在许多编程语言中，可以使用以下方法将字符串按起始值拆分为多行：

1. Python:

def split_string(string, start_index):
    return [string[i:i+start_index] for i in range(0, len(string), start_index)]
    
# 示例
string = "This is a long string that needs to be split into multiple lines"
start_index = 10
result = split_string(string, start_index)
print(result)

2. Java:

public class SplitString {
    public static void main(String[] args) {
        String string = "This is a long string that needs to be split into multiple lines";
        int start_index = 10;
        String[] result = splitString(string, start_index);
        for (String line : result) {
            System.out.println(line);
        }
    }
    
    public static String[] splitString(String string, int start_index) {
        int length = string.length();
        int numLines = (length + start_index - 1) / start_index;
        String[] result = new String[numLines];
        for (int i = 0; i < numLines; i++) {
            int startIndex = i * start_index;
            int endIndex = Math.min((i + 1) * start_index, length);
            result[i] = string.substring(startIndex, endIndex);
        }
        return result;
    }
}

3. JavaScript:

function splitString(string, start_index) {
    var result = [];
    for (var i = 0; i < string.length; i += start_index) {
        result.push(string.substr(i, start_index));
    }
    return result;
}

// 示例
var string = "This is a long string that needs to be split into multiple lines";
var start_index = 10;
var result = splitString(string, start_index);
console.log(result);

以上示例中，splitString函数接受一个字符串和起始值作为参数，并返回拆分后的字符串数组。根据给定的起始值，循环遍历字符串并使用相应的起始值和结束值截取子字符串，将其添加到结果数组中。最后，返回结果数组。