Structural Performance of High Rise Building with High Strength Concrete.pptx

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1. Structural Seismic Performance of High-Rise Buildings with High-Strength Concrete and Construction Cost-Effectiveness Analysis in Bangladesh. Mohammad Murad Hossain M.Sc. In Civil Engineering ID- 23115009

2. Although several factors contribute to the development of high-rise building construction, economics remains the most significant. The rapid increase in land costs in metropolitan areas, along with the ongoing availability of high-strength concrete materials at competitive prices, has greatly accelerated high-rise construction. This growth in the number of tall buildings indicates that the demand for high-strength construction materials will continue to rise. While our understanding of the performance of high-strength materials is well established, there is limited information on the relationship between economics and the performance of high-strength high-rise buildings under earthquake loading. This is particularly relevant because earthquake resistance is a critical aspect of designing many tall buildings (e.g., Laogan and Elnashai , 1999). Additionally, current seismic design provisions, such as ASCE 07-10 (2010), were developed based on extensive observations from past earthquakes and test results for structures designed with normal-strength materials. This highlights the necessity of choosing the most efficient and cost-effective materials for high-rise buildings to mitigate the risks posed by natural hazards to these valuable economic and human assets. Introduction

3. 1. the higher strength and stiffness of high-strength concrete (HSC), it also offers better durability compared with normal-strength concrete (NSC) 2. the unit weight of concrete is marginally affected with increasing compressive strength, while a notable reduction in the structure weight is achieved by reducing the cross sections of HSC members. 3. This weight reduction is important in seismic regions since earthquake forces are directly proportional to the mass. 4. HSC's main economic advantage is its higher structural engineering properties per unit cost, which gives it an economic edge over NSC. 5. The use of smaller cross-sectional HSC vertical elements, particularly in the lower stories of high-rise buildings, allows for a reduction in the steel component and increases the area of usable floor space, bringing in substantial returns from the investment. HSC in the high-rise building construction.

4. OBJECTIVE OF THE STUDY 1.To examine the behavior of multi-story buildings with different graded high strength concrete , as well as the results for the seismic analysis. 2. By performing dynamic analysis, the structure was analyzed in terms of base shear, displacements, drifts, story stiffness, and story forces, by modifying the stiffness and concrete grade of the structure along its height in same seismic zones of Bangladesh

5. A. Three-dimensional modeling and analysis of high-rise structures are computationally demanding, particularly with the wide range of reference buildings and input ground motions considered in the present study B. A comparative cost assessment for the superstructure of the five reference structures is performed with respect to reinforcing steel, concrete and formwork to determine the impact of changing material strength on the cost-effectiveness. Study Methods

6. The five models with different compressive strengths ( 55 , 70, 85 Mpa ) and two combinations of 55-70 Mpa and 75-85 Mpa ) are analyzed by Etabs Software. They are defined as structural elements (beams, columns, and plates) for which proposed sections of (300x600, 250x900) mm in main beams, (250x600) mm in secondary beams, (600x1200) cm in central columns, (375x900, 400x600, 600x1200) mm in non-central columns and plates with (150mm, 180mm) of thickness, all with a high-strength concrete. Structural Model

7. For loads of the entire structure, national standards (BNBC) will be considered in the models. A spectral modal analysis is performed to evaluate these models, granting 100% of the dead load plus a percentage of live load and live roof load, depending on the type of building and its comparison with the maximum allowable drift of 0.007. Design Citeria

8. This research evaluates the non-linear response of structural models taking into account the variation of the mechanical strength of concrete, with the aim of obtaining structures with greater resistance capacity, a reduction of the own weight and the decrease of its cost in the face of a lower volume of flexo -compression and cut, so it will have to be verified with a non-linear analysis and seismic performance. Structural Analysis

9. The use of high-strength concrete in flexural elements enhances rotational ductility, improves column capacity, and increases the stiffness of beam-column joints. In this investigation, we aim to analyze the seismic behavior concerning the increase in concrete strength. To achieve this, we will reduce the sections of the structural elements in each structural model, as the compressive strength ( f’c ) is increased. This will allow us to assess the improvements in the non-linear response resulting from the variation in concrete strength. Usefulness of High Strength Concrete

10. Despite the overwhelming strength properties and design flexibility of HSC construction, its deployment and the achievement of its full potential strength are hindered by several challenges. A particularly significant issue is the low water-to-binder (w/b) ratio inherent in HSC mixtures (Bentz et al. 2009; Dushimimana et al. 2021; Ye et al. 2019), which can lead to microcracking and shrinkage, preventing the realization of its full mechanical and durability properties. Limitation of HSC

11. Response spectrum analysis (RSA) is a method for estimating how a structure will respond to dynamic events, such as earthquakes. It's a linear-dynamic statistical analysis that uses a structure's natural vibrations to calculate the maximum force it might experience during a seismic event.  Response Spectrum Analysis

12. Pushover analysis is a static procedure that employs a simplified nonlinear technique to estimate the seismic deformations of structures. This method can demonstrate how progressive failure occurs in buildings and identify the mode of final failure. Additionally, pushover analysis can predict potential weak areas within the structure by tracking the sequence of damage to each structural member, using a method known as 'hinges.' Push Over Analysis

13. TABLE: Diaphragm Center Of Mass Displacements       Story Diaphragm Output Case Case Type Step Type UX UY           mm mm Story17 D3 EQX LinStatic 76.626 1.759 Story17 D3 EQY LinStatic 2.095 68.457 Story17 D3 RS X LinRespSpec Max 48.905 12.508 Story17 D3 RS Y LinRespSpec Max 11.085 39.39 Story17 D3 0.9 DL + 1 Eq X Combination 78.629 -5.723 Story17 D3 0.9 DL + 1 Eq Y Combination 4.098 60.976

14. TABLE: Base Reactions           Output Case Case Type Step Type Step Number FX FY         kN kN 0.9 DL + 1 Eq X Combination -4825.5567 0.9 DL + 1 Eq Y Combination -0.000001618 -4825.5566 1.2 DL + 1.6 Lr + 0.8 Wx Combination Max -8.978E-07 3146.0533 1.2 DL + 1.6 Lr + 0.8 Wx Combination Min -2000.0348 -4194.7377 1.2 DL + 1.6 Lr + 0.8 WY Combination Max 2000.0348 1.2 DL + 1.6 Lr + 0.8 WY Combination Min -1500.0261 -4194.7377 EQX LinStatic -4825.5567 EQY LinStatic -0.000001094 -4825.5566 RS X LinRespSpec Max 3269.7591 854.3538 RS Y LinRespSpec Max 854.3538 3178.9268

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