Mashnad M.,Walter P. Moore and Associates Inc. |
Jones N.P.,Pennsylvania State University
Journal of Wind Engineering and Industrial Aerodynamics | Year: 2014
Long-span structures are susceptible to wind-induced vibrations due to their low oscillation frequency and low mechanical damping. Although many efforts have been made in the past to model vortexinduced vibration of circular cylinders, limited studies can be found for non-circular cross sections representative of long-span bridge decks. A model for vortex-induced vibration analysis of long-span bridge is presented in this paper. The aeroelastic equation of motion of the model, a procedure to extract aeroelastic coefficients from wind tunnel experiments, analysis of full-scale structures incorporating loss of spanwise correlation of aeroelastic forces, and comparison between simulated and full-scale measured responses on a twin deck bridge (Fred Hartman bridge, Baytown, Texas) are discussed. Six bluffsections-Deer Isle bridge, Tsurumi bridge, Fred Hartman bridge, generic rectangular, H shaped, and circular models-were considered in this research program. © 2014 Elsevier Ltd. All rights reserved.
Waggoner M.C.,Walter P. Moore and Associates Inc.
Structures Congress 2011 - Proceedings of the 2011 Structures Congress | Year: 2011
In 2007 Walter P Moore relocated its corporate headquarters in Houston, TX, in 2007 to three floors in a tall building in downtown Houston designed by the firm. Working with the architecture firm Gensler, initial planning efforts identified the need to connect the workflow of the office via a new, common central stair atrium cut into the existing floor plates. The final design for the stair was chosen from an internal design competition that sought to identify a lightweight, progressive structural solution that highlighted the creative abilities of the firm. The design implemented for the stair consists of a cantilevered, stringerless arrangement that takes advantage of the intrinsic elements that exist functionally in a stair by rewriting the structural behavior of the stair through manipulation of the boundary support conditions. Using this design framework, individual elements of the stair were minimized through the use of high performance materials, including ultra-high performance fiber reinforced concrete (UHPFRC) and high strength steel cables. In addition to the optimization process that enabled the ultra-thin sections, a unique approach to vibration design was taken. The stair was intentionally designed to be somewhat flexible, allowing a platform for discussion of vibration perception topics with the clients who visit the office. The stairs are outfitted with a small tuned mass damper (TMD) and instrumented with accelerometers whose output is displayed on a large screen at the bottom of the stair. © ASCE 2011.
Haselton C.B.,California State University, Chico |
Liel A.B.,University of Colorado at Boulder |
Deierlein G.G.,Stanford University |
Dean B.S.,Walter P. Moore and Associates Inc. |
Chou J.H.,Quincy Engineering Inc.
Journal of Structural Engineering | Year: 2011
This study applies nonlinear dynamic analyses to assess the risk of collapse of RC special moment-frame (SMF) buildings to quantify the seismic safety implied by modern building codes. Thirty archetypical RC SMF buildings, ranging in height from 1 to 20 stories, are designed according to ASCE 7-02 and ACI 318-05 for a high-seismic region. The results of performance-based seismic assessments show that, on average, these buildings have an 11% probability of collapse under ground motion intensities with a 2% probability of exceedance in 50years. The average mean annual rate of collapse of 3.110-4 collapses per year corresponds to an average of 1.5% probability of collapse in 50years. The study further examines the influence of specific design provisions on collapse safety. In particular, changes to the minimum seismic base shear requirement between 2002 and 2005 editions of ASCE 7 and variations in ACI 318 strong-column weak-beam (SCWB) design requirements are investigated. The study finds that the reduction in the minimum base shear, introduced in ASCE 7-05 and subsequently rescinded, dramatically increases the collapse risk of tall (long-period) frame buildings in high-seismic regions. An investigation of the SCWB requirements shows that the current ACI 318 provisions delay, but do not prevent, column yielding and the formation of story collapse mechanisms. An increase in the SCWB ratio above 6/5 (1.2) does not significantly improve performance of low-rise frame buildings but may reduce collapse risk for midrise and taller buildings. This study of modern RC buildings is contrasted with the collapse safety of older (nonductile) RC moment-frame buildings in the companion paper. © 2011 American Society of Civil Engineers.
Mukhopadhyay B.,HDR |
Dutta A.,Walter P Moore and Associates Inc.
Water Resources Management | Year: 2010
Integrated water resources management at river basin scales and evaluation of effects of climate change on regional water resources require quantitative estimates of space-time variability of monthly discharges within a river network. This study demonstrates that such estimates, which can be called stream water availability, for regional river basins with meager or nonexistent gauge data, can be obtained by combining continuity models of hydrological processes, flow routing, and topology of the river basin. The hydrologic processes can be adequately modeled using high quality databases of hydrologic significance. A stream water availability model is presented for Upper Indus Basin (UIB) utilizing the most up-to-date datasets for topography, temperature, precipitation, net radiation, land cover, soil type, and digital atlas. Multiple datasets have been evaluated and the ones with best accuracy and temporal coverage have been selected for the final model. Upper Indus River and its major tributaries are highly significant in regional water resources management and geopolitics. However, UIB is a poorly studied and largely ungauged river basin with an area of 265,598 km2 and extremely rugged topography. Several factors, the chief ones being the challenging terrain and the trans-boundary nature of the basin, have contributed to this knowledge gap. Hydro-climatologically it is a complex basin with a significant cryospheric component. The spatial and temporal variation of the principal climatic variables, namely precipitation, net radiation, and temperature has been thoroughly accounted for in the development of a stream water availability model based on a process model coupled with a topologic model and a linear reservoir model of river flow routing. Model calculations indicate that there are essentially two hydrologic regimes in UIB. The regime that is truly significant in contributing stream flows, originates from the UIB cryosphere containing outstanding glaciers and snowfields. The other regime, generated from wet precipitation and melt water from seasonal snow covers is insignificant due to high rates of infiltration and evaporation in the semi-desert environment prevailing at elevations below perennial snow and ice covers. In general, the modeled stream flow characteristics match with the sparse discharge measurements that are available. Flow in the Indus considerably increases at its confluence with Shyok River and further downstream where other tributaries form the north join the main stem. At or near the outlet of the basin stream flow can vary from less than 800 m3 s-1 in the winter and spring to nearly 8,000 m3 s-1 in the peak summer and can persist to over 1,500 m3 s-1 in the autumn. The importance of snow and glacial melt in Indus River discharge is apparent and any global or regional climate change affecting the equilibrium line elevation of the snow fields in the Karakoram will have a profound influence on the water availability in the Indus. Estimates are made for per capita water availability in Ladakh and Gilgit-Baltistan territories, controlled by India and Pakistan respectively. Geopolitical significance and climate change effects are discussed briefly. © 2010 Springer Science+Business Media B.V.
Williams M.E.,Walter P. Moore and Associates Inc.
American Concrete Institute, ACI Special Publication | Year: 2014
In recent years concrete bridge structures in the USA have been experiencing varied levels of premature concrete deterioration due to alkali-silica reaction (ASR) and related condition delayed ettringite formation (DEF). While these deleterious reactions can affect various concrete bridge members under the right conditions, bridge columns can be notably more susceptible due to their unique exposure conditions and aggressive environments. The degree of deleterious reactions in concrete bridge columns is dependent on susceptibility of the aggregate, and on environmental factors, such as temperature, moisture, and external sources of alkalis. Temperature gradients are known to affect the rate and severity of the ASR expansion. Moisture gradients can be facilitated by high atmospheric humidity, exposure to weather, proximity to water spray from adjacent roadways, malfunctioning joint systems, and/or failed drainage systems, which collectively can provide sufficient conditions for ASR and DEF expansion. This paper suggests that a review of the aggressive environmental conditions at the bridge site can provide valuable insight into the occurrence and progression of premature concrete deterioration and provide direction as to a future course of action for maintenance and repair for concrete bridge columns. Repair procedures are provided dependent on the severity of premature concrete deterioration.
De Luca A.,Walter P Moore and Associates Inc. |
Zadeh H.J.,University of Miami |
Nanni A.,University of Naples Federico II
ACI Structural Journal | Year: 2013
A three-story apartment building on the University of Miami campus, built in 1947 and scheduled for demolition in the spring of 2011, was used as a research test bed. Two identical strips of the one-way reinforced concrete (RC) slab of the first floor of the building were saw cut and load-tested according to the ACI 437-12 load test protocol. After conducting the load test, the slab strips were loaded to failure. This allowed for observations on the margin of safety with respect to failure, a determination that is not generally possible in a proof load test. The analysis of the results provides experimental evidence on the validity of the load test practice for the assessment of structural members.
Lai Z.,Purdue University |
Varma A.H.,Walter P. Moore and Associates Inc. |
Griffis L.G.,Purdue University
Journal of Structural Engineering (United States) | Year: 2016
Concrete-filled steel tube (CFT) beam-columns are categorized as compact, noncompact, or slender depending on the governing slenderness ratio (width-to-thickness b/t or D/t ratio,) of the steel-tube wall. The current AISC specification recommends the bilinear axial force-bending moment (P-M) interaction curve for bare steel members for the design of noncompact and slender CFT beam-columns. This paper compiles the experimental database of tests conducted on noncompact and slender CFT beam-columns, and demonstrates the overconservatism of the AISC P-M interaction curve. This paper also presents the development and benchmarking of detailed 3D finite-element models for predicting the behavior and strength of noncompact and slender CFT members. The benchmarked models are then used to evaluate the fundamental P-M interaction behavior of CFT beam-columns, and the influence of material and geometric parameters such as the tube slenderness ratio , material strength ratio (Fy/fc′), member length-to-section depth ratio (L/D), and axial load ratio (P/Po). The parametric analyses indicate that for L/D ratios up to 20, the P-M interaction curves are governed by the relative strength ratio (csr=AsFy/Acfc′). The parametric analysis results are used to propose revisions to the current standard's interaction equations for designing noncompact and slender CFT beam-columns. © 2015 American Society of Civil Engineers.
Chen S.-Y.,Walter P Moore and Associates Inc. |
Xu H.,Texas Tech University |
Liu H.-C.,Texas Tech University
Jiaotong Yunshu Xitong Gongcheng Yu Xinxi/Journal of Transportation Systems Engineering and Information Technology | Year: 2013
Many signalized intersections in the United States are operating in oversaturated conditions during the morning and afternoon peak hours. Unlike under-saturated intersections, for which many well-established theories and signal timing policies have been developed, consensus has not been reached with regard to the control philosophy and timing strategy of oversaturated signals. For an isolated intersection, a common belief is that timely and efficient allocation of green time among the intersection approaches is essential to optimize traffic flows. A couple of the studies in the past have resulted in reasonable control policies that could possibly be implemented. However, the advantages and limitations of these strategies remain unrealized due to a lack of effective evaluation. This paper conducts an in-depth investigation to the characteristics and applicability of the control policies through thorough examination of two typical groups of classical models. The performance of the classic models is then compared with the latest versions of TRANSYT-7F and Synchro, upon which guidelines are made for effectively implementing signal control polices for oversaturated intersections. Copyright © 2011 by Science Press.
Henkhaus K.,Walter P. Moore and Associates Inc. |
Pujol S.,Purdue University |
Ramirez J.,Purdue University
Journal of Structural Engineering (United States) | Year: 2013
Results from tests on eight full-scale RC columns with ties with large spacing (s>d/2) and 90 hooks are presented. The test results showed that increasing the number of displacement cycles and applying displacements along more than one axis decreased the maximum drift ratio reached before the columns experienced failure in axial compression. Test columns had little drift capacity beyond shear failure. The mean difference between the maximum drift ratio at axial failure and the drift ratio at shear failure was less than 1%. © 2013 American Society of Civil Engineers.
Walter P. Moore and Associates Inc. | Date: 2011-06-03
Long-term facility maintenance may be more efficient when data from multiple sources are combined onto an easily navigable display. In particular, building model data from a three-dimensional computer assisted design (CAD) file may be combined with maintenance information from a computerized maintenance management system (CMMS) and other data sources such as users manuals and repair guides. The combined data may be accessible through a three-dimensional display of the building on a mobile device. The mobile device allows a user to navigate through the building and select components to view additional maintenance information for the selected components. The display may interact with location sensing devices, such as GPS, in the mobile device to automatically display model data near the users location. Additionally, a user may modify component information on the mobile device, which is transmitted to the CMMS to update the stored component information.