic analysis as either linear elastic or linear inelastic. In Reinforced Concrete (RC), the linear elastic analysis is well established with various 3D analysis packages being available. These include ETABS and SPACE GAS among others. Prior to the development of these packages, engineers used to carry out hand calculations in order to analyze the various structural elements of the building, a procedure that often proved tedious due to the complexity of the building as well as the numerous structural elements involved in the structure. As an example, consider performing an analysis for a 12 storey building. This will of course be tedious and cumbersome as compared to analyzing a two storey building. For a long time, Finite Element Modeling (FEM) has found its application in Reinforced Concrete (RC) structures. It has been a very useful and powerful engineering tool in the analysis. With the introduction of computers and Softwares, the use of Softwares such as ETABS and SPACE GASS has found wider application in the analysis procedure. This has specifically been so for reinforced concrete due to its behavioral complexity (Smith and Coull, 1991). In order to stress on the reasons behind the use of building analysis software, it is important to highlight some of the benefits realized through use of software. Efficiency: Various Softwares are programmed with building codes for the various geographic regions. These Softwares incorporate such regulations into the building plans and therefore making sure that there are no possibilities of inadvertently omitting the regulations. The consequences of such omissions include structural failure that could lead into deaths and/or heavy fines, structural errors and wastage of time and money among many others. By incorporating a myriad of building codes in single software, it is thus possible to generate the set of codes for every geographic location so that the designer does not overlook any of them. Consequently, this eliminates possible revisions thereby enabling the contractors to stick to their schedule and budget. Flexibility: Use of structural analysis Softwares finds great importance at the initial stages of a building construction, planning process. It is important to note that in many instances, the conceptual plan does not end up being the used plan in the construction and changes are usually made here and there until the building plan pleases the owner. Softwares facilitate last minute alterations in the load and/or design of the building to be made quickly and accurately incorporate them into the new plans without the risk of having design flaws in the building. Comparing this to hand calculations, making such alterations not only demands enormous efforts and time incorporating them into the new plans but also multiple errors are possible which can sometimes be fatal. Flaws: It is possible to nearly eliminate all the errors involved in the design and construction of the building through use of building analysis Softwares. The Softwares facilitate efficient determination of maximum allowable loads, the number and spacing of the various structural elements and their sizes. When this efficient analysis is combined with precise and careful construction of the building, the results are a reliable, safe and stable building. Speed: Building analysis Softwares are timesaving options for professional engineers, architects and contractors. With the help of these Softwares, it is possible for such professionals to double check their calculations and designs. Moreover, it is possible for them to carry out complicated analysis in a very short time and yet not compromise on the accuracy and safety. Since the Softwares contain building codes within them, crucial design values such as load limits and deflections are automatically generated thereby saving time for other building works. Otherwise, the professionals would have to calculate each value for every component, thereby spending a lot of time on design. Peace of mind: To sum it all, building analysis Softwares relieve the engineers, architects and contractors the pressure involved in building constructions. It is very eminent that a building project, no matter how small it is, requires the various professionals involved to have their fingers crossed throughout the project to ensure everything runs out smoothly. At the initial stages for instance, engineers must pay keen attention to the calculations and analysis otherwise the whole project turns out to be a failure. Building analysis Softwares give engineers a peace of mind in that they rest assured that the construction values arising from the analysis are not erroneous and thereby considering that construction runs out smoothly, the safety of the building is never compromised. The above section has concentrated on the use of Softwares in performing building analysis. Modeling too is accomplished through the use of Softwares. With time experimental modeling has been pushed out of use by computer based modeling, employing Softwares in the modeling process. It is important to note the limitations posed by experimental modeling in order to set up a concrete reason behind the use computer-based modeling. Feldmann (n.d) points out that the main disadvantage of experimental modeling or otherwise advantage of software modeling lies on the cost and time. This is especially the case where the modeling involves a multi-storey building whereby it becomes complicated and tedious to make a model with which to experiment the decision in consideration. This will of course involve a lot of time and money making the model only to destroy it during the experimentation procedure. Even more worse is the situation whereby changes are made in the design of and plan of the building, demanding another model (Kwatra and Naveen, 2000). This is usually not the case when using Softwares such as ETABS and SPACE GASS in the modeling of the various structural elements such as the core. Modeling using such Softwares is simple and speedy especially when changes are made in the plan of the building. References Applied Technology Council (ATC), (1996). Seismic Evaluation and Retrofit of Concrete Buildings, ATC-40. Feldmann, B, (n.d). Designing for Wind. Retrieved from: http://www.alpeng.com/index.php?option=com_content&view=article&id=74&Itemid=9 Gupta & Ajaya (1993). Guidelines for Design of Low-Rise Buildings Subjected to Lateral Forces. Boca Raton: CRC Press. p. 49. Kwatra & Naveen, (2000) “Experimental Studies and ANN Modelling of Wind Loads on Low Buildings”. Ph.D. Thesis, Civil Engineering Department, University of Roorkee (Now Indian Institute of Technology Roorkee). Marjanishvili, S. M., (2004). ‘Progressive Analysis Procedure for Progressive Collapse’, Journal of Performance of Constructed Facilities-ASCE, p. 79-85. Rittenhouse, T, & Smilowitz, R., (2004). Building Protection on Main Street, USA, Design- Build Dateline Simiu, E & Scanlan, H, (1996). Wind effects on structure – Fundamentals and Applications to Design, – third edition. Book published by John Willey & Sons Inc. New York. Smith, B, S, & Coull, A, (1991). Tall Building Structures, John Wiley, New York, p. 537. Vishay Systems, (2006). Earthquake and Wind Load Design Handbook, Vishay Intertechnology, Inc. Willford, M, Whittaker, A & Klemencic, R, (2008). Recommendations for the Seismic Design of High-rise Buildings. Council on Tall Buildings and Urban Habitat, Retrieved from: http://www.arup.com/_assets/_download/853FAEBD-19BB-316E- 4059E101531D20C1.pdf Read More

It is also expected that there will be a combination of all the above categories during the life of the structure, implying that comprehensive and accurate analysis is required during the design phase of the structure to ensure that the building remains safe for its intended use. The complexity of the loads arising from the combination of the various types of loads demands a more comprehensive and complex analysis of the various structural elements. Methods of building core analysis: According to Vishay Systems (2006), there are two methods of analyzing a building structure, linear elastic and linear inelastic analysis.

Simiu and Scanlan (1996 further points out that building analysis can be linear elastic static, non-linear static analysis and non-linear dynamic analysis. Basically, linear elastic static analysis is the simpler of the two, (Gupta and Ajaya, 1993), since it involves static removal of the major structural elements. The procedure is this based on approximation. Non-linear static analysis takes into considerations the non-linear properties and behaviors of the structural element, which is the main advantage of the method.

This method is very helpful in evaluating the ductility property of the structural element. Finally, non-linear dynamic analysis is considered to be the most accurate analysis method since it excellently expresses the behavior of the structure through removal of a single or a number of the structural elements. Though complicated and time consuming method, Simiu and Scanlan (1996) point out that it is more realistic due to its ability to account for the various properties such as the yielding, damping and cracking.

When conducting an analysis for multi-storey buildings, Marjanishvili (2004) indicates that it is good practice to begin with the simple analysis methods such as the linear elastic static method. This sometimes may be sufficient to conduct the analysis but if the design demands further analysis, one can seek the help of more complicated and accurate analysis methods such as the non-linear elastic static method and/or the non-linear dynamic analysis method. Reasons for using Softwares in building analysis: Vishay Systems (2006) classifies dynamic analysis as either linear elastic or linear inelastic.

In Reinforced Concrete (RC), the linear elastic analysis is well established with various 3D analysis packages being available. These include ETABS and SPACE GAS among others. Prior to the development of these packages, engineers used to carry out hand calculations in order to analyze the various structural elements of the building, a procedure that often proved tedious due to the complexity of the building as well as the numerous structural elements involved in the structure. As an example, consider performing an analysis for a 12 storey building.

This will of course be tedious and cumbersome as compared to analyzing a two storey building. For a long time, Finite Element Modeling (FEM) has found its application in Reinforced Concrete (RC) structures. It has been a very useful and powerful engineering tool in the analysis. With the introduction of computers and Softwares, the use of Softwares such as ETABS and SPACE GASS has found wider application in the analysis procedure. This has specifically been so for reinforced concrete due to its behavioral complexity (Smith and Coull, 1991).

In order to stress on the reasons behind the use of building analysis software, it is important to highlight some of the benefits realized through use of software. Efficiency: Various Softwares are programmed with building codes for the various geographic regions. These Softwares incorporate such regulations into the building plans and therefore making sure that there are no possibilities of inadvertently omitting the regulations. The consequences of such omissions include structural failure that could lead into deaths and/or heavy fines, structural errors and wastage of time and money among many others.

By incorporating a myriad of building codes in single software, it is thus possible to generate the set of codes for every geographic location so that the designer does not overlook any of them.

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