Contraction Joints Research Articles

The effects of reservoir geometry on the seismic response of gravity dams

AbstractConventional seismic analysis of gravity dams assumes that the behaviour of the dam–water–soil system can be represented using a 2‐D model since dam vertical contraction joints between blocks allow them to vibrate independently from each other. The 2‐D model assumes the reservoir to be infinite and of constant width, which is not true for certain types of reservoirs. In this paper, a boundary element method (BEM) model in the frequency domain is used to investigate the influence of the reservoir geometry on the hydrodynamic dam response. Important conceptual conclusions about the dam–reservoir system behaviour are obtained using this model. The results show that the reservoir shape influences the seismic response of the dam, making it necessary to account for 3‐D effects in order to obtain accurate results. In particular, the 3‐D pressure and displacement responses can be substantially larger than those computed with the 2‐D model. Copyright © 2007 John Wiley & Sons, Ltd.

Experimental study of dynamic damage of an arch dam

AbstractSeismic responses of a 292‐m high arch dam were studied by experiment on a shaking table. The model system included the arch dam with contraction joints, a part of a reservoir, and a partial foundation with a topographic feature near the dam. Potential rock wedges on the abutments and the mechanical properties including uplift on the kinematic planes were carefully simulated. A damping boundary consisting of a viscous liquid was introduced to simulate the effect of dynamic energy emission to far field, which made the dynamic interaction between the dam and the foundation be adequately represented in the model test of an arch dam system. Dynamic responses of the arch dam system under a sequence of seismic loadings in increasing strength were examined. Eleven cracks or overstresses on the model dam due to the earthquake excitations were observed, and consequently, its natural frequency dropped by about 14%, but the model dam was stable under the hydrostatic load of the impounded water after the test. Copyright © 2006 John Wiley & Sons, Ltd.

Dynamic Solution Code for Structural Analysis upon Joint Element

The analysis of large structures mostly requires a complete three dimensional finite element discretization. Stability of such structures includes not only the stability of structure itself but also that of foundation as well as interconnection elements. The general instability of a structure may be affected by two aspects, firstly, an inappropriate preliminary classical design of the structure and inadequate control over the geometry and quality of the materials used for construction. Secondary, the foundation rock and abutments may contain a number of faults and joints which may be unfavorable to stability of the structure. Therefore it is necessary to consider appropriately the influence of interaction between the structure, foundation and abutments under static and dynamic loads. from construction point of view some of the structures such arch dams are divided into vertical blocks, which are separated by vertical joints which are grouted at the later stage .Since the behavior of such and many other structures whose have contraction joints under static and dynamic loads depends largely on those joints, therefore, the presence of structural codes that can recommend the appropriate specifications on modeling these joints, seems to be necessary. The present study contribution deals with the development of three dimensional finite element software including interfacial behavior of joints between different substructures and interaction behavior of structure and foundation to evaluate the safety of the structure subjected to static and dynamic loads. The developed software is verified upon different points of view and the results are in agreement with experiments.

Forces on Plunge Pool Slabs: Influence of Joints Location and Width

The hydrodynamic pressures due to jets impinging on plunge pools must be taken into account in the stability design of pool floor concrete slabs. The contraction joints between slabs are normally sealed with waterstops, which prevent the transmission to the foundation of the pressures applied on the upper faces of the slabs. However, a waterstop failure will allow pressure transmission to the foundation, inducing uplift forces on the slabs. The use of open joints might also become a feasible solution for the lining of plunge pool floors if the pressure field that develops around each slab could be adequately evaluated. This paper presents an analytical model and experimental research developed to assess the forces on plunge pool slabs, considering either open or closed. The influence of the relative width of the contraction joints and the joint between the slabs and the foundation is analyzed. The mean value and standard deviation of the hydrodynamic vertical force are determined based on point pressure measurements, and their relative importance is discussed.

Experimental study of seismic overloading of large arch dam

A dynamic overloading model test has been carried out on a shaking table for an arch dam of 278 m in height to investigate its behaviours under strong earthquake. The model system included the arch dam with contraction joints, part of reservoir, partial foundation rock with topographic feature near the dam. A damping boundary consisting of viscous liquid has been used to simulate the effect of dynamic energy emission to far field, which made the dynamic interaction between dam and foundation in model arch dam system be represented properly. Three sets of different seismic waves of design level have been used as the input to investigate the difference in the responses of arch dam. Artificial waves of different levels have been used to verify the behaviours of arch dam under seismic overloading. Since the opening of joints during strong earthquake reduced the response acceleration and tensile arch stress, cantilever stress on downstream face exceeded the tensile strength first for the model dam. And the arch dam responded in a non-linear way when input seismic load increased. Some cracks appeared near abutments, and the damage made the natural frequency of arch dam to drop obviously, but the static function did not seem to change for the model tested. Copyright © 2005 John Wiley & Sons, Ltd.

Evaluation of Slab Shape Under Controlled Environmental Conditions

During the curing of Portland cement concrete (PCC) pavements, temperature and moisture gradients in the concrete cause pavement slabs to deform from their initial as-placed shape. Daily and seasonal environmental cycling can then cause the slabs to expand and contract horizontally with changes in average temperature and moisture conditions, and curl and warp vertically as temperature and moisture gradients change through the slab depth. This article reports on a study that evaluated slab shape under controlled environmental conditions. In the study, two 3.66 m (12 ft) wide, by 13.72 m (45 ft) long, by 254 mm (10 in) thick concrete pavements were constructed in the Ohio Accelerated Pavement Loading Facility (APLF). Transverse contraction joints were placed at 4.57 m (15 ft) intervals to create three contiguous 4.57 m (15 ft) long slabs in each pavement. Dowel bars were added to the joints in one pavement, and the other pavement was left undoweled. Results demonstrated large upward vertical deformations along the slab edges early in the curing cycle, and these deformations continued to increase throughout the duration of the tests. The slightly smaller vertical movements observed in the doweled pavement were attributed to the presence of the dowel bars. The authors conclude that by restraining joint movement, dowel bars transferred load to adjacent slabs and reduced slab deformation. They note that forces in the dowel bars were smaller than expected from reports on previous investigations, particularly during the curing process. When modeling PCC pavements, loss of support from the base should be considered as dead and live load stresses are generated in cantilevered slabs.

Pothole erosion of a dissected Lake‐shore platform in Peat, Loch More, Halkirk, Caithness

An unusual combination of environmental factors has brought about the excavation of a series of classical cauldron‐shaped potholes in a dissected lake‐shore platform of peat on the shore of Loch More, Halkirk, Caithness. The potholes have both been eroded by, and now contain, ‘cobbles’ of peat. Some potholes are obviously currently active during periods of heavy rain, while others are abandoned or at least less active, being filled with a growing layer of grass. The platform has been deeply dissected by water erosion along contraction joints which formed as the peat dried out ('nagging') and it now generally resembles a karst‐like miniature ‘bad‐lands’ topography with small ‘mesas’ and ‘buttes’.

Characterization of highway traffic noise generated by rigid pavement contraction joints

Contraction joints in rigid (concrete) pavements are required to permit expansion of each monolithic section of roadway. At higher speeds, the major source of highway noise is attributed to vehicle tire/roadway interaction. Current concerns about limiting the impact of highway traffic noise has forced transportation agencies to consider strategies to control noise generated by tire/roadway interaction. Within this work the difference in noise generated by 1/4‐ vs 3/8‐in. joint widths is conducted. The study focuses on passenger vehicles including a sedan and a light duty van/truck. Both vehicle in‐cabin and roadside noise levels are measured for vehicle speeds of 50, 60, and 70 miles per hour. For the sedan, the minimum and maximum observed in‐cabin differences were determined to be 1.08 and 1.82 dB(A), respectively. Minimum and maximum observed roadside differences are 1.19 and 2.58 dB(A), respectively. Van tests resulted in minimum and maximum observed in‐cabin differences of 0.60 and 1.09 dB(A) and minimum and maximum observed roadside differences of 1.05 and 3.18 dB(A), respectively. This paper contains details of reference standards, test methods, and the results obtained.

Three-dimensional analysis of concrete dams including contraction joint non-linearity

In this study, a non-linear joint element was developed to represent the dynamic behaviour of vertical contraction joints in concrete dams. This element can be used to describe partial joint opening and closing as well as tangential displacement. Joint opening and closure are governed by normal stress criteria; tangential displacement is governed by the Mohr–Coulomb friction criterion. This joint model was incorporated into a non-linear finite element analysis program for concrete dams. Validation of the model was done on the Big Tujunga arch dam. The program was then used to study the effect of joint opening/closing on the behaviour of the Outardes 3 gravity dam where potential joint movement was identified experimentally. The program can carry out energy analyses to evaluate the amount of energy dissipated in contraction joints during seismic events, in addition to dynamic and thermal analyses of concrete dams.

Investigation of Joints Behavior in Seismic Response of Arch Dams

There has been extensive research to examine the effects of contraction joints opening in the nonlinear seismic response of arch dams. However, there has been less attention on the effects of perimetral joint on the response. In this study, a special finite element program is developed, that is described and verified initially. Based on this program, the nonlinear dynamic behavior of a typical thin arch dam is studied. The perimetral joint, as well as, contraction joints are included in the nonlinear cases analyzed. It is shown that the distributions of the maximum tensile stresses are very sensitive to the properties used for the joints. Moreover, the modified joint model proposed for the modeling of perimetral joint is found to be less sensitive and very effective in seismic analysis of concrete arch dams.

Testing and Performance Evaluation of Ultrathin Whitetopping Pavements at Spirit of St. Louis Airport

To obtain a better understanding of ultrathin whitetopping (UTW) pavement behavior under traffic loading and environmental effects and to collect data for calibration and development of a mechanistic design procedure, a UTW test pavement was constructed, instrumented, and load tested. The UTW pavement test section is located at the Spirit of St. Louis Airport, a general aviation airport in Chesterfield, Missouri, and is designed to carry a light aircraft load of 56 kN. The results of analyses conducted on this test pavement and its performance to date are described. The UTW test section was constructed in February 1995 and consisted of six slabs with dimensions of 1.3 × 1.3 m and a design slab thickness of 89 mm. The load testing was conducted in May and September 1995. Load-induced strains, temperature distribution, and surface profiles were measured at different locations and at different times. Pavement core samples were also taken and subjected to laboratory testing. It was observed from the evaluation that ( a) there was very little vertical slab movement in spite of the temperature differential in the slabs, ( b) there was no apparent change in load-induced strains (stresses) with temperature changes, ( c) pavement exhibited high load transfer efficiencies across contraction joints, and ( d) an interface shear strength of 689 kPa was achieved by the commonly used technique for asphalt surface preparation, milling and cleaning. A recent performance review of this pavement also showed that it has performed extremely well after over 6 years in service. Of the 11620 m2 of UTW pavements (about 72,000 UTW panels), only 18 panels have cracked.

A discrete crack joint model for nonlinear dynamic analysis of concrete arch dam

Concrete arch dams are generally constructed of massive plain concrete with almost no tensile resistance. To control tensile forces due to concrete shrinkage, temperature variations and for construction facilitation, arch dams are built in cantilever monoliths separated by vertical contraction joints. Earlier studies show that the modeling of such joints has significant influence on the seismic safety evaluation of arch dams. This fact is due to the tensile and shear failures of joints causing a redistribution of internal forces during and after a big earthquake. In the present study, a nonlinear joint element model with a coupled shear–tensile behavior for realistic finite element analysis of dam–reservoir system is presented. Reservoir upstream radiation, and bottom partial absorption of acoustic waves, as well as water compressibility are considered. The model when applied to simpler cases solved by other workers shows good performances. However, it is much more useful to solve problems not considered so far, e.g., shear keys behavior, joint damages, etc. The model could be employed effectively and conveniently for earthquake safety evaluation of arch dams in highly active seismic regions.

Experimental Investigations into Seismic Failure of High Arch Dams

A series of dynamic experiments for 20 models of high arch dams were recently performed on a shaking table, with the water ignored. The experimental results show that the seismic response and final failure of high arch dams are significantly affected by the contraction joints depending upon the contact materials, the motion of the surfaces, and other factors. The instantaneous acceleration that occurs when the first tensile crack appears is employed very tentatively as the parameter to quantitatively estimate the overload capacity of high arch dams from small-scale models. The final failure patterns of the model dams also are reported and discussed. From the results of the experimental investigation, a new idea is suggested, which is to use the contraction joints to control the response of a high arch dam and thereby to control the level of the seismic damage.

RESONANT FREQUENCY OF CONCRETE ARCH DAM EVALUATED FROM OBSERVATIONAL IN-SITU RECORDS AND EFFECTS OF CONTRACTION JOINTS ON THESE FEATURES

コンクリートダムの固有振動数は, ダムの地震応答に及ぼす最も重要な値の一つである. 2つのアーチダムを対象に, ダムの上部と最低部での地震観測記録や常時微動計測記録, 起振実験の共振曲線から固有振動数を算出し, ダムの貯水位や振動レベルと固有振動数の関係について示す. ある貯水位以下になると貯水位が高い場合の固有振動数より低振動数側の固有振動数になることや, 比較的強振動時には弱振動時にくらべ固有振動数が低振動数側になり, これらはブロックジョイントの影響によるものであることを述べる.

A method for coupled arch dam-foundation-reservoir seismic behaviour analysis

This paper presents a method for coupled arch dam-foundation-reservoir seismic behaviour analysis. The dam is discretized by finite elements (FE) and the foundation and reservoir are discretized by boundary elements (BE). The opening of contraction joints and the spatial variability of the seismic action is taken into account. The study of Pacoima dam by this method is also presented. The computed results show that no cracks were to be expected due to the vibrations induced during the Feb. 9, 1971 San Fernando earthquake.

Selecting Concrete Pavement Joint Sealants. I: Proposed Test Protocol

Sealants used to seal the transverse contraction joints used in joining concrete highway sections without dowels must be flexible enough to withstand excessive conditions such as large temperature fluctuations, severe pavement deflection due to heavy truck traffic, and prolonged moisture exposure. Choosing the most appropriate sealant for the expected service condition from the wide variety of sealants available on the market today can be a daunting task. In Part I of this paper, a comprehensive test protocol that correlates sealant viscoelastic properties with the sealant resistance to deflection is presented. It is proposed that the selection of a sealant should be based on a complete evaluation consisting of three test procedures: (1) the ASTM C794 adhesion-in-peel test to assess concrete/sealant adhesion; (2) dynamic mechanical analysis (DMA) to evaluate sealant flexibility by determining the glass transition temperature, Tg; and (3) the shear fatigue test developed by the writers to analyze sealant performance when subjected to severe pavement deflection in combination with various environmental conditions. Part II of this paper will present the results of testing and comparison of two polyurethane joint sealants using this proposed test protocol.

Modelling of contraction joint and shear sliding effects on earthquake response of arch dams

In an arch dam, adjacent monoliths separated by vertical contraction joints may move relative to each other during an earthquake, resulting in the gradual opening and closing and possible shear movement at the joint surfaces. This paper presents the formulation of a joint constitutive model for a zero-thickness joint element that can simulate both the opening and closing and shear sliding behaviour, as well as the non-linear shear key effects of the joint. The proposed joint element has been implemented in the concrete arch dam finite element analysis program ADAP-88. The response of a typical arch dam subjected to earthquake ground motion is presented to demonstrate the capability of the proposed joint model. Results from a parametric study carried out to study the sensitivity of the response to the joint properties are discussed. The joint parameters considered in the parametric study include apparent cohesion, friction coefficient, and whether the joint has beveled or unbeveled shear key, or the joint is unrestrained in shear sliding. The analysis results show that joint opening and shear slippage at the contraction joints can have significant effects on the response of an arch dam. © 1998 John Wiley & Sons, Ltd.

Investigation of Joint Spalling on Concrete Runway

During 2 days in October 1994, 4-month-old concrete on a runway developed extensive spalling along transverse joints. Damage was extensive, limited to transverse joints; was located in trafficked areas only; and developed only after the beginning of freezing weather. An investigation into possible causes of this spalling concluded that the concrete probably developed a network of microcracks from premature loading before the concrete had gained adequate strength. The concrete continued to gain strength with time and these cracks were not sufficient to cause spalling. Later, moisture accumulated in the cracks froze, which propagated the original cracking to free the spall fragments. The most likely cause of the original inadequate strength gain was probably poor curing of the concrete in the vicinity of the transverse joints caused by damage to the curing compound membrane during initial sawing of transverse contraction joints. Alternate explanations of the damage were unable to account for all of the observed characteristics of the damage. The remaining concrete is essentially sound, and permanent repair of the runway requires only patching of the spalled areas.

Pavement Pressure Generation: Neglected Aspect of Jointed Pavement Behavior

A number of recent rigid pavement research reports and papers and new pavement research projects either ignore effects of contraction joint behavior on the generation of pavement pressure or recommend the retention of high pavement pressures to protect contraction joints. In either case, research methods appear to be inappropriate, and conclusions suspect or counterproductive. It also appears that some researchers have completely lost sight of one of the primary reasons for sealing and resealing contraction joints in the first place. In addition, these reports either ignore entirely or significantly underestimate the effects that generating pavement pressure can have on the integrity of bridges that abut such pavements. Consequently, pavement maintenance engineers who uncritically implement the recommendations given in some of these reports and papers may, during the extreme heat of some distant summer, find themselves dismayed by structures (pavements and bridges) subject to destructive pressures and stresses, widespread structural damage, massive repair costs, restrictive traffic flow at structure repair sites, vehicular accidents, and the personal injuries that usually accompany such restrictions. Based on a brief introductory description of the pavement pressure generation phenomenon, a critique of some of the statements and recommendations given in these reports is provided. Recommendations for basic replicable research to clarify this phenomenon, and for subsequently qualifying future pavement joint research with respect to the effect of design, maintenance, and environmental factors on pavement pressure levels, are also provided. Ultimately, such pressure-generation-focused research will give less subjective and more reliable direction for achieving cost-effective structural designs, more durable structures, more effective maintenance practices, and a safer, more dependable highway environment.

The Great Unsealing: A Perspective on Portland Cement Concrete Joint Sealing

The general mission of most transportation agencies is to ensure a customer focus in the development and operation of a safe and efficient transportation system. The customers desire comfort, convenience, safety, and cost-effectiveness in a transportation system. Agency research must have the objectives of addressing customer-related issues and measuring benefits of importance to them. Accordingly, any joint and sealant research must answer the questions, Why do we seal? and Is it cost-effective? Joint and sealant studies of portland cement concrete (PCC) pavements must address whether joint sealing enhances total pavement performance and is cost-effective, and, if so, what sealant system should be used. The Wisconsin Department of Transportation (WisDOT) has been studying the effect of PCC joint/crack sealing on total pavement performance for 50 years. By 1967 there was substantial documentation that filling and refilling of contraction joints had no beneficial effect on pavement performance. By 1984, it was concluded that pavements with unsealed joints had better overall performance (distress, ride, materials integrity) than pavements with sealed joints. In 1990, WisDOT passed a policy eliminating all PCC joint sealing, in new construction and maintenance. This "no-seal" policy has saved Wisconsin $6,000,000 annually with no loss in pavement performance and with increased customer safety and convenience. The entire PCC sealing issue is beginning to be addressed at the national level, ensuring no false assumptions and with the customer’s needs in view.