Abstract:
This project aims to evaluate the ophthalmic hospital in Nablus, which has a mixed structural system of braced (stone) frames and shear walls.
The evaluation will include static, dynamic, and soil structure interaction analysis, in 3D view, in order to approach the actual model as much as possible.
Two Methods will be used:
1.Manual analysis: assuming 1D structural elements, using recommendations of ACI -05, as done in most engineering offices, (trying to match the reality).
2.Program analysis: (assuming 3D views, and 1D, 2D structural elements, using structural analysis program sap 2000 v.12, more close to reality).
After the checks on the model, by manual analysis and by program, the results will be compared with the as built design details, evaluate of the as built detail will be performed, first for the gravity loads and then for both, gravity and seismic loads.
1.1 What is design?
1.1.1 Introduction:
Reinforced concrete, as a composite material, has occupied a special place in the modern construction of different types of structures due to its several advantages. Italian architect Ponti once remarked that concrete liberated us from the rectangle. Due to its flexibility in form and superiority in performance, it has replaced, to a large extent, the earlier materials like stone, timber and steel. Further, architect's scope and imaginations have widened to a great extent due to its mould ability and monolithicity. Thus, it has helped the architects and engineers to build several attractive shell forms and other curved structures. However, its role in several straight-line structural forms like multistoried frames, bridges, foundations etc. is enormous.
The design of these modern reinforced concrete structures may appear to be highly complex. However, most of these structures are the assembly of several basic structural elements such as beams, columns, slabs, walls and foundations. Accordingly, the designer has to learn the design of these basic reinforced concrete elements. The joints and connections are then carefully developed.
Design of reinforced concrete structures started in the beginning of last century following purely empirical approach. Thereafter came the so-called rigorous elastic theory where the levels of stresses in concrete and steel are limited so that stress-deformations are taken to be linear. However, the limit state method, though semi-empirical approach, has been found to be the best for the design of reinforced concrete structures. The constraints and applicabilities of the limit state method will be considered in the design of this project.
1.1.2 Designobjectives:
Every structure has got its form, function and aesthetics. Normally, we consider that the architects will take care of them and the structural engineers will be solely responsible for the strength and safety of the structure. However, the roles of architects and structural engineers are very much interactive and a unified approach of both will only result in an "Integrated" structure, where every material of the total structure takes part effectively for form, function, aesthetics, strength as well as safety and durability. This is possible when architects have some basic understanding of structural design and the structural engineers also have the basic knowledge of architectural requirements.
Both the engineer and the architect should realize that the skeletal structure without architecture is barren and mere architecture without the structural strength and safety is disastrous. Safety, here, includes consideration of reserve strength, limited deformation and durability. However, some basic knowledge of architectural and structural requirements would facilitate to appreciate the possibilities and limitations of exploiting the reinforced concrete material for the design of innovative structures.
Before proceeding to the design, one should know the objectives of the design of concrete structures. The objectives of the design are as follows:
1.The structures so designed should have an acceptable probability of performing satisfactorily during their intended life.
This objective does not include a guarantee that every structure must perform satisfactorily during its intended life. There are uncertainties in the design process both in the estimation of the loads likely to be applied on the structure and in the strength of the material. Moreover, full guarantee would only involve more cost. Thus, there is an acceptable probability of performance of structures as given in standard codes of practices of different countries.
2. The designed structure should sustain all loads and deform within limits for construction and use. Adequate strengths and limited deformations are the two requirements of the designed structure. The structure should have sufficient strength and the deformations must be within prescribed limits due to all loads during construction and use.
However, sometimes structures are heavily loaded beyond control. The structural engineer is not responsible to ensure the strength and deformation within limit under such situation. The staircases in residential buildings during festival like marriage etc., roof of the structures during flood in the adjoining area or for buildings near some stadium during cricket or football matches are some of the examples when structures get overloaded. Though, the structural designer is not responsible for the strength and deformations under these situations, he, however, has to ensure that the failure of the structures should give sufficient time for the occupants to vacate. The structures, thus, should give sufficient warning to the occupants and must not fail suddenly.
3.The designed structures should be durable.
The materials of reinforced concrete structures get affected by the environmental conditions. Thus, structures having sufficient strength and permissible deformations may have lower strength and exhibit excessive deformations in the long run. The designed structures, therefore, must be checked for durability. Separate checks for durability are needed for the steel reinforcement and concrete. This will avoid problems of frequent repairing of the structure.
4.The designed structures should adequately resist to the effects of misuse and fire.
Structures may be misused to prepare fire works, store fire works, gas and other highly inflammable and/or explosive chemicals. Fire may also take place as accidents or as secondary effects during earthquake by overturning kerosene stoves or lantern, electrical short circuiting etc. Properly designed structures should allow sufficient time and safe route for the persons inside to vacate the structures before they actually collapse.
1.1.3 How to fulfill the objectives?
All the above objectives can be fulfilled by understanding the strength and deformation characteristics of the materials used in the design as also their deterioration under hostile exposure. Out of the two basic materials concrete and steel, the steel is produced in industries. Further, it is available in form of standard bars and rods of specific diameters. However, sample testing and checking are important to ensure the quality of these steel bars or rods. The concrete, on the other hand, is prepared from several materials (cement, sand, coarse aggregate, water and admixtures, if any). Therefore, it is important to know the characteristic properties of each of the materials used to prepare concrete. These materials and the concrete after its preparation are also to be tested and checked to ensure the quality. The necessary information regarding the properties and characteristic strength of these materials are available in the standard codes of practices of different countries. It is necessary to follow these clearly defined standards for materials, production, workmanship and maintenance, and the performance of structures in service.
1.2 What is evaluation?
The notion of evaluation has been around a longtime-in fact, the Chinese had large functional evaluation systems in place for their civil servants as long ago as 2000 B.C. Not only does the idea of evaluation have a long history, but it also has varied definitions. Evaluation means different things to different people and takes place in different contexts.
Thus, evaluation can be synonymous with tests, description, documentations, or management. Many definitions have been developed, but a comprehensive definition is presented by the joint committee on standards for educational evaluation (1981):
“Systematic investigation of the worth or merit of an object...”
This definition centers on the goals of using evaluation for a purpose. Evaluations should be conducted for action-related reasons, and the information provided should facilitate deciding a course of action.
Over the years, evaluation has frequently been viewed as an adversarial process. Its main use has been to provide “thumbs-up” or “thumbs-down” about a program or project. In this role, it has all too often been considered by program or project Directors as an external imposition thatis threatening, disruptive, and not helpful to project staff. Our contention is that while this may be true in some situations, this is not the case in all, or even in most, evaluation efforts. In addition, today in contrast to two decades or three ago, the view is gaining around that evaluation should be a tool that not only measures, but also can contribute to success.
Evaluation can serve many different needs and provide critical data for decision-making at all steps of project development and implementation. Although some people feel that evaluation is an act that is done to a project, if done well, an evaluation is really done for the project.
It is important to remember that evaluation is not a single thing, it is a process, when done well, evaluation can help inform the managers of the project as it progresses, can serve to clarify goals and objectives, and can provide important information on what is, or is not, working, and why.
2.1 Introduction:
Hospitals are considered as one of the most important buildings in the public sector, because of huge number of people, and expensive, important equipments that may exist in hospitals. So, many precautions should be taken before, during, and after design of hospitals in order to avoid the failure caused by additional loads and the natural disastrous circumstances, to achieve health and economical safety.
In this project, we will evaluate (SulamaBintButti) charitable ophthalmic hospital in threestages:
First:static design, considering gravity loads, live and dead. Second:dynamic loads, considering horizontal loads,(such as seismic loads). Third: soil structure interaction, considering the relationship between reactions oncolumns,and settlement infootings until convergence.
By these stages, we hope to achieve integrated design dependingon scientific knowledge, engineering judgment, and practical experience.
On the other hand, the engineering offices depend on static design only, and 1D analysis, which neglect the effect of lateral loads, and make inaccurate modeling that is far from the actual representation for the structures, and can only be justified for conceptual understanding.
2.2 Description:
Evaluationof any project requires providing full information about it, to be able to evaluate in a good way, achieving justice as much as possible, and any lack of information will affect negatively on evaluation. The following provisions describe the project.
2.2.1 Locationdescription:
Geography:the ophthalmic hospital lies beside AseeraStreet, in the northern mountain, in Nablus city.For more details about the location,see location map in appendix (G1).
Topography: the site nature is mountainous,moderate steep and high variant in elevations. For more details about hospital landtopography, see appendix (G3).
Geology: the site investigation reports for the project are not found. So, the reports of the neighborhood location are considered (reports of the Orphan School).Depending on the mentioned reports, the project is expected to be constructed on hard to medium hard limestone soil withvariable bearing capacity depending on the depth of the foundations.As ageneral recommendation depending on site investigation use bearing capacityof(3kg/cm²),as shown in appendix (G5).
2.2.2 Structuredescription:
Structural description:
The hospital has approximately a uniform grid with spans lengths between (6.5 – 7.5)m,which are constructed by two-way ribbed slab system,(to reduce the effect of large deflections, and economical saving). It has a structural system of braced (stone) frames and shear walls, with a structural separator in the middle of the hospital (to divide the building into two structures, increasing the seismic resistance for every one), besides, it is constructed on two levels (see appendix (S1), and appendix (S2)).
Architecture description:
The hospital consists of five stories:a basement (area = 900m²), three floors (total area = 3545m²), and a roof (area = 830m²), with 4.16 m height per storey, as shown in the appendices:for elevations (A1) to (A4) and for plans (S5) to (S9).
2.3 Construction material:
The properties of materials used in this project are not available on a hard copy, so, they will be assumed depending on practice in Palestine and the approximate known used ones, See appendix (S21).
2.3.1 Physical properties:
These properties are related to the material its self in any situation the material is, such as material densities.
1.Reinforced and plain concrete: Reinforced concrete is mainly used in slabs, shear walls, columns, stair, andfootings.Density of R.C= 2.5 ton/m³. Plain concrete is mainly used in masonry walls between stone and blocks. Density of plain concrete= 2.3 ton/m³.
2. Stone: Used in external walls for buildings to give beautiful aspect. Density of stone = 2.6 ton/m³.
3. Blocks: Used for internal dividing in buildings,external walls,and in ribbed slabs. Density of blocks used in ribbed slab = 1.2 ton/m³. Density of blocks used in internal dividing andexternal walls= 1.4 ton/m³.
4.Steel: Used in concrete reinforcing, especially in tension stresses (where concrete is very weak), and as ties for confinement of concrete and bonding steel. Density of steel= 7.86 ton/m³.
2.3.2 Mechanical properties:
These properties are related to behavior of material under forces, (such as, modulus of elasticity, compressive strength(concrete),and yielding stress (steel)).
1.Reinforced concrete: Compressive strength of concrete used in slabs, shear walls,columns, and beams is B300 kg/cm². Compressive strength of concrete used in masonry walls B150 kg/cm². Compressive strength of concrete used in cleanness concrete B200 kg/cm².
2.Steel: Yielding stress (fy) = 4200 kg /cm². Modulus of elasticity (Es) = 200Gpa= 2*106kg/cm². (ACI 318-05 8.5.2).
Note: concrete investigation has not been found, so no checks of the actual strength of structural members have been done.
2.4 Codes and analysis methods:
Engineering is a renewable science depends on physical laws and experimental observations. So, during the last decades, many methods were used to explain the behavior of structures,and these methods are still used until afailure in structures occurs, then a new method appears and so on.
Now, after many developments on engineering methods during the last decades, more accurate methods are appeared, which have less error than provisions methods.
Inthe last decades,the experimental knowledge and experience, have been documented and arrangedin a uniform way, called codes, so, when these codes depend on the local practice and experience, every country or nation has its private codes,despite, these codes could be used in other nations with carefulness with difference between local practices in different countries. In this project, we will use the following methods and codes for evaluating:
1. American Concrete institute (ACI-2005).
2. Ultimate design method
2.5 Loadings:
Humans were, and are still trying to overcome the natural phenomena in order to have a comfortable life, and one of these phenomena is loading (due to gravity, lateral, etc). Loading controls and affects the affecting of humanitarian activities, due to resulting stresses, which may be larger than the stress capacity of the structure elements and materials, so, loading affect the structure should be considered. Types of loadings considered in design in this project are as follows:
2.5.1 Verticalloads:
Dead loads:
Dead loads are constant loads in place, including the weight of the structural elements, (such as slabs, beams, columns, and foundations), and super imposed loads, (such as filling, tiles,and walls).
Live loads:
Live loads are changeable loads in place like weight of people, furniture, and the house content. Live loads are changeable with the variation of type of structures, for example, in residential buildings, density of people and thus live load is less than in public buildings,(such as schools,universities, and hospitals).
2.5.2 Lateralloads:
Earthquake loads:this load affectsstructurevertically and horizontally. The horizontal component is more dangerous than vertical component because it makes shear forces on the structures. So, itshould be consideredin analysis to achieve safety.
Earthquake load effect varies with the magnitude of the earthquake, structural system, soil type, site seismicity, and structure period.
2.6 Load combinations:
The method used in this project is the ultimate design method. This method uses factors of safety for different loads,and these factors are changeable depending on the type of load.
The load factors are: (ACI 318-05 9.2.1)
Wu= 1.4D.L
Wu= 1.2D.L+ 1.6L.L
Wu= 1.2D.L +1.0L.L ±1.0E
Wu= 0.9D.L ±1.0E
Where: D.L: Dead load. L.L: live load. E: Earthquake load.
3.1 Introduction:
Modeling is the language between the engineer and the computer, which helps the engineer to represent the actual structure as he understands,and making the calculations and analysis on the model depending on the engineering laws and theories.
Since, the model the engineer builds should be as it is in the mind of the engineer, achieving the laws and theories the engineer follows in his work. So, it is necessary to know if the model on the computer achieves the required limitations and considerations, or not, by considering the following conditions: