Effect of Creep and Shrinkage model in calculation of long-term deflection of three-span solid slab continuous prestressed concrete bridge

Shrinkage and creep effect significantly to the long-term deflection of prestressed concrete bridge. The proper shrinkage and creep models should be developed to meet the requirements of deflection effect calculation. There are many models has been researched and developed. Each specification, such as ASSHTO, Eurocode, ACI and CEB-FIB, has their own model of shrinkage and creep by considering different input parameter. The long-term deflection calculation is also different in each specification as a result. In this paper, several shrinkage and creep models were selected and reviewed to see the difference and compare by using popular concrete grade in Vietnamese bridge building     (C40 and C45, equivalent to 40 and 45 Mpa, respectively). Those selected shrinkage and creep models are applied in calculation of deflection for a typical three-span continuous solid slab prestressed concrete bridge. The calculation result show the significant different of long-term deflection and the ASSHTO shrinkage and creep model show the biggest deflection

Effect of Creep and Shrinkage model in calculation of long-term deflection of three-span solid slab continuous prestressed concrete bridge

Shrinkage and creep effect significantly to the long-term deflection of prestressed concrete bridge. The proper shrinkage and creep models should be developed to meet the requirements of deflection effect calculation. There are many models has been researched and developed. Each specification, such as ASSHTO, Eurocode, ACI and CEB-FIB, has their own model of shrinkage and creep by considering different input parameter. The long-term deflection calculation is also different in each specification as a result. In this paper, several shrinkage and creep models were selected and reviewed to see the difference and compare by using popular concrete grade in Vietnamese bridge building     (C40 and C45, equivalent to 40 and 45 Mpa, respectively). Those selected shrinkage and creep models are applied in calculation of deflection for a typical three-span continuous solid slab prestressed concrete bridge. The calculation result show the significant different of long-term deflection and the ASSHTO shrinkage and creep model show the biggest deflection

ChatGPT as a Math Questioner? Evaluating ChatGPT on Generating Pre-university Math Questions

Mathematical questioning is crucial for assessing students problem-solving skills. Since manually creating such questions requires substantial effort, automatic methods have been explored. Existing state-of-the-art models rely on fine-tuning strategies and struggle to generate questions that heavily involve multiple steps of logical and arithmetic reasoning. Meanwhile, large language models(LLMs) such as ChatGPT have excelled in many NLP tasks involving logical and arithmetic reasoning. Nonetheless, their applications in generating educational questions are underutilized, especially in the field of mathematics. To bridge this gap, we take the first step to conduct an in-depth analysis of ChatGPT in generating pre-university math questions. Our analysis is categorized into two main settings: context-aware and context-unaware. In the context-aware setting, we evaluate ChatGPT on existing math question-answering benchmarks covering elementary, secondary, and ternary classes. In the context-unaware setting, we evaluate ChatGPT in generating math questions for each lesson from pre-university math curriculums that we crawl. Our crawling results in TopicMath, a comprehensive and novel collection of pre-university math curriculums collected from 121 math topics and 428 lessons from elementary, secondary, and tertiary classes. Through this analysis, we aim to provide insight into the potential of ChatGPT as a math questioner.Comment: Accepted at the 39th ACM/SIGAPP Symposium On Applied Computing (SAC 2024), Main Conferenc

History and applications of concrete steel composite structure

The composite steel-and-concrete structure is a modern structure, combines the advantages of concrete and steel one. Nowadays, it is widely utilized all over the world but not much in Vietnam. Studying the history of formation and development is very meaningful in understanding and applying this type of structure in practice. This article focuses on presenting the formation and development of the composite structure and, at the same time, introduces the potential and applications of the composite structure to the current construction practice in Vietnam

The politics of numbers and additionality governing the national Payment for Forest Environmental Services scheme in Vietnam: A case study from Son La province

Payments for forest environmental services (PFES) is a major breakthrough policy in the Vietnamese forestry sector because it contributes 25% of the total investments in the forestry sector and serves as the first market-based instrument employed to protect forests. However, there is little empirical evidence of its effectiveness. Is the policy meeting the core objectives of improving forest cover and forest quality and is it also achieving its claims of supporting local livelihoods? This paper analyses the environmental, social, and economic impacts of PFES in Son La province, the longest standing implementation of a PFES scheme in Vietnam. Our study uses a sampling method that incorporates pre-matching and a before-after-control-intervention approach. Data was collected from government statistics, remote sensing analysis, focus group discussions involving 236 people, surveys with a total of 240 households, and key informant interviews with 45 people. Our findings show that additionality of PFES in Son La is controversial and depends on who collects the data and what data is used to evaluate the impacts of PFES. Data collection is also politicized to serve central, provincial and district government interests. Evidence shows that PFES has provided little additional income to individual villagers to protect forests in Son La. However, total PFES revenue paid to communities generates significant income for village communities. Moreover, not all villagers can receive continuous payments from PFES, meaning that PFES has not become a stable source of income, rendering the permanence of PFES limited. Improving monitoring and evaluation policies coupled with transparent, inclusive, independent mechanisms are essential to providing a more accurate reflection of impacts from PFES in Vietnam

Generalised linear models for prediction of dissolved oxygen in a waste stabilisation pond

Due to simplicity and low costs, waste stabilisation ponds (WSPs) have become one of the most popular biological wastewater treatment systems that are applied in many places around the globe. Increasingly, pond modelling has become an interesting tool to improve and optimise their performance. Unlike process-driven models, generalised linear models (GLMs) can deliver considerable practical values in specific case studies with limited resources of time, data and mechanistic understanding, especially in the case of pond systems containing vast complexity of many unknown processes. This study aimed to investigate the key driving factors of dissolved oxygen variability in Ucubamba WSP (Ecuador), by applying and comparing numerous GLMs. Particularly, using different data partitioning and cross-validation strategies, we compared the predictive accuracy of 83 GLMs. The obtained results showed that chlorophyllahad a strong impact on the dissolved oxygen (DO) level near the water surface, while organic matter could be the most influential factor on the DO variability at the bottom of the pond. Among the 83 models, the optimal models were pond- and depth-specific. Specifically, among the ponds, the models of MPs predicted DO more precisely than those of facultative ponds; while within a pond, the models of the surface performed better than those of the bottom. Using mean absolute error (MAE) and symmetric mean absolute percentage error (SMAPE) to represent model predictive performance, it was found that MAEs varied in the range of 0.22-2.75 mg L(-1)in the training period and 0.74-3.54 mg L(-1)in the validation period; while SMAPEs were in the range of 2.35-38.70% in the training period and 10.88-71.62% in the validation period. By providing insights into the oxygen-related processes, the findings could be valuable for future pond operation and monitoring