You understand this precisely. CGEL (398-9) identifies which, what, whichever and whatever as relative determinatives and remarks that
The only relative determinative found outside the fused construction is which. It occurs in supplementary but not integrated relatives.
The ‘fused construction’ is also known as the ‘free relative’ construction, so CGEL is speaking here of the use of which in bound relative clauses, as in your examples.
The supplementary/integrated distinction is more widely known as that between nonrestrictive and restrictive relative clauses: relative determinative which is not used in restrictive relatives. In Present-Day English the noun it determines (point and case in your examples) almost always refers to the entire head clause or to some implicit aspect of that clause’s content
At the point at which I was told that my work was unsatisfactory I submitted my resignation.
In a case in which you feel to frail to deal with things, do them as soon as is convenient.
Where is a ‘pro-form’—it ‘stands for’ or refers to another entity in the discourse—but it is not a pronoun. It should be understood as a ‘pro-adverbial: it stands for an adverb, or for a clause or preposition phrase which acts as an adverb.
Because where does not stand for a noun or noun phrase, it cannot act as the object of a preposition:
∗ The office in where I work is on the fourth floor.
If you want to refer to the place itself in a preposition phrase you must use which:
ok The office in which I work is on the fourth floor.
HOWEVER: this does not mean that the three examples in your question are ungrammatical; they are grammatical, but they do not mean what you want them to mean.
Just like pronoun wh- forms, where can be used to head an interrogative:
Where do you work? —I work at 1801 Broadway.
Where can also head a bound relative clause:
I work at 1801 Broadway, where my office is on the fourth floor.
Here where is equivalent to in or at which place.
- Note, by the way, that in such clauses where may also have the extended sense of at the place where:
I work on Broadway, where it intersects with Washington.
Where can also be used to head a
fused relative clause; and this is where it gets tricky. In this sort of clause the
wh- form does not stand for another entity but designates a ‘variable’ whose referent is not specified: in effect, the
wh- form is its own referent! A fused relative clause acts as an NP (nominal); for instance, it may be the subject or object of a verb:
Where I work is my office on Broadway.
I will tell him where I work, and he can meet me there.
And the clause—not where itself, but the entire clause it heads—may also act as the object of a preposition:
The bus stops three blocks from where I work.
That is what is involved in your three examples. As you will see from the paraphrases, they signify something quite different from what you intend:
- The bridge under where we live... This does not mean that you live under the bridge, but that the bridge is under the place where you live: apparently you live over the bridge! What you mean is The bridge under which we live ...
- The beach behind where I am standing... This does not mean that you are standing behind the beach, but that the beach is behind the place where you are standing: apparently you are standing in the water looking out to sea! What you mean is The beach behind which I am standing...
- The shop {next to/close to/before/opposite/in front of, etc} where we live... These are not all so absurd as the previous examples, because the spatial relationships are in most cases reciprocal: if the place where you live is ‘opposite’ the shop, the shop is also ‘opposite’ the place where you live. Still, before and in front of inverts the spatial relationship; and in all these cases, you are inverting your topic: instead of a bound relative clause describing where you live relative to the shop, you have a fused relative clause describing where the shop is, relative to where you live.
NOTE: It is true that in casual speech (and in writing which reflects casual speech) where often ends up with the sense of a pronoun; Man_From_India cites
Where's your favorite destination?
In speech, people often start sentences pointing in one direction, and then end them somewhere else. That’s ordinary and inevitable, because they’re assembling their thoughts on the fly. Hearers allow for that imprecision because they’re parsing the same way; and as long as the rough sense is clear nobody worries much about the syntactic details. Noncasual writing, however, demands strict precision, because there’s no opportunity for the writer and reader to clear up any ambiguity or misunderstanding which may arise. My answer above addresses the precise use of where in noncasual writing, which would require
What is your favorite destination?
∗ marks a usage as unacceptable
Best Answer
Where and when, either as interrogatives or as relatives, are not pronouns but pro-adverbs—they ‘stand for’ adverbials of place and time, respectively.
It is thus not strictly true to say that “a relative clause always contains a relative pronoun”—it may also be headed by a relative pro-adverb. And in some cases (as in He told me to stop, which I did) the relative ‘pronoun’ is actually a component of a relative pro-verbal construction with DO.