Outline and Evaluate Msm Essay Example

Outline and Evaluate Msm Essay Example Outline and Evaluate Msm Essay Outline and Evaluate Msm Essay Psychology Outline and evaluate the multi-store model The MSM was created by Atkinson and Shiffrin  (1968) who suggested that memory was comprised of three separate stores. They were; sensory memory, short term memory and long term memory. The model shows how information is transferred between the three stores. The model simply shows that when your are given information of environmental stimuli it will enter your sensory memory and only if you pay attention will it enter your short term memory, which has a capacity of 7+/- 2 bits of information. The information can last up to 18 seconds, without rehearsal. STM is encoded mainly acoustically, however sometimes it is done visually. If maintenance rehearsal takes place it will remain in STM or be forgotten due to displacement or decay. Elaborative rehearsal will transfer information into LTM which has unlimited capacity and can last a lifetime. LTM is encoded mainly semantically. The retrieval of information from LTM to STM can happen when needed. This model is a linear model because the information just passes through the model one way. A particular strength of this model is that it is high in ecologically validity and therefore can be applied to everyday life. A good example is the case study of H. M. who had brain surgery to cure severe epilepsy but this resulted in the inability to transfer information from STM to LTM so that he could not form long term memories, supporting the concept that the MSM is not a unitary model. Another example is the lab experiment of Glanzer and Cuntiz (1966) who found that participants who were asked to remember lists of words could remember the first and last few words but the ones in the middle were more difficult. This would show that the first words in the list have been stored in LTM whereas the last words are still in STM. A weakness of this model is that the scientific evidence which supports this model lacks validity because it is carried out as a lab experiment. This is an artificial environment and the participants have to remember information which isn’t important to remember in everyday life e. g. trigrams. Another weakness of this model is that it is a much too simply explained because it explains STM and LTM however hardly describes them as fixed structures and does not take into account that there are different types of them e. g. for LTM the different types of structures are procedural or episodic.

Martha essays

Martha essays Marthas Vineyard which was once a deaf community has now became a resort spot for people to get away from their daily lives and enjoy the ocean, houses and beautiful surroundings. The year round population is about fifteen- thousand. During the summer months the population swells to almost one- hundred thousand and about twenty-five thousand each every day. In 1835 a man named John Wesley, a preacher, held camp meetings outside. This camp meeting was only one of one-hundred different revivals that were in an outdoor setting at the time. These meetings were held because the population of people who were mostly puritans were losing faith in God and the meaning of faith itself. The camp meetings became yearly events that caused the population of Marthas Vineyard to rapidly increase. So it is thought today that the new industry on Marthas Vineyard was God sent. The revivals became less spiritual and more recreational. The beautiful Victorian style houses that now cover the grounds of Marthas Vineyard were once tents that housed people for the revivals. This city where all of the revivals took place was Cottage City, and is now known as Oak Bluffs. It is now a historic site for visitors to come and visit. But that is only part of what Marthas Vineyard was once like. Marthas Vineyard was once known as a deaf utopia. The gene of deafness traces back to the early settlers who carried the gene over to the island. Jonathan Lambert was the first known deaf person and that was in the year of 1694. There was a census that was taken in the nineteenth century that measured the extent of deafness. There were two families in 1817 with deaf children, that was a total of seven deaf. A few years later in 1827 there was a total of eleven deaf. By the year of 1880 the town of Chilmark had nineteen deaf in...

5 questions Assignment Example | Topics and Well Written Essays - 1000 words

5 questions - Assignment Example caused by physical factors such as exercise, hereditary and environmental factors such as radiation, pollution and climatic changes and personality traits. In addition, socio-economical factors in a cultural context that gives the human being the ability to interact communicate and position presented in the society such as education, wealth and the place of residence. However, nutrition factors or metabolic factors determine the rate human growth and development in the form of physical and cognitive characteristics. In addition, technology development plays a crucial role in the modern human development in the manner in which human beings acquire and control other factors such as environmental pollution, hereditary factors as well as social factors such as occupation (Rubenstein & Rakic, 2013). 2) The description of the divisions and systems of the mammalian nervous system, e.g. the central nervous system (areas of the brain, spinal cord) and peripheral nervous systems and their respective function (s) The gross organization of the Nervous System is divided into two divisions, the peripheral and the central nervous and their respective subdivisions both in functions and architecture. As single unit, the mammalian nervous system is responsible for the production, control as well as guidance on all mammalian actions, thoughts, and responses to their daily activities. However, each division and system is differentiated by different architecture and function. The peripheral nervous system division consists of the nerves connected directly to the mammalian skin, muscles, body organs as well as blood vessels excluding those nerves that are attached to the skull and the spinal column (Rubenstein & Rakic, 2013). Peripheral nervous system divisions include the somatic nervous system and automatic nervous system. Somatic nervous system is further subdivided into afferent and efferent nerve fibers responsible for mammalian physical sensation and voluntary movements.

What to do Being a city manager Essay Example | Topics and Well Written Essays - 500 words

What to do Being a city manager - Essay Example Being a city manager I have been designated with all important tasks of maintaining the society. In order to achieve success in my course of action I have to consider many responsibilities that I owe to my community. State legislature is passing a bill which is intended to improve the society as a whole and decrease the underage drinking which can cause damage to the whole society. Having been provided with the situation I have limited options to select from in order to enact the bill implemented by the state. With less resources to avail from I have to decide on as to whom I should depend on. Firstly I would gather a meeting of the local councils in order to aware them of the situation that the city is currently going through. It is then that a proper agenda would be formed with the help of the advice that I would receive from my councils. Police department can only excel if I am provided with the resource of money so I can expand the police force of the community which can further keep a check on the underage drinking habits. For this program to be implemented I would advertise for volunteers who would like to keep a check on the problem which our society is currently facing. These volunteers can work for free so that underage drinking can be prohibited in the community. The current line of police officers can be designated the job of checking on bars and restaurants with feasible timings and timetable. These police officers can be assured of future perks and benefits that they would be provided for their hard work.

The United States Patriot Act Essay Example | Topics and Well Written Essays - 1750 words

The United States Patriot Act - Essay Example The PATRIOT Act was enacted to protect US citizens by augmenting the tools by which law enforcement agencies fight crime and improves communication capabilities between these government agencies. In spite of the prevailing majority opinion, the PATRIOT Act protects, rather than degrades, civil liberties. The name of the act, the USA PATRIOT Act, is a shortened acronym for Uniting and Strengthening America by Providing Appropriate Tools Required to Intercept and Obstruct Terrorism. According to the Justice Department, the PATRIOT Act gives support to and encourages enhanced sharing of information among various law enforcement agencies at the local, state and federal levels. In addition, this law assists law enforcement in their efforts to â€Å"connect the dots† from a wider scope of agencies when assembling evidence so as to â€Å"develop a complete picture† regarding possible threats from terrorists. By enabling more fluid communications between the various agencies, information regarding a particular suspect can be matched up faster, often automatically by computer database, and more accurately identified. This assists in increasing the safety of citizens both by removing dangerous suspects from the general population before they are able to cause serious trouble and by ensuring innocent citizens are cleared and released in a timely and efficient manner if or when mistakes are made. Communications is the focus of the other major element of the act as well. The Act allows law enforcement officials more latitude when attempting to intercept transmissions of suspected terrorist’s discussions via electronic surveillance (Ward, 2002). This is not a blanket license for law enforcement to listen to anyone’s line based upon a simple whim or roll of the dice, but is instead intended to help investigators trace suspicious person’s through their more intimate and therefore

Fashion Channel Essay Example for Free

Fashion Channel Essay Analysis Following Rosewood through this case study we have seen the company come to a crossroads. The company had to redefine itself to stay relevant in an evolving space. Rosewood had a reputation for managing uniquely distinctive properties without widespread corporate brand name awareness. Each individual property enjoyed vast success in particular from repeat guests who mostly stayed at only one of their distinctive properties in their growing portfolio. Now the company is looking to the future and specifically evaluating whether or not to incorporate the Rosewood brand into the name of each hotel. Rosewood’s senior management is engaging several tools to make their decision. Implementing this new strategy could lead to a bright future or spell disaster. Pros and cons of Rosewood moving to a corporate brand What is branding? According to Entrepreneur magazine â€Å"The marketing practice of creating a name, symbol or design that identifies and differentiates a product from other products.† Creating a corporate brand can come with positive and negatives. Rosewood’s objective will be to leave an imprint that no one else can leave and to create magic moments that their guests will never forget. Such as when the guest goes down memory lane years later after their stay, they will recall the positively outrageous service, the amenities, the food and the atmosphere created by Rosewood. No other hotel will duplicate what they experienced at their properties. Another positive to branding, Rosewood will create standards to measure the overall performance of all their properties. Such as curb appeal, beautiful landscaping, manicured green grass, flowers in season, to beautiful shrubs and trees. Additionally, as the guest arrives the people become part of the standard set, from the doorman, to the desk clerk, to the bellman, to housekeeping, to the engineering team that keeps the building and room temperature comfortable. This is where Rosewood can benefit from differentiation and drive performance. For that reason Jack Welch states in a World Press article, â€Å"Companies win when their managers make a clear and meaningful distinction between top- and bottom-performing businesses and people, when they cultivate the strong and cull the weak†. Some of Rosewood’s property managers, as mentioned in Harvard Business Review:  Rosewood Hotels and Resorts: Branding to increase customer profitability and lifetime value, many had â€Å"mixed feelings† about moving to a corporate brand. When you are measured against other hotels there is only so much room at the top. Naturally, there will some managers that will be asked to â€Å"ship up or ship out†. Thus, the upside is each hotel pushes each other to be the best they can be. Finally, the guest could anticipate what experience they will have at each Rosewood if they moved to a uniform brand. On the other hand, the down side or cons of moving to a uniform brand for Rosewood could be that data gathered from properties could be skewed or demographic information could not apply to all hotels across the brand. According to Phillip Kotler in A Framework for Marketing and Management â€Å"The data collection phase of marketing research is generally the most expensive and the most prone to error† (p.39). Also, some management after differentiation is established and measured could be dismissed if their hotel is at the bottom. Finally, another con could be that some management and employees are not good team players and are not able to uphold the standards charted by management. Customer Lifetime Value Calculator Using a tool like the Customer Lifetime value calculator can be helpful to Rosewood management as they crunch the numbers. This tool helps management take quantitative information and funnel it down to several outcomes. However, garbage in garbage out must be considered here. The CLTV is only as good as the information provided. If one Rosewood hotel provides flawed information or has not collected the data properly, the assumptions arrived to by the CLTV are not accurate. Perhaps as JWMI 518 W2, L2 states â€Å"The best approach is often to make use of both qualitative and quantitative research†. This approach considers the ever changing market conditions, tangibles and intangibles contained within qualitative and quantitative research. They are both valuable and have their place. Finally, within all the data and assumptions gained from the CLTV, there is one factor not considered. The relationship factor. In order to carry out the legendary service brand Rosewood wants to create, the most critical factor the team should be focused on is building relationships. The data, the CLTV, the amenities and a uniform brand all revolves around the staff building meaningful relationships with the guests. The standardized expectation of  how the guests are served is the most important ingredient and the CLTV does not factor this into the equation. According to INC Magazine, â€Å"The truth is that entrepreneurs too often get caught up in the details of the kinds of products or services they are selling to notice how critical it is to build relationships not just with your customers, but also with your vendors, employees and–gasp–even your competitors. Without strong relationships, it is impossible to have success as a business owner, Recommendation My recommendation is that Rosewood should move to branding their hotels using the Rosewood brand immediately. Without setting standard foundations the guest will not know what to anticipate. Rosewood could use standardized data to help anticipate the needs of the guest before they even asked. Also, creating a uniform brand will help everyone come together as one team. When you are a consummate team player you elevate the performance of everyone around them and then there is no limit to what you can do as a team. When Rosewood has everyone on the same page going in the same direction they can create a wow factor the guest will be telling the world about. To most of the world, getting good service is common versus giving positively outrageous service is uncommon. Having a satisfied customer is common versus taking that satisfied customer exceeding his or her expectations and then taking the service one percent beyond that now Rosewood can create a raving fan that is uncommon. References Entrepreneur Magazine, (2013) http://www.entrepreneur.com/encyclopedia/branding Harvard Business Publishing, (2007), Rosewood Hotels and Resorts: Branding to increase customer profitability and lifetime value, P. 5 INC. (2013) http://www.inc.com/guides/201101/how-to-build-better-business-relationships.html Kotler, Chapter 3: Collecting Information and Forecasting Demand, P.39 World Press, (2012) http://frrl.wordpress.com/2009/10/31/jack-welch-on-differentiation-or-making-winners-out-of-everyone/

Concrete Stitches In Segmental Prestressed Concrete Bridges

Concrete Stitches In Segmental Prestressed Concrete Bridges The in-situ concrete stitches of a segmental prestressed concrete bridge are locations of potential weakness for the entire bridge deck but relatively little work has been carried out in this area. In the current practice, these in-situ stitches are usually designed to be capable of sustaining considerable sagging moment but only minimal hogging moment. Therefore, failure of these joints is possible under exceptional circumstances when the hogging moment is high, which may potentially trigger a progressive collapse. In the light of this, an extensive experimental study on the structural behaviour of the in-situ concrete stitch under different combinations of parameters has been carried out. Two types of specimens are tested in the study, namely the beam specimens and the shear specimens, which both consist of two precast units joined together by in-situ concrete stitch of variable widths. The beam specimens are internally prestressed and subject to different combinations of bending m oment, shear, and prestressing force; while the shear specimens are either internally or externally prestressed and subject to direct shear only. Shear keys are provided to the stitch of several shear specimens to examine the contribution of the keys to the shear strength. The effects of various parameters on the strength of the stitch and ductility of the specimens are investigated. Detailed coverage on the experimental programme and the results of the experimental analyses are presented in this paper. KEYWORDS Experimental study, joints, prestressed concrete, segmental bridges, in-situ stitches. INTRODUCTION Precast segmental concrete bridges have gained popularity over the past 40 years due to their efficiency in coping with difficult site conditions. One of the most commonly used method of constructing this type of bridges is the balanced cantilever method, which essentially involves sequentially extending precast segments outwards from each pier in a balanced manner. A gap of 100 to 200 mm in width is usually provided around the mid-span location between the last two approaching segments to facilitate erection. In-situ concrete is then cast to stitch the segments together, thus making the bridge deck continuous. Under the current practice, the in-situ concrete stitches are usually designed to be capable of sustaining considerable sagging moment but its hogging moment capacity and shear resistance are only nominal. Failure of these joints can only occur under exceptional scenarios when hogging moment is high. However if it really occurs, this could potentially trigger a progressive collapse mechanism because the concrete stitches are locations of potential weakness. Studies on the joints of segmental bridges have been conducted in the past (Buyukozturk et al., 1990; Hewson, 1992; Zhou et al., 2005; Issa and Abdalla, 2007) but the joints studied are either dry or epoxy joints that exists between precast segments and not the in-situ concrete stitching joint that is of interest. As relatively little research work on this area has been conducted, understanding of the actual behaviour of in-situ stitches is limited. In the light of this, an extensive experimental study has been carried out to investigate the behaviour of the in-situ concrete stitches. The study mainly involves a series of loading test on specimens that are comprised of precast units connected by in-situ concrete stitches. The stitch is subjected to different combinations of internal forces by applying loading at different locations along the specimen. Various parameters of the specimens are varied to examine their effect on the strength of the in-situ stitch and its failure mode. These parameters include the width of the stitch, the grade of concrete, the prestressing force, the provision of shear keys, the type of tendon (bonded or unbonded) and the type of prestressing (external or internal). Although the experimental programme is still ongoing, based on the analysis of the current experimental results, several preliminary conclusions have been drawn and are presented in this paper. The experimental programme is also covered i n detail in this paper. TESTING PROGRAMME The experimental study involves load testing on two types of specimens, namely (i) the beam specimens, and (ii) the shear specimens. The beam specimens are used to study the behaviour of the in-situ concrete stitches subjected to different combinations of bending moment and shear, while the shear specimens are used to study the behaviour of the stitches under direct shear. Both the beam and shear specimens consist of two precast units joined together by the in-situ concrete stitches. Control beam specimens have also been fabricated where the entire beam is continuously cast without any stitch along the beam. Typically, the stitch is cast one week after the casting of the precast units. Loading test on the specimens is performed using a testing frame after 28 days from the day of casting of the stitch. Linear variable displacement transducers (LVDTs) are mounted on the specimens at various locations of interest to measure the displacements at these locations. Configuration of the Beam Specimens The length of the beam specimen is 1400 mm with the in-situ concrete stitch at either the mid-span of the beam or offset from the mid-span depending on the internal force that the stitch is subjected to. An actual beam specimen is illustrated in Figure 1. Three cases of internal force at the stitch are examined, namely (i) pure bending moment, (ii) pure shear, and (iii) both moment and shear. The loading test setup to induce the three cases of internal force condition is illustrated in Figure 2. Tendon (a) Case of pure bending moment (b) Case of pure shear (c) Case of moment and shear The section of the beam has an overall depth of 200 mm and a width of 150 mm. A 7-wire steel strand with a nominal area of 100 mm2 is used as the prestressing tendon. The tendon is placed at a depth of 133 mm for Case (i) and Case (ii), and 100 mm for Case (iii). For all beam specimens, Grade 60 concrete is used for both the precast units and the stitch. No shear key is provided to the stitch. Unbonded tendon with an effective prestressing force of 100 kN is applied to all beam specimens. Since the precast units and the in-situ concrete stitch are cast at different time, construction joints exist in the specimen. Prior to casting the in-situ concrete stitch, the laitance at the construction joint area on the surface of the precast unit is removed and the area is roughened by a needle gun until the aggregates are exposed. The construction joint is then wetted for at least 12 hours before casting by laying towels that are completely saturated with water over the joint area. Configuration of the Shear Specimens The shear specimens consist of two L-shaped precast units with the in-situ concrete stitch joining the two units as illustrated in Figure 3. The out-of-plane dimension of the specimen is 200 mm. The specimens are either made of Grade 60 or Grade 45 concrete and both the precast units and the stitch are made of the same grade of concrete. The stitch is subject to a prestress of either 1 MPa or 5 MPa, and stitch widths of 100 mm and 200 mm are examined. The shear specimens are designed in such a way that they are capable of simulating the shear behaviour of box girders of different web configurations. The web of a box girder may or may not be provided with shear keys and some parts of the web may or may not have prestressing tendon running through. Therefore, the specimens are either internally prestressed by bonded tendon or externally prestressed by a clamping device to provide the prestressing force acting on the stitch, while the stitch is either plain or provided with shear keys. For those specimens with shear keys, either one large key with a depth of 50 mm or two smaller keys with a depth of 30 mm are provided. Examples of an externally prestressed specimen with two shear keys and an internally prestressed specimen without shear key are illustrated in Figures 3(a) and 3(b) respectively. For the case where the specimen is internally prestressed, a 7-wire steel strand is used. Prior to casting of the stitch, light roughening is provided at the construction joint area on the precast units to remove the laitance. Similar to the beam specimens, the joint area is wetted for at least 12 hours before casting the stitch. (a) Stitch with shear keys; externally prestressed (b) Stitch without shear key; internally prestressed Figure 4. Examples of setup for shear specimen RESULTS AND DISCUSSION Beam Specimens The load-displacement relationships of the beam specimens tested are plotted in Figures 5(a), 5(b) and 5(c) for the case of the in-situ concrete stitch subjected to pure bending moment (Case (i)), pure shear (Case (ii)), and a combination of moment and shear (Case (iii)), respectively. For the specimens of Cases (b) and (c), only the results of the specimens with 50 mm stitch and 100 mm stitch are available to date. Ductile behaviour is observed for the beam specimens of Case (i). Opening of the construction joints occurs at a load of between 70 kN and 80 kN, while the final mode of failure is concrete crushing in the compression zone at mid-span, as illustrated in Figure 6(a). From Figure 5(a), it is evident that the peak strength of the specimens without stitch (i.e. the control specimen) and those with stitch are approximately the same. The difference in the peak strength between the specimen with a 50 mm stitch and that with a 100 mm stitch is marginal. When the stitch is subject to pure shear, the behaviour of the specimen is brittle. As the peak strength is reached, a large diagonal crack suddenly forms across the stitch (Figure 6(b)) and the strength drops abruptly. It can be seen from Figure 5(b) that regardless of the size of the stitch, the peak strengths of the specimens are nearly the same. (a) Case (i) (b) Case (ii) (c) Case (iii) From Figure 5(c), it is evident that the behaviour of the specimens of Case (c) is ductile. Failure of the specimens is localized at the point of loading where there is significant cracking and crushing of concrete; while at the stitch, slight opening of the construction joint is observed and several diagonal cracks are found propagating from the construction joint towards the point of loading. The condition of the beam at failure is illustrated in Figure 6(c). For the specimen with a 50 mm stitch, the peak strength is approximately 100 kN, while that for the specimen with a 100 mm stitch is approximately 110 kN. The peak strengths of the two specimens are relatively close to each other. The results suggest that the width of the stitch has minimal effect on the strength of the stitch within the maximum width of stitch studied. The ductility of the specimens is also not affected by the width of the stitch but rather by how the specimen is loaded. (a) Case (i) (b) Case (ii) (c) Case (iii) Shear Specimens The load-displacement relationships of the five shear specimens tested are plotted in Figure 7. The shear displacement is the relative vertical displacement between the two precast units. All shear specimens are identified as explained below. Using E-K(M)-100-60-2 as an example, the first field represents the type of prestressing used, with E indicating external prestressing; the second field represents whether the stitch is plain or with shear keys, with K(M) indicating stitch with two shear keys, K(S) indicating stitch with single shear keys, and P indicating plain stitch with no shear key; the third field indicates the width of the stitch in mm; the fourth field indicates the grade of concrete in MPa; and the fifth field indicates the prestress applied to the stitch in MPa. Therefore, a specimen identified as E-K(M)-100-60-2 is composed of Grade 60 concrete with external prestress of 2 MPa applied and two shear keys are provided to the stitch that has a width of 100 mm. The specimens with plain stitch are first discussed. From Figure 7, it can be seen that the behaviour is largely the same for both specimens E-P-100-60-1 and E-P-200-60-1. The peak strengths of the two specimens are between 50 to 60 kN, which once again demonstrates that the width of a plain stitch has little effect on its strength. It is evident that as the prestressing level is increased to 5 MPa (E-P-100-60-5), the peak load-carrying capacity is significantly increased to approximately 220 kN. Therefore, the level of prestressing has marked influence on the load-carrying capacity of the stitch. For specimens with plain stitch, the failure mode is characterized by sudden occurrence of sliding along one or more of the construction joints. Upon failure, the strength of the stitch is mainly contributed by friction from sliding between the surfaces of precast unit and in-situ stitch. As observed from the load-displacement curves, a long smooth plateau is evident in the post peak range for specimens E-P-100-60-1 and E-P-200-60-1, which can be modelled as Coulomb friction. For specimen E-P-100-60-5, the post-peak behaviour as shown in Figure 7 is not as smoothed. Since the prestressing force is substantially higher, the resistance against sliding by the aggregates along the construction joint becomes very large. As the applied load is large enough to overcome that resistance, sudden slippage along the construction joint occurs and the load drops. Subsequently the resistance builds up again and sudden slippage occurs again when the resistance is overcome by the applied load. Therefore the post-peak branch of specimen E-P-100-60-5 has a zig-zag shape. This observation also implies that the roughness of the construction joint should have strong effect on the post-peak strength of plain stitches, which will be examined in due course. Since the post-peak strength of the stitch is mainly contributed by frictional forces, ductility can only be maintained if sufficient pre stressing force is provided. Therefore the presence of adequate prestressing force beyond the peak strength of the stitch is crucial in preventing sudden loss of strength in the stitch. Up to this stage, only two shear specimens with shear keys have been tested. However, the results from the test have already given indication that the behaviour of the stitches with shear keys is quite different from the behaviour of those without shear keys. Upon reaching the peak strength, the stitch of specimen E-K(M)-100-60-1 fails suddenly in a brittle manner by cracking diagonally across the stitch as illustrated in Figure 8 and an abrupt drop in load can be seen in Figure 7. This behaviour is much different from that of the specimens with plain stitches in which the post-peak behaviour is characterized by a long plateau in the load-displacement relationship. This type of stitch has little reserve strength upon reaching the peak load-carrying capacity. No brittle failure is observed for the specimen with one large key and a wider stitch, i.e. specimen E-K(S)-200-60-1. In fact, the specimen was not loaded to failure during the experiment but was stopped at a load of approximately 190 kN because at that load, the prestressing force was increased to a level that had almost reached the capacity of the load cell used to measure the prestressing force. However, at a load of 190 kN, continuous crack had already formed along the construction joint and there was sliding between the precast unit and the stitch along the joint but the stitch still remained intact. From Figure 7, it can be seen that the peak load-carrying capacity of specimens E-K(M)-100-60-2 and E-P-100-60-5 are approximately the same. This observation seems to imply same level of load-carrying capacity can be achieved yet less amount of prestressing can be applied by adding shear keys to the stitch. As aforementioned, there is an increase in prestressing force as load is applied to the specimens with shear keys. This behaviour is caused by dilation in the stitch as the shearing load is applied. Dilation is taken as the displacement between the precast units measured along the horizontal centreline of the stitch. The effect of dilation is much more pronounced for specimens with keyed stitches than those with plain stitches. The relationships between shear displacement and dilation of the various specimens are plotted in Figure 9. For the specimens with plain stitch, dilation is relatively insignificant compared to the dilation in the specimens with keyed stitch. The stress in the tendon can be increased due to dilation. The effect of dilation on tendon stress is rather insignificant for a segmental bridge with unbonded tendon because the strain increase due to dilation will be averaged along the entire length of tendon between end anchorages. However, for segmental bridges prestr essed by bonded tendon, dilation may cause substantial increase in strain at the location of the stitch, which can potentially overstress the tendon. Specimens with stitch prestressed by bonded tendon will be tested in the near future and the effect of dilation on tendon stress will be investigated in due course. CONCLUSIONS Extensive experimental studies have been carried out to investigate the behaviour of in-situ concrete stitches subject to a combination of internal forces and subject to direct shear by conducting a series of loading tests on the beam specimens and shear specimens respectively. Detailed coverage on the setup of the specimens and load testing has been included in this paper. Based on the results of the tests conducted so far, several preliminary conclusions can be drawn: The width of plain in-situ concrete stitch does not appear to have significant effect on the peak-load carrying capacity of the stitch regardless of the combination of internal forces that it is subjected to. The strength of the in-situ concrete stitch is strongly influenced by the level of prestressing applied and the strength of the stitch increases as the level of prestressing increases. For plain in-situ concrete stitches, failure occurs along the construction joint. Strength in the stitch is still present beyond the peak strength and it is mainly contributed by the frictional force from the sliding between the surfaces of precast unit and stitch. By providing shear keys to the concrete stitch, the level of prestressing can be reduced to achieve the same strength as those stitches without key. However, this may result in a brittle failure. For keyed concrete stitches, the amount of dilation is significantly higher than that of plain stitches. For segmental bridges prestressed by bonded tendon, this may have marked effect on the stresses of the tendons. With further testing on the specimens being carried out in the near future, it is expected that more definitive conclusions can be drawn on the behaviour of the in-situ concrete stitches. ACKNOWLEDGEMENTS The study undertaken is supported by Research Grants Council of the Hong Kong Special Administrative Region, China (RGC Project No. HKU 710207E).