Time filter

Source Type

Varney J.C.,Huitt Zollars Inc. | Brown M.D.,WDP and Associates | Bayrak O.,Environmental and Architectural Engineering | Poston R.W.,WDP and Associates
ACI Structural Journal | Year: 2011

The performance of improperly constructed beams is of particular concern in the repair of concrete structures. Not only is there uncertainty about the actual as-built strength and what measures may improve capacity, but also the presence of improper structural details may lead to litigation concerning what structural repairs are really necessary to restore perceived loss of strength. For the specific case of shear, there is value in knowing a reasonable and safe approximation of the shear capacity of improperly detailed beams. To study the effect of improperly anchored stirrups on the shear strength of reinforced concrete beams, four 13 × 24 in. (330 ×610 mm) reinforced concrete sections were fabricated with varying proper and improper shear reinforcement details and loaded to failure. Current ACI 318 and AASHTO LRFD code provisions were used to compare the resulting failure loads from tests with calculated nominal capacities. The experimental results suggest that reinforcement anchorage, as tested, has no significant effect on the shear capacity of a reinforced concrete section. © 2011, American Concrete Institute. All rights reserved.

Garber D.B.,Florida International University | Gallardo J.M.,Technological University of Panama | Deschenes D.J.,Simpson Gumpertz | Bayrak O.,Environmental and Architectural Engineering
ACI Structural Journal | Year: 2016

A comprehensive experimental database containing 237 specimens from 27 different research studies was assembled during a larger research effort undertaken at the University of Texas at Austin to investigate three different short-term loss and four different longterm loss estimation procedures. The assembled database was filtered to eliminate specimens with incomplete information or those not adequately representing those found in the field (as a result of either being too small or overstressed at release). The specimens contained within this filtered database offered a diversity of characteristics well representative of beams found in bridges. This database was used to evaluate several different short-and longterm loss estimation procedures. The results of these evaluations can help to aid the designer in selection of an appropriate procedure for estimating prestress loss. © 2016, American Concrete Institute. All rights reserved.

Tuchscherer R.,Datum Engineers Inc. | Birrcher D.,International Bridge Technologies Inc. | Huizinga M.,Thornton Tomasetti | Bayrak O.,Environmental and Architectural Engineering
ACI Structural Journal | Year: 2010

The purpose of the testing program described in this paper was to evaluate the benefits of triaxial confinement that occurs when the loaded area of a strut-and-tie model (STM) is surrounded by concrete on all sides. To achieve this goal, five full-scale beams were fabricated and tested at the Ferguson Structural Engineering Laboratory in Austin, TX. Specimens were tested with a span-depth ratio (a/A) of 1.85. Two ends of each beam were tested, resulting in a total of 10 tests. Eight tests were conducted on beams with a 21 × 42 in. (530 × 1070 mm) cross section, and two tests were conducted on beams with a 36 × 48 in. (910 × 1220 mm) cross section. The primary experimental variables were the size of the load- and support-bearing plates and the amount of web reinforcement. Based on the results of the testing program, it is recommended that the permissible nodal stresses of an STM be increased for nodes triaxially confined by concrete. Copyright © 2010, American Concrete Institute. All rights reserved.

Champion C.,ZFA Structural Engineers | Liel A.,Environmental and Architectural Engineering
Earthquake Engineering and Structural Dynamics | Year: 2012

Forward directivity may cause large velocity pulses in ground motion time histories that are damaging to buildings at sites close to faults, potentially increasing seismic collapse risk. This study quantifies the effects of forward directivity on collapse risk through incremental dynamic analysis of building simulation models that are capable of capturing the key aspects of strength and stiffness degradation associated with structural collapse. The paper also describes a method for incorporating the effects of near-fault directivity in probabilistic assessment of seismic collapse risk. The analysis is based on a suite of RC frame models that represent both past and present building code provisions, subjected to a database of near-fault, pulse-like ground motions with varying pulse periods. Results show that the predicted collapse capacity is strongly influenced by variations in pulse period and building ductility; pulse periods that are longer than the first-mode elastic building period tend to be the most damaging. A detailed assessment of seismic collapse risk shows that the predicted probability of collapse in 50years for modern concrete buildings at a representative near-fault site is approximately 6%, which is significantly higher than the 1% probability in the far-field region targeted by current seismic design maps in the US. © 2012 John Wiley & Sons, Ltd.

Mohanram A.,University of Hawaii at Manoa | Ray C.,University of Hawaii at Manoa | Harvey R.W.,U.S. Geological Survey | Metge D.W.,U.S. Geological Survey | And 3 more authors.
Water Research | Year: 2010

In order to gain more information about the fate of Cryptosporidium parvum oocysts in tropical volcanic soils, the transport and attachment behaviors of oocysts and oocyst-sized polystyrene microspheres were studied in the presence of two soils. These soils were chosen because of their differing chemical and physical properties, i.e., an organic-rich (43-46% by mass) volcanic ash-derived soil from the island of Hawaii, and a red, iron (22-29% by mass), aluminum (29-45% by mass), and clay-rich (68-76% by mass) volcanic soil from the island of Oahu. A third agricultural soil, an organic- (13% by mass) and quartz-rich (40% by mass) soil from Illinois, was included for reference. In 10-cm long flow-through columns, oocysts and microspheres advecting through the red volcanic soil were almost completely (98% and 99%) immobilized. The modest breakthrough resulted from preferential flow-path structure inadvertently created by soil-particle aggregation during the re-wetting process. Although a high (99%) removal of oocysts and microsphere within the volcanic ash soil occurred initially, further examination revealed that transport was merely retarded because of highly reversible interactions with grain surfaces. Judging from the slope of the substantive and protracted tail of the breakthrough curve for the 1.8-μm microspheres, almost all (>99%) predictably would be recovered within ~4000 pore volumes. This suggests that once contaminated, the volcanic ash soil could serve as a reservoir for subsequent contamination of groundwater, at least for pathogens of similar size or smaller. Because of the highly reversible nature of organic colloid immobilization in this soil type, C. parvum could contaminate surface water should overland flow during heavy precipitation events pick up near-surface grains to which they are attached. Surprisingly, oocyst and microsphere attachment to the reference soil from Illinois appeared to be at least as sensitive to changes in pH as was observed for the red, metal-oxide rich soil from Oahu. In contrast, colloidal attachment in the organic-rich, volcanic ash soil was relatively insensitive to changes in pH in spite of the high iron content. Given the fundamental differences in transport behavior of oocyst-sized colloids within the two volcanic soils of similar origin, agricultural practices modified to lessen C. parvum contamination of ground or surface water would necessitate taking the individual soil properties into account. © 2010.

Caini M.,Environmental and Architectural engineering | Paparella R.,Environmental and Architectural engineering
CESB 2013 PRAGUE - Central Europe Towards Sustainable Building 2013: Sustainable Building and Refurbishment for Next Generations | Year: 2013

Recently, a sensibility directed to the re-use of the vast and diffused building patrimony for the industrial production developed in Europe. Originally built in the second half of the 19th and last century, such patrimony is now disused due to processes of economic transformation and urbanism. Even though considered minor buildings nevertheless, such buildings carry historic-cultural values which are recognized and appreciated. The idea of re-using these buildings is linked to the historical memories, which tend to enhance the cultural identity of a determined territory. However, a further challenge is added; the realization of redevelopments based on sustainable criteria. Through the analysis of case studies in the North-East of Italy, this work proposes to identify sustainable criteria of intervention for this building patrimony. Industrial buildings such as spinning and cotton mills have been analyzed; this paper focuses exclusively on spinning mills. In these cases, sustainability is intended in its wide meaning, it therefore regards: the application of the criterion of "least land consumption" the identification of the building's characteristics; the application of the criterion of the reuse compatible with the materials and the construction techniques of the building; the introduction of compatible and innovative technologies that can be integrated without altering of the historical characteristics of the building itself. From this detailed analysis, it is possible to extrapolate guidelines for a sustainable planning in this particular and specific context. Central Europe towards Sustainable Building 2013.

Caini M.,Environmental and Architectural engineering | Paparella R.,Environmental and Architectural engineering
CESB 2013 PRAGUE - Central Europe Towards Sustainable Building 2013: Sustainable Building and Refurbishment for Next Generations | Year: 2013

What today is considered as innovation, will become of routine in 2020. Therefore, there is the need to teach the future engineers to conceive and plan sustainable buildings. Sustainability must consider the following multiple aspects: energetic efficiency, the possibility of planning buildings to zero consumption, the sustainable use of renewable and not renewable resources, their recycle and the use of products deriving from other productive cycles and reusable for the creation of the building itself. For such aim it is necessary to introduce in the basic formation of the engineering planning student a multidisciplinary planning approach. This work is based on the results of a bioclimatic planning research carried out by the authors in communion with their own didactic experience in the course of Technical Architecture for Building Engineering-Architecture engineers. This work pinpoints the criteria and the contents that must be followed and introduced in the students' formative curricula, with the purpose of obtaining a designer able to plan and realize sustainable buildings. In the light of didactic experiences acquired in developing countries, this work also pays attention to the specific criteria that must be kept under consideration for the formation of engineers that will operate in such contexts.

Simoni L.,Environmental and Architectural Engineering | Schrefler B.A.,Environmental and Architectural Engineering
Advances in Applied Mechanics | Year: 2014

We present as areas of interest for multifield fracturing thermomechanical fracturing, fluid pressure induced isothermal and nonisothermal fracturing, fracturing due to radiation, drying, hydrogen embrittlement, and fractures induced by chemical effects. We discuss the most appropriate constitutive models for their simulation and choose the cohesive fracture model for quasi-brittle materials. Successively we show governing equations for a thermo-hydro-mechanical problem, which is representative for multifield problems. Possible extensions to more fields are addressed. Then methods for numerical modeling of multifield fracturing are presented and the most representative ones, i.e., interface and embedded discontinuity elements, X-FEM, thick level set and phase field models, and discrete crack approach with adaptive remeshing are discussed in some detail. After incorporating this last method in the governing equations, their numerical solution is shown together with the necessary adaptivity in time and space. This solution is validated. Successively applications to thermomechanical fracture; hydraulic fracturing in case of a pumped well and of 2D and 3D dams; fracturing of drying concrete and of a massive concrete beam and finally mechanical effects of chemical processes in concrete are shown. In the case of the pumped well with constant pumping rate, a comparison between an Extended Finite Element solution and that of the discrete crack approach with adaptive remeshing is made which allows for interesting considerations about the nature of hydraulic fracturing. The examples permit to conclude that with increasing complexity of the multifield problems that of the employed fracture models decreases, i.e., advanced fracture models have to date only been applied to problems with a limited number of fields, mainly displacement, thermal and/or pressure fields. There is hence plenty of room for improvement. © 2014 Elsevier Inc.

Elwood E.D.,Environmental and Architectural Engineering | Corotis R.B.,Environmental and Architectural Engineering
12th International Conference on Applications of Statistics and Probability in Civil Engineering, ICASP 2015 | Year: 2015

Within the field of earthquake engineering, there is a desire to identify observed trends of building damage in response to seismic events. Regional loss models, post-earthquake safety evaluations, and rapid screening of structures for potential seismic hazards all utilize "patterns" of expected building behavior in some form. Due to the intrinsic uncertainties in the prediction of earthquake events and building response to these events, the identification of building damage patterns is a complex problem. Further, virtually every building is unique in configuration and characterized by varying site conditions. This research paper presents a unique application of fuzzy set theory within the domain of fuzzy classification (fuzzy clustering) to investigate whether seismic building damage patterns, often expressed linguistically, can be identified from empirical data. Information used in the classification analysis consists of building damage data from the 1994 Northridge Earthquake for concrete structures.

Corotis R.B.,Environmental and Architectural Engineering | Bonstrom H.,Environmental and Architectural Engineering
12th International Conference on Applications of Statistics and Probability in Civil Engineering, ICASP 2015 | Year: 2015

In this paper, an initial analysis is performed to assess the potential loss to a building portfolio subjected to multiple, independent hazards. The procedure extends prior research that uses the First Order Reliability Method (FORM) to analyze the vulnerability of a portfolio of buildings to a seismic hazard. The paper includes discussion of issues to consider for community-wide damage measures and dependencies. The results are applied to Charleston, South Carolina, a community that has both seismic and hurricane hazards.

Loading Environmental and Architectural engineering collaborators
Loading Environmental and Architectural engineering collaborators