Identification of local phenomena of plasticity in concrete under compression test

Abstract In this paper are specifically derived parameters useful to estimate the fatigue behaviour of concrete subject to uniaxial compression. For this, methodologies and experience already adopted in the study of fatigue steel and composite materials are used. These parameters are obtained by detecting the surface temperature of the specimen in the traditional static compression tests. In this way, the beginning of the crisis of the concrete for fatigue stress is linked to the loss of linearity of the temperature-test time curve (ΔT- t) and correlated to stress-test time curve (σ- t) of the tested cubic concrete specimens. In fact, the thermal analysis performed on the cubic specimen surface extended to the whole test time, shows interesting data on the crack beginning and on the subsequent evolution that after a certain number of loading cycles could determine the complete material failure. The slope variation in the interpolating curve temperature-test time allows to identify the critical points of the start fracture. This suggests a methodology to apply to civil infrastructures to evaluate in-situ, during the approval phase or during the working, critical situations. In this paper we propose a method to estimate the value of the "stress limit" (fatigue limit) of concrete material by means of an easy static uniaxial compression test according to an energetic method already proposed by Risitano

Determination of critical stress in high strength concrete

Abstract: In this work, more specimens were tested at equal conditions (static compression test) and, during the tests, the released heat for irreversible phenomena was monitored by means of the analysis of the temperature surface of the specimen. In this way, it was possible to estimate the average value of the macroscopic stress ("critical stress") for which local micro cracks begin. The compression static tests (load - machine time) and the related thermal analysis (temperature-machine time) of spots located on the specimen face of the specimens, highlighted the possibility to estimate the value of the compressive load to which there was loss of linearity in the temperature - machine time diagram ( Δt-t ). This effect is due to internal heat generated for irreversible phenomena (internal micro fractures). The results show that the "critical stress" has values practically coincident for the points (spots) located in different zones (center or corners of the specimens' surface)

Thermal Emission analysis to predict damage in specimens of High Strength Concrete

In this paper thermal analysis was applied to determine the “Critical Stress” of concrete, different from its ultimate strength, able to produce the first damage in the structures under compressive loads. The Critical Stress can be thought as the stress able to produce the beginning of fatigue rupture within the material. Several specimens of high strength concrete were tested in order to define the incipient crack phenomena, also in internal part of the specimen not accessible by direct inspections, with the aid of infrared thermography. A finite element analysis completes the study and compares, for the same static loading conditions, the stress state with the experimental thermographic images. The final results show as the coupling of normal compressive test and the acquisition of the thermal images can be a useful aid to estimate a security stress value, indeed the Critical Stress, before the Ultimate Serviceability Limit (SLU) of the structure, defined as the maximum load condition before its failure

How to Build Reputation in Financial Markets

A company's reputation for accountability and trustworthiness is a critical factor in its ability to attract the financial resources required to support its strategies. However, there has been little research done on how companies build and preserve the trust of financial markets. This research highlights a number of practices and features that seem to positively influence the formation of corporate reputation in financial markets. Collectively, the findings indicate that companies are guided by knowledgeable, respected and committed leaders, that are transparent and comprehensive in their communication of corporate plans, and that display credible and independent control systems are more likely to gather the consensus of the financial community around bold strategic plans

‘Short Interest Pressure’ and Competitive Behaviour

This study introduces and examines a new-to-strategy form of Wall Street pressure – ‘short interest pressure’ – the tension felt by management caused by short sales of the firm\u27s stock. Drawing from a sample of over 5000 competitive actions carried out by competing firms over a 6-year time period, we test whether the level of short interest pressure experienced by the firm in one time period is predictive of properties of the firm\u27s competitive action repertoire in the ensuing time period. Our findings suggest that when faced with short interest pressure firms tend to carry out a higher number of competitive actions in the following time period, as well as a set of actions that deviate from the industry norm. In addition, post hoc analysis reveals that this effect is amplified for poorly performing firms. Thus, our study contributes to a deeper understanding of the relationship between capital market signals and competitive strategy

Directions for a troubled discipline:strategy research, teaching and practice introduction to the dialog

This Dialog responds to a growing debate about the relevance of business schools generally and the value of strategy theory and research for strategic management practice. The authors propose that academic theory and management practice can be better connected through management education. The academy researches practice, derives theory, and returns it to practice through the development of teaching materials and the teaching of current and future practitioners. The three articles in this Dialog examine how different approaches to strategy research inform strategy teaching and its application to practice. Joseph Bower explains the rise of business policy and the process research approach that informed that teaching tradition at Harvard Business School. Robert Grant responds by emphasizing the economic theory underpinnings of strategic management research and its impact on teaching. Paula Jarzabkowski and Richard Whittington conclude by proposing a strategyas-practice perspective and suggesting ways to better incorporate strategy-as-practice research into strategy teaching

Economies of collaboration in build-to-model operations

This is the final version. Available from the publisher via the DOI in this record.The direct-from-model and tool-less manufacturing process of 3D printing (3DP) embodies a general-purpose technology, facilitating capacity sharing and outsourcing. Starting from a case study of a 3DP company (Shapeways) and a new market entrant (Panalpina), we develop dynamic practices for partial outsourcing in build-to-model manufacturing. We propose a new outsourcing scheme, bidirectional partial outsourcing (BPO), where 3D printers share capacity by alternating between the role of outsourcer and subcontractor based on need. Coupled with order book smoothing (OBS), where orders are released gradually to production, this provides 3D printers with two distinct ways to manage demand variability. By combining demand and cost field data with an analytical model, we find that BPO improves 3DP cost efficiency and delivery performance as the number of 3DP firms in the network increases. OBS is sufficient for an established 3D printer when alternatives to in-house manufacturing are few, or of limited capacity. Nevertheless, OBS comes at the cost of reduced responsiveness, whereas BPO shifts the cost and delivery performance frontier. Our analysis shows how BPO combined with OBS makes 3DP companies more resilient to downward movements in both demand and price levels.Innovate UKEngineering and Physical Sciences Research Council (EPSRC

Social stigma and executive compensation

We document that executives working at firms perceived negatively in light of social norms, such as tobacco, gambling and alcohol, earn a significant compensation premium. The premium compensates for personal costs executives bear due to their employer’s negative public perception and include: (i) a reduced likelihood these CEOs will serve as directors on other firms’ boards, which associates with lower executives’ social status, and (ii) impaired job mobility as employers shun stigmatized executives. The compensation premium is not explained by higher managerial skill required in firms we investigate, higher employment contract risk, political capital, litigation risk, or differences in corporate governance quality, and robust to endogeneity concerns. Our results highlight the significant impact job-related social stigma has on executive compensation