Conceptual framework for improved management of risks and uncertainties associated with the performance of the building enclosure

The building enclosure has a substantial impact on the overall performance of a building, especially in relation to moisture safety, energy use, environmental footprint and economy. Although the introduction of novel building technology can increase the risk of failures in terms of reduced building performance, failures can also result from the recurrence of past mistakes while using well established building technologies. This indicates that the dissemination of existing knowledge, often documented in project reports, handbooks or experience databases, is not always carried out in an efficient way. One way of addressing the issue is by increasing awareness concerning potential risks and uncertainties in the building process. The current paper presents a conceptual framework which has the broader aim of promoting risk awareness, improving the treatment of uncertainties and ultimately facilitating risk informed decision making during the modern design and construction process. The framework incorporates risk treatment with BIM based design and construction and could be supported by existing failure/damage and/or experience databases or knowledge systems

Energy efficient buildings by use of reinforced masonry walls : An experimental study

Användning av ytförstärkning har undersökts som ett led i att förbättra murade ytterväggars energiprestanda. De experimentella undersökningarna genomförda vid Lunds tekniska högskola visar att genom användning av ytförstärkning kan tjockleken på den bärande delen i en yttervägg minskas med mellan 30 - 50 procent jämfört med dagens väggtyper. Väggarnas bärförmågan kan samtidigt bibehållas eller rentav ökas. Det insparade utrymmet kan nyttjas till mer termisk isolering, vilket medför att ytterväggens energiprestande förbättras utan ytterligare ökning av dess totala tjocklek

Quantitative assessment of the impact of climate change on creep of concrete structures

Creep of concrete structures is in most cases regarded as a serviceability problem that may have impacts on maintenance and repair costs but cannot lead to structural collapse. However, several structural collapses during the past decades have been, at least partly, attributed to excessive creep deformations. Recent studies suggest that concrete creep may be further exacerbated by climate change. The current study demonstrates how this effect can be quantitatively assessed. For this purpose, six different creep models (i.e, Model Code 1999, Model Code 2010, MPF, B3, B4, and B4s models) are used under considerations of historical and future climatic conditions in southernmost Sweden as given by a regional climate model. Furthermore, two different simulations were performed as follows: 1) considering only climate uncertainty represented by the climate model, and 2) considering climate uncertainty, parameter uncertainty, and creep model uncertainty. The highest impact of climate change on end of century creep coefficient is observed using model B4 where the 75th percentile of the increase in creep coefficient is found to range from 8% to ∼14% depending on the climate scenario. The results of the assessment in this article show that the uncertainty related to climate change on creep of concrete structures (higher effect in RCP8.5 than in RCP2.6 and RCP4.5 which have very similar results) is much smaller than uncertainties resulting from creep modelling

Holistic approach for treatment of accidental hazards during conceptual design of bridge - A case study in Sweden

The control of risks in engineering design is, for most conventional construction projects, achieved through the use of design codes. However, relying on design based on code-compliance can lead to situations where risks are overlooked or inadequately treated; a complementary approach is needed. In this paper, a holistic risk-informed approach for the treatment of accidental hazards during the conceptual design of bridges is considered and a framework for such an approach is provided. The treatment of these design situations is incompatible with current codified approaches. Although risk assessments are commonly used in the design of large scale infrastructure projects, such approaches are rarely used for more common bridge designs. The assessment procedure, applicable for more conventional bridge projects, is described and some background information is provided that is useful for applying the proposed approach in practice. To illustrate the application of the proposed approach in practice, a case study of a bridge construction project in the west of Sweden is considered in which the approach is applied

Reliability of RC Bridge Supports Designed to Resist Heavy Goods Vehicle Collisions

The reliability of bridge-supporting structures to resist impacts from heavy goods-vehicles (HGV) is investigated. Probabilistic simulations are carried out to calculate the reliability index of a circular reinforced concrete column that has been designed using historical values for equivalent static impact loads provided in the Eurocode. Considerations are made for the uncertainties related to the dynamic response and resistance of reinforced concrete bridge supports subjected to vehicular impact. A general procedure is outlined for determining the dynamic resistance of the structure. As input for the impact force, results from previous probabilistic simulations of HGV impacts to road side structures were used. It is found that the design based on the codified approach does not provide adequate safety levels in the case of the structure studied. An alternative formulation for determining more appropriate values for the impact load is suggested and some discussion was given pertaining to other possible design strategies for the treatment of these types of loading situations

Opportunities and challenges of digitalization and automation in bridge design : A pre-study

This report presents the findings from a pre-study concerning the opportunities and challenges of digitalization and automation in bridge design. The project approach is divided into three parts: 1) a short review of the relevant literature, 2) investigations concerning bridge industry perspectives (with focus on bridge consultants), and 3) the identification of future research needs based on parts 1 and 2. The literature review found that digital transformation is often a desirable goal within different industries in Europe and Sweden with the justification that it could improve productivity. Specific digital technologies which have been identified as providing the most potential specifically in the building sector include the automation of knowledge-based work, the utilization of cloud-based services, internet of things (IoT) as well as mobile internet. When it comes to structural engineering, there is a clear indication that the profession is undergoing a paradigm shift towards a greater reliance on digital tools. Professional societies in both the US (ASCE) and the UK (IStructE) highlight the need for the profession to evolve and both have published insights concerning opportunities, challenges, and future needs. Some specific challenges include the need for broadening expertise as well as reforming and improving education for both students and practicing engineers (continuing profession development). The latter was also highlighted in a recent study in Sweden by af Klintberg (2018).Bridge industry perspectives were investigated through a small focus-group and questionnaire study, which involved bridge engineering consultants and experts. The results from both highlighted a high interest in and trends toward increased digital transformation and automation in bridge engineering practice today. Some opportunities which were mentioned include the possibility to reduce conservatism and optimize structures considering a variety of criteria, automation of routine work allowing for more time towards other relevant tasks, as well as the adoption of digital platforms and tools for improved communication, coordination, and management. One interesting ongoing trend within companies is the development of in-house digital tools, often viewed as giving a competitive edge. Challenges of digital transformation and automation which were identified often focussed on risks associated with over-reliance and faith in digital tools coupled with the need for adopting suitable design checking procedures considering potentially complex and comprehensive input/output in calculation (FE) software. Another interesting aspect which was discussed concerned the trend of increased specialization within the sector leading to the question of whether there is a need for ‘general practitioners’ of structural engineering.In synthesizing the results from the first two parts of the project, broad future research needs were identified. These include the necessity to investigate further, and in more detail, both positive and negative impacts of ongoing and future digital transformation and automation. To facilitate a more informed way forward, such impacts should be assessed and evaluated in relation to the structural engineering profession, the bridge and construction sector (including all relevant stakeholders), the individual engineer(s), as well as society at large. Some specific relevant future research topics relate to the investigation of professional variability and its implications, the human-machine interface, the transfer of IT models from design and planning to facility management, as well as effective knowledge and experience transfer in modern design practice. The final sections of the report also elaborate briefly on two common digital technologies used today: digital tools for structural design calculations and Building Information Modelling (BIM)

From Code Compliance to Holistic Approaches in Structural Design of Bridges

Forum papers are thought-provoking opinion pieces or essays founded in fact, sometimes containing speculation, on a civil engineering topic of general interest and relevance to the readership of the journal. The views expressed in this Forum article do not necessarily reflect the views of ASCE or the Editorial Board of the journal

Holistic approach in engineering design - controlling risks from accidental hazards in bridge design

Engineering design, in concise terms, is what engineers do using what they know. It is the underlying decision making activity that determines what is to be built and how it should be built. An ever present requirement in engineering design is that the structure should be safe. While historical approaches to safety in design relied on experience and engineering judgment, modern approaches have rationalized uncertainty in an effort to treat risks in a more consistent and objective way. Concurrent to these advancements, design codes have been developed which include safety formats that are calibrated using these rationalized approaches. This thesis investigates the limitations of the design codes in controlling risks in engineering design and proposes that a complementary approach – involving case-specific risk assessments – is necessary for addressing the risks that are not properly treated by the design codes. The main advantage of such an approach is that: • it broadens the scope of assessment to consider structural systems and possibly non-structural constituents; • it is also applicable during the conceptual design phase for the bridge structure; and • it is complementary to current codified approaches While similar approaches are common in large scale construction projects they are rarely applied in the design of more conventional bridge structures. However, in this thesis it is argued that the application of such approaches is also useful in more common bridge projects to better control risks inadequately treated by design based on code compliance. A framework for a holistic risk-informed approach is provided which focuses on the conceptual design of bridge structures and on the control of risks from accidental hazards. Case studies are conducted to highlight the usefulness of the approach and to help develop crucial aspects of the approach while providing useful background information for its possible implementation in future projects. Specific attention is also paid to the modeling of risks from heavy goods vehicle (HGV) impacts to bridge substructures – a design situation which was found to be inadequate treated using current codified approaches

Robustness analysis of bridge when exposed to train collision due to derailment

This paper considers evaluation of structural robustness for a multi-span concrete bridge crossing multiple rail tracks, in particular the effect of extraordinary exposures on the bridge system. A case study is performed investigating the bridge system’s response to a train collision caused by derailment in an area near the bridge supports. The probability of such an event occurring is estimated from derailment statistics on the railway net. An examination of subsequent propagating actions is carried out based on mechanical and structural considerations. Conclusions drawn here concern the issues of low probability exposures with high con-sequence and possible strategies for increasing overall robustness of these types of bridges

Determining Appropriate Design Impact Loads to Roadside Structures Using Stochastic Modeling

The design and verification of built structures requires structural engineers to consider accidental loading situations. The accidental loading situation investigated in this paper is heavy-goods vehicle (HGV) collisions with roadside structures; focus is on the design of bridge-supporting structures. The impact loads were determined from Monte Carlo simulations of a probabilistic model in which highway traffic measurements and accident statistics in Sweden are input. These loads were calculated for structures adjacent to straight roads as well as roads with curvature, and include considerations of the directional load components. Comparisons were made between the simulation results and approaches given in design codes, with focus on the Eurocode. The simplified approaches provided in the code were inadequate in their treatment of these design situations. Alternative equations for calculating impact forces and energies are presented. These equations can be used for determining design values for impact forces or for conducting probability/risk-based assessments of bridge supports subjected to HGV impacts. In this way, a more consistent treatment of HGV impacts in the design of bridge structures is achieved