Bond Strength and Development Length Models for Straight Plain Longitudinal Reinforcement in Tension

Previous experimental and analytical studies have shown that state-of-practice provisions for evaluating the bond strength and development length of plain bars are not appropriate. Existing provisions tend to provide overconservative estimates of the required development length of plain bars. Using a database of 518 development and 35 splice test specimens, this study proposes simple models for evaluating the bond strength and development length of plain round and square bars. The study demonstrates that the bond strength of a plain bar depends on the casting position, concrete strength, and the ratio of concrete cover to bar diameter. The study also shows that the influence of the loading rate and stirrup confinement level on the bond strength of plain bars may be insignificant. Furthermore, it is shown that the bar size factor in ACI 318 for deformed bars is not justified for plain bars. Using the proposed model, it is concluded that the required development length of a bottom-cast plain bar is 1.33 times that of a bottom-cast deformed bar. Also, the required development length of a top-cast plain bar is two times that of a top-cast deformed bar. The proposed model in this paper is recommended for incorporation into assessment standards

Multicriteria decision making for selecting an optimal survey approach for large building portfolios

Technological advances and innovations have led to various pre- and post-disaster data collection alternatives to traditional sidewalk surveys. Hence, selecting a suitable survey approach may be challenging for different decision-makers. This paper proposes a multicriteria decision-making (MCDM) method to choose the optimal survey approach to gather exposure information needed for reliable multi-hazard risk assessment of large building and infrastructure portfolios. Both deterministic and stochastic implementations of MCDM are investigated, considering primary sources of aleatory and epistemic uncertainties. The applicability of the proposed framework is demonstrated for a portfolio of 13,200 buildings in a hypothetical multi-hazard prone region. The results show that informed decisions on identifying an optimal survey technique could be efficiently derived using MCDM and a number of relevant criteria. The proposed methodology can support various decision-makers in pre- and post-disaster risk modeling and management/reduction

Seismic fragility assessment of bridges with as-built and retrofitted splice-deficient columns

A significant proportion of existing bridges in high seismic regions were constructed prior to the 1970s. As a result of poor reinforcement detailing, pre-1970s bridge columns are susceptible to lap-splice or shear failure in the plastic region. Given the high economic impact of retrofitting all pre-1970s reinforced concrete (RC) bridges, it is essential to identify the most vulnerable bridges for retrofit prioritisation. Analytical fragility functions are useful for quantifying the seismic vulnerability of existing bridge stock. However, the accuracy of these fragility functions relies on the adequacy of the adopted modelling approach. This paper presents a hinge-type modelling approach for capturing the seismic response of as-built splice-deficient and retrofitted RC bridge columns. Fragility analysis is carried out for typical seat and diaphragm abutment two-span bridges using the proposed hinge-type modelling approach. The results showed that the vulnerability of the bridges depends on the column failure mode and the limit state under consideration. Also, the common notion that the column is the most vulnerable component may not necessarily be true. The study underscored that retrofitting columns without retrofitting other components may not effectively mitigate the damage and associated risk

Seismic Performance of Reinforced Concrete Beams Susceptible to Single-Crack Plastic Hinge Behavior

Following the 2010/2011 Canterbury and 2016 Kaikoura earthquakes, a number of reinforced concrete (RC) beams in high-rise structures developed a single primary crack at the beam-column interface without the formation of distributed secondary cracks along the beam length. Detailed assessments showed that these beams have conforming longitudinal steel ratios and the single-crack mechanism may be due to design and/or construction practices for beam-column joints in the 1980s. In order to investigate the seismic behavior of reinforced concrete beams with detailing that inhibited the spread of flexural yielding, an experimental program was carried out on RC beam specimens, having similar reinforcement detailing to that of beams that developed a single crack at their ends during the Kaikoura earthquake to understand their seismic behavior, postearthquake repairability, and residual low-cycle fatigue life. Experimental results showed that the beams were able to undergo significant inelastic drift demands without loss of lateral resistance and have sufficient residual drift capacity following moderate and large earthquake demands. The response of the beam specimens was dominated by hinge rotation via the bond-slip mechanism. Comparisons showed that the measured drift capacities of the beams exceeded the predicted drift capacities computed using state-of-the-practice procedures

Flexure-axial-shear interaction of ductile beams with single-crack plastic hinge behaviour

One of the key damage observations in modern reinforced concrete (RC) frame buildings, damaged following the 2010/2011 Canterbury and 2016 Kaikoura earthquakes, was localised cracking at the beam-column interface of capacity-designed beams. The localised cracking in the beams was due to curtailed longitudinal bars at the beam-column interface. Following these observations, without experimental data to justify desirable seismic performance, modern beams controlled by localised cracking were assumed to be potentially earthquake-vulnerable. To address this, an experimental program was carried out on six RC beam specimens susceptible to single-crack plastic hinge behaviour due to curtailed longitudinal bars. The experimental data show that RC beams with single-crack plastic hinge behaviour can undergo significant inelastic drift demands without loss of lateral resistance. However, contrary to conventional beams with distributed cracking, the response of RC beams with single-crack plastic hinge behaviour due to curtailed longitudinal bars is mainly dominated by hinge rotation (via bond-slip) and shear sliding at the column face. The current paper studies the interdependence of axial elongation, bond-slip and shear sliding deformation of RC beams with single-crack plastic hinge behaviour under cyclic demands. A procedure for seismic assessment of RC beams with single-crack plastic hinge behaviour due to curtailed longitudinal bars is proposed. The proposed formulations can be adopted to develop adequate numerical models for simulating the response of RC frames with beams susceptible to single-crack plastic hinge behaviour due to curtailed longitudinal bars

Limit states for post-earthquake assessment and recovery analysis of ductile concrete components

Post-earthquake assessment procedures require component deformation limits to identify locations for visual inspection and locations needing structural repair. This study proposes a framework for defining component deformation limits for detailed visual inspection and repair for earthquake-damaged concrete buildings. First, observations from cyclic tests of ductile concrete components (beams, columns, and walls) suggested that the residual capacity (in terms of strength and deformation capacity) of such components is likely uncompromised if the deformation at the initiation of lateral strength loss (LSL) is not exceeded in prior loading histories. The results also revealed that the deformation at the initiation of LSL typically corresponds to the onset of longitudinal bar buckling in ductile components. Furthermore, using experimental data, multipliers are developed as fractions of ASCE/SEI 41 modeling parameters at lateral failure (i.e. a or d) to predict deformation at initiation of LSL. Subsequently, a probabilistic approach is proposed for defining the component deformation limits, considering uncertainty in both capacity and demand. Component deformation limits for detailed visual inspection are defined such that there is a low probability (adopted as <10%) of exceeding the deformation at the initiation of LSL. The component deformation limit for repair is defined as the median deformation at the initiation of LSL (i.e. 50% probability of exceedance)

A mixed-mode data collection approach for building inventory development: Application to school buildings in Central Sulawesi, Indonesia

Urban disaster risk management and reduction requires the development and periodic updating of regional building inventories. However, the development of such inventories can be very cost-intensive and time-consuming, making this a challenging task, particularly for low- and middle-income countries. This article discusses a mixed-mode building inventory data collection framework using a rapid and cost-effective remote survey technique that can be deployed in various geographic contexts. A key component of the proposed approach is an inter-rater reliability analysis of data collected from traditional sidewalk surveys and remote surveys for a small subset of buildings in the considered building portfolio, which is used to assess the suitability of the remote survey for the location(s) considered. The framework is demonstrated by developing a regional database of school buildings in the Central Sulawesi region of Indonesia. The database consists of 2536 school buildings from 454 elementary and high schools in the Palu, Sigi, and Donggala regions, susceptible to earthquake-induced ground shaking, tsunami, liquefaction, and landslides. The developed database can be used in pre-event/long-term risk analysis and management, post-event/near-real-time loss estimation, and regional-level decision-making on school assets and related policies. The database has been made available for public use and can be readily harmonized with similar databases for other regions

A Probabilistic Framework for Post-Disaster Recovery Modeling of Buildings and Electric Power Networks in Developing Countries

Post-disaster recovery is a significant challenge, especially in developing countries. Various technical, environmental, socioeconomic, political, and cultural factors substantially influence post-disaster recovery. As a result, methodologies relevant in developed nations may not be directly applicable in Global South contexts. This study introduces a probabilistic framework for modeling the post-disaster recovery of buildings and electric power networks (EPN) in developing countries. The proposed framework combines a building-level assessment of individual assets with a community-level assessment of EPNs to evaluate a building portfolio's post-event functionality state. As part of the framework, a stochastic network analysis approach is proposed to estimate the recovery time of damaged buildings while accounting for technical, environmental, socioeconomic, political, and cultural factors, quantified using data gathered from past events. Similarly, a probabilistic modeling approach is proposed to quantify the EPN's initial post-event outage levels. Specifically, empirical formulations for estimating the recovery time of an EPN as a function of its initial post- event outage levels are calibrated using post-event data from developing countries. A case study is presented to illustrate the application of the proposed framework to model the post-earthquake recovery of a synthetic low-income residential community. The analysis showed that negative technical, environmental, socioeconomic, political, and cultural factors could amplify the reconstruction time of damaged buildings by a factor of almost three. The proposed framework can support decision-makers in disaster planning and management strategies for vulnerable low-income communities

Investing in disaster preparedness and effective recovery of school physical infrastructure

The importance of functioning education infrastructure for the post-disaster recovery of communities is well-acknowledged. Yet, recent natural-hazard events worldwide have highlighted that school facilities still face many post-disaster recovery-impeding challenges. A significant investment in resilience enhancement through appropriate disaster preparedness and post-disaster recovery management is needed to tackle such global challenges. This paper summarises a series of stakeholder engagements (through interviews and focus group discussions) aimed at providing evidence-based recommendations to foster a more rapid and effective post-disaster recovery of school physical infrastructure in disaster-prone marginalised communities. The case-study community is in Central Sulawesi, Indonesia – a region still recovering from the 2018 Central Sulawesi earthquake, tsunami, and liquefaction, which caused damage to over 1200 schools. The considered stakeholders have significant experience in post-disaster recovery management in Central Sulawesi. This paper identifies early-response funding mechanisms, genuine collaborations between stakeholders, and improved capacity for self-organisation as critical elements for an inclusive, sustainable, safer, and more resilient school physical infrastructure. Although the discussion in this paper focuses on Central Sulawesi, the project's outcomes are scalable to other regions in Indonesia, South-East Asia, and other disaster-prone developing nations