Showing papers in "Journal of Performance of Constructed Facilities in 2014"

Damage Assessment of Connections Used in Cross-Laminated Timber Subject to Cyclic Loads

Abstract: Cross-laminated timber (CLT) products are gaining popularity in the North American market and are being used in midrise wood buildings, in particular, in shearwall applications. Shearwalls provide resistance to lateral loads such as wind and earthquake loads, and therefore it is important to gain a better understanding of the behavior of CLT shearwall systems during earthquake events. This paper is focused on the seismic performance of connections between CLT shearwall panels and the foundation. CLT panels are very stiff and energy dissipation is accomplished by the connections. A literature review on previous research work related to damage prediction and assessment for wood frame structures was performed. Furthermore, a test program was conducted to investigate the performance of CLT connections subjected to simulated earthquake loads. Two different brackets in combination with five types of fasteners were tested under monotonic and cyclic loading protocols. In total, 98 connection tests were co...

Fragility Analysis of Skewed Single-Frame Concrete Box-Girder Bridges

Abstract: Damage to skewed bridges in recent earthquakes has reinforced the potential vulnerability of these structures The effect of skew angleonabridge's fragility couldvary for different bridge types, ages, or geometric configurations This paperconducts a probabilistic seismic assessment of skewed bridge performance, focusing on single-frame concrete box-girder bridge subclasses The effect of skew angle on bridge seismicfragilityisinvestigatedforbridgeswithsingle-ortwo-columnbents,integralorseat-typeabutments,andminimalorsignificantlevelsof seismic design Component and system-level damage states consistent with HAZUS-MHdefinitions are also explored in this study The results reveal that older bridges, which are more likely to experience higher damage states, are particularly susceptible to column damage and are not sensitivetoskewSimilarly,thepresenceofintegralabutmentsinnewerbridgessignificantlyreducesthevulnerabilityandminimizestheimpact oftheskewangleonbridgefragilityFornewbridgeswithseat-typeabutments,thebridgeskewanglehasasignificanteffectoncomponentand system fragility for both single- and two-column bent bridges Forthese subclasses,HAZUS-MHskew factors are foundto reasonably estimate theshiftinmedianvaluefragilityfromtheirstraightcounterpartsDOI:101061/(ASCE)CF1943-55090000435©2014AmericanSocietyof

Failure Analysis, Condition Assessment Technologies, and Performance Prediction of Prestressed-Concrete Cylinder Pipe: State-of-the-Art Literature Review

Abstract: Prestressed concrete cylinder pipe (PCCP) is a large-diameter and high-strength pipe used in water or wastewater transmission mains. It has been widely used in North America because of its good performance, large capacity, and cost-effective price. However, some PCCPs fail after a certain time of service because of deterioration. PCCP failures can be very significant considering the pipe size and high internal pressure. To mitigate the serious results of PCCP failures, many condition assessment technologies have been developed to inspect the pipe condition, and many models have been developed to predict the performance of the pipe. These technologies and performance prediction methods have been used as reference for decision-making in PCCP pipeline management. However, because of their limitations, there is still a strong need to improve them for better application in the future. This paper, by using three databases, presents a state-of-the-art literature review of the most commonly used condition...

CLT–Steel Hybrid System: Ductility and Overstrength Values Based on Static Pushover Analysis

Abstract: A timber-steel hybrid system, where cross-laminated timber (CLT) shear panels are used as infill in steel moment resisting frames, is analytically investigated. The proposed hybrid system combines ductile behavior of steel moment frame with lighter and stiffer CLT panels. Initial parametric study is carried out with a single-bay-single-story model using pushover analysis to investigate effect of CLT panel thickness, crushing strength, and confinement gap. Results showed that the parameters studied have a significant influence on system’s ultimate strength, ultimate drift capacity, and post-peak behavior. Subsequently, parametric studies are carried out for three-bay hybrid buildings with three-, six-, and nine-story hybrid buildings for varying panel configuration (a given gap, panel thickness, and crushing strength) values. The parameters varied and are design ductility level (limited ductility and ductile) and infill pattern. A monotonic pushover analysis was performed to develop a preliminary d...

Evaluation of Influence Factors on Crack Initiation of LTPP Resurfaced-Asphalt Pavements Using Parametric Survival Analysis

Abstract: Survival model with Weibull hazard function was used to evaluate the influence of different factors on the crack initiation of resurfaced asphalt pavement. Data from Specific Pavement Study 5 experiments of the Long Term Pavement Performance (LTPP) program were used to conduct the analysis. The initiation time of four types of cracks including alligator (fatigue) crack, longitudinal crack on wheel path, non–wheel path longitudinal crack, and transverse crack was evaluated. Analyzed factors include overlay thickness, total pavement thickness, pretreatment pavement serviceability, traffic volume, freeze index, mixture [whether reclaimed asphalt pavement (RAP) is used], and whether milling is performed before overlay. It was found that traffic level was a significant factor for all four types of cracks. High traffic level accelerated the initiation of cracking. Thick overlay delayed the initiation of cracking except for the non–wheel path longitudinal crack, which is mainly caused by poor constructio...

Experimental Study of the Steel-Concrete Connection in Hybrid Cable-Stayed Bridges

Abstract: A new steel-concrete connection with Perfo-Bond Strip (PBL) connectors for a hybrid cable-stayed bridge was adopted and introduced. Push-out tests of the PBL connectors were performed to evaluate the shear capacity of perfobond ribs in steel-concrete connections. Test results revealed that the shear strength of a perfobond rib in a twin configuration is about 80% of that of a single independent perfobond rib. To investigate the safety and reliability of the proposed connection from a practical perspective, a model test with a scale of 1:2 for the joint of the hybrid girder was carried out on site. During the test, stress distribution, crack resistance ability, and relative slip between concrete and steel were measured carefully to investigate the mechanical performance, force transmission, strength, and stiffness of the steel-concrete connection. The test results revealed that concentrated stress at the loading section in steel girders can be reduced and transferred uniformly through the joint to the concrete sections by a combined axial and shear force transmission mode with the help of bearing plate and multiple parallel perfobond ribs. The findings from the tests and analyses are considered to be of special significance to the design and construction of steel-concrete connections in hybrid cable-stayed bridges.

Simplified Models of Progressive Collapse Response and Progressive Collapse-Resisting Capacity Curve of RC Beam-Column Substructures

Abstract: Based on analysis of a progressive collapse mechanism, this paper presents a simplified model for static analysis of progressive collapse response of RC beam-column substructures under midspan point loading. The proposed model expresses the load-deflection response directly, and it consists of three stages—beam mechanism stage, transient stage, and catenary mechanism stage. In the model, the influence of the span, the sectional dimension, and the reinforcement of the beam on progressive collapse behavior of substructures can be taken into account. The proposed model is validated by experimental results in literature. Last, progressive collapse-resisting capacity curves of substructures are established based on the energy conservation principle, which establishes a foundation for progressive collapse assessment of RC frame structures.

Knowledge-Based Optimization of Building Maintenance, Repair, and Renovation Activities to Improve Facility Life Cycle Investments

Abstract: Buildings and related civil infrastructure are an important factor of production that contribute directly to the accomplishment of an organization’s mission and/or the generation of revenue. Aging, obsolescence, and general deterioration of these buildings, and their systems and components, can adversely affect the ability to accomplish a mission or generate expected revenue, thus resulting in an elevated risk profile. Maintenance, repair, and renovation (MR&R) activities, when planned effectively, can affect performance in such a way to reduce this risk. A rapidly aging infrastructure and building stock in the United States and across the world jeopardizes the ability to generate output and accomplish a mission at status quo. Moreover, rapidly expanding demands on some infrastructure will likewise make the status quo greatly inadequate in the near future. This requires two highly interrelated strategies: (1) to introduce new capabilities and capacities into the infrastructure stock to meet projec...

Defects in affordable housing projects in Klang Valley, Malaysia

Abstract: Several affordable housing programs were introduced by the government of Malaysia to achieve the objectives of several plans; however, the success of the housing programs was reduced because of reported quality problems and defects. This research aims to identify the types of defects in affordable housing and to determine what is causing the defects, so that solutions may be devised to raise the quality of housing stock in Malaysia. A questionnaire survey was distributed to 310 residents in affordable housing, located in four different regions of Klang Valley, Malaysia. The most commonly occurring defects in affordable housing were leaking pipes, total failure of water supply systems, cracking in concrete walls, faulty door knobs, and concrete walls dampness. This suggests that improvements in workmanship, use of superior materials, and changes to more customer-oriented supervision and monitoring may reduce the incidence of defects. Local conditions, such as heavy rainfall, may influence dampness,...

Experimental Analysis of the Structural Behavior of Timber-Concrete Composite Slabs made of Beech-Laminated Veneer Lumber

Abstract: Composite, timber-concrete slabs as structural floor systems for office and residential buildings, offer several technical advantages over traditional, exclusively timber floors. The connection between timber and concrete in current systems made of spruce relies on mechanical steel fasteners to transfer shear forces between the two materials. The mechanical properties of beech-laminated veneer lumber (LVL), which are higher and more reliable than spruce, allow the development of an innovative timber-concrete composite slab made of a thin beech-laminated veneer lumber plate and a concrete layer. The connection between the two materials is accomplished with notches in the timber plate instead of mechanical steel fasteners. The structural performance of this system was evaluated with a series of bending tests. The results demonstrated that this type of timber-concrete composite system was able to reach high load-carrying capacity and that the structural behavior and failure modes of the composite ele...

Development of an Integrated Method for Probabilistic Bridge-Deterioration Modeling

Abstract: Probabilistic deterioration models such as state-based and time-based models are only capable of predicting future bridge-condition ratings when a sufficient amount of condition data and reasonable data distribution are available. However, such are usually difficult to acquire from limited bridge-inspection records. As a result, these probabilistic models cannot guarantee reliable long-term prediction for each of the bridge elements concerned. To minimize this shortcoming, this paper proposes an advanced integrated method to construct workable transition probabilities for predicting long-term bridge performance. A selection process within this method automatically chooses a suitable prediction procedure for a given situation in terms of available inspection data. The backward prediction model (BPM) is also incorporated to effectively predict the bridge performance when sufficient inspection data are unavailable. Four different situations in regard to the available inspection data are predefined in this study to demonstrate the capabilities of the proposed integrated method. The outcomes show that the method can help develop an effective prediction model for various situations in terms of the quantity and distribution of available condition-rating data.

Spatial Corner Effects of Long and Narrow Multipropped Deep Excavations in Shanghai Soft Clay

Abstract: By analyzing the field data from nine metro-station pits with aspect ratios (AR) of pit length to width of 6.6–19.4 in Shanghai soft clay, this paper investigates the potential corner effects (i.e., the retaining walls near pit corners have stronger capabilities to resist deformation than those distant away as a product of spatial arching effects across the pit corners) of long and narrow multipropped metro station excavations. Contrary to the two-dimensional (2D) plane-strain assumption widely adopted in practice for analysis of a metro station excavation (i.e., deformations of the pit in which the displacements of all points along the longitudinal sides are assumed to be parallel to a given plane in the transverse direction and the values of these displacements do not depend on the distance perpendicular to the plane), seven out of the nine metro station pits exhibited apparent corner effects and only two showed plane-strain conditions. Because of the stiffening effects from the pit corners, the...

Dynamic Response of a RC Frame under Column Removal

Abstract: Under a collapse scenario, the sudden loss of support causes a dynamic response that can amplify the internal forces in the members and lead to greater damage. This study considered a one-quarter scale, 2-bay, 2-story RC frame that was axially restrained at the beam locations. The frame was loaded with dead weights, and the support under the center column was kicked out to initiate the dynamic test. The results from four dynamic tests of a reinforced concrete frame with discontinuous reinforcement under various levels of applied load are presented. The fourth drop, with a load corresponding to 42% of the design (1.2×dead load+0.5×live load), did result in a catenary action range of response. A simple single degree of freedom (SDOF) analysis showed that there is a snap-through effect, i.e., a very fine tipping point at which the structure is pushed past the compressive arch or flexural range of response into the catenary action range of response. At this point, the loads in the structure increase s...

Temperature Effects on a Box-Girder Integral-Abutment Bridge

Abstract: As part of a study to quantify temperature effects on integral-abutment box-girder bridges, field instrumentation was monitored continuously for one year on a bridge near Sacramento, California. Thermocouples were installed throughout the deck as well as over the height of the superstructure. Temperature changes were used to obtain maximum and minimum average temperatures as well as positive and negative thermal gradients. These values were compared with recommended respective temperature ranges. Strain changes at various locations were obtained by driving trucks along five load paths. These data, along with strain changes resulting from daily temperature variations, were used to validate a finite-element model using solid elements for the superstructure and springs at the abutments, in order to replicate the partial fixity of the bridge. The validated finite-element model was used to evaluate the effects that the partial fixity and temperature gradients have on the temperature stress for a typical integral-abutment bridge.

Performance-Based Design and Optimization of Buckling Restrained Knee Braced Truss Moment Frame

Abstract: A buckling restrained knee braced truss moment frame (BRKBTMF) is a novel steel structural system that combines steel trusses with buckling-restrained braces (BRBs) to form an alternative seismic force–resisting system. The combination of the steel trusses and the BRBs allows the BRKBTMF to have a large interior opening without the need to provide ductile detailing for the steel trusses. This makes the design very efficient and economical. More importantly, through the use of BRBs as the designated energy-dissipation devices, the damage is controlled within the BRBs, which can be replaced easily after the earthquake. This will drastically reduce the structural damage, repair cost, and repair time, which makes this structure more efficient and resilient toward future earthquakes. In this study, a modification of the performance-based plastic design (PBPD) procedure was derived to design the member sizes of the BRKBTMF. A parameter study was conducted by varying the inclination of BRBs to optimize t...

Statistical Analysis of Concrete Compressive Strengths for California Highway Bridges

Abstract: This investigation presents results of the statistical and probabilistic analyses of 3,269 normal weight concrete cylinder compression tests used for recently constructed highway bridges in California. A new model for in-place strength of concrete structures is proposed as a function of the specified compressive strength, the normalized 28-day cylinder strength, and age of the structure based on a realistic strength–age relation for hardened concrete. The model prediction indicates that concretes in cast-in-place bridge structures designed with specified compressive strengths of 25 MPa (3.6 ksi), 28 MPa (4.0 ksi), and 35 MPa (5.0 ksi) reach their maximum strengths at about 40 years, with approximately 98% of the maximum strength occurring during the first 10 years. Also, through significance testing on the 28-day cylinder strengths, it was established that the California Department of Transportation practice of using an expected concrete strength instead of the specified strength for seismic desig...

Variability of Compressive Strength of Concrete Cores

Abstract: A comprehensive test program was conducted on the compressive strength of concrete cores. The tests involved eight mixes of concrete. Because over 200 tests were conducted, it was possible to undertake an analysis of the concrete cores using the probabilistic treatment of strength. The present work reports a comparative study of alternative probabilistic models to describe the compressive strength of concrete cores. A large class of probability models including two-parameter Weibull, three-parameter Weibull, normal, lognormal, and gamma distributions were validated using test data. This information is useful in the theoretical description of concrete failure. Furthermore, the results were compared in terms of modified Kolmogorov-Smirnov, log-likelihood, and minimum chi-square criterion. The results suggested that none of the described probability methods are adequate for determining the variability of the compressive strength of concrete cores.

Corrugated Steel Plate Culvert Response to Service Train Loads

Abstract: This paper presents the results and conclusions of field tests under service loads that were conducted on a corrugated steel plate (CSP) railway culvert. Inductive gauges, extensometers, and accelerometers were used to monitor displacements, strains, and accelerations of this culvert, respectively. The maximum displacement and strain of the CSP railway culvert was −0.61×10−3 m and −54×10−6, respectively. The biggest displacements and strains were recorded at the culvert crown and quarter points, respectively. The maximum culvert and ballast accelerations were equal to 0.67 and 1.23 m/s2, respectively, and they did not exceed the Eurocode limit of 3.5 m/s2. On the basis of the measured displacements, a discrete Fourier transform method was implemented to determine the frequencies of this culvert. The natural frequencies of the culvert were identified (using the ambient vibration test), and they corresponded to approximately two first dominant frequencies extracted from the forced vibration tests. T...

Performance of Bridges in Liquefied Deposits during the 2010–2011 Christchurch, New Zealand, Earthquakes

Abstract: The performance of road bridges undergoing liquefaction in the foundation soils and substantial lateral spreading during the 2010–2011 Christchurch earthquakes is discussed in this paper. Three, well-documented case studies are presented in detail to illustrate the performance of bridges and their typical damage associated with lateral spreading. The short-span bridges on pile foundations have a very stiff superstructure (deck), which was a key factor in the seismic response of the bridges. It led to a characteristic deformation mechanism for all bridges involving lateral spreading-deck pinning-abutment backrotation with consequent damage to the abutment piles and slumping of the approaches. Overall, road bridges performed relatively well in the 2010–2011 earthquakes compared to other engineering structures, despite the high seismic demands including substantial liquefaction and large kinematic and inertial loads due to spreading and strong ground shaking, respectively.

Development of a Standard Data Structure for Predicting the Remaining Physical Life and Consequence of Failure of Water Pipes

Abstract: This paper presents a standard data structure for predicting the remaining physical life and consequence of failure of water pipes. Correlating the various pipe material types with the pipe life cycle, failure modes and mechanisms are crucial in defining the various parameters that affect water pipelines. Identifying and estimating the failure consequences of a pipeline are also important for risk management. A complete understanding of the pipe life cycle, failure modes and mechanisms, standard data structure to support predictive modeling, and failure consequences can be effectively combined to aid in advanced asset management of drinking water pipelines.

Experimental Evaluation of the Influence of Human-Structure Interaction for Vibration Serviceability

Abstract: The effects of human-structure interaction on the dynamic performance of occupied structures have long been observed. The inclusion of the effects of human-structure interaction is important to ensure that the dynamic response of a structure is not overestimated. Previous observations, both in service and in the laboratory, have yielded results indicating that the effects are dependent on the natural frequency of the structure, the posture of the occupants, and the mass ratio of the occupants to the structure. These results are noteworthy, but are limited in their application,because the data are sparse and are only pertinent to a specific set of characteristics identified in a given study. To examine these characteristics simultaneously and consistently, an experimental test structure was designed with variable properties to replicate a variety of configurations within a controlled setting focusing on the effects of passive occupants. Experimental modal analysis techniques were employed to both t...

Fidelity and Robustness of Detailed Micromodeling, Simplified Micromodeling, and Macromodeling Techniques for a Masonry Dome

Abstract: Understanding the damage and failure mechanisms of masonry structures can help engineers reduce catastrophic failures and fa- cilitate effective restoration and preservation of historical masonry monuments. This can be achieved through a combination of experimental and numerical studies to gain insights on the macrolevel strength-deformation behavior and microlevel defects and crack growth of masonry structures. Although experiments aid in calibration and validation of the numerical model to reduce errors and uncertainties in predictions, the success of the simulations fundamentally depends on the accuracy of the mechanical principles used to represent the heterogeneous masonry assembly. In this paper, three modeling techniques—detailed micromodeling, simplified micromodeling, and macromodeling—are investi- gated,consideringnot onlytheaccuracybutalsotherobustnessof themodelpredictions.In detailedmicromodeling, thebrickunitsandmortar joints are modeled as separate entities. In simplified micromodeling, the bricks and mortar are smeared, homogenized units bonded with zero- thicknessinterfaceelements.Inmacromodeling,themasonrycompositesaresmearedintoahomogenouscontinuum.Linearpropertiesofthese three alternative models are first calibrated by exploiting the modal parameters identified through dynamic experiments conducted on a scaled domespecimeninthelaboratory.The fidelityofthetwomicromodelingandthemacromodelingtechniquesarethenevaluatedbycomparingthe modelpredictionsagainststatic,load-to-failuretestsconductedonthesamescaledmasonrydome.Finally,therobustnessofthethreemodelsto uncertainty in theinput parameters isevaluated.DOI:10.1061/(ASCE)CF.1943-5509.0000440.©2014 American Society of CivilEngineers. Author keywords: Timbrel vault; Guastavino construction; Test-analysis correlation; Uncertainty quantification; Model calibration; Sensitivity analysis; Homogenization.

Significant Characteristics of Scheduled and Condition-Based Maintenance in Office Buildings

Abstract: Sustainability of buildings is one of the main aims in the construction industry. In achieving sustainability, maintenance of buildings and its facilities, which include planning, implementation, and outcome of maintenance activities, becomes an important criterion. This paper aims to identify the significant characteristics of scheduled and condition-based maintenance in office buildings through reviews of relevant literature and a questionnaire survey. The significance of the characteristics was identified through ranking analysis. A semistructured interview was conducted to obtain further details on the characteristics and measures to enhance efficiency of the characteristics. The findings reveal that the dominant characteristics for scheduled maintenance include quality of spare part and material, the level of labor skill and knowledge, and budget allocation for maintenance labor, whereas for condition-based maintenance, the dominant characteristics are the level of manager skill and knowledge...

Heavy Laminated Timber Frames with Rigid Three-Dimensional Beam-to-Column Connections

Abstract: This article presents the seismic performance of a timber frame with three-dimensional (3D) rigid connections The connections were made with self-tapping screws and hardwood blocks were used to support the beams The frame was designed to resist high seismic excitations with the goal of controlling the drift The moment-rotation characteristics of the connections were measured in the laboratory by applying static cyclic loads The frame made of laminated wood beams and columns, and cross-laminated lumber deck, was subjected to seismic, white noise, snapback, and sinusoidal sweep excitations The synthetic seismic excitation was designed to contain a considerable amount of energy close to the frame’s first natural frequency The structure showed no significant damage up to a peak ground acceleration of 125g Failure of the frame occurred due to shearing of the columns with a peak ground acceleration of 15g The designed structure fulfilled with current serviceability limits up to 08g

Forensic Diagnosis on Flood-Induced Bridge Failure. I: Determination of the Possible Causes of Failure

Abstract: In Taiwan, many bridges span rivers that exhibit severe channel variations in response to drastically increased flows and resulting floods caused by typhoons and storms. Flood-induced scour can undermine the effective embedment depth of bridge foundations. The Shuang-Yuan Bridge, spanning a downstream section of the Kaoping Stream, was severely damaged during Typhoon Morakot in August 2009. A qualitative investigation was conducted to determine the possible causes of this bridge collapse. Relevant hydrologic, meteorologic, structural, geotechnical, and terrain information from various sources both in written and image formats was collected, updated, and reviewed. The disaster investigation included field investigations, nondestructive inspection of bridge remnants, and investigation of structural damage of upstream river crossings, hydrologic changes, damage to training structures/embankment, riverbed profile changes, and debris during the flood event. Several inspections were applied to determine the embedment depths, positions of underwater remnants, and changes in riverbed elevation. The investigation results identified multiple possible causes of failure, including flood flows, river-bend-induced turbulent flows, and the joint effects of extended foundations and rafted wood.

Multicriteria Assessment and Prioritization of Hospital Renewal Needs

Abstract: Accurate performance assessment of building systems and subsystems (e.g., roof, boiler, windows, etc.) is essential to properly prioritize the subsystems that compete for capital renewal funding. Typically, the performance assessment of buildings has been based on physical condition alone, which is not sufficient for specialized facilities such as hospitals. This paper introduces a practical multicriteria performance assessment framework for hospitals with four unique features: (1) it divides the hospital into three zones with different characteristics and importance: clinical, nursing, and support; (2) it assesses the performance of hospital subsystems, considering four key performance indicators: condition, level of service, sustainability, and risk; (3) it assesses the service quality (temperature, lighting, noise, etc.) within various indoor spaces and accordingly determines the level of service of related subsystems; and (4) it incorporates a simple all-on-site visual inspection application t...

Seismic Vulnerability of Older Braced Frames

Abstract: Concentrically braced frames (CBFs) are broadly used as lateral-load resisting systems in buildings throughout the United States. Current state-of-the-practice is the use of special concentrically braced frames (SCBFs) where ductility under seismic loading is necessary. Prior to modern seismic codes, braced frames were designed without ductile detailing. Here these systems are termed nonseismic braced frames (NCBFs), which are essentially CBFs designed with no special detailing requirements. These may comply with older code requirements in high-seismicity regions or current code requirements in low-seismicity regions. Many are still in service throughout the United States. Prior research has focused on SCBFs, which has improved their seismic performance. In comparison, there is significant uncertainty regarding the seismic performance of NCBFs and they may be vulnerable to collapse. A study was conducted to evaluate this vulnerability. At the start, a pilot experimental test of NCBFs was conducted...

Practical Modeling for Wind Load Paths in a Realistic Light-Frame Wood House

Abstract: Theobjectiveofthisstudywastodevelopandvalidatepracticalmodelingmethodsforinvestigatingloadpathsandsystembehavior inarealisticlight-framewoodstructure.Themodelingmethodswerevalidatedagainstfull-scaletestsonsubassembliesandanL-shapedhouse. The modeloftheL-shapedhousewasthenmodifiedandusedtoinvestigatetheeffectsof reentrantcorners,wall openings,andgable-endretro- fitsonsystembehaviorandloadpaths.Resultsshowedthattheeffectsofaddingreentrantcornersandwallopeningsonupliftloaddistributions were dependenton theorientation of the trusses with respectto thewalls. Openings addedto walls parallel tothe trusses havethe leasteffect on loadscarriedbytheremainingwallsinthebuilding.Varyingreentrantcornerdimensionsunderdesignwindloadscausedincreasingdegreesof torsion throughout the house depending on the relative location and stiffness of the in-plane walls (parallel to the wind loads) and the assumed direction of the wind loads. Balancing the stiffness of the walls on either side of the house with the largest reentrant corner helped to decrease torsion in the structure under lateral loads. Finally, although previous full-scale tests on gable-end sections verified the effectiveness of the gable-end retrofit that was recently adopted into recent Florida building code, questions remained about the effects of the retrofit on torsion in a full building. The current study found that adding the gable-end retrofits to the L-shaped house did not cause additional torsion. DOI: 10.1061/(ASCE)CF.1943-5509.0000448. © 2014 American Society of Civil Engineers. Author keywords: System behavior; Reentrant corners; Wall openings; Gable-end retrofits.

Seasonal Thermal Cracking of Concrete Dams in Northern Regions

Abstract: In several northern regions around the world, concrete dams are subjected to severe seasonal temperature variations, with up to 75°C changes from summer to winter. Those variations contribute to the degradation of the stiffness, strength, and durability of concrete dams. Thermal stresses and related concrete cracking also need to be evaluated to ensure the structural stability of the dam and to define the initial conditions for unusual or extreme load combinations, such as floods and earthquakes. This paper presents finite-element modeling procedures for assessing the thermomechanical behaviors of concrete dams. The stress relaxation and mechanical properties that depend on the temperature of the concrete are first investigated by considering the thermomechanical responses of simple notched beam models. Heat transfer and thermomechanical analyses are then presented for a 31-m concrete gravity dam and a 214-m multiple arch dam located in Canada. It is shown that temperature-dependent material prope...

Experimental and Numerical Investigations of Groove Connections for a Novel Timber-Concrete-Composite System

Abstract: The development of hybrid structures is constantly being pushed forward because of the need for more efficient components that incorporate multiple functions. Structural requirements lead to state-of-the-art timber-concrete-composite (TCC) floor systems, which consist of a concrete layer on top of timber beams or decks. In bending, the TCC concrete layer is in compression and the timber is in tension. When multifunctionality requirements such as building physics or fire protection are added, other solutions of the structural form of hybrid systems can emerge that challenge common engineering conceptions. This paper presents research on the connection system of a novel TCC setup that integrates thermal and fire protection functionality, in which timber beams are placed at the top and a concrete layer at the bottom. The results from full-scale bending tests, and shear and tension tests on a subsection of the system, show that the grooves cut into the timber beams transmit the shear forces and sufficiently connect the concrete deck vertically to the timber. Subsequently, the structural behavior was numerically modeled and the agreement between experimental and numerical results allow for the validated model to be used for geometric optimizations, and predicting the performance of optimized systems.