Cellular Automata Model for Predicting the Failure Pattern of Laterally Loaded Masonry Wall Panels

This paper introduces a technique that directly predicts the failure patterns of laterally loaded masonry panels based on the results of existing typical panels tested in the laboratory. The technique is based on the use of the cellular automata (CA). In this technique, the CA modeling is established to propagate boundary effects to zones within a panel. The corresponding rules for the state values of zones are derived from the proposed CA model, using appropriate transition functions. These state values are then used by the CA to establish zone similarity between two panels. Finally, the zone similarity is applied to establish locations of cracks on the panel. The technique is used in a novel way that eliminates the use of any numerical tools such as finite-element analysis (FEA). This technique is purely based on comparing the failure pattern of the base panel (a panel whose failure pattern is known from the laboratory tests) and unseen panels (panels not tested in the laboratory by the writers or with unknown failure patterns) subjected to the same type of loading and with similar boundary conditions to predict the failure load of the unseen panels.     

Structural Characterization of Composite Structural Insulated Panels for Exterior Wall Applications

Structural sandwich composite panels are extensively used for modular panelized construction. This paper includes the structural characterization of the innovative composite structural insulated panels (CSIPs) developed for the exterior walls of a modularized structure. The facesheets of the CSIPs consist of E-glass fibers impregnated with polypropylene matrix, while the core consists of expanded polystyrene foam. The overall panel dimensions including the thickness of the facesheets and the core were obtained using sandwich composite design theories. Uniaxial compressive loading and high velocity impact (HVI) loading are the most important loading criteria for an exterior wall of a structure. The proposed CSIPs were tested for a compressive load of 13.13 kN/m (900 plf) in this study. The deflection at this load was ～ 3?mm which was within deflection limits of span/150 as prescribed in ACI 318-05 building design code. The proposed CSIP wall panels were also tested under HVI for the loads prescribed by Federal Emergency Management Agency for design of emergency shelters in hurricane prone areas. Based on the HVI testing, CSIPs were able to stop a blunt object projectile traveling at 135 m/s proving its suitability against HVI type of loading.     

Compound Shear-Flexural Capacity of Reinforced Concrete–Topped Precast Prestressed Bridge Decks

Modern concrete bridge decks commonly consist of stay-in-place (SIP) precast panels seated on precast concrete beams and topped with cast-in-place (CIP) reinforced concrete. Such composite bridge decks have been experimentally tested by various researchers to assess structural performance. However, a failure theory that describes the failure mechanism and accurately predicts the corresponding load has not been previously derived. When monotonically increasing patch loads are applied, delamination occurs between the CIP concrete and SIP panels, with a compound shear-flexure mechanism resulting. An additive model of flexural yield line failure in the lower SIP precast prestressed panels and punching shear in the upper CIP-reinforced concrete portion of the deck system is derived. Analyses are compared to full-scale experimental results of a tandem wheel load straddling adjacent SIP panels and a trailing wheel load on a single panel. Alone, both yield line and punching-shear theories gave poor predictions of the observed failure load; however, the proposed compound shear-flexure failure mechanism load capacities are within 2% accuracy of the experimentally observed loads. Better estimation using the proposed theory of composite SIP-CIP deck system capacities will aid in improving the design efficiency of these systems.     

Techniques for Predicting Cracking Pattern of Masonry Wallet Using Artificial Neural Networks and Cellular Automata

This paper introduces innovative artificial intelligent techniques for directly predicting the cracking patterns of masonry wallets, subjected to vertical loading. The von Neumann neighborhood model and the Moore neighborhood model of cellular automata (CA) are used to establish the CA numerical model for masonry wallets. Two new methods—(1) the modified initial value method and (2) the virtual wall panel method—that assist the CA model are introduced to describe the property of masonry wallets. For practical purposes, techniques for the analysis of wallets whose bed courses have different angles with the horizontal bottom edges are also introduced. In this study, two criteria are used to match zone similarity between a “base wallet” and any new “unseen” wallets. This zone similarity information is used to predict the cracks in unseen wallets. This study also uses a back-propagation neural network for predicting the cracking pattern of a wallet based on the proposed CA model of the wallet and some data of recorded cracking at zones. These techniques, once validated on a number of unseen wallets, can provide practical innovative tool for analyzing structural behavior and also help to reduce the number of expensive laboratory test samples.     

Structural Characterization of Hybrid Fiber-Reinforced Polymer-Glulam Panels for Bridge Decks

The structural characterization of hybrid fiber-reinforced polymer (FRP)–glued laminated (glulam) panels for bridge deck construction is examined using a combined analytical and experimental approach. The structural system is based on the concept of sandwich construction with strong and stiff FRP composite skins bonded to an inner glulam panel. The FRP composite material was made of E-glass reinforcing fabrics embedded in a vinyl ester resin matrix. The glulam panels were fabricated with bonded eastern hemlock vertical laminations. The FRP reinforcement was applied on the top and bottom faces of the glulam panel by wet layup and compacted using vacuum bagging. An experimental protocol based on a two-span continuous bending test configuration is proposed to characterize the stiffness, ductility, and strength response of FRP-glulam panels under simulated loads. Half-scale FRP-glulam panel prototypes with two different fiber orientations, unidirectional (0°) and angle-ply (±45°), were studied and the structural response correlated with control glulam panels. A simple beam linear model based on laminate analysis and first-order shear deformation theory was proposed to compute stiffness properties and to predict service load deflections. In addition, a beam nonlinear model based on layered moment-curvature numerical analysis was proposed to predict ultimate load and deflections. Correlations between experimental results and the two proposed beam models emphasize the need for complementing both analytical tools to characterize the hybrid panel structural response with a view toward bridge deck design.     

Full-Scale Impact Test of Four Traffic Barriers on Top of an Instrumented MSE Wall

This paper presents the results of four full-scale impact tests against barriers placed on top of an instrumented mechanically stabilized earth (MSE) wall. The impact was created by a head-on collision of a 2,268-kg bogie going at about 32.2 km/h. The barriers were New Jersey and vertical wall barriers with a 1.37-m-wide moment slab in 9.14-m-long sections. The wall was 1.52 m high with one panel and two layers of reinforcement. The reinforcement was 2.44-m-long strips, 4.88-m-long strips, and 2.44-m-long bar mats. The backfill was crushed rock. The instrumentation consisted of accelerometers, strain gauges, contact switch, displacement targets, string lines, and high-speed cameras. The test was designed to represent a commonly used installation in current practice including an impact load on the barrier at least equal to 240 kN. Most of the barriers sustained significant damage but overall the behavior of the wall was satisfactory since the displacements of the panels were minimal (less than 25 mm) and the panel damage was acceptable except possibly in the case of the 4.88-m-long strips. The loads measured in the reinforcement indicate that the reinforcement was brought to its ultimate capacity for the duration of the impact but since the impact duration was so short and since the displacements of the panels were within tolerable limits of 25 mm, this is considered acceptable. The use of the longer strips (4.88-m-long strips) leads to slightly smaller panel displacements and higher panel stresses as evidenced by a bending crack in the panel. The 2.44-m-long strips permitted more displacement of the wall panels, but the magnitude of the displacement was considered to be tolerable. The measured maximum dynamic loads in the strips were found to be 3–5 times higher than the calculated maximum static loads by AASHTO guidelines.     

Flexural Testing of Precast Bridge Deck Panel Connections

Precast deck panels are increasingly being utilized to reduce construction times and traffic delays as many departments of transportation (DOTs) emphasize accelerated bridge construction. Despite the short-term benefits, the connections between panels have a history of service failure. This research focused on the evaluation of the service and ultimate capacities of five precast deck panel connections. Full-scale tests were developed to determine the cracking and ultimate flexural strengths of two welded connections, a conventionally posttensioned connection, and two newly proposed, posttensioned, curved bolt connections. The conventionally posttensioned specimens were shown to perform well with the highest cracking loads and 0.42 times the theoretical capacity of a continuously reinforced concrete deck panel. The proposed curved bolt connections were shown to be a promising connection detail with approximately 0.5 times the theoretical capacity of a continuously reinforced panel. Data from the welded specimens showed that some welded connection types perform significantly better than others. The experimental results also compared closely with values calculated on the basis of finite-element modeling, which can be used for future analytical studies.     

Out-of-Plane Strengthening of Masonry Walls with Reinforced Composites

This paper presents an investigation into the effectiveness of using fiber-reinforced composite overlays to strengthen existing unreinforced masonry walls to resist out-of-plane static loads. A total of fifteen wall panels [1,200 × 1,800 × 200 mm (4 ft × 6 ft × 8 in.)] were tested. Twelve panels were assembled with fiber-reinforcing systems attached to the tension side, and the remaining three control walls were left without any external reinforcement. Two configurations of external reinforcement were evaluated. The first reinforcement configuration consisted of two layers of fiber-reinforced plastic webbing and the second consisted of vertical and horizontal bands of undirectional fiber composites. The three wall specimens without external reinforcement were tested to evaluate the change in the system strength and behavior with application of the external reinforcing systems. In addition to the two fiber configurations, the testing program also evaluated two methods of surface preparation of the walls, sand blasting, and wire brush. All specimens were thoroughly washed by water jet, 48 hours prior to application of the fiber-reinforcing systems. Three specimens were tested for each variable. A uniformly distributed lateral load was applied to each panel using the procedures described in the ASTM Standard E-72 Test Method (airbag). Failure loads, strains in the external reinforcement (FRP), out-of-plane deformations, and failure modes were recorded. Recommendations on the usefulness of the proposed technique as a means of strengthening masonry walls for out-of-plane loads are presented. In general, flexural strength of masonry walls can be increased if the shear failure is controlled.     

Fatigue Testing of Traffic Tunnel Panels

An original method is presented for fatigue testing of tunnel panels that are dynamically loaded by pressure waves caused by car and truck traffic. The dynamic pressure load on the tunnel walls is measured at the site and simulated in a real-size laboratory testing procedure, in which pressure and suction loads are generated by a bellow system. The bellow system simulates the maximum loads caused by vans and small trucks. Additionally, a high frequency load is applied by means of a vibrator placed in the antinode of the most important mode shape of the panel system. The loading frequency is imposed close to the corresponding natural frequency of the panel and fixation system. In this vibration loading, the behavior of the panel system during the real life span is controlled. The testing system allows for optimization of both the panel composition and the attachment system.     

Fatigue in selectively fiber-reinforced titanium matrix composites

Many applications of the Ti alloy matrix composites (TMCs) reinforced with SiC fibers are expected to use the selective reinforcement concept in order to optimize the processing and increase the cost-effectiveness. In this work, unnotched fatigue behavior of a Ti-6Al-4V matrix selectively reinforced with SCS-6 SiC fibers has been examined. Experiments have been conducted on two different model panels. Results show that the fatigue life of the selectively reinforced composites is far inferior to that of the all-TMC panel. The fatigue life decreases with the decreasing effective fiber volume fraction. Suppression of multiple matrix cracking in the selectively reinforced panels was identified as the reason for their lack of fatigue resistance. Fatigue endurance limit as a function of the clad thickness was calculated using the modified Smith-Watson-Topper (SWT) parameter and the effective fiber volume fraction approach. The regime over which multiple matrix cracking occurs is identified using the bridging fiber fracture criterion. A fatigue failure map for the selectively reinforced TMCs is constructed on the basis of the observed damage mechanisms. Possible applications of such maps are discussed.     

Ground Movements Associated with Wall Construction: Case Histories

The construction of diaphragm wall panels can cause movements to the adjacent ground. The magnitude of the movements depends on various factors such as the construction technique, soil type, and panel dimensions. These movements can be excessive if the wall dimensions and construction technique are not properly chosen or the process of wall construction is not properly controlled. This paper presents four case histories on the adjacent ground response to the construction of diaphragm wall panels. The aspects of performance monitored include lateral soil movements and soil settlements. The monitoring results indicated that the lateral soil movements caused by the construction of wall panels increased with increasing wall dimension. These results suggest that the magnitude of the lateral soil movements could be minimized by reducing the dimensions of the wall panels. The results also suggest that the use of high slurry levels during the construction of the wall panels would help to minimize the lateral soil movements.     

In-Plane Shear Behavior of Masonry Panels Strengthened with NSM CFRP Strips. I: Experimental Investigation

An experimental investigation was conducted to study the in-plane shear behavior of masonry panels strengthened with near-surface mounted (NSM) carbon fiber-reinforced polymer strips (CFRP). As part of the study four unreinforced masonry panels and seven strengthened panels were tested in diagonal tension/shear. Different reinforcement orientations were used including vertical, horizontal, and a combination of both. The effect of nonsymmetric reinforcement was also studied. The results of these tests are presented in this paper, and include the load-displacement behaviors, crack patterns, failure modes, and FRP strains. The results showed that the vertically aligned reinforcement was the most effective, with significant increases in strength and ductility observed. The dowel strength of the vertical reinforcement did not likely contribute significantly to the shear resistance of the masonry. Instead, it was likely that the vertical reinforcement acted in tension to restrain shear induced dilation and restrain sliding. In some panels cracking adjacent to the FRP strip, through the panel thickness was observed. This type of cracking reduced the bond between one side of the FRP strip and the masonry, and led to premature debonding. A comparison of the test results with the results of other tests from the literature is also presented in this paper.     

Replication bypass and mutagenic effect of alpha-deoxyadenosine site-specifically incorporated into single-stranded vectors

OBJECTIVES: The aims of the study were to 1) assess the effects of 12 weeks of exercise training at low work loads (i.e., corresponding to < or = 50% of peak oxygen consumption [Vo2]) on peak Vo2 and hyperemic calf blood flow in patients with severe congestive heart failure; and 2) evaluate left ventricular diastolic pressure and wall stress during exercise performed at work loads corresponding to < or = 50% and 70% to 80% of peak Vo2. BACKGROUND: Whether the benefits of exercise training can be achieved at work loads that result in lower left ventricular diastolic wall stress than those associated with conventional work loads is unknown in patients with severe congestive heart failure. METHODS: Sixteen patients with severe congestive heart failure trained at low work loads for 1 h/day, four times a week, for 12 weeks. Peak Vo2 and calf and forearm reactive hyperemia were measured before and during training. Nine of the 16 patients underwent right heart catheterization and echocardiography during bicycle exercise at low and conventional work loads (i.e., 50% and 70% to 80% of peak Vo2, respectively). RESULTS: The increase in left ventricular diastolic wall stress was substantially lower during exercise at low work loads than during exercise at conventional work loads, (i.e., [mean +/- SEM] 23.3 +/- 7.4 vs. 69.6 +/- 8.1 dynes/cm2 (p < 0.001). After 6 and 12 weeks of training, peak Vo2 increased from 11.5 +/- 0.4 to 14.0 +/- 0.5 and 15.0 +/- 0.5 ml/kg per min, respectively (p < 0.0001 vs. baseline for both). Peak reactive hyperemia significantly increased in the calf but not in the forearm. The increases in peak Vo2 and calf peak reactive hyperemia correlated closely (r = 0.61, p < 0.02). CONCLUSIONS: In patients with severe congestive heart failure, peak Vo2 is enhanced by exercise training at work loads that result in smaller increases in left ventricular diastolic wall stress than those observed at conventional work loads.     

轻质混凝土拼装墙板填充钢框架协同抗震性能试验研究

为了研究墙板与钢框架结构之间的协同抗震性能,对采用不同墙框连接节点的轻质混凝土拼装墙板填充钢框架进行了低周往复荷载试验。通过对比试件的承载力、滞回性能、刚度、耗能以及延性性能,探讨了轻质混凝土拼装墙板及其整体性对结构抗震性能的影响。结果表明:填充墙板钢框架结构的最终破坏形态以墙板挤压开裂,框架梁柱端部翼缘屈曲为主;轻质混凝土拼装墙板与钢框架协同工作,有利于提高结构整体的承载力和变形能力,减轻钢框架在平面内的屈曲破坏;与刚性节点相比,采用柔性节点连接墙板与钢框架对结构的承载力、层间刚度和耗能能力更为有利;增强拼装墙板的整体性,有助于提高结构整体刚度、变形和耗能能力。研究结果可为轻质混凝土拼装墙板填充钢框架结构的抗震设计提供参考。      

Endurance of Deck-to-Deck Connections in Transverse Hardwood Glulam Decks

Dowel and stiffener beam deck-to-deck connections transfer shear and moment between hardwood glued-laminated (glulam) transverse deck panels in longitudinal timber bridges. The connections resist relative deflections between the deck panels and aid in the prevention of reflexive cracking of the bituminous wearing surface at panel joints. Cyclic loading can reduce the stiffness of some types of deck-to-deck connections resulting in shortened service life. The performance of dowel and stiffener beam deck-to-deck connections for hardwood glulam transverse panel bridge decks was evaluated during cyclic laoding. Five tests were conducted with steel dowel connected deck panels, and five tests were conducted with glulam stiffener beam connected deck panels. Each connection was subjected to 1,000,000 load cycles. Degradation of connector stiffness with increasing number of load cycles was determined. Stiffener beam connections had better cyclic load response than the steel dowel connections. Steel dowel connections experienced approximately 20% degradation of stiffness after 1,000,000 load cycles. Most stiffener beam connections experienced little to no stiffness degradation after 1,000,000 load cycles; the smaller stiffener beam experienced 14% degradation after 1,000,000 load cycles. All connections remained within the limits of deflection criteria established in the 1994 AASHTO LRFD Bridge Design Specifications.     

Free Out-of-Plane Vibrations of Masonry Walls Strengthened with Composite Materials

The natural frequencies and the out-of-plane vibration modes of one-way masonry walls strengthened with composite materials are studied. Due to the inherent nonlinear behavior of the masonry wall, the dynamic characteristics depend on the level of out-of-plane load (mechanical load or forced out-of-plane deflections) and the resulting cracking, nonlinear behavior of the mortar material, and debonding of the composite system. In order to account for the nonlinearity and the accumulation of damage, a general nonlinear dynamic model of the strengthened wall is developed. The model is mathematically decomposed into a nonlinear static analysis phase, in which the static response and the corresponding residual mechanical properties are determined, and a free vibration analysis phase, in which the dynamic characteristics are determined. The governing nonlinear differential equations of the first phase, the linear differential eigenvalue problem corresponding to the second phase, and the solution strategies are derived. Two numerical examples that examine the capabilities of the model and study the dynamic properties of the strengthened wall are presented. The model is supported and verified through comparison with a step-by-step time integration analysis, and comparison with experimental results of a full-scale strengthened wall under impulse loading. The results show that the strengthening system significantly affects the natural frequencies of the wall, modifies its modes of vibration, and restrains the deterioration of the dynamic properties with the increase of load. The quantification of these effects contributes to the understanding of the performance of damaged strengthened walls under dynamic and seismic loads.     

Seismic Damage Thresholds for Gypsum Wallboard Partition Walls

A series of 11 tests of full-scale partition walls were conducted to determine the behavior of nonstructural gypsum wallboard partition walls during lateral deformation as might be expected during a major earthquake. The partition walls were constructed as double-sided, 1/2?in. (13?mm) gypsum wallboard partition walls with wood stud framing. The walls deformed laterally in one of two ways: either as a joint-failure mode with racking of the individual gypsum wallboard panels, or by a pier-rotation mode where all the gypsum wallboard panels in a pier rotated as a unit. In all of the tests, the fasteners failed by pulling through the back of the wallboard panel, cutting of the gypsum, or tearing out through the edge of a wallboard panel. In some tests, the strength of the tape and compound was seen to provide adequate support to cause the walls to roll as a single unit, especially when the spacing of fasteners was large. The maximum load resisted varied from 512?N/m (378?lb/ft) to 1,177?N/m (869?lb/ft) and occurred at drifts between 0.68 and 1.87%. The drift when specific damage thresholds occurred was monitored during testing. Damage initiated with slight cracking of the panels at the wall opening at drifts of 0.25%, followed by increasing damage up to drifts of 2%, and minimal additional damage at drifts above 2%. Damage thresholds for cyclic loading often occurred at lower drifts than comparable specimens under monotonic loading.     

Moment Capacities and Deflection Limits of PFRP Sheet Piles

The structural response of pultruded fiber-reinforced polymer (PFRP) sheet pile panels subjected to a uniform pressure load was investigated. Single, connected, and concrete-backfilled panels were tested to ultimate failure in an attempt to determine their moment capacities, deflection limits, and failure mechanisms. The load-carrying capacity of single-panel FRP piles was found to be 15% higher than that of three panels connected together. No pin and eye joint separation was observed at failure. The concrete backfilled hybrid panels exhibited significantly increased moment capacity. However, the increase in stiffness after the first concrete crack was, at best, only 76% over the pile without backfill. Bearing failure of a PFRP pile with a partially confined support created excessive deflection in the wall, but showed no significant reduction in the load capacity. On the other hand, with fully confined support, the ultimate failure of single, connected, and concrete-backfilled panels was dominated by local buckling, longitudinal tearing, and bearing crush at shear keys, upon reaching a deflection limit of span/50.     

Northern Red Oak Glued-Laminated Timber Bridge

A 5-year program to monitor the performance of a red oak longitudinal girder, transverse deck glued-laminated (glulam) highway bridge is presented. The bridge design details, including preservative treatment results, are described. The live loading results indicate that the predicted and observed live load beam deflections agree to within 7% when the stiffness of the individual beam laminations is used as a predictor and a 10% increase in beam stiffness due to composite action between the deck panel and logitudinal girders is incorporated into the design. The dimensional stability of the deck panels over 3 years has been monitored and analyzed. Significant reflexive cracking of the asphaltic wearing surface has been observed at the interface between each red oak deck panel. This has been attributed to the gap provided between each panel during construction, to the placement of the waterproof membrane directly over the creosote-treated deck panels, and to improper mating of the deck panels to the beams during installation of the lag bolts. Long-term (3-year) dead load deflection measurements indicate that after approximately 1 year, dead load deflections remain nearly constant for the interior beams. Elevations of the lower surface of the two exterior beams fluctuate considerably and vary seasonally. There is no evidence of delamination of the girders or deck panels after 4 years. However, there is some evidence of delamination of the curbs and the tops of rail posts.     

Postbuckling Response Simulations of Laminated Anisotropic Panels

Numerical simulations are used in conjunction with experiments to study the buckling and postbuckling responses and failure initiation of flat, unstiffened composite panels. The numerical simulations are conducted using two‐dimensional shear‐flexible finite elements. The effect of the laminate stacking sequence on the buckling and postbuckling responses is studied. Correlation between numerical and experimental results is good through buckling, but the numerical models overestimate the postbuckling stiffness of the panels when nominal values of the material properties are used. To explain the discrepancies in the postbuckling stiffnesses, analytic sensitivity derivatives are calculated and used to study the sensitivity of the buckling and postbuckling responses to variations in different material and lamination parameters. Experimental results indicate that failure occurs along a nodal line. Numerical results show that the location of failure initiation corresponds to that of the maximum transverse shear‐strain energy density in the panel, which occurs at the edge of the panel at a nodal line. However, the transverse shear deformation has a negligible effect on the global response characteristics of the panel.