CE 72.52 - Lecture 8a - Retrofitting of RC Members

Shear walls are preferred in seismic regions because they are very effective at resisting lateral forces during earthquakes. Shear walls are vertical structural elements designed to transfer seismic forces throughout the height of the building. They provide large strength, high stiffness, and ductility. Shear wall buildings have performed much better during past earthquakes compared to reinforced concrete frame buildings. Some key advantages of shear walls include good earthquake resistance when designed properly, easy construction, reduced construction costs, and minimized damage to structural and non-structural elements during seismic events.

Seminar on Design of Tall Buildings: Trends and Advancements for Structural Performance, November 2016

The document discusses modeling a reinforced concrete building frame using STAAD.Pro and ETABS software. It describes how to model the beams, columns, slabs, walls, stairs, and foundations. Initial member sizes are determined based on architectural requirements and design formulas. The building is modeled by framing the beams and columns. Loads like self-weight, floor loads, and wall loads are applied to the frame. Material properties of concrete are also specified. The document provides guidance on modeling the structural elements and applying loads in STAAD.Pro and ETABS to analyze the building frame.

This document provides step-by-step instructions for performing a modal response spectra analysis and design of a 10-story reinforced concrete building model in ETABS. It describes opening an existing model, defining response spectrum functions and cases based on IBC2000 parameters, running a modal analysis and response spectral analysis, and reviewing results including mode shapes, member forces, and designing concrete frames and shear walls. The objective is to demonstrate modal response spectra analysis and design of the building model according to IBC2000 seismic code provisions.

Introduction to Capacity-based Seismic Design by Dr. Naveed Anwar of Asian Institute of Technology (AIT), Thailand

Presented at Design of Tall Buildings and Affordable Housing ,12 March 2017, Sultan Qaboos University, Muscat, Oman

This document provides an introduction to the course CE 72.52 Advanced Concrete. It discusses the key roles of structural engineers in creating safe built environments. It also outlines some of the main topics that will be covered in the course, including material behavior, section design, member design, ductility, seismic detailing, and prestressed concrete. The document includes several images related to reinforced concrete elements, structural analysis and design processes, and limit state design concepts. It provides an overview of the structural design process from modeling and analysis to detailing and drafting.

Pushover analysis has been in the academic-research arena for quite long. The papers published in this field usually deals mostly with proposed improvements to the approach, expecting the reader to know the basics of the topic... while the common structural design practitioner, not knowing the basics, is left out from participating in those discussions. Here I’m making an effort to bridge that gap by explaining the Pushover analysis, from basics, in its simplicity. A write up on this topic can be found at http://rahulleslie.blogspot.in/p/blog-page.html, though does not cover the full spectrum presented in this slide show.

This document discusses various techniques for retrofitting concrete structures to make them more resistant to seismic activity and other natural hazards. It defines retrofitting as modifying existing structures to increase resistance. Key techniques mentioned include adding new shear walls, steel bracing, column and beam jacketing with steel or concrete, base isolation using seismic isolators, mass reduction by removing floors, and wall thickening. The document also discusses challenges in retrofitting and standards from Indian codes for earthquake-resistant design. The conclusion emphasizes that retrofitting has matured but expertise is still lacking, and optimization is needed to determine the most cost-effective technique for a given structure.

Shear walls are vertical reinforced concrete walls that resist lateral forces like wind and earthquakes. They provide strength and stiffness to control lateral building movement. Shear walls are classified into different types including simple rectangular, coupled, rigid frame, framed with infill, column supported, and core type walls. Design of shear walls involves reviewing the building layout, determining loads, estimating earthquake forces, analyzing the structural system, and designing for flexural and shear strengths with proper reinforcement detailing. The behavior of shear walls under seismic loading depends on their height to width ratio, with squat walls experiencing more shear deformation and slender walls undergoing primarily bending deformation.

A full explanation for the lateral resisting system: CONCRETE MOMENT RESISTING FRAME-STEEL MOMENT RESISTING FRAME- COMPOSITE MOMENT RESISTING FRAME

This document discusses shear wall analysis and design. It defines shear walls as structural elements used in buildings to resist lateral forces through cantilever action. The document classifies different types of shear walls and discusses their behavior under seismic loading. It outlines the steps for designing shear walls, including reviewing layout, analyzing structural systems, determining design forces, and detailing reinforcement. The document emphasizes the importance of properly locating shear walls in a building to resist seismic loads and minimize torsional effects.

This document discusses modeling and analysis techniques for bridge superstructures and substructures. It covers modeling bridge decks using various element types including beam, grid, plate-shell, and solid models. It also discusses modeling bridge piers and foundations using solid elements, beam elements, or springs to represent soil-structure interaction. The document emphasizes the importance of modeling both superstructure and substructure together to accurately capture their interaction, and discusses challenges like modeling bearings and soil.

Presented at International Conference on Structural Engineering- 2015 (24-26 August 2015, Colombo, Sri Lanka)

This document analyzes the seismic response of regular and irregular buildings with vertical irregularities using STAAD.Pro software. Six building models are analyzed - three regular buildings with stepped, inverted-T, and U-shaped vertical irregularities, and three irregular (H-shaped plan) buildings with the same vertical irregularities. Response spectrum analysis is used to determine maximum displacements, base shear, frequencies, and time periods. Results show irregular buildings have higher displacements and lower frequencies than regular buildings. The regular building with a U-shaped vertical irregularity performed the worst with the highest displacements. In conclusion, regular buildings performed better seismically than irregular buildings with vertical irregularities.

This document discusses the behavior of composite slabs with profiled steel decking. It presents information on: 1) Composite slabs that use profiled steel sheets as permanent formwork and tensile reinforcement, allowing for 30% reduced concrete and lower structural weight. 2) The profiled steel decking used which is thin-walled, cold-formed sheets meeting ASTM and IS standards with a galvanized coating. 3) Three slabs - plain concrete, bar reinforced, and steel fiber reinforced - were tested for negative bending capacity, with the fiber reinforced slab showing over a 2.5x increase in load capacity compared to plain concrete.

The document discusses the strut-and-tie approach for analyzing concrete structures. It begins with background concepts such as Bernoulli's hypothesis, St. Venant's principle, and the lower bound theorem of plasticity. It then discusses how axial stresses, shear stresses, and the interaction of stresses affect concrete sections. The document outlines the ACI approach to shear-torsion design and provides equations from ACI 318 for calculating the concrete shear capacity. It introduces the concept of modeling concrete as a truss system and compares this to flexural behavior in beams. The strut-and-tie method is presented as a unified approach for considering all load effects. Guidelines are provided for developing an appropriate strut-and-tie model and

An Introduction to ABAQUS CAE

The document discusses enhancing the seismic resistance of structures through retrofitting existing buildings. It notes that 60% of India's landmass is prone to earthquakes. Popular techniques to strengthen structures include adding shear walls, braces, seismic dampers, and base isolation devices. Retrofitting proves economically beneficial, costing 15-20% of the total structure cost to strengthen it and allow residents immediate shelter rather than replacing the building entirely. The conclusion emphasizes that preparing structures for disasters through techniques like retrofitting can help people live happily and safely.

This document discusses the use of textiles in earthquake prevention. It notes that masonry structures and soil embankments are vulnerable during earthquakes due to inability to withstand dynamic loads and risk of landslides. Multifunctional textile structures are being developed to retrofit existing buildings and earthworks. Different textile materials discussed that can be used include fiber reinforced polymers, carbon fiber reinforced concrete, aramid fibers, and glass fiber. Applications described are using fiber reinforced polymer plates and wrapping to strengthen concrete, aramid fiber sheets to retrofit walls, and base isolation systems to protect structures during seismic events.

Tabitha G presents on retrofitting existing structures using fibre reinforced polymer (FRP) composites. FRP composites involve reinforcing fibres like carbon, glass or aramid embedded in a polymer resin matrix. Retrofitting techniques involve bonding the FRP composites to the exterior of structures to improve their strength. The process involves surface preparation, applying the FRP laminates, and curing. FRP retrofitting provides benefits like increased strength, corrosion resistance and durability. It can be used to reinforce structures in transportation, construction, marine and other fields, though specialized skills are required and it may not be suitable for all structures.

It contains details of retrofitting techniques and their application in various aspects in historical monuments. It would help to protect several heritage structures from the devastating effect of the earthquake. Some applications are also helpful too counter act the severe effect of the wind load. There are many historical heritages especially in India, are reopened to the public after being retrofitted and renovated.

The document discusses repair and rehabilitation of concrete structures. It describes various causes of distress in concrete structures including structural causes, errors in design/construction, chemical reactions, and weathering. It then outlines the evaluation process for repair projects, including visual inspection, non-destructive testing, and laboratory testing to determine the extent of damage and appropriate repair methods. Specific causes of reinforcement corrosion like cracks, moisture, and concrete permeability are explained along with remedial measures.

The document provides guidelines for repair and rehabilitation of existing reinforced concrete buildings. It discusses causes of concrete deterioration like permeability, aggressive agents, and condition surveys. Non-destructive tests are recommended to evaluate concrete quality, cracking, and corrosion. The approach involves identifying deterioration causes, assessing damage extent, and selecting appropriate repair materials and methods to rehabilitate structures in a systematic and cost-effective manner.

The document discusses the design of columns in concrete structures. It covers several topics related to column design including: member strength and capacity versus section capacity, moment magnification, issues regarding slenderness effects, P-Delta analysis, and effective design considerations. The key steps in column design are outlined, including determining loads, geometry, materials, checking slenderness, computing design moments and capacities, and iterating the design as needed. Factors that influence column capacity such as slenderness, bracing, and effective length and stiffness are also described.

This document discusses material behavior and properties that are important for structural analysis and design. It defines various types of material stiffness, from material stiffness to cross-section stiffness to member and structure stiffness. It also discusses stress-strain relationships and different material models, including linear elastic, nonlinear elastic, plastic, and viscoelastic models. Finally, it covers key material properties like strength, stiffness, ductility, time-dependent behavior, damping properties, and how these properties depend on the material composition and loading conditions.

The document discusses the design of coupling beams in three categories based on aspect ratio and shear demand: 1) Coupling beams with an aspect ratio greater than 4 are designed as special moment frame beams with conventional reinforcement. 2) Coupling beams with an aspect ratio less than 2 and shear demand greater than a threshold are designed as diagonally reinforced beams. 3) Other coupling beams can be designed as either special moment frame beams or diagonally reinforced beams.

This document provides an overview of member behavior for beams and columns in seismic design. It discusses the types of moment resisting frames and the principles for designing special moment resisting frames, including strong-column/weak-beam design, avoiding shear failure, and providing ductile details. Beam and column design considerations are covered, such as dimensions, reinforcement, and shear capacity. Beam-column joint design is also summarized, including dimensions, shear determination, and strength.

This document provides information on ductility of concrete structures. It discusses how ductility is key to good seismic performance of structures. Ductility is defined and different levels of ductility are described, from the material level to the structural level. Factors that affect ductility include confinement of concrete, reinforcement, cross-section shape, and applied loads. Moment-curvature relationships are used to compute ductility at the cross-section level. Confinement improves concrete ductility by modifying its stress-strain behavior. Spiral reinforcement increases concrete strength under triaxial compression. Moment-curvature curves can indicate yield points and failure mechanisms for different types of sections.

This document provides an overview of shear and torsion behavior in reinforced concrete sections. It discusses several key topics: 1. There is no unified theory to describe shear and torsion behavior, which involves many interactions between forces. Current approaches include truss mechanisms, strut-and-tie models, and compression field theories. 2. Shear stresses are produced by shear forces, torsion, and combinations of these. The origin and distribution of shear stresses is explained. 3. Concrete alone cannot resist much shear or torsion due to its low tensile capacity. Reinforcement is needed to resist forces through truss action after cracking. 4. Design procedures from codes like ACI 318 are summarized

The document discusses the fundamentals of finite element analysis (FEA) for structural analysis. It provides an overview of FEA, including the modeling process of discretizing the structure into finite elements, generating the stiffness matrix, and solving the algebraic equations to determine structural responses like displacements and stresses. The document also reviews some prerequisite concepts from solid mechanics like stress-strain relationships, material properties, and solution of systems of equations. It traces the history and development of FEA and discusses its wide range of engineering applications today.

This document discusses the analysis and design of floor systems for tall buildings. It covers various types of gravity load resisting systems including direct and indirect load transfer systems. Key aspects covered include load transfer paths, behavior of slab-beam systems, importance of stiffness, simplified analysis methods for one-way and two-way slabs, and continuity conditions. Analysis approaches discussed are direct elastic analysis, moment coefficients, strip methods, yield line analysis, and finite element analysis. Design considerations include thickness estimation based on deflection and reinforcement sizing.

This document discusses structural systems for tall buildings and floor systems. It begins by providing historical context on how understanding of structural design has changed with scale, with Galileo being the first to recognize this. The four key principles of tall building design are then outlined. Different types of structural systems are classified based on material and construction method. Reinforced concrete building elements and vertical and lateral load resisting systems are described. Finally, various common floor system types like flat plates, waffle slabs, and beam and slab systems are presented.

This document discusses repairs, rehabilitation, and retrofitting of structures. It begins by defining repair, rehabilitation, and retrofitting. Repair returns a structure to its previous condition without improving strength. Rehabilitation considers strength by repairing damage. Retrofitting modifies existing structures to increase resistance to hazards like earthquakes. It provides examples of each process. The document outlines evaluation and quality control methods for repairs. It also discusses materials and techniques used for crack repair in structures, including epoxy injection grouting. Overall, the document provides an overview of restoring and upgrading structures through various repair, rehabilitation, and retrofitting methods.

Seminar Presentation on the basics of seismic retrofit to prevent structural damage to buildings, bridges, etc. from earthquake and wind loads.

1. The document discusses parameters that affect the strength of concrete in externally prestressed bridges. It examines factors like tendon layout, prestressing method, effective depth and eccentricity of external tendons, and materials used for tendons. 2. Studies have found that draped tendon profiles provide higher strength than straight profiles. External prestressing requires more prestressing force than internal prestressing, except for very deep girders. Increased effective depth and eccentricity of external tendons enhances strength. 3. Carbon fiber reinforced polymer tendons are an alternative to steel but have issues with brittleness and cost. Overall, optimizing tendon layout and placement can improve the strength of externally prestressed concrete bridges

This case study describes the innovative use of post-tensioned concrete in the construction of the David Brower Center in Berkeley, California. The building uses a hybrid system of post-tensioned concrete walls and frames to provide improved seismic performance and self-centering behavior after earthquakes. This allows the building to avoid permanent damage and remain functional. The post-tensioning reduces the amount of conventional reinforcement needed, making the building more compact and efficient to construct while also lowering its carbon footprint through the use of slag cement. Non-linear simulations were used to verify the design of this unique structural system.

Seismic retrofitting involves modifying existing structures to increase their resistance to seismic activity like earthquakes. It is important for historically significant buildings, areas prone to earthquakes, and tall or expensive structures. Retrofitting techniques can strengthen structures by increasing lateral strength, ductility, and strength-ductility. Some common retrofitting methods include adding new shear walls, steel bracing, base isolation, and column jacketing. Column jacketing involves wrapping columns with steel, reinforced concrete, or fiber-reinforced polymers to improve shear and flexural capacity. The selection of a retrofitting technique depends on factors like the structure type, material condition, cost, and effectiveness for the situation.

This document provides an introduction to prestressed concrete, including: 1) A prestressed concrete structure differs from reinforced concrete in applying an initial load to counteract stresses from use. 2) Prestressing concepts include transforming concrete to an elastic material, combining high strength steel with concrete, and load balancing. 3) Methods include pre-tensioning and post-tensioning, and materials include high strength steel tendons or bars, concrete, and grout.

1. The document discusses techniques for seismic retrofitting of existing structures, including adding new shear walls, steel bracing, jacketing columns and beams, using innovative materials like FRP composites, base isolation, seismic dampers, and tuned mass dampers. 2. It provides an overview of when seismic retrofitting is needed and objectives like ensuring public safety or maintaining structure functionality. 3. A case study describes retrofitting a historic structure in India damaged in an earthquake, including adding diagonal bracing, shotcreting walls, and cross pinning wall corners.

This document summarizes a study on retrofitting an existing reinforced concrete (R.C.) building using different non-destructive testing (NDT) methods. The study assessed the condition of the existing structure using NDTs like ultrasonic pulse velocity testing and Schmidt rebound hammer testing. The results from these tests showed the concrete quality was medium to doubtful. The study then proposes to strengthen and retrofit the structural elements like columns using reinforced concrete jacketing to allow for additional loads from a three-story building extension. The retrofitted structure is then designed to meet the required load carrying capacity.

This document summarizes a presentation on prestressed concrete. It begins with an introduction to prestressed concrete and how it overcomes weaknesses in concrete in tension. It then describes the principles of prestressing by inducing compressive stresses with high-strength tendons before loads are applied. The document compares reinforced concrete with prestressed concrete and describes the methods of pre-tensioning and post-tensioning. It provides examples of prestressed concrete structures like beams, bridges and discusses advantages like reduced size and increased spans as well as disadvantages like higher material costs.