Civil Engineering

Civil Engineering

 

 

Poster Number: CE-01

Authors: Ankit Agrawal, Venkatesh Kodur

Title:  Factors Governing Residual Response of Fire Damaged Reinforced Concrete Beams

 

Abstract: Reinforced concrete (RC) structural members when exposed to fire, experience loss of strength and stiffness as a result of temperature rise in reinforcing steel and concrete. Thus, it is imperative to ascertain the residual capacity of fire damaged structural members through rational engineering methods for facilitating re-occupancy or to develop subsequent retrofitting measures. The extent of residual capacity in a fire exposed RC member is dependent on a number of factors including fire severity, peak rebar and concrete temperatures, level of loading (load ratio), restraint conditions and cross-sectional dimensions. Although earlier studies indicated these factors to be critical, the extent of influence of these parameters is not studied in literature. In this study, a finite element based numerical model is developed in ABAQUS to evaluate residual response of fire damaged RC beams. The influence of fire severity, load level, restraint conditions and sectional dimensions on residual capacity of fire exposed RC beams is studied. Results from the parametric study indicate that fire severity, cross-sectional size and load level have significant influence on both post-fire residual capacity, and residual deformations in the beam. Presence of axial restraint however, has only moderate influence on the post-fire response of RC beams. Moreover, under most real life fire scenarios, RC beams can retain up to 70% of their room temperature capacity provided tensile rebar temperature does not exceed 450°C.

 

This work was supported in part by United States Agency for International Development (through Pakistan-US Science and Technology Cooperative Program grant PGA-2000003665); Michigan State University

 

 

 

Poster Number: CE-02

Authors: Areej Almalkawi, Sameer Hamadna, Parviz Soroushian

Title:  Use of Aerated Cement Slurry for Infiltration in Ferro-cement Application: Mechanical and Thermal Investigations

 

Abstract: The bulk of the building weight resides in the binder, and lowering its density would help reduce the gravity and seismic. The cementitious binder used in development of the indigenous building systems is a slurry capable of infiltrating multiple layers of chicken mesh. Reduction of density of slurry has been accomplished via aeration using a vegetable-based foaming agent (saponin; this slurry produced a satisfactory balance of compressive strength and interaction with the chicken mesh reinforcement. After design and construction of example structural components with this aerated slurry, it was concluded that further weight savings are required for simplifying and expediting the construction process. Steps were thus taken to tailor the aeration conditions for lowering the density of the slurry to 1.3, 1.17 and finally 0.9 gr/cm3. At each step, the compressive strength was evaluated prior to further reduction of density. The data available at this point suggest that, considering the constraints imposed by the need for reliance on locally available labor and facilities, further reduction of density below 0.9 gr/cm3 would be challenging. The aerated slurries with reduced density were characterized for assessment of their strength, sorptivity, thermal conductivity and microstructural characteristics. Preliminary efforts were also initiated to develop nondestructive test methods for evaluating the quality of the low-density aerated slurries

 

 

 

Poster Number: CE-03

Authors: Saleh Alogla, Venkatesh Kodur

Title:  Transient Creep Strain of Concrete at High Temperature Measurements

 

Abstract: Concrete possesses good fire resistant properties due to its low thermal conductivity, high heat capacity, and slow degradation of its mechanical properties with temperature. However, concrete structures undergo significant deformations under fire exposure relative to that under ambient conditions. These deformations result from four strain components namely; mechanical, thermal, creep, and transient. The latter two strain components are typically combined as transient creep strain due to the complexity of separating them. This transient creep strain represents the additional strain, besides mechanical and thermal, which is observed under simultaneous loading and transient heating conditions. To quantify transient creep strain of different concrete types, four concrete mixtures were prepared, and cylindrical specimens were casted to be tested under transient heating conditions. The unique testing equipment was specifically designed for this purpose and comprised of an electrical furnace, hydraulic loading system, and deformation measuring apparatus. Concrete specimen is first loaded in compression to a specific stress level, and then heated, while under constant load, at a pre-selected rate of heating. Results from these experiments include change in axial displacement of the concrete specimen with time. Transient creep strain can be then quantified by deducing other strain components from total strain of the specimen. The findings clearly indicate that most of concrete total strain at high levels of stress and temperature is composed of transient creep. At stress level of 50% and higher, and at temperatures exceeding 500ᵒ, transient creep strain amount to most of concrete total strain and governs failure of concrete specimens.

 

 

 

Poster Number: CE-04

Authors: Mansour Alturki, Rigoberto Burgueño

Title:  Self-centering Reinforced Concrete Bridge Pier-wall System with Elastic Instability Devices

 

Abstract: Conventional reinforced concrete (RC) bridge pier-walls designed to resist seismic loads rely on dissipating seismic induced forces by undergoing permanent inelastic deformations. These pier-walls satisfy safety requirements, but usually suffer unrepairable damage after strong earthquakes. This damage could be eliminated, or highly reduced, by using a self-centering (SC) system. In this system, high seismic demands (damage) locations in pier-walls are replaced with SC devices. This study focuses on SC devices that depend on recoverable elastic instabilities of multiple interconnected cosine-curved domes (CCD) to absorb the seismic demands. Experimental and numerical studies are being carried out to develop and optimize the SC system. Experimental tests are being conducted on 3D printed SC device prototypes to examine: 1) the local behavior of individual and multiple interconnected CCD under load, and 2) the global system behavior of the SC pier-wall. The experimental investigation is associated with finite elements analysis to optimize the geometrical and material properties of the SC device. Primary results show that individual CCD units offer large post-buckling elastic recoverable deformation capacity. The SC device has bilinear response with relatively high initial stiffness and large post-buckling deformations. The device is also capable of recovering its original shape upon load removal. The SC system could be an economic alternative to conventional RC pier-walls where yielding components, or locations with localized plastic damage, are replaced with SC devices that absorb seismic demands through elastic instabilities.

 

 

 

Poster Number: CE-05

Authors: Ata Babazadeh, Rigoberto Burgueño

Title:  Proposed Guidelines to Consider Nonlinear Second-order Moments in Seismic Design of Slender Reinforced Concrete Bridge Columns

 

Abstract: Previous research on reinforced concrete (RC) columns demonstrated that second-order effects, i.e., nonlinear moment profiles and P-delta moments increase the length of the plastic region in proportion to the columns’ slenderness. In this research, a parametric study, which was conducted to determine the magnitude of the slenderness effects on the nonlinear response of RC columns, is presented. The effects of different design parameters such as geometrical, structural, and material properties on the susceptibility of RC bridge columns to second-order effects were investigated. A large set of all the design configurations that are permissible according to the latest seismic design guidelines for bridge columns was considered. It was found that longitudinal steel reinforcement, axial load, and aspect ratio dominate the extent of second-order effects on RC columns. Moreover, this study led to the identification of proper limits for the aforementioned parameters beyond which the nonlinear second-order moments are significant and can no longer be ignored. Recommendations are made based on the presented findings to update the current design guidelines for consideration of second-order effects. Finally, simple expressions are proposed to predict the effects of second-order P-delta moments on the length of the plastic region using common design parameters.

 

This work was supported in part by U.S. National Science Foundation grants CMMI-1000549 and CMMI-1000797

 

 


 

Poster Number: CE-06

Authors: Danilo Balzarini, Imen Zaabar, Karim Chatti

Title:  Impact of Concrete Pavement Structural Response on Rolling Resistance and Vehicle Fuel Economy

 

Abstract: Reduction in vehicle fuel consumption is one of the main benefits considered in technical and economic evaluations of road improvements. The present paper investigates the increase in vehicle energy consumption caused by the structural response of a concrete pavement to a moving load. The pavement structural response under moving load is determined for three sections under different wheel loading conditions (Passenger car, SUV, and Articulated truck), vehicle speed and temperature using a finite element model (DYNASLAB). As the rolling wheels move forward, the local deflection basin caused by the delayed deformation of the subgrade and the rotation of the slab forms a positive slope. The energy dissipated is calculated as the energy required for a rolling wheel to move uphill. Finally, the energy is converted into fuel consumption excess using the calorific value of gasoline and diesel. The maximum deflection-induced energy consumption is about 0.08% of the total consumption for articulated trucks, which is very small compared to 1.9% for asphalt pavements at high temperatures and low speeds, as reported by other studies.

 

This work was supported in part by California Department of Transportation

 

 

 

Poster Number: CE-07

Authors: Srishti Banerji, Venkatesh Kodur

Title:  Effect of Age on Temperature Dependent Thermal Properties of Concrete

 

Abstract: The thermal properties of concrete are critical for evaluating the fire resistance of concrete structures. These properties include thermal conductivity, specific heat, thermal diffusivity, mass loss and they vary with the age of concrete. Hitherto studies to assess concrete thermal properties have been conducted on concrete specimens after full curing (28 days) or long time after casting (much beyond 28 days). However, there is no reported data on the effect of aging on the evolution of thermal properties of concrete. Most properties of concrete including thermal properties change significantly with age, specifically in the first few weeks of casting. Hence, early age variation in thermal properties of is crucial for capturing the rate of hydration and rapid change in its moisture content during this period. In order to characterize the evolution of the thermal properties of concrete with age, experimental studies were conducted on normal strength concrete specimens. Thermal properties of concrete were evaluated at 3, 7, 14, 28 and 90 days after casting of concrete with the means of sophisticated instruments. Data from the tests is utilized to establish the effect of age on the evolution of thermal properties of concrete. These age dependent properties can be highly useful for evaluating heat of hydration, early age cracking as well as fire resistance of other concrete structures.

 

 

 

Poster Number: CE-08

Authors: Meghna Chakraborty, Timothy J. Gates

Title:  Developing Safety Performance Functions for Rural Unpaved Roadway Segments in Michigan

 

Abstract: More than 59% of fatal crashes in Michigan in 2015 occurred in rural areas. Unpaved roads, including both gravel and unimproved surfaces, are a critical component of the transportation network in Michigan, accounting for over 57% (43,606 miles) of the total roadway rural collector and local mileage (FHWA). However, safety research related to unpaved roads in the United States is very limited. To address this knowledge gap, research to develop safety performance functions (SPFs) for rural unpaved roadway segments in the state of Michigan is currently underway. SPFs are regression models that are used to estimate the expected crash frequency for a specific site type as a function of various factors that include traffic volumes, along with factors related to the roadway environment and roadway geometry, including functional classification, driveway counts, roadway widths, roadway curvature, and other factors. These roadway data have been collected from a variety of sources for roadway segments located within more than 20 counties statewide and have been merged with traffic crash data from 2011 to 2015. The data is currently being prepared for further analysis, including developing of the SPFs for rural unpaved road segments.

 

 

 


 

Poster Number: CE-09

Authors: Suyog Chaudhari, Yadu Pokhrel

Title:  Modeling and Remote Sensing of Water Storage Change in Lake Urmia, Iran

 

Abstract: Lake Urmia, the second largest saline lake in the world, is on the verge of drying up completely and creating a massive environmental disaster in the region. Several studies have partly blamed the intensive irrigation activities and prolonged droughts as the reason for this current condition of Lake Urmia. This paper studies the Lake Urmia watershed using a number of remote sensing data sets like current and historical Landsat imagery and MODIS, etc. to quantify the change in agricultural areas and inland water bodies as a result of intensive irrigation in the period of 1980-2016 . Furthermore, the Total Water Storage (TWS) anomalies by GRACE and a global land surface model called HiGW-MAT are studied to get the TWS variations in the Lake Urmia region. HiGW-MAT simulates all the components of an energy balance and water balance including the human land-water relationship and groundwater pumping. An attempt to calculate the Total Agricultural Water Consumption from 1980-2016 in the Lake Urmia watershed will be made, using the methodology based on Penman-Monteith method stated in Yuan & Shen, 2013, provided we get the weather station data from the region. Initial results show that the lake has shrink by about 56% with a corresponding increase of 98% in agricultural cropland and 180% in urban areas. The TWS change in the Lake Urmia basin by GRACE is about -1.69 cm/year which is in agreement with the simulated trend from HiGW-MAT.

 

 

 

Poster Number: CE-10

Authors: Fatemeh Fakhrmoosavi, Xiang (Alex) Xu, Ali Zockaie, Hani S. Mahmassani

Title:  Travel Costs Estimation on Least Generalized Cost Paths for  Large-scale Networks with Multi-class Users

 

Abstract: The integrated ABM-DTA framework requires implementing one of the least generalized cost path finding algorithms at different levels. The least generalized cost path finding algorithm is the most time-consuming module in DTA, thus rerunning this algorithm at the ABM level, where just least generalized cost information is needed (not the actual path information), is not efficient. An alternative approach, which is commonly practiced in ABM models coupled with the static traffic assignment, is to output zone-to-zone travel cost skims when they are calculated during the traffic assignment problem. The stored data can be used in the destination and mode choice models. However, in the ABM-DTA integration framework storing the dynamic travel skims considering multi-class users is not efficient due to the large size of the data and memory requirement. This calls for an alternative heuristic approach that can estimate least generalized costs in the network to be used at the ABM level in destination and mode choice models. This study finds the distance, travel time, and monetary cost of the path with the least generalized cost function for a certain origin and destination pair at a specific departure time. The algorithm incorporates simulated trajectories of the vehicles at the DTA level to estimate these costs as a function of Euclidian distance between the origin and destination zones. Numerical results for two real-world networks suggest the applicability of the method in large-scale networks in addition to its lower computational burden including solution time and memory requirements relative to other alternative approaches.

 

 

 

Poster Number: CE-11

Authors: Brian Gammon, Timothy Gates

Title:  Safety Performance of Rural Two-lane Two-way Paved County Highway Segments in Michigan

 

Abstract: Safety Performance Functions (SPFs) are a widely used procedure utilized by transportation agencies and engineers to predict crash frequency along roadway segments or at intersections. SPFs are particularly useful for determining the effect of various characteristics pertaining to traffic volume and composition, roadway geometry, area type, and cross-sectional features on traffic crash occurrence. The Highway Safety Manual (HSM) suggests using SPFs as the analysis method in highway safety studies used to support traffic safety improvement programs. SPFs are highly dependent on geographic regions along with functional class. Over 59% of fatal crashes in Michigan in 2015 occurred in rural areas and more than 74% (89,444 miles) of paved roadways in Michigan are rural county routes (FHWA, MDOT). This project focuses on determining an accurate SPF model for non-trunkline two-lane, two-way paved highway segments based on 30 Michigan counties. The SPF variable inputs include, but are not limited to, Average Annual Daily Traffic (AADT), segment length, access driveway density, pavement travel way and shoulder width, pavement marking presence as well as additional factors such as curb or parking lane presence. Due to over dispersion of the variance, a negative binomial regression model is utilized as the functional form for the SPF. Crash Modification Factors (CMFs) and further model calibrations will be included to improve precision of the SPF.

 

This work was supported in part by Michigan Department of Transportation

Poster Number: CE-12

Authors: Iman Harsini, Parviz Soroushian

Title:  Nondestructive Monitoring of Alkali-Silica Reaction in Concrete Using Portable NMR

 

Abstract: This paper documents the application of nondestructive NMR techniques towards detection and characterization of progressive Alkali-Silica Reaction (ASR) in standard concrete specimens made with reactive aggregates exposed to accelerated ASR aging. Relaxation times and self-diffusion coefficient were measured using the nondestructive NMR test system for specimens (prior to and) after different aging periods to study the formation of ASR gel and microcracks in cement-paste matrix. The formation of ASR gel and the subsequent imbibing of water into the gel alter the water distribution and binding condition in concrete. An increased concentration of water in ASR gel where it can exist in a distinct binding (mobility) condition is expected. The swelling of ASR gel is accompanied by formation of microcracks where water could reside in bulk form, and can create new structural gradients with respect to depth. The nondestructive NMR test data were interpreted in light of these effects of ASR aging on concrete structure, and distinct trends in NMR test data that point at the presence and extend of ASR were identified. Corroborative nondestructive tests were also conducted in order to verify the trends identified in NMR tests. These nondestructive tests involved measurement of ultrasound pulse velocity (UPV), dynamic elastic modulus, petrographic analysis, dye treatment and weight and volume changes.

 

This work was supported in part by US DOT

 

 

 

Poster Number: CE-13

Authors: Bang He, Mingzhe Li, Sihao Gu, Weiyi Lu

Title:  Enhanced Buckling Behavior of Liquid Filled Cylindrical Tubes under Uniaxial Compression Load

 

Abstract: With the advance of the nano-porous material, liquid nanofoam (LN) filled structures (tube, micro-truss, etc.) have been developed in past couple years. The prominent energy absorption capability of these structures and their promising implementation in auto industry, civil engineering has drawn considerable attention. However, the mechanical behavior of these structures with the presence of the interaction of confined liquid and structure are still completely unfolded. This study aimed to investigate the behavior of liquid-filled structures under quasi-static compression loading through experimental observation and analytical work. Our study demonstrate that the existence of increased hydro-static pressure in cylindrical tubes under compression load leads to the following enhanced mechanical behavior comparing to empty tubes. (a) the collapse is successive and less sensitive to circumferential imperfection than empty tube, (b) the axisymmetric buckling of both liquid filled tubes shows a stable tendency in term of the buckling modes and reaction loads after initial collapse, (c) the load in axial direction is proportional to the tube shortening after initial collapse, (d) the tubes ends up with an uniformed bugling instead of collapse of localized wrinkles. As a result, the axial rigidity wasn’t reduced in the existence of the internal pressure. These findings shed light on the potential engineering applications of liquid filled structures where successive and stable collapse are desired, like the energy absorption device. From the analytical work, the understanding on shell behavior with increasing internal pressure is also extended.

 

This work was supported in part by Ford-MSU Alliance Program

 

 

Poster Number: CE-14

Authors: Derek Hibner, Venkatesh Kodur

Title:  Residual Capacity of Fire Exposed Reinforced Concrete Columns

 

Abstract: Reinforced concrete (RC) structural members exhibit high fire resistance due to relatively low thermal conductivity, high thermal capacity, and a slower degradation of mechanical properties of concrete with increasing temperature. Complete collapse of RC structures is rare, due to advancements made in active fire protection systems and efficient firefighting strategies. However, this fact does not ensure safety of a structure for immediate reoccupation after a fire is extinguished. Unlike fire induced spalling, which is a visible sign of fire damage, structural deterioration due to degradation of mechanical properties at elevated temperatures and redistribution of stresses within the member is not too apparent. Thus, it is imperative to ascertain the residual capacity of structural members through rational engineering methods. A combination of numerical and experimental studies was applied for developing an approach for assessing residual capacity of fire exposed RC columns. The effect of varying fire scenarios and thermal properties on the thermal profile experienced within an RC column was studied using a numerical model developed in ABAQUS. Results from the analysis show that much of the capacity of a fire exposed RC column will be retained, as long as the temperature of the fire does not exceed 800 ̊C. Further, a drastic reduction of capacity was observed in a fire exposed column when fire temperatures exceed 1000 ̊C.

Poster Number: CE-15

Authors: Ali Imani Azad, Roozbeh Dargazany

Title:  Multi-scale Study of Mechanical Behavior of CNT Fibers

 

Abstract: The interest in carbon nanotube (CNT) fibers have been highly increased due to their light weight, high strength, and high electrical conductivity. Still, the hierarchical structure of the helical and twisted fibers yields significant loss in translation of mechanical properties from individual CNTs to fiber. The sources of the loss has not been well understood. Studying the sources of energy loss and contribution of each sources could be helpful for maximizing the tensile strength and rigidity of these fibers. A CNT fiber made by braiding CNT strands. The strands are also formed by twisting CNT yarns, which are similarly formed by twisting the CNT ribbons around themselves. Those ribbons are thin plates of CNTs extracted from the forest of nanotubes. Thus, CNT fibers are the result of bending of twisted structures around each other. This makes the bending behavior of a twisted structures a vital key to study the tensile behavior of the final fiber product. Our study employs a multi-scale approach to describe the hierarchical structure of fibers and understand the sources of losses with respect to phenomena such as decrease in void area in a cross section of fiber, and the effect of plastic behavior of each strand in the fiber.

 

 

 

Poster Number: CE-16

Authors: Anthony Ingle, Timothy Gates

Title:  Rural Two-lane Two-way Highway Safety Performance

 

Abstract: This study involves the development of safety performance functions (SPFs) for two-lane two-way segments located along rural roadways under the jurisdiction of the state of Michigan. Extensive databases were developed that resulted in the integration of traffic crash information, traffic volumes, and roadway geometry information. After these data were assembled, an exploratory analysis of the data was conducted to identify general crash trends. This included assessment of the base models provided in the Highway Safety Manual (HSM), as well as a calibration exercise, which demonstrated the goodness-of-fit of the HSM models across various site characteristics. Michigan-specific SPFs were estimated, including simple models that consider only annual average daily traffic (AADT). More detailed models were also developed, which considered additional geometric factors, such as posted speed limits, number of lanes, and the presence of shoulder and rumble strips along the edge of the roadway. Crash modification factors (CMFs) were also estimated, which can be used to adjust the SPFs to account for differences related to these factors. Ultimately, the results of this study provide the Michigan Department of Transportation (MDOT) with a number of methodological tools that will allow for proactive safety planning activities, including network screening and identification of high-risk sites.

 

This work was supported in part by Michigan Department of Transportation

 

 

 

Poster Number: CE-17

Authors: Guoting Kang, Han Qiu, Shu-Guang Li, David Lusch, Mantha S. Phanikumar

Title:  Understanding High-resolution Spatiotemporal Dynamics of Groundwater Recharge Using a Physically Based Hydrologic Model: A Case Study in Ottawa County, Michigan

 

Abstract: Quantifying the natural rates of groundwater recharge and identifying the location and timing of major recharge events are essential for maintaining sustainable water yields and for understanding contaminant transport mechanisms in groundwater systems. Using Ottawa County, Michigan as a case study in sustainable water resources management, this research is part of a larger project that examines the issues of declining water tables and increasing chloride concentrations within the county. A process ­based hydrologic model (PAWS) is used to mechanistically evaluate the integrated hydrologic response of both the surface and subsurface systems to further compute daily fluxes due to evapotranspiration, surface runoff, recharge and groundwater­-stream interactions. The model is built based on three major watersheds at 300m spatial resolution and daily temporal resolution, covering all of Ottawa County and is calibrated using streamflow data from USGS gauging stations. In addition, synoptic and time­series baseflow data collected using Acoustic Doppler Current Profilers and electromagnetic flow meters during the summer of 2015 are used to test the ability of the model to simulate baseflows and to quantify the uncertainty. The MODIS evapotranspiration product is used to evaluate model performance in simulating ET. The primary objectives of this study are to (1) understand the periods and locations of high and low groundwater recharge in the county between the years 2011 and 2015; and (2) analyze the impacts of different types of land use, soil and elevation on groundwater recharge.

 

 

Poster Number: CE-18

Authors: Leila Khalili, Roozbeh Dargazany

Title:  A Micro-mechanical Model for Predicting Visco-elastic Behavior of Elastomeric Composites Based on Visco-elastic Response of Single Polymer Chain

 

Abstract: In this work a viscoelastic model is developed to simulate and predict the inelastic and time-dependent damage behavior of elastomeric composites. The concept here is that single polymer chain has a visco-elastic behavior which describes creep in one chain with respect to local matrix relaxation. The reason for considering time dependent behavior for single chain is that the stiffness of a polymer chain segment dissipates over time due to chain sliding or breakage of physical links. Linking polymer softening to the creep behavior observed in uniaxial tension of the composite, the damage mechanism in one polymer chain is derived with respect to the deformation history. Having the time-dependent behavior of single polymer chains, through a micro-macro-scale transition using micro-sphere concept, the viscous effects in rubber viscoelasticity can be described. Using the network evolution concept, the kinetic energy of rubber matrix is calculated in each direction. Accordingly damage history will be measured in each direction and extended to represent the viscous contribution of polymers in mechanics of the matrix. This proposed model includes a few number of physically motivated material constants and demonstrates good agreement with experimental data.

 

 

Poster Number: CE-19

Authors: Puneet Kumar, V.K.R. Kodur

Title:  Thermo-mechanical Behavior of Prestressed Concrete Hollow Core Slabs Exposed to Vehicle Fires

 

Abstract: Prestressed hollow core (HC) concrete slabs are widely utilized in parking structures due to their cost effectiveness, speedy construction, low maintenance costs, superior quality, optimized production, and inherent high fire resistance. While structural performance of HC slabs is investigated thoroughly, information related to fire performance of these slabs is rather sparse in the literature. Fire resistance of these slabs is mostly estimated through standard fire tests or prescriptive approaches, without any consideration to critical factors governing fire behavior under vehicle fire exposure in parking structures. In order to overcome current knowledge gaps, a set of numerical studies is undertaken using a generic 3D finite element model. The model, developed using ANSYS, is capable of capturing fire behavior of HC slabs for a wide range of variables such as: different fire scenarios, concrete strength, member dimensions, cover thickness, load level, and support restraints. This validated model is utilized to perform a series of parametric studies to identify critical factors affecting fire behavior of these structures under vehicle fire exposure in parking structures. Results from these parametric studies can be further utilized to propose a rational design approach, for performance based fire design of HC slabs.

 

This work was supported in part by Prestressed Concrete Institute (PCI)

 

 

Poster Number: CE-20

Authors: Yogesh Kumbargeri, Ugurcan Ozdemir, Derek Hibner, Michele Lanotte, M. Emin Kutay, Aksel Seitllari

Title:  An Acceptance Test Protocol for Chip Seal Projects using Image Analysis Techniques

 

Abstract: Chip seal is a popular preventive maintenance techniques implemented by many Departments of Transportation (DOTs) and other road agencies. Its performance depends on Percent Embedment (PE) of aggregates in the asphalt layer. Main objective of the research study was to develop a standard test protocol to directly calculate the PE via digital image analysis. Three image-based algorithms, namely (i) peak & valley method, (ii) surface coverage area method, and (iii) each aggregate method, were developed to analyze chip seal samples. Then, validated algorithms were used to analyze lab produced samples as well as cores from eight different road sections across Michigan. Chip seal samples produced in laboratory were used to investigate effect of binder and aggregate application rates on PE. It was concluded that PE was sensitive to binder application rates but not to aggregate. Core samples were used to compare the ED results from image-based algorithms against the results of sand patch and laser-scanning tests carried out in-situ. Among the image analysis algorithms, peak & valley method was found to show similar results as obtained from sand patch tests. Surface coverage area method was recommended as the most appropriate to analyze chip seal pavements as it omits the assumptions made in the other methods. The image-based algorithms were implemented in a user-friendly software package, named as CIPS, to analyze chip seal samples fundamentally and accurately. The test protocol, along with software can be easily used, distributed to various road agencies and contractors, aiding as a robust QA/QC tool for chip seal performance investigation.

 

This work was supported in part by Michigan Department of Transportation (MDOT); University Transportation Center for Highway Pavement Preservation (UTCHPP)

Poster Number: CE-21

Authors: Junfeng Li, Bang He, Weiyi Lu

Title:  Mechanical Response of Metallic Tube with Structural Defect Filled with Compressive Liquid

 

Abstract: Lightweight design is desired for various engineering applications including structural design of columns, machine tool components, etc. Hollow structures are one major type of lightweight designs. However, hollow structures are more sensitive to defects than their solid counterpart, due to damage localization introduced by their structural configurations and dimensions. In current study, we use a compressive liquid to fill metallic tubes with structural defects and hypothesize that the hybrid structure (1) is much less sensitive to defects, and (2) possesses higher specific buckling strength and energy absorption capacity. To test our hypotheses, we characterized the mechanical behavior of empty tubes, incompressible liquid filled tubes, and compressible liquid filled tubes with and without structural defects by uniaxial compressive tests. The size, shape and location of the defects on the testing specimens were precisely controlled. Our experimental results demonstrate that the liquid filled tubes have better load carrying capacity and defect tolerance. In addition, the compressible liquid filled tube has larger deformability and higher energy absorption capacity. With the improved mechanical properties, the liquid filled metallic tubes can be developed into lightweight, strong, and stable structural components for load carrying and energy dissipation. The enhanced defect resistance of liquid filled tubes can lower the manufacturing requirement, and thus reduce the total cost of structural components.

 

 

 

Poster Number: CE-22

Authors: Mingzhe Li, Bang He, Sihao Gu, Weiyi Lu

Title:  Enhanced Gravimetric and Volumetric Energy Absorption Efficiencies of Thin-walled Steel Tubes Filled with Liquid Nanofoam

 

Abstract: Thin-walled metal tubes have been widely used as energy absorbers to mitigate adverse effects of impact and protect structures and facilities. However, once the initial buckling stress of the tube is reached, the post-buckling plateau of the tube has a much reduced average stress which determines the energy absorption efficiency of the empty tube. As a result, the real energy absorption efficiency of the thin-walled tube is much lower than the theoretical limit which is proportional to the value of initial buckling stress. We hypothesize that by filling thin-walled tubes with the novel liquid nanofoam (LN), (i) the energy absorption efficiency of the hybrid structure can reach the theoretical limit, and (ii) the main working mechanism is the effect of solid-liquid interaction on tube buckling. To test these hypotheses, we have characterized the energy absorption efficiency of LN filled steel tubes by quasi-static compression tests and dynamic impacts. Under quasi-static compression, the gravimetric and volumetric energy absorption efficiencies of LN filled steel tubes are 25% and 118% higher than the values of empty tubes, respectively. This is due to the changed buckling mode and the promoted post-buckling stress of the hybrid structure by the highly compressible LN. In addition, under dynamic impact, both the gravimetric and volumetric energy absorption efficiencies of LN filled tubes are further increased by 16%. The strain rate dependent behavior of LN filled tubes must be attributed to the solid-liquid interaction between the LN and the steel tube wall. Our experimental results have demonstrated that the energy absorption efficiency of thin-walled tubes are significantly improved by the LN filler especially at higher strain rates. This hybrid structure has merit in guiding the design of light-weight and small scale cellular structures for vehicle safety and crashworthiness.

 

This work was supported in part by Ford-MSU Alliance Program

 

 

 

Poster Number: CE-23

Authors: Muhammad Munum Masud, Syed Waqar Haider

Title:  Incorporation of Pavement Preservation Treatments in Pavement- ME Analysis and Design

 

Abstract: Moisture in pavement subsurface layers has a major influence on Pavement performance. Variation in moisture content over time in subsurface layers predominantly in subgrade, is dependent on temperature, moisture, precipitation and surface conditions of pavements. Sources, which allow moisture change in unbound layers, include surface cracks, untreated shoulders, side ditches and longitudinal/transverse joints. Consequently, resilient modulus is adversely affected, which ultimately leads to premature failures in pavements and reduced life. Keeping in view the contribution of moisture damage in pavements, there is a dire need to relate the extent of discontinuities to the increase in moisture levels in unbound layers. In this study, an effort will be made to develop relationships between the amount of surface cracking (joints/cracks) and the infiltration rate of water into the subsurface layers in different climates using the SMP data, to study the effects on unbound layers’ resilient modulus. For this, Drainage Requirement in Pavements (DRIP) microcomputer program is used to evaluate and validate existing models available for analysis of moisture change in pavements. Existing models will be used to establish impact of moisture on unbound layers moduli and subsequently use the pavement ME to quantify performance requirements. This study will also emphasize on effect of pavement preservation treatment timings on pavement performance in the analysis and design process

 

 

Poster Number: CE-24

Authors: Gopikrishna Musunuru, Syed Waqar Haider

Title:  Comparisons of Traffic Patterns Overtime in Michigan for Mechanistic Empirical Pavement Design

 

Abstract: The 1993 AASHTO Design guide has been used for the design of pavements for several years. Although it has been an important tool in pavement design, it is severely limited in the sense that the guide is empirical and the overall traffic is represented by a single value called the equivalent single axle load (ESAL). Several studies have found that the ESAL is incapable of representing the complex failure modes of pavement structures. To address these limitations, AASHTOWare Pavement ME Design was developed by National Cooperative Highway Research Program (NCHRP). Pavement ME requires an extensive amount of traffic inputs for design/analysis of pavement systems; such as base year truck traffic volume, traffic volume adjustment factors, axle load distribution factors, and general traffic inputs. These traffic volume adjustment factors include monthly adjustment factors (MAF), vehicle class distribution (VCD), hourly distribution factors (HDF), and traffic growth factors. The general traffic input data includes number of axles per truck, axle configuration, and wheel base. Pavement ME required traffic data can be obtained through weigh-in-motion (WIM), automatic vehicle classification (AVC), and vehicle counts. Axle load distribution factors or spectra (ALS) can only be determined from WIM data. A study has been conducted in 2009 to develop these traffic inputs for MEPDG using the data collected from the WIM and classification sites between the years 2006 and 2007across the State of Michigan. The objective of this study is to develop the inputs using the data between 2011 and 2016 and compare the old and the new traffic patterns. Any change in patterns observed would severely affect the pavement design. The results of this study could be used by MDOT to incorporate into their pavement design process.

 

This work was supported in part by Michigan Department of Transportation

 

 

Poster Number: CE-25

Authors: M. Z. Naser, V. K. Kodur

Title:  An Approach for Evaluating Shear Capacity of Steel and Composite Beams Subjected to Fire Conditions

 

Abstract: Steel structures exhibit lower fire resistance due to high thermal conductivity, low specific heat and rapid degradation of strength and stiffness properties of steel. In fact, steel structural elements can rapidly lose much of their load carrying capacity within the first 20-25 minutes from exposure to fire conditions. As a result, steel structural members can be highly vulnerable to fire-induced damage leading to collapse of a structure. Therefore, behavior of steel and composite beams, under fire conditions, is of critical concern from fire safety point of view. In current design philosophy, fire design of these beams is carried out based on flexural limit state only. However, this design philosophy may not be conservative (or realistic) especially when shear forces in a beam are dominant or shear capacity degrades at a rapid pace under fire. Since current design provisions do not provide specific guidance on fire resistance of steel and composite beams subjected to combined shear and fire loading, this paper presents the development of an approach for evaluating shear capacity of steel and composite beams as a function of fire exposure. This proposed approach accounts for temperature-induced degradation of mechanical properties of concrete and steel, temperature-induced sectional instability and level of composite action offered by concrete slab in evaluating shear capacity in beams. The validity of the proposed approach will be established by comparing predicted response parameters against test data through numerical analyses.

 

This work was supported in part by National Science Foundation under Grant number CMMI-1068621

 

 

Poster Number: CE-26

Authors: Tula Ngasala, Phanikumar Mantha, Susan Masten

Title:  Using Groundwater Modeling System (GMS) to Estimate the Contamination Load of Domestic Wells from Septic Systems in Tanzania

 

Abstract: Groundwater is one of the main sources of water in many urban low-income areas of Dar-es-Salaam, Tanzania. People rely on domestic wells for their daily water supply. The on-going study was done in one of the urban communities of Dar-es-Salaam city. In this area, many domestic wells are located approximately 5 meters to 12 meters away from septic tanks or pit latrines (WHO standard is 60 meters). At least one latrine or septic tank was found at each household and there was a domestic well after every five to ten households. Groundwater Modeling System (GMS) will be used to develop a conceptual model based on data from nearly 65 boreholes. The model will use a steady state calibration and transmissivity data to simulate nitrate, total dissolved solids and E. coli load from septic systems to groundwater as well as global sensitivity analysis. The main goal is to conduct groundwater modeling to analyze the performance of existing wastewater collection systems and the negative impact to groundwater. Specific objectives are to estimate the load (mass rate) of contaminants, distance, velocity and time that contaminant plumes will take to reach the nearby domestic wells. Soil, aquifer and domestic wells properties were collected from the study area as input parameters for calibration and simulation purposes. Results are expected to show the significant contamination level of domestic wells in terms of distance, velocities and time. An estimated level of contamination will help with the future implementation of new technologies to minimize groundwater contamination.

 

 

 

Poster Number: CE-27

Authors: Rajendra Prasath Palanisamy, Yiming Deng, Mahmoodul Haq, Sung-Han Sim

Title:  Virtual Sensing for Structural Health Monitoring of Offshore Structures

 

Abstract: Offshore structures are generally subjected to harsh environment with strong tidal current and wind loading, which demands robust and reliable Structural Health Monitoring (SHM) to avoid any catastrophic failure. The growing size, complexity, and harsh environment of offshore structures lead to difficulties in sensor deployment and maintenance. Response at critical locations in complex offshore rigs are inaccessible during sensor deployment. Moreover, their operational environment demands frequent sensor maintenance for uninterrupted monitoring. Virtual sensing addresses these issues by estimating unmeasured responses with the help of measured responses. This dissertation delineates a virtual sensing method based on Kalman state estimator to combine multi-sensor data under non-stationary random excitation. The estimation algorithm effectively uses the FE model of a structure to predict and fuse different type of structural response (acceleration and strain). The performance of virtual sensing is successfully verified with numerical and experimental test over a bottom fixed off-shore structure. Test results conclude that the unmeasured responses are reasonably recovered form measured responses.

 

 

 

Poster Number: CE-28

Authors: Shabnam Rajaei, Karim Chatti, Roozbeh Dargazany

Title:  Tire-pavement Interaction in Micro-scale: Hysteresis Contribution

 

Abstract: Understanding the interaction between tire and pavement surface is of great importance since it can improve the perception of friction and rolling resistance. Friction plays an important role in vehicle safety while rolling resistance can affect fuel consumption of the vehicle. Several factors influence these two phenomena. In this study, the effect of pavement surface characteristics on friction and rolling resistance is investigated at the microscale level. Focusing on the effect of pavement surface micro-texture on tread rubber energy loss, a finite element model is generated using commercial software ABAQUS. The pavement surface is considered as simple sinus waves. The energy loss due to predefined surfaces is calculated. A UMAT subroutine code has also been prepared for characterizing the rubber material properties as hyper-viscoelastic material. The results of the model are validated by Persson’s theory of rubber friction.

 

This work was supported in part by Center for Highway Pavement Preservation (CHPP)

 

 

 

Poster Number: CE-29

Authors: João Rodrigues, Venkatesh Kodur, Mohannad Naser

Title:  Effect of Shear on the Fire Response of Steel and Composite Steel and Concrete Beams

 

Abstract: Structural elements in case of fire experience loss of load bearing capacity and stiffness due to degradation of strength and modulus properties of constituent materials. Current provisions on design of structural elements takes into account the temperature induced actions but in general shear effects is quite always not taken into account. However shear can be important on high slender beams, such as the case of bridge girders, beams with reduced cross sectional area and beams with short-span. In these beams shear effects can be more predominant than flexural effects because shear capacity can degrade at a more rapid pace than flexural capacity due to possible temperature induced local buckling of the web. The design codes consider shear design as a minor problem. The Eurocodes, for example, examines the shear capacity of cross-section as for normal temperature, but affecting the resistance by the yield strength reduction coefficient of the steel for the temperature of the web. Research on the effects of shear on beams is still scarce. However the available research have shown that shear can be a problem especially in high slender beams. As part of current research the problem inherent to the effects of shear on failure of steel and composite beams under fire is studied. Based on results from numerical studies, methodologies are proposed for shear design under fire exposure. Further possibilities to overcome shear effects such as using corrugated or trapezoidal web beams is discussed.

 

 

 

Poster Number: CE-30

Authors: Ramin Saedi, Mohammadreza Saeedmanesh, Ali Zockaie, Meead Saberi, Nikolas Geroliminis, Hani S. Mahmassani

Title:  Network-wide Fundamental Diagram (NFD) and Travel Time Reliability Relations for a Heterogeneous Network and its Density-based Clusters

 

Abstract: The primary objective of this paper is to elaborate homogeneous well-defined Network-wide Fundamental Diagrams (NFD) after clustering a heterogeneous network, in order to alleviate the variance of congestion within each cluster. Partitioning is based on the spatial properties of congestion in the course of a specific time span. In this paper we intend to represent the travel time reliability models both for the heterogeneous network and its partitioned homogeneous subnetworks. The proposed model for reliability of travel time and extracting NFD in subnetwork level are calibrated for realistic large-scale network of Chicago when effectively serve the morning and evening peak demands. This study establishes important results in describing two main features of the transportation network: (i) network-level and subnetwork-level relationships between main traffic flow components and (ii) overall reliability of travel time as a performance descriptor for network and its clusters. These results could allow the application of methodological strategies to organize the real-time hierarchical perimeter traffic control configuration to reduce the network overall congestion. Employing NFD in transportation planning stipulates the implementation of a new generation of traffic control scheme and enhance the mobility. Formulation of travel time reliability takes advantage of estimation of the level of service from users’ perspective. Characterizing the NFDs and variability of travel time can be utilized to develop the routing strategies and urban planning activities.

 

 

 

Poster Number: CE-31

Authors: Hadi Salehi, Saptarshi Das, Shantanu Chakrabartty, Subir Biswas, Rigoberto Burgueño

Title:  An Image-based Machine Learning Paradigm for Health Monitoring of Aerospace Structure through a Self-powered Sensing Concept

 

Abstract: This study proposes an intelligent strategy for damage identification in aerospace structures. The strategy was evaluated based on the simulation of the binary data generated from self-powered wireless sensors along with a pulse switching architecture. A system employing such an energy-efficient technology requires dealing with power budgets for sensing and communication of binary data that leads to time delay constraints. This paper develops an innovative image-based machine learning paradigm using pattern recognition (PR) for health monitoring of aerospace structures. Time-delayed binary data extracted from self-powered sensors was utilized to determine damage indicator variables. The performance and accuracy of the damage detection strategy was examined and tested for the case of an aircraft stabilizer. Damage states were simulated on a finite element model by reducing stiffness in a region of the stabilizer’s skin. Results indicate that the proposed damage detection strategy show satisfactory performance to identify damage in spite of high noise levels. It is observed that PR can be applied as a promising machine learning paradigm for damage detection using novel self-powered wireless sensors with time-delayed binary data.

 

 

 

Poster Number: CE-32

Authors: Mahmood Sarwar, Venkatesh Kodur

Title:  Characterizing Compressive Strength and Explosive Spalling Behavior of Ultra High Performance Concrete (UHPC) at Elevated Temperatures

 

Abstract: Concrete is one of the most widely used materials in construction applications. Newer types of concrete are being developed to improve the performance and durability properties and explore environmentally friendly considerations. One recent development in concrete technology is ultra high performance concrete (UHPC). UHPC offers excellent material properties including strength, durability, ductility, and sustainability, and thus finding wide ranging application in infrastructure. When used in building applications, UHPC structural members must satisfy fire resistance requirements as specified in building codes. For evaluating fire resistance, high temperature mechanical properties of UHPC is critical. Unfortunately, data pertaining to UHPC’s mechanical properties at elevated temperatures is quite limited. Preliminary studies indicate that UHPC, due to low permeability, experiences rapid strength degradation at elevated temperatures. In addition, UHPC can undergo significant spalling under fire conditions. These two factors can lead to significant loss of strength and stiffness properties in structural elements resulting in lower fire resistance, and sudden failure. To develop data on temperature induced strength degradation, and explosive spalling behavior of UHPC, an experimental study on UHPC specimens is carried out at Michigan State University. UHPC cylinders were fabricated from three different design mixes, namely two mixes of UHPC with varying content of steel fibers and one UHPC mix with steel and polypropylene fibers. The cylinders were tested in a hot state under compressive loads at various temperatures (20 – 700C). In the presentation, detailed results pertaining to explosive spalling, and the empirical relation showing the variation of compressive strength with temperature will be presented.

 

 

 

Poster Number: CE-33

Authors: Aksel Seitllari, Yogesh Kumbargeri, Michele Lanotte, M. Emin Kutay

Title:  Investigation of the Effect of Polymer and Rubber Modifications on Bubble Size Distribution of Foamed Binders using X-ray Microtomography Imaging

 

Abstract: Rapid implementation of foam-based Warm Mix Asphalt (WMA) technologies in the U.S. has significantly increased the need for understanding the behavior of foamed asphalt binders, especially the binders modified with polymers and other new additives. It is well known that foaming characteristics of binders are influenced by numerous factors including foaming technology, amount of water, temperature, binder grade and modification. The main objective of this study was to investigate the significance of neat (control), polymer (SBS) and partially devulcanized rubber (DVR) modified asphalt binder properties on foaming characteristics (e.g. bubble size distribution and surface area index). Internal morphology of bubbles in foamed asphalt binders were directly quantified using the nondestructive X-Ray Microtomography (XRM) imaging technique. The neat and modified binders were foamed at temperatures corresponding to the equi-viscous conditions. As soon as the binders were foamed, they were instantly frozen using liquid nitrogen to preserve the internal bubble morphology. Then the XRM system at the Michigan State University (MSU) was used to acquire the 3D internal images of the frozen foamed asphalt binders. Image processing techniques were employed to isolate the individual bubbles then their size, volume and shape characteristics were computed using image analysis methodologies. The results showed that polymer (PMB) and partially devulcanized rubber (DVR) modified binders significantly affected the foam characteristics and the morphology of the bubbles.

 

This work was supported in part by Michigan Department of Environmental Quality

 

 

 

Poster Number: CE-34

Authors: Sanghoon Shin, Yadu Pokhrel

Title:  High Resolution Modeling of Reservoir Storage and Extent Dynamics at Continental Scales

 

Abstract: Land surface models have been used to assess water resources sustainability under changing Earth environment and increasing human water needs. Overwhelming observational records indicate that human activities have ubiquitous and pertinent effects on the hydrologic cycle; however, they have been crudely represented in large scale land surface models. In this study, we enhance an integrated continental-scale land hydrology model named Leaf-Hydro-Flood to better represent reservoir storage dynamics. The model is implemented at high resolution (5km grids) over the continental US. Reservoir operation and river-flood routing schemes are newly implemented and irrigation and groundwater pumping are simulated altogether. The new schemes improve river flow simulations in highly regulated regions through better representation of dynamic reservoir extent, an important mechanism that remains largely ignored in continental to global scale hydrological modeling. The dynamic reservoir extent is expected to allow better modeling of hydrologic storage and fluxes related to land-water management. The improvements in this study have potential to build consistent modeling framework for human-water-climate interactions.

 

 

 

Poster Number: CE-35

Authors: Meead Saberi, Mehrnaz Ghamami, Yi Gu, MohammadHossein Shojaei, Elliot Fishman

Title:  Network Theoretic Investigation of the Influences of a Public Transit Disruption on Bike Sharing Use

 

Abstract: This paper employs a network theoretic analysis to realize the influences of a public transportation disruption on bike sharing usage in London. We initially compared statistical properties of the bike sharing use before, during, and after a disruption in London underground. Results showed that the disruption resulted in increase of both the number and duration of bike trips. Also, new origin-destination demand were generated and the bike sharing network became more connected during the disruption. The observed changes are not homogeneous over space, such that stations in central London encountered greater increase in bike trip counts com-pared to outer areas. The main contributions of the paper are presentation of a network-based approach to analyzing bike trips and providing in-sights on the interconnections between public transportation and bike sharing systems. Results suggest that bike sharing systems can potentially reduce the load on public transport network and increase the resilience of the transportation system in times of disruptive events.

 

 

 

Poster Number: CE-36

Authors: Roya Solhmirzaei, Venkatesh Kodur

Title:  Shear Behavior of Ultra High Performance Fiber Reinforced Concrete Beams

 

Abstract: Ultrahigh performance fiber reinforced concrete (UHPFRC) is an advanced cementitious material made with low water to binder ratio and high fineness admixtures; and possess superior mechanical properties, such as high compressive and tensile strength, improved durability and ductility properties. Being a relatively new construction material, there are limited experimental studies on shear behavior of UHPFRC beams at structural level. To develop an understanding on shear behavior of UHPFRC beams, two beams made of UHPFRC were tested under predominant shear loading. The beams were not provided with any shear reinforcement in order to take advantage of high tensile strength offered by UHPFRC. To capture cracking patterns and their propagation, a special digital image correlation (DIC) technique was utilized. In the presentation, detailed results including load-deflection response, crack propagation, and failure patterns will be presented. In addition, the feasibility of designing UHPFRC beams without any additional shear reinforcement (stirrups) will be discussed.

 

 

 

Poster Number: CE-37

Authors: Steven Stapleton, Timothy Gates

Title:  Assessing Driver Yielding Compliance at Uncontrolled Midblock Pedestrian Crossing Areas on Low Speed Roadways

 

Abstract: A field study was performed to compare the relative effectiveness of various types of countermeasures commonly utilized at uncontrolled midblock crosswalks.  A variety of crosswalk treatments were evaluated in a cross-sectional study at 31 low-speed midblock crosswalks located on or near three public universities in lower Michigan.  The locations included unmarked crosswalks, in addition to various crosswalk marking strategies with and without additional enhancement devices, which included the pedestrian hybrid beacon (PHB), rectangular rapid flashing beacon (RRFB), and in-street R1-6 signs.  Driver yielding compliance to pedestrian crossing events was the measure of effectiveness, which served as a surrogate for crashes due to a lack of adequate crash data.  To isolate the crosswalk treatment effects, several roadway and traffic characteristics were included in the analysis, including crossing width, vehicular and pedestrian volumes, lane position of the vehicle, and position of the vehicle within a queue.  The logistic regression model results indicated that the type of crosswalk treatment has a strong influence over driver yielding compliance.  While yielding compliance improves substantially when crosswalk markings are utilized, the highest compliance rates are achieved when an additional enhancement device (i.e., RRFB, PHB, or R1-6 sign), is also provided.  Furthermore, yielding compliance showed little sensitivity to driver lane position at locations where a crosswalk enhancement device was utilized.  Yielding compliance rates also showed improvements across each of the crosswalk enhancement devices compared to prior studies performed within Michigan, suggesting that compliance improves as drivers become more familiar with these devices.

 

 

 

Poster Number: CE-38

Authors: Timothy J. Gates, Peter T. Savolainen, Steven Stapleton, Trevor Kirsch, Santosh Miraskar

Title:  Development of Safety Performance Functions and Other Decision Support Tools to Assess Pedestrian and Bicycle Safety

 

Abstract: A field study was performed at 40 uncontrolled crosswalks and 26 signalized intersections on low-speed roadways at three major college campuses across lower Michigan. An array of existing traffic control devices existed at study sites, including various crosswalk marking strategies, and enhanced devices: PHBs, RRFBs and single in-street R1-6 signs. Sites included a variety of roadway and traffic characteristics, including crossing widths, median presence, and vehicular, pedestrian, and bicyclist volumes. Three evaluations were performed for the midblock segments and signalized intersection study sites: driver yielding compliance, vehicle-pedestrian conflicts, and non-motorized traffic crash data. The yielding compliance study found that the type of crosswalk treatment has a strong influence over driver yielding compliance, finding that the highest compliance rates occur when an additional enhancement device is provided. To supplement small crash sample sizes at study sites, Michigan statewide pedestrian and bicyclist crash data were collected and utilized to develop safety performance functions (SPFs) for predicting pedestrian and bicyclist crashes. Because pedestrian and bicyclist volumes were not available statewide, models were developed for pedestrian and bicycle crashes based solely on vehicular AADT. In general, the models showed that pedestrian and bicycle crashes increase with increasing traffic volumes. However, even in the highest volume cases, only a fraction of crashes involved a pedestrian or bicyclist. Pedestrian and bicycle crashes were further estimated based on the respective proportion of the Michigan specific SPF models for total crashes. The primary limitation towards prediction of pedestrian and bicycle crashes is the lack of reliable exposure data.

 

This work was supported in part by TRCLC

 

 

 

Poster Number: CE-39

Authors: Jacob Swanson, Timothy Gates

Title:  Safety Performance for Rural Trunkline Four-leg, Two-way Stop Controlled Intersections in Michigan

 

Abstract: More than 20 percent of all traffic fatalities in the United States occur at intersections and over 80 percent of intersection-related fatalities in rural areas occur at un-signalized intersections (FHWA). Of the 893 fatal crashes in Michigan in 2015, 223 (25%) occurred at intersections. When compared to all other intersection control types; intersections with stop signs represent the highest percentage of fatal crashes, with almost 40% (MTCF). To address the evident safety concerns, research has been ongoing for rural intersections within the state of Michigan; with the focus of the research concentrating on the development of safety performance functions (SPF’s) for rural four-leg, 2-way stop controlled intersections. Safety performance functions are a vital element of the Highway Safety Manual (HSM) statistical methods. SPF’s are regression models that work to correlate geometric roadway characteristics and traffic volumes with the expected number of crashes for specific site types and conditions. The SPF’s involved with this research will be a function of various factors; including, functional classification, number of lanes and their designations (left, right, thru), skew angle, number of driveways for each leg, and other factors (presence of railroad, sidewalk, pedestrian signal, flasher, and/or median). The intersection data has been collected for more than 20 counties across Michigan and has been joined together with Michigan’s traffic crash data from 2011-2015. An analysis will be performed on the merged data and a safety performance function will be developed for rural four-leg, two-way stop controlled intersections.

 

This work was supported in part by Michigan Department of Transportation

 

 

 

Poster Number: CE-40

Authors: Suhail Hyder Vattathurvalappil, Mahmoodul Haq

Title:  Experimental and Numerical Modeling of Tri-axial Braided CFRP Crush-tubes

 

Abstract: The demand for novel crush tubes with high specific energy absorption has increased to meet the light-weighting goals, the stringent transportation safety requirements, and to produce high-safety ratings in vehicles. Despite the high specific stiffness and impact damage tolerance of braided composites, they are not extensively used in the automotive applications due to their complexity and limited understanding compared to conventional metal crash cans. In this work, experimental and numerical characterization of tri-axial braided composites for use in novel crush tubes is explored. Compressive coupon tests were performed and used to validate meso-scale unit-cell models. Resulting model/behavior was used to study the progressive compressive behavior of the cylindrical (6 in. long and 3 in. diameter) crush tube. Finally, experimental quasi-static compressive tests were performed on similar crush tubes to validate the numerical model. Preliminary results show that the numerical models agree reasonably with the experimental results. Future work would extend this work at higher strain rates and validate models can be used for better design of braided crush tubes.

 

 


 

Poster Number: CE-41

Authors: Lijiang Xu, Mingzhe Li, Weiyi Lu

Title:  Influence of Pore Size on Yielding Strength of Ceramic Based Nanofoams

 

Abstract: Light-weight and strong structural components are desired for many engineering applications including airplanes, spacecraft and cars, helping to improve fuel efficiency, as well as in mobile electronics and biomedical devices. To enhance the loading carrying capability and extend service life, high yield strength is needed. Although foams are one major type of light-weight materials, the specific yield strength (σy/ρ) of these hollow structures is a constant by first order of estimation. In order to develop light but strong materials, i.e., increased value of the specific yield strength, one possible solution is ceramic based foams with nanoscale pores. The size effect on the elastic limit of ceramics is well known. In foams, once the pore size is reduced to nanometer scale, the size and density of defects can be much reduced, and thus the elastic limit can be significantly improved. To validate our hypothesis, we have conducted compressive tests on nanoporous silica gels, the most widely used nanoporous material. Four types of nanoporous silica spheres with same particle size and porosity but different nanopore sizes (10 nm, 20 nm, 30 nm, and 100 nm) were selected and pre-compressed by an Instron universal tester. Due to the nanopore size distribution and system compliance, the elastic limit was not directly observed from the stress-strain curves. Alternatively, we employed the liquid infiltration tests to analyze the degree of plastic deformation in the silica gels by evaluating the remaining porosity of the silica gels after mechanical compression. In addition, the effect of nanopore size on elastic limit of the nanoporous silica gels were studied by combining gas adsorption analysis with the mechanical tests. Our experimental results suggest that when the nanopore size is reduced from macroporous (>50 nm) to mesoporous (2 nm - 50 nm), the elastic limit of the nanofoams are increased. In mesoporous range, the smaller nanoporous silica gels possess higher elastic limit which may be attributed to the reduced defects of ceramics, corresponding to the assumption. These findings suggest that nanofoams bring us a promising way to design lightweight, strong, and durable materials.