Failure Mode Identification of Masonry Infilled RC Frames

This paper presents a new method to identify the ultimate failure mode of reinforced concrete (RC) frames due to the presence of masonry infill walls. The proposed method is based on simple geometry, reinforcement ratios and material properties of the elements involved in the frame-wall assembly. A simple engineering tool, expressed in terms of infill wall-to-RC frame stiffness and strength ratios, is developed to estimate whether the ultimate failure mode that would evolve during strong earthquake ground shaking in the infilled RC frame is brittle or ductile. The brittle failure mode, that is, shear failure in columns, should be avoided in design and mitigated in existing structures. The method checks various possible failure mechanisms including those that may develop depending on how the infill wall may fail during strong shaking such as the formation of captive columns. Data from twenty three laboratory specimens tested by other researchers are used in developing the engineering tool

Structural design under seismic risk using multiple performance objectives

Structural design is a decision-making process in which a wide spectrum of requirements, expectations, and concerns needs to be properly addressed. Engineering design criteria are considered together with societal and client preferences, and most of these design objectives are affected by the uncertainties surrounding a design. Therefore, realistic design frameworks must be able to handle multiple performance objectives and incorporate uncertainties from numerous sources into the process. In this study, a multi-criteria based design framework for structural design under seismic risk is explored. The emphasis is on reliability-based performance objectives and their interaction with economic objectives. The framework has analysis, evaluation, and revision stages. In the probabilistic response analysis, seismic loading uncertainties as well as modeling uncertainties are incorporated. For evaluation, two approaches are suggested: one based on preference aggregation and the other based on socio-economics. Both implementations of the general framework are illustrated with simple but informative design examples to explore the basic features of the framework. The first approach uses concepts similar to those found in multi-criteria decision theory, and directly combines reliability-based objectives with others. This approach is implemented in a single-stage design procedure. In the socio-economics based approach, a two-stage design procedure is recommended in which societal preferences are treated through reliability-based engineering performance measures, but emphasis is also given to economic objectives because these are especially important to the structural designer's client. A rational net asset value formulation including losses from uncertain future earthquakes is used to assess the economic performance of a design. A recently developed assembly-based vulnerability analysis is incorporated into the loss estimation. The presented performance-based design framework allows investigation of various design issues and their impact on a structural design. It is a flexible one that readily allows incorporation of new methods and concepts in seismic hazard specification, structural analysis, and loss estimation

A performance-based optimal structural design methodology

A general framework for multi-criteria optimal design is presented which is well-suited for performance-based design of structural systems operating in an uncertain dynamic environment. A decision theoretic approach is used which is based on aggregation of preference functions for the multiple, possibly conflicting, design criteria. This allows the designer to trade off these criteria in a controlled manner during the optimization. Reliability-based design criteria are used to maintain user-specified levels of structural safety by properly taking into account the uncertainties in the modeling and seismic loads that a structure may experience during its lifetime. Code-based requirements are also easily incorporated into this optimal design process. The methodology is demonstrated with two simple examples involving the design of a three-story steel-frame building for which the ground motion uncertainty is characterized by a probabilistic response spectrum which is developed from available attenuation formulas and seismic hazard models

Observations About the Seismic Response of RC Buildings in Mexico City

Over 2000 buildings were surveyed by members of the Colegio de Ingenieros (CICM) and Sociedad Mexicana de Ingenieria Estructural (SMIE) in Mexico City following the Puebla-Morelos Earthquake of 2017. This inventory of surveyed buildings included nearly 40 collapses and over 600 buildings deemed to have structural damage. Correlation of damage with peak ground acceleration (PGA), peak ground velocity (PGV), predominant spectral period, building location, and building properties including height, estimated stiffness, and presence of walls or retrofits was investigated for the surveyed buildings. The evidence available suggests that (1) ground motion intensity (PGV) drove the occurrence of damage and (2) buildings with more infill and stiff retrofit systems did better than other buildings

Experimental validation of a damage detection approach on a full-scale highway sign support truss

Highway sign support structures enhance traffic safety by allowing messages to be delivered to motorists related to directions and warning of hazards ahead, and facilitating the monitoring of traffic speed and flow. These structures are exposed to adverse environmental conditions while in service. Strong wind and vibration accelerate their deterioration. Typical damage to this type of structure includes local fatigue fractures and partial loosening of bolted connections. The occurrence of these types of damage can lead to a failure in large portions of the structure, jeopardizing the safety of passing traffic. Therefore, it is important to have effective damage detection approaches to ensure the integrity of these structures. In this study, an extension of the Angle-between-String-and-Horizon (ASH) flexibility-based approach [32] is applied to locate damage in sign support truss structures at bay level. Ambient excitations (e.g. wind) can be considered as a significant source of vibration in these structures. Considering that ambient excitation is immeasurable, a pseudo ASH flexibility matrix constructed from output-only derived operational deflection shapes is proposed. A damage detection method based on the use of pseudo flexibility matrices is proposed to address several of the challenges posed in real-world applications. Tests are conducted on a 17.5-m long full-scale sign support truss structure to validate the effectiveness of the proposed method. Damage cases associated with loosened bolts and weld failures are considered. These cases are realistic for this type of structure. The results successfully demonstrate the efficacy of the proposed method to locate the two common forms of damage on sign support truss structures instrumented with a few accelerometers

A Methodology for Performance-Based Optimal Structural Design

A general framework is presented for optimal design based on multiple design criteria which is suitable for performance-based design of structural systems operating under uncertain risk. Reliability-based design criteria are used to maintain specified levels of structural safety by properly taking into account the uncertainties in the future seismic loads. The ground motion uncertainty is characterized by a probabilistic response spectrum developed from available attenuation formulas and seismic hazard models. A simple illustrative example is given

Multi-criteria optimal structural design under uncertainty

A general framework for multi-criteria optimal design is presented which is well suited for performancebased design of structural systems operating in an uncertain dynamic environment. A decision theoretic approach is used which is based on aggregation of preference functions for the multiple, possibly con#icting, design criteria. This allows the designer to trade o! these criteria in a controlled manner during the optimization. Reliability-based design criteria are used to maintain user-speci"ed levels of structural safety by properly taking into account the uncertainties in the modelling and seismic loads that a structure may experience during its lifetime. Code-based requirements are also easily incorporated into this optimal design process. The methodology is demonstrated with a simple example involving the design of a three-storey steel-frame building for which the ground motion uncertainty is characterized by a probabilistic response spectrum which is developed from available attenuation formulas and seismic hazard models. Copyrigh