Abstract
Tower cranes play an integral role in construction of civil engineering projects. In spite of this, tower cranes are associated with some risks. Thus, any civil engineering project has to include systems of ensuring the safety of the tower crane. Tower cranes should be managed at the sight based on the priorities given to the various project activities of the civil engineering project. Because of this significant role, this paper discusses the application of tower cranes in the construction of civil engineering projects. First, this paper examines some tower crane related accidents. This is followed by the determination of tower crane positions on site. This paper then examines tower crane base design. What follows is a detailed analysis of the staging and erection procedures of crane towers. Finally, this paper analyses the design of a tower crane (base and staging) in accordance with AS1418.4 before eventually making a conclusion.
Introduction
One serious concern in construction of civil engineering projects is the safety of the tower crane. According to Chiu & Kui (2008, pp. 1-6), tower crane is a crane that can swing and on which other structures can be fixed on a pole perpendicularly. Tower cranes are customary machinery at the site of any construction of civil engineering projects (Marshall 2000, pp.1-6). Tower cranes can rise up to 150 meters in the air and can lift up to 19 tones. Application of tower cranes in construction of civil engineering projects has especially become important following the series of crane accidents which have been experienced in the recent past. For instance, the Californian State has passed a law which is meant to curtail some tower crane activities in the construction of civil engineering projects. A board of supervisors from San Francisco have accented to the inclusion of a requirement of crane safety to the San Francisco Building Code (SFBC) (Chiu & Kui 2008, pp. 1-6).
A tower crane has several components; the base, the tower and the slewing unit (Marshall 2000, pp. 1-6). The first component of a tower crane is the climber. The climber can be lifted to various levels of any construction of civil engineering project. The next components is the free stand; a crane that swings in horizontal manner and that can be fixed at the bottom or at the rails of the civil engineering project but that is not fixed on another structure (Chiu & Kui 2008, pp. 1-6). The next component is the tower crane mobile which is fixed on a mobile machine such as a tractor. The final component is the self-erector. It should be appreciated that the San Francisco Department of Building Inspection (DBI) does not have any powers to regulate tower cranes in the construction of civil engineering projects. Similarly, the employees at the San Francisco Department of Building Inspection are not experts in regulating the tower cranes (Chiu & Kui 2008, pp. 1-6).
As a result of the seriousness given to the safety of tower cranes in construction of civil engineering projects, various codes and practices have been developed to act as the guide to the San Francisco Building Code Requirements (Chiu & Kui 2008, pp. 1-6). The various codes and practices are applicable to climber tower cranes as well as to standing tower cranes that are usually used in construction of civil engineering projects. All the same, these codes and practices are meant to meet the entire specifications of the Cal/OSHA. For a long time, simulations have mainly been employed in the academic circles. However, the civil engineering industry has seen an introduction of computer models resulting from the techniques of Special Purpose Simulation (SPS). This has had the effect of reducing the time for developing models used to design tower cranes in construction of civil engineering projects (Appleton et al pp. 1709-1715).
A tower crane can carry a maximum weight of 18 metric tones. To reach the highest level, the tower crane rises on its own by one pole every time. The moment the construction of civil engineering project has been accomplished, the procedure is inverted; with the crane disengaging the poles on its own. However, it is worth noting that the tower crane cannot carry such a weight in the event that the weight is placed at the tip of the spring. Use of the crane in the construction of civil engineering projects is based on the rationale that the nearer the weight is placed to the post, the greater the weight the tower crane can carry (Marshall 2000, pp. 1-6). In much construction of civil engineering projects, cranes do not fall because of the thick concrete base weighing about 183, 000 kg usually made by the civil engineering construction company before the arrival of the tower crane (Karavadia 2009). It is the big support bolts inserted deeply into the thick concrete base that supports the tower crane. However, this does not mean that tower cranes are safe. The use of tower cranes in construction of civil engineering projects is usually associated with several accidents as depicted below.
Some Tower Crane Related Accidents
The first tower crane related accident that can be mentioned in this study was in Penrose; Colorado. In this tower crane related accident, the OSHA issued a fine to the tune of $1,500 to a contractor by the name of Hardrock Structure because of a tower crane related accident that had led to the loss of life of at least one person and seriously injuring many others (Cranestodaymagazin.com 2008). In this tower crane related accident, Hardrock was subcontracted by Stresscon. The contract for Hardrock was placing girders which Stresscon was supplying to Mortenson Construction; the main contractor. The tower crane related accident occurred when Hardrock was making use of a crane in lifting a panel. In the course of lifting the panel, the riggings of the tower crane snagged on a beam and made the panel to fall on the construction workers who were working under. In the event of such tower crane related accidents occurring in the United States, a fine of $ 5,000 is normally levied by the safety examiner. However, given the fact that Hardrock was a small organization coupled with the fact that this was the first time Hardrock was involved in a tower crane related accident having violated the OSHA regulation on the need to train employees, Hardrock was only fined $1,500 by the safety examiner.
The next tower crane related accident took place in Dubai. Coincidentally, this tower crane related accident took place only a few meters from the place where crane professionals were paying a visit to the Middle East Cranes symposium on Cranes’ Today which was talking place in Dubai (Cranestodaymagazin.com 2008). During this tower crane related accident, the Potain luffer was carrying a concrete object. The object fell down and bent over the perimeter of the civil engineering project which was under construction. In this tower crane related accident, the crane was operating alongside other Potain towers. This was during twin tower civil engineering project for Aerated Concrete Industries (Acico) in Kuwait. In this tower crane related incident, three cranes among them the one that had caused the accident were climbing luffing object which was located outside. Meanwhile, a fourth crane had also been operational at the site of the civil engineering project. The news of the tower crane related accident came during the time experts were convening for a conference on Cranes Today’s Middle East Cranes in Dubai. The venue of the meeting was located a few apartments from Sheikh Zayed Road (Cranestodaymagazin.com 2008).
The other tower crane related accident occurred in St Petersburg, in Florida; United States of America. This tower crane related accident involved a lift of six cranes. Similarly, county commissioners from the nearby county of Miami Dade had had ongoing discussions concerning the newly introduced safety rules (Cranestodaymagazin.com 2008). The tower crane related accident in St. Petersburg took place when six mobile cranes which had been hired from the Kelley Equipment had been involved in the translocation of a pipe for Progress Energy; a South-Eastern US based manufacturing company dealing in electricity and coal. This tower crane related accident took place when the superstructure broke apart from the carrier and flung an operator by the name of George Huffman from his car. Luckily the victim came out of the accident unhurt. During the same period, legislatures in the nearby county of Miami-Dade went ahead with a decree by Commissioner Audrey Edmonson to place a stringent lift development and safety measures on local crane organizations dealing in construction of civil engineering projects (Cranestodaymagazin.com 2008). The decree relates to many moderate tower cranes together with construction of civil engineering hoists.
Another tower crane related accident was the case in which a contact with a power line killed an employee in Wisconsin (Cranestodaymagazin.com 2008). In this tower crane related accident, an employee with Voeller Mixer based in Port Washington was at work in one of the concrete mixers of the company which dealt in construction of civil engineering projects. A crane, which was also operational at work in the surrounding area, came into contact with the source of power leading to the electrocution of Tappa, the employee who was aged 21 years. The electrocution threw the employee a distance more than 20 meters from his work location. The fifth tower crane related accident, was an oil spillage which led to the apprehension of South Korean captains. In this tower crane related accident, the connection wire between tow tug-boats got cist in the sea. A barge that was floating freely pierced an oil tanker from Hong Kong causing spoilage of about 79,000 barrels of oil into the sea (Cranestodaymagazin.com 2008). This took place off the western coast of South Korea. As a result of the spillage, many birds were killed and the beaches in the western coast of South Korea turned black.
The other crane related accident is the incident in which a crane officer at BAE Systems had to dive in the sea following the collapse of his crane. This happened at the Port of San Francisco. The operator had took some time in the water which was estimated to have a temperature of 10°C before the officer could be rescued (Cranestodaymagazin.com 2008). Apparently, the pole of the 55f crane the operator had been working with snapped causing the crane to topple gradually into the water. It was established that the crane contained more than 50 gallons of oil the time the accident occurred. Another crane related accident that can be mentioned is the case of Seattle. In this crane related accident, a truck driver escaped unhurt having just alighted from a truck that was a few minutes later hit by steel metals falling off a mobile crane that had collapsed. The truck driver had been transporting steel metals to a construction of civil engineering project site in Snoqualmie. The crane, which caused the accident by picking up a weight of trusses only for the trusses to fall on the truck, had been in hired from Ness Cranes (Cranestodaymagazin.com 2008).
The next crane related accident was a risky rescue mission by a Fort Worth Fire Department engineer. In this rescue mission, a 40 tone United States crane had toppled over a big workshop. The 40 tone had been carrying loads into a hauler only to accidentally lean on the hauler. In the process, the operator by the name of Kevin Easton got stuck between the side of the crane and the side of the hauler (Cranestodaymagazin.com 2008). Eventually, the operator was helped out but with a broken tibia and fibula. Finally, the last crane related accident was the case of a construction of civil engineering project contractor based in the United Kingdom. In this case, a ban of £ 40,000 was placed on the UK based contractor Sir Robert McAlpine following a crane related accident. In this crane related accident, the excess weight of a mobile crane hit a light pole causing a civil engineering construction employee to lose his leg (Cranestodaymagazin.com 2008).
During the court hearing of the crane related accident which was held at Old Bailey, a criminology court in London, the civil engineering construction company affiliated to Sir Robert McAlpine was fined £ 40,000 and directed to pay about £ 13,000. This crane related accident, which took place in Westminster; London, occurred when the civil engineering construction company was working with a 250t Liebherr which Baldwins Crane Hire had leased to the civil engineering construction (Cranestodaymagazin.com 2008). An investigation on the crane related accident turned out that the location of the mobile crane had been tried in several places. When eventually the crane was located at a point, it was noted that the crane could hit a light pole but no action was taken to prevent such an occurrence (Cranestodaymagazin.com 2008). Of course the tower crane eventually hit a light pole with the shattered pieces of the pole hitting and seriously injuring an employee whose foot had to be amputated following the accident. This necessitated the fine.
The Determination of Tower Crane Positions on Site
There are several issues to be considered in the determination of tower crane positions on site. As was noted in the beginning, the determination of tower crane positions on site is usually done based on work priorities within a given period of time. This implies that with the increase in the number of construction of civil engineering project activities, the intricacy of the model also increases (Appleton et al pp. 1709-1715). This implies that the increase in the number of activities to be conducted in the construction of civil engineering project is likely to render conventional models useless to be employed in the civil engineering industry. The determination of tower crane positions on site using conventional SPS models uses the relational logic relationships in depicting the rationale behind the developed system. As a replacement of the conventional relational logic relationships, the tower crane relationship makes use of precedence ranking logic as the new model of developing a system.
The determination of tower crane positions on site can be done using the special purpose solution (SPS). The SPS is a technique which has been developed by symphony as a way of modeling the activities of tower cranes at construction of civil engineering projects (NSERC 2000). It is worth mentioning that the symphony ordinary model is a simulation technique for universal purposes that permit a construction of civil engineering projects practitioner to develop a system by making use of the ideas of how processes interact. It means that developing a construction of civil engineering project model by way of ordinary template would require the construction of civil engineering project practitioner to have prior knowledge of simulation tools. It means that to use the ordinary template, the construction of civil engineering project practitioner needs to have an understanding of issues such as modeling based on hierarchy, creating entities and routes, resources, data, as well as tracing (NSERC 2000).
During the determination of tower crane positions on site using the ordinary template, the main activities of the construction of civil engineering project are categorized into various ways such as rebar actions, slab activities, column activities, main activities as well as miscellaneous activities (Appleton et al pp. 1709-1715). Computerized simulation has been regarded as an instrumental technique for advanced users such as those in the construction of civil engineering projects. Computer based simulation is very instrumental because it offers the construction of civil engineering project practitioners with the needed flexibility and room for manipulation as to adopt any kind of civil engineering construction procedure (Appleton et al pp. 1709-1715).
The determination of tower crane positions on site using SPS has been described as the computer-developed surrounding designed to permit an expert to develop a construction of civil engineering project (Appleton et al pp. 1709-1715). By making use of SPS tools in the determination of tower crane positions on site and in creating an environment for developing models tailor made to the civil engineering industry, computer simulations offer many merits to the construction of civil engineering project practitioners (Appleton et al pp. 1709-1715). It is worth noting that conventional simulation models adopt the co relation logical relationships in driving procedures within the particular construction of civil engineering project. This is usually done on the basis of a given time frame and necessity. With regard to the determination of tower crane positions on site, it would mean that all the lifting actions have a designated time of occurrence and a predetermined precedence. All these would depend on how critical each activity is relative to the entire activities which are to be accomplished by the tower crane.
A construction of civil engineering project practitioner who understands how critical each activity of a tower crane is relative to the schedule of the construction of civil engineering project activities should have a template of SPS. This would be regarded as an effort towards the determination of tower crane positions on site (Appleton et al pp. 1709-1715). The SPS template can go along way in assisting the civil engineering project practitioner to understand how vital the specific activities of the tower crane are in relation to the overall activities of the construction of civil engineering project. With regards to construction of civil engineering projects that are characterized by a series of repetitive activities, logic depicted by co relational logical relationships is deemed appropriate. During the determination of tower crane positions on site, every activity taking place in the developed system does not go through an identifiable recurring procedural manner. Rather, they contain various identifiable activities moving in a linear manner in the entire crane.
In the course of the determination of tower crane positions on site, all the activities of the tower crane are done on the basis of the how urgently demanded they are in the system which has been modeled (Appleton et al pp. 1709-1715). With the rise in the number of lifting actions by the tower crane, the complication of the construction of civil engineering project using conventional co relational logic relationships becomes an uphill task which cannot be implemented within the construction of civil engineering project fraternity (Appleton et al pp. 1709-1715). The planned SPS tower crane guide will make use of the precedence ranking logical management in solving the problem during the determination of tower crane positions on site.
The above implies that for every selection of a lift during the determination of tower crane positions on site, the tower crane chooses the highly prioritized lifting action which is highly prioritized and which is presently within the model of the construction of civil engineering project. By making use of the precedence ranking logical control against the co relational logical relationships, the understanding of the domain of the tower crane is made easy (Appleton et al pp. 1709-1715). Using the precedence ranking logical management rationale during the determination of tower crane positions on site is characterized by several advantages. The first advantage of using the precedence ranking rationale is that it creates a modeling surrounding which is easy to develop and alter. In other words, the use of the precedence ranking rationale during the determination of tower crane positions on site in a construction of civil engineering project is that it can be manipulated by a civil engineering project practitioner. Second, precedence ranking rationale minimizes the time of developing new tower cranes models of civil engineering construction (Appleton et al pp. 1709-1715). Third, precedence ranking rationale shields the models of tower crane from rising complications arising from the rise in lifting actions during the determination of tower crane positions on site in an ongoing construction of civil engineering project.
Tower Crane Base Design
There are several issues in tower crane base design. During tower crane base design, some important changes can always be made to the design of the crane. The base of a tower crane is usually made of a big concrete pad which provides strength to the crane. The base of the crane is connected to the mast which acts as the height of the tower crane (Marshall 2000, pp. 1-6). At the very top of the tower is usually the slewing unit which enables the crane to go round when it is operational at the construction of civil engineering project. The first significant modification is to remove the pointed parts. Sometimes, during tower crane base design, the pointed parts of the post can be removed to ensure that the tower crane is constructed in a simple way and to ensure that the cost of constructing the tower crane is minimal (Resource Gwent Ltd 2003, pp. 1-36). Past research on the implications of eliminating the pointed parts have established that increasing the general diameter of the base part offers the required support in all the intended water levels, more so the in the case where very compressive strong concretes are adopted.
The second change which can be made during tower crane base design is to widen diameter of the base mast. This is in relation to the smallest parts of the concrete part of the hoist joined to the gravity stand in an integral way. In as much as this change would have implications in wave loadings, it is usually important to have a given level of flexibility (Resource Gwent Ltd 2003, pp. 1-36). This degree of flexibility at the construction of civil engineering project is best indicated by the base part using the adaptable sleeve. In tower crane base design, the big concrete filling is what first demonstrates how stable the crane is. During tower crane base design, this big concrete filling is usually made prior to the arrival of the crane. The filling usually measures 10 by 10 by 1.3 meters with a total weight of about 183, 000 kg (Marshall 2000, pp. 1-6).
The detailed tower crane base design at the construction of civil engineering project usually involves several elements. First are the elemental structures. In tower crane base design, caissons should be left as cylindrical structures as a way of maintaining the advantages of product line manufacturing techniques and reducing the differences in tooling (Resource Gwent Ltd 2003, pp. 1-36). In the course of tower crane base design, the caisson is expected to have a benchmark flat lid. It is expected that the benchmark flat lid will act as a passage to the lower part of the tower until it reaches the bottom. According to Marshal (2000, pp. 1-6), during the crane base design, the big support bolts are deeply inserted into the filling to provide strength to the base of the crane. This simply implies that in any construction of civil engineering project, the cranes are basically bolted in the soil in order to make them stable.
The second element in crane base design is moments. For water that is 15m deep, a diameter of 5m is considered much requirement in relation to moment ability and is thus allowed. It is worth pointing out that the size of the tower crane is left constant at a diameter of 5m in order to reduce disparities in structure (Resource Gwent Ltd 2003, pp. 1-36). At a height of the 30m there is a further increase in the loadings and the moment applicable on the tower at the level it is joined to the base increases to virtually the same level. Tower crane base design should be done in this manner because in any construction of civil engineering project, the crane can only reach a highest height of 80 meters if it is not supported. Marshal (2000, pp. 1-6) has argued that the base of the tower crane is designed in such a way that it can only reach a height of more than 80 meters in the event that the crane is tied on the civil engineering construction project as the civil engineering construction project increases around the building.
The third element in tower crane base design is the joining of structural element. This is especially in the area of fabricated and assembly joints. During tower crane base design fabricated joints permit the casting of the concrete parts of the tower crane to be done. In the same way, the fabricated joints goes along way in permitting the earlier cast components top be inserted. It should be recalled that fabricated joints are similar in any construction of civil engineering project and are made up of starter rods acting as reinforcements (Resource Gwent Ltd 2003, pp. 1-36). The greatest weight the tower crane can carry is about 19 metric tones. However, following tower crane base design, tower cranes are not able to carry such a weight in the event that the weight is located at the tip of the crane (Marshal 2000, pp. 1-6).
The second kind of joint is the assembly joint which is more complex in nature. In much construction of civil engineering projects, many assembly joints on the civil engineering project structure are straight from end to end (Resource Gwent Ltd 2003, pp. 1-36). This has implication that the assembly joints directly transfer tensile and compressive stress regardless of whether the linking boundary of the outer caisson and the caisson are not straight from and to end. In tower crane base design, the assembly joints are made in a careful way in order to avoid the failures resulting from compression. Tower crane base design uses two maximum value switches to ensure that crane is not overloaded. The utmost weight switch regulates the haul on the cable thereby ensuring that the weight does not surpass 18 metric tones (Marshal 2000, pp. 1-6). Next is the weight moment switch which ensures that the person in charge of operating the crane does not surpass the crane’s tone-meter ranking as the weight is moving out of the spring.
The last component of tower crane base design in any construction of civil engineering project is demountable joint. To maintain the capacity of reducing the mast as a result of its functioning use, tower crane base design uses an automatic mechanism of locking (Resource Gwent Ltd 2003, pp. 1-36). The locking mechanism takes place at the point where the higher and lower mast joints are connected. The higher part is whole and comprises of a ring extension which enables the connection of bolts and nuts on an equivalent ring extension. The moment the positioning of the upper part of the tower crane is accomplished, the extension bolts are put in place using a hydraulic scram pre-tensioning mechanism. This ensures that the entire bolts are fastened to the needed weight during tower crane base design.
In tower crane base design, the lower joint extension and bolts are designed in the same way as the upper extension joints although with bigger weights to work with. The joints located at the lower side of the tower crane are also inclusive of a leveling mechanism (Resource Gwent Ltd 2003, pp. 1-36). The moment the middle and the higher parts of the crane are uplifted, the structure of the tower crane is examined for how vertical it is as a way of compensating for any ascent in the surface. Tower cranes are usually transported to the construction of civil engineering project site in trailers. A mobile crane is then used in assembling the object placing the various components on a mast measuring 12 meters long and comprising two post parts (Marshal 2000, pp. 1-6). Counterweights are then added to the mobile crane. During tower crane base design, the changes to the tower are done at the joint located at the base using stationary hydraulic rams. After the sections of the tower have been aligned vertically, the leveling system is fixed into place and crammed with fast setting grout.
Staging and Erection Procedures of Crane Towers
There are various staging and erection procedures of crane towers. To illustrate these various techniques, we examine a construction of civil engineering project of the Kurushima Kaikyo Bridge. Kurushima Kaikyo Bridge is the first illustration of the first three related suspended bridges passing through Kurushima Strait. Kurushima Strait is renowned for being amongst the main vigorous tidal currents in Japan (Akihiro et al 2002, pp. 65-75). Owing to the fact that the stiffening support of the construction of civil engineering project of Kurushima Kaikyo Bridge is a unit cellular box support, direct hoisting technique was used in erecting the stiffening girder blocks (Mine et al 2000, pp. 87-96). Other than the direct hoisting technique, the other staging and erection procedure of crane towers is all-hinge erection technique. Other issues in staging and erection procedure of crane towers are erection of special portions, wind resistance in erections, as well as camber measurements during erections.
Direct Hoisting Technique
The first staging and erection procedure of crane towers is through direct hoisting. Taking the example of the construction of civil engineering project of Kurushima Kaikyo Bridge, 13 blocks were erected using direct hoisting technique based on various procedures. In the first staging and erection procedure of direct hoisting technique, the placing of an independently-driven barge laden with stiffening girder was done below the point of erection. During the second staging and erection procedure of direct hoisting technique, the main cable was fixed to the stiffening girder (Akihiro et al 2002, pp. 65-75). Next, the staging and erection procedure of direct hoisting technique entailed the seclusion of the independently-driven barge from its location area when unloading was taking place after which the stiffening girder was raided in place using the carrying beams through a lifting axis. The fourth staging and erection procedure of direct hoisting technique entailed the temporary connection of the stiffening girder to an available girder through lifting axis (Mine et al 2000, pp. 87-96). The stiffening girder and the mass of the stiffening girder block as well as the laden erection are the biggest incidents to have been hoisted directly in the history of Japan.
All-Hinge Erection Technique
Staging and erection procedure of crane towers can also be done through all-hinge erection technique. All-hinge erection technique encompasses two procedures; determining the way the erection axis is structured and incomplete splicing (Akihiro et al 2002, pp. 65-75). Because of the employment of all-hinge erection technique, the stiffening support blocks were joined for a temporary period using lifting hinges. Taking the case of Kurushima Kaikyo Bridge as a construction of civil engineering project, the erection axis configuration is done in a way that stiffening is not undertaken for the in-plane bends between blocks and the intrusion by the way the things were connected was avoided.
With regards to staging and erection procedure of incomplete splicing, the design of the stiffening girders is done on the basis of absence of stress by the time the design was under completion. In this case, the generation of negative bending moment was done in the girders during the later phases of erection (Akihiro et al 2002, pp. 65-75). However, given that the scaffolds for traveling for field splice were designed following the erection of final blocks in the working station, the flanges in the lower levels would affect one another. In the event that the lower flange intervals of a stiffening girder are reduced, jerks are used to pull the girders together in forceful way (Mine et al 2000, pp. 87-96). Moreover, as a mechanism of ensuring that the erection hinges located at the bending moment function in the correct way in the event of a storm, an area representing two-thirds of the inferior part of the side web as well as the centre web is simultaneously split.
Erection of Special Portions
Sometimes there can be special portions in a construction of civil engineering project. In the case of Kurushima Kaikyo Bridge as a construction of civil engineering project, there were some instances when erection processes were different from other kinds of erections applicable in general sections. For example, in some parts steel metals were used in the hangers close to the middle of the bridge (Akihiro et al 2002, pp. 65-75). Similarly, owing to the fact that the arrangement to carry beams on the side of the tower could be done instantly over an erection level. There are three activities in staging and erection procedure of special portions. The first activity is the erection of the rod-type hanger section. In this case, the procedure of erecting the special portions was changed such that the connection of the erection hinges was done after adjusting a level variation with the prevailing girders (Mine et al 2000, pp. 87-96). The second staging and erection procedure was to pass the lifting beam on top of the rod-type hanger. Compressive pressures acted on the steel-metal hanger the time a lifting beam passed on top if it. The third staging and erection procedure in the erection of special portions is the erection of a slab attached to the tower. In this case, it was important to pull-in from the basic tower during swing erection.
Wind Resistance in Erections
The other important issue in staging and erection procedures of crane towers is the issue of wind resistance. Since fixing by erection hinges and incomplete splitting on its own would not be strong enough, a decision was made to cut the side of the central part of the closing slab (Akihiro et al 2002, pp. 65-75). In the example of Kurushima Kaikyo Bridge as a construction of civil engineering project, the central part of the closing slab was done to minimize out of plane moment in the course of the erection time (Mine et al 2000, pp. 87-96). Similarly, the central part of the slab was done in order to split the final slab after completing the entire splicing of blocks in general portions. In addition, slabs were set aside going round restricted by seeing to it that the transfer of weight from the final of the stiffening tower to the wall of the tower was drone using a cushion substance.
Buffeting in the course of erection is likely to destroy the construction of civil engineering project. This can take place when the bottom flange opens and closes prior to splicing (Akihiro et al 2002, pp. 65-75). In reference to the case of Kaikyo Bridge as a construction of civil engineering project, attempts were made to prevent this phenomenon by undertaking splicing in advance. Thus, in preparation for interruption, the installation of a cushion jig was done in the beam which ran along the longitude of the bottom flange. The partial splicing procedure was planned after considering the number of times the bottom flange opened and closed resulting from buffeting. The partial slicing procedure was also done after considering the amount of joints made each day, and finally, after determining the bottom-flange time lapses and the forceful draw-in force in every stage of erection (Mine et al 2000, pp. 87-96). The above measures should always be taken in any construction of civil engineering project in the event that there is storm or if wind with velocity surpassing the critical figure is anticipated.
Camber Measurements during Erections
In our illustrative example of Kurushima Kaikyo Bridge as a construction of civil engineering project, pin fixing technique was used as the technique of fixing the hanger of this construction of civil engineering project. For that matter it was not possible to make adjustments to the shape of the guider in the course of erection (Akihiro et al 2002, pp. 65-75). In this staging and erection procedure of camber measurements, and as a way of understanding the function played by the guider, it was necessary to carry out a site survey every moment the installation of a stiffening girder slab was done. During this staging and erection procedure of camber measurements, it was also necessary to carry out a site survey every moment the installation of a stiffening girder was done as a mechanism of checking how aligned the construction of civil engineering project was (Mine et al 2000, pp. 87-96). This highlights the importance of camber measurements during erections in any construction of civil engineering project.
Design of a Tower Crane (Base and Staging) in Accordance with AS1418.4
The Occupational Health and Safety (OSH) Regulation of 2001 stipulates that the design of certain kinds of construction of civil engineering projects be done in line with the applicable standard in Australia. The design of a tower crane (base and staging) in accordance with as1418.4 clearly provides ways of safeguarding people working in high construction of civil engineering projects. The Australian Standard AS 1418.4 is a regulation providing for safety of the cranes, hoists and winches (Industry Plant Consultative Committee 2005, pp. 1-2). The design of the tower crane, both the base and the staging, are well stipulated in the AS1418.4. Moreover, it is required that the design of construction of civil engineering projects be registered. The registration requirement is especially needed for mobile cranes having the capability of more than 10 tones as well as tower cranes. The AS1418.4 stipulates that workboxes which are meant to be hanged from the crane should be registered (Whitehead 2002, pp. 1-4). According to clause 142(3) (d), people working in a construction of civil engineering project should not be suspended with any kind of crane except a crane specifically intended for that particular purpose. Simply put, the AS1418.4 states that in no given scenario will a worker at a construction of civil engineering project be loosely pendant from the clip of a tower crane.
The design of a tower crane (base and staging) in accordance with as1418.4 provides that tower crane should be clearly labeled to indicate the maximum tare load, the highest number of people it can carry, the highest kilograms it can carry as well as an identification number. The AS1418.4 also provides that crane workboxes should not carry more than three people (Whitehead 2002, pp. 1-4), and that the stiles of the tower crane should fill the corridor 1000mm (Industry Plant Consultative Committee 2005, pp. 1-2). Out of the three people, the AS1418.4 further states that one individual should be knowledgeable in crane signs. According to Industry Plant Consultative Committee (2005, pp. 1-2), in the base and staging design of a tower crane, the longest pace which should exist between the rungs is 300mm and that the rungs should have a diameter of 20mm. Similarly, the AS11418.4 provides that the base and staging design of a tower crane should be such that the length between the stiles is 300mm. Moreover, the AS 1418.4 stipulates that the rungs and the frames of the tower crane should have enough distance (Industry Plant Consultative Committee 2005, pp. 1-2).
The rungs and the frames of the tower crane should not have any obstruction to ensure that a good foothold is achieved; AS1418.4 provides that this should be a minimum of 160mm. The design of a tower crane (base and staging) in accordance with as1418.4 further requires that if upright ladders are employed, there need to be a rest platform of 12.5 m followed by every 10.0 m. The AS1418.4 further provides that landing grounds for construction of civil engineering project workers need to be a minimum of 450mm in width. Industry Plant Consultative Committee (2005, pp. 1-2), have noted that boundary safety has to be offered in order to prevent workers in a construction of civil engineering project from falling down. The AS1418.4 also stipulates that during base and staging design of a tower crane, walkways need to have a minimum width of 225 mm. According to Industry Plant Consultative Committee (2005, pp. 1-2), boundary protection have to be continual and encompasses guardrail placed in a straight way and middle guardrail. Alternatively, the boundary protection could have an infill pane playing a similar function as a middle guardrail and toe board reinforced by posts.
The parts of the tower crane should withstand at least a point weight of 550 N whether the weight is functional in a vertical or horizontal manner. If fall arrest is employed, the design of a tower crane (base and staging) in accordance with as1418.4 stipulates emergency measures have to be put in place. The AS1418.4 further provides that the workers in the construction of civil engineering project be taken through a training session on the way the emergency measures can be applied in rescuing a falling worker by employing a fall arrests (Industry Plant Consultative Committee 2005, pp. 1-2). This is very necessary because workers in a construction of civil engineering project can suffer fatal injuries if they happen to fall from a crane. Organizations dealing in construction of civil engineering projects must see to it that there is secure entrance to all places where workers are working. Similarly, organizations in construction of civil engineering projects must make sure only the crane maintenance team have access to the tower cranes. Finally, the design of a tower crane (base and staging) in accordance with as1418.4 also expects suppliers of tower cranes to comply with all its provisions.
Conclusion
This paper has examined the application of tower cranes in the construction of civil engineering projects. In the first part, this paper examined the some tower crane related accidents. This study has established that despite the pivotal role played by tower cranes in any construction of civil engineering project, tower cranes are usually associated with several accidents. This study has established that a contact with a power line has led to the death on an employee, with other organizations in construction of civil engineering projects even being fined as a result of crane related accidents (Cranestodaymagazin.com 2008). Possibly, organizations in construction of civil engineering projects in Japan have realized this increased number of crane related accidents and have began to recall many of their cranes (Cranestodaymagazin.com 2008). This means that the government of Japan is increasingly becoming more attentive with the concerns and disclosures of customers with regards to tower crane safety.
This paper has also examined the determination of tower crane positions on site. This study has established that managing the tower crane at the sight of the construction of civil engineering project should be dependant on the priorities which have been given to the various activities being undertaken as the construction of civil engineering project (Appleton et al pp. 1709-1715). This study has established that conventional techniques of making models have used relational ranking relationships as a way of representing the logical issues encompassed in the modeled systems. On the contrary, tower cranes employ precedence ranking rationale as the replacement of relational ranking relationship in depicting logical issues which have to be considered in designing tower cranes (Appleton et al pp. 1709-1715).
This paper has also reviewed tower crane base design. This study has established that tower crane base design is a complicated issue involving many activities. For instance, this study has established that increasing the diameter of the bottom post parts can go along way in providing enough support in all the planned depths particularly in the areas where elevated firmness concrete are used (Resource Gwent Ltd 2003, pp. 1-36). The bottom of the tower crane is usually bolted into big concrete slab in order to support the crane (Marshall 2000, pp. 1-6). The base of the tower crane is designed in such a way that the bottom of the crane is connected to the tower. The tower crane acquires its stability from the big concrete slab that the organization dealing in construction of civil engineering project makes prior to the arrival of the tower crane. This concrete slab, which offers support to the base of the crane, usually measures about 30 by 30 by 4 feats. Thus, tower cranes are usually fixed into the ground to make them stable.
This paper has also examined the staging and erection procedures of crane towers. This study has established that crane towers can be erected using various techniques. These include direct hoisting and all-hinge erection techniques (Akihiro et al 2002, pp. 65-75). During staging and erection procedures of crane towers, it is usually important to consider the issue of special portions and resistance to wind. This implies that in any construction of civil engineering project, there could arise some situations which might necessitate that the different procedures are used to erect the crane towers. The illustrative example of Kurushima Kaikyo Bridge as a construction of civil engineering project indicated that crane towers should be staged and erected in manner that can resist strong winds (Mine et al 2000, pp. 87-96).
Finally, this paper has examined the design of a tower crane (base and staging) in accordance with AS1418.4. With the enactment of the Occupational Health and Safety Act of 2000, there was need to abolish the regulations of the Constructions Safety Act. The OHS 2001 stipulates that construction of civil engineering project sites have to be designed in tandem with the provisions of Australian Standard AS1418 (Whitehead 2002, pp. 1-4). The AS1418.4 was a standard which was established by the Standard Australia Committee ME-005 especially on cranes. The AS1418.4 seeks to present a nationwide standardized prerequisite of designing tower cranes by the importers, the manufacturers, the organizations in construction of civil engineering projects who use the cranes as well as those in regulation (Standards Australia International 2004, pp. 1-8). This study has therefore established that the AS1418.4 categorically provides precise ways of reaching high areas for operation and preservation intentions.
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