Structural Engineering

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    (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.
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    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.
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    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.
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    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.
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    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.