STR-840: INVESTIGATION OF LIVE LOAD MOMENT AND SHEAR FOR THE DESIGN OF BRIDGE DECK SLAB CANTILEVERS WITH UNSTIFFENED EDGE OR BUILT WITH TL-5 BARRIER WALL

This study builds on the methods of analyses with respect to cantilever slabs in the Canadian Highway Bridge Design Code (CHBDC), and recommends new simplified equations for the intensity of the transverse moment and shear force at the base of the cantilever overhang due to applied vertical truck loading. A parametric study was conducted using finite-element modelling on bridge deck cantilevers with variable lengths and slab thicknesses. Different end stiffening arrangements were considered, including the presence of PL-3 barriers walls (recently renamed to TL-5) as well as the concrete curb supporting intermittent steel posts carrying the bridge railing. The barrier length changed from 3 to 12 m, while the cantilever length ranged from 1.0 to 3.75 m. The results of this study complement the empirical expressions developed by others to determine the minimum required factored moment and tensile force resistance at the deck-barrier junction, induced by horizontal railing loads. Further to presenting design charts and empirical equations based on a series of cantilever-barrier configurations, this study gives way to the development of a suitable procedure for designing the bridge deck slab

STR-831: FATIGUE STRENGTH OF ANGLE-SHAPED TRANSVERSE CONNECTION FOR GFRP-REINFORCED PRECAST FULL-DEPTH DECK PANELS IN ACCELERATED BRIDGE CONSTRUCTION

Prefabricated bridges elements and systems (PBES) are subjected to repeated truck loads while being exposed to weather conditions. Fatigue of the structural elements and corrosion of the reinforcement are the main reasons for bridge deterioration. This research investigates the fatigue strength of full-depth deck panels (FDDP) resting over steel cross-braced girders and reinforced with ribbed-surface, high-modulus (HM), glass fiber reinforced polymer (GFRP) bars. The precast FDDP has transverse panel-to-panel connection of angle-shape with female shear key, and panel-to-girder connection of V-shape, where both connections are filled with ultra-high performance fiber reinforced concrete (UHPFRC). Two different fatigue loading were conducted to simulate the Canadian Highway Bridge Design Code (CHBDC) truck loading, namely: constant amplitude fatigue (CAF) loading and variable amplitude fatigue (VAF) loading. The fatigue damage for all cycles is summed to obtain the cumulative fatigue damage (CFD) for the entire loading history. The reliability of the GFRP-reinforced precast FDDP subjected to high cycle fatigue is then evaluated based on load-cycle (P-N) damage accumulation approach. A simple life-span prediction model is proposed for the FDDP based on the CFD

STR-894: BOND STRENGTH OF RIBBED-SURFACE HIGH-MODULUS GLASS FRP BARS EMBEDDED INTO UNCONFINED UHPFRC

High-modulus (HM) ribbed-surface glass fiber reinforced polymer (GFRP) bars have recently been used in concrete bridge decks to avoid corrosion of steel reinforcement resulting from the use of de-icing salts in winter times in North America. Recently, prefabricated full-depth deck panels (FDDPs), made of normal strength concrete or high performance concrete and reinforced with GFRP bars, are used in Canada to acceleration bridge construction. The FDDPs are connected through panel-to-panel and panel-to-girder connections. These connections are filled with joint-filled cementitious materials as ultra-high performance fiber-reinforced concrete (UHPFRC). This paper presents the experimental program to investigate the bond strength of the GFRP bars embedded into unconfined UHPFRC using pull-out testing, leading to the proper GFRP bar development length required to determine the width of the closure strip between connected slabs. The longitudinal GFRP/UHPFRC interface is influenced by (i) the development length-to-nominal diameter of the bar ratio, (ii) the concrete cover-to-bar diameter ratio and (iii) the development length-to-embedment depth ratio due to lugs or headed-end and (iv) concrete compressive strength. GFRP bars embedded into UHPFRC would rely less on the friction and adhesion of the interface, and more on the bearing of the lugs against the concrete. These bearing forces act at an angle to the axis of the bar, causing radial outward forces. Pullout failure of the GFRP/UHPFRC interface leads to shearing of the lugs and bar slippage from the headed-end. Adequate bond strength between the GFRP/UHPFRC interfaces is necessary for design of jointed PDDFs. Therefore, accurate predictions of development length and bond strength of straight or headed-end bars without passing through the high localized stresses due to flexural are essential for safe design

STR-877: FINITE-ELEMENT MODELING FOR FRP STRENGTHENING OF PRESTRESSED CONCRETE BOX GIRDER BRIDGES BUILT BY CANTILEVER METHOD

Balanced cantilever construction is an economical method when access from below is expensive or practically impossible. In segmental balanced cantilever construction the precast segments are transported to the bridge construction site and placed and held at the right position before post-tensioning back to the rest of the bridge. As the construction stages go on, the statically determinate structure changes to a statically indeterminate one, which should be considered in the design process. Creep and shrinkage of concrete and relaxation of prestressing steel may lead to excess long-term deflection and may cause redistributions in internal forces and stresses. In the previous study (Hedjazi et. al.) a general simulation for time-dependent analysis of segmentally erected prestressed concrete box-girder bridges has been presented. A three dimensional finite-element model for the balanced-cantilever construction of segmental bridges, including effects of the load history, material nonlinearity, creep, shrinkage, and aging of concrete and relaxation of prestressing steel was developed using ABAQUS software. The analysis has shown significant changes in the values of deflections, longitudinal stresses and internal forces as a result of long-term effects of creep and shrinkage of concrete and relaxation of the prestressing steel which has led to new arrangement and the increase in the number of mid-span continuity cables. But some times, adding new cables or rearranging the cables in existing bridges, is impossible. In these cases strengthening of the deck is a fast and economical solution. The aim of this study is to analyze the structural behavior of prestressed concrete box girder bridges when strengthening with fiber reinforced polymer laminates (FRP). Three examples of prestressed concrete box-girder bridges segmentally-erected using the balanced-cantilever technique have previously discussed to demonstrate their long-term behavior under dead load and effects of live load at the end of construction and different ages up to a thousand days by performing nonlinear analysis up to failure. In the present study, same examples of prestressed concrete box-girder bridges is being strengthened using FRP laminates. A moment–curvature analysis was subsequently carried out to investigate the flexural characteristics of the prestressed concrete box-girder bridges prior to and after strengthening with CFRP laminates. The results shows that significant strength can be gained at the ultimate limit state. The increase in flexural resistance at ultimate does provide an adequate margin of safety against further overloading

STR-878: NUMERICAL MODELING FOR STRUCTURAL BEHAVIOR OF BRIDGE DECK BARRIERS MADE OF FIBER REINFORCED CONCRETE

Nonlinear finite-element (NLFE) analysis was used to compare and optimize the load transfer and failure mode of bridge barriers subjected to static transverse loads. Concrete is a material that needs strengthening in tension in order to meet the structural requirements. Studies have shown that the addition of steel fibers in a concrete matrix improves all the mechanical properties of concrete, especially tensile strength, impact strength, and toughness. The resulting material possesses higher tensile strength, consolidated response and better ductility. Although fiber reinforcement is a method that has been in use over the last few decades, yet it is unfamiliar to some practices, and there is no common guideline for design using this method. It is now well established that one of the important properties of fiber reinforced concrete (FRC) is its superior resistance to cracking and crack propagation and also the fibers are able to hold the matrix together even after extensive cracking. In the present study, numerical finite-element analysis has been performed on selected bridge barriers with steel reinforcement, to compare the difference between barriers with normal and fiber reinforced concrete. The FE modeling was performed under static load testing with displacement control. The ultimate load carrying capacities for each barrier type was compared. The behaviors of FRC barriers with different amount of fibers were accurately simulated with NLFE models. Modifications were then made to FRC barriers to reduce the barrier wall thickness as well as the reinforcement arrangement. The present study shows reserved capacity of FRC barriers compared to their counterparts with normal concrete and steel reinforcement

MAT-702: MECHANICAL BEHAVIOUR OF ULTRA-HIGH PERFORMANCE CONCRETE OBTAINED WITH DIFFERENT CONCRETE CONSTITUENTS AND MIX DESIGNS

This research investigates the mechanical behaviour for the Ultra-High Performance Concrete (UHPC) and UltraHigh Performance Fiber Reinforced Concrete (UHPFRC). UHPC and UHPFRC are designed to be self-consolidated concrete that level itself without mechanical vibration due to its highly flowability and moderate viscosity. UHPFRC is used as joint-fill cementitious materials for the connections of prefabricated bride elements and systems used for the Accelerated Bridge Construction and rapid bridge replacement. The main concrete constituents of such materials consist from: binders (cement), powders (fillers), liquids (additives), water, and fibers. Hence, the mixture proportion design should follow a densified mixture design algorithm to densify the particle packing that reduces the amount of pores and reduces the water/binder ratio to attain the design criteria. The concrete mix design has two approaches, namely: classical mixture including the response surface methodology and factorial-based central composite design, also known as the mathematically independent variable. Experimental work is conducted to determine the optimum particle size distribution and to identify the chemical effects followed by parametric experimental tests on different concrete constituents to develop series of UHPC/UHPFRC products and monitor there rheological behavior

MAT-732: EXPERIMENTAL STUDY ON THE CAPACITY OF BARRIER DECK ANCHORAGE IN MTQ PL-3 BARRIER REINFORCED WITH HM-GFRP BARS WITH HEADED ENDS

A recent design work conducted at Ryerson University on PL-3 bridge barrier has led to an economical glass fibre reinforced polymer (GFRP) bar detailing for sustainable construction. A PL-3 barrier wall of 27.6 m length was constructed using the proposed GFRP bar configuration, incorporating the use of V-Rod headed-end bars. The proposed barrier configuration was recently crash tested to qualify its use in Canada’s highway bridges. Then, wall segments of this barrier were tested under static loading to-collapse to determine their structural behavior, crack pattern and ultimate load carrying capacity under simulated vehicle impact load. Test results led to establishing two Standard drawings by Ontario Ministry of Transportation (MTO) for use by consulting engineers and contractors. The crash-tested barrier dimensions were identical to those specified by Ministry of Transportation of Quebec (MTQ) for PL-3 barrier except that the base of the barrier was 40 mm short and the deck slab is of 200 mm thickness, leading to reduction in the GFRP embedment depth into the deck slab. As such, Ryerson University research team proposed an experimental program to ensure that the resistance of barrier-deck junction, with the reduced width of barrier base and thickness of the deck slab, is greater of equal to the specified factored design load applied to the barrier wall simulating vehicle impact. This paper summarizes the experimental program to justify the modified barrier design to fit with MTQ barrier and deck slab dimensions and experimental findings when compared to the available factored applied moments specified in CHBDC of 2006 for the design of barrier-deck junction. Correlation between the experimental findings and the factored applied moments from CHBDC equivalent vehicle impact forces resulting from the finite-element modelling of the barrier-deck system was conducted followed by recommendations for use of the proposed design in highway bridges in the Province of Quebec

STR-832: ULTIMATE FLEXURAL STRENGTH AND LONG-TERM CREEP DEFLECTION FOR STRUCTURAL INSULATED FOAM-TIMBER SANDWICH PANELS

The structural insulated panel (SIP) is a sandwich structured composite that is prefabricated by attaching a lightweight thick core made of Expanded Polystyrene (EPS) foam laminated between two thin, and stiff face skins made of Oriented Strand Board (OSB). The use of sandwich panels provides key benefits over conventional materials including: very low weight; high stiffness; durability and; production and construction cost savings. The facing skins of the sandwich panel can be considered as the flanges for the I-beam carrying bending stresses in which one face skin is subjected to tension, and the other is in compression. The core resists the shear loads and stabilizes the skin faces together giving uniformly stiffened panel. OSB is wood product that shrinks when dry and swells when adsorb moisture either due to liquid or vapor from the surrounding atmosphere. The relative combination of relative humidity and temperature is introduced into the equilibrium moisture content (EMC) that increases with the increase of the relative humidity and with decreasing temperature. Experimental test matrix includes testing 2.44 m (8’) and 4.88 m (16’) long SIPs for 5 years under different sustained loads and weather resistive barriers (WRBs), recording creep deflection, relative humidity and temperature. After creep recovery, the SIPs are loaded to-collapse to determine their flexural strength

Progressive Collapse Resistance of RC Beam–Slab Substructures Made with Rubberized Concrete

Abnormal loads can produce localized damage that can eventually cause progressive collapse of the whole reinforced concrete (RC) structure. This might have devastating financial repercussions and cause numerous severe casualties. Numerical simulation, using the finite element method (FEM), of the consequences of abnormal loads on buildings is thus required to avoid the significant expenses associated with testing full-scale buildings and to save time. In this paper, FEM simulations, using ABAQUS software, were employed to investigate the progressive collapse resistance of the full-scale three-dimensional (3D) beam–slab substructures, considering two concrete mixes, namely: normal concrete (NC) and rubberized concrete (RuC) which was made by incorporating crumb rubber at 20% by volume replacement for sand. The FEM accuracy and dependability were validated using available experimental test results. Concrete and steel material non-linearity were considered in the FE modelling. The numerical study is extended to include eight new models with various specifics (a set of parameters) for further understanding of progressive collapse. Results showed that slabs contribute more than a third of the load resistance, which also significantly improves the building’s progressive collapse resistance. Moreover, the performance of the RuC specimens was excellent in the catenary stage, which develops additional resilience to significant deformation to prevent or even mitigate progressive collapse