Civil & Environmental Engineering
Permanent URI for this communityhttp://hdl.handle.net/1903/2221
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Item ANALYZING BID PRICES QUANTITATIVELY AND PROTEST DECISIONS QUALITATIVELY TO REDUCE PROJECT-RELATED DISPUTES IN ADVANCE(2022) Kim, Young Joo; Skibniewski, Miroslaw J; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Parties to a construction contract can consume significant resources in dealing with project-related disputes. Therefore, it is advantageous for project stakeholders to identify potential issues earlier to avoid such problems as much as possible. This dissertation research explored evidence-based approaches to reduce project-related disputes before commencing construction projects. The research was carried out by examining a cost dataset from a state Department of Transportation that prioritizes the lowest-priced bid and by investigating a bid protest dataset from a Federal Government office that typically prioritizes the best value. With the coefficient of variation of bids as an independent variable of interest, the cost dataset was quantitatively studied using Welch’s t-test, correlation and regression analyses, and the K-nearest neighbors classification. Then, the Government Accountability Office’s decisions on denied bid protests against the U.S. Army Corps of Engineers were qualitatively meta-summarized. The observations showed the limited usefulness of collective intelligence provided by bidders at the time of bid opening in identifying projects likely to experience more significant project cost changes upon completion, as well as the effectiveness of the thematic findings in limitedly helping small businesses fore-test the validity of their cases before filing bid protests. The results could be applied beyond the Architecture, Engineering, and Construction industries as projects occur in all industries and industry sectors.Item ANALYTICAL STUDY OF THE BEHAVIOR OF COMPOSITE DOVETAIL METAL DECKING FLOOR SYSTEMS FOR THE DEVELOPMENT OF PRACTICAL DESIGN GUIDELINES(2022) Pase, Tara; Phillips, Brian M; Fu, Chung C; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Prior testing and industry practice have shown composite metal floor systems – floors systems constructed from concrete composite with metal decking – behave stiffer than the current state-of-the-practice simplified calculations and estimations predict. Specifically, the dovetail decking does not have the quantity of available research and universal design guidance compared to the more common trapezoidal composite decking; this lack of a more accurate design standard has made the calculation of the non-linear stiffness behavior of the dovetail composite deck floor systems under small to intermediate strains inaccurate, and therefore limits its use for long-span configurations where deflection limits (i.e., serviceability limits) control the design.The objective of this research is to create an analytical model of the flexural behavior of re-entrant dovetail composite decking floor systems for service (i.e., deflection) and strength (i.e., ultimate capacity) limit states and to understand the unique mechanical behavior of the slab system. By creating a more accurate analytical model of the flexural behavior of the dovetail composite deck system, a robust design guide table for engineering use is developed for a multitude of variables typically seen in construction, including but not limited to: various loads, deck gauges (thicknesses), concrete strength, concrete depths, etc. The flexural behavior of the composite metal deck is modeled based on its material properties and the following base assumptions: the composite slab is in pure bending; plane sections remain plane and are orthogonal to the neutral axis; the laws of static equilibrium apply; and loads are assumed to be static. Application of this composite theory to determine the moment-curvature relationship using a numerical strain-compatibility computer-based solver is compared against physical tests to validate and calibrate the theoretical assumptions that make up the basis for the calculations. The resulting flexural behavior derived from this numerical strain-compatibility method has a multitude of uses including but not limited to: the derivation of a robust design table for a number of decking gauges, common slab thickness values, concrete strength ranges, and so forth; and variable stiffness properties for use in simplified finite element plate models. The real-world purpose for this new numerical strain-compatibility model is to provide robust design guidance and engineering resources for practicing structural engineers, without a time-consuming and expensive finite element model. With the numerical strain-compatibility analysis, an engineer can accurately analyze and specify composite concrete slabs in building projects without being limited by shorter spans or thicker slabs due to inaccuracies in deflection calculations.Item PROBABILISTIC ASSESSMENT OF MULTI-MECHANISM FLOOD HAZARDS USING A BAYESIAN APPROACH(2022) Mohammadi, Somayeh; Bensi, Michelle; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Multi-mechanism floods (MMFs) are flood events caused by the simultaneous occurrence of multiple flood mechanisms such as storm surge, precipitation, waves, and tides. The term compound floods, which is a broader term frequently used in the current literature, includes MMFs as a subset. MMF events can have more severe impacts on communities and the built environment than single-mechanism floods. Therefore, a realistic probabilistic assessment of the frequency and severity of flood hazards requires the inclusion of the hazard contribution of MMFs. This dissertation addresses four objectives related to the probabilistic evaluation of MMFs. First, this dissertation develops a lexicon and framework for discussing a broad range of MMFs and then defines the gaps and shortcomings of the current literature. Second, this dissertation develops a Bayesian approach (BA) for performing a probabilistic assessment of a specific type of MMF hazard, namely tropical cyclone-induced increase in river discharge arising from multiple flood mechanisms. The Bayesian model is built using a Bayesian Network (BN). Five computationally justifiable predictive "placeholder" models are developed in this approach to estimate conditional probability tables in the BN. Third, the performance of the BN is assessed for "reasonableness" using three historical storms that affected the study area. Fourth, the capability of the BN for information updating is demonstrated by setting information related to historical observations as evidence in the developed BN and conducting forward and backward inferences. Finally, this study concludes with a summary and synthesis of the gaps and weaknesses of current literature and practices in addressing compound flood hazards. This study further highlights the capabilities and challenges of the developed Bayesian approach and outlines proposed next steps to address these challenges.Item VIBRATIONS OF MULTIPLE INTERCONNECTED BEAMS BY DIRAC-LAPLACE-HEAVISIDE METHOD(2021) Zhao, Xingzhuang; Chang, Peter; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The Multiple Inter-Connected Beams (MICB) system is widely used in civil and mechanical engineering. Adopting Euler-Bernoulli beam theory, this thesis presents novel exact and closed-form solutions for free and forced vibrations of the MICB system with intermediate connections and masses using a continuum approach. Recently, Roncevic et al. (2019) adopted Green's function method to study the free vibrations of a beam system with arbitrary intermediate supports. A total of 49 cases of Green's functions were derived and tabulated for each combination of the boundary conditions, i.e., fixed, pinned, sliding, free, translational spring-supported, rotational spring-supported, and combined translational-rotational spring-supported. Han et al. (2021) adopted the dynamic stiffness matrix method to study the free vibrations of a double-beam system with intermediate supports. With this method, one must discretize the beams at the connections and then apply the continuity conditions. This thesis is intended to treat MICB with arbitrary boundary conditions in a unified manner and avoid the need to discretize the beams. In this work, the Dirac-Laplace-Heaviside (DLH) method is proposed to investigate vibrations of the MICB with arbitrary intermediate connections and concentrated masses under the arbitrary boundary conditions subjected to arbitrary external excitation. The Dirac's delta function is adopted to formulate the mathematical model; the Laplace transform is utilized to solve the model; and the Heaviside function is used to implement the solution. Euler-Bernoulli beam is assumed to have a uniform cross-section. Axial loads, arbitrary external exciting forces, and arbitrary boundary conditions are also incorporated in the studied model. The exact mode shape solutions are developed by the proposed DLH method. The arbitrary boundary conditions are handled in a unified form. The solutions are validated by numerical results using a Finite Element Method (FEM). They are also compared to the results of specific cases and Green's function method. This study contributes to a continuum approach to handle beams with interconnections and concentrated masses. It is a general model that could be reduced to the specific models investigated in the literature. The method and model reported in this thesis may be useful for vibration analysis, dynamic control, vibration attenuation, design optimization of the MICB.Item Social media crowdsourcing for rapid damage assessment following sudden-onset earthquakes(2021) Li, Lingyao; Baecher, Gregory; Bensi, Michelle; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Rapid appraisal of damages related to hazard events is important to first responders, government agencies, insurance industries, and other private and public organizations. While satellite monitoring, ground-based sensor systems, inspections, and other technologies provide data to inform post-disaster response, crowdsourcing through social media is an additional and novel data source. In this study, the use of social media data, principally Twitter postings, is investigated to make approximate but rapid early assessments of damages following earthquake disasters. The goal is to explore the potential utility of using social media data for rapid damage assessment after sudden-onset hazard events and to identify insights related to potential challenges. This study defines a text-based damage assessment scale for earthquake damages and then develops a text classification model for rapid damage assessment. The 2019 Ridgecrest, California earthquake sequence is mainly investigated as the case study. Results reveal that Twitter users rapidly responded to this sudden-onset event, and the damage estimation shows temporal and spatial characteristics. The generalization ability of the model is validated through the investigation of damage assessment for another five earthquake events. Although the accuracy remains a challenge compared to ground-based instrumental readings and inspections, the proposed damage assessment model features rapidity with large amounts of data at spatial densities that exceed those of conventional sensor networks.Item IMPACTS OF FREE NITROUS ACID (FNA) ON STABLIZING FOOD WASTE (FW) AND SEWAGE SLUDGE (SS) FOR ANAEROBIC CO-DIGESTION(2021) Liu, Ruizhe; Li, Guangbin GL; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Anaerobic digestion (AD) is a sustainable waste-to-energy method for converting organic wastes to methane. In this work, a pretreatment of food waste (FW) with free nitrous acid (FNA) was proposed, and various pretreatment times (4 hrs, 72 hrs, and 28 days) and FNA concentrations (1.07, 2.13, and 5 mg FNA-N/L) were tested to evaluate its effectiveness in stabilizing FW and sewage sludge (SS). Soluble chemical oxygen demand (sCOD), soluble protein (sP), and soluble polysaccharide (sPS) in the groups with 50%:50% (w/w VS) pretreated at 5 mg FNA-N/L for 72 hrs were significantly increased by 631, 530, and 780 %, respectively, compared with the control group without FNA addition. Additionally, less sulfide was detected in the groups with FNA addition, indicating an effective reduction in sulfide-odor during the storage/pretreatment of FW and SS. The potential of biogas production of FNA-pretreated FW was assessed using biochemical methane potential (BMP) test, and the results showed that the groups with FNA pretreatment produced up to 91.97% more methane than the group without FNA. The results from this work indicated an improved digestibility of FW and/or SS for AD using FNA pretreatment, and suggested the optimal pretreatment condition at 2 mg FNA-N/L for 24 hrs for FW and FW/SS.Item Effects of Mineral Composition on Dynamic Properties of Dry Sands(2020) Rodriguez, Ricardo; Aggour, Mohammed S; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The effects of mineral composition on the dynamic properties of dry sands, mainly the shear modulus and damping, are not well determined. Due to the vast geologic diversity, knowledge of the effects of mineral composition on dynamic properties can be very beneficial since it can have a direct effect on the site’s seismic response analysis. To understand these effects, a series of dynamic tests using a Drnevich Resonant Column device were performed on various sand samples with different mineral compositions. Sands were selected and classified based on their respective ranking in the Mohs scale of hardness. All sand samples were engineered to have the same gradation properties. Resonant column tests were performed at various confining pressures in order to assess each sand’s shear modulus and damping ratio as a function of strain. Tests results show that the mineral composition has a large effect on both the shear modulus and damping. It was concluded that testing soils during the site characterization process should be emphasized.Item RELATING RISKS TO PAY FACTORS FOR HIGHWAY PAVEMENTS THROUGH MONTE CARLO SIMULATION(2019) Zhao, Yunpeng; Goulias, Dimitrios G; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The majority of State Highway Agencies (SHAs) now employ statistical-based specifications for the acceptance of highway materials and pavement construction. The parameters of these statistical acceptance plans are specified based on engineering judgment and may result in a high level of risk to both agency and contractor. In order to appropriately apply such specifications to the pavement construction industry, the associated production quality (i.e., materials and construction variability) needs to be well understood by all parties involved and its potential impacts require to be assessed. To address this objective of this study was to: (i) quantify the risks to the agencies and contractors (i.e., Type I and Type II errors); (ii) examine how the key components in a statistical acceptance plan impact its performance; and, (iii) identify a methodology to balance the risks and pay factors. Risk and pay factor analysis were conducted for both single and multiple quality characteristics through Monte Carlo simulation, and the development of Operating Characteristic, OC, curves. Furthermore, case studies were presented to demonstrate the value of the analyses proposed in this study. The methodology and findings identified in the study can be applied elsewhere to evaluate the acceptance plans and the associated risks pertinent to pavement construction and the production of highway materials.Item Modulus Based Compaction Quality Assurance for Unbound Materials Using Lightweight Deflectometer(2019) Afsharikia, Zahra; Schwartz, Charles W; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Moving away from traditional density-based methods of compaction quality assurance (QA) towards modulus-based procedures using Light Weight Deflectometer (LWD) require developing practical framework to: (1) determine soil- specific LWD target modulus, and (2) evaluate LWD modulus in the field effectively. This dissertation draws upon work from two research studies, TPF-5(285) pooled fund study and pilot projects conducted by Maryland State Highway Administration to refine the two proposed QA specifications for road base, subgrade, and embankment construction. The practical method of establishing the target modulus based on LWD drops on compacted Proctor molds was proposed and evaluated. Three types of LWDs (Zorn ZFG3000, Olson LWD-01, Dynatest 3031) were utilized and their field to target modulus ratio was compared to the percent compaction as a criterion for goodness of compaction. Results confirmed the validity of procedures for the variety of geomaterials tested and suitability for practical implementation by field inspection personnel. Target modulus values, calibrated acceptance criteria, sampling method, and frequency is presented for future implementation in the state of Maryland and other state DOTs. The LWD manufacturers collaborated to facilitate the implementation by instrument design and improvement or software/application development.Item INFLUENCE OF USING BONDING AGENT AND SHEAR STUDS ON BOND STRENGTH OF CONCRETE OVERLAYS ON PRESTRESSED SLABS(2018) Sharma, Shubham; Amde, Amde M.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This study explores the effects of using bonding agent and shear studs in conjunction with a defined surface roughness condition on the bond strength of concrete overlays poured over prestressed concrete slabs. The shear bond and tensile bond strengths are tested for seven cases by using Double-L test and Split-Prism test respectively. The test variables are surface roughness, use of slurry mix, commercial bonding agent and shear studs at the interface. Application of grooves on the substrate provides a good bond owing to an interlocking effect. Application of bonding agent results in the lowest bond strengths by introduction of a plane of weakness. The bond strength values where shear studs are used are the highest of all test cases. Based on the findings from this study, a recommendation is made to Maryland Department of Transportation to use precast panels with pre-existing grooves and simply pour the overlay concrete on top.