Structural Engineering

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https://hdl.handle.net/20.500.11888/3186

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Developing a Computer Program for Analysis and Design of Reinforced Concrete Sections; AD RCS
(2004) Ibrahim Muhammad Ahmad Mahmood; Dr. Abdul Razaq Touqan
A need for a computer program to analyze and design reinforced concrete sections for both academic education and engineering offices services is beyond doubt. Also, a need for having programs in Arabic language to help in communication of engineers graduated from all over the world is becoming increasingly important. This thesis presents a computer program that tries to fulfill previous needs based on ACI code and presented in both Arabic and English languages, and uses local and international units. The computer program; Analysis and Design of Reinforced Concrete Sections; AD RCS; is constructed using Visual Basic 6 programming language. The input and output data are performed using dialog boxes in windows environment. The program has the ability of analyzing reinforced concrete sections of beams, columns and single footings and also design them for flexure, shear, axial and torsion. It also introduces capacity interaction diagrams and section reinforcement details.
Simplified Conceptual Equation for Soil-Structure Interaction for Simple Structures Due To Vertical Loads for Practical Purposes
(2016) Fawzi S. Abu-Aladas; Dr. Abdul Razzaq A. Touqan; Dr. Mahmud M.S. Dwaikat
The non-uniform settlements represent a big challenge for the structural engineers due to the problems caused by this phenomenon. Many cracks in the walls, columns and slabs occur due to such non-uniform settlements. These cracks range from small cracks to major cracks that may threat the safety of the building and the residents. Along the years, geotechnical engineers have developed many methods to find settlements in soil. However, these methods need certain expertise and knowledge in the properties and the conditions of soil, which many structural engineers are poor at. Therefore, and because of the importance of the soil-structure interaction, this study focuses on proposing simplified equation to estimate the settlements of soil with acceptable accuracy for practical purposes, like design or field checks. To simplify the process, the displacement will be presented as ratios and will be used as a reference for the fitted equation, where the soil settlement and the displacement of structure are assumed dependent by taking the ratios to the total displacement, which represents the summation of the soil settlement and the displacement of structure. By knowing displacement of structure and the displacement ratio, the soil settlement can be found, and vice versa. Within this thesis, the applicability of the main assumptions used in soil structure interaction will be demonstrated for simple structure of one square column and footing and simple two-span frame with identical columns and footings dimensions. The finite elements method will be used as the calculation tool for the displacements of the structure and the soil, where to assure acceptable accuracy, the soil and the structure will be simulated as multi nodded three-dimensional elements, meshed to certain dimensions that give accurate results. The equations for the displacement ratios will be fitted using the finite elements results, and the results will be discussed by conducting comparisons between the results from finite elements and the equations, in order to assess the accuracy of the equations’ results.
Seismic Assessment and Rehabilitation of Existing Buildings Using Nonlinear Static Procedures (NSPs) -Pushover Procedures-
(An-Najah National University, 2017-07-13) Shehadah, Anas Shaher Abdul-Hafeeth; Dwaikat, Mahmud
Design of buildings for seismic loads is becoming mandatory in Palestine. However, what about the existing buildings? Existing buildings, especially old ones, were mostly designed under the influence of static loads. Such buildings may stand vulnerable to earthquakes and thus need to be strengthened; so that they become safe. To achieve the required level of strengthening, advanced analysis and assessment tools must be used. There is a lack of systematic studies that provide practical "know-how" guidelines for local engineers on the assessment and retrofitting of existing buildings against seismic loads. Generally, the guidelines written in foreign codes (e.g. the ASCE or FEMA) are very broad and general and may pose a challenge to local engineers regarding the consistency of their implementation. This study bridges this gap between local engineers and international codes by putting these guidelines into action through a practical case study. Generally, four procedures are available for seismic analysis of buildings: two linear procedures, and two nonlinear procedures. The nonlinear procedures include the nonlinear static procedure (NSP) and nonlinear dynamic procedure (NDP). NSP's are deemed to be very practical tools to assess the nonlinear seismic performance of structures. On the other hand, NDP's require detailed input data, and it is very time-consuming, which is a relevant drawback in design offices, where the deadlines are restrictive. Also, it doesn’t exist in Palestine neither local earthquake records, nor specialized powerful programs for NDP. This makes the NSP best choice for practical assessment of buildings. The research objective in this thesis is to demonstrate an assessment methodology through studying a local existing building, which was designed under gravity loads only, and then propose retrofitting solutions to remedy the deficiencies in the building. Based on the above, the case study building is assessed using an NSP that is called capacity spectrum method (CSM) as per ATC-40. The behavior of the structure is generated using nonlinear pushover analyses. The seismic assessment were conducted based on FEMA 356 performance criteria. According to FEMA 356, there are two approaches for seismic evaluation: global-level and member-level with three performance levels, which are immediate occupancy (IO), life safety (LS) and collapse prevention (CP). In addition, seismic design requirements that are mentioned in ASCE 7-10 were conducted in order to assess the building for irregularities. Based on the nonlinear pushover analysis and the assessment of the building, it was found that the building suffers from vertical irregularities and concentration of plastic hinges at the ground floor. In order to improve the performance of the building, two possible retrofitting techniques were applied including the addition of RC column jackets, and moment resisting RC frames. The capacity curves for the retrofitted structure were compared to those for the un-retrofitted case. FEMA global drift limits were compared with the drift limits of the performance points of each retrofitting techniques based on the FEMA member-level criteria. In addition to this, the ASCE limits were also rechecked and compared to the ratios of the un-retrofitted building. The retrofitting techniques helped improve the performance of the building. This thesis paves the way to further research on seismic assessment of existing buildings with effective tools for judging the efficiency and suitability of retrofitting techniques.
Effect of Using Fiber Reinforced Polymers on the Ductility of Retrofitted Reinforced Concrete Joint
(An-Najah National University, 2018-01-24) أبو طحنات, يزن بسام; دويكات, محمود
Reinforced concrete (R.C) structures are common in Palestine. One considerable weakness in these structures is the connection between beams and columns. Several researchers showed that reinforced concrete joints suffer brittle failure due to combined effect of loading on the joints. Therefore, the ductility of the beam-column joints in reinforced concrete structures is an essential factor to prevent sudden failure of the joint. Different techniques were adapted by several researchers to increase the ductility and strength of beam-column joints including the use of high strength concrete, special stirrups and reinforcement configuration, steel plates and Fiber-Reinforced Polymer (FRP). One way to improve the ductility of such joints is the use of sheet wraps of FRP. This research focuses on studying the effect of using FRP wraps on exterior RC beam-column joints. Finite Element (F.E.) analysis using commercial FE software (ABAQUS) is used to investigate the ductility behavior of RC joints strengthened by FRP. The model is validated using available published test data. This model is used to conduct a parametric study on the key factors that affect joints nonlinear behavior. Results are used to develop simple conceptual equations to predict the ductility of exterior beam-column joints as a function of the applied FRP. Such equations can be used as an initial conceptual design step for checking the adequacy of RC beam-column joints in seismic design of RC buildings.
Enhancing Earthquake Resistance of Local Structures by Reducing Superimposed Dead Load
(An-Najah National University, 2018-02-08) منذر دويكات , عبدالرزاق طوقان
The geographical location of Palestine along the Aqaba-Dead Sea Transform Fault, the highest seismic active boundary in the Middle East, had put the country in a major hazard over the past history. Although seismic hazards across the area with relatively low probability, the less attention given towards seismic guidelines in both design and construction in the local practice is expected to play a significant role on the intensities of the coming ground shakings. Ribbed slab systems supported on embedded beams and overloaded by superimposed dead loads (SDLs) are a common flooring system in the local construction industry. Literatures focus on the seismic response behavior of ribbed slabs, hidden beams, or heavy constructions indicate an earthquake-prone buildings. Hence, the existing of such undesirable factors combined exceedingly exacerbates the strength of earthquake shaking. In this respect, the factor of SDL which is one reason of heavy construction is studied. Solid slab with drop beams construction is utilized as a flooring system in a set of reinforced concrete framed structures. The framed structures are supposed to be built on three different soil profile types in Nablus, and one more sensitive soil profile type in Jericho. At every particular site, there are three structures sustaining a SDLs of 1kN/m2, 3kN/m2, and 5kN/m2. This, however, is to investigate the impact of the reduction in the SDL at different site effects on the materials cost (Concrete, and steel) of frame beams and columns. The representative computational models are constructed, analyzed and designed using the finite element program SAP2000, Version 19.1.1. The analysis is done by means of modal response spectrum method described in the Minimum Design Loads for Buildings and Other Structure (ASCE/SEI 7-10), whereas the design is accomplished on the basis of the Building Code Requirements for Structural Concrete and Commentary (ACI 318-14). In final conclusion, the developed approach of reducing SDL form 5kN/m2 to 1kN/m2 can reduce the materials cost in the skeletal elements of about 25%.
Effect of Shear Wall Openings on the Fundamental Period of Shear Wall Structures
(An-Najah National University, 2018-08-13) محمود دويكات, عبدالرزاق طوقان
A common approach in resisting lateral forces is the use of reinforced concrete shear walls in low-rise and mid-rise buildings. These walls represent the main elements to resist the lateral forces due to their large strength and stiffness. However, such walls may contain many openings like doors and windows due to functional requirements, and this may largely affect the overall lateral stiffness of them. It is thus of prime importance to quantify the effect of openings on the dynamic performance of the shear walls. To generate data on the effect of openings on the fundamental period of shear walls, finite element analysis using SAP2000 structural analysis program is used as a main source in this study after verifying the results by comparing them to theoretical equations proposed by Hsiao in 2014 and hand calculations of period using Rayleigh’s method. Finite element analysis is made first by using linear elastic analysis at the wall level with different central window opening sizes, and for different wall heights. Then, multi-floor typical shear wall buildings with different central window opening sizes are studied for various numbers of floors and different stiffness ratios of walls to columns. The results are compared to ASCE7-16 code equations for estimating the fundamental period of shear wall structures. After conducting this study, it is found that the openings in concrete shear walls have a major effect on the fundamental period and on the lateral stiffness of shear-walled structures. Central window opening ratio of 3% is the maximum ratio that can be neglected safely in a one floor building, and this ratio increases by increasing the number of floors. Door opening ratio of 65% converts the solid wall to behave as a frame. The effect of wall openings on the fundamental period of shear wall structures depends on the height of the building and on the deflection mode of the shear walls, where it is either shear or flexural deflection mode. Finally, statistically regression is used to fit an equation for estimating the increase in the fundamental period of the shear – walled regular structures due to openings in the shear walls. Such an equation is quite useful in the conceptual design phase of buildings. The final results are discussed by conducting comparisons between finite element results and the fitted equation results.
The Effect of Various Patterns of Internal Partitions on the Fundamental Period of Reinforced Concrete Framed Buildings -Experimental and FE Modelling Study
(جامعة النجاح الوطنية, 2018-09-20) Qarout, Ola Mohsen
Reinforced concrete (RC) with infill wall partitions are common structures in Palestine. The presence of infill walls can definitely influence the seismic behavior of the structure, as they contribute to the total mass and stiffness of the structure. Specifically, the fundamental period of the structure, which depends mainly on the stiffness and mass of the structure, can be influenced by the existence of brick walls. Several models were proposed by different researchers to predict the seismic behavior of infill wall structures, and also to study their effect on the fundamental period of the whole structure. However, one obvious shortcoming of these models is that their properties do not match those of the brick walls commonly used in Palestine. Therefore, this thesis involves a study to predict the stiffness of brick walls used in Palestine based on 3-D nonlinear F.E. analysis. Some needed parameters in this modeling are taken from experimental tests which were conducted as a part of the work of this thesis. The results of this study were used to develop strut models equivalent to real brick walls. This, in turn, would facilitate modeling and analysis of buildings by using struts as substitutes to brick wall partitions. After that, the effect of these partitions on the fundamental period of the structure was studied. For this goal, macro modeling of RC framed structure was carried out with several patterns of partitions. The results of this study were simplified into two simple, reasonable and practical equations. One of these equations is used for predicting the equivalent strut width as a function of wall length and the column size of the surrounding frame. The other equation is used for predicting the fundamental period of the structure with infill wall partition as a function of the density of partitions distribution in the structure.
Effect of Column Orientation on Response Modification Factor (R-Factor) of Reinforced Concrete Frames
(An-Najah National University, 2018-09-20) زيد, أحمد محمود عبد الله
Response Modification factor (R-Factor) is an essential seismic design parameter, which is typically used to describe the level of inelasticity expected in structural systems during an earthquake and is used to reduce the anticipated earthquake load due to the inherent inelasticity of the structure. International building codes provide fixed values for this factor for each category of building system despite the fact that its value depends on the details of the structural system and thus should differ for each building. One of the aspects of buildings in Palestine is their irregularity and this includes the disorientation of columns strong axes in the building plan to suit architectural needs. In Palestine, the international codes are generally applied with little to no guidelines on the validity of these codes to the buildings being designed. To-date, there are no guidelines as to how this R-Factor would change due to the disorientation of main axes of the load-bearing columns in the building. This study comes as a step towards investigating the validity of the code-specified values of the R-factor for framed buildings with disoriented columns. To achieve the above-mentioned goal, pushover analysis is considered as a nonlinear procedure to predict the inelastic behavior of framed buildings, by exposing the structure to increasing lateral loads, until failure occurs. The finite element software SAP2000 is used to generate the nonlinear behavior curve through incremental elastic-plastic analysis with concentrated plasticity in the plastic hinges within the structural members. Two building layouts were used in the study, one square and the other is rectangular, with variable number of storey’s and variable column orientation. The results show that the R-Factor increases as the number of storey’s increase, and it attains a maximum value when the loading direction coincides with the strong axes of the columns. The R-factor is minimum when the main quake load coincides with the weak axes of the columns. These results were invariable for both building layouts. Also, it is found that the R-Factor recommended by the seismic design provisions (IBC 2012 for example) may not be conservative for use in buildings with disoriented columns. In fact, it is found that for buildings of 4 floors, the value of R-factor from IBC 2012 is higher than that obtained from the push over analysis. This means that using IBC2012 value of R-Factor would give lower induced seismic forces for design, which may lead to detailing level that does not warrant the realistic R-Factor for the building being designed. The study is only a first step towards scrutinizing the validity of the international building codes for use in Palestine and further research is needed to advance this study. As a future research topic, it is recommended to conduct nonlinear time-history analysis using actual earthquake records in order to compare the inelastic behavior of these buildings to the actual earthquake loads in these buildings.
Effect of Column Orientation on Response Modification Factor (R-Factor) of Reinforced Concrete Frames
(An-Najah National University, 2018-09-20) Zaid, Ahmad Mahmoud
Response Modification factor (R-Factor) is an essential seismic design parameter, which is typically used to describe the level of inelasticity expected in structural systems during an earthquake and is used to reduce the anticipated earthquake load due to the inherent inelasticity of the structure. International building codes provide fixed values for this factor for each category of building system despite the fact that its value depends on the details of the structural system and thus should differ for each building. One of the aspects of buildings in Palestine is their irregularity and this includes the disorientation of columns strong axes in the building plan to suit architectural needs. In Palestine, the international codes are generally applied with little to no guidelines on the validity of these codes to the buildings being designed. To-date, there are no guidelines as to how this R-Factor would change due to the disorientation of main axes of the load-bearing columns in the building. This study comes as a step towards investigating the validity of the code-specified values of the R-factor for framed buildings with disoriented columns. To achieve the above-mentioned goal, pushover analysis is considered as a nonlinear procedure to predict the inelastic behavior of framed buildings, by exposing the structure to increasing lateral loads, until failure occurs. The finite element software SAP2000 is used to generate the nonlinear behavior curve through incremental elastic-plastic analysis with concentrated plasticity in the plastic hinges within the structural members. Two building layouts were used in the study, one square and the other is rectangular, with variable number of storey’s and variable column orientation. The results show that the R-Factor increases as the number of storey’s increase, and it attains a maximum value when the loading direction coincides with the strong axes of the columns. The R-factor is minimum when the main quake load coincides with the weak axes of the columns. These results were invariable for both building layouts. Also, it is found that the R-Factor recommended by the seismic design provisions (IBC 2012 for example) may not be conservative for use in buildings with disoriented columns. In fact, it is found that for buildings of 4 floors, the value of R-factor from IBC 2012 is higher than that obtained from the push over analysis. This means that using IBC2012 value of R-Factor would give lower induced seismic forces for design, which may lead to detailing level that does not warrant the realistic R-Factor for the building being designed. The study is only a first step towards scrutinizing the validity of the international building codes for use in Palestine and further research is needed to advance this study. As a future research topic, it is recommended to conduct nonlinear time-history analysis using actual earthquake records in order to compare the inelastic behavior of these buildings to the actual earthquake loads in these buildings.
Seismic Assessment of Public Schools in Palestine According to International Building Code IBC
(جامعة النجاح الوطنية, 2019-07-22) Adas, Mohammad Omar
It is known that schools in countries need special requirements for implementation issues controlling all needs reaching the best way for safely use to all occupants. Moreover; schools -as they are core of communities- used as shelters in Severity circumstances like wars, damages …etc. Schools have a high degree of importance and focus on their physical status, which means the need to ensure their durability, sustainability and the integrity of all their components, as well as the global practice of using them as shelters in the event of natural disasters Human and various emergencies. The great importance of these facilities - schools - puts us in charge of community, ethics and professionalism beyond personal interests, and it is imperative in the field of engineering and construction design to ensure work to provide maximum care and safety, to stand these important facilities to all risks, for example, Seismic dangers. A great part of existing schools' structures in Palestine have been constructed using the same project details; with our concerning the seismic criteria including site conditions. In this research, we present an engineering scientific study that evaluates the topographic impact and the effect of its changes on seismic behavior and the difference in the design of public-school facilities in Palestine based on Time period of fundamental mode of structure according to codes of practice. Scientifically; It is proven that seismic behavior varies from region to region and from one structure to another according to many variables, mainly the nature of the soil on which the origin will be established. Hence, it is far from right to have the same seismic design for a number of schools located in several different places Terrain and seismic behavior. Different topographies directly affect seismic design factors, system considerations, importance of structure, and structural analysis methods. The study targeted a number of different designs of public schools in Palestine to collect statistical information about the nature of practice in previous years. The statistical data were used to create three school models in three different topographies (Jericho, Ramallah and Qalqilya). And to make the necessary recommendations based on Time period of fundamental mode of structure as a minimum in access to the safety of public schools within several construction systems of the same structure, and the results were obtained and a comprehensive overview of the best means and systems of the construction design of public schools in the occupied Palestinian territories. Several tools were used in local code-based analysis and evaluation, such as SAP program, and the results obtained were verified to ensure the reliability of the program and all its outputs. An interesting result has been found that puts the structural designer on the proper path of the safe structural design, within the necessary hypotheses that develop these structures from the structural aspects. The study also linked some design needs to the correct practice which means linking design to different implementation needs.
Seismic Assessment of Historical Buildings in Palestine Nativity Church as a Case-Study
(جامعة النجاح الوطنية, 2019-07-22) Safiyeh, Ali Abdellatif Ali Abu
This thesis addresses the study of the seismic assessment of historical structures in Palestine, by focusing on general condition and structural stability of The Church of Nativity in Bethlehem, which is the most valuable structure over the world, because it is earliest Christian structures, and the birth place of Jesus. The work of this thesis can be divided into the following main phases: a focus on the one case study with its properties, review of the state of art, preparation and calibration of a 3D finite element models, and the structural analysis to assess the seismic behavior of the Church. The assessment was done by using the static pushover and dynamic time history methods and the results of these analyses are studied in terms of the generated cracks propagation in each direction, effects of relative displacement of masonry blocks and progressive collapse analysis for the structures elements. In particular, the results of the pushover analysis carried out, conclude that the transversal direction is the most vulnerable and the damage concentrates at the main lateral (longitudinal) walls, mainly at the south and north alignment walls, also at the vaults and at the connections of the vaults to the apses. On the other hand, the dynamic analysis presented similar conclusions in terms of structural performance. Furthermore, it allowed conclude that for the considered earthquake, the relative displacement of adjacent masonry blocks (RDAMB) indicates the locations of failure, and the prediction of reasons. Furthermore, the progressive collapse technique is able to predict the critical regions, and effect of rock falls in masonry walls of the structure.
Influence of Bearing Non-Reinforced Parameter Walls with Stone Cladding on Fundamental Period Computation
(جامعة النجاح الوطنية, 2019-08-21) عمر حلاحلة, محمد
ينتشر في فلسطين نمط البناء باستخدام التكسية الحجرية الطبيعية وعادةً ما تُنشأ هذه الجدران باستخدام طبقة من الخرسانة غير المسلحة، أو من الطوب المفرغ . جرت العادة أن يتم إهمال هذه الجدران من التحليل الإنشائي، حيث تعتبر هذه الجدران جدراناً غير حاملةً، حيث تكون الفرضية المستخدمة في النمذجة اعتبار الإطارات والجدران المسلحة كعناصر إنشائية، ويتقصر تمثيل الجدران غير المسلحة على إضافة وزنها للنموذج الرياضي، دون إبداء أي مساهمة في مقاومة القوى الأفقية أو العمودية. إن تجاهل تضمين هذه الجدران في عملية التحليل والتصميم يجعل التنبؤ بسلوك المنشآت محل شك، كما ويُنذر بخطورة تصرف المنشآت حين تعرضها لقوى الزلازل. إن فهم سلوك المنشآت في الزلازل يعتمد بشكل رئيس على قيمة زمن التردد الأساسي. إن تطوير طرق نمذجة تعمل على رفع دقة التنبؤ بزمن التردد الأساسي خطوة أساسية ومهمة في الخطوات السليمة لتحليل وتصميم أي منشأ. تهدف هذه الدراسة إلى اقتراح نموذج رياضي يمكن الوثوق به لتحسين دقة قيمة زمن التردد الأساسي التي يتم احتسابها، حيث إن المتعارف عليه في التحليل الإنشائي المستخدم في فلسطين هو إهمال هذه الجدران إنشائياً والتعامل معها بصفتها تساهم في الوزن فقط. تهدف هذه الدراسة إلى تسليط الضوء على خطورة إهمال هذه الجدران في التحليل الإنشائي، وإعطاء توصية بضرورة نمذجتها باستخدام إحدى المعادلات المتاحة التي تستبدل الجدران بعنصر مكافئ، الأمر الذي من شأنه أن يرفع دقة التحليل الإنشائي وعليه يُقلل المخاطر المتوقعة عند حدوث الزلازل.
Improving Ductility Behavior of Sway-Special Exterior Beam-Column Joints Using Ultra-High Performance Concrete.
(جامعة النجاح الوطنية, 2020-01-21) رائد فايز أبو سفاقة, فايز
إن المفاصل الخرسانية هي أكثر العناصر الحرجة في المنشأ. لذلك فإن كودات التصميم ومن ضمنها الكود الأمريكي للخرسانة يوفر متطلبات حازمة لتصميم العقد الخرسانية في المنشآت ذات التمايل الخاص لمنع اتهيارها مع درجة ممطولية منطقية تحت تأثير الأحمال الزلزالية. على كل حال, إن تجمع العديد من أنواع الستليح الطولي والعرضي يسبب مشاكلا في التنفيذ. هذا البحث يهدف إلى تطوير أداء ممطولي للعقد الخرسانية الخارجية في المنشأت ذات التمايل الخاص مع استغناء كامل عن التسليح العرضي وذلك باستخدام مادة الخرسانة فائقة الأداء (UHPC). تم استخدام الخرسانة فائقة الأداء من صنف ب وتحتوي على ما نسبته حجميا 2% من الألياف الفولاذية كما تم اعتمادها من مؤسسة الطرق الفدرالية (FHWA). تم عمل البحث بالتحليل العددي باستخدام برنامح العناصر المحدودة أبكس (ABAQUS). تم استخدام هذا البرنامج لبناء نموذج محاكاة ثلاثي الأبعاد لعقدة خرسانية خارجية و التحقق من نتائج النموذج باستخدام بيانات اختبارية منشورة. بعد ذلك, تم عمل مصفوفة نماذح باستخدام المتغيرات الرئيسية المؤثرة على تصرف العقد الخرسانية. هذه المتغيرات تتصمن النسبة بين العمق الكلي لمقطع الجاسئ بالنسبة للعمق الكلي لمقطع العمود ( من 0.6 إلى 1.6 مع 0.1 زيادة), نسبة الحمل الرأسي (0.25 و 0.5) ونسبة التسليح الطولي في العمود (1% و 2%). تم استخدام نتائج المحاكاة لمصفوفة النماذج للمقارنة بين تصرف العقد الخرسانية ذات التفاصيل للتمايل الخاص مع العقد الخرسانية المقواة باستخدام الخرسانة فائقة الأداء في مدى القوة, الممطولية و نوع الأنهيار الحاصل. إن النتائج قد أكدت إمكانية استخدام الخرسانة فائقة الأداء في تقوية العقد الخرسانية في المنشآت ذات التمايل الخاص بدون فقد في القوة والممطولية. زيادة على ئلك, إن العقد الخرسانية المقواة بالخرسانة فائقة الأداء أظهرت تفضيلا في الأداء على الحد النسبي الأدنى بين عزم العمود وعزم الجاسئ مع بعض الانتهاكات في هذه النسبة. لفحص مدى هذه الانتهاكات, تم تقييم عزم العمود باستخدام النموذج الذي اقترحه ساتسيوجلو ورازفي (Saatcioglu and Razvi 1992) للخرسانه المحصورة. بعد ذلك, تم حساب النسبة بين عزم العمود المحصور إلى عزم العمود غير المحصور (حسب الكود الأمريكي ACI). لقد وجد أن هذه النسبة تتراوح بين 1.02 و1.20 وذلك يعتمد على نسبة الحمل الرأسي ونسبة التسليح الطولي في العمود. هذه النسب مرتبطة بأبعاد وتفاصيل التسليح للعمود المستخدمة في هذا البحث. ختاما, تم استخدام النموذج التحليل الذي اقترحه الأسطا وخان (Alosta and Khan 2017) لتقييم سعة العقد الخرسانية الخارجية الخالية من التسليح العرضي لقوى القص في تقييم سعة العقد الخرسانية المدعمة بالخرسانة فائقة الأداء وربطها بنسبة الألياف الفولاذية المثلى لاستخدامها بالمادة. بشكل مختصر, هذا البحث يشير إلى إمكانية استخدام الخرسانة فائقة الأداء في تقوية العقد الخرسانية الخارجية ذات التمايل الخاص على الحد النسبي الأدنى لعزم العمود المحصور إلى عزم الجاسئ مع استخدام النسبة الحجمية المثلى للألياف الفولاذية حسب قوة القص المطلوبة.
Effects of Structural Links Between Building and Ground Cut on its Seismic Performance
(جامعة النجاح الوطنية, 2020-10-14) نواف قدادحة, عبد الحميد
يشكل المهندس الانشائي وعالم الزلازل المفتاح الأساسي لضمان تصميم آمن للمنشآت لأحمال الزلازل، الا أن التطبيق الشائع هو أن يبدأ المهندس المعماري عملية التصميم للمبنى، وعليه يحدد العديد من الأمور التي لها علاقة بتكوين المنشأ والتي لها أثر رئيسي في أداء المنشأ واستجابته لأحمال الزلازل. يمكن تعريف تكوين المبنى بحجم المنشأ وشكله في الأبعاد الثلاثة وشكل وتوزيع العناصر الانشائية، واتصاله مع المباني المجاورة أو الأرض الجانبية، وطبيعة ومواقع العناصر الانشائية وغير الانشائية التي تؤثر بالعادة على تصرف المنشأ تحت تأثير الاحمال المختلفة. هذا البحث يشكل اضاءة على هذه المباني التي تحوي بعض هذه التكوينات التي تمنع المبنى من التصرف بحرية تحت تأثير الأحمال الجانبية. المباني الخاضعة للدراسة تحوي وصلات انشائية مع الأرض المجاورة من جهة واحدة، تمنعها من الحركة باتجاه القطع الصخري فيما تبقى حرة الحركة في الاتجاه الاخر. نظرا لتعقيد وتفرد كل نموذج من هذه المباني، فإن العديد من العوامل تؤثر على أداء المبنى تحت أحمال الزلازل ولذلك يتوجب دراسة هذه العوامل منفردة. لتطوير رؤية واضحة لأداء هذه المباني تحت تأثير احمال الزلازل، تمت دراسة منشئات اطارية بسيطة تحوي وصلات تحد من حركتها الجانبية باتجاه واحد وتحليلها تحت تأثير أحمال مختلفة ومقارنتها بنفس النماذج حرة الحركة، وذلك بواسطة برنامج SAP2000 كأداة رئيسية خلال هذه الدراسة ، بعد تأكيد النتائج بمقارنتها بالمعادلات النظرية للأحمال الموجية المتناسقة ، والتأكد من حسابات التردد الطبيعي للمنشأ بطريقة Rayleigh . لغرض هذه الدراسة، تم اعتماد طريقتين للقياس تم تطبيقهما على كل الاحتمالات لمكان الوصلات بالنسبة للمنشأ الإطاري بنماذج بدرجة حرية واحدة واثنتين وثلاثة: • طريقة طيف الاستجابة " response spectrum approach “: وعليه تم تطبيق حمل دوري جيبي متناسق يحوي ترددات من 0.1 ثانية – 2 ثانية بفرق درجات 0.1 ثانية وبنفس السعة على كل النماذج التي تحوي نفس التكوين بترددات طبيعية مختلفة تتراوح بين 0.1 ثانية – 2 ثانية. وبناء عليه تم قياس الازاحة والازاحة النسبية واظهارها في رسومات بالنسبة لتردد الأحمال. وعليه يتوضح أن النماذج المحدودة الحركة تبدي استجابة أكبر لبعض ترددات الأحمال الموجية. • طريقة استجابة التردد " frequency-response approach": وعليه يتم تطبيق حمل موجي بتردد واحد من 0.1 ثانية – 1.6 ثانية منفردا على النماذج بزمن موجي طبيعي محدد للنموذج حر الحركة. وعليه تظهر رسومات النتائج للإزاحة والازاحة النسبية التغير في الزمن الموجي الطبيعي للمنشئات محدودة الحركة وتقارن الاختلاف في الاستجابة القصوى بين النماذج الحرة والمحدودة. نسبة الزيادة في الازاحة النسبية بين النماذج حرة الحركة ومحدودة الحركة موضحة في الرسومات القياسية بالنسبة لزمن التردد للأحمال والزمن الطبيعي للمنشأ. تم اعتماد النماذج بمقارنتها مع الدراسات السابقة ومن ثم دراسة أثر تغير خصائص الوصلات وعلاقتها بأداء المنشأ محدود الحركة. وعليه تم عمل رسومات نظرية بسيطة لتوقع أثر الوصلات الانشائية على النماذج المختلفة. بعد إتمام هذه الدراسة، يتضح أن الوصلات الانشائية بين المبنى والأرض المجاورة لها أثر كبير على زمن التردد الطبيعي للمنشأ وعلى الجساءة الأفقية اللحظية للمباني الاطارية. وعليه تشير نتائج هذه الدراسة أن تصميم المبنى لنمط توزيع قوى القص بناء على استجابة المبنى حر الحركة يمكن أن تكون غير واقية للتقليل من حدوث أو اتساع الضرر في المبنى الإطاري الذي يتعرض لقدر أكبر من التشوه الغير مرن نتيجة الإعاقة في مدى الازاحة الأفقي.
The Effect of Earthquake Vertical Component on the Response of Cantilever Beams in Multi-Storey Reinforced Concrete Building
(An-Najah National University, 2021-07-15) البيك, أحمد محمود سليم
Structural design to withstand seismic loading is mainly governed by horizontal ground motion, and the effects of vertical ground motion have long been considered insignificant or secondary. However, an emerging evidence indicates that vertical ground motions have significant destructive potential, especially under specific site conditions. Evidence suggests that the vertical component of ground motion is more important than previously thought, especially for events close to the fault and when buildings have a cantilever beam. The purpose of this thesis is to investigate the effect of vertical component of earthquake on the response of cantilever beams of multi-story reinforced concrete building. Finite Element (F.E) analysis using available commercial software (Etabs) is used to investigate the effect of vertical component of earthquake on cantilever beams in 2D and 3D models with different cases. The models are verified by comparing the periods of models to hand calculation of single degree of freedom. Many different models have been constructed with different cases. The results show that the equivalent static equation in ASCE 7-16 (0.2SDS D) code can be considered to be conservative for structures with seismic design category (B). A proposed equivalent static equation is suggested to account for the effect of vertical components of earthquake on the response of cantilever. The proposed equation is generally conservative for most of the cases with different seismic deign categories (B, C, D).
USING ULTRA-HIGH PERFORMANCE CONCRETE FOR ELIMINATING SOFT AND WEAK STORY IRREGULARITIES IN SPECIAL REINFORCED CONCRETE MOMENT RESISTING FRAMED STRUCTURES
(An Najah National University, 2022-02-27) Mohammad Sharawneh, Ali
Multistory buildings are common in Palestine and sometimes are built with a ground floor that has an open space or is higher than the rest floors for commercial purposes. Therefore, the soft and weak story irregularities may occur on the ground floor. This research aims to eliminate the soft or weak story irregularities in the design stage without affecting the architectural requirements by changing the columns material from normal strength concrete (NSC) to ultra-high performance concrete (UHPC) in the soft or weak story. To quantify the effect of the material switch from NSC to UHPC on the column strength and stiffness, a parametric study using sectional stress analysis is performed. Overall, 216 NSC and UHPC columns cross-sections are analyzed under the following parameters: axial load levels, longitudinal reinforcement ratio, cross-section width, and cross-section depth to width ratio. The effectiveness of using UHPC on the column stiffness is studied where the change in the flexural rigidity is represented using the ratio of the effective flexural rigidity (EIe) of UHPC columns to NSC columns. Also, the validity of cracking analysis modifiers of NSC columns is established for UHPC columns. The effectiveness of using UHPC on the column strength is investigated using the ratio of the moment capacity of the UHPC columns to NSC columns. After that, the adequacy of the column shear capacity is checked, and found that the lateral strength of the UHPC column is still controlled by the moment strength. Moreover, regression analysis is performed for the parametric study results to create equations that predict the increase in the sectional stiffness and strength of the columns. Finally, a 3D sway special moment-resisting framed building is used as a case study to confirm the sectional analysis results and to investigate the frame's overall behavior before and after using UHPC in the soft/weak story columns. The frame is designed according to ASCE7-16 and ACI318-19 and has both an extremely soft story and weak story irregularities on the ground floor. Nonlinear static analysis (pushover) is performed for the frame using SAP2000. The frame analysis results agree well with the parametric study results. In addition, the overall behavior of the frame is enhanced when the UHPC is used since the displacement and the plastic hinges do not concentrate on the soft/weak story. In summary, switching the columns material in the soft/weak story from NSC to UHPC can be safely used to eliminate the soft/weak stories irregularities at the design stage without changing the architectural or functional restriction.
EFFECT OF HORIZONTAL COMPONENT OF EARTHQUAKE ON HANGED ROOFS LOADED WITH HEAVY WALLS
(2022-05-17) Motaz Mohammad Ibrahim Abu Aladas
Background: It can be clearly seen that most of today's buildings contain cantilevers, and in most cases these cantilevers are loaded by moderate to heavy masonry loads. The effect of earthquake components on the loaded cantilevers is not clearly described in the design codes, which is a research interest. The main objective of this research is to understand the behavior of cantilevers when subjected to a horizontal earthquake component under different conditions, since the codes do not give the necessary attention to the weakness of cantilevers and their effects on the vulnerability of structures. Methods: Some of the most sensitive properties of cantilevers were selected to study the behavior of cantilevers and their effects on the response of structures. The literature review included the investigation and collection of information on the most important factors affecting the behavior of cantilevers, such as direction, length, and loading of cantilevers. In order to study each of these parameters, a series of models with specific parameters were analyzed in the Extended 3D (Three Dimensional) Analysis of Building Systems (ETABS) software after being verified and adopted. Results: the results of the forces and stresses in the presence of masonry have an increase of 152% for axial forces and 13.4% for shear forces and bending moments due to the horizontal component of the earthquake. On the other hand the vertical earthquake component does not have an axial effect on the cantilevered sections and the effect of axial stress due to the horizontal earthquake component on the shear capacity of sections does not exceed 2% for beams and 1% for ribs. And critical cantilever length to successive span length can reach 22% in some cases. Conclusion: The research indicate that it’s recommended to avoid an irregular structure to minimize the inherent torsion. On the other hand, a regular structure, where the center of mass coincides with the center of stiffness, may have a torsional response in some cases. Research has also shown that the horizontal earthquake component does not cause a significant decrease in shear capacity and that the vertical earthquake component is not worse than the horizontal one. Keywords: loaded cantilever, torsional mode, horizontal earthquake component, vertical earthquake component, site seismicity.
EFFECT OF SETBACK ON THE ELASTIC DYNAMIC RESPONSE OF REINFORCED CONCRETE FRAMED STRUCTURES
(2023-01-03) Aseel Jamal Fareed Badran
Background: The collapse due to a seismic load typically starts at locations of the weakness of the structural system in the building. The weaknesses often occur due to a discontinuity in mass, strength, or stiffness between two adjacent floors. A well-known type of vertical geometric irregularity in structures is a setback, defined as a sudden decrease in the building's lateral dimension at a certain height. Problem Statement: The ASCE 7:16 code sets limitations on the Linear Equivalent Static method (LES), where it does not permit the use of this method for some types of irregularity, including setback irregularity, which are located in seismic design category (SDC) D, E and F. On the other hand, the LES method can be used in SDC B and C without restrictions. The code permits using the Modal Response Spectrum (MRS) and the Time History Analysis (THA) for all buildings without limitations on the SDC. Objectives: This study examines the effect of a setback on the elastic seismic response parameters of reinforced concrete framed structures, such as the fundamental period, the seismic base shear, the inter-story distribution of shear forces, and story drift. Finally, this study examines the solution to the problem of the code restrictions on the use of the LES method. Methodology: Buildings with Perimeter masonry walls with different setback ratios at different levels were analyzed using the commercial software ETABS 2016 according to the provisions of ACI318-14 and ASCE 7:16. The analysis was done using the LES method, MRS method, and THA method. The outcomes of the elastic response of the setback buildings were compared to similar buildings but without setbacks, in addition to comparing the results of the analysis methods used in this study. Conclusion: Based on the results, the vertical distribution of shear force from LES was modified depending on the THA method results. This modification allows the use of the LES method in various SDCs. Keywords: Linear Equivalent Static Analysis (LES); Modal Response Spectrum (MRS); Seismic Response; Setback structures; Time History Analysis (THA).
EFFECT OF THE BUILDING ASPECT RATIO ON RESPONSE MODIFICATION FACTOR FOR REINFORCED CONCRETE MOMENT RESISTING FRAMES
(2023-07-02) Dana Issam Abdul Kareem Nassar
Abstract The response modification factor (R) is one of the essential factors in seismic design and is used to define the nonlinear behavior of buildings during an earthquake. International codes such as IBC 2016 provide a constant value for “R” for a particular structural system. However, the value of "R" may change based on parameters including zone factor, soil site class, aspect ratio of the frame, column orientation, and type of slabs. This study investigates the effect of building aspect ratio on the value of "R". In addition, it checks if the values of the R factor recommended by the IBC-2016 code are conservative. A single cycle for calculating the R factor is applied by pushover analysis (nonlinear response analysis) to achieve this goal. It was applied to many 3-D intermediate moment-resisting frame systems with different aspect ratios as the key parameter and different seismic zone factors and sites as secondary parameters to determine the behavior of the frame with increasing lateral force until collapse. The researcher selected 30 cases with different aspect ratios, zone factors, site classes, and building plans. Then, the ETABS2016 program is used to design and analyze (elastic analysis) the 3-D frames as per previous code requirements. Finite element software (ABAQUS) performs the nonlinear analysis via incremental Elasto-Plastic analysis. The reinforced concrete elements are presented in the program as line elements. Afterwards, the Xtract program is used to evaluate the inelastic properties of the sections fed to ABAQUS for the frame analysis. The obtained results of "R" are compared to the values suggested by international codes (IBC 2016). The results demonstrate an influence of the aspect ratio, zone factor, and site class on the R factor. An equation was derived to calculate the R factor through the aspect ratio of the building and the seismicity of the region. Consequently, the computed values for the cases depending on the pushover curve are larger than or equal to those recommended by the IBC2016 code. So, the international code is conservative, in term of the total base shear, force because it considers the period of the building in the calculation of the R factor. However, further ductility investigation is needed as the required R values are higher than code ones. Keywords: Nonlinear static analysis; ABAQUS program; response modification factor

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