Waters flowing in streams and rivers have the ability to scour channel beds, to carry particles (heavier than water) and to deposit materials. This phenomenon of sediment transport can affect substantially the design of reservoirs. The paper describes four case studies of siltation which rendered useless water storage structures in less than 25 years. Although each dam had advanced structural features, the hydrology of the catchment and sediment transport processes were not properly taken into account. The study highlights practical situations in which a reservoir must be analysed as a complete system, taking into account structural features, hydraulics, hydrology, sediment transport, catchment erosion and catchment management. The case studies may used as teaching examples to increase student interest on the significance of sediment transport problems and to emphasise the design procedure to professionals. They may serve also to alert the community at large to basic errors caused by improper soil conservation policy and the inability to predict sediment-load process.
This paper presents the development of a generic framework for asset maintenance management. The work included reviewing the operating characteristics and functions of three commercial software packages currently used for asset management. Based on the advantages and disadvantages of the software, a framework model is presented in the form of an IDEF0 process model that served to illustrate the interaction and dependencies among diverse sets of knowledge areas. Ce document expose le développement d'une structure générique de gestion du maintien des immobilisations. Les travaux comprenaient l'examen des caractéristiques d'exploitation et des fonctions de trois (3) progiciels commerciaux qui sont actuellement utilisés aux fins de la gestion des actifs. On présente un modèle de structure d'encadrement, fondé sur les avantages et les inconvénients du logiciel, sous la forme d'un modèle de processus à méthodologie de définition intégrée zéro (DÉFI 0), qui a permis d'illustrer l'interaction entre divers ensembles de secteurs de connaissances ainsi que leurs dépendances. RES
Culverts are among the most common hydraulic structures. Modern designs do not differ from ancient structures and are often characterised by significant afflux at design flows. A significant advance was the development of the Minimum Energy Loss (MEL) culverts in the late 1950s. The design technique allows a drastic reduction in upstream flooding associated with lower costs. The development and operational performances of this type of structure is presented. The successful operation of MEL culverts for more than 40 years is documented with first-hand records during and after floods. The experiences demonstrate the design soundness while highlighting the importance of the hydraulic expertise of the design engineers.
The durability of concrete structures can be defined as their ability to sustain the serviceability for which they were designed. Today's practicing engineer therefore, pays particular attention to the types of deterioration that could threaten preserving the designed function of a structure. The complexities involved in current designs, the proliferation of new materials and services and hygienic requirements however, make the design engineer's job demanding. La durabilité des structures en béton peut être définie comme la capacité de ces ouvrages à maintenir l'aptitude au service pour laquelle ils ont été conçus. Aujourd'hui, les ingénieurs praticiens accordent donc une grande attention aux mécanismes de détérioration qui pourraient menacer le maintien des fonctions théoriques des ouvrages. La complexité des conceptions actuelles, la prolifération de nouveaux matériaux et services et les exigences sanitaires rendent toutefois le travail de l'ingénieur-concepteur particulièrement exigeant. RES
Rework has been identified as a major contributor to cost and schedule overrun in construction projects. Previous studies that have examined rework are based on a limited data sets and thus eschew generalizations being made about the key determinants. Using data from 260 completed building (n=147) and civil engineering (n=113) projects, path analysis is used to develop a structural model of the most significant causes of rework. The model revealed that the paths of client-directed changes, site management and subcontractors, and project communication were statistically significant contributors to rework costs. The analysis confirmed that the lack of attention to quality management resulted in higher rework costs being incurred in the projects sampled. The analysis also revealed that there were no significant differences between building and civil engineering projects in terms of the direct and indirect cost of rework experienced, and the effectiveness of the project management practices implemented. Considering the findings, it is suggested that generic strategies for reducing the incidence rework in construction and civil engineering projects can be developed.
Many industrial floors are required to have high-quality flat surfaces for the operation of specialized equipment, particularly high-reach stackers operating from the surfaces of warehouse floors. For new floors, the essence of floor flatness lies in the manner of finishing and the systematic monitoring of the flatness achieved immediately following construction. Achieving such surfaces in floor slabs however, is quite difficult because of the moisture and temperature gradients that cause them to curl at the joints. Such curling seriously affects the operation of an industrial facility. Floors subjected to heavily loaded forklift traffic may rapidly deteriorate, causing safety problems. Curling is also exacerbated in industrial floors by the use of power-troweled surface hardeners to produce the dense high-strength top surface required for high wear resistance. Repair of curled floors in industrial locations involves grinding, patching, installation of dowels, and grouting underneath the curled slab. The timing and appropriateness of the method used are of vital importance to the durability of the repair. Aspects of design and construction to minimize curling of new industrial floors, the factors that contribute to cracking and curling, measures to minimize curling, and the repair of curled floors are discussed in this paper.
High wind events such as hurricanes and storms often cause severe damage to crest-fixed thin steel roof claddings. Past research on wind damage has shown that low cycle fatigue cracking of steel roof sheeting around the fastener holes has been the reason for the premature pull-through failures of roof claddings under fluctuating wind forces. Such a situation will be at its worst if the roof sheeting is already split at the fastener holes. An inspection of trapezoidal steel roofs has shown that roofing has been split in the transverse direction due to accidental or poor workmanship-caused overtightening of screw fasteners. Once split, even slightly, the roofing can only survive a few cycles of wind uplift loading. Therefore an investigation using laboratory experiments and finite element analyses was carried out to study the splitting behaviour of two commonly used high tensile steel trapezoidal roof claddings. Analytical and experimental results agreed reasonably well and presented a good understanding of the splitting behaviour of trapezoidal roof claddings. This paper presents the details of this investigation and the results.
A large number of specialty repair concrete products are currently marketed and new products are being continually introduced leaving clients, engineers, and designers bewildered. The paucity of information on the mechanical and thermal properties of a given product complicates material selection. These difficulties force designers to adopt materials that have properties close to those of the original concrete. In so doing they often reject advantages offered by polymer-based products now on the market. The challenge is to understand the properties of each material and select the appropriate one. To assure predictable performance, the designer must have a good knowledge and understanding of the properties of the repair material, how it will interact with the environment in service, and a clear description of maintenance procedures and intervals. Typical properties of currently used polymeric materials in relation to the important aspect of selection based on compatibility with in-service conditions and suitability with the application procedures of the job are discussed.
Sprinkled surface hardeners are incorporated into freshly placed concrete slabs while high-strength overlays are placed on a previously poured new concrete slab or an existing deteriorated slab, providing improved abrasion and impact resistance. Metal filings are combined with cement corrosion inhibitors and water-reducing admixtures. Depending on the intended application, the metallic particles may either be treated with chemicals or directly sieved and graded. Rusting of metallic surface hardeners can occur when the installation of these products or the conditions during installation are not closely controlled. Visual tests, including microscopy and chemical analysis, were employed to investigate some of the potential factors that contribute to the rusting problem. Observations and possible causes contributing to the rusting and debonding problems are identified: (1) a decrease in the alkalinity of the cement paste due to carbonation; (2) exposure of unprotected metallic particles to air during the brushing procedure; and (3) timing of the finishing operations.
Henry Petroski, the Aleksander S. Vesic Professor of Civil Engineering and Professor of History, Duke University, one of this generation’s most readable and influential authors of published works on engineering history, has done it again. This volume is another Petroski contribution that simply must be added to your library. To Forgive Design: Understanding Failure explores a multitude of topics that apply historic experience to contemporary design in the unique style common to his writings. Petroski’s creative insights are legendary and frequently cited by design and construction professionals and academics worldwide. This book continues the tradition; it will not disappoint the reader.
The underlying theme of To Forgive Design: Understanding Failure is clear: “Successful change comes not from emulating success and trying to better it, but from learning from and anticipating failure, whether actually experienced or hypothetically imagined.” In exploring this theme, Henry Petroski provides fascinating examples, from pop-top cans to the Titanic and from little boys playing with string and chewing gum over sidewalk grates to major catastrophic oil spills. As always, Petroski demonstrates skill in writing for a wide range of audiences. The book can easily be read, understood, and appreciated by the lay public, as well as by engineers of all technical specialties.
The most widely used construction material for engineered structures in the world is RC, and the primary component of RC is, of course, concrete. Although not as widely appreciated as it should be, concrete is perhaps the most nuanced of all construction materials; although it is essential that practicing engineers understand its basic properties and limitations, an understanding of its nuances is indispensable for engineers in the practice of forensic engineering. Failure of RC structures is as often attributable to materials performance as it is any other cause. Neville’s Properties of Concrete is a must have for any engineer or practitioner involved in portland cement construction, troubleshooting, or forensic engineering. It is a practical guide hewn from in-depth appreciation and consideration of the principles of concrete technology. In this age of Internet searches done for quick information but not knowledge, Neville’s treatise provides a reliable essential reference for almost everything concrete.
Concrete is different from many other construction materials in that it is usually batched at or near job sites and not fabricated in factories or manufacturing facilities and placed and finished in the field. Quality, and thus its nuance, is almost exclusively dependent on project-to-project materials selection and acquisition and on workmanship during construction in variable environmental conditions. Moreover, the performance requirements for concrete are highly variable from project to project. Therefore, engineering supervision on the site and during mix development is essential if the engineer’s design intent is to be achieved in the as-built structure. Neville’s Properties of Concrete provides engineers with essential information for understanding the principles of concrete, solving concrete-related problems, avoiding common pitfalls, and assessing its in-field performance.
Environment, society, and economy are the three pillars of sustainability. The five chapters of the book discuss current challenges facing human society, and how construction practitioners address these challenges using concrete through the process of design, construction, operation, and end-of-life. The sustainability credentials of concrete are introduced in Chapter 1, and detailed in Chapter 2 responding to climate change, resource depletion, social progress, and economic growth. Without a doubt, the man-made stone is strong, durable, robust, and versatile to resist flooding and wind damages, and also satisfies aesthetics requirements. Concrete as a construction material functions well in buildings by withstanding chemical treatments, providing fire resistance, supplying higher thermal mass, and offering acoustic barriers. In addition, the cement and concrete industry plays a critical role in the economic growth of the world. Georgopoulos and Minson use specific numbers cited from research completed by Capital Economics (p. 41) to underline the contribution of the cement and concrete industry to the U.K. economy. Skeptics might argue that the manufacturing of cement and concrete devours natural resources, and it is an energy and emission intensive process. However, advanced technologies have already furnished the cement and concrete industry with alternative energy and improved efficiency to reduce fossil fuel consumption and greenhouse gas emissions. The embodied carbon dioxide of concrete is comparable with, or much less than, timber and steel per unit volume or unit mass (p. 26). Concrete can be recycled to reduce the depletion of virgin aggregates. In addition, it is not difficult to restore the limestone and aggregate quarries, and interestingly, the book points out that quarrying actually helped find several significant archaeological sites in Britain.
After justifying the sustainability potential of concrete in the first two chapters, Georgopoulos and Minson move the discussion further in Chapters 3–5 utilizing concrete to build sustainable buildings and infrastructure. Conceptual design not only influences the construction program, but also has substantial impact on sustainability of the project. Chapter 3 details how to apply integrated design and employ concrete structural systems (i.e., substructures, vertical, and horizontal systems, cladding and roof structures) in design to achieve a sustainable building, and proposes innovative solutions using cementitious materials and concrete to design infrastructure (brownfield remediation, pavements, pipes, bridges, urban drainage systems, and foundations of wind turbines). Designers and engineers may need conceptual design tools to aid them in selecting sustainable structural systems. The free software Concept developed by U.K. Concrete Centre is introduced in Chapter 3 (p. 79), which facilitates the selection of optimal concrete slab or frame for a multistory building. The readers can follow the link provided in the reference to download the software and explore the benefits of this design planning Concept tool.
In 2009, a 13-story residential building founded on lightly reinforced prestressed high-strength concrete (PHC) pipe piles in Shanghai collapsed completely during the excavation of an adjacent underground garage (i.e., on the southern side). In the course of construction, excavated soil had been dumped on the northern side of the building and formed a 10-m-high fill slope before the collapse. In order to identify the principal cause of the sudden building collapse, an extensive field investigation was carried out immediately after the accident. In addition to geotechnical exploration of soil properties, physical evidence was collected and documented including the layout of collapse debris, damage to piles, and induced pile movements. To assist in the investigation and provide insights into the collapse, three-dimensional finite-element analysis was carried out to simulate the process of excavation and dumping. For piles located adjacent to the dumped soil on the northern side of the building, uppermost fractures could be seen near the interface between the reinforced and unreinforced sections, which were located approximately 1-2 m below the original level of the pile head. Most of these failure surfaces were flat, implying that these piles failed under tension. For piles situated on the excavation (southern) side of the collapsed building, the uppermost fracture surfaces were tilted at an angle and the concrete was severely damaged, suggesting that these fractures occurred mainly from compression. Photographs of the pipe interior taken with a high-resolution digital camera and results of a low-strain pile integrity test revealed that most piles examined had generally broken into three or more sections. According to results of the numerical analysis, the largest bending moment was developed in the piles on the excavation side of the building at a depth corresponding to the interface of the soft and firm-stiff clay layers (13.5 m below the ground surface), under the combined effect of excavation and dumping. This suggests that the failure occurred first for piles on the excavation side, and eventually caused the building to fall flat onto the excavation site. A lesson learned from the accident is that geotechnical engineers and contractors should be better trained to improve their understanding of the effects of surcharge loading on PHC piles. Moreover, proper construction procedures and site supervision schemes should be explicitly spelled out and strictly followed by all parties during construction.
To investigate the dynamic responses and damage modes of the dome of a liquefied natural gas (LNG) storage tank under aircraft impact, a finite-element (FE) model of a 160,000-m3 LNG storage tank for an actual LNG project and two kinds of aircraft was established. Through comparison of the results of a numerical simulation and an impact perforation test, the accuracy of the numerical simulation method and the material model were confirmed. The FE model of the aircraft also was validated, based on the Riera method. The dynamic responses and failure phenomena of the dome and wall of the LNG tank under aircraft impact were studied, respectively. Based on the simulation results, the influence of the reticulated shell on the antishock capability of the dome was evaluated. The numerical results revealed that the LNG outer tank was able to resist the impact of a Bombardier Challenger 850 and a Boeing 757 flying at 100 m/s; the ability to withstand shock loading was improved greatly by the combined effects of the concrete and reticulated shells. However, when the Bombardier Challenger 850 aircraft hit the tank wall at 100 m/s, the aircraft penetrated into the LNG outer concrete structure. More seriously, when the Bombardier aircraft hit the ring beam, in addition to the penetration damage at the direct impact site, there was a wide range of collapse near the breakdown hole, and the structure was severely damaged.
The influence of the American engineer George Washington Whistler on the design of the St. Petersburg-Moscow Railway, called the Nikolaev Railway, is discussed. The line, built between 1842 and 1851 and approximately 644 km long, was the first large-scale implementation of railroad transportation in Russia. Whistler recommended a 1,524-mm (5-ft) railroad gauge, which was accepted by the Tsar. He helped design the railway's first freight and passenger steam locomotives, and he helped organize the manufacturing facility for the production of locomotives and other rolling stock. Because Whistler had successfully built a pioneering Howe truss bridge for the Western Railroad over the Connecticut River in Springfield, Massachusetts in 1841, he was able to persuade Russian engineers to adopt the Howe form for the Nikolaev Railway's 64 major bridges. The design of the Connecticut River Bridge inspired the renowned Russian engineer Dmitry Jouravsky to perform over 8 years of study on the Howe form. Jouravsky's contributions to structural engineering and his design adaptations are discussed in the context of the Connecticut River Bridge.
A successful engineering project must include its timely and economic completion. Aproject management failure can lead to delays and cost overruns. One example of a project that greatly exceeded its projected budget is the construction of the multiple facilities for the 1976 Olympic Games in Montreal. These included the Olympic Stadium, a velodrome for bicycle events, and the Olympic Village to house the athletes. This case study reviews the circumstances of the cost increases and the design decisions and other circumstances that led to them. The difficulties were brought on by an unrealistic schedule to complete the facilities before the fixed start date of the Games, combined with an unusually cavalier attitude toward project costs, exacerbated by political tensions. Although the original cost estimate for the facilities was $120 million, the final cost was $1.5 billion, with $830 million for the main stadium alone. Part of the justification for the expense of the facilities was the hope that the facilities would be useful for future athletic events-the record on this is mixed at best. The lessons learned can be applied to other projects to better control costs. (C) 2013 American Society of Civil Engineers.
Apart from the anticipated damage to unreinforced stone and masonry chimneys, some disturbing results were observed in the June 28, 1992 earthquakes; namely, the unsatisfactory performance of recently built residential struc tures, some of which were clearly deficient, despite being subject to code-enforcement procedures, and others that were in substantial compliance with the building codes. The fact that building standards, as reflected in the codes, have been subjected to stepwise developments over the last 60 years has produced a stock of buildings that possess a range of seismic resistance. However, it would be expected that, in general, the newer structures would perform better than the older ones. Experience in the Big Bear Lake area has shown departure from this pattern in several categories. One comprises buildings that failed prematurely, almost certainly as a result of negligent construction. A second includes buildings where failure appears to have been brought about by deficiencies that the codes do not address. Recent case studies are used to illustrate these disturbing facts.
The 1995 Hyogo-ken Nanbu (Kobe), Japan earthquake provided the world's first experience with earthquake damage to new long-span bridges designed to 1990s seismic standards. This paper reviews damage and describes techniques used to repair three major steel bridges along the Wangan route (Bayshore route) in Kobe-the 885 m Higashi-Kobe Bridge, the 217 m Rokko Island Bridge, and the 252 m Nishinomiya Port Bridge. These bridges, in service for less than three years, were essential components in the highway transportation system in the Kobe region. Extremely large ground motions, and failure of bearings, connections, and seismic restrainers were principal contributors to the damage sustained by these bridges. Repairs utilized heavy-lift floating cranes (up to 4,100 ton capacity) and various jacks to stabilize the structures and to realign spans. In one case, reconstruction of a collapsed span was required, with lifting weight a prime concern. Significant constraints on the repair included confined working space and requirements for maintaining maritime navigational clearances. The closure times for the repair of the bridges ranged from three to nine months.
The ASCE Technical Council on Forensic Engineering (TCFE) traditionally selects one paper published in this journal during the previous calendar year for our Outstanding Paper Award. This year, the Publications Committee, the Awards Committee, and the TCFE Executive Committee unanimously selected two equally outstanding papers for the award. One paper is from our special issue Analysis of Structural Failures Using Numerical Modeling, and the other was chosen from the remaining five issues published in 2013. The award recipients are Gianni Bartoli and Michele Betti; and Clay Naito, Daniel Cox, Qi-Song “Kent” Yu, and Hillary Brooker. Award certificates will be given to each recipient, and they will be recognized at the Seventh ASCE Forensic Engineering Congress in New York City.
As indispensable electric power equipment in substations, high-voltage power transformers have experienced severe damage in past earthquakes. This paper illustrates an earthquake-damaged 500-kV power transformer: all three 550-kV bushings fractured, oil conservator supports were sheared off, and leaked transformer oil caused a fire. A detailed finite-element model of the power transformer was developed. The modal and response-history analyses using the finite-element model were conducted to investigate possible reasons for the power transformer earthquake damage. The results indicated that the local modes of the transformer components, such as bushings and turrets, and the oil conservator dominate the power transformer vibration. Spectral accelerations at the top flange plates of the turrets on the transformer tank were significantly amplified for the transformer bushings. Peak resultant bending moments at the bottoms of the air-side insulators of the 550-kV bushings subjected to the Wenchuan earthquake motions exceeded their bending capacities. Accelerations for the oil conservator were also greatly amplified, thus the oil conservator supports suffered large translational and torsional deformations to the earthquake motions. It is concluded from the earthquake damage and seismic analyses that this type of power transformer is vulnerable to strong earthquakes because the earthquake effect is not adequately considered in the power transformer structural design.
A large number of stairways experienced minor to extreme damage during Wenchuan Earthquake (Ms=8.0) that shook northwestern Sichuan on May 12, 2008. A postearthquake field reconnaissance on buildings was carried out in the epicentral region. Typical stairway configurations identified in the epicenter areas and the corresponding damage experienced are discussed in this paper. Various types of seismic damage to the stairway components or the primary structures occurred because of the interaction between the stairways and the primary structural systems. The primary structures were affected by the formation of short columns or short beams and high local shear stresses in the floor diaphragms and beam-column joints of the stairwells. Stairway components were vulnerable to seismic actions where the distresses included cracking or spalling of concrete, buckling of reinforcing bars in the middle of the flights or at the stair flight-landing junction, high local stresses in the landing slab of L-shaped stairways and in the middle of landing beams, and stress concentration at the corner of Z-shaped stringer. Brittle stair enclosures and finish materials were particularly hazardous due to their falling debris.
This paper presents the findings from both the detailed site investigations and the computational analyses on the Zipingpu concrete-faced rockfill dam (CFRD), a 156-m high dam in which 100-cm permanent settlement and 60-cm horizontal displacement occurred during the 2008 Wenchuan, China, earthquake. The Zipingpu CFRD was 17 km away from the epicenter and was considerably damaged by the Wenchuan earthquake. It was estimated that the peak acceleration in the top of the dam along the axial and vertical direction was about 20.0∈∈m/s2, and the peak acceleration at the river level was about 16.0∈∈m/s2. It was calculated that peak acceleration of dam bedrock was more than 5.0∈∈m/s2, and the intensity (Chinese scale) was more than IX. Based on an in-situ investigation, the peak value of settlement of the dam crest reached 744.3 mm, and the peak value of horizontal displacement toward the right and left abutment are 226.1 mm and 106.8 mm, respectively. The actual experience of the peak acceleration and seismic intensity of the Zipingpu CFRD in this earthquake was considerably beyond criteria used for the original design standards. To simulate the seismic activity and damage, a three-dimensional (3D) numerical model of the Zipingpu CFRD is established and the numerical simulation analysis of Wenchuan earthquake damage is presented. The calculated results show that the numerical analyses are consistent with the in-situ investigation. The seismic performance of the Zipingpu CFRD during the Wenchuan earthquake is reproduced in the numerical model. The acceleration response, permanent deformation, and damage characteristics of the Zipingpu CFRD in the Wenchuan earthquake are understood as a result of this study. It should also be highlighted that the valuable and rare data from the seismic response of such a large dam will be useful for further case studies.
