Structural Engineering

Permanent URI for this collection

http://etd.aau.edu.et/handle/12345678/138

Browse

Now showing 1 - 20 of 287

Prefabrication of Structural Elements: A CaseStudy
(Addis Ababa University, 1998-06) Bulto, Gutema; Adamu, Asnake (PhD)
The back-log of housing units in Ethiopia was so immense that all efforts made by the Government and inhabitants could not wipe out the shortage of housing in the early 1980s. To promote the building industry and to alleviate the housing shortage prefabrication technology was introduced. The Prefabricated Building Parts Production Enterprise (PBPPE), which makes use of IMS precast concrete system (a patent of the Institute for Testing Materials for prestressed concrete), was established in 1984 with a technical assistance from the former Yugoslavia. The objectives of the enterprise are to promote the building industry through mass production of precast concrete elements, to alleviate the shortage of housing and to reduce the construction cost. Since its foundation the enterprise has carried out the production of building parts and the erection of residential and public buildings. The IMS framework of precast concrete constitutes one of the widely applied industrialized building technology, because it provides for cost-effective mass production of buildings. In the research work, a review of the experiences of other countries and a comprehensive literature survey on prefabrication was conducted. Then, the Ethiopian experience in the use of precast concrete especially the IMS system was assessed. The use and development of the IMS precast system were found slow and far below our expectation. To identify the sole cause that contributed to this effect, a sample survey was carried out and from the analysis of the survey conclusions were drawn. After a thorough evaluation of the existing modules, to demonstrate the flexibility and the possible modification to the existing modules of the IMS system, a proposal was made for a G+1 dwelling building. Comparative analysis between the existing and the proposed modules was made and recommendations were forwarded. The study also considers the application of precast concrete to other special structures. Finally, conclusions and recommendations were forwarded to promote the development of the IMS system. Essentially, great efforts should be done to disseminate technical information through brochures, manuals, design guidelines and advertisement to support the industrialization of the building industry in Ethiopia.
Evaluation of Approximate Methods for the Design of Biaxiall Y Loaded Reinforced Concrete Columns
(Addis Ababa University, 1999-05) Desta, Tefera; Chane, Bayou(PhD)
The ultimate capacity of reinforced concrete sections under normal force and biaxial bending moments can be represented by a three dimensional interaction surface in terms of the normal force and biaxial moments. The surface can be conveniently represented by a family of curves either on a plane of constant normal force relating the two moment components or as interaction diagram on a plane of constant angle relating the normal force and the resultant of the two moment components. However, the curves can not be described by exact and closed form mathematical expressions due to a wide variety of parameters involved in the determination of ultimate biaxial moment capacity of crosssections with normal force. Thus the systematic generation of such curves to be used for design involves obtaining sufficient number of suitable points by iteration which normally requires use of computer programs. In the absence of such facilities, the use of approximate methods becomes mandatory. There are different approximate methods adopted in different codes for the design of biaxially loaded reinforced concrete columns and the purpose of this thesis work is to assess and evaluate the proximity of some of these approximate methods with the exact solution. The approximate methods evaluated include those recommended by EBCS-2 [1), CPllO [2,3) and ACI [4,5).
Computerized AnalysisofFrames with Non-Prismatic Members
(Addis Ababa University, 2002-04) Takele, Samson; Taye, Shifferaw(PhD)
Optimal Design for Prestressed Concrete Box Girder Brigde
(Addis Ababa University, 2002-06) HaileMichael, Samuel; Taye, Shifferaw(PhD)
This thesis concerned with optimization of simply supported prestresed concrete box girder bridge. Usually, the design of prestressed concrete bridges is done based on codes on prestressed concrete bridges. The code requirement is generally concerned with the safety of the structure in its lifetime. Apart from satisfying the code requirement, the design should be economically chosen. For a given condition, there might be a large number of alternatives that satisfy the requirements imposed by codes. But the designer must be in position to choose the one, which is optimal against certain measure of optimality. Therefore, the designers have to do some optimization to arrive at such design. The objective of this thesis work is to show how the optimal design of a prestressed concrete boxgirder bridge can be obtained. It will established a general relationship among different design variables at optimum and will recommend a simple procedure to identify an the optimum design. The presentation is divided in to six chapters. In chapter one, a detail discussion on the theory of prestressed concrete is presented. Great emphasis is given for analysis of sections for flexure both in elastic and plastic ranges. It also explains the usual trends to be followed in the design of a pre stressed concrete section under service and over loads. In chapter two, application of pre stressed concrete on bridge is discussed. Conditions favoring pre stressed concrete application for such type of structural systems Chapter three discusses about optimization theory and general formulation of an optimization problem. Emphasis will be given numerical optimization theory and techniques. Chapter four deals with the methods used to solve an optimization problem. An extended complete coverage is given on linear programming and feasible direction methods, as they will be used later in chapter six to solve an optimal design problem for box-girder bridge. In chapter five, an optimal design problem is formulated for simply supported rectangular box-girder bridge based on AASHTO 96 Code. 2 In chapter six, the optimal design problem formulated in (chapter five) is solved for 40m span bridges using a Fortran program written for the method of Feasible Direction. The program is developed for this particular purpose. Concluding remark is also given The source code of developed program along with a flow chart outlining the program logic to this work is included in an appendix.
A Study on The Suitability of Local Steel Profiles for The Production of Steel Deck Reinforced Composite Slabs for Building
(Addis Ababa University, 2003-03) Redie, Rufael; Adamu, Asnake(PhD)
Floor and roof slabs constructed using composite panels of steel deck and concrete in which the steel deck panels serve both, as formwork and reinforcement are the practice of developed nations. The steel deck manufacturers developed their own cross sectional profiles and provide detail manuals where the thickness of the sheets ranges between 0.8mm to 1.5mm. This new technology has not been yet practiced in our construction industry. Thus, this Thesis Paper aims at assessing the local profile steel sheet products and develop analysis and design techniques for steel deck concrete composite slab for building, which fit our local conditions. The organization of the study can be viewed to consist of four main components, the first being assessment of the physical and mechanical properties and production process of steel sheet profiles produced by local manufacturers as well as foreign practices. Analysis and design requirement based on local building code requirement, foreign code of practice such as British Standard and international published books on the subject matter are dealt in the second part of the text for various stages of loading. Laboratory test for the assessment of tensile strength of local sheet and chemical as well as mechanical shear interlock between profile sheet and concrete conducted in the capacity of the local laboratory facility can be very well grouped as the third part of the manuscript. Design example for composite slab together with cost comparison between composite system and conventional slab construction are elaborated in the last section of the text. In general, Serviceability, Strength and Economy aspects of such construction are the main concerns of the study.
Seismic Microzonation For Central Addis Ababa
(Addis Ababa University, 2003-07) Mengistu, Araya; Haile, Messele(PhD)
This study is conducted to prepare seismic microzonation map to central part of Addis Ababa City. The basic method used is the observation and analysis of microtremors. The first effort was made by Ayele (2001) based on 40 observation sites. Latter detailed study was initiated by dividing the city in to five parts namely the northeastern, northwestern, central, southeastern and southwestern parts of which the central part is the study area for this thesis. In this thesis seismicity and related hazard for Addis Ababa city and its locality, historic records, geologic conditions and effects on earthquake, and the theoretical background used in preparing microzonation maps are presented. The nature of microtremors, basic characteristics and their use in estimating site-effects is also discussed together with the method of measurement, equipments used and available tools to analyze collected data. The suitability of microtremor based site-effect study has been tested by comparison of results with solutions from one dimensional analytical model for selected sites
Use of Composite Concrete Slab System Using Hollow Blocks and Precast Slab/Beam Member
(Addis Ababa University, 2004-06) Merid, Belay; Adil, Zekaria (PhD)
Housing is needed by many people in all parts of the country. Low-income persons usuallycannot afford to pay for the labour to build their houses and they have difficulty in doing thbuilding themselves because many of the construction methods and standard practices are toocomplicated. Simplification of the construction methods therefore seems to be a logical wayo reduce the cost of house. Moreover the increasing cost of construction materials and the time taken are the othenputs, which make the cost of construction to be expensive, and therefore the other way oeducing the cost of construction is to decrease the material and labour inputs. One of the temporary construction material inputs is the formwork. Formwork is a temporaryancillary construction used as a mould for structure, in which concrete is placed, hardens andmatures. The construction of formwork involves considerable expenditure of time andmaterial. The cost of formwork may be up to 20 to 25% of cost of structure in building workand even higher in bridges. In order to reduce this expenditure, it is necessary to design toeconomical types of formwork and mechanize its construction. When the concrete haeached a certain required strength, the formwork is no longer needed and is removed, in thcase of slab the formwork should be remain as it is for 14 days, this condition obstructactivities to be performed at lower level and affects the total time required for thconstruction. On the other hand the use of wood for use of formwork is a common practice in our country, and this significantly affects the countries limited source of wood. Therefordecreasing the use of formwork in the construction industry reduces the expenditure, time oconstruction and generally contributes in the reduction of deforestation. This study uses a simplified precast beam slab system, which reduces the use of formworkrom the usual way of construction technique.
Literature Review: Design of Structural Concrete Using Strut-Andtie Model and Application to Some Special Structures
(Addis Ababa University, 2004-09) Mohammed, Aziz; Z/Yohannes, Girma (PhD)
Through out history engineers have been looking for ways of designing structures that are simple and would accurately model real life objects. In order to achieve this, actual structures have to be modeled in such a way that they become amenable to analysis. This was mainly achieved by a mathematical modeling. Whilst many parts of structures can be modeled mathematically to relate accurately with the test results, some parts of a structure notably, where there are openings and discontinuities pose a problem. This is basically due to the inability to model them accurately, resulting in difficulty of obtaining reliable estimate of the stress values. On this line therefore various modeling approaches, for such regions of discontinuity have been proposed. These sections of “discontinuity” or in short “D-regions” include beam-column connections, areas of openings etc. These sections have been difficult to understand and analyze in the design of structures. Therefore, the question arises, how can all components of a structure be analyzed and hence understood and designed with equal accuracy? What alternative analysis approaches are possible? In the past many structural analysis approaches have been developed to address the various problems faced in real life. Some of the advanced features include the non-linear stress analysis, finite element method, etc. further to this the strut-and-tie modeling has been developed as an alternative structural analysis method to address regions of discontinuity, whose analysis has so far been addressed through the conventional analysis approach. The strut-and-tie model is a powerful tool for analyzing the structures in areas of disturbances or discontinuity in either geometry or statics. Hence, designing such special structures and xiv predicting their behavior will increase the possibility of using them in confidence, as well as making them safe. The objective of this thesis is therefore to introduce a brief actual review of the theoretical background, definitions of the strut-and-tie model, its compliance to the real world, brief example of selected structures (as an application of the Strut-and-tie model to real structure) and designing of a special structure. The final result gives structural engineers options of analysis approaches capable of application to all types of systems. By considering an alternative approach to current design approaches this study will be applicable to the analysis and design of special structures such as beam-column connections, openings in the shear walls, deep beams above large opening of a building (for circulation), corbels, monuments etc. The literature survey of the topic has encompassed review of landmark papers on this topic, textbooks, journals and available literature. Finally, two typical structures and one special structure, a monument, are designed in an attempt to visualize the Strut-and-tie model.
Alternative Approach for The Analysis of Suspended Slab Panels Under Partition Wall Load
(Addis Ababa University, 2005-06) Seyoum, Thomas; Zekeria, Adil(PhD)
Analysis techniques for most structural elements with different arrangement of externally applied loads are well developed and sufficiently covered with modern analysis theories. Further more, the application of today’s high-speed computers enables the analysis of complex structures with different load arrangements. In addition to these effective analysis tools, building design codes provide table of values and analysis charts for the analysis of different elements of structural systems. As one of the structural element in building structure, different analysis methods were proposed for the analysis of suspended slab panel subjected to non-uniform loads. Among the possible arrangement of externally applied loads on suspended slab panel a line load is the one which can best represent the weight of partition wall on it. Different simplified analysis methods were proposed to consider the contribution of this load to the design action effects. The current practice of accounting this partition wall loads in the analysis of suspended slab panel is to change it to the 'equivalent' uniformly distributed load. The analysis of regular slab panel subjected to uniformly distributed load may be carried out using computer softwares or using coefficients which are presented in many design codes (including the Ethiopian Building Code of Standards for concrete structures, EBCS 2 – 1995). The Swedish method and Reynolds method can be referred as some of the examples which are used to obtain equivalent uniformly distributed load. These methods analysis need to be investigated whether they can represent the actual load or not. Therefore, as it is important to address this problem, comparative analysis has been carried out. A new simplified method which considers the actual scenario has been developed. This newly proposed method makes use of coefficients derived from the basic principle of elastic analysis of plate. The results have been verified by comparing it with results of the finite element analysis. It enables us to make elastic analysis of suspended slab panel subjected to the weight of partition wall and avoids the uncertain use of approximate methods.
Pedestrian Cable Bridges for Ethiopian Rivers
(Addis Ababa University, 2005-07) W/Semayat, Tsegaye; Tebedge, Nigusie
Infrastructure is one of the most essential elements of development for any nation. It is vital for the advancement of economic activities, communication, administration and social interaction of a country. Like most developing nations, Ethiopia needs to expand its infrastructure of which the road sector calls for a special attention Currently, the Ethiopian government is investing billions of Birr on the improvement of the road sector. This being the case, the amount of money allocated will fall far short of the total sum of money the country needs to bring the road sector development to an acceptable level. The need for the road sector development is of paramount importance to the rural Ethiopia. These are areas where infrastructure, such as road, bridges, telecommunications, are necessities. For instance, two nearby villages could be separated for almost a season, waiting for the abatement of a small river that howls between them. An attempt to cross this river will result in death of people and their livestock. To mitigate the problem, the current Ethiopian government, seems to make an effort to construct roads and bridges that connect rural villages, by allocating a huge sum of money. The fact remains, however, such an endeavor demands much more money than the country can afford. Thus, calling for a system which takes cost and efficiency into account to alleviate the problem at hand. One of the methods that can be applied, and which has been proven to be efficient in other countries of a similar geographic context, is the building of low cost cable bridges, namely, the suspended cable bridges. These bridges have been introduced to our nation years back by a certain NGO by the name “Bridges for Prosperity” which built four bridges- two in Addis Ababa and two around Dessie.
Dynamic Analysis of Liquid Containing Cylinderical Tanks
(Addis Ababa University, 2005-10) Seyoum, Samuel; Zekaria, Adil(PhD)
Liquid containing cylindrical containers are one of those sensitive structures affected by dynamic loads. These liquid containing structures are affected not only by the inertia xi effect of the shell alone but also by the impulsive as well as convective pressures that are developed by the liquid they contain. There are a number of analysis methods; among them the Housner approximate method is widely used. In order to study the behavior of ground supported cylindrical tanks caused by dynamic loading a finite element method was undertaken. Using the FEM the flexibility of the shell wall and the liquid properties can be included. Due to the complex nature of theoretical approaches especially when considering the dynamic nature of structure, the use of software becomes very important. To model this system the ANSYS finite element software was used. Different parameters were considered, and the liquid was idealized as a displacement based element. For the analysis the three dimensional as well as two dimensional approaches have been used. And the fluid property such as sloshing and development of hydrodynamic effect were included in these elements. Ground supported cylindrical tanks having variable height, radius and thickness were analyzed. The results showed that the sloshing frequencies of the Housner approximate method and the FEM are comparable. The two dimensional FEM produced coupled frequencies of the system which have higher frequencies than the sloshing frequencies. As compared to Housner’s simplified method the shear for shallow and slender tanks obtained using the FEM are generally larger, while the bending moments obtained using FEM for slender tanks were smaller. The axial force of FEM was also found out to be significant. The vertical displacement of the free surface obtained using FEM for sloshing and coupled mode were very small as compared to Housner’s method. Key words: Cylindrical tanks; Sloshing; Fluid-Structure interaction xii
A Computer Program for Elastic Analysis and Design of Steel Space Frame Structures According to Ebcs 3 1995
(Addis Ababa University, 2006-09) Tilahun, Tamrat; Taye, Shifferaw(PhD)
An application program shall be developed for the elastic analysis of steel space frame structures and design of the structure members. Matrix method for the analysis of the structure and EBSC 3 1995 specifications for the design of members will be implemented. Subsequently a small application program which provides user interfaces in the input of data, analysis of the structure and design of members will be generated.
Behavior and Modeling of Semi Rigid Steel Beam to Column Connections.
(Addis Ababa University, 2007-09) Wondimu, Temesgen; Taye, Sjifferaw
In most steel frame designs the beam to column connections are assumed to be rigid or pinned. Rigid joints, where no relative rotation occurs between the connected members, transfer not only substantial bending moments, but also shear and axial forces. On the other extreme, pinned joints are characterized by almost free rotation movement between the connected elements that prevent the transmission of bending moments. Despite these facts, the great majority of joints doesn’t exhibit such idealized behavior. A substantial effort has been made in recent years to characterize the behavior of semi rigid connections. Most design codes included methods and formulas to determine both their resistance and stiffness. EC3 and EC4, for instance, allow the use of springs attached to the end of the beams at both sides of the joints. In order to account for the panel shear deformation the code allows the use of interaction parameter, called the β factor. But since the definition of the β factor implies an approximation of internal forces at the joint, it requires an iterative process at the time of the global analysis of the structure. In order to avoid this iterative process various researchers proposed new elements accounting for various deformation modes of the connections. Although the new proposed element by Bayo et.al accurately characterizes the behavior of semi-rigid connections based on the EC component method it is not appropriate to use in commonly available software. In this thesis a new component-based two-node-connection element is proposed. By using the proposed two-node element the static and dynamic response behaviors of a semi-rigid frame as compared to a rigid frame of the same geometry and cross section are studied using a general purpose finite element package ANSYS. The study showed that connection flexibility tends to increase vibration periods and hence reduces the internal stresses due to a given earthquake action in the frame elements as compared to those in rigid frames. 12 CHAPTER ONE 1.1. INTRODUCTION Traditionally, steel frame design assumes that beam-to-column joints are rigid or pinned. Rigid joints, where no relative rotations occur between the connected members, transfer not only substantial bending moments, but also shear and axial forces. On the other extreme, pinned joints are characterized by almost free rotation movement between the connected elements that prevents the transmission of bending moments. Despite these facts, it is largely recognized that the great majority of joints doesn’t exhibit such idealized behavior. This is explained by the fact that in semi – rigid frames the internal force distributions, lateral displacement magnitudes, collapse modes are functions of joint flexibility. Extensive studies have been carried out over the past twenty five years to estimate the actual behavior of such joints. Innumerable studies have been produced on composite and steel semi-rigid connections, covering the state of the art [1], numerical studies and experimental tests [2 - 8]. The fundamental results of these investigations led to code specifications that provided structural engineers with adequate procedures to evaluate the moment rotation characteristics of semi rigid connections. A good example of this new design trend is available in Eurocode3 [17]. Despite the substantial increase in structural design knowledge, the semi-rigid connection design is still facing resistance from structural engineers. This is explained by: 1. Lack of detailed information on the advantages of semi-rigid design philosophy. Semi-rigid frame design has many advantages. These include: a. Economy
Analysis and Design of Assembled Steel Truss Bridges
(Addis Ababa University, 2007-10) Tihitina Siyoum; Tebedge, Negussie(Prossefor)
Comparision of Prestressed Hollow Core Slab and Precast Concrete Beam‐Hcb Slab System
(Addis Ababa University, 2008-01) Shawel, Abebe; Taye, Shifferaw (PhD)
A prestressed hollow core slab element studied in this thesis is a precast prestressed concrete member with continuous voids provided to reduce weight and, therefore, cost and, as a side benefit, to use for concealed electrical or mechanical runs. Primarily used as floor or roof deck systems, hollow core slabs also have applications as wall panels, spandrel members and bridge deck units. This system of construction does not require form work and Propping during installation. Precast, prestressed concrete floors offer significant advantages in many types of building construction. They offer design, time and cost advantages over other flooring materials and systems and are suitable for use with all structural systems, i.e. concrete, masonry and steel In our country precast prestressed concrete elements are not widely used for construction of most buildings. The conventional cast in-situ construction require lots of formwork and construction time, and also the precast beam-slab system construction require propping and construction time too which increases the total cost of a project. When precast prestressed hollow core slab elements are introduced in vast amount in the construction of buildings, an economical construction could be achieved. The economy of the generalized hollow core slab system is require a short construction time compared to precast beam slab system and in the quantity of slabs that can be produced at a given time with a minimum of labor required. Each slab on a given casting line will have the same number of pre-stressing strands. Therefore, the greatest production efficiency is obtained by mixing slabs with the same reinforcing requirements from several projects on a single production line. This implies that best efficiency for a single project is obtained if slab requirements are repetitive. In the present study, the advantages of prestressed hollow core slab elements, for construction of the floor slabs of four story building, is shown by making cost comparison between the precast beam-slab system and pre-stressed hollow core slab system. For this iii purpose, the same span length is chosen for the two slab systems. These elements are designed for loads they should sustain when used in the construction of slabs. Finally cost comparison is made between the two systems of slab construction. The cost comparison showed that the prestressed hollow core slab system
Evaluation of Analysis and Design Results of Reinforced Concrete Walls Carried out using ETABS
(Addis Ababa University, 2008-03) Kassa, Wondimu; Zerayohannes, Girma(PhD)
The use of commercial application programs is well established in the local structural design offices working in Ethiopia. Among the most widely used programs are SAP2000 and ETABS by CSI, California, Berkeley. User confidence in respect of analysis results is reasonably high for building structures or bridges whose lateral force resisting systems comprise 3-D rigid frames. For buildings with wall or dual wall-frame systems, however, the comparison is not so straight forward, and has not yet been systematically investigated and reported. More recently some users while accepting the drawbacks in respect of the design of columns tend to accept the design results of walls as valid. Clearly, response of structural walls to axial load and biaxial bending is much more involved than their column counterpart. In an effort to show the proximity and/or divergence of the results of ETABS with other soft wares and analysis methods the following processes has been performed. 1. Lateral load distribution results of ETABS were compared with those of the approximate elastic analysis procedure for a system of walls. 2. Column reinforcement results of ETABS were compared with those from interaction charts of EBCS 2 Part2. 3. Reinforcement of the walls from ETABS was checked by software specially developed for checking capacities of structural walls of any shape under normal load and biaxial bending. From the lateral load distribution comparison result, it was observed that there were differences between the outputs of ETABS and the approximate elastic analysis. The percentage difference varies from one wall arrangement type to another and wall section to wall section. In case of the design results, column reinforcement areas obtained from ETABS were larger than those from interaction charts of EBCS 2 Part 2. For the simple rectangular structural walls considered, the reinforcement from ETABS was found to be insufficient to resist the design actions on it. The same thing was observed on the L-shaped walls. Where as for the C-shaped walls designed by ETABS the capacity to demand ratio were nearly 1. vii Based on the comparison results of the design of a limited number of columns and walls, it may be concluded that the design of walls and columns performed by ETABS may lie on the safe side or the unsafe side.
Strength Evaluation of Existing Bridges
(Addis Ababa University, 2009-01) Bayou, Yonnas; Adamu, Asnake(PhD)
A bridge must be inspected on regular basis to ensure public safety and to protect public investment. Bridge inspection program helps to identify the needs of bridges for repair, maintenance, preservation, reconstruction and replacement. Many bridges have collapsed in Ethiopia and other countries. Periodic inspection and maintenance of bridges helps to avoid this problem. Recently bridge inventory and inspection program has begun in Ethiopia. This program has proved to be very useful in providing information about bridges in Ethiopia which otherwise would have been unavailable. According to a report from this program, quite a large number of bridges are in critical condition needing immediate intervention. This can be disastrous if remedial actions are not taken by the concerned bodies in due times. One of the key components of a bridge inspection is load rating. This is a method to know the strength of an existing bridge to carry current traffic loads. When the load rating of a bridge is greater than or equal to one, it implies that the bridge is strong enough for current traffic conditions. Load rating or strength evaluation of existing bridges is quite different in some respect from designing of a new bridge. This is because in strength evaluation, the loads are taken to represent the actual traffic condition. Since bridge inspection and maintenance activities started recently in Ethiopia, much is not known about strength evaluation of bridges. This thesis has thus made an attempt to address such problem by developing a computer program that will be used to load and evaluate the rates of simple span slab type and girder concrete bridges
A computer program for generating design charts of L-shaped short columns on the basis of EBCS 2 - 1995
(Addis Ababa University, 2009-07) Mohammed, Melaku; Zerayohannes, . Girma Ing (Associate Professor)
In this thesis a program is developed to generate design charts of L-shaped reinforced concrete column on the basis of EBCS-2, 1995. Design chart can be prepared for any cross-sectional dimension of columns with possible arrangements of reinforcement bars. The program will have also freedom for the choice or different reinforcement and concrete grades. The section is always bi-axial and strength is computed by assuming different position of the neutral axis of given orientation. Strain compatibility and equilibrium equations are applied for the section capacity determination according to the Ethiopian Building Code Standard. Green’s theorem is used to convert the double integral over the area in to line integral. The Gaussian Integration is also used to convert the double integral over the compressive zone in to a line integral along the perimeter of the compressive zones. Finally numerical method is used to convert the line integral in to simpler mathematical expression for programming. The principles of coordinate geometry are used to calculate the intersection point of two lines, the distance between to points and other important parameters to be incorporated in the program. Although equivalent rectangular stress-distribution due to Whitney can be used with out much loss in accuracy, the parabolic-rectangular stress distribution is used for the analysis of the concrete section as is primarily recommended by EBCS-2, 1995. The design chart can be generated for all possible reinforcement ratios and any possible orientation of the neutral axis. It should however be noted that the Ethiopian building code standard limitations on the reinforcement ratio, section dimension, amount of reinforcement bars should be maintained for good design. The program is written in visual Fortran programming language; however, the program can be run from Microsoft visual C++ window without any change in the algorithm. The output of the program will be automatically exported and saved in to a text file that can be opened using Microsoft office excel program to generate the charts. The chart generated is finally verified with registered version of Alashki’s program for accuracy and satisfactory results are obtained.
Design and Cost Comparison of Reinforced Masonry and Reinforced Concrete Building Structures
(Addis Ababa University, 2009-07) Nega, Kalehiwot; Zerayohannes, Girma (PhD)
Most building structures known to be constructed in Ethiopia and other many countries contain, by rule of thumb or knowledge, some proportion of masonry components. Despite this reality, the development of analysis and design techniques for masonry structures has lagged behind reinforced concrete. The lack of engineered guide lines, at governmental level, to the design of reinforced masonry and failure of local universities to deliver courses on masonry has played their shares in the ill-treatment of this potentially rich construction material-masonry. Not few people perceive, as stone solely, the meaning of masonry and have clouded perceptions regarding the extendible use of this material as core component of a structure. This research work, therefore, attempts to set some insights on the actual meaning of masonry and the possible positive outcomes that can be enjoyed by making use of it in an engineered manner. To do so, this thesis introduces some of the available methods of design based on limit state design philosophy and so investigates some standard documents, in the captioned philosophy, like Ethiopian building code standard and the British code for design of masonry. Based on techniques in the reviewed materials a G+4 building structure, consisting of reinforced masonry wall as a main structural component and located in a Zone 2 seismic region of Ethiopia, is modeled in 3-D by equivalent frame idealization, designed and its cost is compared with a similar reinforced concrete building. It is found that better economy, with overlapping advantages of sound insulation and short construction time are gained from the use of reinforced masonry as a main structural component of building structures with current and practical price ranges. Considering gradual cost increase in masonry units and decrease in cost of cement, starting from current prices of both materials, the break even point for the cost of construction of the designed building using both construction material types is found.
Analysis Design and Cost Effectiveness of Precast Beam-Slab System
(Addis Ababa University, 2009-07) Matheas Kebede; Girma Zerayohannes (PhD)
Pre-cast beam-slab is made of pre-cast reinforced concrete beam together with hollow blocks. The pre-cast beams are spaced at certain intervals and the hollow blocks are placed on them to form a working platform with out the use of formwork. The slab HCB, hanging between the pre cast beams are functioning like a formwork. They give only a temporary support during the installation phase. Only the pre-cast beams and the slab concrete are load bearing parts of the slab. In our country pre-cast beam-slab system is not widely used for construction of most buildings. The conventional cast institu constructions require lots of formwork and construction time, which increase the total cost of a project. When pre-cast beam slab systems are introduced in the construction of buildings, an economical construction could be achieved. In the present study, two types of pre-cast beam elements are chosen. Experimental studies are made on these beam elements by casting them in the laboratory condition. From experimental observation, there tried to come up with a new theoretical model. Loaddeflection data was taken from the experiment and compared with the theoretical output. Furthermore cost comparison is made between the two systems of slab construction. For the arrangement of panels used to compare cost, the pre-cast beam-slab system of construction is more economical than the conventional system. Finally, the model gives a hint for future study in trying to simulate the actual pre-cast beam slab system.

Browse

Browsing Structural Engineering by Issue Date

Results Per Page

Sort Options