## 1.Introduction

According to the statistics, Korea heavily relied on international trade about 98.6 % in 2014 (Statistics Korea, 2016) and it is important for the development of its economy to transport import or export cargoes efficiently through ports and establish relevant infrastructures. For the efficient port operation, it is essential to secure proper capacity of port facilities as well as anchorages for safe operation of ports. Although the size of economy is expanding, the development of port facilities has not been followed properly, and there seems to be a less interest in anchorages that are used as waiting place for entering/departing ships as well as have a close relation to the safety of ports.

Ulsan port, the biggest hub port that handles liquid cargoes, is recently planning the continuous expansion of port facilities and the relevant infrastructures in order to grow as a vital crude oil cargo port in Asia through the Far East oil hub business (Lee, 2014). However, as the optimum capacity of anchorages are not secured for the increasing number of entering/departing ships, it may increase the possibility of dangers in relation to the safety of ships anchoring and passing.

There are some studies on the capacity of anchorage so far, for instance, Deville (2011) suggested anchorage utilization by using simulation method according to the anchorage shape, Kim (2010) suggested standards for securing anchorage by comparing the degree of congestion and efficiency of anchorages, and Lee and Lee (2014) suggested Pyeongtaek port's according to the increase of harbour volume. However, there is no study on the suggestion of necessary capacity of anchorage according to the expansion of port in order to take a preliminary action on the demand of anchorage in the future.

This study proposed a model which can calculate the Anchorage Operating Rate (Hereinafter referred to as "*AOR*") and proposed an interactive formula by carrying out a regression analysis on the interrelation among the number of ships using anchorage, the length of ship, and the dwell time at anchorage and harbour volume. With this formula, this study analyzed the *AOR* at anchorages in Ulsan port at its present (2014) and the future (2020), and ultimately proposed the necessary capacity of anchorage in the upcoming future.

## 2.Establishment of Model for Evaluating *AOR*

In order to identify the extent of anchorages being used and analyze whether the anchorages are sufficient or not, the *AOR* model was suggested by considering the volume of ships using anchorage, the dwell time at anchorage and other various conditions. The concept of *AOR* and estimating methods will be discussed below.

### 2.1.Volume of ships using anchorage (ship/day), *AV*_{R}

_{R}

The volume of ships using anchorage (Hereinafter referred to as "*AV _{R}*") can be defined as the average number of ships using anchorage per day among ships that used such anchorages for 1 year, without considering peak factors and types of ships. The formula is as follows (Formula 1).

Where, *S _{i}* : The number of ships using anchorage per

*i*day

*T* : The number of days using anchorage per year except for unavailable days of anchorage due to natural disaster

### 2.2.Volume of anchorage capacity (ship/day), *AV*_{C}

_{C}

If there are many long-term waiting ships at anchorage, the volume of anchorage capacity would be decreased compared to many short-term waiting ships. Consequently, the volume of anchorage capacity (Hereinafter referred to as "*AV _{R}*") can be defined as the volume of ships using anchorage per day when the dwell time at anchorage is considered on the basis of the number of ships that can anchor at once and the formula is as follows (Formula 2).

Where, *D _{i}* : Dwell time of ships using anchorage

*U* : The number of ships that can anchor at once

### 2.3.Anchorage operating rate (%), *AOR*

The *AOR* can be defined as the proportion of the average number of *AV _{R}* to the

*AV*, and the formula is as follows (Formula 3). If

_{C}*AOR*is 100 %, it means that the anchorage has reached the theoretical maximum number of ships that the anchorage can accommodate. If this figure is less than 100%, it means that the anchorage can accommodate more ships that wish to use the anchorage.

if, *AOR* = 100 % ; Maximum *AOR*

*AOR* < 100 % ; Sufficient anchorage

*AOR* > 100 % ; Insufficient anchorage (Additional anchorage required)

## 3.Survey of the Current Status of Anchorages in Ulsan Port

### 3.1.Arrangement and capacity of anchorages in Ulsan port

The anchorages in Ulsan port are consisted of E, W, M, T anchorages and they are designed to accommodate different size of ships according to natural environmental factors such as depth, wave. However, for the purpose of this paper, W and T anchorages are excluded for this research because W anchorage is rarely used and T anchorage is used only by ships calling at Mipo port. The capacity and area of E and M anchorages in Ulsan port are shown as below (Table 1).

The M anchorage in Ulsan port is a group anchorage, located on the right side of No. 1 Fairway, and on the left side of the Hyundai Heavy Industry. The M anchorage can be used by ships below 2,000 GT and ships obtaining special permit from the Ulsan Regional Office of Oceans and Fisheries. E1~E3 anchorages are the main anchorages in Ulsan port, adjacent to the right side of No. 1 Fairway, it is easy for ships calling at Ulsan port to proceed to the fairway after using the anchorages. It was found that the E1 anchorage can be used by ships below 10,000 G/T, E2 anchorage by ships below 30,000 G/T, E3 anchorage by ships below 150,000 G/T.

### 3.2.Survey of the current status of anchorage in Ulsan port

The number of anchoring ships in Ulsan port, average dwell time, average length of ships and the number of incoming ships between the year of 2005 and 2014 were explored through the Ulsan Regional Office of Oceans and Fisheries (2014), and the harbour volume in Ulsan port was also studied during the same period through the statistical data of the UPA (2015). The findings are as follows (Table 2).

The table shows that the harbour volume in Ulsan port has generally increased for 10 years, and so does the average length of ships using anchorages in Ulsan port. However, the number of ships using anchorages was analyzed to have fluctuated during the period.

### 3.3.Depth and seabed of anchorages in Ulsan port

The depth and seabed of anchorages in Ulsan port were analyzed through the ECDIS data, and the findings are as follows (Table 3).

The seabeds of anchorages in Ulsan port are all ‘Mud’. The depth at E3 anchorage is the deepest with 60 m, and depth at M anchorage is the shallowest with 12 m.

## 4.Analysis of *AOR* at Anchorages in Ulsan Port in 2014

### 4.1.Analysis of the number of ships that can anchor at once

In order to calculate the number of ships that can anchor at once, first, it is necessary to examine the average length of ships using anchorages. Furthermore, after checking the turing radius required for anchoring according to the formula for calculating the turning radius of anchorage specified in the MOF (2014), the number of ships that can anchor at once in Ulsan port can be identified by drawing the turing radius at E and M anchorages in Ulsan port. Accordingly, the number of ships that can anchor at once was analyzed by drawing through Autocad program after examining the average length of anchoring ships per anchorage in Ulsan port, and checking the turning radius according to the Korea Harbour and Fishery Port Design Standards.

#### 1)Analysis of the Korea Harbour and Fishery Port Design Standards

The principle of anchorage designation is that the scale of anchorage is generally decided through the formula for calculating the turing radius of anchorage specified in the MOF (2014) and, among those anchorage designation methods, geographical and marine traffic conditions are comprehensively taken into account in order to designate the optimum anchorage.

The design standards for anchorage require that the radius of anchorage is calculated according to seabed condition and wind scale on the basis of length over all (LOA) of ships and depth (D) of anchorage. Accordingly, the turing radius of anchorage was analyzed on the basis of single anchor, which is generally used in practice when anchoring. The formula is as follows (Table 4).

#### 2)Analysis of turing radius of anchorages in Ulsan port

Having analyzed average length of ships using anchorages in Ulsan port, depth and seabed of anchorages, the turing radius was calculated by applying the Korea Harbour and Fishery Port Design Standards. The findings are shown as below (Table 5).

#### 3)Analysis of the number of ships that can anchor at once in Ulsan port

With the data from Table 5, which is about the turning radius of anchorages, the number of ships that can anchor at once in Ulsan port was drawn through Autocad and ECDIS program. The figure is as follows (Fig. 1).

It was analyzed that at M anchorage in Ulsan port, 20 ships can anchor at once and at E1 anchorage 18 ships, at E2 anchorage 11 ships, E3 anchorage 7 ships can anchor at once.

### 4.2.Analysis of *AOR* at anchorages in Ulsan port in 2014

#### 1)Analysis of volume of ships using anchorage and volume of anchorage capacity

In order to analyze *AOR* at anchorages in Ulsan port in 2014, the volume of ships using anchorage and volume of anchorage capacity were analyzed, and the findings are as follows (Table 6).

As it was found that the anchorages in Ulsan port have not been used for 3 days due to the influence of heavy weather and typhoon, the *AV _{R}* per day was analyzed by dividing the number of ships using anchorage for 1 year by 362 days.

For the *AV _{C}*,

*AV*of M anchorage, which has the shortest dwell time, is the largest with 29.4 ship/day, followed by E1, E2 and E3 anchorages. Thus, it was analyzed that the volume of anchorage capacity is related to the anchorage dwell time.

_{C}#### 2)Analysis of *AOR*

The *AOR*s were analyzed on the basis of the analysis of volume of ships using anchorage and volume of anchorage capacity, and the findings are as follows (Fig. 2).

Accordingly, among anchorages in Ulsan port in 2014, E3 anchorage is the highest with 88.6 %, followed by E1 anchorage with 84.0 %, E2 anchorage with 62.6 %, M anchorage with 48.6 %. Analysis shows that *AOR*s at E3 and E1 anchorages in Ulsan port are over 80 %, which is a bit high, but below 100 %. Thus, it is considered that the current anchorages in Ulsan port have maintained the proper capacity of anchorages.

## 5.Prediction of Future *AOR* in Ulsan Port

### 5.1.The method for predicting *AOR* in Ulsan port

In order to predict future *AOR* in Ulsan port, the estimation shall be required with regard to the number of ships using anchorage, the size of ships using anchorage (length of ship) and the dwell time at anchorage at the time of analysis. For the estimation of those factors, the interrelation among harbour volume, ships using anchorage and incoming ship, which are generally used as the index of port development plan, can be examined. This study carried out a regression analysis of interrelation among the number of ships using anchorages in Ulsan port, average length of ship, average dwell time, harbour volume and the number of incoming ships between the year of 2005 and 2014, and consequently suggested an approximate formula.

The regression analysis (Fig. 3~5) were carried out in order to estimate the number of ships using anchorage, the average length of ships using anchorage and the average dwell time at anchorage and the formulas are as follows (Formula 4~6).

Where, *Y _{A}* : Ship using anchorage (ship)

*X _{H}* : Ship incoming harbour (ship)

*Y _{L}* : Ship's length (m)

*X _{V}* : Harbour volume (kton)

*Y _{D}* : Dwell time (h)

The statistical analysis using SPSS program was carried out in order to test for significance of formulas induced via regression analysis and the findings are as follows (Table 7).

With the result of suitability analysis of the regression model, it was found out that the explanatory power of all formulas are over 80 % and the Durbin-watson test was within the range of 1~3, approving the independence of residual. With the result of significance test of dispersion model, it was found out that the significance probabilities against "F" are below 0.05, satisfying the suitability of regression model. Furthermore, the test for significance of regression coefficients was conducted and the levels of significance (p) are below 0.05, being statistically significant at the level of 5 %.

### 5.2.Analysis of parameters per anchorage in Ulsan port in 2020

The future harbour volume in Ulsan port specified in the (MOF, 2011) will be 252,611 kton/year, and the Ulsan Port Authority anticipates that the number of incoming ships in 2020, when the construction of New Port and Oil hub Port is completed, will be 29,828 ships. With this data, the number of ships using anchorage, average length of ship and average dwell time at anchorage in 2020 is predicted as follows (Table 8).

The total number of ships using anchorages, average length of ships using anchorage and average dwell time at anchorage in 2020 were estimated on the basis of the approximate formula provided in paragraph 5.1. The total number of ships using anchorages was divided according to the ratio of incoming ships per anchorage, and the average length of ships and average dwell time were also estimated in proportion to data of each anchorage.

### 5.3.Prediction of *AOR* in Ulsan Port in 2020

#### 1)Analysis of the number of ships that can anchor at once

On the basis of Table 9, led by parameter analysis per anchorage in Ulsan port in 2020, the number of ships that can anchor at once in Ulsan port was drawn through Autocad and ECDIS program. The findings are as follows (Fig. 6).

It was analyzed that at M anchorage in Ulsan port, 18 ships can anchor at once and at E1 anchorage 17 ships, at E2 anchorage 10 ships, E3 anchorage 7 ships can anchor at once. Accordingly, it was found that the number of ships that can anchor at once at E1, E2, M anchorages in 2020 is 1 ship less than those in 2014.

The *AOR* can be defined as the proportion of the *AV _{R}* to the

*AV*.

_{C}#### 2)Volume of ships using anchorage and volume of anchorage capacity

In order to predict the *AOR* at anchorage in Ulsan port in 2020, the volume of ships using anchorage and volume of anchorage capacity were analyzed and the findings are as follows (Table 10). When calculating the *AV _{R}*, 362 days, which is the same as 2014, was used for the average days using anchorage for 1 year.

For the *AV _{C}*,

*AV*of M anchorage, which has the shortest dwell time, is the largest with 17.2 ship/day, followed by E1 anchorage with 10.4 ship/day, E2 anchorage with 5.4 ship/day and E3 anchorage 2.9 ship/day.

_{C}When calculating the *AV _{R}*, 362 days, which is the same as 2014, was used for the average days using anchorage for 1 year. For the

*AV*,

_{C}*AV*of M anchorage, which has the shortest dwell time, is the largest with 17.2 ship/day, followed by E1 anchorage with 10.4 ship/day, E2 anchorage with 5.4 ship/day and E3 anchorage with 2.9 ship/day.

_{C}#### 3)Prediction of *AOR*

The *AOR* in 2020 was anticipated on the basis of the analysis of volume of ships using anchorage and volume of anchorage capacity, and the findings are as follows (Fig. 7).

Accordingly, among anchorages in Ulsan port, it was analyzed that, in 2020, the *AOR* at E1 anchorage will be the highest with a rate of 168.3 %, followed by E3 anchorage with 131.0 %, E2 anchorage with 118.5 %, M anchorage with 108.7 %.

As a result of the estimation of the *AOR* in 2020 on the basis of the current status of anchorages and port operation data in Ulsan port between the year of 2005 and 2014, it was analyzed that *AOR* at all anchorages will be over 100% in 2020 and it is considered that additional anchorages need to be secured.

The number of necessary anchored ships was examined in order to decrease the *AOR* to the level of 100 %, and the findings are as follows (Fig. 8). It is therefore analyzed that more areas which can accommodate additional 11 ships at E1 anchorage, 1 ship at E2 anchorage, 2 ships at E3 anchorage and 1 ship at M anchorage respectively would be necessary. As a whole, it is considered that the proper capacity of anchorages that can accommodate the total of 67 ships at the same time would be required.

## 6.Conclusion

This study proposed methods to evaluate the proper capacity of anchorage in Ulsan port by introducing the concept of *AOR* and suggested the formula by carrying out a regression analysis on the interrelation among the number of ships using anchorage, the length of ship, and the dwell time at anchorage and harbour volume. With this formula, this study anticipated the *AOR* at anchorages in Ulsan port in 2020 and proposed the necessary capacity of anchorage.

The results of this study are as follows.

First, the *AOR* was introduced by considering the number of ships using anchorage, the dwell time, the length of ship, and the standards for calculating the proper capacity of anchorage were proposed.

Second, having analyzed the *AOR* at anchorages in 2014, the AOR at E3 anchorage is the highest with 88.6 %, followed by E1, E2 and M anchorages. Analysis shows that *AOR*s at E3, E1, E2 and M anchorages in Ulsan port are less than 100 %, thus, it is considered that the current anchorages in Ulsan port have maintained the proper capacity of anchorages.

Third, in order to anticipate the necessary capacity of future anchorages in Ulsan port, the interactive formula among the number of ships using anchorage, the dwell time, the length of ship and harbour volume was proposed on the basis of the current status of anchorages and port operation data in Ulsan port between the year of 2005 and 2014.

Fourth, as a result of the estimation of the *AOR* at anchorages in Ulsan port in 2020, it was analyzed that the *AOR* at E1 anchorage will be the highest with 168.3 %, followed by E3 anchorage with 131.0 %, E2 anchorage with 118.5 %, M anchorage with 108.7 %. Thus, it was analyzed that *AOR* at all anchorages will be over 100 % by 2020 and it is considered that additional anchorages need to be secured.

Last, the number of necessary anchoring ships was examined in order to decrease the *AOR* to the level of 100 %, and it is analyzed that more areas which can accommodate additional 11 ships at E1 anchorage, 1 ship at E2 anchorage, 2 ships at E3 anchorage and 1 ship at M anchorage respectively would be necessary.

With this concept of *AOR*, the *AOR* at anchorages in Ulsan port can be analyzed and the quantitative propose can be possible as to whether the anchorages are sufficient or not and the necessary capacity of anchorages. Thus, it would contribute to the systematic management of anchorages by port planner or operating authorities.

Future study is needed to study the techniques that can analyze the *AOR* considering the characteristics of the port, such as peak time, type of ship. Moreover, with this concept of *AOR* specified in this paper, the *AOR* at all anchorages in South Korea can be analyzed and it can ultimately contribute to the safety of ships within ports by applying the proper capacity of anchorage to the Korea Harbour and Fishery Port Design Standards.