Mix Design Effects on the Durability of Alkali-Activated Slag Concrete in a Hydrochloric Acid Environment

Because of its high strength, energy reduction, and low environmental impact, researchers have encouraged considering alkali-activated slag concrete (AASC) as a potential alternative to conventional concrete. In this study, the impact of mix design parameters on the durability of AASC, made with ground granulated blast furnace slag and activated with different alkaline solutions (NaOH, KOH, and Na2SiO3 ) immersed up to six months in a hydrochloric acid bath with pH = 3, has been investigated. A total of 13 mix designs were made in a way that, in addition to the type of alkaline solution, considered three other parameters, namely the molarity of alkaline solutions, the weight ratio of alkaline solutions to slag, and the weight ratio of alkaline solutions to sodium silicate. Visual inspections displayed that the AASC samples almost remained intact after exposure to an HCl acid solution with pH = 3 for up to 6 months, while the OPC sample experienced deleterious deterioration. The results clearly show that AASC outperformed OPC concrete when it comes to durability in an HCl acid solution. The strength reduction and weight loss of AASC compared with OPC concrete were approximately one-tenth and one-fifth, respectively. The AASC samples containing potassium hydroxide showed a higher strength reduction and weight loss in the HCl acid solution than the samples made with sodium hydroxide

The Role of Therapeutic Landscape in Improving Mental Health of People with PTSD

Post-traumatic stress disorder (PTSD) as a complex disorder, with serious consequences, affects the quality of life of the individual, the family, as well as the community. Therefore, the subject of this chapter is to study how to reduce stress and improve the quality of life of these people and consequently the community. This chapter is based on documentary studies including the foundations of the theory, the study of the results of experiments in the world, and case studies in this field, which shows that the interaction of individuals with PTSD and therapeutic landscapes can act as a therapeutic mechanism. In the following, features from therapeutic landscapes that help to optimize mental health levels are reviewed in people with PTSD, briefly

Pros and cons of various equivalent frame models for nonlinear analysis of URM buildings

Brick masonry is considered as one of the old construction materials, and several cultural heritage assets are made of unreinforced masonry (URM), which is susceptible to earthquakes due to its brittle behavior. The equivalent frame method (EFM) is a nonlinear modeling method widely utilized for the seismic analysis of URM buildings with lower computational efforts than finite and discrete element methods. In this study, three macroelements, including the unified method (UM), composite spring method (CSM), and double modified multiple vertical line element model (DM-MVLEM), were utilized to model three case studies. The first case study is a full-scale two-story URM wall that was tested by applying the cyclic prescribed displacements, and two other case studies were developed by changing the configuration of openings. The second case study is with short piers, and weak spandrels exist in the third model. The efficiency of the methods in terms of the accuracy of the pushover results, prediction of damage patterns, and duration of the incremental dynamic analysis (IDA) are discussed. Finally, seismic fragility curves are provided to compare the IDA results

Vulnerability assessment of cultural heritage structures

Cultural heritage (CH) assets are the legacy of a society that are inherited from the past generations and can give us lessons for contemporary construction. Not only the formally recognized CH assets but also the non-CH structures and infrastructure, and the interconnection between them are crucial to be considered in a vulnerability assessment tool for the sustainable reconstruction of historic areas. Since most CH assets were not designed based on robust design codes to resist natural hazards such as earthquakes, vulnerability assessment and preservation are pivotal tasks for the authorities. For this aim, Hyperion, an H2020 project (Grant agreement No 821054), was formed in order to take advantage of existing tools and services together with novel technologies to deliver an integrated vulnerability assessment platform for improving the resiliency of historic areas. Geometric documentation is the first and most important step toward the generation of digital twins of CH assets that can be facilitated using 3D laser scanners or drone imaging. Afterward, the finite element method is an accurate approach for developing the simulation-based digital twins of cultural heritage assets. For calibration of the models, the result of the operational modal analysis from the ambient vibration testing using accelerometers can be utilized. Structural analysis for the prediction of the structural behavior or near real-time analysis can be carried out on the calibrated models. However, the full finite element analysis needs a lot of computational effort, and to tackle this limitation, equivalent frame methods can be utilized

Structural Vulnerability Assessment of Heritage Timber Buildings: A Methodological Proposal

The conservation of heritage structures is pivotal not only due to their cultural or historical importance for nations, but also for understanding their construction techniques as a lesson that can be applied to contemporary structures. Timber is considered to be the oldest organic construction material and is more vulnerable to environmental threats than nonorganic materials such as masonry bricks. In order to assess the structural vulnerability of heritage timber structures subjected to different types of risk, knowledge about their structural systems and configurations, the nature and properties of the materials, and the behavior of the structure when subjected to different risks, is essential for analysts. In order to facilitate the procedure, different assessment methods have been divided into the categories in situ and ex situ, which are applicable for vulnerability assessments at the element and full-scale level of a case study. An existing methodology for structural vulnerability assessments and conservation of heritage timber buildings is reviewed and a new methodology is proposed

Seismic Vulnerability Assessment and Strengthening of Heritage Timber Buildings: A Review

Recent studies highlight the potential impact of earthquakes on cultural heritage sites and monuments, which in turn yield significant adverse impacts on economies, politics, and societies. Several aspects such as building materials, structural responses, and restoration strategies must be considered in the conservation of heritage structures. Timber is an old organic construction material. Most of the historic timber structures were not designed to withstand seismic forces; therefore, the seismic vulnerability assessment of heritage timber structures in areas with high seismic hazard is essential for their conservation. For this purpose, different strategies for the numerical modeling of heritage timber buildings have been developed and validated against tests results. After performing seismic analysis using detailed analytical methods and predicting the susceptible structural components, strengthening techniques should be utilized to mitigate the risk level. To this aim, various methods using wooden components, composite material, steel components, SMA etc., have been utilized and tested and are reviewed in this study. There are still some gaps, such as full-scale numerical modeling of strengthened buildings and investigating the soil–structure interaction effects on the seismic behavior of buildings that should be investigated

A novel macroelement for seismic analysis of unreinforced masonry buildings based on MVLEM in OpenSees

Unreinforced masonry (URM) buildings are susceptible to extraordinary actions such as earthquakes compared to steel or reinforced concrete buildings. Various methods have been developed for the computational analysis of URM buildings in the last few decades. The equivalent frame method (EFM) is one of the numerical modeling approaches widely used for the nonlinear analyses of URM buildings. Different macroelements in the context of the EFM have been proposed. However, there is still a need for an efficient modeling approach in the computational effort that can predict the real behavior of URM structural components with sufficient agreement and available in opensource structural analyses software packages. For this purpose, a new macro-element based on the multiple vertical line element method (MVLEM) element has been developed in this study. The MVLEM is available in the OpenSees software platform comprising vertical uniaxial macro-fibers and a shear spring as an efficient macroelement for nonlinear analysis of flexure-dominated reinforced concrete walls. The novel macroelement, double modified MVLEM (DM-MVELM) element has been proposed consisting of two modified MVLEM elements tied with a nonlinear shear spring at the middle with a trilinear backbone behavior. DM-MVLEM can capture the axial-flexural interaction with lower computational effort than finite element models and fiber beam-column elements. The DM-MVLEM has been validated against the test results at the structural components level and a full-scale perforated URM wall. Unified method (UM) and composite spring method (CSM) are two existing EFMs that are presented in this study. A study is performed by comparing the seismic behavior of the perforated URM walls modeled using the UM, CSM, and DM-MVLEM modeling strategies. Results show that the DM-MVLEM can predict the damage patterns, and nonlinear behavior of spandrels can be simulated that was usually modeled with linear behavior in EFMs

State of the art of simplified analytical methods for seismic vulnerability assessment of unreinforced masonry buildings

Cities in the developing world are facing outstanding economic and human losses caused by natural hazards such as earthquakes, and the amount of losses is affected by the quality of preventive measures and emergency management. For this reason, seismic vulnerability assessment is considered a crucial part of a strategy for seismic risk mitigation and for improving the resiliency of cities. Due to the high number of building archetypes for the seismic vulnerability assessment at a large scale, fast, simplified methods have been proposed that can facilitate the assessment procedure with low computational effort. Simplified methods can be categorized into three groups: analytical, empirical, and hybrid methods. In this study, simplified analytical methods for the seismic vulnerability assessment of unreinforced masonry (URM) buildings were reviewed, starting with their classification into three main groups: collapse mechanism-based, capacity spectrum-based, and fully displacement-based methods. Finally, attention was given to the corresponding software packages that were developed to facilitate the assessment procedure

Model Updating of a Masonry Tower based on Operational Modal Analysis: The Role of Soil-structure Interaction

Vibration-based finite element model (FEM) updating of cultural heritage assets is gaining so much attraction these days since destructive tests are usually not allowed to be performed. In this study, a framework for developing three-dimensional (3D) FEMs is proposed using 3D laser scanners and applied on Slottsfjell tower, a stone masonry tower in Tønsberg, Norway. Operational modal analysis (OMA) was done based on the ambient vibration testing (AVT) data to define the frequency values and corresponding mode shapes of the tower. Mechanical properties of the tønsbergite stone were utilized to derive the base values of the material properties of the homogenized masonry for performing sensitivity analysis and FEM updating. To investigate the effect of the soil-structure interaction (SSI) on the FEM updating results, three FEMs are developed. The fixed-base model is the FEM without considering the SSI effects, and two other FEMs are developed using the substructure and direct methods for simulating the SSI effects. Sensitivity analysis was performed to investigate the effective parameters on the dynamic characteristics of the models. FEM updating was conducted on the three FEMs, and results are compared to each other to show the role of the SSI on the FEM updating results. The resonance effect can cause damages to buildings located even in low seismicity zones. For this aim, the risk of resonance effect has been evaluated for the tower. Finally, linear dynamic analysis was performed on the three calibrated models, and the results were compared to each other

Seismic Performance Evaluation of Special RC Frames with Gravity Steel Columns under the Base Level

In many multistory buildings, basement levels are used as parking spaces. However, dimensions of reinforced concrete columns at these levels cause them to be unideal parking spaces. An alternative is to replace the RC columns in middle frames with steel columns that are not a part of seismic force resisting system and only support vertical loads, therefore have smaller sections. Using simply supported steel columns under the base level is beneficial not only because they have smaller cross-sections which lead to increasing the parking space but also these steel columns are easier to be replaced after any possible damages and can be considered as convenient alternatives compared to ordinary RC columns in construction. In this research, seismic performance of structures implementing the suggested alternative is evaluated using nonlinear static and dynamic analyses and compared to that of regular counterparts. Results show that these structures pass the acceptability tests proposed by FEMA P695 methodology. Moreover, seismic performance factors of these two structural systems have been calculated and proposed