Causes of Failures in Circular Concrete Silo Walls, Particularly Under Environmental Influences

The paper reports the results of a case study for achieving longer service life and increasing the environmental sustainability of concrete silos. Damage mechanisms in concrete silo walls, and respectively in cylindrical structures (e.g., chimneys, cooling towers, and tanks), are widely diverse. The common causes of failures include those due to poor design considerations, construction deficiencies, non-compliance with operational rules and regulations, lack of maintenance, and insufficient and/or corroded reinforcements, together with the environmental conditions affecting the walls. In addition to the ultimate limit state design, temperature-induced cracking may often be underestimated in the design of reinforced concrete silos, leading to premature deterioration and losses in serviceability. Cracks from environmental or service conditions facilitate the ingress of moisture and corrosive agents. Therefore, there is an increased interest in reducing the appearance of cracks and limiting their width. The aim of this paper is to highlight the synergistic effects in the design, construction, and operation of silo walls, particularly under varying environmental influences. The research undertaken indicates that systematic errors can be identified and corrected.

A Structural Analysis Of A Factory Hall With A Two-Story Office Building As A Precast And Prestressed Concrete Construction

The objective of this thesis is to develop a precast and prestressed concrete design for a factory hall, which was initially planned as a steel structure. Furthermore, a structural analysis is conducted on several chosen structural elements according to the European Standards and the German Annexes respectively. The analysis is done both by manual calculation and software calculation for comparison and includes the ultimate limit state design, the serviceability limit state design and the design for the state of transportation and assembly of the precast members. Lastly, to illustrate the results of the analysis, an overview drawing with the new concrete design as well as formwork and reinforcement drawings for each of the analyzed structural members are developed.

Reliability-Based Ultimate Limit State Design of Micropiles in Ontario Soils

The design practice of micropiles in Ontario soils under the ultimate limit state was improved through both statistical and reliability analyses of a database of 40 micropile load tests. Micropile design is extremely dependent on engineering experience and judgement due to the lack of an accurate estimation of the bond strength. The FHWA manual of micropiles only provides wide ranges of bond strength in different ground conditions. Micropile load tests were conducted by Keller Foundations Ltd and collected for this study. From a statistical analysis, Fuller and Hoy’s method was selected as the best method to estimate the failure load from non-failed tests. Adjusted parameters were given to predict the bond strength of micropiles. A method was proposed to estimate the contributions from the cased length and the tip to the total resistance. In the end, a reliability analysis was conducted and the resistance factors were recalibrated.

Reliability-Based Ultimate Limit State Design of Micropiles in Ontario Soils

The design practice of micropiles in Ontario soils under the ultimate limit state was improved through both statistical and reliability analyses of a database of 40 micropile load tests. Micropile design is extremely dependent on engineering experience and judgement due to the lack of an accurate estimation of the bond strength. The FHWA manual of micropiles only provides wide ranges of bond strength in different ground conditions. Micropile load tests were conducted by Keller Foundations Ltd and collected for this study. From a statistical analysis, Fuller and Hoy’s method was selected as the best method to estimate the failure load from non-failed tests. Adjusted parameters were given to predict the bond strength of micropiles. A method was proposed to estimate the contributions from the cased length and the tip to the total resistance. In the end, a reliability analysis was conducted and the resistance factors were recalibrated.

A Structural Analysis Of A Factory Hall With A Two-Story Office Building As A Precast And Prestressed Concrete Construction

The objective of this thesis is to develop a precast and prestressed concrete design for a factory hall, which was initially planned as a steel structure. Furthermore, a structural analysis is conducted on several chosen structural elements according to the European Standards and the German Annexes respectively. The analysis is done both by manual calculation and software calculation for comparison and includes the ultimate limit state design, the serviceability limit state design and the design for the state of transportation and assembly of the precast members. Lastly, to illustrate the results of the analysis, an overview drawing with the new concrete design as well as formwork and reinforcement drawings for each of the analyzed structural members are developed.